AU2011349905A1

AU2011349905A1 - A hybrid power generation system and method based on solid fuel pyrolisis and char combustion

Info

Publication number: AU2011349905A1
Application number: AU2011349905A
Authority: AU
Inventors: Jinghai Li; Junfeng Li; Songgeng LI; Weigang LIN; Wenli SONG; Jianzhong Yao
Original assignee: Institute of Process Engineering of CAS
Current assignee: Institute of Process Engineering of CAS
Priority date: 2011-05-17
Filing date: 2011-12-16
Publication date: 2012-12-06
Anticipated expiration: 2031-12-16
Also published as: JP2013534988A; JP5632075B2; CN102261271A; DE112011100506T8; WO2012155314A1; DE112011100506T5; AU2011349905B2; CN202165134U

Abstract

Abstract This invention relates to a hybrid power generation system and method based on solid fuel pyrolysis and char combustion, the system includes a pyrolyzer (1) for pyrolyzing solid fuel to produce gaseous, liquid and solid char fuels, in 5 which the gaseous and the liquid fuels are separated through a condenser (2), wherein, the separated gaseous and liquid fuels are respectively introduced into a gaseous fuel purifier (3) and a liquid fuel purifier (4) for dust removing and desulfurization; and the solid char fuel is supplied into a boiler (5) for combustion to generate steam; a gas turbine (7) for burning gaseous or/and 10 liquid fuels to generate electricity; and a steam turbine (8) for using steam to generate electricity. In the present method, solid fuel is pyrolyzed to produce gaseous, liquid, solid char fuels, and the resulted gaseous, liquid and char fuels are respectively introduced into gas turbine and boiler to produce steam to generate electricity. The present invention effectively simplifies the process, 15 reduces the cost, and takes both advantage of the IGCC and ultra supercritical power generation, and so the power generation efficiency is significantly improved, not only can be used in large power plants, but also can be used in small power generation units with medium and high parameters.

Description

A hybrid power generation system and method based on solid fuel pyrolysis and char combustion Field of the invention 5 This invention relates to the technical field of coal power generation, and particularly to a hybrid power generation system and method based on solid fuel pyrolysis and char combustion. Background of the invention The principle of coal power generation is using steam produced at high 10 temperature and high pressure to drive a steam turbine to generate electricity, the higher the temperature and pressure of the steam is, the higher efficiency of power generation is. Under the conditions of 374.15 0C, 22.115MPa, the density of steam will increase to be substantially identical with that of liquid water, these conditions are called critical parameters of 15 water; the parameters which are higher are called supercritical parameters of water; and when the temperature and pressure is higher than 6000C and 25-28MPa, these conditions are called Ultra supercritical parameters of water. The typical parameters of a power generation system under subcritical 20 conditions are 16.7MPa/5380C/538 0 C and the power generation efficiency is about 38%; the pressure of the main steam of a power generation system under supercritical conditions is usually around 24MPa, the temperature of the main steam and reheated steam is 538-560 o C, the typical parameters of a power generation system under supercritical conditions are 25 24.1 MPa/538 0 C /538oC, and the corresponding power generation efficiency thereof is about 41 %; the pressure of the main steam of a power generation system under ultra supercritical conditions is 25-31 MPa, the temperature of the main steam and the reheated steam is 580~610oC, and the power generation efficiency thereof is about 45%. 1 Gas turbine combined cycle power generation is to use gaseous or liquid fuel in a gas turbine for power generation firstly, and then, the heat of the discharged high-temperature flue gas is recovered in a heat recovery steam generator (HRSG) to produce steam which is introduced into a 5 steam turbine to generate electricity. The gas turbine combined cycle system uses both of Brown cycle and Rankine cycle, and its power generation efficiency is close to 57-58%. The system discharges fewer dust and sulfur dioxide, and nitrogen oxide at 10-25ppm. IGCC is an abbreviation of the integrated gasification combined cycle 10 power generation system. Firstly, coal is gasified to produce gas, after the gas being purified, the gas is supplied into a gas turbine for generating electricity. Steam generated from HRSG is introduced into a steam turbine for generating electricity. By integrating highly efficient steam and gas turbine combined cycle power generation system with clean coal 15 gasification technology, IGCC technology features high power generation efficiency and environmental friendly, and so it is a promising clean coal power generation technology. According to current technology level, the net power generation efficiency of IGCC is up to 43-45%, the amount of pollutants emissions is only 1/10 of conventional coal-fired power plants; 20 The desulfurization efficiency can reach 99%, the emission of SO 2 is about 25mg/Nm 3 ; nitrogen oxides emission is only 15-20% of conventional coal-fired power plants; the amount of water consumption is only 1/2-1/3 of conventional power plants, so it is beneficial to the environment. However, the construction cost of IGCC power plants is higher than that of pulverized 25 coal fired power plants, its construction cost is much higher than that of a 1000MW power generation units under ultra supercritical conditions; In addition, IGCC system is more complex, which becomes an obstacle to its further development. 2 In China, coal with the high volatile accounts for more than 80% of coal resources, wherein about 13% is lignite, 42% is sub-bituminous and 33% is bituminous coal. The volatile matter of coal is rich in hydrocarbon, which can be converted into gas directly. 5 A lot of research and development about coal pyrolysis technology has been carried out internationally in order to obtain pyrolysis oil or upgraded fuels. Examples of technical solutions raised include TOSCOAL rotary kiln pyrolysis technology, Lurgi-Ruhr moving bed pyrolysis technology, CEOD fluidized bed pyrolysis and ECOPRO entrained-flow bed fast pyrolysis 10 technology. However, with the large scale application of petroleum, the development of coal pyrolysis technology has been substantially ceased. As early as at the end of 50's, Chinese Academy of Sciences and the Dalian First Power Plant, the Changchun Automobile Manufacturing Plant jointly carried out industrial experiments of coal pyrolysis with solid heat 15 carrier integrated with combustion, and have obtained preliminary experimental results. However, after the discovery of Daqing oil field, further experiment was terminated. In the early 1980, Dalian University of Technology developed DG process, China Coal Research Institute developed multi-stage rotary kiln pyrolysis technology, etc. Recently, 20 because of the increasing demands for oil and gas resources in China, different coal pyrolysis processes and multi-generation techniques have been proposed, by Zhejiang University, Tsinghua University, Institute of Process Engineering and Institute of Coal Chemistry, Chinese Academy of Sciences, and so on, aiming to achieve multi-generation of heat, gas and 25 power at the same time. Institute of Process Engineering of Chinese Academy of Sciences has been engaged to realize clean and efficient utilization of coal by coal topping process (i.e., pyrolysis). In this process, it is found that the best way 3 to realize clean and efficient utilization of coal is coal pyrolysis staged conversion process. Ultra supercritical power generation technology makes gaseous and liquid components contained in coal burned directly, failing to make full use of them which has the potential to produce more power. IGCC 5 coal gasification process with a gasification efficiency of 80% is very complicated, which sets a ceiling for the power generation efficiency of the system. Moreover, the steam cycle of IGCC system cannot reach higher temperatures due to the limitation by the temperatures of the flue gas from the gas turbine, so the power generation efficiency of IGCC can only reach 10 43-45%. Therefore, the present application proposed a hybrid power generation system based on solid fuel pyrolysis and char combustion, in order to combine the advantages of IGCC and ultra supercritical power generation to achieve higher power generation efficiency through coal pyrolysis technology. 15 Summary of the invention Therefore, the object of the invention is to provide a hybrid power generation system and method based on solid fuel pyrolysis and char combustion. The object is achieved by pyrolyzing the solid fuel to obtain gaseous (pyrolyzed gas), liquid (tar) and solid (char) fuel through solid fuel 20 pyrolysis technology; condensing the resulted gaseous and liquid fuel and performing dust removing and desulfurization of the gaseous and liquid fuel separately, after which the gaseous and liquid fuel is introduced to a gas turbine for power generation; introducing the steam generated by burning the solid char fuel in a boiler and the steam generated from a heat recovery 25 steam generator(HRSG) into a steam turbine for power generation, thereby, the efficiency of coal power generation is increased. With a simple structure and low cost for establishing and operating, the present invention can be used in existing medium and small scale power units to improve the 4 efficiency of power generation, save energy and reduce emission. In order to realize the above object, the invention provides a hybrid power generation system based on solid fuel pyrolysis and char combustion, comprises: a pyrolyzer(1) for pyrolyzing the solid fuel to produce gaseous, 5 liquid and solid char fuel; a condenser(2), for separating the gaseous and liquid fuel; a gaseous fuel purifier(3), for performing dust removing and desulfurization for the gaseous fuel; a liquid fuel purifier(4), for performing dust removing and desulfurization for the liquid fuel; a boiler(5), for performing combustion of the solid char fuel to generate steam; a gas 10 turbine(7), for burning the gaseous or/and the liquid fuel to generate electricity ; a steam turbine(8), for generating electricity by using the steam. As an improvement of the above technical solution, the hybrid power generation system further includes a heat recovery steam generator(HRSG, 6), for generating steam by using the hot flue gas from the gas turbine(7) to 15 drive the steam turbine(8) to generate electricity. As another improvement of the solution, the hybrid power generation system further includes a HRSG(6), for generating steam by using the hot flue gas from the gas turbine(7) and introducing the steam into the boiler(5) so as to mix the introduced steam and the steam produced in the boiler(5), 20 and then the mixture is superheated and introduced into the steam turbine(8) to generate electricity, as shown in Fig.2; or the steam generated by the HRSG(6) is introduced into the boiler(5) to be superheated individually, after which it is introduced into the steam turbine(8) together with other steam from boiler to drive the steam turbine(8) to generate 25 electricity. In order to realize another object of the present invention, the invention provides a hybrid power generation method based on solid fuel pyrolysis and char combustion, includes the steps of: 1) feeding the solid fuel into a 5 pyrolyzer to be pyrolyzed so as to produce gaseous, liquid and solid char fuel; 2) condensing the gaseous and liquid fuel resulted from step) in a condenser so that the gas and liquid are separated, after which the gaseous and liquid fuel being performed dust removing, desulfurization 5 through a gaseous fuel purifier and a liquid fuel purifier separately, and then generating electricity by introducing the gaseous and/or liquid fuel into a gas turbine; 3)burning the char resulted from pyrolysis in a boiler to produce steam for driving a steam turbine to generate electricity. As an improvement of the above method, it further includes step 4): 10 introducing the hot flue gas from the gas turbine into a HRSG to produce steam for driving the steam turbine to generate electricity. As another improvement of the method, preferably the steam produced by the boiler burning char in step 3) and the steam generated from the HRSG in step 4) are respectively introduced into the same or different 15 steam turbines to generate electricity. As another improvement of the method, preferably the steam produced by the HRSG in step 4) is introduced into the boiler burning char, mixed and superheated with the steam in the boiler, and then introduced into the steam turbine to generate electricity; or the steam is introduced into the 20 boiler to be superheated individually, and then is introduced into the steam turbine to drive the steam turbine together with other steam from boiler to generate electricity. The above solid fuel includes coal, oil sands, oil shale or biomass. The pyrolysis includes simple pyrolysis, partial combustion pyrolysis, 25 partial gasification pyrolysis or combination thereof. The liquid fuel in step 2) is directly output as a product. The advantages of the invention lie in, the hybrid power generation system and its method based on solid fuel pyrolysis and char combustion 6 according to the present invention uses solid fuel pyrolysis technology to pyrolyze the solid fuel into gaseous(pyrolyzed gas), liquid(tar) and solid(char) fuel. The resulted gaseous and liquid fuels are used in a gas turbine for generating electricity. It takes full advantage of the benefit that 5 the efficiency of the gas turbine combined cycle power generation is higher than that of ultra supercritical power generation, while avoiding the complex coal gasification process in IGCC. The solid char fuel obtained from pyrolysis is also used in the boiler for combustion to generate steam with ultra supercritical parameters for driving a steam turbine to generate 10 electricity. Since the higher energy conversion efficiency in the pyrolysis process, which is about 95-97%, the hybrid power system can achieve an even higher power generation efficiency than IGCC and ultra supercritical power generation. Assuming that the efficiency of coal pyrolysis is 96%, and 30% of the 15 energy is contained in the gaseous and liquid fuel and the rest 70% of the energy is contained in the solid char, if the power generation efficiency of the gaseous and liquid fuel by using gas turbine combined cycle power system is 58-67%, the power generation efficiency of char combustion by using ultra supercritical generation system is 45%, then, the efficiency of 20 the hybrid power generation through coal pyrolysis and char combustion is about 47-50%, which is higher than 46% of IGCC and 45% of ultra supercritical power generation. However, compared with IGCC, the cost and complexity of the present invention is greatly reduced. In addition, there are a lot of medium and small scale coal thermal 25 power plants in China, which mainly use power generation system driven by steam produced from boiler and so the efficiency is very low, only about 36%. As the power generation efficiency of gas turbine has little change with the increase of the capacity of the gas turbine, about 30% of oil and 7 gas and about 70% of solid char can be obtained by pyrolysis with an efficiency of 96%. The char may be introduced into original power generation system, and the oil and gas can be used in the combined steam and gas turbine cycle power system to generate power with an efficiency of 5 56%, and so the efficiency of the whole system can be up to 42%. In short, according to the present invention, the liquid and gaseous fuel resulted from pyrolysis are used in the gas turbine power generation system; the steam produced by burning the solid char resulted from the pyrolysis, and the steam generated from the HRSG of the gas turbine are 10 used in the steam turbine for power generation, thereby the efficiency of power generation is increased. The system can be used not only in large power plants to realize maximum efficiency of currently existing coal fired power plants; but also in small power generation units operating at medium or high pressure parameters, which increases the power generation 15 efficiency of small power generation units by a larger magnitude, realizing the purposes of saving energy and reducing emission. Brief description of the drawings Figure 1 is the schematic diagram of hybrid power generation system based on solid fuel pyrolysis and char combustion according to the present 20 invention; Figure 2 is a schematic diagram showing the first embodiment of the hybrid power generation system based on solid fuel pyrolysis and char combustion according to the present invention; and Figure 3 is a schematic diagram showing the second embodiment of 25 the hybrid power generation system based on solid fuel pyrolysis and char combustion according to the present invention. Description of the reference numerals: 1-a pyrolyzer; 2-a condenser; 3-a gaseous fuel purifier; 4-a liquid fuel 8 purifier; 5-a boiler; 6-a heat recovery steam generator (HRSG); 7-a gas turbine; 8-a steam turbine Best modes for carrying out the present invention Hereafter, the present invention will be described with reference to the 5 drawings and the embodiments in further details. According to the present invention, a hybrid power generation system mainly includes: a pyrolyzer 1 for pyrolyzing the solid fuel to produce gaseous, liquid and solid char fuels; a condenser 2 for separating the gaseous and the liquid fuels; a gaseous fuel purifier 3 and a liquid fuel 10 purifier 4 for performing dust removing and desulfurization of the gaseous and liquid fuels, respectively; a gas turbine 7 for generating electricity by burning the gaseous or/and the liquid fuels; a HRSG 6 for producing steam by using the hot flue gas from the gas turbine 7; a boiler 5 for producing steam by burning the char fuel; and a steam turbine 8 for generating 15 electricity by using the steam. As shown in Fig.1, a hybrid power generation method based on solid fuel pyrolysis and char combustion according to the present invention includes the following steps: (1) feeding the solid fuel into a pyrolyzer 1 to be pyrolyzed so as to 20 produce gaseous, liquid and solid char fuels; (2) condensing the gaseous and liquid fuels resulted from step (1) in a condenser 2 so that the gaseous and liquids are separated, after which the gaseous and liquid fuels being performed dust removing, desulfurization through a gaseous fuel purifier 3 and a liquid fuel purifier 4 separately, and 25 then generating electricity by introducing the gaseous and/or liquid fuels into a gas turbine 7; (3) feeding the hot flue gas from the gas turbine 7 into a HRSG 6 to produce steam for driving a steam turbine 8 to generate electricity; 9 (4) burning the resulted char fuel in a boiler 5 to produce steam for driving the steam turbine 8 to generate electricity. The solid fuel mentioned in the step (1) refers to coal, oil sands, oil shale, biomass, etc. 5 The pyrolysis mentioned in the step (1) refers to simple pyrolysis, partial combustion pyrolysis, partial gasification pyrolysis or the combinations thereof. After being purified, the resulted liquid and gaseous fuels mentioned in the step (2) are completely or partially introduced into the same or different 10 gas turbines, or only the gaseous fuel is introduced into the gas turbine. The steam produced by the HRSG 6 mentioned in the step (3) and the steam produced by the boiler 5 mentioned in the step (4) are respectively introduced into the same or different steam turbines to generate electricity; or the former steam is introduced into the boiler 5 to be mixed with the 15 steam therein and then the mixture is introduced into the steam turbine 8 to generate electricity, as shown in Fig. 2; or the former steam is introduced into the boiler 5, and after being superheated individually, is finally introduced into the steam turbine 8 for driving it to generate electricity with other steam. 20 Embodiment 1 Fuels: bituminous coal with the higher volatile matter Implementing method: Firstly, the coal is fed into the pyrolyzer 1, where the coal is pyrolyzed to obtain the gaseous and liquid and solid char fuels; the resulted gaseous 25 and liquid fuels are condensed in the condenser 2 so as to be separated, then are respectively introduced into the gaseous fuel purifier 3 and the liquid fuel purifyier 4 for performing dust removing and desulfurization, after which are introduced into the gas turbine 7 for generating electricity; the 10 resulted solid char fuel discharged from the bottom of the pyrolyzer 1 is introduced into the boiler 5 to be burned to generate steam, at the same time, the steam produced by the HRSG 6 is also integrated into the steam-water system of the boiler 5, and the superheated steam produced 5 from the boiler 5 is supplied to the steam turbine 8 for generating electricity. As the steam produced by the HRSG 6 is integrated into the main steam system of the boiler 5, power generation can be realized by steam with higher parameters, and so the efficiency of power generation is further improved. 10 Assuming the ultra supercritical power generation efficiency is 45%, the power generation efficiency of a gas turbine is 40%. The steam-water system of the HRSG is coupled with the steam-water system of the char combustion boiler, wherein the steam can be superheated by the boiler as so to generate electricity with high parameters of the steam of the boiler. In 15 other words, when coupled with the ultra supercritical steam boiler, the power generation efficiency of gas turbine combined cycle power system is (40%+60% x 45%) = 67%, so the power generation efficiency of the whole system is (45% x 0.7+67% x 0.3) x 0.96 = 50%, which is much higher than that of IGCC or ultra supercritical power generation. If the efficiency of ultra 20 supercritical power generation is increased, then the efficiency of the whole system will be increased accordingly. Embodiment 2 Fuels: lignite with the higher volatile matter Implementating method: 25 As shown in Fig. 3, coal is introduced into the pyrolyzer 1, where it is mixed with hot ash provided from the circulating fluidized bed boiler 5, wherein the hot ash is used to provide heat to cause the coal to be pyrolyzed in the pyrolyzer 1, so as to obtain the gaseous and liquid fuels 11 and the solid char fuel. The resulted gas and liquid fuels are condensed by the condenser 2 so as to be separated from each other and then the separated gaseous and liquid fuels are respectively introduced into the gaseous fuel purifier 3 and liquid fuel purifier 4 for performing dust removing 5 and desulfurization, and finally are introduced into the gas turbine 7 for power generation. The hot flue gas from the gas turbine 7 is introduced into the HRSG 6, where the produced steam is used to drive the steam turbine 8 for power generation. On the other hand, the resulted solid char discharged from the bottom of the pyrolyzer 1 is introduced into the boiler 5, where the 10 steam resulted from combustion of the solid char is used to drive the steam turbine 8 for power generation. Furthermore, the steam produced by the HRSG 6 is also introduced into the steam turbine 8 for power generation. The efficiency of coal pyrolysis is 96%, and 30% of the energy lies in the gaseous and liquid fuel, the rest 70% of the energy lies in the solid char. 15 The efficiency of gaseous and liquid fuel in a gas turbine combined cycle power system is 58%, and the efficiency of the char combustion in an ultra supercritical boiler to produce steam for power generation is 45%, so the efficiency of a hybrid power generation of the present invention is (45% x 0.7+58% x 0.3) x 0.96 = 47%, which is higher than 46% of IGCC and 45% 20 of ultra supercritical power generation units. However, compared with IGCC, the cost and complexity of the present invention is greatly reduced. It should be noted that the above embodiments are only used to illustrate the technical scheme of the present invention instead of limiting the scope of the present invention. Although the present invention is 25 described in details referring to the embodiments, persons skilled in the art should understand, modifications or equivalent replacement may be made within the spirit of the present invention. The protection scope of the present invention is defined in the claims. 12

Claims

1. A hybrid power generation system based on solid fuel pyrolysis and char combustion, comprising: a pyrolyzer (1) for pyrolyzing the solid fuel to produce gaseous, liquid and 5 solid char fuels; a condenser (2), for separating the gaseous and liquid fuels; a gaseous fuel purifier (3), for performing dust removing and desulfurization for the gaseous fuel; a liquid fuel purifier (4), for performing dust removing and desulfurization 10 for the liquid fuel; a boiler (5), for performing combustion of the solid char fuel to generate steam; a gas turbine (7), for burning the gaseous or/and the liquid fuels to generate electricity ; 15 a steam turbine(8), for generating electricity by using the steam produced by the boiler(5).

2. The hybrid power generation system based on solid fuel pyrolysis and char combustion as claimed in claim 1, characterized in that, the hybrid power 20 generation system further includes a heat recovery steam generator (HRSG, 6), for generating steam by using the hot flue gas from the gas turbine (7) to drive the steam turbine(8) to generate electricity.

3. The hybrid power generation system based on solid fuel pyrolysis and char 25 combustion as claimed in claim 1, characterized in that, the hybrid power generation system further includes a HRSG (6) for generating steam by using the hot flue gas from the gas turbine (7) and introducing the steam into the boiler (5) so as to be mixed with the steam produced therein, and then the mixture is superheated and introduced into the steam turbine(8) to generate 30 13 electricity; or the steam generated by the HRSG (6) is introduced into the boiler (5) to be superheated individually, after which it is introduced into the steam turbine (8) to drive the steam turbine (8) together with other steam from boiler to generate electricity. 5

4. A hybrid power generation 'method based on solid fuel pyrolysis and char combustion, including the steps of: (1) feeding the solid fuel into a pyrolyzer to be pyrolyzed so as to produce gaseous, liquid and solid char fuels; 10 (2) condensing the gaseous and liquid fuels resulted from step (1) in a condenser so that the gaseous and liquid fuels are separated, after which the gaseous and liquid fuels being performed dust removing, desulfurization through a gaseous fuel purifier and a liquid fuel purifier separately, and then generating electricity by introducing the gaseous and/or liquid fuels into a gas 15 turbine; (3) burning the char resulted from pyrolysis in a boiler to produce steam for driving a steam turbine to generate electricity.

5. The hybrid power generation method based on solid fuel pyrolysis and char 20 combustion as claimed in claim 4, characterized in that, the method further includes step (4): introducing the hot flue gas from the gas turbine into a HRSG to produce steam for driving the steam turbine to generate electricity.

6. The hybrid power generation method based on solid fuel pyrolysis and char 25 combustion as claimed in claim 5, characterized in that the steam produced by the boiler burning char in step (3) and the steam generated from the HRSG in step (4) are respectively introduced into the same or different steam turbines to generate electricity. 30 14

7. The hybrid power generation method based on solid fuel pyrolysis and char combustion as claimed in claim 5, characterized in that the steam produced by the HRSG in step (4) is introduced into the char combustion boiler, mixed with the steam produced in the boiler and superheated, and then the mixture is 5 introduced into the steam turbine to generate electricity; or the steam is introduced into the boiler to be superheated individually, and then is introduced into the steam turbine to drive the steam turbine together with other steam from boiler to generate electricity. 10

8. The hybrid power generation method based on solid fuel pyrolysis and char combustion as claimed in claim 4, characterized in that the solid fuel includes coal, oil sands, oil shale or biomass.

9. The hybrid power generation method based on solid fuel pyrolysis and char 15 combustion as claimed in claim 4, characterized in that the pyrolysis includes simple pyrolysis, partial combustion pyrolysis, partial gasification pyrolysis or combination thereof.

10. The hybrid power generation method based on solid fuel pyrolysis and char 20 combustion as claimed in claim 4, characterized in that the liquid fuel in step (2) is output as a product directly. 25 15