A power generation method based on complementary gasification of coal and biomass

Abstract

The present disclosure provides a power generation method and system based on complementary gasification of coal and biomass, in which heat generated by combustion of biomass in an external combustor is used to provide heat for pyrolysis and gasification processes; the pyrolysis adopts a staged pyrolysis mode, and the process is divided into low-temperature and high-temperature two stages, so that carbon dioxide is released in the low-temperature stage, and carbon monoxide and hydrogen are released in the high-temperature stage, realizing enrichment of carbon dioxide at a lower pyrolysis temperature and enrichment of hydrogen at a higher pyrolysis temperature, reducing carbon dioxide separation energy consumption, and realizing directional separation of carbon and hydrogen components. The gasification process adopts a water vapor conversion reactor and a carbon capture unit, first converting carbon monoxide in the mixed gas into hydrogen and carbon dioxide by using the water vapor conversion reaction, and then capturing carbon dioxide in the conversion gas by using the carbon capture unit, greatly reducing the carbon dioxide emission in the gasification power generation process.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of energy power, and mainly relates to a coal and biomass complementary gasification based power generation method and system. BACKGROUND

[0002] For a long time, coal has been an important part of China's energy structure. In recent years, China has actively promoted the transformation of clean energy, but coal is still the main source of energy, used in power and industry and other fields. Coal mining and utilization process will release a large amount of pollutants and harmful gases, causing air and environmental pollution, and causing harm to human health and natural ecosystems. China has abundant biomass resources, and reasonable development and utilization of biomass resources can not only reduce the use of fossil energy, but also reduce carbon dioxide emissions and environmental pollution.

[0003] Pyrolysis technology is a thermochemical process that decomposes coal, biomass and other fuels into gaseous, liquid and solid products under high temperature conditions. Generally, the pyrolysis process is carried out in the absence of oxygen or in an inert gas atmosphere, and the temperature range of the pyrolysis process is between a few hundred degrees Celsius and a few thousand degrees Celsius. The properties of pyrolysis products are mainly affected by factors such as temperature, reaction time, raw material type and reactor type. Gasification technology is a process that converts carbon-based fuels into synthesis gas under high temperature and gasification agent atmosphere. The temperature range of the gasification process is usually within 600-1500℃, and the gasification agent is usually oxygen, carbon dioxide and steam. The main components of synthesis gas are carbon monoxide, hydrogen, carbon dioxide and methane, etc., and the proportion of these gas components depends on the fuel and reaction conditions.

[0004] In existing gasification and pyrolysis technologies, heat generated by burning fossil fuels such as natural gas or coal is usually used to heat pyrolysis furnaces and gasification furnaces. However, the existing heating method also has the disadvantages of high energy consumption and high carbon dioxide emissions. Therefore, it is necessary to seek a low-carbon and economical heating method.

[0005] In existing gasification power generation technologies, the heat generated by burning synthesis gas with air is used as the high-temperature heat source of the power generation system, and the exhaust gas produced after the synthesis gas is burned is directly discharged into the environment. Since the main components of synthesis gas are hydrogen and carbon monoxide, the composition of the flue gas after combustion contains carbon dioxide, resulting in an increase in the amount of carbon dioxide emitted into the environment.

[0006] In summary, achieving efficient and clean use of coal and reducing carbon dioxide emissions from fossil energy power generation is a problem that needs to be solved in China. SUMMARY

[0007] Therefore, the application provides a coal and biomass complementary gasification-based power generation method and system.

[0008] To solve the above technical problems, the application is implemented as follows.

[0009] A coal and biomass complementary gasification-based power generation method, comprising the following steps.

[0010] Step S1: using a burner to generate flue gas heat to preheat air and dry biomass;

[0011] Step S2: drying the biomass and combusting the hot air to generate pyrolysis heat, including first pyrolysis heat and second pyrolysis heat; the first pyrolysis heat is less than the second pyrolysis heat;

[0012] Step S3: using the first pyrolysis heat to heat a low-temperature pyrolysis furnace to pyrolyze coal into semi-coke and low-temperature pyrolysis gas;

[0013] Step S4: using the second pyrolysis heat to heat a high-temperature pyrolysis furnace to pyrolyze the semi-coke into coke and high-temperature pyrolysis gas; the low-temperature pyrolysis gas contains more carbon dioxide than the high-temperature pyrolysis gas;

[0014] Step S5: combusting the dried biomass and hot air to generate gasification heat, and using the gasification heat to heat a gasification furnace to gasify the coke into synthesis gas;

[0015] Step S6: combining the low-temperature pyrolysis gas, the high-temperature pyrolysis gas and the synthesis gas into high-temperature mixed gas, and using a heat exchanger to recover heat of the high-temperature mixed gas to heat a gasification agent, and then the heated gasification agent enters the gasification furnace;

[0016] Step S7: removing tar in the low-temperature mixed gas generated by heat exchange to generate pure mixed gas;

[0017] Step S8: performing a water-gas shift reaction on the pure mixed gas to generate converted gas;

[0018] Step S9: separating carbon dioxide in the converted gas by a carbon dioxide capture unit to obtain hydrogen gas with high purity;

[0019] Step S10: using the hydrogen gas with high purity as fuel of a combined cycle unit to generate electric power.

[0020] Preferably, the step S3 further introduces dry biomass into the low-temperature pyrolysis furnace, and the low-temperature pyrolysis furnace uses the first heat to pyrolyze the mixture of the biomass and the coal.

[0021] Preferably, the first pyrolysis heat supports the operation temperature of the low-temperature pyrolysis furnace, which is selected from 200-1000℃; the second pyrolysis heat supports the operation temperature of the high-temperature pyrolysis furnace, which is selected from 600-1500℃; and the operation temperature of the low-temperature pyrolysis furnace is less than that of the high-temperature pyrolysis furnace.

[0022] Preferably, in step S1, the drying temperature of the biomass is selected from 100-150℃.

[0023] Preferably, in step S5, the gasification temperature is selected from 900-1500℃.

[0024] Preferably, in step S6, the gasification agent is steam, carbon dioxide or oxygen.

[0025] Preferably, in step S7, the tar removal method is water washing or adsorption.

[0026] Preferably, in step S8, the temperature of the steam shift reaction is selected from 200-500℃.

[0027] Preferably, in step S9, the carbon dioxide capture unit separates the carbon dioxide in the converted gas by chemical absorption or physical absorption.

[0028] The application also provides a coal-biomass complementary gasification-based power generation system, which comprises:

[0029] a dryer for heating the biomass by using the heat of the second exhaust flue gas discharged from the air preheater to generate dried biomass, the dried biomass being provided to the combustor as fuel, and the first exhaust flue gas after heat exchange being discharged into the environment;

[0030] a combustor for combusting the dried biomass and hot air to generate heat and high-temperature flue gas, the heat including the first pyrolysis heat, the second pyrolysis heat and the gasification heat; the first pyrolysis heat being less than the second pyrolysis heat;

[0031] an air preheater for heating air by using the high-temperature flue gas generated by the combustor to produce hot air, which is provided to the combustor; and the first exhaust flue gas after heat exchange being introduced into the dryer;

[0032] a low-temperature pyrolysis furnace for pyrolyzing the coal for pyrolysis by using the first pyrolysis heat to produce semi-coke and low-temperature pyrolysis gas;

[0033] a high-temperature pyrolysis furnace for pyrolyzing the semi-coke by using the second pyrolysis heat to produce coke and high-temperature pyrolysis gas; the volume fraction of carbon dioxide contained in the low-temperature pyrolysis gas being greater than that in the high-temperature pyrolysis gas;

[0034] a gasification furnace for gasifying the coke by using the gasification heat and the gasification agent after heat exchange in the heat exchanger to generate synthesis gas;

[0035] A heat exchanger is used to heat the gasification agent by using high-temperature mixed gas composed of low-temperature pyrolysis gas, high-temperature pyrolysis gas and synthesis gas, and the heated gasification agent is provided to the gasifier; and the low-temperature mixed gas generated after heat exchange is provided to the tar separation device;

[0036] A tar separation device is used to separate tar in the low-temperature mixed gas to generate pure mixed gas;

[0037] A water-gas shift reactor is used to convert carbon monoxide in the pure mixed gas into carbon dioxide by water-gas shift reaction, and to obtain conversion gas mainly composed of carbon dioxide and hydrogen;

[0038] A carbon dioxide capture unit is used to capture carbon dioxide in the conversion gas and to produce hydrogen;

[0039] A combined cycle unit is used to generate electricity by using the hydrogen as fuel.

[0040] Preferably, in step S8, the temperature of the water-gas shift reaction ranges from 200 to 500℃.

[0041] The system further comprises a coal pretreatment unit used to crush and dry the coal to generate the coal used for pyrolysis and provided to the low-temperature pyrolysis furnace.

[0042] Preferably, in step S8, the temperature of the water-gas shift reaction ranges from 200 to 500℃.

[0043] There is a conveying channel between the dryer and the low-temperature pyrolysis furnace, and the dried biomass enters the low-temperature pyrolysis furnace through the conveying channel according to the desired blending ratio of the biomass and the coal, and the low-temperature pyrolysis furnace pyrolyzes the blend of the dried biomass and the coal by using the first pyrolysis heat; the blending ratio is greater than or equal to 0.

[0044] Advantages:

[0045] (1) The present application proposes a power generation method based on complementary gasification of coal and biomass, which uses the heat generated by the combustion of biomass in an external burner to provide heat for the pyrolysis and gasification processes. Since biomass is a carbon-neutral fuel, it does not produce additional carbon dioxide emissions. Compared with traditional heating methods, biomass external heating reduces heating costs and carbon dioxide emissions.

[0046] (2) Compared with existing gasification power generation technology, the present application uses a water-gas shift reactor and a carbon capture unit. First, the water-gas shift reaction is used to convert carbon monoxide in the mixed gas into hydrogen and carbon dioxide, and then the carbon capture unit is used to capture carbon dioxide in the conversion gas, greatly reducing the carbon dioxide emissions in the gasification power generation process. The introduction of the carbon capture unit can effectively reduce the carbon emissions in the power generation process. Therefore, the present application has good environmental benefits and industrial application scenarios.

[0047] (3) The present application also relates to waste heat recovery technology. The flue gas generated by biomass combustion has a high temperature and high utilization potential. In the present application, the high-temperature flue gas generated by biomass combustion is used to preheat air, and the low-temperature flue gas is used to dry biomass, thereby realizing the cascade utilization of flue gas heat.

[0048] (4) Through the method of staged pyrolysis, the energy consumption of carbon dioxide separation is reduced, and the directional separation of carbon and hydrogen components is realized. BRIEF DESCRIPTION OF DRAWINGS

[0049] Figure 1 The flow chart of the coal and biomass complementary gasification-based power generation method of the present application is shown in Figure 1.

[0050] Figure 2 The composition block diagram of the coal and biomass complementary gasification-based power generation system of the present application is shown in Figure 2.

[0051] In the above-mentioned accompanying Figure 2 In the above-mentioned accompanying DETAILED DESCRIPTION

[0052] The present application will be described in detail below with reference to the accompanying drawings and examples.

[0053] The application provides a coal and biomass complementary gasification based power generation scheme, and the core idea is as follows: firstly, the heat generated by the combustion of biomass in an external combustor is used to provide heat for the pyrolysis and gasification processes. Since biomass is a carbon neutral fuel, no additional carbon dioxide emissions are generated, and compared with the traditional heat supply mode, the biomass external combustion heat supply reduces the heat supply cost and the carbon dioxide emission amount. Secondly, compared with the existing gasification power generation technology, the water vapor conversion reactor and the carbon capture unit are adopted, the carbon monoxide in the mixed gas is converted into hydrogen and carbon dioxide by using the water vapor conversion reaction, and then the carbon dioxide in the converted gas is captured by using the carbon capture unit, so that the carbon dioxide emission amount in the gasification power generation process is greatly reduced.

[0054] Another application point of the application is that in the existing pyrolysis technology, the pyrolysis reaction is concentrated in a pyrolysis furnace, and the gaseous, liquid and solid products are generated at one time, so that the product cannot be accurately controlled. Actually, in the pyrolysis process of coal, carbon dioxide and methane are first generated at a lower pyrolysis temperature, and with the increase of the pyrolysis temperature, the yield of hydrogen and carbon monoxide is gradually increased, so that the carbon dioxide component concentration is continuously reduced. Compared with the existing pyrolysis technology, the application adopts a staged pyrolysis mode, and the gaseous products at different pyrolysis temperature stages of coal are collected separately, so that the mixing of carbon and hydrogen components is avoided. Among them, carbon dioxide is enriched at a lower temperature, and the energy consumption for separating carbon dioxide is reduced. Hydrogen is enriched at a higher temperature, and the subsequent hydrogen purification energy consumption is reduced.

[0055] In order to make the purpose, technical scheme and advantages of the application more clear, the application will be further described in detail below with reference to the drawings.

[0056] Embodiment 1

[0057] The embodiment provides a preferred scheme of a coal and biomass complementary gasification based power generation method, referring to Figure 1 The method comprises the following steps:

[0058] S1, the heat of the flue gas generated by the combustor is used to heat air and dry biomass, and the heated hot air and dry biomass enter the combustor again.

[0059] In a preferred embodiment, part of the dried biomass enters the combustor, and the other part enters the low-temperature pyrolysis furnace together with the pretreated coal.

[0060] The process can be considered as a pretreatment process of biomass and coal, which can realize the functions of biomass drying, coal crushing and drying, and air preheating. The heat required for biomass drying and air preheating comes from the flue gas generated by the combustion of biomass and hot air in step S2. The flue gas first enters the air preheater to heat the air, and then enters the dryer to dry the biomass, which realizes the cascade utilization of flue gas heat and reduces the heat loss of flue gas.

[0061] Here, biomass refers to all types of biomass; the type of coal is not limited; the mixing ratio of biomass and coal entering the low-temperature pyrolysis furnace is not limited, and the biomass ratio can be 0.

[0062] S2, drying biomass and hot air combustion to generate pyrolysis heat, wherein the pyrolysis heat includes at least first pyrolysis heat and second pyrolysis heat. The first pyrolysis heat is less than the second pyrolysis heat.

[0063] Part of the dried biomass generated in step S1 and the combustion of hot air generate heat and high-temperature flue gas. The pyrolysis heat released by combustion includes the first pyrolysis heat required in step S3 and the second pyrolysis heat required in step S4. The flue gas released by combustion provides heat for the air preheater and the dryer. The preferred drying temperature of biomass is in the range of 100-150℃

[0064] S3, using the first pyrolysis heat to heat the low-temperature pyrolysis furnace to pyrolyze biomass and coal to generate semi-coke and low-temperature pyrolysis gas. The main components of low-temperature pyrolysis gas are carbon dioxide, methane, carbon monoxide, hydrogen and tar, which are the same as high-temperature pyrolysis gas, but the volume fraction of carbon dioxide in low-temperature pyrolysis gas is higher than that in high-temperature pyrolysis gas.

[0065] The process can be considered as a low-temperature co-pyrolysis process of biomass and coal, which can realize the enrichment of carbon dioxide at a lower temperature. The required heat is provided by step S2, and under the condition of lower temperature pyrolysis, semi-coke and low-temperature pyrolysis gas with high carbon dioxide content can be obtained.

[0066] S4, using the second pyrolysis heat to heat the high-temperature pyrolysis furnace to pyrolyze semi-coke to generate coke and high-temperature pyrolysis gas.

[0067] The process can be considered as a high-temperature pyrolysis process of semi-coke, which makes semi-coke generate hydrogen and carbon monoxide at a higher temperature. Semi-coke is provided by step S3, and the required heat is provided by step S2. Under the condition of higher temperature pyrolysis, coke and high-temperature pyrolysis gas mainly composed of hydrogen and carbon monoxide can be obtained.

[0068] In this embodiment, the operating temperature range of the low-temperature pyrolysis furnace is preferably 200-1000℃; the operating temperature range of the high-temperature pyrolysis furnace is preferably 600-1500℃. At the same time, the operating temperature of the low-temperature pyrolysis furnace is less than the operating temperature of the high-temperature pyrolysis furnace.

[0069] S5, using the heat of gasification to supply heat to the gasifier to gasify the coke to generate synthesis gas.

[0070] The process can be considered as a gasification process of coke, which uses the heat generated by the burner in step S2 to supply heat to the gasifier, and the coke generated in step S4 and the high-temperature gasification agent generated in step S6 to generate synthesis gas in the gasifier. The main components of the synthesis gas are hydrogen and carbon monoxide. The gasification temperature of the gasifier is preferably 900-1500°C.

[0071] S6, the low-temperature pyrolysis gas, the high-temperature pyrolysis gas, and the synthesis gas are combined to form a high-temperature mixed gas, and the heat of the high-temperature mixed gas is recovered by the heat exchanger to heat the gasification agent, and the heated gasification agent enters the gasifier.

[0072] The process uses the heat exchanger to recover the heat of the low-temperature pyrolysis gas in step S3, the high-temperature pyrolysis gas in step S4, and the synthesis gas in step S5 to preheat the gasification agent, and the preheated gasification agent enters the gasifier. The gasification agent can be water vapor, carbon dioxide, and oxygen.

[0073] S7, the low-temperature mixed gas generated by the heat exchange enters the tar separation device to remove tar to generate pure mixed gas.

[0074] The process uses the tar separation device to separate the tar in the low-temperature mixed gas in step S6 to generate pure mixed gas with low tar content. The tar removal method can be water washing or adsorption.

[0075] S8, the pure mixed gas enters the shift reactor to undergo a water-gas shift reaction to generate shift gas.

[0076] The process uses the water-gas shift reaction to convert the carbon monoxide in the pure mixed gas in step S7 into carbon dioxide and hydrogen to generate shift gas mainly composed of carbon dioxide and hydrogen. The temperature range of the water-gas shift reaction is preferably 200-500°C.

[0077] S9, separating the carbon dioxide in the shift gas by a carbon dioxide capture unit to obtain high-purity hydrogen.

[0078] The shift gas generated in step S8 is passed into the carbon dioxide capture unit to separate carbon dioxide and pure hydrogen, and the separated carbon dioxide is stored. The carbon dioxide capture method can be chemical absorption or physical absorption, etc.

[0079] S10, using the high-purity hydrogen as fuel for a combined cycle unit to generate electricity.

[0080] The high-purity hydrogen in step S9 is used as fuel for a combined cycle to generate low-carbon electricity.

[0081] In the power generation method proposed in this embodiment, the heat required by the low-temperature pyrolysis furnace, the high-temperature pyrolysis furnace and the gasification furnace is provided by an external burner, which reduces energy consumption and carbon dioxide emissions compared to traditional heating methods. The high-temperature flue gas generated by the combustion of biomass in the external burner provides heat for the air preheater and the dryer. This process maximizes the use of flue gas heat and realizes the cascade utilization of flue gas heat. Compared with the traditional pyrolysis method, the pyrolysis process in the present invention is divided into two stages: low-temperature pyrolysis and high-temperature pyrolysis, so that carbon dioxide is first released in the low-temperature stage, and carbon monoxide and hydrogen are released in the high-temperature stage, thereby realizing the separation of hydrocarbon components. In addition, the present invention captures the carbon dioxide generated in the power generation process and reduces carbon dioxide emissions.

[0082] Example 2

[0083] Based on the above method, this embodiment provides a system for implementing the above method, such as Figure 2 As shown, the system based on the complementary gasification of coal and biomass includes a dryer 1, a burner 2, an air preheater 3, a coal pretreatment unit 4, a low-temperature pyrolysis furnace 5, a high-temperature pyrolysis furnace 6, a gasifier 7, a heat exchanger 8, a tar separation device 9, a water-gas shift reactor 10, a carbon capture unit 11 and a combined cycle unit 12. Among them:

[0084] Dryer 1 can implement step S1 above, utilizing the waste heat from second exhaust gas 24 discharged from air preheater 3 to heat raw biomass 13, producing dried biomass. In a preferred embodiment, the dried biomass has two destinations, as the resulting dried biomass is divided into first dried biomass 15 and second dried biomass 16. After heat exchange, first exhaust gas 14 from dryer 1 is discharged into the environment.

[0085] The burner 2 can implement the above step S2, and is used to burn the first dried biomass 15 and the hot air 23 from the air preheater 3 to generate heat 17 and high-temperature flue gas 21. The heat 17 includes first pyrolysis heat 18, second pyrolysis heat 19 and gasification heat 20.

[0086] The air preheater 3 can implement the above step S1, and is used to use the high-temperature flue gas 21 generated by the burner 2 to heat air 22 to produce hot air 23, which is provided to the burner 2. The first exhaust flue gas 24 after heat exchange is circulated back to enter the dryer 1.

[0087] The coal pre-processing unit 4 can implement the above step S1 to dry and crush the raw coal 25 into coal 26 for pyrolysis.

[0088] The low-temperature pyrolysis furnace 5 can realize the above step S3, and is used for pyrolyzing the coal 26 and the second dry biomass 16 to produce semi-coke 28 and low-temperature pyrolysis gas 27 by using the first pyrolysis heat 18. In other embodiments, if no dry biomass is introduced, the low-temperature pyrolysis furnace only pyrolyzes the coal.

[0089] The high-temperature pyrolysis furnace 6 can realize the above step S4, and is used for pyrolyzing the semi-coke 28 to produce coke 30 and high-temperature pyrolysis gas 29 by using the second pyrolysis heat 19.

[0090] The gasification furnace 7 can realize the above step S5, and is used for heating the coke 30 and the high-temperature gasification agent 33 to make the coke gasify to produce high-temperature synthesis gas 31 by using the gasification heat 20.

[0091] The heat exchanger 8 can realize the above step S6, and is used for heating the gasification agent 32 by using the heat of the high-temperature mixed gas composed of the low-temperature pyrolysis gas 27, the high-temperature pyrolysis gas 29 and the high-temperature synthesis gas 31 to obtain the high-temperature gasification agent 33, which is provided to the gasification furnace 7. The low-temperature mixed gas 34 produced after the heat exchange is provided to the tar separation device 9.

[0092] The tar separation device 9 can realize the above step S7, and is used for separating the tar 35 in the low-temperature mixed gas 34 to obtain the pure mixed gas 36.

[0093] The water-gas shift reactor 10 can realize the above step S8, and is used for converting the carbon monoxide in the pure mixed gas 36 into carbon dioxide and hydrogen by the water-gas shift reaction to obtain the shift gas 37 mainly composed of carbon dioxide and hydrogen.

[0094] The carbon capture unit 11 can realize the above step S9, and is used for capturing the carbon dioxide 38 in the shift gas 37 to generate the hydrogen 39 with higher purity.

[0095] The combined cycle unit 12 can realize the above step S10, and is used for generating the electric power 40 by using the hydrogen 39 with higher purity as fuel.

[0096] In the above description, the dryer 1 can be an air flow dryer, and the coal pretreatment unit 4 can use existing equipment such as a coal mill. The low-temperature pyrolysis furnace 5 and the high-temperature pyrolysis furnace 6 can be one of a heating furnace, a soaking furnace or a calcining furnace.

[0097] Examples

[0098] In order to further illustrate the feasibility of the present application, one of the typical working conditions is selected, and the power generation process is simulated. In the selected working condition, the coal is used as fuel for the staged pyrolysis and gasification, and the biomass is only used as fuel for the burner and does not participate in the pyrolysis and gasification process. Table 1 shows the basic operating parameters of the example.

[0099] To illustrate the difference of the components of low-temperature pyrolysis gas and high-temperature pyrolysis gas, Table 2 gives the mole fraction of the main components of low-temperature and high-temperature pyrolysis gas in the simulation results.

[0100] Table 3 gives the energy analysis results of the example. From the energy input point of view, the energy of coal used for staged pyrolysis and gasification accounts for 72.57% of the total input energy, and the energy of biomass used for external combustion heat supply accounts for 25.17% of the total input energy. From the system power consumption point of view, the power consumption of the air compressor in the combined cycle power generation system accounts for 89.86% of the total power consumption, and the power consumption of carbon capture accounts for 7.57% of the total power consumption. From the energy efficiency point of view, the cold coal gas efficiency of the example is 86.32%, which is higher than that of traditional coal gasification. When the carbon dioxide capture rate is 95%, the carbon capture amount of the example is 10.65 kg / s, and the power generation efficiency of the example is 45.04%, which is higher than that of the traditional coal gasification power generation system (30-35%) under the same carbon capture rate.

[0101] Table 1 Basic parameters of the example

[0102] Basic parameters Value Unit Low temperature pyrolysis temperature 600 ℃ High temperature pyrolysis temperature 950 ℃ Gasification temperature 1000 ℃ Gas turbine inlet temperature 1327 ℃ Waste heat boiler outlet temperature 104 ℃ Steam cycle main steam temperature 566 ℃ Biomass external combustion temperature 1100 ℃ Shift reaction temperature 220 ℃ Pyrolysis pressure 1.1 bar Gasification pressure 20 bar Steam / char molar ratio 1.12 - Heat transfer loss 6 ％ Carbon monoxide / water molar ratio 1.4 - Selexol separation process, CO2 capture rate 95 ％ Gas turbine efficiency 92 ％ High, medium and low pressure cylinder efficiency 88 / 89 / 87 ％ Coal consumption 5 kg / s Biomass consumption 1.99 kg / s Gasification agent (water) consumption 4.88 kg / s

[0103] Table 2 Mole fraction of the main components of low-temperature pyrolysis gas and high-temperature pyrolysis gas

[0104]

[0105] Table 3 Energy analysis results of the example

[0106]

[0107]

[0108] The above specific embodiments further illustrate the purpose, technical solutions and beneficial effects of the present application. It should be understood that the above description is only for specific embodiments of the present application and is not intended to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. A method for power generation based on coal and biomass complementary gasification, characterized by, The system comprises: Step S1, using a combustor to generate flue gas heat to preheat air and dry biomass; Step S2, dry biomass and hot air combustion generates pyrolysis heat, including first pyrolysis heat and second pyrolysis heat; the first pyrolysis heat is less than the second pyrolysis heat; Step S3, the first pyrolysis heat provides heat for the low-temperature pyrolysis furnace to generate semi-coke and low-temperature pyrolysis gas from coal pyrolysis; Step S4, the second pyrolysis heat provides heat for the high-temperature pyrolysis furnace to generate coke and high-temperature pyrolysis gas from semi-coke pyrolysis; the volume fraction of carbon dioxide contained in the low-temperature pyrolysis gas is greater than that in the high-temperature pyrolysis gas; Step S5, dry biomass and hot air combustion generates gasification heat to provide heat for the gasification furnace to generate synthesis gas from coke gasification; Step S6, the low-temperature pyrolysis gas, the high-temperature pyrolysis gas, and the synthesis gas constitute a high-temperature mixed gas, and the heat of the high-temperature mixed gas is recovered through a heat exchanger to heat the gasification agent, thereby obtaining a low-temperature mixed gas generated by heat exchange, and the heated gasification agent enters the gasification furnace; Step S7, tar in the low-temperature mixed gas generated by heat exchange is removed to generate a pure mixed gas; Step S8, the pure mixed gas is subjected to a water-gas shift reaction to generate a shifted gas; Step S9, carbon dioxide in the shifted gas is separated by a carbon dioxide capture unit to obtain purified hydrogen gas; Step S10, the purified hydrogen gas is used as fuel for a combined cycle unit to produce electricity.

2. The method of claim 1, wherein, Step S3 further introduces dry biomass into the low-temperature pyrolysis furnace, and the low-temperature pyrolysis furnace pyrolyzes the mixture of biomass and coal using the first pyrolysis heat.

3. The method of claim 1, wherein, The first pyrolysis heat supports the operating temperature range of the low-temperature pyrolysis furnace to be 200-1000℃; the second pyrolysis heat supports the operating temperature range of the high-temperature pyrolysis furnace to be 600-1500℃; and the operating temperature of the low-temperature pyrolysis furnace is less than that of the high-temperature pyrolysis furnace.

4. The method of claim 1, wherein, In step S1, the biomass drying temperature range is 100-150℃.

5. The method of claim 1, wherein, In step S5, the gasification temperature is 900-1500℃; and in step S6, the gasification agent is steam, carbon dioxide, or oxygen.

6. The method of claim 1, wherein, In step S8, the temperature range of the water-gas shift reaction is 200-500℃.

7. The method of claim 1, wherein, In step S7, the tar removal method is water washing or adsorption; and in step S9, the carbon dioxide capture unit separates carbon dioxide in the shifted gas by using a chemical absorption method or a physical absorption method.

8. A power generation system based on coal and biomass complementary gasification, characterized by, The system comprises: A dryer (1) for heating biomass to generate dry biomass using the heat of the second exhaust flue gas (24) discharged from the air preheater (3), and the dry biomass is provided to the combustor (2) as fuel, and the first exhaust flue gas (14) after heat exchange is discharged into the environment; A combustor (2) for combusting dry biomass and hot air (23) to generate heat (17) and high-temperature flue gas (21), and the heat (17) includes first pyrolysis heat (18), second pyrolysis heat (19), and gasification heat (20); the first pyrolysis heat is less than the second pyrolysis heat; An air preheater (3) for heating air to produce hot air (23) using the high-temperature flue gas (21) generated by the combustor (2) and providing the hot air (23) to the combustor (2); and the second exhaust flue gas (24) generated by heat exchange enters the dryer (1). a low-temperature pyrolysis furnace (5) for pyrolyzing coal (26) for pyrolysis to produce semi-coke (28) and low-temperature pyrolysis gas (27) using the first pyrolysis heat (18); a high-temperature pyrolysis furnace (6) for pyrolyzing the semi-coke (28) to produce coke (30) and high-temperature pyrolysis gas (29) using the second pyrolysis heat (19); the low-temperature pyrolysis gas contains more carbon dioxide than the high-temperature pyrolysis gas; a gasifier (7) for gasifying the coke (30) using the gasification heat (20) and the heated gasification agent (33) from the heat exchanger (8) to produce synthesis gas (31); a heat exchanger (8) for heating the gasification agent using the heat of the high-temperature mixed gas composed of the low-temperature pyrolysis gas (27), the high-temperature pyrolysis gas (29) and the synthesis gas (31), and providing the heated gasification agent to the gasifier (7); the low-temperature mixed gas (34) produced after heat exchange is provided to the tar separation device (9); a tar separation device (9) for separating tar (35) from the low-temperature mixed gas (34) to produce pure mixed gas (36); a water-gas shift reactor (10) for converting carbon monoxide in the pure mixed gas (36) into carbon dioxide through a water-gas shift reaction to obtain conversion gas (37) mainly composed of carbon dioxide and hydrogen; a carbon dioxide capture unit (11) for capturing carbon dioxide (38) in the conversion gas (37) to produce hydrogen (39); a combined cycle unit (12) for generating electricity using the hydrogen (39) as fuel.

9. The system of claim 8, wherein, The system further comprises a coal pretreatment unit (4) for crushing and drying coal to produce the coal (26) for pyrolysis provided to the low-temperature pyrolysis furnace (5).

10. The system of claim 8, wherein, There is a conveying channel between the dryer (1) and the low-temperature pyrolysis furnace (5), and the dried biomass enters the low-temperature pyrolysis furnace (5) through the conveying channel according to the desired mixing ratio of biomass and coal, and the low-temperature pyrolysis furnace (5) pyrolyzes the mixture of dried biomass and coal using the first pyrolysis heat; the mixing ratio is greater than or equal to 0. a low-temperature pyrolysis furnace (5) for pyrolyzing coal (26) for pyrolysis to produce semi-coke (28) and low-temperature pyrolysis gas (27) using the first pyrolysis heat (18); a high-temperature pyrolysis furnace (6) for pyrolyzing the semi-coke (28) to produce coke (30) and high-temperature pyrolysis gas (29) using the second pyrolysis heat (19); the low-temperature pyrolysis gas contains more carbon dioxide than the high-temperature pyrolysis gas; a gasifier (7) for gasifying the coke (30) using the gasification heat (20) and the heated gasification agent (33) from the heat exchanger (8) to produce synthesis gas (31); a heat exchanger (8) for heating the gasification agent using the heat of the high-temperature mixed gas composed of the low-temperature pyrolysis gas (27), the high-temperature pyrolysis gas (29) and the synthesis gas (31), and providing the heated gasification agent to the gasifier (7); the low-temperature mixed gas (34) produced after heat exchange is provided to the tar separation device (9); a tar separation device (9) for separating tar (35) from the low-temperature mixed gas (34) to produce pure mixed gas (36); a water-gas shift reactor (10) for converting carbon monoxide in the pure mixed gas (36) into carbon dioxide through a water-gas shift reaction to obtain conversion gas (37) mainly composed of carbon dioxide and hydrogen; a carbon dioxide capture unit (11) for capturing carbon dioxide (38) in the conversion gas (37) to produce hydrogen (39); a combined cycle unit (12) for generating electricity using the hydrogen (39) as fuel.

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