JPS606392B2 - High-temperature, high-pressure gas purification method and device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a technology for refining coal gas, and more particularly to a technology for decomposing and removing ammonia contained in coal gas, and more specifically, a method for refining coal gas in which ammonia is removed together with hydrogen sulfide. Regarding gas purification technology.

BACKGROUND ART The technology of synthesizing gaseous fuels consisting of hydrogen, carbon monoxide, methane, etc. by gasifying fossil fuels has been known for a long time.

In recent years, the use of coal as an energy source in place of oil has been reaffirmed, and power generation systems using coal as a fuel source are being considered. However, in a power generation system using coal as a fuel source, it is economical and thermally efficient to burn the high-temperature gaseous fuel synthesized by coal gasification at a high temperature without lowering the temperature and operate the gas turbine pin. It is considered an essential condition for process configuration. However, the problem here is that sulfur and nitrogen, which are naturally included in fossil fuels such as coal, turn into hydrogen sulfide and ammonia, respectively, during gasification, and the gaseous fuel after gasification contains 100% of each. The point is that it is contained in a concentration of several percent from blood increase. Hydrogen sulfide is an extremely corrosive gas and is a serious source of pollution, and ammonia, which becomes nitrogen oxide when gasified fuel is burned, is also a serious source of pollution. Therefore, in order to protect the equipment, it is essential to remove hydrogen sulfide as early as possible, and it is required to remove hydrogen sulfide as soon as possible after gaseous fuel is produced by gasification and before combustion. On the other hand, the same can be said for ammonia; it is technically difficult to perform denitrification at the stage when it becomes NOk after gaseous combustion because the denitration load is extremely high, and it is necessary to decompose and remove it before combustion. Become. From the above points, it is essential to remove and decompose hydrogen sulfide and ammonia before combustion, and the development of technology to remove hydrogen sulfide and ammonia at high temperatures will contribute to the success of power generation systems using coal as a fuel source. It has been requested as a key. There are many examples in which the removal of hydrogen sulfide from high-temperature gases is required, not only for synthetic fuels made from coal, but it is generally considered to be an extremely difficult technology. Conventionally, a dry method using a solid removal agent formed into granules has been considered effective as a method for removing hydrogen sulfide from gas at high temperatures.
Methods using calcium carbonate, dolomite, iron oxide, etc. as removal agents are known. Among these removers, iron oxide is said to be the best in terms of hydrogen sulfide removal rate, ease of recycling of the remover whose activity has deteriorated, and economical efficiency. Iron oxide reacts with hydrogen sulfide at high temperatures (
1} Prepare iron sulfide as shown in the formula.

Fe203 12 days x 10 days 2 → eS+3 days 20 (1) Since iron oxide once converted to iron sulfide loses its ability to remove hydrogen sulfide, it is required to regenerate it to restore its removal ability.

A method for regenerating iron oxide is to contact iron sulfide with air or a gas mixture of air and water vapor, and return it to iron oxide with the by-product of sulfur dioxide gas or hydrogen sulfide, as shown in the Ushio method. ing. Misaki eS+702 one is e
203 14S02 {2- is eS+9 days 20 → Fe203 12 days 2S+ ratio (3-However, the removal reaction m of hydrogen sulfide by iron oxide is an exothermic reaction, so when the removal reaction temperature increases, the remaining hydrogen sulfide due to the reaction equilibrium Since the concentration increases, it is necessary to control the temperature to an appropriate level in terms of the allowable residual concentration of hydrogen sulfide.

Figure 1 demonstrates the temperature dependence of the above-mentioned hydrogen sulfide removal reaction using iron oxide, and shows that when coal gas having the composition shown in Table 1 is brought into contact with an absorbent containing iron oxide at various temperatures. This shows the actual concentration of residual hydrogen sulfide.

The coal gas leaving the coal gasifier is usually 800~900oo
However, at such high temperatures, a considerable concentration of hydrogen sulfide remains, and in order to suppress the remaining hydrogen sulfide to about 50 degrees, it is necessary to carry out the desulfurization reaction at about 65 to 0. Table 1 On the other hand, various catalysts are generally considered for the decomposition of ammonia. Effective catalysts are severely limited.

A granular catalyst containing iron in the form of reduced iron has been considered as an extremely effective catalyst for the decomposition of ammonia in coal gas, and ammonia is decomposed as shown in the following equation. 2NH3F Toru N2 100% 2 {4} are 12NH3 1 is exN + Chihito 2
■2FexN→2Fe+N2
'6} Since the ammonia decomposition reaction represented by the above formula is an endothermic reaction, the higher the decomposition temperature, the lower the concentration of ammonia remaining in the reaction equilibrium.

Therefore, the higher the temperature, the more preferable the ammonia decomposition reaction is, contrary to the hydrogen sulfide removal reaction. On the other hand, the ammonia decomposition reaction represented by the formula {4} is a reaction in which two molecules of ammonia are converted into one
A total of 4 gas molecules (nitrogen molecules and 3 molecules of hydrogen) are generated, and the number of molecules increases with the reaction, so the higher the pressure at which the ammonia decomposition reaction takes place, the higher the concentration of ammonia remaining in the reaction equilibrium. It gets expensive.

Figure 2 shows the reaction equilibrium when ammonia is decomposed by bringing the coal gas shown in Table 2 into contact with a catalyst containing iron in the reduced iron state under various pressures and temperatures. This shows the concentration of ammonia remaining above.

The effects of temperature and pressure on the aforementioned ammonia decomposition are clearly demonstrated. Gasification of 10,000 coal, etc. increases the calorific efficiency, which is expressed as the ratio of the amount of heat generated when raw coal is directly combusted and the amount of heat generated when the gaseous fuel produced by gasification is combusted. It is required to increase the pressure of conversion as high as possible, and it is usually operated at around 20k9/m.

However, in order to prevent ammonia decomposition from being affected by hydrogen sulfide, it is necessary to desulfurize coal gas before ammonia decomposition, and in order to perform desulfurization with a sufficient removal rate,
The desulfurization reaction must be carried out at about ℃. At this time, the reaction conditions for ammonia decomposition following desulfurization are a high pressure of 20k9/m and a temperature of 650oO. When ammonia is decomposed under such conditions, the remaining ammonia has a significantly high concentration of about 81 yen, as can be seen from point 2 on curve 1 in FIG. As mentioned above, when hydrogen sulfide and ammonia in coal gas under high temperature and high pressure are removed and decomposed using an iron oxide absorbent and a catalyst containing iron in the reduced iron state, sulfur Due to the conflicting temperature dependencies of the hydrogen removal reaction and the ammonia decomposition reaction, there was a technical difficulty in being unable to remove both with satisfactory performance. The present invention has been made in view of the above points, and its purpose is to provide a means for purifying coal gas that can decompose and remove ammonia contained in coal gas with sufficiently high efficiency. .

The present invention was made through detailed research on the removal reaction of hydrogen sulfide and ammonia in high-temperature coal gas and comprehensive consideration on coal gasification power generation systems. This method is carried out under conditions that allow for the most effective operation of gas turbines through combustion, and by removing part of the sensible heat of high-temperature, high-pressure coal gas produced by coal gasification, the temperature can be reduced to iron oxide-based gas. The temperature is controlled at a temperature that allows hydrogen sulfide removal reaction using a removing agent, and after removing hydrogen sulfide through contact with an iron oxide-based removing agent, the coal gas is expanded to reduce the force.
This method is characterized in that ammonia is decomposed by contacting the expanded coal gas with a catalyst containing iron in the form of reduced iron.

The present invention will be explained below using specific examples.

FIG. 3 shows one embodiment of the present invention and is a flow sheet of a process for removing hydrogen sulfide and ammonia from coal gas. In FIG. 3, coal gas 2 produced by gasifying coal 1 in a gasification furnace 21 is cooled in a heat exchanger 22 to become coal gas 3 at a temperature suitable for hydrogen sulfide removal reaction and enters a desulfurization reactor 23. The desulfurization reaction device 23 is filled with an absorbent made of iron oxide or an absorbent containing iron oxide, and removes hydrogen sulfide in the coal gas as iron sulfide. The coal gas 4 from which hydrogen sulfide has been removed is sent to an expansion turbine 24
It enters the coal gas and expands into low pressure coal gas 5. At this time, the work caused by the expansion of the coal gas is extracted as electric power by the expansion turbine. The coal gas 5 whose pressure has decreased is transferred to a heat exchanger 22
The coal gas 2 absorbs the sensible heat of the high temperature coal gas 2 and is heated to become a high temperature coal gas 6 again and enters the ammonia decomposition reactor 25. The ammonia decomposition reactor 25 is filled with catalyst particles containing iron in the state of reduced iron, and decomposes ammonia in the coal gas into nitrogen and hydrogen. Coal gas 6 in which ammonia has been decomposed is sent as clean gas 8 to a combustor 26 of a gas turbine, where it is combusted by air 12 to become high-temperature, high-pressure gas 10, which moves a gas star pin 27 to become high-temperature exhaust gas 11. The exhaust gas 11 is normally sent to a waste heat boiler for waste heat recovery treatment. Next, a detailed explanation of the process according to the present invention will be given using an example of actual measurement data obtained when coal gas is actually passed through the process shown in FIG.

The coal gas 2 coming out of the gasifier 21 is pressurized to 20 k9/h at a high temperature of 80,000 ml, and has the composition shown in Table 1.

When the high-temperature, high-pressure coal gas 3 is passed through the desulfurization reactor 23 filled with an absorbent containing iron oxide, residual coal gas 4 remains in the desulfurized coal gas 4 depending on the temperature of the coal gas 2, as shown in FIG. Since the hydrogen sulfide concentration changes, the coal gas 2 is cooled in the heat exchanger 22 to reduce the temperature of the coal gas 3 to 650q.
By controlling the temperature to 0, a desulfurization rate of 99% could be achieved. The coal gas 4 that came out of the desulfurization reactor 23 had a temperature of 65,300 ℃ with a slight increase in temperature because the reaction between hydrogen sulfide and iron oxide was an exothermic reaction. When the coal gas 4 is expanded by the expansion turbine 24, a slight temperature drop occurs along with a pressure drop. This temperature drop is determined by the rate of expansion from coal gas 4 to 5 in expansion turbine 24. Therefore, the temperature of the coal gas 6 obtained by passing the expanded coal gas 5 through a heat exchanger and heating it by the sensible heat of the coal gas 2 is as follows.
It is determined by the expansion rate in the expansion turbine 24. Furthermore,
Since the ammonia decomposition reaction is controlled by both the temperature and pressure of the coal gas 6, when the coal gas 6 is passed through the ammonia decomposition reactor 23 filled with a catalyst containing iron in the reduced iron state, it is decomposed in reaction equilibrium. The concentration of ammonia remaining in the coal gas 8 without being removed is a value determined by the expansion rate from the coal gas 4 to the coal gas 5 in the expansion turbine 24. Therefore, Table 2 shows how to change the expansion rate when expanding coal gas 4 to coal gas 5 in expansion turbine 24,
The pressure and temperature of coal gases 5, 6, and 8 and the ammonia concentration remaining in coal gas 8 are measured and shown. As shown in Table 2, the residual ammonia concentration was all kept at a low concentration of 300 feet or less when the expansion coefficient was between 1.3 and 4.

The operation of the present invention can be clearly explained based on FIG. In Fig. 2, 1 is a curve showing the relationship between ammonia decomposition temperature and residual concentration when the pressure is 20 kg/equal, where 01 to 15 k9/swim, m 10 k9/lump, and W 7.
5k9/mass, V shows the relationship between 5k9/earth 2 o'clock. The ○ points in Figure 2 indicate the gasifier outlet conditions (20k9/carp,
It shows the ammonia concentration remaining when ammonia decomposition is performed at 800q○). However, according to the conventional technology, since the pressure of 20k9/lump must be cooled to an appropriate temperature for desulfurization, the change follows curve 1 in Figure 2, and 80,000 coal gas is converted to 65 k9 required for desulfurization.
When cooled to the ■ point of 000, the residual ammonia concentration becomes 8.
The concentration is as high as 10 willows. On the other hand, according to the present invention, the pressure and temperature are lowered by adiabatically expanding the coal gas to perform work, and by exchanging sensible heat between the coal gases, the coal gas entering the desulfurization reactor is desulfurized. The residual concentration of ammonia varies from 1 to 0, m, W, V in Fig. 2 because the gas entering the ammonia decomposition reactor is heated to a high temperature suitable for ammonia decomposition while cooling to the temperature used for the reaction at 650q0. There is a change to the curve, and the residual ammonia concentration becomes determined by the points ■, ■, ■, ■ corresponding to each condition No. in Table 2. At each point, the deviation is less than 30 degrees, and about one-third of the ammonia 1 remains compared to the conventional method shown by ■. The fourth is a process flow sheet showing another embodiment of the present invention.

The difference from the embodiment of the present invention shown in FIG. 3 is that air 9 is mixed into the coal gas 6 which has been heated and heated by the sensible heat of the coal gas after desulfurization, and the coal gas 6 is heated through three oxidation temperature risers. A part of the combustible gas contained in the ammonia decomposition reactor 25 is oxidized and burned to raise its temperature, and is then fed into the ammonia decomposition reactor 25 as gas 7 under more favorable temperature conditions for ammonia decomposition. The amount of air 9 added to the coal gas 6 is adjusted according to the temperature of the coal gas 6 and the ammonia decomposition temperature, and is within a range that satisfies the minimum required value of the combustible gas ratio when burned in the combustor 26 after ammonia decomposition. limited to. Table 3 shows the results of the decomposition of ammonia by adding adjusted air to the coal gas 6 obtained under the pressure-reducing conditions in each expansion turbine shown in Table 2 and raising the temperature to a gasifier outlet temperature of 800 qo. The result shows the combustion rate of the combustible gas in the coal gas 6 and the ammonia concentration remaining in the outlet gas 8 of the ammonia decomposition reactor 25.

Table 4 From Table 4, the effect of increasing the temperature by adding air to coal gas is remarkable, and by using only less than 6% of combustible gas, the residual concentration of ammonia can be reduced to about 7. It can be seen that it is possible to lower the skin level.

The residual ammonia concentration can be further reduced by increasing the utilization rate of combustible gas, that is, the combustion rate as much as possible. On the other hand, even if combustible gas is burned before the combustor 26, there is no heat loss as all of the combustion heat is used to increase the sensible heat of the coal gas, and it goes without saying that this does not change the thermal efficiency of the entire power generation system. . A specific numerical example of the embodiment of the present invention described above is as follows: A desulfurization reaction device is filled with a desulfurization catalyst in which iron oxide is supported on alumina, and the alumina-supported iron oxide is reduced with hydrogen in an ammonia decomposition reactor, and the iron content is converted into reduced iron. This data was obtained when the reactor was operated with an ammonia decomposition reaction catalyst packed in the state.

In addition, in the above embodiment, only the data was shown when the pressure was reduced to 5k9/kg, but this is different from the compression ratio and compression efficiency of the air 12 sent to the coal-gas combustor 26, and the expansion ratio and efficiency of the gas turbine 27. This is based on the fact that it is not very desirable to reduce the pressure to less than about 5 kg/cm in view of the correlation and the relationship with the ammonia decomposition reaction temperature.

According to the embodiment of the present invention shown in FIG. 3, hydrogen sulfide and ammonia can be removed and decomposed from high-temperature gas with high efficiency by effectively controlling the pressure and temperature of coal gas. Since the pressure reduction of coal gas can be directly converted into electrical energy, it is possible to operate a high-temperature gas purification process with high efficiency.

According to another embodiment of the present invention shown in FIG.
In addition to the effects of the embodiment of the present invention shown in FIG. 3, it is possible to provide a process that complies with stricter ammonia residual concentration regulations, and to operate a high-temperature gas purification process with extremely high purification efficiency and thermal efficiency. be.

In addition, in the embodiment of the present invention shown in FIGS. 3 and 4, a fixed bed type reactor is applied as the desulfurization reactor 23, and only the desulfurization reactor is shown, but in reality, it is combined with a regeneration reactor. It is designed to perform switching operation for desulfurization and regeneration.

Furthermore, it is of course possible to use a fluidized bed type reactor as the desulfurization reactor and the regeneration reactor to perform the desulfurization reaction and the regeneration reaction continuously. If necessary, an ammonia decomposition reactor may also be combined with a regeneration reactor. The work done by the expansion turbine can also be converted into mechanical energy other than electrical energy. The effect of the present invention is that the removal of sulfides such as hydrogen sulfide and the decomposition of nitrides such as ammonia contained in real gas such as high-temperature coal gas can be performed with high efficiency in succession. The effect of purifying and refining high-temperature real gas containing impurities such as coal gas and converting it into harmless fuel gas with high efficiency can be achieved.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the relationship between desulfurization reaction temperature and residual hydrogen sulfide concentration, Fig. 2 is a diagram showing the relationship between ammonia decomposition pressure, temperature, and residual ammonia concentration, and Fig. 3 is a diagram showing the relationship between desulfurization reaction temperature and residual hydrogen sulfide concentration. A system diagram of a coal gasification power generation system equipped with a high-temperature, high-pressure gas purification device, which is one embodiment, and FIG. 4 is a system diagram of a coal gasification power generation system equipped with a high-temperature, high-pressure gas purification device, which is another embodiment of the present invention. This is a system diagram of 2... Coal gas, 7... Clean gas, 21... Gasifier, 22... Heat exchanger, 23... Desulfurization reactor, 24.
... expansion turbine, 25 ... ammonia decomposition reactor,
26...Combustor, 27...Gas turbine. Kaya Figure 2 Tsutomu Figure 3 Grandson Figure 4

Claims (1)

[Claims] 1. In a method for producing high-temperature, high-pressure gas that sequentially removes and decomposes sulfides such as hydrogen sulfide and nitrogen compounds such as ammonia contained in high-temperature, high-pressure gas, The sulfides in the high-temperature, high-pressure gas are removed by a catalyst containing iron oxide, and the high-temperature, high-pressure gas is then heated to a temperature suitable for a nitrogen compound decomposition reaction after pressure reduction, and the sulfides are removed from the high-temperature, high-pressure gas. 1. A method for purifying high-temperature, high-pressure gas, which comprises decomposing nitrogen compounds using a catalyst containing iron in a reduced iron state under a temperature condition higher than that temperature and a pressure condition lower than the sulfide removal pressure. 2. The method for producing and refining high-temperature, high-pressure gas according to claim 1, characterized in that the temperature at which the sulfide is removed is adjusted so that the concentration of hydrogen sulfide remaining in the high-temperature, high-pressure gas is approximately 250 ppm or less. 3. The method for purifying high-temperature, high-pressure gas according to claim 1, wherein the pressure condition is a pressure not less than about 5 kg/cm^2. 4. The high-temperature, high-pressure gas according to claim 1, 2, or 3, characterized in that the high-temperature, high-pressure gas after sulfide removal is passed through an expansion means to lower the pressure to the above-mentioned pressure conditions. Purification method. 5. The method for purifying high-temperature, high-pressure gas according to claim 1, 2, 3, or 4, characterized in that the pressure effect of the high-temperature, high-pressure gas by the expansion means is converted into power. 6. After the sulfide is removed and after the pressure is lowered, the high-temperature gas is brought to a temperature more favorable for the subsequent decomposition of nitrogen compounds by giving the sensible heat of the high-temperature, high-pressure gas before the sulfide removal. A method for purifying high-temperature, high-pressure gas according to claim 1, 2, 3, 4, or 5, characterized in that the temperature of the high-pressure gas is adjusted. 7. The high-temperature high-pressure gas after the sulfide removal and after the pressure drop is adjusted to a temperature more favorable for ammonia decomposition due to the sensible heat of the high-temperature high-pressure gas before the sulfide removal,
A part of the combustible gas is oxidized and burned by adding air, and the temperature of the high-temperature high-pressure gas heated by the sensible heat of the high-temperature high-pressure gas is raised to a temperature more favorable for ammonia decomposition. A method for purifying high-temperature, high-pressure gas according to claim 1, 2, 3, 4, 5, or 6. 8 A sulfide removal reaction device having a catalyst containing iron oxide that removes sulfide from high-temperature, high-pressure gas, and reduced iron that decomposes and removes nitrogen compounds from the high-temperature, high-pressure gas from which sulfides have been removed in the sulfide removal reaction device. a nitrogen compound decomposition reaction device having a catalyst containing iron in a state of A heat exchanger is installed to give the sensible heat of the high-temperature, high-pressure gas before sulfide removal to the subsequent high-temperature, high-pressure gas, and the high-temperature, high-pressure gas, which has been reduced in pressure and temperature by the pressure reduction device and the heat exchanger, is transferred to the nitrogen compound decomposition reaction device. A high-temperature, high-pressure gas purification device characterized in that the gas is guided to 9. Claim 8, further comprising an addition device for adding air to the high-temperature, high-pressure gas exiting the heat exchanger.
The high-temperature, high-pressure gas purification device described in Section 1. 10. The high-temperature, high-pressure gas purification device according to claim 9, wherein the addition device oxidizes and burns the combustible gas of the high-temperature, high-pressure gas with the added air. 11. Claim 8, 9, or 10, characterized in that an expansion turbine is used as the pressure reducing device.
The high-temperature, high-pressure gas purification device described in Section 1.