WO2002020952A1

WO2002020952A1 - Partially-gasified air-preheated and coal-fired combined cycle power generation system and power generation method

Info

Publication number: WO2002020952A1
Application number: PCT/CN2001/001200
Authority: WO
Inventors: Anpei Han
Original assignee: Anpei Han
Priority date: 2000-07-28
Filing date: 2001-07-24
Publication date: 2002-03-14
Also published as: CN1277339A; CN1162643C; AU2002223391A1

Abstract

The present invention relates to a partially-gasified air-preheated coal-fired combined cycle power generation system and power generation method, the system is constituted mainly by a coal gas block, which includes a pressured fluidized bed gasifier, gas cooler/steam superheater and ceramic filter, and their auxiliaries, coal is partially gasified in the gasifier while using air and steam as gasifying medium; a boiler block which includes low-multiplex circulation fluidized bed boiler and waste-heat boiler, and their auxiliaries; a gas turbine block which comprises compressor, prepositive combustion chamber, gas turbine, electrical generator and their auxiliaries; a steam turbine block, it comprises steam turbine, electrical generator and their auxiliaries. The optimal combination of the above parts constitute a coal-fired power generation system which can make electrical power with high efficiency, low pollution and low cost.

Description

Partial gasification air preheating coal-fired combined cycle power generation system and method

The present invention relates to a gas / steam combined cycle power generation system and method (PGACC), and particularly to a coal-fired gas / steam combined cycle power generation system and method.

More specifically, the present invention relates to an optimized combined coal-fired combined cycle power generation system. It properly combines the two power generation cycles of coal gasification, combustion, desulfurization and purification, and gas / steam, so that it has higher power generation / power supply efficiency, a simpler system composition, less environmental pollution, and investment and operation and maintenance. Features such as lower cost.

The invention also relates to a dedicated gas cooler / steam superheater. It uses steam as a cooling medium to cool the gas to below 65 ° C, so that ceramic dust can be used to filter out dust and condensed alkali metals and other particles, so that the gas meets the requirements of gas turbines. The steam is superheated to a set temperature while cooling the gas to drive the steam turbine generator set to generate electricity. The steam comes from the gas turbine waste heat boiler and duplex circulating fluidized bed boiler of this system. In this way, the sensible heat of high-temperature gas is used reasonably, and the steam can be superheated to a very high temperature without being restricted by the exhaust temperature of the gas turbine.

The invention also relates to a dedicated atmospheric circulating fluidized bed boiler. The boiler uses semi-coke produced by a coal gasifier as fuel to produce two working fluids, namely high-temperature compressed air and high-pressure saturated steam. / Calcium oxide further completes the coal / semi-coke removal process. Due to the use of a duplex circulating fluidized bed boiler, the gasifier in this system can avoid the inefficient stage of the coal gasification process, thereby simplifying its structure and increasing its output. Because more than 60% of the heat released by the combustion of semi-coke is used to heat the compressed air, the gas turbine / turbine power ratio and cycle thermal efficiency of the combined cycle can be improved without using a special heat-resistant alloy.

The invention also relates to a reasonable desulfurization process. In a pressurized fluidized bed gasifier, the desulfurization reaction will generate CaS and deposit in the semi-coke of the dense phase layer and the fly ash of the gas stream. These semi-coke and fly ash are then sent to a circulating fluidized bed boiler with the remaining limestone / calcium oxide. In the fluidized bed of the boiler, the unreacted sulfur in CaS and semi-coke will continue to react with the limestone / calcium oxide. Ca S 04 is formed and discharged with the circulating fluidized bed boiler bed slag. Background technique

It is known that the integrated coal gasification combined cycle system (I GCC), which has been initially commercialized, generally uses oxygen as a gasification agent to gasify all coal at high temperatures. As a result, the entire system is complex, with high power consumption and high investment and operation and maintenance costs.

It is known that the pressurized fluidized bed combined cycle system (PFBC-CC), which has been initially commercially operated, burns and desulfurizes coal in a pressurized fluidized bed, and the high-temperature and high-pressure flue gas generated is used to drive a gas turbine to generate electricity. Due to the difficulty of purifying the flue gas, the corrosion and abrasion of the gas turbine is large, which affects the life of the gas turbine. And because the temperature of the high-temperature and high-pressure flue gas generated by the pressurized fluidized bed is limited by the working conditions of the pressurized fluidized bed, it cannot be too high, so it is difficult to improve the efficiency of the gas cycle. Mingming purpose

In response to the above problems, in some countries, efforts are being made to find a clean coal-fired combined cycle power generation system with a simpler system, less self-use electricity, and more reliability.

One of the objectives of the present invention is to provide a clean coal-fired combined cycle power generation system that partially gasifies coal with air. Partial gasification of coal and combustion of the remaining coke after gasification are completed in a pressurized fluidized bed gasifier and a duplex fluidized bed boiler, respectively. Since only part of the coal is gasified, the inefficient stage of the coal gasification process can be avoided, so the structure of the gasifier is simplified and the gas output is increased. Since the dual-use boiler is also used to heat the compressed air of the gas turbine, the gas turbine / turbine power ratio of the combined cycle can be increased. And because the desulfurizer (limestone) can be used to desulfurize the coal during the gasification process and the combustion of semi-coke, it can reduce the sulfur content of the coal gas and the sulfur dioxide in the flue gas of the duplex boiler. The boiler flue gas is processed outside the furnace.

Another object of the present invention is to provide a clean coal-fired combined cycle power generation system that partially gasifies coal with air. The combination of its gas cooler and steam superheater reduces the amount of steam generated by the additional cooling water to cool the gas, so as to improve the system's gas turbine / turbine power ratio and thus improve the efficiency of the power plant.

The third object of the present invention is to superheat the saturated steam of the waste heat boiler and the duplex boiler by using the high-temperature thermal energy of the gas. Therefore, the steam system may adopt subcritical or supercritical parameters without being restricted by the exhaust temperature of the gas turbine. There is also no need to add additional fuel to the waste heat boiler, so the structure of the waste heat boiler is simple. The fourth object of the present invention is to use a circulating fluidized bed boiler to burn semi-coke generated from a fluidized bed gasifier. The boiler uses normal pressure, 'low-rate circulation, and no steam superheater is arranged. The furnace's water-cooled wall is covered with a layer of wear-resistant refractory bricks, and an air heater is arranged above the furnace. As a result, most of the semi-coke combustion heat (more than 60%) is used to heat the air. In this way, the compressed air of the gas turbine unit can be heated to 600 ° C-8 00 ° C, so that the system's gas turbine / turbine power ratio and power plant efficiency can be improved without using expensive high-temperature heat-resistant alloys.

The fifth object of the present invention is to obtain the best benefit of the entire system by rationally configuring each part of the system. With relatively simple systems, relatively simple equipment and structures, and lower investment, higher power generation / power supply efficiency and less environmental pollution are achieved. Technical solution of the present invention

The object of the present invention can be achieved according to the following system and method:

A partially gasified air preheating combined cycle power generation system is characterized in that the composition structure is: a pressurized fluidized bed gasification furnace and its auxiliary equipment, which partially gasify coal and generate crude coal gas and semi-coke; and special coal gas cooling Device / steam superheater for cooling the gas produced by the gasifier and superheating the saturated steam generated by the system at the same time; the gas purification device includes a cyclone separator in front of the gas cooler and a ceramic filter behind the gas cooler, It is used to purify crude gas to meet the requirements of gas turbines. Duplex (hot air / steam) atmospheric pressure circulating fluidized bed boiler and its auxiliary equipment are used for the semi-coke produced by the ash gasifier to obtain high-temperature compressed air. And high-pressure saturated steam; the gas turbine generator set and its auxiliary equipment use high-temperature and high-pressure gas expansion generated by the combustion of purified gas and high-temperature compressed air for power generation; waste heat boilers use gas turbine exhaust to generate high-temperature and high-pressure steam, and are cooled by gas Heater / steam superheater sends steam turbine after overheating; steam turbine generator set and its auxiliary equipment ,. Duplex pot Steam from furnaces and waste heat boilers is overheated by gas coolers / steam superheaters and expanded by steam turbines to generate electricity.

A partially gasified air preheating combined cycle power generation method, characterized by: pulverized coal and demineralized coal (limestone) using air / steam as a gasification agent, and partially passing gas through a pressurized fluidized bed gasification furnace Desulfurization and desulfurization to produce low-calorific value gas and semi-coke; the low-calorific value gas is cooled, dust-removed and purified and sent to the front combustion chamber of the gas turbine; In In the boiler, more than 60% of the heat released by the combustion of the semi-coke is used to heat the compressed air of the gas turbine compressor, and less than 40% of the heat is used to generate the saturated steam; The combustion chamber and the low-calorific value gas are burned to generate high-temperature gas, which is expanded by the gas turbine to generate power, and the gas turbine exhaust gas is generated by the waste heat boiler to generate high-pressure steam; the high-pressure saturated steam generated by the duplex boiler is sent to the high-pressure steam generated by the waste heat boiler After the gas cooler / steam superheater overheats, the steam turbine expands to generate power.

The above system is further characterized in that the special gas cooler / steam superheater is a shell and tube heat exchanger, outside the tube is high-temperature gas, and inside the tube is high-pressure steam (cooling medium). A dedicated air heater without a steam superheater is arranged in the duplex (hot air / steam) atmospheric pressure circulating fluidized bed boiler, and a wear-resistant refractory brick is laid on the water-cooled wall of the furnace to reduce the heat absorption during evaporation and ensure that Most of the heat released from the combustion of semi-coke is used to heat the air.

The above method is further characterized in that the steam generated by the system is used to cool the high-temperature gas to a temperature convenient for purification through a gas cooler / steam superheater, and at the same time, the steam is superheated to facilitate the improvement of system efficiency. By using the dual-substance circulating fluidized bed boiler, the semi-coke embers produced by the gasification furnace can be used, and more than 60% of the heat released from its combustion is used to heat the compressed air to 600 ° C-800 ° C, At the same time, the residual limestone / CaO of the gasifier can be used to convert the harmful CaS discharged with the semi-coke generated by the gasifier into the stable and harmless CaS04 in the duplex boiler. The pressurized fluidized-bed gasification furnace and the duplex fluidized-bed boiler can perform a high-efficiency desulfurization process that is connected to each other in order to effectively reduce the sulfur content of the gasifier gas and the SO ₂ in the boiler flue gas. Content, so there is no need to use a special out-of-furnace desulfurization device for gas and flue gas desulfurization. Effect of the invention.

Such a reasonably combined coal-fired combined cycle power generation system and method can achieve the goals of high efficiency, low pollution and low cost power generation.

The invention is further described below with reference to the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a system structure of the present invention. DETAILED DESCRIPTION OF THE INVENTION

The gas island (1) has a pressurized fluidized bed gasifier (2), and the pulverized coal and limestone are added to the furnace for partial gasification and desulfurization. The generated gas is separated by the cyclone (3), and then enters the gas cooler / steam superheater (4) to cool to 650. C or less. The ceramic filter then removes dust, alkali metals and other solid particles and sends them to the combustion chamber (32) in front of the gas turbine. The semi-coke and residual limestone / calcium oxide are appropriately cooled and depressurized and sent to a circulating fluidized bed boiler.

The boiler island (10) contains a circulating circulating fluidized bed boiler (1 1). The depressurized and properly cooled semi-coke and limestone are sent to the boiler hearth (12). The semi-coke combustion air is passed by a blower (17). The air preheater (16) is fed into the furnace. The high-temperature flue gas generated by combustion passes through the air heater (1 3) above the furnace, and the low-temperature flue gas after heating the compressed air is separated by gas / solid through a cyclone (14). Most of the fly ash was separated and returned to the furnace. The separated low-temperature flue gas passes through the economizer (15), air preheater (16), and dust collector (19), and is finally discharged into the chimney by the induced draft fan (20). The waste heat boiler (21) in the boiler island uses the gas turbine exhaust gas to heat the boiler feed water and generate high-pressure steam (saturated or low superheat), and the steam from the circulating fluidized bed boiler is fed into the gas after it is collected in the steam drum (18) Cooler / steam superheater (4) is too hot.

The front combustion chamber (32) in the gas engine island (30) is used to burn low-calorific gas, and the high-temperature gas generated by the combustion of the preheated compressed air and the low-calorific gas is used to drive the gas turbine (33) and its generator set (34) Power generation.

The steam turbine generator sets (41) and (42) in the steam turbine island (40) are driven by high-temperature and high-pressure steam from a gas cooler / steam superheater and generate electricity. A small amount of high pressure extraction steam from the steam turbine (41) is supplied to the pressurized fluidized bed gasifier (2), and a small amount of low pressure extraction steam is supplied to the deaerator (45) to deoxidize the feed water. After the boiler feed water passes the deaerator (45), it is sent to the waste heat boiler U 1) and the circulating fluidized bed boiler (1 1) by the feed water pump (46).

Claims

Rights request

1. A partially gasified air preheating combined cycle power generation system, characterized in that the composition structure is: a pressurized fluidized bed gasification furnace and its auxiliary equipment, which partially gasify coal to produce crude coal gas and semi-coke; Gas cooler / steam superheater, used to cool the gas produced by the gasifier and at the same time superheat the saturated steam generated by the system;

A gas purification device, including a cyclone separator in front of the gas cooler and a ceramic filter behind the gas cooler, for purifying crude gas to meet the requirements of the gas turbine;

Duplex working-pressure atmospheric circulating fluidized bed boiler and its auxiliary equipment are used for the semi-coke produced by the ash-burning gasifier to obtain high-temperature compressed air and high-pressure saturated steam;

The gas turbine generator set and its auxiliary equipment use high-temperature and high-pressure gas expansion generated by the combustion of purified coal gas and high-temperature compressed air for power generation;

The waste heat boiler uses the gas turbine exhaust to generate high-temperature and high-pressure steam, and sends it to the steam turbine after it is overheated by the gas cooler / steam superheater;

Steam turbine generator sets and their auxiliary equipment, steam produced by duplex boilers and waste heat boilers are overheated by gas coolers / steam superheaters, and then expanded by steam turbines to generate power.

2. A partially gasified air preheating combined cycle power generation method, characterized in that:

'' The pulverized coal and desulfurizing agent use air / steam as a gasifying agent, and are partially gasified and straightened by a pressurized fluidized-bed gasifier, generating low-calorific value coal gas and semi-coke;

The low-calorific-value gas is cooled, dust-removed, and purified, and then sent to the front combustion chamber of the gas turbine; the semi-coke is embossed by a dual-pressure atmospheric circulating fluidized bed boiler, and in the boiler, the heat released by the semi-coke combustion More than 60% is used to heat the compressed air of the gas turbine compressor, and less than 40% of the heat is used to generate saturated steam;

The high-temperature compressed air heated by the duplex boiler is sent to the front combustion chamber of the gas turbine and the low-calorific value gas is burned to generate high-temperature gas, which is expanded by the gas turbine to generate power, and the exhaust gas of the gas turbine passes through the waste heat boiler to generate high-pressure steam;

The high-pressure saturated steam generated by the duplex boiler and the high-pressure steam generated by the waste heat boiler are sent to a gas cooler / steam superheater to be overheated and expanded by a steam turbine to generate power.

3. The combined cycle power generation system according to claim 1, wherein: the special coal gas cooler / steam superheater is a shell-and-tube heat exchanger, outside the tube is high-temperature gas, and inside the tube is high-pressure steam.

4. The combined cycle power generation system according to claim 1, characterized in that: a special air heater without a steam superheater is arranged in the Han working medium normal pressure circulating fluidized bed boiler, and is laid on the water wall in the furnace Wear-resistant refractory bricks to reduce the heat absorption of evaporation, to ensure that most of the heat released by semi-coke combustion is used to heat the air.

5. The combined cycle power generation method according to claim 2, characterized in that the steam generated by the system itself is passed through a gas cooler / steam superheater .. The high temperature gas is cooled to a temperature convenient for purification, and at the same time the steam is Overheated to help improve system efficiency.

6. The combined cycle power generation method according to claim 2, characterized in that: using the duplex fluid circulating fluidized bed boiler, the semi-coke ash produced by the gasification furnace can be used, and the heat released by the combustion can be obtained 6 0 ° /. The above is used to heat compressed air to 600. C- 8000 ° C. At the same time, the residual limestone / CaO of the gasifier can be used to convert the harmful CaS discharged by the coke into the stable and harmless in the duplex boiler. CaS04.

7. The combined cycle power generation method according to claim 2 or 6, characterized in that: a high-efficiency desulfurization process connected in front and back can be performed in the pressurized fluidized bed gasifier and the duplex fluidized bed boiler, respectively. In order to effectively reduce the sulfur content of the gasifier gas and the content of SO ₂ in the boiler flue gas, there is no need to use a special desulfurization device outside the furnace to desulfurize the gas and flue gas.