Power generation method based on complementary gasification of coal and biomass

Abstract

The invention provides a power generation method and system based on complementary gasification of coal and biomass. According to the method, heat generated by combustion of biomass in an external combustor is used for supplying heat to pyrolysis and gasification processes; the pyrolysis adopts a graded pyrolysis mode, and the process is divided into a low-temperature stage and a high-temperature stage, so that carbon dioxide is released at the low-temperature stage, carbon monoxide and hydrogen are released at the high-temperature stage, enrichment of carbon dioxide at a relatively low pyrolysis temperature and enrichment of hydrogen at a relatively high pyrolysis temperature are realized, the energy consumption of carbon dioxide separation is reduced, and the production efficiency is improved. And directional separation of hydrocarbon components is realized. A water vapor conversion reactor and a carbon capture unit are adopted in the gasification process, firstly, carbon monoxide in mixed gas is converted into hydrogen and carbon dioxide through the water vapor conversion reaction, then carbon dioxide in converted gas is captured through the carbon capture unit, and the emission amount of carbon dioxide in the gasification power generation process is greatly reduced.

Description

Technical Field

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

[0002] Coal has long been an important part of my country's energy structure. In recent years, my country has actively promoted the transformation to clean energy, but coal is still the main source of energy, used in many fields such as electricity and industry. The process of coal mining and utilization will release a large amount of pollutants and harmful gases, causing air and environmental pollution, and causing harm to human health and natural ecosystems. my country has abundant biomass resources. The rational 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 fuels such as coal and biomass into gas, liquid and solid products under high temperature. Usually, 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 several hundred degrees Celsius and several thousand degrees Celsius. The properties of the pyrolysis products are mainly affected by factors such as temperature, reaction time, type of raw materials and reactor type. Gasification technology is a process that converts carbon-based fuels into synthesis gas under high temperature and gasifying agent atmosphere. The temperature range of the gasification process is usually between 600 and 1500°C, and the gasifying agent is usually oxygen, carbon dioxide and water vapor. The main components of synthesis gas are carbon monoxide, hydrogen, carbon dioxide and methane, and the proportions of these gas components depend on the fuel and reaction conditions.

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

[0005] In the existing gasification power generation technology, the heat generated by the combustion of syngas and air is used as the high-temperature heat source of the power generation system, and the exhaust gas generated after the combustion of syngas is directly discharged into the environment. Since the main components of syngas are hydrogen and carbon monoxide, the flue gas after combustion contains carbon dioxide, which leads to an increase in the amount of carbon dioxide discharged into the environment.

[0006] To sum up, achieving efficient and clean utilization of coal and reducing carbon dioxide emissions from fossil energy power generation are issues that my country urgently needs to address. Summary of the invention

[0007] In view of this, the present invention provides a power generation method and system based on the complementary gasification of coal and biomass, which utilizes the heat generated by biomass combustion to provide heat for the pyrolysis and gasification processes, which can effectively reduce the carbon emissions in the heating process; and introduces a carbon capture unit, which can effectively reduce the carbon emissions in the power generation process.

[0008] In order to solve the above technical problems, the present invention is implemented as follows.

[0009] A method for power generation based on complementary gasification of coal and biomass, comprising:

[0010] Step S1, using the heat of flue gas generated by a burner to preheat air and dry biomass;

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

[0012] Step S3, the first pyrolysis heat is used to heat the low-temperature pyrolysis furnace to pyrolyze the coal to generate semi-coke and low-temperature pyrolysis gas;

[0013] Step S4, the second pyrolysis heat is used to heat the high-temperature pyrolysis furnace to pyrolyze the semi-coke to generate coke and high-temperature pyrolysis gas; the volume fraction of carbon dioxide contained in the low-temperature pyrolysis gas is greater than that in the high-temperature pyrolysis gas;

[0014] Step S5, drying the biomass and burning the hot air to generate gasification heat, which is used to heat the gasifier to gasify the coke to generate synthesis gas;

[0015] Step S6: The low-temperature pyrolysis gas, the high-temperature pyrolysis gas and the synthesis gas form a high-temperature mixed gas, and the heat of the high-temperature mixed gas is recovered by a heat exchanger to heat the gasifying agent, and the heated gasifying agent enters the gasifier;

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

[0017] Step S8, the pure mixed gas undergoes a water vapor shift reaction to generate a conversion gas;

[0018] Step S9, separating carbon dioxide from the conversion gas through a carbon dioxide capture unit to obtain hydrogen with higher purity;

[0019] Step S10: Use high-purity hydrogen as fuel for the combined cycle unit to produce electricity.

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

[0021] Preferably, the operating temperature range of the low-temperature pyrolysis furnace supported by the first pyrolysis heat is 200-1000°C; the operating temperature range of the high-temperature pyrolysis furnace supported by the second pyrolysis heat is 600-1500°C; and at the same time, the operating temperature of the low-temperature pyrolysis furnace is lower than the operating temperature of the high-temperature pyrolysis furnace.

[0022] Preferably, in step S1, the biomass drying temperature is in the range of 100-150°C.

[0023] Preferably, in step S5, the gasification temperature is 900-1500°C;

[0024] Preferably, in step S6, the gasifying agent is water vapor, carbon dioxide or oxygen.

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

[0026] Preferably, in step S8, the temperature range of the water gas shift reaction is 200-500°C.

[0027] Preferably, in step S9, the carbon dioxide capture unit uses a chemical absorption method or a physical absorption method to separate the carbon dioxide in the conversion gas.

[0028] The present invention also provides a power generation system based on complementary gasification of coal and biomass, the system comprising:

[0029] A dryer, used to heat the biomass using the heat of the second exhaust gas discharged from the air preheater to generate dry biomass, the dry biomass is provided to the burner as fuel, and the first exhaust gas after heat exchange is discharged into the environment;

[0030] A burner is used to burn the dry biomass and hot air to generate heat and high-temperature flue gas, wherein the heat includes a first pyrolysis heat, a second pyrolysis heat and a gasification heat; the first pyrolysis heat is less than the second pyrolysis heat;

[0031] The air preheater is used to heat the air with the high-temperature flue gas generated by the burner to produce hot air, which is then supplied to the burner; the first exhaust flue gas generated by heat exchange enters the dryer;

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

[0033] A high-temperature pyrolysis furnace is used to pyrolyze the semi-coke to produce coke and high-temperature pyrolysis gas using the second pyrolysis heat; the volume fraction of carbon dioxide contained in the low-temperature pyrolysis gas is greater than that in the high-temperature pyrolysis gas;

[0034] A gasifier, used to utilize gasification heat to heat the coke and the gasifying agent heated by the heat exchanger to gasify the coke to generate synthesis gas;

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

[0036] Tar separation device, used to separate tar from low-temperature mixed gas to generate pure mixed gas;

[0037] A water gas conversion reactor, which converts the carbon monoxide in the pure mixed gas into carbon dioxide through a water gas conversion reaction, and obtains a conversion gas mainly composed of carbon dioxide and hydrogen;

[0038] a carbon dioxide capture unit, for capturing carbon dioxide in the conversion gas and producing hydrogen;

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

[0040] Preferably, in step S8, the temperature range of the water gas shift reaction is 200-500°C.

[0041] The system further includes a coal pre-processing unit for crushing and drying the coal to generate the coal for pyrolysis and provide it to the low-temperature pyrolysis furnace.

[0042] Preferably, in step S8, the temperature range of the water gas shift reaction is 200-500°C.

[0043] There is a conveying channel between the dryer and the low-temperature pyrolysis furnace. According to the required blending ratio of biomass and coal, the dried biomass enters the low-temperature pyrolysis furnace through the conveying channel. The low-temperature pyrolysis furnace uses the first pyrolysis heat to pyrolyze the mixture of dry biomass and coal; the blending ratio is greater than or equal to 0.

[0044] Beneficial effects:

[0045] (1) The present invention proposes a power generation method based on the 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 and does not produce additional carbon dioxide emissions, compared with traditional heating methods, biomass external combustion heating reduces heating costs and carbon dioxide emissions.

[0046] (2) Compared with the existing gasification power generation technology, the present invention adopts a water vapor conversion reactor and a carbon capture unit. First, the water vapor conversion reaction is used to convert the carbon monoxide in the mixed gas into hydrogen and carbon dioxide. Then, the carbon capture unit is used to capture the carbon dioxide in the converted gas, which greatly reduces the emission of carbon dioxide 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 invention has good environmental benefits and industrial application scenarios.

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

[0048] (4) Through graded pyrolysis, the energy consumption of carbon dioxide separation is reduced, and the directional separation of hydrocarbon components is achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 This is a flow chart of a power generation method based on complementary gasification of coal and biomass according to Embodiment 1 of the present invention;

[0050] Figure 2 This is a block diagram of a power generation system based on complementary gasification of coal and biomass according to the second embodiment of the present invention.

[0051] In the above-mentioned Figure 2 In the figure, the components and their corresponding marks are: 1-dryer; 2-burner; 3-air preheater; 4-coal pretreatment unit; 5-low temperature pyrolysis furnace; 6-high temperature pyrolysis furnace; 7-gasification furnace; 8-heat exchanger; 9-tar separation device; 10-water gas conversion reactor; 11-carbon capture unit; 12-combined cycle unit; 13-raw biomass; 14, first exhaust flue gas; 15 first dried biomass, 16-second dried biomass; 17-heat; 18-first pyrolysis heat; 19-second pyrolysis heat; 2 0-Gasification heat; 21-High-temperature flue gas; 22-Air; 23-Hot air; 24-Second emission flue gas (flue gas used for biomass drying); 25-Raw coal; 26-Coal used for pyrolysis; 27-Low-temperature pyrolysis gas; 28-Semi-coke; 29-High-temperature pyrolysis gas; 30-Coke; 31-Synthesis gas; 32-Gasifying agent; 33-High-temperature gasifying agent; 34-Low-temperature mixed gas; 35-Tar; 36-Pure mixed gas; 37-Conversion gas; 38-Carbon dioxide; 39-Higher-purity hydrogen; 40-Electricity. DETAILED DESCRIPTION

[0052] The present invention is described in detail below with reference to the accompanying drawings and embodiments.

[0053] The present invention provides a power generation scheme based on the complementary gasification of coal and biomass, the core idea of ​​which is: first, use 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 and does not produce additional carbon dioxide emissions, compared with traditional heating methods, biomass external combustion heating reduces heating costs and carbon dioxide emissions. Secondly, compared with existing gasification power generation technologies, the present invention uses a water vapor conversion reactor and a carbon capture unit, first using a water vapor conversion reaction to convert carbon monoxide in the mixed gas into hydrogen and carbon dioxide, and then using a carbon capture unit to capture carbon dioxide in the converted gas, greatly reducing carbon dioxide emissions during the gasification power generation process.

[0054] Another inventive point of the present invention is that in the existing pyrolysis technology, the pyrolysis reaction is concentrated in a pyrolysis furnace, and gas, liquid and solid products are generated at one time, and precise control of the products cannot be achieved. In fact, in the pyrolysis process of coal, at a lower pyrolysis temperature, carbon dioxide and methane are generated first. As the pyrolysis temperature increases, the yields of hydrogen and carbon monoxide gradually increase, so that the concentration of the carbon dioxide component continues to decrease. Compared with the existing pyrolysis technology, the present invention adopts a graded pyrolysis method to separately collect gaseous products at different pyrolysis temperature stages of coal to avoid mixing of hydrocarbon components. Among them, the enrichment of carbon dioxide is achieved at a lower temperature, which reduces the energy consumption of carbon dioxide separation. The enrichment of hydrogen is achieved at a higher temperature, which reduces the energy consumption of subsequent hydrogen purification.

[0055] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings.

[0056] Example 1

[0057] This embodiment provides a preferred solution for a power generation method based on complementary gasification of coal and biomass, see Figure 1 , the method comprises the following steps:

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

[0059] In a preferred embodiment, a portion of the biomass after drying enters the burner, and the other portion and the pretreated coal enter the low-temperature pyrolysis furnace.

[0060] This 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. This process 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 blending ratio of biomass and coal entering the low-temperature pyrolysis furnace is not limited, and the biomass ratio can be 0.

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

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

[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 the low-temperature pyrolysis gas are carbon dioxide, methane, carbon monoxide, hydrogen and tar, which are the same as those of the high-temperature pyrolysis gas, but the volume fraction of carbon dioxide contained in the low-temperature pyrolysis gas is greater than that of the high-temperature pyrolysis gas.

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

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

[0067] This process can be considered as a high-temperature pyrolysis process of semi-coke, which generates hydrogen and carbon monoxide at a relatively high temperature. The semi-coke is provided by step S3, and the required heat is provided by step S2. Under the pyrolysis condition of a relatively high temperature, 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° C., and the operating temperature range of the high-temperature pyrolysis furnace is preferably 600-1500° C. At the same time, the operating temperature of the low-temperature pyrolysis furnace is lower than the operating temperature of the high-temperature pyrolysis furnace.

[0069] S5. The gasification heat is used to heat the gasifier to gasify the coke to generate synthesis gas.

[0070] This process can be considered as a coke gasification process, in which the heat generated by the burner in step S2 is used to heat the gasifier, and the coke generated in step S4 and the high-temperature gasifying agent generated in step S6 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 form a high-temperature mixed gas. The heat exchanger recovers the heat of the high-temperature mixed gas to heat the gasifying agent, and the heated gasifying agent enters the gasifier.

[0072] In this process, the heat exchanger is used 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 heat exchange enters the tar separation device to remove tar and generate pure mixed gas.

[0074] In this process, the tar separation device is used to separate the tar from the low-temperature mixed gas in step S6 to produce a pure mixed gas with a low tar content. The tar removal method can be a water washing method or an adsorption method.

[0075] S8. The pure mixed gas enters the shift reactor to undergo a water vapor shift reaction to generate a conversion gas.

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

[0077] S9. Separate the carbon dioxide in the conversion gas through a carbon dioxide capture unit to obtain hydrogen with higher purity.

[0078] The conversion gas generated in step S8 is passed into a 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 a chemical absorption method or a physical absorption method.

[0079] S10. Use high purity hydrogen as fuel for the combined cycle unit to produce electricity.

[0080] The higher purity hydrogen in step S9 is used as fuel for the combined cycle to produce 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] Embodiment 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 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 conversion reactor 10, a carbon capture unit 11 and a combined cycle unit 12. Among them:

[0084] The dryer 1 can implement the above step S1, and is used to heat the raw biomass 13 using the waste heat of the second exhaust flue gas 24 discharged from the air preheater 3 to produce dried biomass. In a preferred embodiment, the dried biomass has two destinations, because the produced dried biomass is divided into the first dried biomass 15 and the second dried biomass 16. The first exhaust flue gas 14 after heat exchange of the 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 heat the air 22 with the high temperature flue gas 21 generated by the burner 2 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 pretreatment unit 4 can implement the above step S1, and is used to dry and crush the raw coal 25 into coal 26 for pyrolysis.

[0088] The low temperature pyrolysis furnace 5 can implement the above step S3, and is used to pyrolyze the coal 26 for pyrolysis and the second dry biomass 16 using the first pyrolysis heat 18 to produce semi-coke 28 and low temperature pyrolysis gas 27. 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 implement the above step S4, and is used to pyrolyze the semi-coke 28 to produce coke 30 and high-temperature pyrolysis gas 29 using the second pyrolysis heat 19 .

[0090] The gasifier 7 can implement the above step S5 and is used to heat the coke 30 and the high-temperature gasifying agent 33 using the gasification heat 20 to gasify the coke to generate the high-temperature synthesis gas 31 .

[0091] The heat exchanger 8 can implement the above step S6, and is used to heat the gasifying agent 32 with 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 gasifying agent 33, and provide it to the gasifier 7. The low-temperature mixed gas 34 generated after the heat exchange is provided to the tar separation device 9.

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

[0093] The water gas shift reactor 10 can implement the above step S8, convert the carbon monoxide in the pure mixed gas 36 into carbon dioxide and hydrogen through the water gas shift reaction, and obtain the conversion gas 37 mainly composed of carbon dioxide and hydrogen.

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

[0095] The combined cycle unit 12 can implement the above step S10 to generate electricity 40 using the relatively pure hydrogen 39 as fuel.

[0096] The dryer 1 may be an airflow dryer, and the coal pretreatment unit 4 may use existing equipment, such as a coal mill, etc. The low-temperature pyrolysis furnace 5 and the high-temperature pyrolysis furnace 6 may be a heating furnace, a soaking furnace or a calcining furnace.

[0097] Examples

[0098] In order to further illustrate the feasibility of the present invention, a typical operating condition is selected and the power generation process is simulated. In the selected operating condition, coal is used as fuel for graded pyrolysis and gasification, and 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] In order to illustrate the difference between the components of low-temperature pyrolysis gas and high-temperature pyrolysis gas, Table 2 shows the mole fractions of the main components of low-temperature and high-temperature pyrolysis gas in the simulation calculation results.

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

[0101] Table 1 Basic parameters of the example

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

[0103] Table 2 Mole fractions of 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 specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for power generation based on complementary gasification of coal and biomass, characterized in that: include: Step S1, using the heat of flue gas generated by a burner to preheat air and dry biomass; Step S2, drying the biomass and burning the hot air to generate pyrolysis heat, including a first pyrolysis heat and a second pyrolysis heat; the first pyrolysis heat is less than the second pyrolysis heat; Step S3, the first pyrolysis heat is used to heat the low-temperature pyrolysis furnace to pyrolyze the coal to generate semi-coke and low-temperature pyrolysis gas; Step S4, the second pyrolysis heat is used to heat the high-temperature pyrolysis furnace to pyrolyze the semi-coke to generate coke and high-temperature pyrolysis gas; 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, drying the biomass and burning the hot air to generate gasification heat, which is used to heat the gasifier to gasify the coke to generate synthesis gas; Step S6: The low-temperature pyrolysis gas, the high-temperature pyrolysis gas and the synthesis gas form a high-temperature mixed gas, and the heat of the high-temperature mixed gas is recovered by a heat exchanger to heat the gasifying agent, and the heated gasifying agent enters the gasifier; Step S7, removing tar from the low-temperature mixed gas generated by heat exchange to generate a pure mixed gas; Step S8, the pure mixed gas undergoes a water vapor shift reaction to generate a conversion gas; Step S9, separating carbon dioxide from the conversion gas through a carbon dioxide capture unit to obtain hydrogen with higher purity; Step S10: Use high-purity hydrogen as fuel for the combined cycle unit to produce electricity.

2. The method according to claim 1, characterized in that Step S3 is further to introduce dry biomass into the low-temperature pyrolysis furnace, and the low-temperature pyrolysis furnace utilizes the first heat to pyrolyze the mixture of biomass and coal.

3. The method according to claim 1, characterized in that The first pyrolysis heat supports an operating temperature range of 200-1000°C for the low-temperature pyrolysis furnace; the second pyrolysis heat supports an operating temperature range of 600-1500°C for the high-temperature pyrolysis furnace; and at the same time, the operating temperature of the low-temperature pyrolysis furnace is lower than the operating temperature of the high-temperature pyrolysis furnace.

4. The method according to claim 1, characterized in that In step S1, the biomass drying temperature is in the range of 100-150°C.

5. The method according to claim 1, characterized in that In step S5, the gasification temperature is 900-1500°C; in step S6, the gasification agent is water vapor, carbon dioxide or oxygen.

6. The method according to claim 1, characterized in that In step S8, the temperature range of the water gas shift reaction is 200-500°C.

7. The method according to claim 1, characterized in that In step S7, the tar removal method is a water washing method or an adsorption method; in step S9, the carbon dioxide capture unit uses a chemical absorption method or a physical absorption method to separate the carbon dioxide in the conversion gas.

8. A power generation system based on complementary gasification of coal and biomass, characterized in that: The system includes: A dryer (1) is used to utilize the heat of the second exhaust gas (24) discharged from the air preheater (3) to heat the biomass to generate dry biomass, the dry biomass is provided to the burner (2) as fuel, and the first exhaust gas (14) after heat exchange is discharged into the environment; A burner (2) is used to burn dry biomass and hot air (23) to generate heat (17) and high-temperature flue gas (21), wherein the heat (17) includes a first pyrolysis heat (18), a second pyrolysis heat (19) and a gasification heat (20); the first pyrolysis heat is less than the second pyrolysis heat; The air preheater (3) is used to utilize the high-temperature flue gas (21) generated by the burner (2) to heat air to produce hot air (23), which is provided to the burner (2); the first exhaust flue gas (24) generated by heat exchange enters the dryer (1); A low-temperature pyrolysis furnace (5) for pyrolyzing coal (26) for pyrolysis using a first pyrolysis heat (18) to produce semi-coke (28) and low-temperature pyrolysis gas (27); A high-temperature pyrolysis furnace (6) is used to pyrolyze the semi-coke (28) using a second pyrolysis heat (19) to produce coke (30) and high-temperature pyrolysis gas (29); the volume fraction of carbon dioxide contained in the low-temperature pyrolysis gas is greater than that in the high-temperature pyrolysis gas; A gasifier (7) for heating the coke (30) and the gasifying agent (33) heated by the heat exchanger (8) using the gasification heat (20) to gasify the coke (30) and generate synthesis gas (31); The heat exchanger (8) is used to heat the gasifying 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 the heated gasifying agent is provided to the gasifier (7); the low-temperature mixed gas (34) generated after the 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 generate a pure mixed gas (36); A water gas shift reactor (10) converts the carbon monoxide in the pure mixed gas (36) into carbon dioxide through a water gas shift reaction, and obtains a 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) and producing hydrogen (39); A combined cycle unit (12) is used to generate electricity using the hydrogen (39) as fuel.

9. The system according to claim 8, characterized in that The system further comprises a coal pre-processing unit (4) for pulverizing and drying the coal to generate the coal for pyrolysis (26) and provide it to the low-temperature pyrolysis furnace (5).

10. The system according to claim 8, characterized in that There is a conveying channel between the dryer (1) and the low-temperature pyrolysis furnace (5). According to the required blending ratio of biomass and coal, the dried biomass enters the low-temperature pyrolysis furnace (5) through the conveying channel, and the low-temperature pyrolysis furnace (5) pyrolyzes the blend of dried biomass and coal using a first pyrolysis heat; the blending ratio is greater than or equal to 0.

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