JPH0718350B2 - Integrated coal gasification combined cycle power plant - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an air-oxidized coal gasification combined cycle power generation plant, which extracts gas from a compressor of a gas turbine and further pressurizes it with a boost compressor to produce coal gasification. The present invention relates to a system for supplying air to a furnace.

[Conventional technology]

Japanese Patent Application Laid-Open No. 57-59993 discloses this type of combined power plant.
It is well known in the art.

Including the above-mentioned known technology, conventionally, air to a coal gasification furnace is generally extracted from a compressor of a gas turbine, cooled by an intermediate air cooler, and then pressurized by a boost compressor to a coal gasification furnace. Is being supplied. In the above-mentioned known example, the heat retained by the bleed air from the compressor of the gas turbine is wasted to the outside of the system in the intermediate air cooler, resulting in heat loss in the plant.

[Problems to be solved by the invention]

In a coal gasification combined cycle power generation plant composed of a pressurized air oxidation coal gasification furnace and a combined cycle power generation plant, air which is a gasifying agent of the coal gasification furnace is extracted from a compressor of a gas turbine and boosted by a booster compressor. It is supplied to the coal gasifier after the pressure is raised by. It is possible to supply the air supplied to the coal gasification furnace from the compressor of the gas turbine without extracting it from the compressor of the gas turbine, but it is possible to use the compressor of the gas turbine rather than the compressor of a small capacity installed separately. Is more efficient (that is, less power is required for compression), the air to the coal gasification furnace is generally supplied by a system that bleeds air from the compressor of the gas turbine and further boosts the pressure by the boost compressor. .

When the pressure ratio and the air weight flow rate in the compressor are the same, the power of the booster compressor becomes smaller as the volume flow rate of air becomes smaller. Therefore, if the air temperature at the compressor inlet is high,
In order to reduce the volumetric flow, it is better to cool as much as possible. On the other hand, the air at the compressor outlet of the gas turbine is about 390 ° C, which is a fairly high temperature. Therefore, the bleed air from the compressor of the gas turbine is once cooled to reduce the volumetric flow rate of air and then sent to the boost compressor to reduce the power consumption of the boost compressor.

For the above reasons, in the above-mentioned conventional technology, an air cooler is installed upstream of the booster compressor, and consideration is given to reducing the power of the booster compressor, but the heat quantity of the high-temperature bleed air from the compressor of the gas turbine is There was a problem that the heat loss of the plant was large because no consideration was given to the effective use of the plant.

An object of the present invention is to provide an integrated coal gasification combined cycle power plant that can reduce heat loss in a system that supplies air from a compressor of a gas turbine to a gasification furnace.

[Means for solving problems]

In the coal gasification combined cycle power generation plant provided with the pressurized air-oxidized coal gasification furnace, the gas turbine, the exhaust heat recovery boiler, and the steam turbine, and the step-up compressor, A gas / gas heat exchanger is provided for performing heat exchange between the bleed air from the turbine compressor and the air sent from the booster compressor, and (b)
This is achieved by providing an air cooler that cools the intake air of the booster compressor and that uses the water supplied to the exhaust heat recovery boiler as the heat absorbing substance.

[Action]

In the combined cycle power plant configured as described above, the high temperature air of about 390 ° C at the compressor outlet of the gas turbine is cooled to about 190 ° C by the gas / gas heat exchanger at the outlet of the gas turbine compressor, and at the same time, By heating the air at the outlet of the booster compressor, its sensible heat is given to the air supplied to the gasification furnace to recover the heat. Further, the sensible heat is supplied to the exhaust heat recovery boiler by heating the supply water at the same time as it is cooled down to about 50 ° C. by the air cooler supplied with water at about 30 ° C. It is given to the water supply to recover heat. The air that exits the air cooler that uses the supply water as a cold heat source is further cooled to about 40 ° C by the air cooler using the external cooling water installed at the inlet of the boost compressor, and then sent to the boost compressor. . The air sent to the booster compressor is boosted by the booster compressor, the temperature rises due to adiabatic compression and becomes air at about 150 ° C, and the gas / gas heat exchanger is further extracted by the gas turbine compressor bleed air. After being heated to about 350 ℃, it is supplied to the coal gasification furnace.

As described above, the sensible heat of the air conventionally discarded to the outside in the air cooler is recovered by the heat supplied to the air supplied to the coal gasification furnace and the waste heat recovery boiler,
The plant thermal efficiency is improved.

〔Example〕

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

Before explaining the embodiment of the present invention, the principle of the present invention will be described with reference to FIG.

The coal 2 and the air 3 are supplied to the coal gasification furnace 1, and the coal and the air react in the coal gasification furnace 1 to generate a high-temperature crude product gas 4. The high-temperature crude product gas 4 is cooled to a temperature required by the gas refining 6 by a gasification furnace heat recovery boiler 5, and at the same time, its sensible heat is recovered as steam.

The crude product gas cooled to about 400 ° C. is sent to the gas refining 6, where it is dusted and desulfurized to become a clean fuel gas 7.

The fuel gas 7 is sent to the combustor 9 of the gas turbine 8 and generates high-temperature and high-pressure gas burned by the air from the compressor 10. The high temperature and high pressure gas generated in the combustor 9 is a gas turbine.
Generator that drives 11 and is connected to this gas turbine
Generates electrical output at 12.

The high-temperature exhaust gas 13 of the gas turbine 8 is sent to the exhaust heat recovery boiler 14, where the sensible heat of the gas is recovered as steam, and then discharged as a relatively low temperature gas (about 100 ° C.) to the outside of the system. .

The exhaust heat recovery boiler 14 includes a superheater 15, an evaporator 16 and a economizer 17. Water supply 18 to the exhaust heat recovery boiler 14 is first a economizer 17
Is supplied to the evaporator 16 and the gasification furnace heat recovery boiler 5. Saturated steam is generated in the evaporator 16, and is sent to the superheater 15 together with the saturated steam generated in the gasification furnace heat recovery boiler 5 to become superheated steam.
Supplied to 19. The steam turbine 19 drives a generator 20 to generate an electric output.

On the other hand, the steam that has worked in the steam turbine 19 is sent to the condenser 21, cooled by the cooling water, condensed, and becomes condensed water. Condensed water of the condenser 21 is supplied as a water supply 18 to the exhaust heat recovery boiler 14 by a water supply pump 22.

The air 3 supplied to the coal gasifier 1 is a gas turbine 8
Part of the air compressed by the compressor 10 is extracted, pressurized by the boost compressor 23, and then supplied to the coal gasification furnace 1.

In this embodiment, a gas / gas heat exchanger 24 and an air cooler 25 are installed to cool the air sent to the boost compressor 23. The gas / gas heat exchanger 24 is the compressor 10 of the gas turbine 8.
The air cooler 25 is installed so as to exchange heat between the outlet air of the booster compressor 23 and the outlet air of the booster compressor 23, and the air cooler 25 is installed at the inlet of the booster compressor 23.

Although the extraction air from the compressor 10 of the gas turbine 8 is as high as about 390 ° C, the gas / gas heat exchanger 24 exchanges heat with the air of about 150 ° C from the step-up compressor 23 to about 190 ° C. To be cooled. The air exiting the gas / gas heat exchanger 24 is further cooled in the air cooler 25 by external cooling water. How much the air temperature at the outlet of the air cooler 25 can be lowered depends on the temperature of the external cooling water, but when using seawater of about 20 ° C for the external cooling water, the air temperature at the outlet of the air cooler 25 is It will be about 40 ℃. Since the air sent to the boost compressor 23 is adiabatically compressed by the boost compressor, the air temperature at the exit of the boost compressor is about 15
It will be about 0 ° C. The air exiting the booster compressor is heated by the gas turbine gas extraction in the gas / gas heat exchanger 24,
It reaches 350 ° C and is supplied to the coal gasifier 1.

According to the principle configuration of FIG. 1, the sensible heat of the air, which has been conventionally discarded to the outside, is recovered as the feed water to the gasification air 3 and the exhaust heat recovery boiler 5 which are supplied to the coal gasification furnace 1. As a result, the plant thermal efficiency can be improved.

The air sent from the gas turbine compressor 10 to the step-up compressor 23 is
In this example, in order to reduce the power of the step-up compressor 23, the temperature is cooled from about 390 ° C to about 40 ° C. The sensible heat for cooling the air is about 5.3% of the fuel heat input to the plant, that is, the coal heat input. Equivalent to. In the prior art, about 5.3% of this amount of heat was discarded to the outside, resulting in heat loss. However, in FIG. 1, as described above, the cooling sensible heat of the air must be recovered to the gasification air and the feed water. Improves plant thermal efficiency. The mechanism for improving the plant thermal efficiency will be specifically described below for each factor.

First of all, by recovering the cooling sensible heat of air to the air at the outlet of the step-up compressor 23, the temperature of the air sent to the coal gasification furnace is increased from 150 ° C to 350 ° C to improve the plant thermal efficiency. I'm drawing. In the coal gasification furnace 1, a gasification reaction is performed with coal and air to generate a crude product gas 4,
The temperature in the coal gasification furnace 1 is considerably high, for example, 1500 to 1700 ° C. in the spouted bed type gasification furnace. This is because the temperature in the coal gasification furnace must be set to the melting point of the ash or higher in order to discharge the ash in the coal gasification furnace to the outside as molten slag. The gasification reaction in the coal gasifier 1
Combustion Partial combustion (incomplete combustion), water-gas reaction, shift reaction, etc. are performed in a complicated manner, but the rate of combustion increases as the supply temperature of gasified air decreases. For example, assuming that the air temperature is 150 ° C. and 350 ° C., 150 ° C. air requires a larger amount of heat to raise the supplied air to the same gasification temperature. Therefore, 150
In the case of air at 0 ° C., in order to supply a larger amount of heat, it is necessary to increase the amount of supplied air and increase the ratio of combustion reaction in the gasification reaction. Therefore, the amount of heat converted to gas in the calorific value of coal supplied to the coal gasifier is reduced, and the calorific value of the crude product gas is reduced. Further, when the amount of air increases, the amount of crude product gas generated increases. On the other hand, the temperature of the crude product gas is 1500 to 1700 ℃ in the gasifier, and about 400 ℃ at the gasifier heat recovery boiler outlet, which is constant regardless of the gas amount. The amount of heat recovered in the boiler increases, and the amount of steam in the heat recovery boiler increases.

Therefore, the ratio of the heat quantity of the fuel gas and the steam supplied to the combined cycle power generation facility (which is composed of the gas turbine, the exhaust heat recovery boiler, and the steam turbine) increases as the temperature of the gasification air increases. In the combined cycle power generation facility, the fuel gas works in the gas turbine, and the exhaust gas generates steam to work in the steam turbine, whereas the steam works only in the steam turbine, so it is supplied to the combined cycle power generation facility. The higher the ratio of the heat quantity of the fuel gas to the total heat quantity, the higher the thermal efficiency of the combined cycle power generation facility. Therefore, the higher the temperature of the gasification air, the higher the proportion of fuel gas, and the higher the plant thermal efficiency.

On the other hand, when the temperature of the gasification air is high, the total amount of heat entering the combined cycle power generation facility also increases, so the output of the combined cycle power generation facility increases and the plant thermal efficiency improves.

As described above, when the temperature of the gasification air rises, the thermal efficiency of the plant is improved due to the effect of increasing the total heat quantity to the combined cycle power generation facility and the effect of increasing the ratio of the fuel gas heat quantity.

The relationship between the temperature of the gasification air and the plant thermal efficiency is shown in FIG. The horizontal axis represents the temperature of air supplied to the coal gasifier, and the vertical axis represents the deviation in plant thermal efficiency.

Compared to the case where gasification air is supplied at about 150 ° C according to the conventional technique, the gasification air is about 350
When it is supplied at ° C, the plant thermal efficiency is improved by about 4.2% (relative value).

Next, a first embodiment of the present invention will be described with reference to FIG. However, since the fuel system from the coal gasification furnace 1 to the gas turbine 8 and the steam system of the exhaust heat recovery boiler 14 have the same configurations as those in FIG. 1, description thereof will be omitted, and the air system will be described next.

In the present embodiment, the gas / gas heat exchanger 24 that exchanges heat with the extraction air of the compressor 10 of the gas turbine 8 and the air at the outlet of the booster compressor 23.
And an air cooler 26 for supplying water to the exhaust heat recovery boiler 14. Compared with FIG. 1, the point that the feed water 18 to the exhaust heat recovery boiler 14 is used for cooling the air cooler 26 is different. The temperature of each part of the air sent from the compressor 10 of the gas turbine 8 to the coal gasification furnace 1 is the same as that in FIG. In the present embodiment, instead of using the external cooling water in the air cooler 26, the water is supplied to the exhaust heat recovery boiler 14. Therefore, the sensible heat of the air that has been discarded to the outside in FIG. Since heat can be recovered, the amount of evaporation of the exhaust heat recovery boiler 5 increases. Therefore, compared with FIG. 1, the amount of steam to the steam turbine 19 increases, the steam turbine output increases, and the plant thermal efficiency improves.

Next, the effect of recovering the cooling sensible heat of the air to the water supply to the exhaust heat recovery boiler 5 in the above-described first embodiment (FIG. 2) will be described.

As shown in the above-mentioned known art, in the prior art, the feed water to the exhaust heat recovery boiler is heated by the feed water heater after leaving the condenser and is supplied to the exhaust heat recovery boiler. The heat source of the feed water heater is bleed air from the steam turbine, and the steam turbine output is reduced by taking bleed air for heating the feed water from the steam turbine. In the present embodiment, the extraction of the steam turbine is not used for heating the feed water, but the sensible heat for cooling the air is used. Therefore, the extraction of the steam turbine can be eliminated and the output of the steam turbine can be increased. Therefore, the plant output is increased and the plant thermal efficiency is improved.

The relationship between the outlet water temperature of the air cooler and the plant thermal efficiency
Shown in the figure. The air-cooler outlet feed water temperature is about 33 ° C which is the condenser outlet temperature (that is, when the heat recovery in the air-cooler is 0) to about 60 ° C. At the feed water temperature of 60 ° C, the plant thermal efficiency improvement is about 0.6%. However, the plant thermal efficiency improvement amount does not increase above 60 ° C.

In the waste heat recovery boiler, in order to prevent condensation in the economizer and white smoke in the chimney, the feed water temperature at the inlet of the economizer needs to be generally about 60 ° C or higher. We are taking measures. Therefore, up to the feed water temperature of 60 ° C, there is an effect of improving the plant thermal efficiency by recovering the cooling sensible heat of air to the feed water, but the plant thermal efficiency improvement amount does not increase even if the feed water temperature is 60 ° C or higher.

From the above, in the principle configuration shown in Fig. 1, about 55% of the cooling sensible heat of the air is recovered to the gasification air to improve the plant thermal efficiency by about 4.2%. Further, in the embodiment shown in FIG. 2, by recovering the cooling sensible heat of air to both the gasification air and the feed water, the plant thermal efficiency improvement of about 4.2% by the temperature rise of the gasification air, In addition, the plant thermal efficiency can be improved by about 0.6% by heating the supply water, and the plant thermal efficiency can be improved by about 4.8% by combining the two.

Next, a second embodiment of the present invention will be described with reference to FIG.

In this embodiment, a gas / gas heat exchanger for exchanging heat between the extraction air of the compressor 10 of the gas turbine 8 and the air at the outlet of the booster compressor 23.
24 and an air cooler 26 by supplying water to the exhaust heat recovery boiler 14
And an air cooler 25 using external cooling water. In the principle configuration of FIG. 1 and the embodiment of FIG. 2, in addition to the gas / gas heat exchanger 24, either one of the air cooler 26 by the water supply or the air cooler 25 by the external cooling water is installed. On the other hand, in the embodiment of FIG. 3, in addition to the gas / gas heat exchanger, the air cooler 26 by the water supply and the air cooler by the external cooling water are used.
The difference is that both 25 and 25 are installed.

The extracted air of about 390 ° C. from the compressor 10 of the gas turbine 8 exchanges heat with the air of about 150 ° C. from the step-up compressor 23 in the gas / gas heat exchanger 24 and is cooled to about 190 ° C. . gas/
The air exiting the gas heat exchanger 24 is further cooled to about 50 ° C. by the feed water in the air cooler 26, and at the same time, the feed water is heated, and the sensible heat is recovered by the feed water. The air discharged from the air cooler 26 is further cooled by the air cooler 25 to 40 ° C. by the external cooling water.
It is cooled to some extent and sent to the boost compressor 23. Air is boosted in the booster compressor 23, and the air at the outlet of the booster compressor is about 15
After reaching 0 ° C. and further heated to about 350 ° C. by the gas / gas heat exchanger 24, it is supplied to the coal gasification furnace 1.

〔The invention's effect〕

As described above in detail, according to the integrated coal gasification combined cycle power plant of the present invention, it is possible to reduce the heat loss of the air system fed from the compressor of the gas turbine to the gasification furnace. It contributes to the improvement of the thermal efficiency of the integrated coal gasification combined cycle power plant as a whole.

[Brief description of drawings]

FIG. 1 is a system diagram for explaining the principle of the present invention, FIG. 2, FIG.
FIG. 4 is a system diagram showing the first and second embodiments of the present invention, FIG. 4 is a graph showing the action and effect according to the principle shown in FIG. 1, and FIG. 5 is a diagram showing the action and effect of the embodiment shown in FIG. It is a graph. 1 ... Coal gasifier, 2 ... Coal, 3 ... Air, 4 ...
Crude gas, 5 ... Gasifier heat recovery boiler, 6 ... Gas refining, 7 ... Fuel gas, 8 ... Gas turbine, 9 ... Combustor, 10 ... Compressor, 11 ... Gas turbine, 12 ... Generator, 13 ... Exhaust gas, 14 ... Exhaust heat recovery boiler, 15 ... Superheater, 16 ... Evaporator, 17 ... Economizer, 18 ... Water supply, 19 ...
Steam turbine, 20 ... Generator, 21 ... Condenser, 22 ... Water pump, 23 ... Boost compressor, 24 ... Gas / gas heat exchanger, 25 ... Air cooler, 26 ... Air Cooler.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Takeshi Yokosuka Kenshi Yokosuka 4-6 Kanda Surugadai, Chiyoda-ku, Tokyo Inside Hitachi, Ltd. (72) Inventor Nobuo Nagasaki 3-2-1, Saiwaicho, Hitachi, Ibaraki Engineering Co., Ltd. (56) Reference JP-A-62-186018 (JP, A)

Claims (2)

[Claims] Claims: 1. A coal gasification combined cycle power plant provided with a pressurized air-oxidized coal gasification furnace, a gas turbine, an exhaust heat recovery boiler, and a steam turbine, and a coal gasification combined cycle power plant provided with a booster compressor. A gas / gas heat exchanger for exchanging heat between the extracted air from the gas turbine compressor and the air sent from the booster compressor is provided, and (b) air cooling for cooling the intake air of the booster compressor. An integrated coal gasification combined cycle power plant, which is provided with an air cooler that uses water supplied to an exhaust heat recovery boiler as an endothermic substance. 2. A second air cooler according to claim 1, further comprising: a second air cooler for further cooling the air cooled by the air cooler with external cooling water and sending the booster compressor. Integrated coal gasification combined cycle power plant.