JP5801264B2 - Exhaust gas circulation thermal power plant operating method and exhaust gas circulation thermal power plant - Google Patents

Description

The present invention relates to an operation method of an exhaust gas circulation thermal power plant having a combustor that employs O ₂ stoichiometric combustion, and an exhaust gas circulation thermal power plant. More specifically, the present invention realizes an exhaust gas circulation thermal power plant by maintaining a constant concentration of nitrogen oxides contained in combustion exhaust gas from a combustor that employs O ₂ stoichiometric combustion. It is about the technology that makes it possible.

In a gasification power plant, exhaust gas discharged from a gas turbine is recovered by a heat recovery boiler, denitrated by a denitration facility, and then exhausted from a chimney. On the other hand, in a gasification power plant, a dry method may be employed for purification of gasification gas fuel in order to improve plant thermal efficiency and reduce costs by simplifying the plant configuration system. When this dry method is adopted, the nitrogen gas (mainly ammonia (NH ₃ )) is contained in the gasification gas fuel, and a large amount of fuel NOx is generated in the combustion process and discharged from the gasification power plant. Occupies most of NOx. Therefore, a technique for reducing fuel NOx is important.

In a conventional gasification power plant, a method for reducing fuel NOx by applying a reduction combustion method to a gas turbine combustor is employed (for example, Patent Document 1 and Patent Document 2). In this reduction combustion method, the amount of air supplied to the upstream portion of the combustor is reduced to a fuel rich condition, and nitrogen compounds in the gasified gas fuel are decomposed into N ₂ under a reducing atmosphere, and the combustor downstream side The remaining air is supplied to the engine so as to achieve complete combustion.

JP 2002-061517 A JP 2002-188457 A

  However, in gasification power plants that employ dry gas purification, even if fuel NOx is reduced by the reduction combustion method, the amount of NOx emissions will be greater than in plants that employ wet gas purification. There is a need to further reduce fuel NOx.

  It is an object of the present invention to provide a closed cycle thermal power plant operating method and a closed cycle thermal power plant that can further reduce the generation of fuel NOx even when dry gas purification is employed.

Formulas 1 and 2 show general reaction formulas of nitrogen compounds (NH ₃ ) and nitrogen oxides (NOx) in the denitration reaction used in the flue gas denitration apparatus of the thermal power plant. This decomposition reaction of nitrogen compounds by NO is a reaction that proceeds excellently in a very narrow temperature range called a temperature window. When the reaction temperature is high, the nitrogen compound (NH ₃ ) is oxidized to NO and the reaction temperature is low. And nitrogen compound and NO are discharged as they are without reacting. Therefore, the reaction is controlled by using a catalyst in the conventional denitration apparatus. As a result of intensive studies on the reduction of nitrogen oxide concentration in the exhaust gas of a closed cycle gas turbine power plant that employs O ₂ stoichiometric combustion, the present inventors have found that closed combustion employing O ₂ stoichiometric combustion is employed. In a cycle gas turbine power plant, exhaust gas recycled as a diluent contains CO ₂ and H ₂ O as main components and contains a small amount of O _2, so the decomposition reaction of nitrogen compounds by NO is relatively low. As well as knowing that it progresses, it was found that the temperature is included in the temperature distribution of the exhaust gas or gasified gas fuel of the closed cycle gas turbine power plant.

[Equation 1]
NH ₃ + NO + 1 / 4O ₂ → N ₂ + 3 / 2H ₂ O (1)
[Equation 2]
6NO ₂ + 8NH ₃ → 7N ₂ + 12H ₂ O (2)

Here, NOx is a general term for NO and NO ₂ , but most of NOx in the circulating exhaust gas of the power plant is NO, and decomposition of NH ₃ proceeds mainly by the general reaction formula (1) of Formula 1.

The present invention has been made on the basis of such knowledge, and the invention according to claim 1 is characterized in that the gasification gas generated in the gasification furnace is purified by a dry gas purifier and the amount of O ₂ as a fuel gas containing NH ₃ is obtained. In the operation method of a thermal power plant that burns with a combustor that performs stoichiometric combustion, before exhausting part or all of the exhaust gas discharged from the combustor and mixing it with the fuel gas as a diluent and combusting with the combustor Nitrogen oxide and O ₂ in the diluent are reacted with NH ₃ in the fuel gas to be decomposed into N ₂ and H ₂ O, and undecomposed NH ₃ is burned in the combustor and oxidized to nitrogen oxide. The operation is performed while maintaining the concentration of nitrogen oxides in the exhaust gas within a certain range by repeating the decomposition reaction and the oxidation reaction of NH ₃ .

When the diluent is mixed with the fuel gas, NH ₃ in the fuel gas reacts with nitrogen oxide NOx in the diluent and decomposes into N ₂ molecules mainly by the rightward reaction of the overall reaction (1). The reaction rate and reaction amount of the overall reaction (1) depend on the reaction temperature and reaction time. In particular, the reaction temperature is affected by the composition of the fuel gas and diluent (exhaust gas) and the reaction time. That is, in order for NH ₃ in the fuel gas and NO in the diluent to decompose into N ₂ , it is necessary to set the reaction temperature and reaction time according to the gas composition. There are few examples where is actively applied.

In the flow path (mixed gas flow path) through which the mixed gas of the fuel gas and the diluent flows, the overall reaction (1) proceeds and shows a decomposition rate corresponding to a predetermined reaction temperature and reaction time. Thereafter, the mixed gas is supplied to the combustor, and the residual NH _{3 that} has not been decomposed into N ₂ is oxidized to NO during the combustion process. The exhaust gas after combustion, for example, works in an expansion turbine, and then recycles part or all of it as a diluent to form a closed loop. The amount of ammonia produced in the gasifier due to the nitrogen content in the raw material is determined by the operating conditions of the raw material and the gasifier, and the mixed gas flow path decomposes ammonia in the gasification gas. Requires the presence of NO in the diluent. Therefore, the ammonia decomposition rate in the mixed gas passage need not be 100%, but is decomposed and adjusted to an appropriate value, and at the same time, the NO concentration in the exhaust gas is adjusted to a predetermined value. To establish. In addition, unlike the case where a high denitration rate is required for the denitration apparatus, control of the reaction temperature and reaction time is important, but the decomposition rate in the mixed gas channel is operated under relatively easy conditions.

In addition, there is a secondary effect that a small amount of oxygen in the diluent can be actively contributed to combustion in the combustor by mixing the diluent with the fuel gas. For example, a fuel gas (composition example: CO = 66%, H ₂ = 24%, CO ₂ , H ₂ O, N ₂ ) is burned stoichiometrically with O ₂ , and the combustion gas is diluted with exhaust gas to combustor When the outlet gas temperature is set to the 1300 ° C. level, the amount of dilution gas is about 3.7 times the sum of the fuel gas and the oxidant. If the concentration of the O ₂ component remaining in the diluent is 2%, this corresponds to 19% of the total amount of O ₂ supplied to the combustor. When the O ₂ component in the diluent is not actively contributed to combustion, the O ₂ concentration in the exhaust gas further increases. By providing a mixed gas flow path, the fuel gas and the diluent are mixed in advance and supplied to the combustor, so that the O ₂ component in the diluent can actively contribute to combustion. Also have.

ADVANTAGE OF THE INVENTION According to this invention, the NOx removal apparatus installed downstream of a gas turbine can be made unnecessary, or it can reduce significantly, the closed cycle gas turbine for gasification gas which comprises a closed loop is materialized, and simplification of a plant system It becomes possible to aim at the cost reduction by. In addition, the O ₂ component remaining in the diluent can be actively involved in gas turbine combustion, and there is an effect of reducing the O ₂ component concentration in the diluent.

The operation method of the exhaust gas circulation thermal power plant according to claim 2 is to adjust the concentration of nitrogen oxides in the exhaust gas by changing the decomposition rate of NH ₃ by increasing or decreasing the amount of the diluent mixed. is there.

  The overall reaction (1) is composed of a number of elementary reactions, and the reaction rate of each elementary reaction is determined by the gas composition concerned, its concentration and the reaction temperature. That is, the temperature window in which the rightward reaction of the general reaction (1) proceeds greatly depends on each elementary reaction and the related gas component concentration. In addition, the reaction path involving many elementary reactions varies depending on the composition of the fuel gas and the exhaust gas, and as a result, the optimum reaction temperature for forming a temperature window also varies. Considering the elementary reaction of the overall reaction (1), the non-catalytic denitration can be operated more efficiently by adjusting the amount of the diluent mixed with the fuel gas according to the composition of the fuel gas and the exhaust gas. It becomes possible.

According to a third aspect of the present invention, there is provided a method for operating an exhaust gas circulation thermal power plant that adjusts the concentration of nitrogen oxides in the exhaust gas by changing the decomposition rate of NH ₃ by increasing or decreasing the reaction time of the decomposition reaction. is there.

  In consideration of the elementary reaction of the overall reaction (1), the non-catalytic denitration can be operated more efficiently by adjusting the reaction time of the decomposition reaction according to the composition of the fuel gas and the exhaust gas.

According to a fourth aspect of the present invention, there is provided a method for operating an exhaust gas circulation thermal power plant in which the concentration of nitrogen oxides in the exhaust gas is adjusted by changing the decomposition rate of NH ₃ by increasing or decreasing the reaction temperature of the decomposition reaction. is there.

  The elementary reactions involved in the overall reaction (1) are affected by the composition of the fuel gas, the composition of the exhaust gas, and the reaction temperature, and the rightward reaction rate and amount of the overall reaction (1) change. That is, in order to appropriately control the overall reaction (1), it is important to set the mixed gas flow path to an appropriate reaction temperature according to the composition of the mixed gas and to provide a reaction time according to the reaction temperature. .

Here, for raising and lowering the reaction temperature, the heat of the high-temperature gasification gas in the gasification furnace or the heat of the high-temperature exhaust gas discharged from the gas turbine can be used. The decomposition of ammonia in the gasification gas and NO in the gas turbine combustion exhaust gas into N ₂ requires controlling the reaction temperature to a narrow operating temperature called a “temperature window”. According to this, by recovering the heat of each part of the gasification power plant and controlling the reaction temperature of the decomposition reaction of NH ₃ to an arbitrary value, the decomposition reaction of NH ₃ is appropriately controlled, and an external heat source It is possible to prevent the thermal efficiency of the power plant from being unnecessarily lowered without using the power.

Here, the fuel reforming part (the flow path through which the decomposition reaction of NH _{3 in} the fuel gas proceeds while the diluent is mixed with the fuel gas) is connected to, for example, the upstream part in the combustor or the outer cylinder of the combustor. It can be provided between the cylinders in the combustor wall surface cooling section or the combustor tail cylinder. According to this, by providing the fuel reforming part in each part of the combustor, the heat source accompanying the fuel reforming (decomposition of NH _{3 in} the fuel gas) can be easily obtained, and at the same time, the combustor part is also cooled. There are advantages you can do. In particular, by providing a fuel reformer around the combustor in the gas turbine casing, it is possible to introduce the reformed gasification gas into the combustor without collecting it, and the power plant is inadvertently complicated. Don't make it.

  Further, it is possible to provide the fuel reforming section inside the turbine blade. According to this, by providing the fuel reforming section in the gas turbine blade section, it is possible to easily obtain the heat source of the predetermined reaction heat required for fuel reforming, and at the same time, by performing the turbine blade cooling, the turbine blade There is also a synergistic effect that eliminates the need for a high-pressure medium for cooling, reduces the power of the compressor of the power plant, and improves plant thermal efficiency. In addition, when a reburning gas turbine is employed, a reforming gasification gas can be introduced into the reburning gas turbine combustor without recovering the reformed gasification gas by providing a fuel reforming unit in the cooling unit of the first stage stationary vane. This also has the advantage of simplifying the configuration of the gas turbine.

Further, in the operation method of the exhaust gas circulation type thermal power plant according to claim 5, a part or all of the oxidant supplied to the combustor is mixed with the fuel gas, and the decomposition rate of NH ₃ is changed to change in the exhaust gas. This adjusts the concentration of nitrogen oxides.

By supplying the oxidizing gas supplied to the combustor to the fuel gas, the O ₂ component concentration of the mixed gas increases, and the overall reaction (1) can be promoted at a lower reaction temperature. This makes it possible to safely decompose ammonia in the fuel gas and NO in the exhaust gas into N ₂ without increasing the reaction temperature of the mixed gas flow path. Further, the fuel gas is premixed with an oxidant and a diluent and supplied to the combustor to facilitate mixing, and fuel gas / O ₂ stoichiometric combustion in the combustor can be promoted. It is possible to reduce the concentration of the O ₂ component remaining therein, the CO or H ₂ component that is an unburned component, and improve the combustion efficiency.

  Moreover, you may make it perform rated operation after said adjustment like the operation method of the exhaust gas circulation type thermal power plant of Claim 6, and the operation method of the exhaust gas circulation type thermal power plant of Claim 7 As described above, the nitrogen oxide concentration in the exhaust gas is measured while performing the rated operation, and the rated operation may be performed while performing the above adjustment so that the measured value becomes a predetermined target value. .

Further, according to the operation method of the exhaust gas circulation thermal power plant according to claim 8, the temperature of the mixed gas in which the diluent is mixed with the fuel gas is set to 300 to 600 ° C. to promote the decomposition reaction of NH ₃ , and then the combustion It supplies to the vessel.

Furthermore, the invention described in claim 9 is a thermal power generation system in which a gasification gas generated in a gasification furnace is purified by a dry gas purification device and burned in a combustor that performs O ₂ stoichiometric combustion as a fuel gas containing NH _3. In the plant, a recycling system that recycles part or all of the exhaust gas discharged from the combustor and mixes it with the fuel gas as a diluent, and the fuel gas mixed with the diluent dilutes NH ₃ in the fuel gas. has a nitrogen oxides and the mixed gas flow channel for conveying while decomposed into N ₂ and H _{2 O} by O ₂ in the dosage, the combustor, the NH ₃ remaining in the fuel gas is burned nitrogen It is oxidized to oxide, and by mixing diluent with fuel gas by a recycle system, NH ₃ decomposition and oxidation reaction are repeated, so that the concentration of nitrogen oxide in exhaust gas is within a certain range. Maintenance It is intended to be.

  The exhaust gas circulation thermal power plant according to claim 10 is provided with a plurality of supply positions for supplying the diluent to the fuel gas and switching means for switching the supply position to be used.

  An exhaust gas circulation thermal power plant according to an eleventh aspect includes first flow rate adjusting means for increasing or decreasing the amount of diluent supplied.

  An exhaust gas circulation thermal power plant according to claim 12 is provided with a bypass passage for mixing a part or all of the oxidant supplied to the combustor with the fuel gas, and a supply amount of the oxidant mixed with the fuel gas. A second flow rate adjusting means for increasing / decreasing is provided.

Furthermore, in the exhaust gas circulation thermal power plant according to claim 13, the mixed gas flow path has a portion for setting the temperature of the mixed gas to 300 to 600 ° C. Therefore, the temperature of the mixed gas can be set to 300 to 600 ° C. to promote the NH ₃ decomposition reaction.

In the present invention, exhaust gas is supplied to the fuel gas as a diluent, so that NH ₃ in the fuel gas is decomposed and nitrogen oxides used for the decomposition (generation of nitrogen oxides in the exhaust gas) are produced. Since they can be balanced, the exhaust gas can be circulated to be mixed with the fuel gas, and a closed cycle exhaust gas circulation thermal power plant can be established.

Further, since fuel gas containing NH ₃ can be used, dry gas purification of fuel gas can be adopted, and plant thermal efficiency can be increased as compared with the case where wet gas purification is adopted.

Further, the gasified fuel is mixed with a circulating gas (diluent) obtained by recycling the exhaust gas, and NH ₃ in the gasified fuel and nitrogen oxides in the exhaust gas are reacted in a non-catalytic manner to undergo gas phase decomposition into N _2. Therefore, even when dry gas purification is employed, the generation of fuel NOx can be further reduced.

Moreover, since NH ₃ in the fuel gas is decomposed using nitrogen oxides in the exhaust gas, it is not necessary to provide a separate supply source of nitrogen oxides.

It is a schematic block diagram which shows 1st Embodiment of the exhaust gas circulation type thermal power plant to which this invention is applied. NH ₃ and the influence of reaction temperature on the formation degradation properties of NO (D / F ratio = 3, reaction time 10s) is a graph showing a. It is a schematic block diagram which shows 2nd Embodiment of the exhaust gas circulation type thermal power plant to which this invention is applied. NH ₃ and NO dilution effect ratio D / F on the degradation properties (reaction temperature 400 ° C., reaction time 10s) is a graph showing a. It is a schematic block diagram which shows 3rd Embodiment of the exhaust gas circulation type thermal power plant to which this invention is applied. It is a schematic block diagram which shows 4th Embodiment of the exhaust gas circulation type thermal power plant to which this invention is applied. It is a schematic block diagram which shows 5th Embodiment of the exhaust-gas circulation type thermal power plant to which this invention is applied. The influence of O ₂ concentration on the relationship between reaction temperature and NH ₃ and NO decomposition characteristics is shown, (a) is a decomposition characteristic diagram of NH ₃ , (b) is a decomposition characteristic diagram of NO, (c) is a total fuel N component it is an exploded characteristic diagram of (NH ₃ and NO). It is a schematic block diagram which shows 6th Embodiment of the exhaust gas circulation type thermal power plant to which this invention is applied. It is a schematic block diagram which shows 7th Embodiment of the exhaust gas circulation type thermal power plant to which this invention is applied, and shows the vicinity of the fuel reforming part. It is a schematic block diagram which shows 8th Embodiment of the exhaust-gas circulation type thermal power plant to which this invention is applied, and shows the vicinity of the fuel reforming part. It is a schematic block diagram which shows 9th Embodiment of the exhaust gas circulation type thermal power plant to which this invention is applied, and shows the vicinity of the fuel reforming part. It is a schematic block diagram which shows 10th Embodiment of the exhaust gas circulation type thermal power plant to which this invention is applied. It is a flowchart which shows the operating method of the exhaust gas circulation type thermal power plant of FIG. FIG. 6 is a schematic configuration diagram showing a main part of a modification of the first flow rate adjusting means 23. Is a schematic diagram of a model of a CO ₂ recovering high efficiency IGCC and closed cycle gas turbine power generation system used in analysis to confirm the effect of the present invention. It is a graph which shows the influence of exhaust gas circulation on a fuel NOx exhaust characteristic. NH applied to O ₂ stoichiometric combustion closed cycle gas turbine ₃ is a diagram showing an example of an operation overview of the cracking system. It is a graph which shows the verification result of this analysis method in non-catalytic denitration conditions. It is a graph which shows the effect of the non-catalytic decomposition method on the fuel NOx exhaust characteristic. NH ₃ and the influence of reaction temperature on the time course of NO (D / F ratio = 3) is a graph showing a. H ₂ component generating decomposition characteristics of (the initial value of the H ₂ component concentration in the mixed gas as the reference (100%)) is a graph showing a. The influence of reaction time on NH ₃ and NO decomposition characteristics is shown, (a) is the decomposition characteristic diagram of NH ₃ , (b) is the decomposition characteristic diagram of NO, (c) is the total fuel N content (NH ₃ and NO) FIG. The influence of the dilution ratio D / F on the relationship between the reaction temperature and NH ₃ and NO decomposition characteristics is shown. (A) is a decomposition characteristic diagram of NH ₃ , (b) is a decomposition characteristic diagram of NO, and (c) is a total fuel. it is an exploded characteristic diagram of N min (NH ₃ and NO). NH ₃ and the effect of _{O 2} concentration on the NO decomposition properties (reaction temperature 400 ° C., reaction time 10s) is a graph showing a. NH ₃ and the effect of NO on the decomposition ratio NO / NH ₃ molar ratio (reaction temperature 400 ° C., reaction time 10s) is a graph showing a. Is a graph showing the effect of the proportion of fuel in the CO / _{H 2} concentration on the NH ₃ and NO decomposition ratio. The influence of the ratio of CO / H ₂ concentration in fuel on the relationship between reaction temperature and NH ₃ and NO decomposition characteristics is shown, (a) is a decomposition characteristic diagram of NH ₃ , (b) is a decomposition characteristic diagram of NO, (c ) Is a decomposition characteristic diagram of all fuel N components (NH ₃ and NO). NH ₃ and the effect of the fuel in the NH ₃ concentration on the NO decomposition ratio (reaction temperature 400 ° C., reaction time 10s) is a graph showing a. The influence of the NH ₃ concentration in the fuel on the relationship between the reaction temperature and the NH ₃ and NO decomposition characteristics is shown. (A) is a decomposition characteristic diagram of NH ₃ , (b) is a decomposition characteristic diagram of NO, and (c) is the total fuel. it is an exploded characteristic diagram of N min (NH ₃ and NO). Is a graph showing the effect of pressure on the NH ₃ and NO decomposition ratio.

Hereinafter, the configuration of the present invention will be described in detail based on the form shown in the drawings. Here, not the closed cycle gas turbine power plant having a gas turbine combustor as the combustion apparatus which performs the O ₂ stoichiometric combustion will be described as an example but is not limited thereto, a combustor for performing O ₂ stoichiometric combustion And an exhaust gas circulation type thermal power plant that circulates part or all of the exhaust gas discharged from the combustor into fuel gas by a recycle system is applicable.

A first embodiment of the present invention will be described. In the present embodiment, a gasification gas fuel reforming combined power plant will be described as an example of an exhaust gas circulation thermal power plant. FIG. 1 is a schematic diagram showing the configuration of a gasification gas fuel reforming combined power plant. As shown in FIG. 1, the plant system applied in the present embodiment is a system for gasifying raw coal or the like with air or an oxidant mainly composed of oxygen separated and generated from air, and purifies the gasified gas. Gas purification system, gasified gas fuel (fuel gas) is burned stoichiometrically with an oxidizer mainly composed of O ₂ , the gas turbine is driven, and power is generated by a generator coupled to the gas turbine. It consists of a system that uses the heat of the high-temperature exhaust gas from the turbine to generate electricity through a steam cycle. In particular, the gasification furnace employs a gasifying agent in which CO ₂ is added to O ₂ , and the gas turbine employs a closed cycle in which high-temperature combustion gas is diluted with gas turbine exhaust gas, thereby reducing the CO ₂ of the power plant. A technology for reducing emissions or reducing CO ₂ recovery power is adopted.

  Examples of the gasification raw material C include, but are not limited to, coal, petroleum, biomass, waste, and the like. Examples of the gasifying agent AO2 include, but are not limited to, oxygen, air, oxygen-enriched air, and the like.

Here, the apparatus configuration will be described below in the case of a coal gasification plant using oxygen as an oxidizing agent. This plant includes an oxygen production apparatus 1, a gasification furnace 2, a gas purification apparatus 3, a fuel reformer, a gas turbine combustor 5 as a combustor that performs O ₂ stoichiometric combustion, a gas turbine 6, and an exhaust heat recovery boiler. 7, an exhaust gas compressor 8, a generator 9, a steam turbine 10, and the like.

The fuel reforming portion is a region in which the decomposition reaction of NH ₃ mainly proceeds in the mixed gas of the fuel gas and the diluent, and is a portion downstream of the diluent supply position 4 in the fuel gas flow path. And, it is the upstream side portion of the mixed gas flow path 22. The fuel reforming unit may use the supply path as it is, or may be a special device that promotes the mixing of the fuel gas and the diluent.

In the present embodiment, at least the fuel reforming section of the mixed gas flow path 22 is at a temperature at which the temperature of the mixed gas can be 300 to 600 ° C. By making the temperature of the mixed gas 300 to 600 ° C., the decomposition reaction of NH ₃ in the fuel gas can be promoted.

  The oxidant AO2 necessary for the gasification furnace 2 is generated by the oxygen production apparatus 1. In the oxygen production apparatus 1, oxygen AO 2 is separated from high-pressure air supplied by a compressor (not shown) and supplied to the gasification furnace 2 and the gas turbine combustor 5. In the gasification furnace 2, by supplying oxygen AO2, the coal C is oxidized with oxygen to generate gasified gas fuel CG1, degassed and desulfurized by the gas purification device 3 to be gasified gas fuel CG2, and further supplied position 4 The gasified gas fuel CG3 to be supplied to the gas turbine combustor 5 is generated by decomposing and removing the nitrogen compounds in the gasified gas fuel CG2 in the mixed gas flow path 22 downstream of the gas. When the load of the gasification furnace 2 rises and gasification gas fuel CG3 of a certain quality or higher is produced, it is supplied to the gas turbine combustor 5. In the gas turbine 6, the operation is started by switching the gasified gas fuel CG3 to the starting fuel, the plant load is increased, and the operation is mainly performed under rated conditions.

  In addition, when especially distinguishing about fuel gas, what was produced | generated by the gasification furnace 2 is called gasification gas fuel CG1, and what was further refine | purified by the gas purification apparatus 3 is called gasification gas fuel CG2. Further, a mixture of diluent is referred to as mixed gas or gasified gas fuel CG3. Further, when particularly distinguishing the exhaust gas discharged from the combustor 5, the gas immediately after being discharged from the combustor 5 is called a gas turbine combustion exhaust gas FG, and the gas passed through the gas turbine 6 is a gas turbine. It is called exhaust gas G.

The high-temperature gas turbine exhaust gas G of the gas turbine 6 delivers heat to the feed water FW by the exhaust heat recovery boiler 7, guides the generated steam ST to the steam turbine 10, drives it, and generates the generator 9 To generate electricity. The steam ST recovered by the steam turbine 10 is ascited to the feed water FW by the condenser 11 and then supplied to the exhaust heat recovery boiler 7. On the other hand, when a part or all of the exhaust gas that has passed through the exhaust heat recovery boiler 7 is recycled as a diluent, and a part of the exhaust gas is recycled as a diluent, the remaining exhaust gas is converted into a CO ₂ recovery device. After CO ₂ is recovered by the exhaust gas 12, the exhaust gas is exhausted from the chimney 13. In FIG. 1, the symbol CD represents CO ₂ recovered from the gas turbine exhaust gas.

The exhaust gas circulation thermal power plant includes a recycle system 21 that recycles a part or all of exhaust gas discharged from the gas turbine combustor 5 and mixes it with fuel gas as a diluent, and a fuel gas mixed with a diluent. A mixed gas flow path 22 for conveying (mixed gas) while decomposing NH ₃ in the fuel gas into N ₂ and H ₂ O by nitrogen oxide and O ₂ in the diluent, and a combustor 5. Is a method in which NH ₃ remaining in the fuel gas is burned and oxidized into nitrogen oxides, and by mixing a diluent with the fuel gas by the recycle system 21, the decomposition reaction and the oxidation reaction of NH ₃ are performed. Repeatedly, the concentration of nitrogen oxides in the exhaust gas is maintained within a certain range.

  The diluent supply position 4 may be provided between the gas purification device 3 and the gas turbine combustor 5, or may be provided between the gasification furnace 2 and the gas purification device 3. That is, a diluent may be mixed with the gasified gas fuel CG2 after purification by the gas purification apparatus 3, or a diluent may be mixed with the gasified gas fuel CG1 before purification. The mixed gas flow path 22 is a portion of the flow path for supplying the fuel gas to the combustor 5 where the fuel gas mixed with the diluent, that is, the mixed gas flows, and in the former case, the gas purification device 3 and the combustor 5. The upstream end of the mixed gas flow path 22 is located between the gasification furnace 2 and the gas purification device 3 in the latter case.

In the mixed gas flow path 22, the entire amount of the gasified gas fuel CG 2 supplied to the gas turbine 6 is supplied to the fuel reforming unit together with a small amount of nitrogen oxide and a small amount of oxygen in the gas turbine combustion exhaust gas FG (diluent). By using the heat in an appropriate temperature region in the gasification furnace 2, the nitrogen compound in the gasification gas fuel CG2 and the nitrogen oxide in the gas turbine combustion exhaust gas FG supplied to the fuel reforming section are obtained. Decomposes into nitrogen molecules (N ₂ ) in the presence of O ₂ .

The operation method of the exhaust gas circulation type thermal power plant is that a part or all of the exhaust gas discharged from the gas turbine combustor 5 is recycled and mixed with the fuel gas as a diluent, and diluted before being combusted in the combustor 5. Nitrogen oxides in the agent and O ₂ react with nitrogen compounds in the fuel gas to be decomposed into N ₂ and H ₂ O, and undecomposed nitrogen compounds are burned in the combustor 5 to be oxidized into nitrogen oxides. The operation is performed while maintaining the concentration of nitrogen oxide in the exhaust gas within a certain range by repeating the decomposition reaction and oxidation reaction of the nitrogen compound.

  Adjustment for maintaining the nitrogen oxides in the exhaust gas within a certain range may be performed in advance before the rated operation of the plant (preliminary adjustment), or may be performed at any time during the rated operation ( Feedback control). In this embodiment, prior adjustment is performed, and rated operation is performed after adjustment. Here, the pre-adjustment before the rated operation may be performed during the start-up operation of the plant, or the gasification raw material C used at the time of plant design is determined and adjusted according to the gasification raw material C. There may be.

Adjustment for maintaining the nitrogen oxide in the exhaust gas constant is performed by adjusting the concentration of the nitrogen oxide in the exhaust gas. As such adjustment, by raising and lowering the temperature of the decomposition reaction (the temperature of the mixed gas) in which the nitrogen oxides in the diluent and O ₂ are reacted with the nitrogen compounds in the fuel gas and decomposed into N ₂ and H ₂ O. By changing the decomposition rate of nitrogen compounds (temperature adjustment method), the time of decomposition reaction (time for decomposition reaction, in other words, the time to combust in the combustor 5), the decomposition rate of nitrogen compounds is reduced. Method of changing (time adjustment method), method of changing the decomposition rate of nitrogen compounds by increasing / decreasing the mixing amount of the diluent (mixing amount adjustment method), part or all of the oxidant supplied to the combustor 5 as fuel gas There is a method of changing the decomposition rate of nitrogen compounds by mixing and changing the amount of oxygen (oxygen amount adjusting method). These methods may be performed alone or in combination of some or all of them. In the case where there is only one diluent supply position 4 as in this embodiment and no second flow rate adjusting means for increasing or decreasing the supply amount of the oxidant to be mixed with the fuel gas is provided, the starting operation is performed. Only the mixing amount adjustment method can be used for adjustment while performing.

  FIG. 2 shows the result of examination of the decomposition of ammonia in the gasified gas fuel CG2 and NO in the gas turbine exhaust gas G by numerical analysis based on reaction kinetics in the mixed gas flow path 22.

For the numerical analysis, the elementary reaction scheme proposed by Millar and Bowman was used (literature name: Miller, JA, and Bowman, CT, 1989, “Mechanism and modeling of nitrogen chemistry in combustion,” Prog. Energy Combust. Sci. , Vol.15, pp.287-338.). The elementary reaction scheme of this document consists of 248 elementary reactions, and the chemical species considered are 51 components. Although various elementary reaction schemes have been proposed, the inventors of the present application have confirmed that in the reaction analysis of NH ₃ and NO in the gasification gas, the results agree with the experimental results under certain conditions ( Literature name: Hasegawa, T. et al., “Study of Ammonia Removal from Coal Gasified Fuel,” Combustion and Flame, Vol. 114, pp.246-258, 1998.).

  For thermodynamic data, JANAF thermodynamic property values were used, and unknown physical property values were derived from the relationship between Gibbs standard formation energy and chemical equilibrium constants. That is, 51 differential equations for obtaining the concentration of each chemical species with respect to the reaction time can be created from a chemical reaction system including 51 chemical species. The concentration of each chemical species after an arbitrary reaction time was determined by solving the nonlinear differential equation system of equation 51 using the Gear method. Also, in the reaction process, all chemical species are assumed to be uniformly mixed, diffusion and mixing processes are not considered, and the reaction proceeds at a constant temperature. The numerical solution method is not limited to the Gear method, and other numerical solution methods such as the Runge-Kutta method may be used.

Table 1 (Rated conditions for gas turbine combustors for CO ₂ recovery type high efficiency IGCC system) shows the state quantities of various fluids under the rated conditions of closed-cycle gas turbine combustors, combustor pressure, combustor outlet gas temperature, etc. Show. The reaction time is set to 10 s. The numerical analysis was carried out in the reaction temperature range of 200 ° C to 1200 ° C for the gas mixture of gasified gas fuel shown in Table 1 and a part of the diluent (gas turbine exhaust gas G three times the gasified gas). did. The NH ₃ and NO concentrations after mixing the gasified gas fuel and diluent were each 125 ppmv. The analysis here is for a 416 MW class CO ₂ recovery type coal gasification combined power plant with a power generation end output. However, the plant output or the like does not affect the analysis of NH ₃ decomposition itself.

As shown in the analysis results in FIG. 2, by setting the reaction temperature to 300 ° C. or higher, the NH ₃ in the gasification gas and the NO in the gas turbine combustion exhaust gas can be partially or totally decomposed into N _2. Became clear.

By setting the reaction temperature at 400 to 480 ° C., NH ₃ and overall decomposition rate of NO to (DeTFN) it can be 50% or more.

If “DeTFN ≧ 40%” is used as a reference, the reaction temperature is 350 to 550 ° C. In this case, assuming that NH ₃ in the gasified gas fuel is 1 mol under the rated conditions of the gas turbine, NOx in the exhaust gas is 1 mol or less. This corresponds to a denitration rate of about 80% when a denitration apparatus is installed. Since the thermal power plant operates at a denitration rate of 80 to 95%, a denitration device can be dispensed with.

On the other hand, if the reaction temperature is set to a high temperature of 600 to 1000 ° C., it is possible to decompose 90% or more of NH ₃ into N ₂ , but on the other hand, the decomposition rate of NO decreases and DeTFN also decreases. Recognize.

  From the above, the temperature of the mixed gas is preferably 300 to 600 ° C., more preferably 350 to 550 ° C., and even more preferably 400 to 480 ° C. Before reaching the combustor 5, the mixed gas is maintained at the above temperature and maintained for the time required for the reaction at that temperature.

  Further, as a fuel reforming method, the supply position 4 is installed on the upstream side of the gas refining device 3, or is installed before and after the exhaust heat recovery boiler 7 in order to use the heat of the gas turbine exhaust gas G (pipe). It is also conceivable that the mixed gas flow path 22 is installed in the exhaust heat recovery boiler 7 or the flue, or a heat exchanger is installed and heated). In the former case, by performing fuel reforming before gas purification, fuel reforming can be performed at a higher reaction temperature, and heating for obtaining reaction heat of fuel reforming is not required.

In the mixed gas flow path 22, a total reaction of all or part of the nitrogen compound (hereinafter described as NH ₃ ) in the fuel gas and the nitrogen oxide (hereinafter described as NO) in the gas turbine combustion exhaust gas FG is performed. As shown in Formula (1), it decomposes into N ₂ . The reformed gasified gas fuel CG3 is supplied to the gas turbine combustor 5 together with the oxidizing agent AO2 mainly composed of oxygen, burned stoichiometrically, the gas turbine 6 is driven, and the generator 9 generates electric power. By decomposing ammonia (NH ₃ ) in the gasified gas fuel and NO in the gas turbine exhaust gas into N ₂ , the amount of NOx generated in the gas turbine exhaust gas G is adjusted, and the NOx discharged from the plant is greatly increased. Can be reduced.

In the present embodiment, the stoichiometric combustion of the gasified gas fuel CG3 by O ₂ has a high combustion temperature, so the gas turbine exhaust gas G is also supplied to the gas turbine combustor 5 to bring the combustion temperature to a predetermined temperature. It has been reduced to.

The concentration of nitrogen oxides in the exhaust gas automatically converges to a value in an appropriate range based on the relationship between the decomposition rate of NH ₃ and the molar amount of nitrogen oxides circulated.

In this way, by adjusting the amount of NOx produced in the gas turbine exhaust gas G, a closed cycle gas turbine that circulates most of the gas turbine exhaust gas G can be employed in the gasification power plant, and CO ₂ separation is achieved. - not highly dependent on the recovery technique, and it is possible to reduce the CO ₂ emissions from power plants without damaging the thermal efficiency of the plant.

Further, in the gas turbine combustor 5, the gas turbine exhaust gas G as a diluent is mixed in advance with the fuel gas and supplied to the gas turbine combustor 5, so that O ₂ in the diluent is actively used for gas turbine combustion. The synergistic effect of reducing the O ₂ concentration remaining in the gas turbine exhaust gas G and facilitating the use of the gas turbine exhaust gas G for coal transportation or the like can be obtained.

  Next, a second embodiment of the present invention will be described. In addition, the same code | symbol is attached | subjected about the same member and component as the above-mentioned power plant, and those detailed description is abbreviate | omitted. In the present embodiment, a gas turbine fuel reforming power generation gas turbine plant will be described as an example of an exhaust gas circulation thermal power plant. FIG. 3 is a schematic diagram showing a configuration of a gasification gas fuel reforming type power generation gas turbine plant. In this plant, the nitrogen oxide concentration in the exhaust gas is measured while performing the rated operation, and the rated operation is performed while adjusting so that the measured value becomes a predetermined target value. That is, feedback control is performed so that the concentration of nitrogen oxides in the exhaust gas is maintained within a certain range. In this embodiment, the NO concentration in the gas turbine exhaust gas G is monitored by the analyzer 15, and the supply of the gas turbine combustion exhaust gas HG2 supplied to the supply position 4 so that the NO concentration is balanced within a certain range. It is characterized by adjusting the amount. Note that the concentration of nitrogen oxides in the exhaust gas usually changes in an increasing direction unless controlled, and can be maintained within a certain range by controlling it to be below a certain value (others) The same applies to the above embodiment).

  The supply amount of the gas turbine combustion exhaust gas HG2 supplied as the diluent to the supply position 4 is adjusted by, for example, the opening degree of the flow rate adjustment valve. That is, a flow rate adjusting valve is provided as the first flow rate adjusting means 23 for increasing or decreasing the supply amount of the diluent.

  In the case of particularly distinguishing the diluent, the one after being compressed by the exhaust gas compressor 8 is referred to as exhaust gas HG, and the one supplied to the combustor 5 is referred to as gas turbine combustion exhaust gas HG1. Further, what is supplied to the supply position 4 is called gas turbine combustion exhaust gas HG2, and what is supplied to the gasification furnace 2 is called gas turbine combustion exhaust gas HG3.

FIG. 4 shows the reaction kinetics about the influence of the dilution amount on the decomposition of NH ₃ in the gasified gas fuel CG 2 and NO in the gas turbine exhaust gas G in the mixed gas flow path 22 as in FIG. It is the result examined by numerical analysis based on it. The composition of the gasified gas fuel and the diluent is constant as shown in Table 1, the reaction temperature is constant at 400 ° C., and the amount of gas turbine exhaust gas supplied to the supply position 4 is changed to change ammonia (NH ₃ ) and NO. The decomposition rate of is examined. The horizontal axis shows the ratio of dilution amount (gas turbine exhaust gas supply amount) / gasification gas fuel supply amount (dilution ratio). In the analysis, the concentration of NH ₃ in the gasified gas fuel is constant at 500 ppmv, and the supplied NO concentration is adjusted to be equimolar with NH ₃ . From the analysis results shown in FIG. 4, at the reaction temperature, the NH ₃ decomposition rate (DeNH ₃ ) increases as the dilution ratio increases, and the NO decomposition rate (DeNO) shows the maximum value at the dilution ratio = 3 to 4. It can be seen that the decomposition rate (DeTFN) of NH ₃ and NO as a whole tends to increase gradually. FIG. 4 shows an example of numerical analysis of the mutual decomposition reaction of NH ₃ and NO. The optimum value of the gas turbine exhaust gas supply amount is also affected by the composition of the gasification gas and the gas turbine exhaust gas, and the reaction temperature.

The general reaction formula (1) is a general reaction in which equimolar NH ₃ and NO react to decompose into N ₂ . Most of NH ₃ in the fuel gas is oxidized to NO during the combustion process. Therefore, the total of NH ₃ and NO remaining without being decomposed in the mixed gas flow path 22 becomes the NOx concentration in the gas turbine exhaust gas. In the closed cycle gas turbine, which is the main object of the present invention, most of the gas turbine exhaust gas G is circulated as a working medium, so that if no measures are taken, the NOx concentration in the gas turbine exhaust gas G will increase until it is saturated. Therefore, there is a concern that the realization of the closed-cycle gas turbine and the operation of the downstream power plant component equipment may be hindered. Therefore, the NO concentration in the gas turbine exhaust gas G is monitored, and the supply amount of the gas turbine exhaust gas G is adjusted so that the NO concentration in the gas turbine exhaust gas G becomes a value within a certain range. It is possible to appropriately control the mutual decomposition reaction of NH ₃ in gas and NO in gas turbine exhaust gas G (diluent) to be supplied into N ₂ .

In addition, decomposition of NH ₃ is considered to be caused not only by the general reaction formula (1) but also by the general reaction formula (2), and is a reaction phenomenon involving many elementary reactions. For this reason, there is a possibility that the control of the equimolar reaction of NH ₃ and NO may be inappropriate. In such a case, the optimum reaction conditions regarding the operation data of the system and the NH ₃ decomposition condition data by numerical analysis, specifically, the fuel composition, the exhaust gas composition, and the decomposition conditions of NH ₃ and NO corresponding to each composition By creating a database by collecting data on (reaction temperature, reaction time), the influence of the exhaust gas mixture amount on the optimal reaction conditions, etc., the NO concentration in the gas turbine exhaust gas G is maintained within a certain range. Thus, by adjusting the supply amount of the gas turbine exhaust gas G to the supply position 4, NOx generation in the closed cycle gas turbine can be suppressed to a predetermined concentration or less. As a result, the amount of NOx discharged to the outside can be reduced, so that the capacity of the denitration facility can be reduced, or a power plant that does not require installation can be realized, and the initial cost and operation cost of the plant can be reduced. it can.

  In the above description, the flow rate adjusting valve that directly adjusts the flow rate of the diluent to the supply position 4 is provided as the first flow rate adjusting means 23. However, the present invention is not limited to this, and the dilution to the supply position 4 is performed. Any agent that can increase or decrease the supply amount of the agent can be used. For example, as shown in FIG. 15, by supplying a valve as the first flow rate adjusting means 23 at the branch point of the recycle system 21 and changing the inflow ratio to the recycle system 21, the diluent is supplied to the supply position 4. The amount may be adjusted.

  Next, a third embodiment of the present invention will be described. In addition, the same code | symbol is attached | subjected about the same member and component as the above-mentioned power plant, and those detailed description is abbreviate | omitted. In the present embodiment, a gas turbine fuel reforming power generation gas turbine plant will be described as an example of an exhaust gas circulation thermal power plant. FIG. 5 is a schematic diagram showing the configuration of a gasification gas fuel reforming type power generation gas turbine plant. This plant is provided with a plurality of supply positions 4 for the fuel gas of the diluent, and switching means 24 for switching the supply positions 4 to be used.

  In the present embodiment, a switching valve for switching the flow path leading to each supply position 4 is provided as the switching means 24.

  Each supply position 4 has a different distance to the gas turbine combustor 5. That is, the length of the mixed gas passage 22 is different for each supply position 4. Therefore, the time required to flow from each supply position 4 to the gas turbine combustor 5 is different, and the time for the decomposition reaction can be changed. In the present embodiment, the supply position 4 is, for example, in the vicinity of the outlet of the gasification furnace 2, in the vicinity of the inlet of the gas purification device 3, in the gas purification device 3, in the vicinity of the outlet of the gas purification device 3, and in the gas purification device 3 and gas turbine combustion Near the intermediate position between the gas purifier 5 and at a position closer to the gas turbine combustor 5 than an intermediate position between the gas purifier 3 and the gas turbine combustor 5.

By providing a plurality of supply positions 4 and switching the supply position 4 to be used, i.e., the supply position 4 for supplying the diluent, by the switching means 24, the time until the mixed gas reaches the gas turbine combustor 5 can be changed. Therefore, the time during which the decomposition reaction of the general reaction formula (1) is performed in the mixed gas flow can be changed (time adjustment method). By adjusting the reaction time, decomposition of NH ₃ in the fuel gas and NO in the exhaust gas into N ₂ can be adjusted.

The installation position of the supply position 4 can be installed in a region from the upstream gasification furnace 2 to the combustor 5. In particular, the mutual decomposition reaction of NH ₃ and NO described in the general reaction formula (1) is promoted by appropriately setting the reaction time and the reaction temperature. In particular, when a catalyst or the like is not used, the gas turbine combustion exhaust gas G (diluent) is supplied to any position from the gasifier 2 to the combustor 5 to decompose NH ₃ and NO into N _2. Is possible. This is because the NH ₃ , NO concentration, and O ₂ concentration in the mixed gas of the fuel gas and the diluent are small and hardly affect the oxidation reaction of the fuel. Accordingly, the supply position 4 is provided with a supply nozzle so as to disperse and mix the diluent in the fuel gas, and the mixed reaction gas (mixed gas) proceeds downstream, and the overall reaction formula ( Decomposition of NH ₃ and NO into N ₂ proceeds as described in 1). In particular, when an appropriate reaction temperature called a reaction temperature window is relatively low, the reaction time required for the mutual decomposition reaction becomes long. For this reason, the generation time of NO in the gas turbine exhaust gas is controlled by selecting the exhaust gas supply position 4 and adjusting the reaction time, and controlling the plant so that the NO concentration in the exhaust gas is maintained within a certain range. The increase in the pressure is suppressed and a closed cycle gas turbine is realized.

  Next, a fourth embodiment of the present invention will be described. In addition, the same code | symbol is attached | subjected about the same member and component as the above-mentioned power plant, and those detailed description is abbreviate | omitted. In the present embodiment, a gas turbine fuel reforming power generation gas turbine plant will be described as an example of an exhaust gas circulation thermal power plant. FIG. 6 is a schematic diagram showing the configuration of a gasification gas fuel reforming power generation gas turbine plant. In this plant, the NO concentration and other compositions in the gas turbine combustion exhaust gas are measured and monitored by the analyzer 15, and the supply position 4 to be used is adjusted so that the NO concentration in the combustion gas is maintained within a certain range. That is, the supply position 4 to be used is selected. In addition, description of the waste heat recovery boiler 7 grade | etc., Is abbreviate | omitted in FIG.

By switching the supply position 4 to be used by the switching means 24, the reaction time which is one of the most important items of the decomposition reaction condition of NH ₃ and NO into N ₂ is optimized, and the NOx generated in the plant is kept constant. The gasification power plant can be operated to maintain the range value. That is, when the reaction time is increased, switching to the upstream supply position 4 is performed, and when the reaction time is decreased, switching to the downstream supply position 4 is performed to optimize the secured reaction time.

Next, a fifth embodiment of the present invention will be described. In addition, the same code | symbol is attached | subjected about the same member and component as the above-mentioned power plant, and those detailed description is abbreviate | omitted. In the present embodiment, a gas turbine fuel reforming power generation gas turbine plant will be described as an example of an exhaust gas circulation thermal power plant. FIG. 7 is a schematic diagram showing the configuration of a gasification gas fuel reforming power generation gas turbine plant. This plant includes a bypass passage 25 that mixes part or all of the oxidant supplied to the gas turbine combustor 5 with the fuel gas. In the present embodiment, a system AO 23 (bypass passage 25) for supplying a part or all of the oxidant supplied to the gas turbine combustor 5 to the supply position 4 is provided, and the reaction gas (mixed gas) composition is mainly used. By adjusting the O ₂ component concentration, the mutual decomposition reaction of NH ₃ in the fuel gas and NO in the diluent into N ₂ described in the general reaction formula (1) is adjusted.

FIG. 8 shows the result of investigation of the decomposition of NH ₃ in the gasified gas fuel CG ₂ and NO in the gas turbine exhaust gas G by numerical analysis based on reaction kinetics in the mixed gas flow path 22. In the numerical analysis, the same method as in FIG. 2 is used. The analysis conditions are the gas mixture shown in Table 1 and a part of diluent (three times the diluent of gasification gas fuel) mixed gas (reference conditions in Table 2) and supplied to the gas turbine combustor 5 Shows a comparison result of the analysis when a part of the oxidizing agent to be supplied is mixed and the analysis result when the O ₂ component concentration is reduced from the mixed gas (O ₂ concentration = 0.25 vol%). . The NH ₃ concentration in the gasified gas fuel was set to 500 ppmv, and the NH ₃ and NO concentrations after mixing the gasified gas fuel, the diluent and the oxidant were set to 125 ppmv, respectively.

According to the analysis result of FIG. 8, it can be seen that 40-60% (DeTFN) of NH ₃ and NO as a whole can be decomposed by optimizing the reaction temperature according to the O ₂ component concentration in the mixed gas. At this time, it has been confirmed that the oxidation reaction of CO and H ₂ which are main combustible components in the gasified gas fuel hardly occurs. Since the optimum reaction temperature varies depending on the composition of the gasified gas fuel, the diluent and the oxidant, whether data is obtained in advance and the optimum reaction temperature for each composition is obtained (adjustment in advance) The optimum reaction temperature may be obtained while operating the gasification power plant by the reaction kinetic analysis (feedback adjustment).

In consideration of mixing an oxidizing agent with gasified gas fuel, it is desirable that the reaction temperature be low. The analysis result in FIG. 8 shows that the mutual decomposition reaction of NH ₃ and NO into N ₂ can be promoted at a reaction temperature as low as 350 ° C. while suppressing the oxidation of the fuel. As a result, it is possible to realize a closed-cycle gas turbine power plant for gasified gas fuel that reduces the initial cost and simplifies the system.

Next, a sixth embodiment of the present invention will be described. In addition, the same code | symbol is attached | subjected about the same member and component as the above-mentioned power plant, and those detailed description is abbreviate | omitted. In the present embodiment, a gas turbine fuel reforming power generation gas turbine plant will be described as an example of an exhaust gas circulation thermal power plant. FIG. 9 is a schematic diagram showing the configuration of a gasification gas fuel reforming type power generation gas turbine plant. In this plant, the NH ₃ concentration in the gasification gas fuel CG3 supplied to the combustor 5 and the NO concentration in the gas turbine exhaust gas G are monitored by the analyzer 15, and the NO concentration in the gas turbine combustion exhaust gas is determined. Adjusting the reaction temperature of the mixed gas flow path 22 and adjusting the supply amount of the oxidant and gas turbine combustion exhaust gas HG2 (diluent) introduced into the supply position 4 so as to be maintained within a certain range of values. It is characterized by. In the present embodiment, the NH ₃ concentration in the gasified gas fuel CG3 and the NO concentration in the gas turbine exhaust gas G are monitored by the same analyzer 15, but each is separately used using a dedicated analyzer. You may make it monitor.

  In the present embodiment, in the middle of the bypass passage 25 that mixes a part or all of the oxidant supplied to the gas turbine combustor 5 with the fuel gas, the second supply amount of the oxidant mixed with the fuel gas is increased or decreased. A flow rate adjusting means 26 is provided. As the second flow rate adjusting means 26, for example, a flow rate adjusting valve that receives the operation signal 16a from the analyzing device 16 and changes the valve opening degree can be used, but is not limited thereto.

The values of the state quantities of the gasified gas fuel CG3 and the gas turbine exhaust gas G are sent from the analyzer 15 to the analyzer 16, and NH ₃ in the gasified gas fuel CG3 and NO N ₂ in the gas turbine exhaust gas G are sent. The optimal condition for promoting the decomposition into the gas is calculated, the signal 16a indicating the optimal reaction temperature value of the fuel reforming section, the supply amount of the gas turbine combustion exhaust gas and oxidant AO23 supplied to the fuel reforming section An instructing signal 16b is transmitted. For optimal reaction conditions in the fuel reforming section, for example, numerical analysis based on reaction kinetics described in the first embodiment may be used. As shown in FIG. 2 and FIG. 8, it is possible to calculate the optimum reaction temperature according to the composition of the gasified gas fuel CG3 and the gas turbine exhaust gas G by numerical analysis of reaction kinetics.

  The fuel reforming unit of the present embodiment is provided with a temperature adjusting heater (not shown), and the heater is operated by a signal 16a from the analysis device 16 to adjust the temperature of the fuel reforming unit. In the heater, the amount of heating by fuel or electricity is adjusted so that the heating temperature according to the signal 16a is obtained. However, the temperature adjustment means is not limited to this, and a heat source may be obtained for the gasification furnace 2 or the gas turbine exhaust gas G, the gas turbine casing, and the expansion turbine 6. In this case, since an external heat source is not used, it can be operated without impairing the plant thermal efficiency.

  As for the supply amounts of the gas turbine combustion exhaust gas HG2 and the oxidant AO23 supplied to the supply position 4, for example, a flow rate adjustment valve (first flow rate adjustment unit 23) and a flow rate adjustment valve (second flow rate adjustment unit 26). ) Adjust according to the opening.

As a result, the reaction conditions in the mixed gas flow path 22 are optimized, and the NH ₃ in the gasification gas fuel and the NO in the gas turbine combustion exhaust gas are decomposed into N ₂ while minimizing the influence on the plant. The gasification power plant can be operated so that NOx generated in the plant is maintained within a certain range.

  Next, a seventh embodiment of the present invention will be described. In addition, the same code | symbol is attached | subjected about the same member and component as the above-mentioned power plant, and those detailed description is abbreviate | omitted. In the present embodiment, a gas turbine fuel reforming power generation gas turbine plant will be described as an example of an exhaust gas circulation thermal power plant. FIG. 10 shows the reaction heat required for the fuel reforming reaction in the fuel reforming section of the gas turbine fuel reforming power generation gas turbine plant, and the heat source for the gasification furnace 2 or gas turbine exhaust gas G. is there.

As shown in the general reaction formula (1), O ₂ is required in the reaction system for the mutual decomposition reaction of NH ₃ and NO into N ₂ in the fuel reforming section. As shown in FIG. 8, when the O ₂ concentration in the reaction system is low, a reaction temperature of 400 ° C. to 700 ° C. is required for the overall reaction (1) to have a reaction rate of a predetermined value or more. On the other hand, when the O ₂ concentration in the reaction system is high, NH ₃ is oxidized to NO at a high reaction temperature, so the reaction temperature needs to be set to 300 ° C. to 500 ° C. as shown in FIG. Further, when the O ₂ concentration is high, it is necessary to set the reaction temperature to a lower temperature. That is, in order to simultaneously decompose NH ₃ in the gasified gas fuel and NO in the diluent into N ₂ in the fuel reforming section, the O ₂ concentration in the fuel reforming section and the reaction temperature have an inverse correlation. It will be. In order to obtain a high reaction temperature, it is appropriate to use the gasification furnace 2 as a heat source. Conversely, when it is important to adjust the temperature to a lower temperature and a narrower temperature range, the exhaust gas line of the gas turbine 6 is By using a heat source, the temperature can be adjusted to a predetermined temperature. For example, in order to circulate the gas turbine combustion exhaust gas and supply it to the gas turbine 6, it is necessary to lower the temperature of the exhaust gas and then increase the pressure by the compressor 8. A heat source 17 is provided by a heat exchanger 17 provided in the exhaust gas line. Or by using the exhaust heat recovery boiler 7 as a heat source, it is possible to adjust to an arbitrary temperature below the exhaust gas temperature. As a result, there is no need to obtain a heat source required for fuel reforming outside, and NH ₃ in the gasification gas fuel and NO in the gas turbine exhaust gas are decomposed into N ₂ and generated in the plant without requiring on-site power. NOx to be reduced can be reduced. This makes it possible to realize a highly efficient gasification power plant that suppresses the increase of NOx in the closed-cycle gas turbine exhaust and reduces the CO ₂ emission amount.

  Next, an eighth embodiment of the present invention will be described. In addition, the same code | symbol is attached | subjected about the same member and component as the above-mentioned power plant, and those detailed description is abbreviate | omitted. In the present embodiment, a gas turbine fuel reforming power generation gas turbine plant will be described as an example of an exhaust gas circulation thermal power plant. FIG. 11 is a schematic diagram showing the installation location of the fuel reforming section of the gas turbine fuel reforming power generation gas turbine plant. The plant of this embodiment has a fuel reforming unit as compared with the plant of the first embodiment, in the upstream part in the combustor 5, between the inner cylinder and the outer cylinder, or in the gas turbine combustor five tail cylinder. It is provided in the part.

  By providing the fuel reforming section between the inner cylinder and the outer cylinder of the gas turbine combustor 5 or in the combustor 5 tail cylinder section, fuel reforming is realized while cooling the combustor 5 inner cylinder and tail cylinder. . Further, by providing the function of the fuel reforming unit in the upstream portion of the gas turbine combustor 5, part of the reaction heat due to the combustion reaction can be used for fuel reforming, and the heat source for fuel reforming The equipment and structure required for heat exchange with the fuel are not required, and fuel reforming is realized with a simpler structure.

  With the structure of the fuel reforming unit described above, in the gasification power plant that employs dry gas purification within the operating load range of the gas turbine, as in the plant of the first embodiment, without impairing the thermal efficiency of the plant, In addition, with a simpler structure as a plant system, it is possible to maintain a NOx generation amount within a certain range and realize a closed cycle gas turbine.

  Next, a ninth embodiment of the present invention will be described. In addition, the same code | symbol is attached | subjected about the same member and component as the above-mentioned power plant, and those detailed description is abbreviate | omitted. In this embodiment, a gas turbine fuel reforming type combined gas turbine plant will be described as an example of an exhaust gas circulation thermal power plant. FIG. 12 is a schematic diagram showing the configuration of a gasification gas fuel reforming type combined power generation gas turbine plant. The plant of this embodiment is characterized in that the fuel reforming section is provided inside the turbine blade.

In the gas turbine, it is necessary to cool the stationary blade and the moving blade in the expansion turbine 6. In normal industrial gas turbines, blades are mainly cooled by air that is a working medium of the gas turbine, and in some gas turbines, steam is used for cooling. However, in the closed cycle gas turbine by the O ₂ stoichiometric combustion of the gasified gas fuel targeted by the present invention, the gas turbine exhaust gas G circulates. In this system, it is conceivable to use steam or cool gas turbine combustion exhaust gas G, gasified gas fuel or oxidant to cool the turbine blades.

In this embodiment, by providing the fuel reforming portion inside the gas turbine blade, the turbine blade is cooled, and at the same time, NH ₃ in the gasified gas fuel and NO in the gas turbine exhaust gas are decomposed into N ₂ . As a result, in addition to not requiring in-house power for the heat source of the fuel reforming section, a synergistic effect is obtained in that the plant thermal efficiency can be improved by recovering the heat that has cooled the turbine blades.

  Next, a tenth embodiment of the present invention will be described. In addition, the same code | symbol is attached | subjected about the same member and component as the above-mentioned power plant, and those detailed description is abbreviate | omitted. In the present embodiment, a gas turbine fuel reforming power generation gas turbine plant will be described as an example of an exhaust gas circulation thermal power plant. FIG. 13 shows the configuration of a gasification gas fuel reforming power generation gas turbine plant, and FIG. 14 shows the operation method.

  In this plant, a plurality of supply positions 4 of the diluent to the fuel gas are provided, a switching means 24 for switching the supply position 4 to be used, a first flow rate adjusting means 23 for increasing or decreasing the supply amount of the diluent, and a combustor. 5 includes a bypass passage 25 that mixes part or all of the oxidant supplied to the fuel gas 5 with the fuel gas, and a second flow rate adjusting means 26 that increases or decreases the supply amount of the oxidant mixed with the fuel gas.

Further, this plant measures the nitrogen oxide concentration in the exhaust gas while performing the rated operation, and performs the rated operation while adjusting the measured value so as to be a target value determined in advance. That is, feedback control is performed so that the concentration of nitrogen oxides in the exhaust gas falls within a predetermined range of values. The values of the state quantities of the gasified gas fuel CG3 and the gas turbine exhaust gas G are sent from the analyzer 15 to the analyzer 16. The analysis device 16 calculates optimum conditions for promoting the decomposition of NH ₃ in the gasified gas fuel CG ₃ and NO in the gas turbine exhaust gas G into N ₂ , and the first flow rate adjusting means 23 and the switching means 24. The second flow rate adjusting means 26 is operated. In addition, description of the waste heat recovery boiler 7 grade | etc., Is abbreviate | omitted in FIG.

After a certain amount of time has elapsed after the plant operation is started and the operation is stabilized, the rated operation is started and feedback control is performed. In the rated operation, the fuel gas composition (NH ₃ , O _2, etc.) and the exhaust gas (diluent) composition (NO, O _2, etc.) are measured and monitored (step S 41).

In addition, the relationship between the NO / NH ₃ molar ratio, the O ₂ concentration in the mixed gas (fuel gas and diluent) and the D / F ratio (= the amount of diluent / the amount of fuel gas), the decomposition reaction of NH ₃ The relationship between the appropriate reaction time and the diluent supply position 4 that can secure the reaction time, and the relationship between the appropriate reaction temperature of the NH ₃ decomposition reaction and the diluent supply position 4 that can secure the reaction temperature are numerical values. The database is obtained in advance by analysis and plant design data, and the plant control device (not shown) refers to this database and determines the appropriate values based on the measured values of the fuel gas composition and the diluent composition. The D / F ratio and diluent supply position 4 are determined (step S42), and the switching means 24 and the first flow rate adjusting means 23 are operated (step S43). In step S42, the second flow rate adjusting means 26 is reset (operated to open degree = 0).

The control device refers to the measured value of the fuel gas composition (NH ₃ , O _2, etc.) and the measured value of the exhaust gas composition by the analyzer 15 (step S44), and the NOx concentration in the exhaust gas is within a certain range. (Yes in step S45), the process proceeds to step S46 to maintain the current operation. Thereafter, the control device repeatedly executes step S46 → step S43 → step S44 → step S45 → step S46 →... Until the determination in step S45 becomes No, and operates while balancing the NOx concentration in the exhaust gas within a certain range. continue.

On the other hand, if the NOx concentration in the exhaust gas deviates from a certain range, the control device proceeds from step S45 to step S47 and reexamines the D / F ratio and the supply position 4 to be used. That is, the control device refers to the stored database, determines an appropriate D / F ratio based on the measured values of the fuel gas composition and the diluent composition (step S47), and determines the determined D / F ratio. An appropriate reaction temperature and reaction time are determined based on the O ₂ concentration in the mixed gas obtained at step S48.

  When the determined reaction temperature and reaction time are sufficient, the process proceeds from step S49 to step S50, and the supply position of the diluent that satisfies the determined reaction temperature and reaction time is determined with reference to the database. Thereafter, the process returns to step S43, and the first flow rate adjusting means 23 is operated so as to achieve the D / F ratio determined in step S47, and the switching means 24 is operated so as to be the supply position 4 determined in step S50. .

On the other hand, when the reaction temperature and the reaction time determined in step S48 are insufficient, the process proceeds from step S49 to step S51, and the O ₂ concentration in the mixed gas is set so that an appropriate reaction temperature and reaction time can be obtained. adjust. The control device first determines whether or not an appropriate reaction temperature and reaction time can be obtained by adjusting the O ₂ concentration in the mixed gas by adjusting the D / F ratio (step S51). That is, the control device performs a trial calculation of the O ₂ concentration in the mixed gas when the D / F ratio is changed, and adjusts the D / F ratio to adjust the reaction temperature and reaction time appropriately. Estimate the O ₂ concentration, and calculate the D / F that minimizes the NO concentration in the exhaust gas circulation within a certain range. In the calculated D / F, as shown in FIG. 23 or FIG. 25 described later, the exhaust gas NO concentration calculated from the decomposition rate DeTFN is adjusted to be as small as possible within the target NOx adjustment range. Judge whether or not.

When an appropriate reaction temperature and reaction time can be obtained by adjusting the O ₂ concentration in the mixed gas by adjusting the D / F ratio, the process proceeds from step S51 to step S47, and the D / F ratio is reset. To do. On the other hand, when the appropriate reaction temperature and reaction time cannot be obtained by adjusting the O ₂ concentration in the mixed gas by adjusting the D / F ratio, the process proceeds from step S51 to step S52, and the O ₂ concentration in the mixed gas is reached. After the second flow rate adjusting means 26 is operated to compensate for the shortage, the process returns to step S48. In step S48, an appropriate reaction temperature and reaction time are determined by adding the amount of O ₂ added by the second flow rate adjusting means 26 to the O ₂ amount based on the D / F ratio, and the determined reaction temperature and reaction time are determined. If it is sufficient, the process proceeds from step S49 to step S50, the supply position of the diluent that satisfies the reaction temperature and reaction time is determined with reference to the database, and step S43 and subsequent steps are executed.

On the other hand, when the reaction temperature and the reaction time determined in step S48 are insufficient, the process proceeds from step S49 to step S51. In step S51, an appropriate reaction is performed by adjusting the concentration of O ₂ in the mixed gas by adjusting the D / F ratio after taking into account the amount of O ₂ added by the second flow rate adjusting means 26 in the previous execution of step S52. It is determined whether or not the temperature and reaction time can be obtained. If an appropriate reaction temperature and reaction time can be obtained, the process proceeds to step S47 to reset the D / F ratio and execute step S48 and subsequent steps. To do. If an appropriate reaction temperature and reaction time can be obtained, the process proceeds to step S52, the second flow rate adjusting means 26 is operated again, and then step S48 and subsequent steps are executed.

By operating the plant in this way, the supply and decomposition of NH ₃ and the decomposition and generation of NOx are balanced, so that the NOx concentration in the exhaust gas falls within a certain range and a closed cycle gas turbine plant is established. Can do.

That is, to measure and analyze the composition of the gasified gas fuel and the composition of the diluent or oxidant supplied to the fuel reforming section, to decompose ammonia in the gasified gas fuel and NO in the diluent into N ₂ The optimum reaction temperature and reaction time are derived, and the optimum feed position 4 for mixing the diluent is selected. In order to derive the optimum reaction temperature and reaction time, a database may be created in advance by experiment or numerical analysis, or may be calculated by numerical analysis based on the composition of gasified gas fuel, diluent, or oxidant. Then, the composition of the gas turbine combustion exhaust gas is measured, and the reaction conditions of the fuel reforming section that can be balanced to a predetermined range of NO concentration are set. According to this, it is possible to avoid setting the reaction conditions in the fuel reforming section to conditions more severe than necessary. Further, even when a catalyst is used for promoting the reaction in the fuel reforming section, unnecessary reaction promotion can be avoided, so that the life of the catalyst can be extended.

  In the above description, a database has been created in advance before operation, and feedback control has been performed using this database. Each time numerical analysis is performed, and feedback control may be performed so that the NOx concentration in the exhaust gas falls within a certain range.

  The above-described embodiment is an example of a preferred embodiment of the present invention, but is not limited thereto, and various modifications can be made without departing from the scope of the present invention.

(1) In a thermal power plant where gasified gas generated in a gasifier is purified by a dry gas purifier and burned in a combustor that performs O ₂ stoichiometric combustion as a fuel gas, no external heat source or power is required In addition, a method for vapor-phase decomposition of ammonia in gasified fuel into N ₂ without a catalyst was examined by reaction kinetic analysis assuming a homogeneous premixed reaction. The analysis was performed on a 416 MW class CO ₂ recovery type coal gasification combined power plant with a power generation end output. However, the plant output or the like does not affect the analysis of NH ₃ decomposition itself.

The meanings of the main symbols are as follows.
D / F: Dilutant / fuel supply amount ratio (dilution ratio): Amount [mol / mol] indicating how many times the diluent has been supplied
DeNH ₃ ... Decomposition rate of NH ₃ in fuel to N ₂ [%]
DeNOx: Decomposition rate of NO in exhaust gas supplied to the reactor into N ₂ [%]
DeTFN: total decomposition rate of NH ₃ and NO into N ₂ in the reactor [%] = (1 − ((NH ₃ + NO) concentration after reaction) ÷ ((NH ₃ + NO) concentration before reaction) )) X 100 [%]
Tr ... Reaction temperature [° C]
t ... reaction time [s (seconds)]
φ * ... Equivalent ratio calculated only from fuel and oxidizer without considering O ₂ component in diluent

This will be specifically described below.
(2. Application of ammonia decomposition method to exhaust gas circulation / O ₂ stoichiometric combustion closed cycle gas turbine)
(2.1) Features of Exhaust Circulation / O ₂ Stoichiometric Combustion Closed-Cycle Gas Turbine FIG. 16 shows the configuration of a closed-cycle thermal power plant targeted in this analysis. In the closed-cycle thermal power plant _model, the _O 2 -CO ₂ blown coal gasification fuel is stoichiometric combustion at O _2, and recycling most of the gas turbine exhaust gas mainly composed of CO ₂ and H _{2 O} A closed loop is configured to supply the combustor and adjust the combustion temperature. Moreover, after separating and removing halogen, mercury, and H ₂ O from a part of gas turbine exhaust gas, CO ₂ is recovered, and about 10% of this CO ₂ is used for transporting coal to the gasifier. . That is, without requiring the application of steam shift reaction as the IGCC employing the pre-combustion recovery system, the moisture in the exhaust gas by by steam separator separating and recovering high-purity CO _2, CO ₂ recovered power To achieve zero emission IGCC power generation.

As shown in Table 1, the gasified fuel is expected to contain several hundred to several thousand ppmv of ammonia (NH ₃ ) generated due to the nitrogen compound in the coal during the gasification process. When the dry method is adopted for gas purification, NH ₃ is not removed but supplied to the gas turbine combustor, fuel NOx is generated in the combustion process, and the fuel NOx concentration is increased by circulation of the exhaust gas. FIG. 17 analytically examines the tendency of the fuel NOx production concentration in the exhaust gas at the combustor outlet to increase due to exhaust gas circulation. In the analysis, all NH ₃ in the gasified fuel is oxidized to NOx, and the generation of thermal NOx is assumed to be zero because it is relatively small relative to the amount of fuel NOx produced, and other exhaust gas circulation The amount (amount of diluent supplied in Table 1) and the like are constant under the conditions shown in Table 1. The NH ₃ concentration in gasified fuel is a parameter because it is affected by the type of coal and the gasification method.

In any of the fuel NH ₃ concentrations, the fuel NOx concentration increases in a similar manner by repeating exhaust gas circulation, and each of them tends to saturate to a constant value. That is, the number of exhaust circulations is 30, and the fuel NOx concentration in the exhaust circulation gas is 99% or more of the saturation concentration. For example, when the concentration of NH ₃ in the fuel is 500 ppmv or 1000 ppmv, the saturation concentration of fuel NOx is 490 ppmv and 980 ppmv, respectively, which are values proportional to the NH ₃ concentration in the fuel. When CO ₂ is separated from the exhaust gas, condensed water is separated by brackish water separation.

In view of the above, in this analysis, a closed cycle thermal power plant that employs dry gas refining is modeled and a method for non-catalytic decomposition of NH ₃ in gasified fuel into N ₂ in the gas phase is analyzed.

(2.2) Method of Decomposing Ammonia in Gasified Fuel In this analysis, the exhaust gas denitration reaction by the dry method indicated by the general reaction formula (1) of the mathematical formula 3 or the general reaction formula (2) of the mathematical formula 4 is applied. NH ₃ in the liquefied fuel and NOx in the exhaust gas are reacted to decompose into nitrogen (N ₂ ) and water vapor (H ₂ O).

[Equation 3]
NO + NH ₃ + 1 / 4O ₂ → N ₂ + 3 / 2H ₂ O (1)

[Equation 4]
6NO ₂ + 8NH ₃ → 7N ₂ + 12H ₂ O (2)

Here, although the NOx is a general term for NO and NO _2, NOx in the circulating exhaust gas of thermal power plant model is mostly is NO, decomposition of NH ₃ proceeds by overall reaction equation (1).

In normal dry flue gas denitration, NH ₃ as a reducing agent is supplied to exhaust gas, and a selective catalytic reduction method in which the reaction is performed on the catalyst and a method in which the reaction is performed in the gas phase without using a catalyst (non-catalytic Reduction method). Since the catalyst-free reduction method does not use a catalyst, it has the advantage of reducing the initial cost and operation cost, but is hardly used due to restrictions in use such as control of the reaction temperature.

In the present invention, NH ₃ in gasified fuel and NO in circulating exhaust gas are reacted to decompose into N ₂ , and fuel pretreatment for reducing fuel N and decomposition of NO in exhaust gas are performed simultaneously. By realizing it, it is intended to reduce NOx that increases in the circulating exhaust gas. That is, instead of supplying O ₂ and NO from the outside as in the prior art, the remaining NH ₃ that is not decomposed in the non-catalytic reaction section is oxidized to NO in the combustor, and is supplied to the reaction section as circulating exhaust gas. To maintain the balance between decomposition to N ₂ and oxidation to NO. Thereby, mutual decomposition of NH ₃ and NO is realized under a low temperature condition that could not be realized until now.

The features (a) to (d) of the present invention are described below, and an example of an outline of a system when the present technique is applied to a closed cycle gas turbine for CO ₂ recovery type IGCC is shown in FIG.
(A) Necessary for the NH ₃ decomposition reaction by previously mixing the circulating exhaust gas containing fuel NO generated in the combustor due to NH ₃ in the gasified fuel and the residual O ₂ component with the gasified fuel. NO and O ₂ are supplied, there is no need to procure from the outside, and NO and O ₂ can be supplied safely.
(B) By mixing the exhaust circulation gas, the H ₂ component in the gasified fuel is relatively reduced, and the inhibition of NH ₃ decomposition by high concentration H ₂ is suppressed, while the reaction due to the coexistence of H ₂ is performed at a low temperature. doing.
(C) The denitration reaction (1) is promoted at the supply temperature (400 to 600 ° C.) of the gasified fuel or the exhaust circulation gas to the combustor, and heating or the like is unnecessary.
(D) Since no catalyst is used, there is no problem such as deterioration or blockage of the catalyst portion. In addition, there is no need for operating costs for the catalyst.

In the system operation example shown in FIG. 18, 40% of the total (2 molar equivalents) of NH ₃ in the gasified fuel and NO in the circulating exhaust gas is decomposed into N ₂ in the NH ₃ decomposition reaction section (reactor). Undecomposed NH ₃ is oxidized to NO by a gas turbine combustor, and NO is supplied to the reactor by exhaust circulation.

When NH ₃ in the fuel gas is 1 molar equivalent, the fuel NO in the entire exhaust gas is saturated at 1.2 molar equivalent. Among them, exhaust gas containing 1 molar equivalent of fuel NO is circulated and supplied to the reactor, and exhaust gas containing 0.2 molar equivalent of fuel NO is separated and led to a CO ₂ recovery system. In this case, since the fuel NO discharged out of the system is 0.2 molar equivalent, the decomposition rate of NH ₃ in the fuel supplied to the gas turbine corresponds to 80%.

(3. Reaction kinetics numerical analysis method)
The reactor model, elementary reaction model, and numerical analysis method adopted in this analysis are described below.

(3.1) Reactor model and elementary reaction model In this analysis, a completely stirred reactor (homogeneous reactor) model was adopted. In this analysis model, it is assumed that all chemical species are uniformly mixed in the reaction process, the diffusion / mixing process is not considered, and the reaction proceeds at a constant temperature and a constant pressure.

The elementary reaction model is a reaction scheme proposed by Miller-Bowman. By comparing it with the experimental results in the reductive decomposition reaction of fuel N in gasified fuel and the oxidation reaction of fuel N in CH ₄ premixed flame. Validity and scope of application have been confirmed.

  The reaction scheme consists of 248 elementary reactions, and the chemical species considered are 50 components. For thermodynamic data, JANAF thermochemical property values are used. For chemical species not listed in the physical property value table, Gibbs standard formation energy (ΔG °) and chemical equilibrium constant (K ). The value of ΔG ° was obtained from the CHEMKIN database (Formula 5).

[Equation 5]
ΔG ° = R × T × ln (K) (3)

(3.2) Numerical analysis method Consider one chemical reaction formula (Formula 6).

  The generation rate of the chemical species X is given by Equation 7.

  When there are n types of reaction formulas with respect to the chemical species X, the generation rate of the chemical species X is the summation of Equation 7 and is given by Equation 8.

  Assuming now that a chemical reaction equation system is considered and Ni chemical species are included therein, Equation 6 can be created for each of Ni chemical species. That is, a differential equation for obtaining the concentration of each chemical species with respect to the reaction time can be created from a chemical reaction equation system including Ni chemical species. By solving this nonlinear differential equation system, the concentration of each chemical species after an arbitrary reaction time can be determined. The Gear method was used to solve the differential equation.

(3.3) Validity of Analysis Method FIG. 19 shows the results of reaction analysis under the experimental conditions of Lyon et al. Regarding non-catalytic denitration compared with the experimental results. In the analysis, a mixed gas _{NH 3: 380ppmv-NO: 225ppmv} -H 2: 380ppmv-O 2: assuming a uniform reaction 2 vol% to subject the balance _{N 2,} the pressure is atmospheric pressure, the reaction temperature is as constant at each temperature Yes.

The analysis results such as the reaction temperature at which NH ₃ and NO start to decompose and the NO regeneration behavior under high temperature conditions are in good agreement with the experimental data, and this analysis method can reproduce the NH ₃ and NO generation and decomposition behavior. Is shown.

(4. Ammonia decomposition characteristics)
The reference conditions and analysis range of this analysis are shown in Table 2 (analysis conditions for NH ₃ vapor phase decomposition). Under the reference conditions, the reaction temperature and pressure conditions were set temperatures and pressures when gasified fuel or circulating exhaust gas (diluent in Table 1) was supplied to the gas turbine combustor. The ratio of the mixed amount of exhaust gas to fuel (dilution ratio D / F) is 3 mol / mol. At this time, the concentration of the O ₂ component in the circulating exhaust gas decreases from 0.9 vol% to 0.66 vol% due to the mixing of the fuel. The composition of the gasified fuel was based on the rated conditions shown in Table 1, and the NH ₃ concentration in the fuel was set to 500 ppmv.

Regarding the NH ₃ concentration in gasified fuel, Leppalahti et al. Have evaluated the production of fuel N by various gasification methods such as peat, and the NH ₃ concentration in gasified fuel has been reported to exceed 10,000 ppmv. On the other hand, there are indications that the NH ₃ concentration is approximately up to about 5000 ppmv when looking at the literature surveyed on coal gasification fuel. There are gasification methods suitable for the raw materials and the amount of power generation, and there are no reports of such high NH ₃ concentrations for high-temperature, high-pressure spouted bed coal gasification fuels. Therefore, in this analysis, the decomposition characteristics were examined in the NH ₃ concentration range up to 3000 ppmv.

Gasification fuel supply temperature, pressure and composition (CO / H ₂ concentration, NH ₃ concentration) vary depending on IGCC system configuration and operation, coal type, etc., and the O ₂ component concentration in the gas turbine circulation exhaust gas is also a closed cycle gas turbine. It depends on the setting conditions. However, it is not much different. In addition, in the general reaction formula (1), apparently, NH ₃ and equivalent of NO react with 1/4 molar equivalent of O ₂ component. However, it is actually a reaction phenomenon involving a large number of elementary reactions, and in a multi-component mixed gas, NH ₃ , NO and O ₂ components not only interact but each combustible component in the mixed gas. Or react with diluent components. Therefore, to set the analysis range as shown in Table 2, the amount of gas diluent on degradation properties of NH _3, the influence of the circulating amount of NO (NO / NH ₃ molar ratio), a flammable gas fuels The effects of the components CO and H ₂ will be examined from reaction kinetic analysis using an elementary reaction model, and the application effect and scope of the present invention will be clarified.

(4.1) exploded characteristic diagram 2 of the NH ₃ and NO is an illustration of the reaction analysis the effect of reaction temperature on the formation decomposition characteristics of the NH ₃ and NO. In the analysis, as shown in the standard conditions of Table 2, a diluent with a dilution ratio D / F of 3 is uniformly mixed with gasified fuel, and the reaction time is 10 s under the condition that the reaction temperature is constant at each temperature. The concentration of NH ₃ and NO components later is examined. The concentration of the NH ₃ component contained in the gasified fuel is constant at 500 ppmv, and the NO component supplied by mixing the diluent is set to be equivalent to NH ₃ in the gasified fuel.

NH ₃ in the mixed gas (marker ◯ in the figure) starts decomposing when the reaction temperature exceeds 250 ° C., and shows a decomposition rate of 90% or higher at 600 ° C. or higher. On the other hand, NO (□ in the figure) shows almost the same decomposition behavior as NH ₃ up to a reaction temperature of 400 ° C., and the decomposition rate decreases conversely when it exceeds 400 ° C. Further, at 600 ° C. or more, NO ₃ is oxidized due to oxidation of NH _3. It can be seen that is generated. As a result, the decomposition rate (DeTFN: Δ in the figure) for the total of NH ₃ and NO shows a maximum value at a reaction temperature of 400 to 450 ° C., and a minimum value at 800 ° C. That is, by setting the reaction temperature to 400 to 450 ° C., the decomposition rate of NH ₃ in fuel (DeNH ₃ ) is 54 to 69%, the decomposition rate of NO in circulating exhaust gas (DeNO) is 48 to 37%, NH The total decomposition rate (DeTFN) of ₃ and NO has reached 51 to 53%.

In a closed cycle gas turbine, there is a concern that NOx increases in the exhaust gas due to exhaust circulation. Figure 20 under conditions of a reaction temperature of 400 ° C. as shown in FIG. 2, compared with the case of not applying the decomposition method of the NH ₃ Effect of circulating number of exhaust gas on the fuel NOx generation characteristics in the circulating exhaust gas Show. In the analysis, the initial value of the NO / NH ₃ molar ratio is shown as a parameter. The total decomposition rate DeTFN of NH _{3 in the} fuel and NO in the exhaust gas is assumed to change according to the D / F ratio. It can be seen that at any initial NO / NH ₃ molar ratio, NO in the exhaust gas circulation converges to 0.71 molar equivalent of NH _{3 in} the fuel. This corresponds to 13% of the saturation concentration when NH ₃ decomposition is not performed. For example, set up a denitrification equipment, to reduce the NOx concentration in the circulating exhaust gas to 13% of the saturation concentration is required to be operated in denitration efficiency 87%, NH ₃ uncatalyzed decomposition technique which Have the same effect.

FIG. 21 shows the change over time of NH ₃ and NO under the same conditions as in FIG. 2, using the reaction temperature as a parameter. NH ₃ in the gasified fuel is diluted to 125 ppmv by mixing a diluent 3 times the molar equivalent of the fuel (dilution ratio D / F = 3), and the NO component is equivalent to NH ₃ .

When the reaction temperature is 300 ° C., NH ₃ and NO start mutual decomposition from the reaction time of about 1 s, and the concentrations of NH ₃ and NO decrease almost similarly as the reaction time elapses. On the other hand, as the reaction temperature rises, the mutual decomposition reaction of NH ₃ and NO occurs early, and while the decomposition amount of NH ₃ increases, the decomposition amount of NO decreases and the reaction temperature reaches 600 ° C. Then, a part of NH ₃ is oxidized to NO and the NO concentration is increased.

Further, NO generated by the oxidation of NH ₃ under a high temperature condition is consumed and reduced by the oxidation of H ₂ that is a fuel gas component as the reaction time elapses. For example, at a reaction temperature of 1200 ° C., NO increased to 1.8 times the initial concentration due to the oxidation of NH ₃ , and almost completely decomposed in a reaction time of 100 s or longer. On the other hand, as shown in FIG. 22, the H ₂ component in the gasified fuel decreases to about 60% of the initial concentration under the reaction temperature of 1200 ° C. At this time, although not shown in the drawing, a CO component of almost the same amount as the amount of decrease in H ₂ is generated and increased in the fuel, and the fuel composition changes although the fuel heating value hardly changes. The change in the fuel composition changes the combustibility and thus affects the combustion performance of the gas turbine. That is, when mixing a diluent with gasified fuel, it is important to maintain the mixed gas temperature at 800 ° C. or lower.

(4.2) Effect of reaction time FIG. 23 shows the effect of reaction temperature on the decomposition characteristics of NH ₃ and NO under the same conditions as in FIG. 2, using the reaction time as a parameter (0.1 s to 1000 s). Show. In any reaction time, the decomposition rate of NH ₃ shows almost the same tendency, and the decomposition rate increases as the reaction temperature increases ((a) of FIG. 23). Further, when compared at the same reaction temperature in a temperature range of 600 ° C. or lower, the NH ₃ decomposition rate increases as the reaction time becomes longer, but the decomposition rate is almost the same at a reaction time of 10 seconds or longer.

On the other hand, the decomposition characteristics of NO showed a tendency different from that of NH ₃ , and showed the maximum decomposition rate (maximum value) at a reaction temperature of 400 ° C. except for the case of a reaction time of 1000 s (FIG. 23B). . Further, it can be seen that at any reaction temperature, the decomposition rate of NO becomes almost the same level when the reaction time is 10 s or more. As a result, as shown in FIG. 23C, the reaction temperature that maximizes the total decomposition rate of NH ₃ and NO also decreases as the reaction time increases in the range of 10 s or less, and is almost constant over the reaction time of 10 s or more. Indicates the value. That is, it was found that by setting the reaction temperature to 400 to 450 ° C., the total of NH _{3 in} the fuel and NO concentration in the exhaust gas can be suppressed to ½ or less.

When the reaction time is 1000 s or more, the total decomposition rate of NH ₃ and NO can be increased to 80% or more by setting the reaction temperature to 800 ° C. At that time, the H ₂ component in the fuel is increased. Do not decrease. However, it is difficult to provide a reaction time of 1000 s in an actual plant, and it is necessary to use a catalyst or the like that activates the reaction field.

(4.3) Influence of Diluted Gas Amount FIG. 4 shows the influence of the diluent mixing ratio (dilution ratio D / F: diluent / gasification fuel ratio) on the decomposition characteristics of NH ₃ and NO. In the analysis, the dilution ratio D / F is changed under the rated conditions, and the mixed gas component is also changed. Other analysis conditions are constant according to the reference conditions shown in Table 2.

As the dilution ratio D / F increases, the decomposition rate of NH ₃ increases. On the other hand, the NO decomposition rate reaches a maximum at a D / F ratio of 3 to 4, but shows a decomposition rate of approximately 45 to 48%. As a result, the total decomposition rate of NH ₃ and NO tends to increase gradually as the dilution ratio increases, and a decomposition rate of 50% or more can be obtained when the dilution ratio D / F is 3 or more. it can.

FIG. 24 shows the influence of the dilution ratio D / F on the relationship between the reaction temperature and the decomposition rate of NH ₃ and NO. At any dilution ratio, the NH ₃ decomposition rate shows a similar tendency, and when compared at the same reaction temperature, the NH ₃ decomposition rate increases as the dilution ratio increases.

On the other hand, the NO decomposition rate tends to become maximum at a reaction temperature of 400 ° C., but it can be seen that the NO decomposition rate decreases on the high temperature side as the dilution ratio increases. As a result, the reaction temperature that maximizes the total decomposition rate of NH ₃ and NO is 350 to 450 ° C., and it can be seen that the higher the dilution ratio, the faster the mutual decomposition reaction of NH ₃ and NO at a lower temperature.

(4.4) Influence of Diluting Gas Component (4.4.1) Influence of O ₂ Concentration FIG. 25 shows the influence of the O ₂ component concentration on the mutual decomposition reaction of NH ₃ and NO. In the analysis, the influence is examined in the range of 0.25 to 2.5 vol% of the O ₂ concentration under the reference conditions shown in Table 2. As the O ₂ concentration in the mixed gas increases, the decomposition rate of NH ₃ increases, while the decomposition rate of NO shows a maximum value when the O ₂ concentration is 0.7 to 1.25 vol%. As a result, the total decomposition rate of NH ₃ and NO tends to become maximum when the O ₂ concentration is 1.25 to ₂ vol%.

FIG. 8 shows the influence of the O ₂ component concentration on the relationship between the reaction temperature and the mutual decomposition reaction of NH ₃ and NO. Comparing (a) to (c) of FIG. 8, the reaction temperature that maximizes the NO decomposition rate DeNO or the total decomposition rate DeTFN of NH ₃ and NO decreases with an increase in the O ₂ concentration in the mixed gas. You can see that Further, when the O ₂ concentration is 1 vol% or higher, NO decomposition is not observed at a reaction temperature of 500 ° C. or higher, NO is generated due to the oxidation of some NH ₃ , and the NO concentration is increased. That is, it is important to adjust the reaction temperature according to the O ₂ component concentration in the mixed gas.

(4.4.2) Influence of NO component (NO / NH ₃ molar ratio) FIG. 26 shows the influence of the NO supply amount on the decomposition rate of NH ₃ and NO. In the analysis, under the reference conditions shown in Table 2, the influence of the NO supply amount in the range of 0.5 to 2.5 times (molar ratio) of the NH ₃ concentration is examined.

As the NO / NH ₃ molar ratio increases, the decomposition rate of NH ₃ increases, while the decomposition rate of NO decreases. As a result, the total decomposition rate of NH ₃ and NO tends to be maximized when the NO / NH ₃ molar ratio is in the range of 0.75 to 1.00.

(4.5) Effect of gasified fuel component (4.5.1) Effect of combustible component FIG. 27 shows the relationship between NH ₃ and NO when the ratio of CO and H ₂ components in the gasified fuel is changed. The effect on the decomposition rate is shown. In the analysis, the total concentration of CO and H ₂ components in the gasified fuel is assumed to be constant at 90 vol% (≡66.2 + 23.8 vol%: rated conditions shown in Table 1), and the CO concentration is −20, −10, +10, +20 vol. Comparison is made for%. The other conditions are the standard conditions shown in Table 2.

Each decomposition rate of NH 3, _NO with increasing CO concentrations in the gasification fuel, and NH ₃ and the total decomposition ratio of NO indicates a tendency to rise in the same manner both. That is, it can be seen that the proportion of combustible components in the gasified fuel greatly affects the reaction amount of the equivalent decomposition of NH ₃ and NO according to the general reaction formula (1). This is compared to the CH ₄ component of the high-concentration CO component and trace amounts of is because the high concentration of H ₂ is strongly suppress the mutual decomposition reaction of NH ₃ and NO, the ratio of H ₂ component in the fuel The smaller the NH ₃ and NO decomposition rate is, the smaller it is.

Figure 28 shows the reaction temperature and NH 3, _NO each decomposition rate, and the effect of the ratio of CO and H ₂ component relationships on gasification fuel decomposition rate of the sum of NH ₃ and NO. At a reaction temperature higher than 300 ° C., the NH ₃ decomposition rate is affected by the H ₂ component in the fuel, and the lower the H ₂ concentration (the higher the CO concentration), the higher the NH ₃ decomposition rate.

On the other hand, the NO decomposition rate shows a maximum value at a reaction temperature of 400 ° C. for any fuel composition, and the lower the H ₂ concentration in the fuel, the higher the NO decomposition rate is in the case of the NH ₃ decomposition rate. Similarly, it tends to be higher. However, at higher reaction temperatures, conversely, the fuel as the NO decomposition ratio of low concentration of H ₂ shows a tendency to decrease. That is, the lower the H ₂ concentration, the narrower the reaction temperature range effective for NO decomposition.

The optimum reaction temperature that maximizes the total decomposition rate of NH ₃ and NO is in the range of 400 to 450 ° C., and the optimum reaction temperature tends to be lower as the H ₂ concentration in the fuel is lower. Yes.

(4.5.2) Influence of NH ₃ concentration FIG. 29 shows the influence of NH ₃ concentration on the decomposition rate of NH ₃ and NO. In the analysis, the NH ₃ concentration is changed under the condition that the NO / NH ₃ molar ratio in the mixed gas is constant at 1, and the NO supply amount is also increased in proportion to the NH ₃ concentration. The other analysis conditions are the reference conditions shown in Table 2.

As the NH ₃ concentration in the gasified fuel increases, the decomposition rate of NH ₃ and NO increases, and when the NH ₃ concentration is 500 ppmv or higher, both show a decomposition rate of 50% or higher. In particular, when the NH ₃ concentration is 1000 ppmv or more, the decomposition rates of NH ₃ and NO are equal.

On the other hand, when the NH ₃ concentration in the fuel becomes a low concentration condition of 500 ppmv or less, the decomposition rate of NH ₃ and NO sharply decreases, and the decomposition rate of NO decreases more greatly than the NH ₃ decomposition rate.

FIG. 30 shows the relationship between the reaction temperature and the decomposition characteristics of NH ₃ and NO, using the NH ₃ concentration in the fuel as a parameter. In either reaction temperature, the higher the NH ₃ decomposition percentage NH ₃ concentration in the fuel is seen to be improved.

On the other hand, the optimum reaction temperature that maximizes the NO decomposition rate shows a tendency to increase slightly as the NH ₃ concentration in the fuel increases, and the higher the NH ₃ concentration, the better the NO decomposition characteristics on the higher temperature side. doing. As a result, the reaction temperature at which the total decomposition rate of NH ₃ and NO is maximized is 400 to 450 ° C. (NH ₃ concentration in fuel = 100 to 1000 ppmv), and rises gradually as the NH ₃ concentration increases. Showed a trend.

(4.6) Effect of Pressure FIG. 31 shows the effect of reaction pressure on the decomposition rate of NH ₃ and NO. In the analysis, only the reaction pressure is changed under the reference conditions shown in Table 2.

Decomposition rate of NH 3, _NO with increasing reaction pressure, the total decomposition ratio of the NH ₃ and NO are reduced substantially the same manner. For example, when the reaction pressure is reduced from 30 atm to 20 atm, the decomposition rate of NH ₃ increases from 54% to 59%, and the decomposition rate of NO increases from 48% to 51%.

(5. Summary)
The basic performance and application conditions of the present invention are shown in Table 3 (Outline of decomposition method of NH _{3 in} gasified fuel and optimization by plant operation conditions), and the outline is described below.

And propose a part of NH ₃ features gasification fuel of the NH ₃ decomposing scheme oxidized to NO, and supplies the NO required for NH ₃ decomposition reaction by the exhaust gas recirculation, to _{N 2} NH ₃ Considering the decomposition of NO and the amount of oxidation as a NO supply source, the NH ₃ decomposition rate can be substantially achieved 87%. As a result, there is no need to procure and supply NO for the installation of flue gas denitration equipment or NH ₃ decomposition.

· To promote the mutual decomposition reaction of NH ₃ and NO at a temperature of conditioning gas turbine for supplying the gas fuels or circulating exhaust gas in the reaction temperature (400 to 600 ° C.). The optimum reaction temperature is 350 ° C to 450 ° C. When various gasified gas fuels are used, the reaction temperature is in the temperature range of 250 ° C to 700 ° C. It is important to adjust the reaction temperature according to the gas mixing ratio (dilution ratio), NO component concentration or O ₂ component concentration in the exhaust gas circulation, combustible component in the gasified fuel, or NH ₃ concentration.

  The concentration of nitrogen oxides in exhaust gas during plant operation was investigated. In the feedback control that adjusts to maintain the nitrogen oxide concentration in the exhaust gas within a certain range at any time during the rated operation of the plant, control is performed to reduce the fluctuation range. It is thought that the concentration of objects will constantly fluctuate. However, the fluctuation is due to feedback control, and in an actual plant, there is a more gradual fluctuation due to the coal type, plant load, etc., but this is not considered to be caused. Below, the fluctuation | variation by feedback control was examined for the fluctuation | variation when a dilution ratio changes as an example.

For example, when the NH ₃ concentration in the gasified fuel is 500 ppmv, it is considered that the fluctuation in a short time is not large unless the coal type is changed. However, with different gasifier systems, it is considered that the NH ₃ concentration in gasified gas fuel is different even with the same coal type.

  Further, even if the concentration of nitrogen oxides in the exhaust gas varies, it is considered that there will be no particular problem for plant operation.

In FIG. 20 described above, the NO / NH ₃ molar ratio (ratio of the NO molar amount in the exhaust gas and the NH ₃ molar amount in the fuel) fluctuated in the range of 0.5 to 2.0 at the rated temperature condition. As a result of the analysis, the NO / NH ₃ molar ratio converges to 0.71 after about four exhaust circulation cycles. That is, it is understood that the value automatically converges to an appropriate value from the relationship between the decomposition rate of NH ₃ and the circulating molar amount of NO. However, FIG. 20 only considers the case where the NO / NH ₃ molar ratio fluctuates, but in reality, the NO / NH ₃ mol converges due to the influence of the pressure, the composition of the gasified fuel, and the composition of the exhaust gas. The ratio will be determined.

That is, in the range of NO / NH ₃ molar ratio in FIG. 20 = 0.5 to 2.5, DeTFN is about 40 to 53%. In this range, the number of exhaust gas circulations is about 4 to 5, and the NO / NH ₃ molar ratio converges to 0.71.

However, in FIG. 20, all the exhaust gas is supplied to the fuel (exhaust gas / fuel: D / F = 5.54 mol / mol). If the exhaust gas of exhaust gas circulation / fuel = 3 mol / mol is mixed with the fuel, the convergence value is different. FIG. 4 shows the result of the influence of D / F. When calculated by reflecting this, it is considered that the NO / NH ₃ molar ratio is generally converged to 1.07.

Moreover, when it becomes partial load, decomposition | disassembly conditions differ. Generally, when Tex (average gas temperature at the outlet of the combustor 5) = 800 ° C., the NO / NH ₃ molar ratio is considered to converge to 0.87.

From the above, when feedback control is performed, the concentration of nitrogen oxides in the exhaust gas is automatically in the range of NO / NH ₃ molar ratio = 0.7 to 1.1, for example, under rated conditions. It is considered to be adjusted. Further, at the time of partial load, it is considered that the exhaust gas is circulated in its entirety, and is automatically adjusted to the NO / NH ₃ molar ratio range under rated conditions.

As with the case of the feedback control, the pre-adjustment for performing the adjustment for maintaining the concentration of nitrogen oxide in the exhaust gas within a certain range in advance before the rated operation of the plant is similar to that in the feedback control. The concentration of nitrogen oxides automatically converges to a value according to the relationship between the decomposition rate of NH ₃ and the circulating molar amount of NO.

2 Gasification Furnace 3 Gas Purifier 4 Diluent Supply Position 5 Combustor 21 Recycling System 22 Mixed Gas Channel 23 First Flow Rate Control Unit 24 Switching Unit 25 Bypass Channel 26 Second Flow Rate Control Unit

Claims (13)

In a method for operating a thermal power plant in which a gasification gas generated in a gasification furnace is purified by a dry gas purification device and burned in a combustor that performs O ₂ stoichiometric combustion as a fuel gas containing NH ₃ , A part or all of the discharged exhaust gas is recycled and mixed with the fuel gas as a diluent, and before burning in the combustor, nitrogen oxide and O ₂ in the diluent are mixed with NH in the fuel gas. ₃ is decomposed into N ₂ and H ₂ O, and undecomposed NH ₃ is combusted in the combustor to be oxidized into nitrogen oxide, and the NH ₃ decomposition reaction and oxidation reaction are repeated. An operation method for an exhaust gas circulation thermal power plant, wherein the operation is performed while maintaining the concentration of nitrogen oxides in the exhaust gas within a certain range. The exhaust gas circulation thermal power plant according to claim 1, wherein the concentration of nitrogen oxides in the exhaust gas is adjusted by changing the decomposition rate of the NH ₃ by increasing or decreasing the mixing amount of the diluent. how to drive. The exhaust gas circulation thermal power according to claim 1 or 2, wherein the concentration of nitrogen oxides in the exhaust gas is adjusted by changing the decomposition rate of the NH ₃ by increasing or decreasing the reaction time of the decomposition reaction. How to operate the power plant. 4. The concentration of nitrogen oxides in the exhaust gas is adjusted by changing a decomposition rate of the NH ₃ by raising or lowering a reaction temperature of the decomposition reaction. 5. Operation method of exhaust gas circulation type thermal power plant. A part or all of an oxidant supplied to the combustor is mixed with the fuel gas, and a nitrogen oxide concentration in the exhaust gas is adjusted by changing a decomposition rate of the NH _3. Item 5. A method for operating an exhaust gas circulation thermal power plant according to any one of Items 1 to 4.   The operation method of the exhaust gas circulation thermal power plant according to any one of claims 2 to 5, wherein a rated operation is performed after the adjustment.   3. The nitrogen oxide concentration in the exhaust gas is measured while performing a rated operation, and the rated operation is performed while performing the adjustment so that the measured value becomes a predetermined target value. 5. An operation method of the exhaust gas circulation thermal power plant according to claim 5. The temperature of the mixed gas obtained by mixing the diluent with the fuel gas is set to 300 to 600 ° C to promote the decomposition reaction of the NH ₃ and then supplied to the combustor. The operation method of the exhaust gas circulation type thermal power plant as described in any one. In a thermal power plant in which a gasification gas generated in a gasification furnace is purified by a dry gas purification apparatus and burned in a combustor that performs O ₂ stoichiometric combustion as a fuel gas containing NH ₃ , the gas is discharged from the combustor A recycle system that recycles a part or all of the exhaust gas and mixes it with the fuel gas as a diluent, the fuel gas mixed with the diluent, NH ₃ in the fuel gas, nitrogen in the diluent A mixed gas flow path is provided which is conveyed while being decomposed into N ₂ and H ₂ O by oxides and O ₂ , and the combustor burns NH ₃ remaining in the fuel gas to generate nitrogen oxides in is intended to oxidize, the diluent nitrogen oxides of the exhaust gas is Kaee decomposition reaction and the oxidation reaction and is repeated in the NH ₃ by mixing the fuel gas by the recycled system Exhaust gas circulation thermal power plant, characterized in that the concentration is maintained within a certain range.   The exhaust gas circulation thermal power plant according to claim 9, further comprising a switching unit that provides a plurality of supply positions of the diluent to the fuel gas and switches the supply position to be used.   The exhaust gas circulation thermal power plant according to claim 9 or 10, further comprising first flow rate adjusting means for increasing or decreasing the supply amount of the diluent.   A bypass passage for mixing a part or all of the oxidant supplied to the combustor with the fuel gas, and a second flow rate adjusting means for increasing or decreasing the supply amount of the oxidant mixed with the fuel gas; The exhaust gas circulation thermal power plant according to any one of claims 9 to 11,   The exhaust gas circulation thermal power plant according to any one of claims 9 to 12, wherein the mixed gas flow path has a portion for setting the temperature of the mixed gas to 300 to 600 ° C.

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