JP2617089B2 - Integrated coal gasification combined cycle power plant - Google Patents

Abstract

PURPOSE:To reduce heat bypass rate and improve plant efficiency by introducing inert gas having high pressure as cooling medium into a gas cooler for heat exchange and introducing inert gas having high temperature into a gas turbine through a combuster. CONSTITUTION:Coal is gasified in a gasifying furnace 1, gas formed therein is supplied to a combuster 4 via a gas cooler 2 and a gas purification device 3 to mix it with air compressed by a compressor 8 for combustion. A gas turbine 5 is rotated by high pressure and temperature gas which is obtained thus to drive a generator 9, and steam turbines 6, 6' are rotated by steam which is generated in an exhaust gas boiler 7 due to heat exchange with exhaust gas in the gas turbine 5. In this case, a part of nitorgen 14 which is separated from oxygen in an air separation equipment 11 and whose pressure is increased by a nitrogen compressor 12 is fed as cooling medium of the gas cooler 2, and nitorgen 14 whose temperature is raised in the gas cooler 2 is introduced into the gas turbine 5 via the combuster 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a system for reducing heat bypass (bypass of gas turbine) and increasing plant efficiency in an integrated coal gasification combined cycle power plant.

[0002]

2. Description of the Related Art FIG. 3 is a system diagram of an integrated coal gasification combined cycle power plant described in Japanese Utility Model Laid-Open No. 57-168735. The conventional technology includes a gas turbine 51 and its exhaust gas 5.
An exhaust heat boiler 53 which generates steam 54 by heat exchange with
In the combined cycle power plant constituted by the steam turbine 55 driven by the steam 54, the oxygen is separated into oxygen 61 and nitrogen 59 by an air separator 58,
1 is used as a gasifying agent in a gasification furnace 63 for gasifying coal 62 by pressurizing with an oxygen compressor 60, and nitrogen 59 is pressurized by a nitrogen compressor 65 and used as a gas turbine 5.
One of the combustors 66 is injected.

[0003]

That is, in the above prior art, a part of the nitrogen gas generated by the air separator is introduced into the combustor of the gas turbine instead of the bleeding from the steam turbine used up to that time. Since the purpose is to reduce nitrogen oxides (NOx) in the combustion gas by injection, improvement of the plant efficiency by this technique cannot be expected. The present invention has been made in view of such a situation, and an object of the present invention is to provide a system capable of significantly improving the plant efficiency of a combined gasification combined cycle power plant with a simple configuration.

[0004]

The above object is achieved by a combined gasification combined cycle power plant as set forth in the appended claims. That is, (1) a gasifier for gasifying coal, a gas cooler for cooling the gas generated in the gasifier, a gas purification device for purifying the generated gas, a gas turbine using the generated gas as a fuel, and a gas turbine. An exhaust gas boiler that generates steam by exchanging heat with exhaust gas of a turbine, a steam turbine driven by steam from the exhaust gas boiler, and a device that pressurizes an inert gas, and a generator is generated by the gas turbine and the steam turbine In a coal gasification combined cycle power plant that drives and generates electricity, the pressurized inert gas is introduced into a gas cooler as a cooling medium to perform heat exchange, and the heated inert gas is introduced into a gas turbine through a combustor. Combined power plant.

(2) The integrated coal gasification combined cycle power plant according to (1), wherein the inert gas is nitrogen gas generated from an air separation device. (3) The integrated coal gasification combined cycle power plant according to (1), wherein the inert gas is nitrogen gas generated from a nitrogen production device. (4) Inert gas is exhaust gas from gas purification equipment
(1) The combined gasification combined cycle power plant described in (1). Hereinafter, the operation and the like of the present invention will be described based on examples.

[0006]

FIG. 1 is a system diagram of an integrated coal gasification combined cycle power plant according to a first embodiment of the present invention, and FIG. 2 is a system diagram of a combined coal gasification combined cycle power plant according to a second embodiment of the present invention. is there. 1 and 2, 1 is a gasifier, 2 is a gas cooler, 3 is a gas purifier, 4 is a combustor, 5 is a gas turbine, 6 and 6 'are steam turbines, 7 is an exhaust gas boiler, 8 is a compressor, 9 Is a generator, 10 and 19 are air compressors, 11 is an air separation device, 12 is a nitrogen compressor,
13 is an oxygen compressor, 14 is nitrogen, 15 is steam, 16 is oxygen, 17 is a desulfurization device, 18 is a nitrogen production device, 20 is air, and 21 is coal.

First, a first embodiment shown in FIG. 1 will be described. Coal charged into gasifier 1 (generally pulverized coal)
In a high-temperature and strong reducing atmosphere, oxygen 21 is separated from the air supplied from the air compressor 10 by the oxygen compressor 13 and separated by the air separation device 11 and pressurized by the oxygen compressor 13. And discharged from the gasification furnace 1 at high temperature and high pressure.

Since the product gas discharged from the gasification furnace 1 contains impurities such as residual ash, nitrogen oxide and sulfur oxide gases, and alkali metals, it is necessary to remove them. The gas is sent into the gas cooler 2 to cool the apparatus to an allowable temperature.

As a cooling medium, a part of the nitrogen 14 separated from oxygen in the air separation device 11 is supplied to the gas cooler 2 by pressurizing the nitrogen with a nitrogen compressor 12, and heat exchange with the produced gas is performed. As a result, the generated gas is reduced to an appropriate temperature and flows into the gas purification device 3 disposed downstream, where impurities are removed therefrom, and then flows into the combustor (combustor) 4 of the gas turbine 5. On the other hand, the nitrogen 14 as a cooling medium that has exchanged heat with the high-temperature generated gas in the gas cooler 2 flows into the combustor 4 of the gas turbine 5 in the same manner as the generated gas while the temperature is raised.

The product gas burned by the high-pressure air supplied from the compressor 8 in the combustor 4 and the nitrogen 14 whose heat is enhanced through the combustor 4 flow into the gas turbine 5 at a high temperature and a high pressure to flow into the gas turbine 5. The gas turbine 5 directly connected to 9 is driven.

The mixed gas of the combustion gas and the nitrogen 14 that has driven the gas turbine 5 enters the exhaust gas boiler 7 disposed further downstream with the temperature and pressure lowered, and
After generating high-pressure steam 15 and driving the steam turbines 6, 6 ', sulfur oxides are removed in a desulfurization unit 17,
Discharged at low temperature and clean.

On the other hand, in the conventional coal gasification combined cycle power plant, pressurized water is generally used as a cooling medium to be fed into the gas cooler, and the gas cooler exchanges heat with a high-temperature generated gas to raise the temperature. The generated water is used as feed water for an exhaust gas boiler, the increased heat is converted into generated steam, and the steam with the increased evaporation is sent to a steam turbine to increase the power generation. .

In general, when a gas turbine and a steam turbine are compared, the gas turbine is higher and the steam turbine is lower in terms of thermal efficiency. Therefore, when the heat absorbed by the gas cooler is converted into steam and the steam turbine is driven to generate power as described above, the heat efficiency cannot be expected to be so high.

On the other hand, as in the integrated coal gasification combined cycle power plant according to the present invention, an inert gas is used as a cooling medium for a gas cooler, and the temperature of the heat-absorbed gas is raised through a combustor of a gas turbine. By supplying power to a gas turbine with high thermal efficiency to generate power, sending the gas discharged from the gas turbine to an exhaust gas boiler to generate steam, and driving the steam turbine with the steam to further contribute to power generation In addition, the plant efficiency can be significantly improved.

FIG. 2 is a system diagram of an integrated coal gasification combined cycle power plant according to a second embodiment of the present invention.
While the embodiment of the present invention is directed to a so-called oxygen-blown gasifier, the second embodiment pressurizes the atmosphere with an air compressor 19 and sends the compressed air to the gasifier 1 to remove coal 21. It is a figure which shows the case of the gasification furnace 1 called the air blowing to gasify.

In this embodiment, the air separation device 11 of the first embodiment is not provided, and a part of the nitrogen 14 from the nitrogen production device 18 is used as a cooling medium of the gas cooler 2. Also in this case, the heat of the nitrogen 14 recovered by the gas cooler 2 is first used in the gas turbine 5,
Next, in the point that it is converted into steam in the exhaust gas boiler 7 and used in the steam turbines 6, 6 ', it is exactly the same as in the first embodiment.

As a cooling medium for the gas cooler, instead of the nitrogen used in the first and second embodiments, for example, a low-temperature gas discharged from a desulfurization unit 17 shown in FIGS. It is needless to say that substantially the same effects can be obtained by appropriately pressurizing and using the active gas.

[0018]

As described above, according to the present invention, in the integrated coal gasification combined cycle power plant, the heat recovered in the gas cooler is conventionally directly converted into steam to drive the steam turbine, as described in the above embodiment. On the other hand, by first driving the gas turbine, which has higher thermal efficiency than the steam turbine in the gaseous state, and then converting the heat of the exhaust gas to steam to drive the steam turbine, the plant thermal efficiency is significantly improved. This has the effect that it can be increased.

[Brief description of the drawings]

FIG. 1 is a system diagram of an integrated coal gasification combined cycle power plant according to a first embodiment of the present invention.

FIG. 2 is a system diagram of an integrated coal gasification combined cycle power plant in a second embodiment according to the present invention.

FIG. 3 is a system diagram of an integrated coal gasification combined cycle power plant in an example of the related art.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Gasifier 2 Gas cooler 3 Gas purifier 4 Combustor 5 Gas turbine 6, 6 'Steam turbine 7 Exhaust gas boiler 8 Compressor 9 Generator 10, 19 Air compressor 11 Air separator 12 Nitrogen compressor 13 Oxygen compressor 14 Nitrogen Reference Signs List 15 steam 16 oxygen 17 desulfurization device 18 nitrogen production device 20 air 21 coal 51 gas turbine 51 52 exhaust gas 52 53 exhaust heat boiler 54 steam 55 steam turbine 56 atmosphere 57 air compressor 58 air separator 59 nitrogen 60 oxygen compressor 61 oxygen 62 Coal 63 Gasifier 64 Generated gas 65 Nitrogen compressor 66 Combustor

Claims (4)

(57) [Claims] 1. A gasifier for gasifying coal, a gas cooler for cooling a gas generated by the gasifier, a gas purifier for purifying the generated gas, a gas turbine using the generated gas as a fuel, and a gas turbine. An exhaust gas boiler that generates steam by exchanging heat with exhaust gas of a turbine, a steam turbine driven by steam from the exhaust gas boiler, and a device that pressurizes an inert gas, and a generator is generated by the gas turbine and the steam turbine In an integrated coal gasification combined cycle power plant that drives and generates electricity, the pressurized inert gas is introduced into a gas cooler as a cooling medium to perform heat exchange, and the heated inert gas is introduced into a gas turbine through a combustor. Characteristic integrated coal gasification combined cycle power plant. 2. An integrated coal gasification combined cycle power plant according to claim 1, wherein the inert gas is nitrogen gas generated from an air separation device. 3. The integrated coal gasification combined cycle power plant according to claim 1, wherein the inert gas is nitrogen gas generated from a nitrogen production device. 4. The integrated coal gasification combined cycle plant according to claim 1, wherein the inert gas is an exhaust gas from a gas purification device.