JP2010230287A - Coal gasification power-generating plant and combustion method for coal gasification power-generating plant - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To further reduce NOx by disposing a partitioning wall having an injection hole for injecting nitrogen produced by an air separator to the outer periphery sidewall surface of an inner cylinder, on the inner side of an outer cylinder. <P>SOLUTION: This coal gasification power-generating plant includes the air separator for separating the air into oxygen and nitrogen, a gasification furnace for producing a coal gasification gas by coal and oxygen produced by the air separator, a gas turbine combustor producing a combustion gas by the coal gasification gas produced by the gasification furnace, and a turbine driven by the combustion gas. On the inner side of the an outer cylinder of the gas turbine combustor, the partitioning wall is provided having the injection hole for injecting nitrogen produced by the air separator to the outer periphery sidewall surface of an inner cylinder of the gas turbine combustor. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a coal gasification power plant and a combustion method for the coal gasification power plant.

In recent years, diversification of fuel has been studied for gas turbine combustors. Specifically, the use of by-product fuel containing hydrogen in addition to liquefied natural gas (LNG), which is the main fuel of gas turbines, has been studied. Since hydrogen does not generate carbon dioxide (CO ₂ ) during combustion, it is a fuel that can contribute to the prevention of global warming. By-product fuel containing hydrogen includes, for example, a gas (COG: Coke Oven Gas) generated from a coke oven, which is a raw material for a blast furnace, and an off-gas generated at a petroleum refinery. Gasified fuel obtained by gasifying coal or heavy oil with oxygen is also a fuel containing hydrogen. The Coal Gasification Combined Cycle (IGCC), which gasifies coal, heavy oil, etc. with oxygen and uses gas fuel to generate power with a gas turbine, is a power generation system that makes effective use of abundant resources. It has been put to practical use mainly in Europe and America.

In recent years, a CO ₂ separation and capture system (CCS: Carbon Dioxide Capture and Storage) that separates and removes carbon in fuels has been studied from the viewpoint of preventing global warming. This CO ₂ separation and recovery system is also being considered for application to IGCC and other power generation systems. The fuel after the separation and recovery of CO ₂ by CCS becomes a hydrogen-rich fuel containing a large amount of hydrogen. Therefore, a combustor that uses hydrogen-rich fuel needs to cope with problems peculiar to hydrogen-containing fuel. In addition, since the IGCC plant has a different fuel composition depending on the type of coal, gasifier load, CCS operating conditions, etc., a combustor that can cope with changes in the fuel composition is required. A typical gas generated in an IGCC plant is a medium calorie gas. This medium calorie gas has a higher flame temperature than that of LNG, which is a general high calorie fuel, and requires measures to reduce NOx. In addition, since hydrogen generated in a large amount by providing CCS has a wide flammable range and a high combustion speed, the flame easily approaches the burner during combustion.

  When the gas turbine combustor of the IGCC plant adopts the premixed combustion method, the flame may easily backfire in the premixed gas flow path due to changes in the flame position formed in the burner, and the reliability of the combustor may be impaired. There is. On the other hand, the diffusion combustion method has a lower risk of impairing the reliability of the combustor than the premixed combustion, but the local flame temperature is increased and the NOx emission amount is increased. As a countermeasure, a system is adopted in which nitrogen generated in the air separation device is injected into the combustor and NOx is reduced by lowering the local flame temperature. However, in order to improve the plant efficiency, if the nitrogen temperature is raised or the amount of nitrogen injection generated in the plant cannot be secured sufficiently, the NOx environmental value cannot be satisfied, and additional measures such as steam injection are required. .

  In addition to these combustion methods, a method of relaxing the high temperature region includes a distributed lean combustion method. This is a system in which fuel to be injected is wrapped in an air flow, and the fuel and air are rapidly mixed by contraction and rapid expansion when passing through the air hole.

  Further, Patent Document 2 is disclosed as an example of supplying nitrogen generated from an air separation device to a gas turbine combustor in an IGCC plant that generates power by gasifying coal with oxygen. The combustor described in Patent Document 2 is a combination of a diffusion burner for flame stabilization and a premixed burner for low NOx. This combustor reduces the cooling air supplied to the inner cylinder by cooling the inner cylinder with nitrogen. As the cooling air is reduced, the combustion air supplied to the premix burner is increased to dilute the air-fuel mixture and lower the NOx concentration.

JP 2003-148734 A JP-A-8-68301

  The combustor of Patent Document 1 rapidly mixes fuel and air by contraction and rapid expansion when passing through an air hole. However, when hydrogen-rich fuel is used, since the hydrogen-rich fuel has a high combustion rate, there is a possibility that the fuel concentration is ignited with a deviation remaining and the NOx concentration increases.

  Further, in the combustor of Patent Document 2, when the fuel composition or the fuel flow rate is changed, there is a possibility that a deviation occurs in the fuel concentration in the premixed gas and the NOx concentration increases.

  Accordingly, an object of the present invention is to further reduce NOx.

  The present invention is characterized in that a partition wall provided with an injection hole for injecting nitrogen generated by the air separation device to the outer peripheral side wall surface of the inner cylinder is provided inside the outer cylinder.

  According to the present invention, it is possible to further reduce NOx.

1 is a structural diagram of a combustor showing Example 1. FIG. 1 is a front view of a combustor related to Example 1. FIG. 2 is a partially enlarged view of a burner relating to Example 1. FIG. FIG. 3 is a conceptual diagram showing a fuel concentration related to Example 1. It is a figure which shows the relationship between the fuel density | concentration regarding Example 1, and flame temperature. 1 is a system schematic diagram of a power plant showing Example 1. FIG. It is a figure which shows the change of the fuel flow volume with respect to the gas turbine load regarding Example 1, and the figure which shows the change of nitrogen flow volume and extraction air flow volume. 6 is a front view of a burner relating to Example 2. FIG.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 6 shows an outline of a system related to the coal gasification power plant of this embodiment. First, the configuration and system of this plant will be described.

The gasification power plant of this embodiment includes a gasification furnace 21, a gas purification device 22, a CO ₂ separation and recovery device 23, a gas turbine 5, an air separation device 11, and the like. The gasification furnace 21 generates coal gasification gas 60 from the coal 20, the gas purification device 22 removes impurities in the fuel by desulfurization and dedusting, and the CO ₂ separation and recovery device 23 converts the carbon content in the fuel into steam. to generate H ₂ and CO ₂ by a shift reaction, a facility for separating and removing CO _2. The coal gasification gas 63 exiting the CO ₂ separation and recovery device 23 is supplied to the gas turbine combustor 3 to generate thermal energy. The turbine 4 generates rotational energy, transmits power to the generator 6, and generates electricity. The air separation device 11 can supply the extracted air 103 from the compressor 2 and the discharge air 110 from the backup compressor 14. Even before the gas turbine is started, the oxygen 120 necessary for the gasification furnace 21 can be supplied by the discharge air 110 of the backup air compressor 14. When the gas turbine 5 is started with the starting liquid fuel 51 and the extraction air 103 can be supplied from the compressor 2 to the air separation device 11, the discharge air 110 of the backup compressor 14 is increased by the increase of the extraction air 103. The flow rate can be reduced.

  The oxygen 120 produced by the air separation apparatus 11 is supplied to the gasification furnace 21 after being pressurized by the oxygen boosting compressor 15. Further, the nitrogen 130 generated by the air separation is boosted by the nitrogen boosting compressor 13 and then supplied to the gas turbine combustor 3.

The composition of the fuel supplied to the gas turbine combustor 3 differs greatly before and after the CO ₂ separation and recovery. A typical composition before CO ₂ recovery is a fuel (composition A) containing H ₂ and CO as main components. On the other hand, after conversion by the CO ₂ recovery apparatus of CO in the fuel to CO ₂ by steam and the shift reaction, the CO concentration in the fuel by separating and recovering reduced. For this reason, the coal gasification gas discharged from the CO ₂ separation and recovery device 23 has a high H ₂ concentration in the fuel under the condition that the CO ₂ recovery rate is high, and becomes H ₂ rich fuel (composition B). In the present plant, when trouble occurs in the CO ₂ separation and recovery device 23 while supplying H ₂ rich fuel to the gas turbine, the CO ₂ separation and recovery device 23 must be stopped. While the CO ₂ separation and recovery device 23 is stopped, the fuel of composition A is supplied to the gas turbine combustor. In addition, when the fuel of composition A is being supplied to the gas turbine and the system is switched to pass the coal gasification gas to the CO ₂ separation and recovery device 23, the fuel supplied to the gas turbine combustor changes from composition A to composition B. However, the H ₂ concentration in the fuel changes greatly. Therefore, the gas turbine combustor needs to cope with these composition changes. In particular, when the fuel changes from composition A to composition B, the combustion rate increases with an increase in the H ₂ concentration in the fuel, so that the risk of backfire increases with low NOx combustion by premixed combustion.

  FIG. 1 shows a system diagram of a gas turbine and an enlarged view of a gas turbine combustor. The gas turbine 5 includes a compressor 2, a gas turbine combustor 3, a turbine 4, a generator 6, a starter motor 8, and the like. The gas turbine 5 compresses the air 101 sucked from the atmosphere by the compressor 2 and supplies the combustion air 102 to the gas turbine combustor 3. The gas turbine combustor 3 generates the combustion gas 140 by mixing and burning the combustion air 102 and the starting liquid fuel 51 or the coal gasification gas 62 (63) by the compressor 2, and the combustion gas 140 is converted into the turbine 4. To supply. The turbine 4 is supplied with rotational power by supplying the combustion gas 140, and the rotational power of the turbine 4 is transmitted to the compressor 2 and the generator 6. The rotational power transmitted to the compressor 2 is used as compression power, and the rotational power transmitted to the generator 6 is converted into electric energy.

  The gas turbine combustor 3 includes an outer cylinder 10 that is a pressure vessel, an inner cylinder 151 that is provided inside the outer cylinder 10 and that forms a combustion chamber 12 therein, and an outer periphery that forms a flame upstream of the combustion chamber 12. A burner 300, a pilot burner 301 capable of gas combustion with the starting liquid fuel, and a tail cylinder (not shown) for guiding the combustion gas 140 generated in the combustion chamber 12 to the turbine 4 are provided. An outer peripheral burner 300 for performing low NOx combustion is a plurality of air holes 310 opened in the air hole plate 315, and a plurality of fuel nozzles 320 that are located upstream of the air holes 310 and inject fuel into the air holes 310. Is provided. On the other hand, in the pilot burner 301, an oil nozzle 302 is arranged in the center in the radial direction of the burner constituted by a plurality of air holes and a fuel nozzle. In the combustor of the present embodiment, the pilot burner 301 is disposed at the center in the radial direction of the combustor, and a plurality of outer peripheral burners 300 are disposed on the outer peripheral side thereof.

  A cylindrical partition wall 150 is provided between the inner cylinder 151 and the outer cylinder 10. FIG. 2 shows a cross-sectional view of the partition wall 150. The downstream end of the partition wall 150 is joined to the outer cylinder 10. In an annular space surrounded by the outer cylinder 10 and the partition wall 150, the nitrogen 130 from the nitrogen boosting compressor 13 flows. The cylindrical partition wall 150 is provided with a nitrogen injection hole 135 for injecting nitrogen. The nitrogen injection hole 135 has an annular structure and is arranged so that the nitrogen jet collides with the inner cylinder 151 at an axial position close to the burner. A plurality of nitrogen injection holes 135 are arranged in the circumferential direction, and five rows are arranged in the combustor axial direction. Nitrogen 130 injected from the nitrogen injection hole 135 becomes a jet and collides with the outer peripheral side wall surface of the inner cylinder 151, and the inner cylinder 151 is cooled by the collision jet. Nitrogen 130 flows through the space between partition wall 150 and inner cylinder 151 while mixing with combustion air 102, and flows into air holes 310 of outer peripheral burner 300 and pilot burner 301. Therefore, each burner is supplied with low oxygen concentration air 102a in which combustion air 102 and nitrogen 130 are mixed. Flames 200 and 201 are formed by mixing and burning the low oxygen concentration air 102a and the coal gasification gases 62 and 63.

  Hereinafter, an operation method using a gasification power plant as an example will be described. At startup, the gas turbine is driven by external power such as a starter motor 8. The gas turbine rotational speed is kept constant at the rotational speed corresponding to the ignition condition of the combustor, and the combustion air 102 necessary for ignition is supplied to the gas turbine combustor 3 to satisfy the ignition condition. Then, the starting liquid fuel 51 is supplied from the oil nozzle 302 to the combustion chamber 12 and ignited. Thereafter, the combustion gas 140 is supplied to the turbine 4, and the turbine 4 increases in speed as the flow rate of the liquid fuel 51 increases. Then, the starter motor 8 is detached, and the gas turbine enters a self-sustained operation and reaches the no-load rated rotational speed. After the gas turbine reaches the no-load rated rotational speed, the inlet gas temperature of the turbine 4 increases due to the addition of the generator 6 and the increase in the flow rate of the liquid fuel 51, and the load increases. After loading, the air separation device 11 generates oxygen by extracting the extraction air 103 necessary for the air separation device 11 from the compressor 2. Further, the nitrogen 130 generated by the air separation device 11 is supplied to the gas turbine combustor 3. The air required for the air separation device 11 can also be supplied from the backup compressor 14. Therefore, by supplying oxygen 120 from the air separator 11 to the gasifier, the gasifier can be operated before the gas turbine is started.

  The gas turbine combustor injects nitrogen 130 generated in the air separation device 11 into the inner cylinder 151, so that the local flame temperature can be lowered even during the liquid fuel burning operation, and the NOx emission concentration can be suppressed. Thereafter, when coal gas can be supplied as the gasifier load increases, the combustor switches the fuel from liquid fuel burning to gas burning. The fuel switching operation is performed under a substantially constant load condition, and the flow rate of the liquid fuel 51 ejected from the pilot burner 301 is decreased, and at the same time, the flow rate of the coal gasification gas 62 (or 63) is increased to switch to gas-only combustion. After switching to gas-only firing, the load can be increased by increasing the fuel flow rate of the outer peripheral burner 300. An outline of these operation schedules is shown in FIGS.

FIG. 7A shows changes in the flow rates of the liquid fuel 51 and the coal gasification gas 62 (or 63) with respect to the gas turbine rotational speed and the gas turbine load, and FIG. 7B schematically shows changes in the extraction air and nitrogen injection flow rates. Respectively. The flow rate of the coal gasification gas in FIG. 7A indicates the total flow rate supplied to the combustor. The states (a) to (e) in the figure are:
(A) Ignition by starting fuel (b) No-load rated speed (c) At the start of fuel switching (d) At the completion of fuel switching (e) Represents the rated load. The states (a) to (c) are the exclusive combustion of the starting fuel, the states (c) and (d) are the mixed combustion of the starting fuel and the coal gasification gas, and the states (d) and (e) are the exclusive combustion of the gas. It becomes a driving state.

  After the ignition with the starting fuel is completed and the no-load rated rotation speed of the gas turbine is reached, the nitrogen 130 can be supplied to the gas turbine combustor. FIG. 7 (b) reaches the no-load rated speed and supplies nitrogen after loading. However, by supplying the discharge air of the backup compressor to the air separation device, nitrogen can be supplied to the gas turbine combustor before reaching the no-load rated rotational speed. After supplying nitrogen to the combustor, air can be extracted from the compressor 2 to the air separation device 11 as the load of the gas turbine increases. The flow rate of the bleed air is approximately proportional to the change in the gas turbine load. Thereafter, when the coal gasification gas can be supplied, the gas turbine combustor can switch the fuel from the liquid fuel burning to the gas burning [state (c)]. During fuel switching [states (c), (d)], operation is performed with the nitrogen flow rate and the bleed air flow rate kept constant under almost constant load conditions to ensure combustion stability. The fuel is switched to gas-only firing by reducing the flow rate of the liquid fuel 51 and increasing the flow rate of the coal gasification gas 62 (or 63) [state (d)]. After switching to gas-only firing, the load can be increased as the fuel flow rate increases.

  Next, the concept of reducing NOx using low oxygen concentration air will be described with reference to FIGS. FIG. 2 is a view of the gas turbine combustor shown in FIG. 1 as viewed from the downstream side (combustion chamber side). A pilot burner 301 capable of liquid fuel combustion and gas combustion is provided at the radial center of the combustor, and a plurality of outer peripheral burners 300 are arranged on the outer peripheral side thereof. These burners comprise coaxial jet burners with fuel nozzles and air holes. The pilot burner 301 includes an oil nozzle 302 inside a coaxial jet burner capable of gas combustion. On the other hand, a partition wall 150 is provided on the outer peripheral side of the inner cylinder 151, and the partition wall 150 is provided with a nitrogen injection hole 135 that injects nitrogen 130 toward the outer peripheral side wall surface of the inner cylinder 151. The injected nitrogen 130 becomes a jet and collides with the inner cylinder 151 to cool the inner cylinder wall surface by heat transfer (impingement cooling). The nitrogen 130 that has cooled the inner cylinder 151 is mixed with combustion air and supplied to the air holes 310 of the outer peripheral burner and the pilot burner.

  FIG. 3 shows a partially enlarged view of air holes and fuel nozzles in the outer peripheral burner 300. A fuel nozzle 320 for injecting fuel into the air holes is disposed upstream of the air holes 310 opened in the air hole plate 315. The tip of the fuel nozzle 320 is provided with an injection hole 320a for injecting fuel, and fuel can be injected toward the combustion chamber. Low oxygen concentration air 102a in which nitrogen and combustion air are mixed is supplied from the periphery of the fuel nozzle, and the injected coal gasification gas 62 (63) and the low oxygen concentration air 102a are compressed and discharged at the air hole inlet. Due to the rapid expansion at, the flame 200 is formed. In this mixing process, a fuel concentration distribution exists in the air-fuel mixture (M portion in FIG. 3) flowing into the flame.

FIG. 4 schematically shows the fuel concentration distribution with respect to the jet diameter corresponding to the air hole. The central portion in the radial direction of the air hole located coaxially with the fuel injection hole tends to be higher than the average fuel concentration C _{ave in} which the fuel and air are mixed (C ₁ ). Further, the outer peripheral side of the fuel injection hole tends to be lower than the average fuel concentration (C ₀ ). As the density increases, the NOx concentration increases in a region where the fuel concentration is high. These phenomena will be described based on the flame temperature in FIG.

FIG. 5 shows the change in the theoretical flame temperature with respect to the fuel / air mixture concentration (equivalent ratio). In the figure, the flame temperature by fuel and air and the flame temperature by fuel and low oxygen concentration air are compared and shown. First, the design temperature for reducing NOx at the burner outlet is a ° C. This temperature assumes operation at an average fuel concentration _Cave1 when fuel and air are used. When a fuel concentration deviation occurs in the mixture of fuel and air and the equivalent ratio of C ₁ is reached, the flame temperature becomes d ° C., which is higher than the design temperature a ° C. For this reason, the NOx concentration increases as the flame temperature rises. On the other hand, when low oxygen concentration air in which air and nitrogen are mixed is used, the average fuel concentration at the design temperature of a ° C. is C _ave2 . And even if the equivalence ratio of C ₁ exists locally due to the deviation of the fuel concentration, the flame temperature by the low oxygen concentration air remains at b ° C. (b ° C. <d ° C.). That is, it is possible to further suppress the NOx concentration by using nitrogen generated in the plant as compared with a normal fuel / air mixture.

  As described above, the partition wall 150 provided with the nitrogen injection holes 135 for injecting the nitrogen 130 generated by the air separation device 11 to the outer peripheral side wall surface of the inner cylinder 151 is provided inside the outer cylinder 10. The generated inert medium such as nitrogen cools the inner cylinder 151 and is then mixed with the combustion air 102 to become low oxygen concentration air. By supplying this low oxygen concentration air to each burner, it is possible to suppress an increase in flame temperature even if a deviation in fuel concentration occurs in the burner portion, and low NOx combustion becomes possible. Therefore, it is not necessary to use combustion air for cooling the inner cylinder, and at the same time, it is possible to further reduce NOx.

  Further, in the conventional diffusion combustor, additional measures such as steam injection are not necessary, which can contribute to reduction of steam injection equipment cost and improvement of plant efficiency.

The burner of the gas turbine combustor according to the present embodiment is disposed on the upstream side of the combustion chamber 12, and includes an air hole plate 315 having an air hole 310 for supplying the combustion air 102 to the combustion chamber 12, and an air hole plate. Since it has the fuel nozzle 320 which is arrange | positioned in the upstream of 315 and injects coal gasification gas to the air hole 310, the mixing distance of fuel and air is short, and risks, such as a backfire, can be excluded. Therefore, by applying the burner to the IGCC plant, even if the fuel composition supplied to the gas turbine combustor changes depending on the operating state of the CO ₂ separation and recovery device, the risk of backfire and the like can be eliminated. And it becomes possible to operate | move continuously with the same combustor, without stopping gas turbine equipment. In addition, since low oxygen concentration air is supplied to the burner, even if a deviation in fuel concentration occurs due to a change in fuel composition, an increase in flame temperature can be suppressed, and low NOx combustion becomes possible.

  This embodiment is an example of changing the circumferential pitch of nitrogen injection holes. FIG. 8 is a structural view seen from the combustor downstream side. The inner wall surface of the inner cylinder 151 and the outer peripheral burner 300 arranged on the upstream side of the combustor are arranged adjacent to each other because of space. Depending on the operating conditions of the combustor, the inner wall surface of the inner cylinder 151 is affected by the flame 200 formed on the outer burner 300, and the metal temperature of the inner wall surface A portion of the inner cylinder 151 may be higher than that of the B portion. There is. In this embodiment, the metal temperature rise in the A part is suppressed. Specifically, in order to effectively supply nitrogen to the inner cylindrical wall surface (A part) in the vicinity of the burner, the nitrogen injection holes 135 are concentratedly opened in the partition wall 150 adjacent to the burner. The rise in metal temperature between the outer peripheral burners (B part) is lower than that in the A part. Therefore, even if the impingement cooling with nitrogen is not performed on the part B, the degree of increase in the metal temperature is low. Nitrogen cooled around the A part becomes low oxygen concentration air mixed with combustion air, and is supplied to the air holes 310 provided in the outer peripheral burner 300 and the pilot burner 301. Then, combustion of low oxygen concentration air and fuel enables low NOx combustion as in the first embodiment.

  So far, the pilot burner has been shown with an oil nozzle, but the same effect can be obtained by using a high-calorie fuel such as liquefied petroleum gas (LPG) or LNG as the starting fuel. In that case, the pilot burner has a nozzle configuration similar to that of the outer peripheral burner.

In addition, in the peripheral burner, the example in the case of supplying coal gasification gas was shown, but coal gas such as high calorie fuel such as LNG and LPG, coke oven gas and H ₂ rich fuel generated in oil refinery, etc. Similar effects can be obtained with fuels other than activated gas.

2 Compressor 3 Gas Turbine Combustor 4 Turbine 5 Gas Turbine 6 Generator 8 Motor for Start-up 10 Outer Cylinder 11 Air Separation Device 12 Combustion Chamber 20 Coal 21 Gasification Furnace 22 Gas Purification Device 23 CO ₂ Separation and Recovery Device 51 Liquid Fuel 62 , 63 Coal gasification gas 101 Air 102 Combustion air 102a Low oxygen concentration air 103 Extraction air 120 Oxygen 130 Nitrogen 135 Nitrogen injection hole 140 Combustion gas 300 Outer burner 301 Pilot burner 302 Oil nozzle 310 Air hole 315 Air hole plate 320 Fuel nozzle 320a injection hole

Claims (4)

An air separation device for separating air into oxygen and nitrogen;
A gasification furnace that generates coal gasification gas from the oxygen generated by the coal and the air separation device;
A gas turbine combustor that generates combustion gas from the coal gasification gas generated by the gasification furnace;
A turbine driven by the combustion gas,
The gas turbine combustor includes an outer cylinder, an inner cylinder which is disposed inside the outer cylinder and forms a combustion chamber for burning the coal gasification gas, and a burner which burns with the coal gasification gas. In our coal gasification plant,
A coal gasification plant characterized in that a partition wall provided with injection holes for injecting the nitrogen generated by the air separation device onto the outer peripheral side wall surface of the inner cylinder is provided inside the outer cylinder. A coal gasification plant according to claim 1,
The burner of the gas turbine combustor is disposed on the upstream side of the combustion chamber, and is disposed on the upstream side of the air hole plate having an air hole for supplying combustion air to the combustion chamber, A coal gasification plant comprising: a fuel nozzle that injects the coal gasification gas into the air holes. A coal gasification plant according to claim 1,
The coal gasification plant, wherein the injection hole for injecting nitrogen is provided in the partition so as to inject the nitrogen only to the inner cylinder wall surface in the vicinity of the burner. An air separation device for separating air into oxygen and nitrogen;
A gasification furnace that generates coal gasification gas from the oxygen generated by the coal and the air separation device;
A gas turbine combustor that generates combustion gas from the coal gasification gas generated by the gasification furnace;
A turbine driven by the combustion gas,
The gas turbine combustor includes an outer cylinder, an inner cylinder which is disposed inside the outer cylinder and forms a combustion chamber for burning the coal gasification gas, and a burner which burns with the coal gasification gas. In the combustion method of the coal gasification plant
The nitrogen generated by the air separation device is sprayed onto the outer peripheral side wall surface of the inner cylinder, and after cooling the inner cylinder with the nitrogen, the nitrogen and combustion air are mixed to generate low oxygen concentration air. A combustion method for a coal gasification plant, wherein the low oxygen concentration air is supplied to the burner.

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