JP2870243B2 - Coal gasification plant and its operation method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coal gasification plant and, more particularly, to a coal gasification plant which generates a small amount of nitrogen oxides (hereinafter referred to as NOx) at startup and a method of operating the same.

[0002]

2. Description of the Related Art Coal gasification plants have attracted attention because coal having the largest reserves as a fossil fuel can be efficiently used for power generation. This plant is clean because it gasifies coal and performs desulfurization treatment.It is highly efficient as a power generation plant because it uses gasified fuel in a gas turbine. There is an excellent effect that the generation of NOx during combustion is small.

[0003] Many proposals have already been made for this coal gasification plant. For example, in Japanese Patent Application Laid-Open No. 3-43608, an auxiliary combustion device is provided in a coal gasification furnace, and the auxiliary combustion device is used at the time of startup. It is known that a coal gasifier is heated to a temperature allowed for a coal gasification reaction and is started up to a point where the coal gasifier can be operated by itself.

[0004]

In a normal operation state of a coal gasification plant, the gasification fuel generated in the coal gasification furnace is used as a gas turbine fuel as described above. Since it is low in calories, it has an excellent effect that NOx is less generated during combustion in a gas turbine.

On the other hand, in the above-mentioned Japanese Patent Application Laid-Open No. 3-43608, an auxiliary combustor is used at the time of startup.
The occurrence of x must also be at a sufficiently low level.

Here, the relationship between fuel combustion and NOx, and measures to reduce the amount of external emission of NOx are examined. The NOx includes fuel NOx formed by the reaction of nitrogen contained in fuel with oxygen, and air NO. It is divided into thermal NOx formed by the reaction of nitrogen inside with oxygen. NOx
In order to reduce the amount of external emission of NOx, there are a method of suppressing the generation of NOx and a method of separating the generated NOx into nitrogen and oxygen.

[0007] Of these, the latter method, in which generated NOx is separated into nitrogen and oxygen, is examined first, and is difficult to apply to a coal gasification plant using an auxiliary combustor at the time of startup. The reason is that the primary purpose is to use the high-temperature gas obtained by combustion in the auxiliary combustor for heating various parts of the coal gasification plant. Lower than the reaction temperature of the denitration catalyst to be separated. There is a system in which a second auxiliary combustor is provided at the inlet of the denitration catalyst reactor to heat the gas to the reaction temperature of the denitration catalyst, but this is not advisable.
For this reason, it is effective to take a countermeasure by a method of suppressing the generation of NOx.

Considering the method of suppressing the generation of NOx, the generation of fuel NOx can be prevented by using a fuel containing as little nitrogen as possible. On the other hand, thermal NO
It is known that x generally has a higher combustion temperature, and the higher the pressure, the greater the amount of x generated.

By the way, in a coal gasifier, coal is used as a gasification fuel by using coal and an oxidizing agent. In this case, there are two types, one using air as an oxidizing agent and the other using oxygen as an oxidizing agent. Yes. In the former case, the coal gasifier has air supply equipment for gasification as a necessary equipment, so that air can be used as an auxiliary fuel oxidizer using this equipment. . On the other hand, in order to shorten the startup time, the auxiliary fuel combustion temperature must be increased, and when the combustion temperature is increased, another problem occurs that the amount of generated thermal NOx increases.

On the other hand, in a coal gasifier using oxygen as an oxidizing agent, no thermal NOx is generated. However, when oxygen is also supplied to the auxiliary combustor for combustion, the flame may approach the fuel nozzle that supplies the fuel at a high burning speed and burn the fuel nozzle. If the gas leaks into the gasification furnace, the gasification furnace may be burned. In addition, in a coal gasifier using oxygen as a gasifying agent, a new installation of an air supply facility is required to use air as an oxidizing agent for auxiliary fuel.

In view of the above, an object of the present invention is to provide a coal gasification plant capable of reducing NOx when using auxiliary fuel, and a method of operating the same.

Another object of the present invention is to provide a coal gasification plant capable of effectively utilizing combustion exhaust gas when using auxiliary fuel, and a method of operating the same.

[0013]

SUMMARY OF THE INVENTION The object of the present invention is to focus on the fact that gasified fuel in a coal gasifier is not used at the time of startup, and to remove inert gas other than nitrogen, such as carbon dioxide, contained in the gasified fuel. This is achieved by extracting and feeding mixed with oxygen to the auxiliary combustor. Further, the above object is achieved by storing and using carbon dioxide separated from flue gas at the time of auxiliary fuel combustion in a coal gasifier.

[0014]

When an inert gas other than oxygen and nitrogen, such as carbon dioxide, is used as an oxidizing agent for the auxiliary fuel of a coal gasifier,
The burning rate is lower than when pure oxygen is used as the oxidizing agent. For example, 50% diluted with carbon dioxide
When oxygen having an oxygen concentration is used, the combustion speed is reduced to 1/4 or less, and burning of the fuel nozzle can be prevented. Moreover, even if the oxidizing agent leaks into the gasification furnace, there is no risk of burning. Further, since high oxygen concentration combustion can be provided, even if nitrogen is contained, generation of nitric oxide, which is a cause of global warming, can be eliminated.

In a coal gasification plant using oxygen as a gasifying agent, by using a hydrocarbon fuel such as light oil as an auxiliary fuel, the exhaust gas components of the auxiliary fuel become carbon dioxide, water vapor, and excess oxygen. This auxiliary fuel combustion gas can separate water vapor by cooling to obtain carbon dioxide gas, which can be used not only for diluting oxygen as an oxidizing agent but also for increasing the critical pressure to about 76 atmospheres or more. By pressurizing, it can be stored as liquefied carbon dioxide in a pressure vessel, and can be used when necessary.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to FIG.

The coal gasification power generation system is a coal gasification system A
, A gas turbine device B, and a gas turbine exhaust heat utilization system C. The present invention mainly relates to the coal gasification system.

First, the coal gasification system A will be described. Fuel is supplied from the coal supply pipe 52 and the auxiliary fuel supply pipe 51 to the coal gasifier 5 of the coal gasification system A,
An oxidant is supplied from the air separation device 10. An air compressor 12 is connected to an input side of the air separation device 10, and an oxygen compressor 11 and an oxygen mixing device 13 are installed at an outlet side of the air separation device 10. A mixed gas of an inert gas other than nitrogen is supplied to the coal gasifier 5. At the outlet of the gasification furnace 5, a crude fuel gas pipe 5
3 is connected to a crude fuel gas heat recovery boiler 6, an evaporator 38 is installed in the gasification furnace 5, and an evaporator 39, an economizer 36 and a superheater 40 are installed in the crude fuel gas heat recovery boiler 6. You. These economizers 36,
Water supplied in this order to the evaporators 38, 39 and the superheater 40 is supplied from a gas turbine exhaust heat utilization system C, which cools the crude fuel gas in the gasification furnace 5 and the crude fuel gas pipe 53. I do. 37 is an evaporator 38,
The steam generated by this heat exchange is used in a gas turbine exhaust heat utilization system C. The pipe from the crude fuel gas heat recovery boiler 40 outlet is connected to the gas purification device 8 through the gas-gas heat exchanger 7. By the heat exchange in the crude fuel gas heat recovery boiler 6, the temperature of the crude fuel gas supplied to the gas purification device 8 is set to a temperature suitable for processing in the gas purification device 8. The pipe from the gas purification device 8 is again connected to the gas = gas heat exchanger 7
Through the fuel gas supply pipe 111 and the fuel gas control valve 113
Is connected to the combustor 2 of the gas turbine device B via A pipe from the gas purification device 8 to the sulfur recovery device 9 is also connected.

The gas turbine apparatus B includes a compressor 1 for compressing air 50, a combustor 2 for supplying compressed air and a purified gas from the coal gasification system A to perform combustion, and a combustor 2
And a generator 4 driven by the gas turbine 3.

Finally, the gas turbine exhaust heat utilization system C will be described. The flue gas pipe 55 from the gas turbine 3
The exhaust heat recovery boiler 14 is connected. The exhaust heat recovery boiler 14 includes a low-pressure economizer 30, a low-pressure drum 31, a low-pressure evaporator 32, a high-pressure economizer 33, and a high-pressure drum 3.
4, a high-pressure evaporator 35, a superheater 45, a reheater 46, a pressure pump 23 and the like. The steam turbine system includes a high-pressure steam turbine 15, a reheat steam turbine 16, a low-pressure turbine 17, a steam turbine generator 18, a condenser 19, and a feedwater pump 20. Water supply line 5 from condenser 19
7 is connected to a low-pressure economizer 30 in the exhaust heat recovery boiler 14 through a water supply pump 20. The outlet of the low-pressure economizer 30 is connected to the low-pressure drum 31 and also to the pressurizing pump 23 at the same time. The piping at the outlet of the pressure pump 23 is connected to a high-pressure economizer 33 and is connected to a high-pressure drum 34. Further, a pipe is provided from the outlet of the pressure pump 23 to the economizer 36 of the crude fuel gas heat recovery boiler 6. The low-pressure drum 31 has a low-pressure evaporator 32, and the high-pressure drum 34 has a high-pressure evaporator 35. The high-pressure drum 34 is connected to a superheater 45, and a pipe from the superheater 40 of the crude fuel gas heat recovery boiler 6 is connected in the middle of the superheater. The pipe from the superheater 45 in the exhaust heat recovery boiler 14 is connected to the high pressure steam turbine 15, and the pipe is connected from the outlet of the high pressure steam turbine 15 to the reheater 46 in the exhaust heat recovery boiler 14. In addition, a pipe from the low-pressure drum 31 is also connected to the same pipe. From the outlet of the reheater 46, a pipe is connected to the reheat steam turbine 16, and from the outlet of the reheat steam turbine 16, the low pressure turbine 17 is connected.
The pipeline is connected to the condenser 19 from the outlet of the low-pressure steam turbine 17. Steam turbine generator 18
Are connected to a high-pressure steam turbine 15, a reheat steam turbine 16, and a low-pressure steam turbine 17.

Conventionally known coal gasification power plants are:
It is configured as outlined above, and in the device of the present invention,
A combustion gas recycle pipe 114 is installed from the middle of the fuel gas supply pipe 111 to the oxygen mixing device 13 via a combustion gas recycle control valve 112, a combustion gas separation device 116, and a combustion gas recycle compressor 115.
16 is characterized in that an exhaust gas pipe 119, a drain pipe 118, and a cooling water pipe 117 are provided.

Hereinafter, the operation of the embodiment of FIG. 1 particularly during the steady operation of the coal gasification system A will be described.

Air compressed by the air compressor 12 to about 6 atm is supplied to the air separation device 10. The air compressor 12 is generally a compressor having an intercooler to reduce the compression power. This high pressure air is supplied to the air separation device 10.
At the outlet of the air separation unit 10, oxygen and nitrogen at normal pressure are obtained. The oxygen is supplied to the oxygen compressor 11
After the pressure is increased to about 35 atm by the gas supply to the coal gasifier 5 as a gasifying agent,
The coal supplied from 2 is gasified to produce a crude gas.

During normal operation, the combustion gas recycle control valve 112 is closed, no fuel gas flows to the combustion gas recycle pipe 114, and oxygen produced by the air separation device 10 as an oxidant is supplied to the coal gasification furnace 5. The pressure is increased by the oxygen compressor 11 and supplied.

Next, the operation at the time of startup will be described.
When the coal gasification furnace 5 is started, the temperature of the coal gasification system is almost at room temperature, and it is necessary to raise the temperature to a temperature at which the gasification reaction can be performed in the coal gasification furnace 5.

In this embodiment, the air separation device 10 is started first, and after the pressure of the coal gasification system is increased, the air separation device 10 is started.
Is supplied to the coal gasifier 5 to burn hydrocarbon-based auxiliary fuel such as light oil supplied from the auxiliary fuel supply pipe 51. The combustion gas obtained by burning the auxiliary fuel flows through the fuel gas supply pipe 111. At this time, the fuel gas control valve 113 is closed, and the combustion gas recycle control valve 112 is closed.
When the is opened, the combustion gas flows into the combustion gas separation device 116 through the combustion gas recycle control valve 112. In the combustion gas separation device 116, low-temperature cooling water is supplied to the cooling water pipe 117 to lower the temperature of the combustion gas, condense the water vapor in the combustion gas, and discharge the water from the drain pipe 118 as moisture.

The pressure of the coal gasification system A is about 25 atm for supplying gasified fuel to the gas turbine, and the pressure of the combustion gas separation device 116 is considered in consideration of the pressure loss of the fuel gas supply pipe 111 and the like. Assuming that the pressure is 20 atm, by setting the temperature of the combustion gas separator 116 to 100 ° C. or less by the cooling water flowing through the cooling water pipe 117, the partial pressure of steam in the combustion gas becomes 1 atm or less, and the concentration is 95% or more. Carbon dioxide gas can be obtained. After the pressure of the carbon dioxide gas is increased by the combustion gas recycle compressor 115 through the combustion gas recycle pipe 114, the gas is supplied to the oxygen mixing device 13 to dilute the concentration of oxygen supplied as an oxidant of the auxiliary fuel.

Here, the reason why carbon dioxide gas is mixed and diluted with oxygen as an oxidizing agent of the auxiliary fuel will be described. First, as described above, when oxygen is supplied to the auxiliary combustor for combustion, the combustion speed is high and the flame approaches the fuel nozzle for supplying the fuel, which may burn the fuel nozzle. On the other hand, when oxygen is used as the oxidizing agent, Bernard and Gunser (Ber
nard Lewis, Guenthervon Elbe) Combat, Frame and Explosion of Gasies (C
OMBUSTION, FLAMES and EXPLOSIONS of GASES, ACADEMI
As shown in C PRESS INC., P388, 1961), it is effective to mix an inert gas with oxygen. FIG. 8 is cited from the above-mentioned literature, in which the horizontal axis shows the volume ratio of methane as a fuel, and the mixing rate of oxygen and carbon dioxide is a parameter, and the combustion speed is shown on the vertical axis. In contrast to the case where pure oxygen is used as an oxidizing agent, if the oxygen is diluted with carbon dioxide and 50% oxygen concentration is used, the burning rate is reduced to 1/4 or less, and burning of the fuel nozzle can be prevented. Moreover, even if the oxidizing agent leaks into the gasification furnace, there is no risk of burning.

Excess carbon dioxide and the like in the combustion gas separation device 116 are discharged from the exhaust gas pipe 119 to the outside.
The cooling water of about 100 ° C. can be easily obtained by using the cooling water of the condenser 19 or the boiler water supply.

These operations can be performed not only when the coal gasifier is started but also when the power plant is shut down at night and the auxiliary fuel is burned to keep the temperature of the coal gasifier high. That is clear. According to this embodiment, there is an effect that an inert gas for diluting oxygen can be obtained without installing a special inert gas facility in the power plant.

In a second embodiment of the present invention, steam is used as the inert gas. In the case where a device for generating steam must be provided inside the plant, there is no effect of the present invention, but a steam generation source outside the plant, for example, a coal gasification plant exists in a plurality of lines, and steam is obtained from another line. Where possible, oxygen and water vapor can be used as oxidizers for the auxiliary fuel. According to this embodiment, steam having a high specific heat can be used as a diluent for oxygen,
Since the local increase in the combustion temperature is suppressed, there is an effect of further suppressing the generation of NOx.

A third embodiment of the present invention will be described with reference to FIG. FIG. 2 shows only the parts related to the present invention in the gasification equipment in the coal gasification power generation plant, and the parts of the power generation plant not shown in this figure are the same as those in the embodiment of FIG. Hereinafter, portions different from the embodiment shown in FIG. 1 will be described.

In addition to the combustion gas recycle pipe 114 connected from the combustion gas separation device 116 to the oxygen mixing device 13 via the combustion gas recycle compressor 115, a carbon dioxide control valve 126, a carbon dioxide compressor 121, a carbon dioxide liquefaction Device 122, liquefied carbon dioxide storage device 123, liquefied carbon dioxide supply valve 124, and liquefied carbon dioxide evaporator 12
A pipe line connected to the oxygen mixing device 13 via 5 is provided. During the steady operation, the combustion gas recycle control valve 112 is closed as in the embodiment shown in FIG. 1, and the fuel gas is supplied to the combustor 2 through the fuel gas control valve 113.

At the time of startup, the fuel gas control valve 113 is closed as in the embodiment of FIG.
12 is opened and the combustion gas is supplied to the combustion gas recycle control valve 1
It flows into combustion gas separator 116 through 12. In the combustion gas separation device 116, low-temperature cooling water is supplied to the cooling water pipe 117 to lower the temperature of the combustion gas, condense the water vapor in the combustion gas, and discharge the water from the drain pipe 118 as moisture. The carbon dioxide gas obtained here is supplied to the oxygen mixing device 13 after being pressurized by the combustion gas recycle compressor 115 through the combustion gas recycle pipe 114, and the oxygen concentration supplied as the oxidant of the auxiliary fuel is used for dilution.

On the other hand, surplus carbon dioxide obtained by the combustion gas separation device 116 is boosted in pressure by the carbon dioxide compressor 121 through the carbon dioxide control valve 126, enters the carbon dioxide liquefaction device 122, and is cooled below the liquefaction temperature by the cooling water B 127. Is cooled. If the outlet of the carbon dioxide compressor 121 is at or above the critical pressure of carbon dioxide of about 76 atm, the temperature of the carbon dioxide liquefaction device 122 can be at room temperature without any problem.
At atmospheric pressure, liquefied carbon dioxide can be obtained at 45 ° C. or lower. As described in the embodiment of FIG. 1, the pressure of the combustion gas in the fuel gas supply pipe 111 is about 20 atm. Therefore, in the carbon dioxide compressor 121, the pressure may be increased from this pressure to a predetermined pressure. The carbon dioxide liquefied by the carbon dioxide liquefaction device 122 is sent to and stored in the liquefied carbon dioxide storage device 123. Exhaust gas pipe 119
Is sent to the oxygen mixing device 13 through the combustion gas recycle pipe 114 and the carbon dioxide and carbon dioxide liquefaction device 122
It is used to discharge surplus carbon dioxide other than carbon dioxide liquefied in the above and gas contained in other auxiliary fuel combustion gas.

The liquefied carbon dioxide stored in the liquefied carbon dioxide storage device 123 opens the liquefied carbon dioxide supply valve 124 and burns the liquefied carbon dioxide from the liquefied carbon dioxide storage device 123 when the auxiliary fuel is burned in the early stage of the coal gasification plant startup. The carbon is sent to the liquefied carbon dioxide evaporator 125 through the liquefied carbon dioxide supply valve 124,
By applying heat in step 5, liquefied carbon dioxide is converted into carbon dioxide and sent to the oxygen mixing device 13 to dilute the oxygen sent from the oxygen compressor 11 and use it as an oxidizing agent for the auxiliary fuel.

When the coal gasification plant is stopped, the liquefied carbon dioxide stored in the liquefied carbon dioxide storage device 123 is at a high pressure.
Since it can be supplied to the coal gasification system as carbon dioxide in 25, the coal gasifier 5 can be stopped quickly,
There is an effect that carbon dioxide can be used as a purge gas in a coal gasification plant.

A fourth embodiment of the present invention will be described with reference to FIG. FIG. 3 shows only the parts related to the present invention in the gasification facility in the coal gasification power generation plant as in FIG. 2, and different parts from the embodiment shown in FIG. 2 will be described below.

A carbon dioxide control valve 126 is provided on a pipe from the combustion gas separation device 116 to the carbon dioxide liquefaction device 122, and the liquefied carbon dioxide low temperature storage device 130, the liquefied carbon dioxide supply valve 124,
A pipe is connected to the oxygen mixing device 13 via a liquefied carbon dioxide pump 131 and a liquefied carbon dioxide evaporator 125. Further, a low temperature nitrogen pipe 132 is connected to the liquefied carbon dioxide low temperature storage device 130 and the carbon dioxide liquefaction device 122 from the air separation device 10.

At the time of startup, the fuel gas control valve 113 is closed as in the embodiment of FIG.
2 is opened and the combustion gas is supplied to the combustion gas recycle control valve 11.
2 into the combustion gas separator 116. In the combustion gas separation device 116, low-temperature cooling water is supplied to the cooling water pipe 117 to lower the temperature of the combustion gas, condense the water vapor in the combustion gas, and discharge the water from the drain pipe 118 as moisture.
The carbon dioxide gas obtained here is supplied to the oxygen mixing device 13 after being pressurized by the combustion gas recycling compressor 115 through the combustion gas recycling pipe 114, and the oxygen concentration supplied as an oxidizing agent of the auxiliary fuel is used for dilution.

On the other hand, the excess carbon dioxide obtained by the combustion gas separation device 116 enters the carbon dioxide liquefaction device 122 through the carbon dioxide control valve 126, and is supplied to the low temperature nitrogen supplied from the air separation device 10 through the low temperature nitrogen pipe 132. Is cooled by nitrogen gas.

The carbon dioxide liquefied by the carbon dioxide liquefaction unit 122 is sent to and stored in the liquefied carbon dioxide low-temperature storage unit 130. In the liquefied carbon dioxide low temperature storage device 130, the temperature is kept at 18 ° C. or lower by the low temperature nitrogen gas supplied from the air separation device 10 through the low temperature nitrogen pipe 132. The exhaust gas pipe 119 is a combustion gas recycle pipe 114.
It is used to discharge carbon dioxide sent to the oxygen mixing device 13 through the air, excess carbon dioxide other than carbon dioxide liquefied by the carbon dioxide liquefaction device 122, and other gases contained in the auxiliary fuel combustion gas.

The liquefied carbon dioxide stored in the liquefied carbon dioxide low-temperature storage device 130 is supplied to the liquefied carbon dioxide supply valve 12 when the auxiliary fuel is burned in the early stage of the coal gasification plant startup.
4. Open liquefied carbon dioxide and liquefy carbon dioxide pump 13
The pressure is increased by 1 and sent to the liquefied carbon dioxide evaporator 125, and heat is applied by the liquefied carbon dioxide evaporator 125 to convert the liquefied carbon dioxide to carbon dioxide and send it to the oxygen mixing device 13 to reduce the oxygen sent from the oxygen compressor 11 It can be diluted and used as an oxidizer for auxiliary fuel.

According to this embodiment, the pressure of the liquefied carbon dioxide storage device can be lowered, and simultaneously, the pressure of the carbon dioxide system is increased by liquefied carbon dioxide. The use of a pump has the effect of facilitating the operation of the system. FIG. 4 shows a fifth embodiment of the present invention. The embodiment shown in FIG. 4 is an embodiment of the exhaust gas pipe 1 connected to the combustion gas separation device 116 in addition to the embodiment shown in FIG.
19 is connected to a liquefier exhaust gas pipe 140 from the carbon dioxide liquefier 122. The gas discharged from the carbon dioxide liquefier 122 to the outside through the liquefier exhaust gas pipe 140 is the gas that has not been liquefied in the gas supplied to the carbon dioxide liquefier 122, The water vapor and oxygen remaining in the device 116. In the combustion in the coal gasifier 5, it is necessary to supply more oxygen than is necessary for the combustion of the auxiliary fuel in order to prevent unburned components from being emitted during the combustion of the auxiliary fuel and to lower the combustion temperature. Therefore, surplus residual oxygen is contained in the auxiliary combustion exhaust gas. This oxygen is supplied to the combustion gas separation device 11.
6, the carbon dioxide remains in the carbon dioxide liquefaction device 122 even if it becomes liquefied carbon dioxide, and is discharged outside through the liquefier exhaust gas pipe 140. In the carbon dioxide liquefaction device 122, carbon dioxide, which is a main component of the gas, is removed as liquefied carbon dioxide, so that the concentration of oxygen in the gas discharged out of the system through the liquefier exhaust gas pipe 140 increases. If almost no water vapor is removed by the combustion gas separation device 116, oxygen having a concentration close to 100% can be obtained. The surplus gas of the combustion gas separator 116 as a main component can be supplied from the exhaust gas pipe 119 to the liquefaction apparatus exhaust gas pipe 140, mixed, and discharged outside the system. According to this practical example, there is an effect that a danger such as an explosion due to gas discharged from the coal gasifier system to the outside can be prevented.

FIG. 5 shows a sixth embodiment of the present invention. FIG.
In the embodiment shown in FIG. 2, in addition to the embodiment shown in FIG. 2, a liquefier exhaust gas pipe 140 is connected from the carbon dioxide liquefier 122, and a nitrogen gas pipe 150 is connected from the air separator 10 to this. is there. As described in the embodiment of FIG. 4, since the oxygen concentration of the gas discharged to the outside from the carbon dioxide liquefaction device 122 through the liquefaction device exhaust gas pipe 140 is high, there is a danger in removing the gas out of the system as it is. . In this embodiment, the nitrogen gas generated during the air separation in the air separation device 10 can be supplied to the liquefier exhaust gas tube 140 through the nitrogen gas tube 150, mixed, and discharged out of the system.
Since the nitrogen gas generated in the air separation device 10 is obtained by air separation, the nitrogen gas is about four times as large as the oxygen supplied to the coal gasification furnace 5, and the dilution of the oxygen discharged from the liquefier discharge gas pipe 140 to the outside is performed. Since the temperature is low and the temperature is low, the safety is higher than that in the practical example shown in FIG.

According to the present embodiment, there is an effect that the danger of explosion or the like due to gas discharged from the coal gasifier system to the outside can be prevented.

In the sixth embodiment of the present invention, a pipe from the liquefied carbon dioxide storage device 123 is connected to a liquefier exhaust gas pipe 140 instead of the nitrogen gas pipe 150 in the embodiment of FIG. is there. The liquefied carbon dioxide stored in the liquefied carbon dioxide storage device 123 is supplied to the liquefier exhaust gas pipe 140 and decompressed to carbon dioxide, which dilutes the oxygen concentration of the gas passing through the liquefier exhaust gas pipe 140.

According to the present embodiment, there is an effect that the danger of explosion or the like due to gas discharged from the coal gasifier system to the outside can be prevented.

FIG. 6 shows a seventh embodiment of the present invention. This embodiment is different from the embodiment shown in FIG. 2 in that a carbon dioxide bypass 160 is connected between the gas = gas heat exchanger 7 and the combustor 2 of the fuel gas supply pipe 111 from the liquefied carbon dioxide storage device 123, and A carbon dioxide bypass control valve 162 and a carbon dioxide bypass evaporator 1
61 is installed.

During the normal operation of the coal gasification plant, the combustion gas recycle control valve 112, the liquefied carbon dioxide supply valve 124 and the carbon dioxide bypass control valve 162 are closed, and the fuel gas gasified in the coal gasifier 5 is The fuel gas is supplied to the combustor 2 through the fuel gas control valve 113 without passing through the combustion gas separation device 116.

Some abnormality occurs in the coal gasifier system,
When the calorific value of the gasified fuel rises to a state where the combustor 2 of the gas turbine cannot be tolerated, the carbon dioxide bypass control valve 162 is opened, and liquefied carbon dioxide is supplied from the liquefied carbon dioxide storage device 123 to the carbon dioxide bypass evaporator 161. Then, it can be supplied to the fuel gas supply pipe 111 instead of carbon dioxide by the carbon dioxide bypass evaporator 161,
The calorific value of the gasified fuel supplied to the combustor 2 can be reduced.

When the power plant is stopped, the carbon dioxide bypass control valve 162 is opened to supply liquefied carbon dioxide from the liquefied carbon dioxide storage device 123 to the carbon dioxide bypass evaporator 161.
The gas is supplied to the combustor 2 in place of carbon dioxide to purge the combustor 2, the gas turbine 3, and the exhaust heat recovery boiler 14 system.

According to this embodiment, there is an effect that damage to the combustor 2 of the power plant can be prevented. FIG. 7 shows an eighth embodiment of the present invention. The embodiment shown in FIG. 7 differs from the embodiment shown in FIG. 2 in that the gas = gas heat exchanger 7 and the fuel gas control valve 11
3 from the fuel gas supply pipe 111 to the fuel bypass 17 at startup.
0 is connected, a start-up fuel bypass valve 172 and a flare stack 171 are installed on a start-up fuel bypass 170, and a carbon dioxide bypass B 175 is installed from the liquefied carbon dioxide storage device 123 to the flare stack 171. On the carbon dioxide bypass B175, a carbon dioxide bypass B control valve 173, a carbon dioxide bypass B evaporator 174, and an oxygen mixer B177 are installed. Further, an oxygen supply pipe 176 from the air separation device 10 is provided to the oxygen mixer B177.

When the temperature rise of the coal gasification furnace system is completed, coal is supplied from the coal supply pipe 52 and gasification is performed using oxygen supplied from the oxygen compressor 11 as a gasifying agent. Since the gas does not have the properties permitted by the combustor 2, the fuel gas control valve 113 is closed, fuel is not sent to the combustor 2, and the fuel bypass valve 172 is opened at the start-up time. Send complete fuel gas. On the other hand, oxygen is sent from the air separation device 10 to the oxygen mixer B177 through the oxygen supply pipe 176. To the oxygen mixer B177, the carbon dioxide bypass B control valve 173 is opened, and the liquefied carbon dioxide is supplied from the liquefied carbon dioxide storage device 123 to the carbon dioxide bypass B evaporator 174.
The carbon dioxide is supplied and converted into carbon dioxide by the carbon dioxide bypass B evaporator 174, and the oxygen concentration can be adjusted.
Even incomplete fuel gas, which has a very low calorific value at the beginning of gasification, can be burned by increasing the oxygen concentration in the oxygen mixer. The flare stack 17 is also controlled by controlling the amount of carbon dioxide supplied from the liquefied carbon dioxide storage device 123.
1 can burn.

According to the present embodiment, the incomplete gasified fuel in the early stage of gasification is replaced with a safe gas by combustion to be discharged outside the system.

[0056]

According to the present invention, it is possible to provide an operation method and a system for reducing NOx when auxiliary fuel is used in a coal gasification power plant.

According to the present invention, it is possible to provide an operation method and a system for effectively utilizing carbon dioxide in combustion exhaust gas when using auxiliary fuel in a coal gasification furnace in a coal gasification power generation plant.

[Brief description of the drawings]

FIG. 1 shows an embodiment of the present invention.

FIG. 2 shows an embodiment of the present invention.

FIG. 3 shows an embodiment of the present invention.

FIG. 4 shows an embodiment of the present invention.

FIG. 5 shows an embodiment of the present invention.

FIG. 6 shows an embodiment of the present invention.

FIG. 7 shows an embodiment of the present invention.

FIG. 8 is a reference diagram showing the effect of the present invention.

[Explanation of symbols]

2 ... combustor, 5 ... coal gasifier, 10 ... air separation device,
11: oxygen compressor, 112: combustion gas recycle control valve, 114: combustion gas recycle pipe, 115: combustion gas recycle compressor, 116: combustion gas separation device, 119
... exhaust gas pipe, 121 ... carbon dioxide compressor, 122 ... carbon dioxide liquefaction device, 123 ... liquefied carbon dioxide storage device,
130: liquefied carbon dioxide low-temperature storage device, 131: liquefied carbon dioxide pump, 132: low temperature nitrogen pipe, 140: liquefier exhaust gas pipe, 150: nitrogen gas pipe, 160: carbon dioxide bypass, 162: carbon dioxide bypass control valve, 1
70: startup fuel bypass, 171: flare stack, 175: carbon dioxide bypass B, 176: oxygen supply pipe, 177: oxygen mixer B.

──────────────────────────────────────────────────の Continuation of the front page (51) Int.Cl. ⁶ Identification code FI F02C 6/00 F02C 6/00 E 7/26 7/26 A (56) References JP-A-57-83636 (JP, A) JP-A-2-157426 (JP, A) JP-A-61-233083 (JP, A) JP-A-61-114009 (JP, A) JP-A-3-43608 (JP, A) JP-A-50-111101 (JP, A) JP-A-57-183529 (JP, A) JP-A-3-145523 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) F02C 3/30 C10J 3 / 46 F02C 3/28 F02C 6/00 F02C 7/26

Claims (6)

(57) [Claims] 1. A coal supply system for supplying coal, an oxygen separation system for separating oxygen from air, an auxiliary fuel supply system for supplying auxiliary fuel, and warmed by combustion of the auxiliary fuel at the time of start-up of the coal supply system for normal operation In a coal gasification plant consisting of a coal gasifier, which is sometimes supplied with coal and oxygen to obtain gasified coal, and a refining means for purifying gasified coal, an inert gas other than nitrogen is obtained from the refined gasified coal. Inert gas separating means for separating gas, mixing means for mixing the separated inert gas with oxygen from the oxygen separation system, and supplying the mixed gas of inert gas and oxygen to the coal gasifier together with auxiliary fuel And a coal gasification plant comprising: 2. The coal gasification plant according to claim 1, wherein
A coal gasification plant wherein the auxiliary fuel is a hydrocarbon fuel and carbon dioxide is separated as an inert gas other than nitrogen. 3. The coal gasification plant according to claim 1, wherein
A coal gasification plant wherein the auxiliary fuel is a hydrocarbon fuel and separates steam as an inert gas other than nitrogen. 4. A coal supply system for supplying coal, an oxygen separation system for separating oxygen from air, an auxiliary fuel supply system for supplying a hydrocarbon-based auxiliary fuel, and heating by starting combustion of the auxiliary fuel when the system is started. In a coal gasification plant consisting of a coal gasifier that is supplied with coal and oxygen during normal operation to obtain gasified coal, and a refining means for refining the gasified coal, Carbon dioxide separating means for separating carbon, mixing means for mixing the separated carbon dioxide and oxygen from the oxygen separation system, and means for supplying a mixed gas of carbon dioxide and oxygen to a coal gasifier together with auxiliary fuel. A coal gasification plant comprising liquefied carbon dioxide means and liquefied carbon dioxide storage means. 5. A method of operating a coal gasifier which is heated by the combustion of auxiliary fuel at the time of start-up and is supplied with coal and oxygen during normal operation to obtain gasified coal. To separate the inert gas
A method for operating a coal gasifier in which auxiliary fuel is burned by the mixed gas of the inert gas and oxygen. 6. A method for operating a coal gasifier which is heated by the combustion of a hydrocarbon-based auxiliary fuel at the time of startup and is supplied with coal and oxygen during normal operation to obtain gasified coal. A method of operating a coal gasifier that separates carbon dioxide, combusts auxiliary fuel with the mixed gas of carbon dioxide and oxygen, and liquefies and stores carbon dioxide.