Staged gasification combustion system and combustion method for coal fuel

Abstract

The present invention provides a staged gasification combustion system and a combustion method for coal fuel, comprising: a pyrolyzer adapted to subject coal fuel to a pyrolysis reaction and absorb heat to obtain char particles, tar and pyrolysis gas; a pyrolysis product purification and separation unit adapted to separate the tar and pyrolysis gas from the pyrolyzer to obtain separated tar and separated pyrolysis gas; a gasifier adapted to subject the char particles from the pyrolyzer and the tar from the pyrolysis product purification and separation unit to a gasification reaction with a gasifying agent preheated by a waste heat boiler and release heat to prepare synthesis gas; and a waste heat boiler adapted to subject the pyrolysis gas from the pyrolysis product purification and separation unit to a reforming reaction with water in the synthesis gas to obtain reformed gas; wherein the pyrolysis gas comprises methane, ethane and ethylene. The present invention utilizes the sensible heat of high-temperature synthesis gas to preheat the gasifying agent and drive the reforming of pyrolysis gas, realizing the cascade utilization of thermal energy.

Description

Technical Field

[0001] The present invention relates to the technical fields of energy utilization and fuel combustion, and particularly relates to a staged gasification combustion system and combustion method for coal fuel. Background Art

[0002] Currently, the mainstream of the energy system is traditional fossil fuels represented by coal, petroleum, and natural gas. Among them, coal is an important primary energy source, and its main utilization method is coal-fired power generation. However, direct combustion of coal will produce a relatively large amount of pollutants, such as SO x 、NO x 、dust, etc. Discharged into the environment, they will pollute the atmosphere and cause relatively serious environmental problems. In addition, the CO2 emitted by burning coal will cause the greenhouse effect when discharged into the atmosphere.

[0003] Coal gasification can convert coal from a solid fuel into a clean gas fuel. However, traditional coal gasification technologies still have some problems. Such as relying on the reaction of part of the coal with oxygen to supply heat for the gasification process, a large consumption of pure oxygen, a relatively large heat transfer temperature difference in the cooling process of high-temperature syngas, and a relatively low cold gas efficiency (70%-85%), etc.

[0004] Therefore, it is necessary to find a coal fuel combustion system to solve the above problems. Summary of the Invention

[0005] In view of at least one or a part of the above technical problems, embodiments of the present invention provide a staged gasification combustion system and combustion method for coal fuel, which can decouple the coal gasification process into a pyrolysis process and a gasification process, reduce the share of direct combustion of coal fuel, and reduce the heat transfer temperature difference in the gasifier.

[0006] To achieve the above object, as one aspect of the present invention, there is provided a staged gasification combustion system for coal fuel, including: a pyrolyzer, adapted to subject coal fuel to a pyrolysis reaction and absorb heat to obtain char particles, tar, and pyrolysis gas; a pyrolysis product purification and separation unit, adapted to separate the tar and pyrolysis gas from the pyrolyzer to obtain separated tar and separated pyrolysis gas; a gasifier, adapted to subject the char particles from the pyrolyzer and the tar from the pyrolysis product purification and separation unit to a gasification reaction with a gasifying agent preheated by a waste heat boiler and release heat to prepare syngas; and a waste heat boiler, adapted to subject the pyrolysis gas from the pyrolysis product purification and separation unit to a reforming reaction with water in the syngas and obtain reformed gas; wherein the pyrolysis gas includes methane, ethane, and ethylene.

[0007] In one embodiment, the waste heat boiler preheats the gasifying agent required for the gasification reaction by using the heat in the first temperature range of the syngas from the gasifier; and the waste heat boiler provides energy for the reforming reaction of the pyrolysis gas by using the heat in the second temperature range of the syngas from the gasifier; wherein, the temperature of the first temperature range is higher than that of the second temperature range.

[0008] In one embodiment, it further includes: a syngas purification unit, which is suitable for purifying the syngas; and a pre-combustion CO2 capture unit, which is suitable for reacting CO in the syngas to obtain CO2, and capturing the CO2 and discharging it from the combustion system.

[0009] In one embodiment, it further includes: a gas turbine, which is suitable for mixing and burning hydrogen in the syngas with air to obtain high-temperature flue gas and generate first heat and second heat, and converting the generated first heat into electrical energy for output to the system; a diverter, which is suitable for diverting the second heat from the gas turbine, so that a part of the second heat is transferred to the pyrolyzer to provide heat for the pyrolysis reaction of the coal fuel, and another part of the second heat is transferred to the waste heat boiler; the waste heat boiler, which is suitable for recovering the sensible heat of the high-temperature flue gas from the gas turbine and another part of the second heat; and a steam turbine, which uses the steam from the waste heat boiler to expand and generate electricity.

[0010] In one embodiment, it further includes an air separation unit, which is suitable for purifying the introduced oxygen; and a second mixer, which is suitable for mixing air with the purified oxygen to obtain a gasifying agent, and introducing the gasifying agent into the waste heat boiler.

[0011] In one embodiment, a first mixer is further provided in the waste heat boiler and the syngas purification unit.

[0012] In one embodiment, the pre-combustion CO2 capture unit includes a CO2 conversion unit and a CO2 capture unit. The CO2 conversion unit is suitable for oxidizing CO in the syngas to obtain CO2; the CO2 capture unit is suitable for capturing the obtained CO2 and discharging it from the combustion system.

[0013] As another aspect of the present invention, a combustion method is provided, which uses the combustion system as described above. The method includes:

[0014] Feeding the coal fuel into the pyrolyzer, carrying out a pyrolysis reaction and absorbing heat to obtain semi-coke particles, tar and pyrolysis gas;

[0015] Feeding the tar and pyrolysis gas obtained by pyrolysis into the pyrolysis product purification and separation unit for separation, and respectively inputting the separated tar and the semi-coke particles obtained by pyrolysis into the gasifier to carry out a gasification reaction with the gasifying agent preheated by the waste heat boiler to prepare syngas; and

[0016] The pyrolysis gas from the pyrolysis product purification and separation unit is input into the waste heat boiler and undergoes a reforming reaction with the water in the syngas to obtain reformed gas.

[0017] In one of the embodiments, the reformed gas includes CO and H₂; the syngas includes CO, H₂, H₂O, and CO₂.

[0018] In one of the embodiments, the temperature of the syngas before entering the waste heat boiler is 1300 - 1500 °C; the temperature of the mixed gas of the low-temperature syngas and the reformed gas at the outlet of the waste heat boiler is 200 - 300 °C.

[0019] Based on the staged gasification combustion system and combustion method of coal fuel according to the above embodiments of the present invention, the process of coal gasification is decoupled into a pyrolysis process and a gasification process. First, a part of the heat is used to pyrolyze the coal fuel to obtain char particles, tar, and pyrolysis gas. The char particles are input into the gasifier for gasification, and the tar and pyrolysis gas are separated in the pyrolysis product and separation unit. Then, the tar is introduced into the gasifier, and the heat released by the syngas at the outlet of the gasifier is used to preheat the gasification agent respectively, and drive the reforming of methane, ethylene, and ethane in the pyrolysis gas, so that the carbon and hydrogen in methane, ethane, and ethylene in the pyrolysis gas are decoupled, reducing the direct oxidation share of the coal fuel and lowering the irreversible loss in the gasification process. The sensible heat of the high-temperature syngas in the gasifier is used to preheat the gasification agent and drive the reforming of the pyrolysis gas, which can utilize the heat in a cascade manner and reduce the heat transfer temperature difference in the gasifier. Description of the Drawings

[0020] The present invention will be further described in detail below with reference to the drawings.

[0021] Figure 1 Shows a block diagram of the staged gasification combustion system of coal fuel in an embodiment of the present invention; and

[0022] Figure 2 Shows a flowchart of the method for staged gasification combustion of coal fuel in an embodiment of the present invention.

[0023]

Explanation of the Reference Numerals in the Drawings

[0024] 1 - Pyrolyzer, 2 - Air separation unit, 3 - Pyrolysis product purification and separation unit, 4 - Gasifier, 5 - Waste heat boiler, 6 - First mixer, 7 - Syngas purification unit, 8 - Pre - combustion CO2 capture unit, 9 - Gas turbine, 10 - Shunt, 11 - Waste heat boiler, 12 - Steam turbine, 13 - Second mixer, s1 - Coal fuel, s2 - Semi - coke particles, s3 - Air, s4 - High - temperature syngas, s5 - Syngas, s6, s7 are both mixtures of syngas, s8 - Carbon dioxide, s9 - Mixture of hydrogen and steam, s10, s11, s14, s15 are all high - temperature flue gases, s12, s21 are both water, s13 - Steam, s16 - Mixture of tar and pyrolysis gas, s17 - Pyrolysis gas, s18 - Reformed gas, s19 - Tar, s20 - Oxygen, s22 - Gasifying agent, s23 - Pre - heated gasifying agent, P - Electric energy output. Detailed implementation mode

[0025] The composition of coal fuel is relatively complex, and it contains many chemical bonds or chemical chains that are easy to break. With different coal qualities of coal fuel, the breaking situations of the chemical bonds and chemical chains are different. Traditional coal gasification does not specifically distinguish different coal fuels, but directly transports them into the gasifier for gasification reaction to convert them into carbon monoxide and hydrogen. In the process of realizing the concept of the present invention, it is found that by decoupling the coal gasification process into a pyrolysis process and a gasification process, the proportion of direct coal combustion can be reduced.

[0026] Therefore, the embodiments of the present invention provide a staged gasification combustion system and combustion method for coal fuel, which can use the heat obtained from the gasification reaction in the gasifier to pre - heat the gasifying agent and drive the reforming of pyrolysis gas, so that the carbon and hydrogen in methane, ethane and ethylene in the pyrolysis gas are decoupled, reducing the irreversible loss in the gasification process.

[0027] In this article, the decoupling of carbon and hydrogen refers to the process of decomposing compounds containing carbon and hydrogen such as methane, ethylene or ethane into carbon monoxide and hydrogen through a reforming reaction, specifically referring to the process of disconnecting the connection between carbon and hydrogen elements in the compound to make them into separate elements or compounds.

[0028] To make the purpose, technical solution and advantages of the present invention clearer and more understandable, the following combines specific embodiments and refers to the attached drawings to further elaborate on the present invention in detail.

[0029] Specifically, as an aspect of the present invention, there is provided a coal fuel staged gasification combustion system, comprising: a pyrolyzer, a pyrolysis product purification and separation unit, a gasifier, and a waste heat boiler. The pyrolyzer is adapted to subject the coal fuel to a pyrolysis reaction and absorb heat to obtain char particles, tar, and pyrolysis gas. The pyrolysis product purification and separation unit is adapted to separate the tar and pyrolysis gas from the pyrolyzer to obtain separated tar and separated pyrolysis gas. The gasifier is adapted to subject the char particles from the pyrolyzer and the tar from the pyrolysis product purification and separation unit to a gasification reaction with a gasifying agent preheated by the waste heat boiler and release heat to produce syngas. The waste heat boiler is adapted to subject the pyrolysis gas from the pyrolysis product purification and separation unit to a reforming reaction with the water in the syngas and obtain reformed gas. The pyrolysis gas includes methane, ethane, and ethylene.

[0030] Figure 1 FIG. shows a block diagram of a coal fuel staged gasification combustion system according to an embodiment of the present invention.

[0031] The following will be combined with Figure 1 to describe in detail a coal fuel staged gasification combustion system in an embodiment of the present invention.

[0032] Specifically, as Figure 1 shown, the coal fuel staged gasification combustion system provided by the embodiment of the present invention includes a pyrolyzer 1, a pyrolysis product purification and separation unit 3, a gasifier 4, and a waste heat boiler 5.

[0033] The pyrolyzer 1 is a closed structural unit made of a high-temperature resistant alloy material. Specifically, a heating furnace, a reactor, and a discharge device can be set as needed. Among them, the heating furnace can select electric heating, oil and gas heating, or steam heating and other methods to keep the inside of the pyrolyzer 1 in a relatively high temperature state; the reactor can control the flow of reaction gas and temperature change; the discharge device can install multiple branch pipes as needed to discharge the generated gas and solid particles respectively. The pyrolyzer 1 is adapted to convert the coal fuel into solid char particles, liquid tar, and gaseous pyrolysis gas by heating and decomposing the coal fuel at a relatively high temperature. According to needs, the outlet of the solid product on the heat absorption side of the pyrolyzer 1 can be connected to the gasifier 4, and the char particles s2 are transported to the gasifier 4 through the branch pipe of the solid product outlet. The outlets of the liquid and gaseous products on the heat absorption side of the pyrolyzer 1 are connected to the pyrolysis product purification and separation unit 3, and the mixture s16 of tar and pyrolysis gas can be transported to the pyrolysis product purification and separation unit 3 through the branch pipe of this outlet.

[0034] The pyrolysis product purification and separation unit 3 is provided with a feed inlet, a closed reaction chamber, a cooler, a purification device, a separation device, and a discharge outlet. Among them, the feed inlet mainly feeds the mixture of tar and pyrolysis gas obtained from the pyrolysis reaction into the closed reaction chamber for treatment; the closed reaction chamber can be set as a spherical or cylindrical structure to maintain the constancy of the reaction temperature and pressure; the cooler, through a cooling medium, such as water, quickly cools down the passing reaction products; the purification device is suitable for removing the mixed impurities from the reaction mixture to make the reaction products cleaner; the separation device can be provided with membrane separation, extraction, or rectification methods as needed to separate the purified mixture of tar and pyrolysis gas s16; the discharge outlet transports the separated tar to the gasifier 4 through a branch pipeline and transports the separated pyrolysis gas to the waste heat boiler 5 through another branch pipeline. The pyrolysis product purification and separation unit 3 is mainly used to separate the mixture of tar and pyrolysis gas s16 and transport them separately.

[0035] The gasifier 4 is set as a fixed bed or fluidized bed structure, and its overall equipment layout can be set as a vertical structure according to needs, including a fuel addition end, a gas discharge end, and a heating furnace. The fuel addition end, gas discharge end, and heating furnace can be arranged on the same plane as needed to facilitate operation and maintenance. The gasifier 4 is used to carry out gasification reactions of the semicoke particles from the pyrolyzer 1 and the tar from the pyrolysis product purification and separation unit 3 with the preheated gasifying agent s23 respectively and release heat, thereby preparing high-temperature synthesis gas s4.

[0036] The waste heat boiler 5 can be provided with a furnace body, a smoke exhaust duct, a waste heat recovery device, an air preheater, a dust collector, and a flue according to needs. The waste heat boiler 5 belongs to a type of heat exchanger and is mainly used for heat transfer. In the embodiment of the present invention, the waste heat boiler includes round and / or square tubes and plates, which are composed of parallel pipes arranged side by side, and the pipes can be fastened by welding and / or bolts as needed. During heat transfer, the high-temperature synthesis gas s4 flowing out of the gasifier outlet is cooled, and then the heat is transferred to the pyrolysis gas s17 in another pipe to be used for the reforming reaction of the pyrolysis gas s17 with the water in the high-temperature synthesis gas s4 to obtain reformed gas s18. It should be noted that these different gases always remain in different channels to prevent their mixing. Valves and / or automatic regulators for adjusting the flow rate can be set as needed to control the heat transfer, thereby achieving the purpose of controlling the temperature for heating and cooling. Among them, the pyrolysis gas includes methane, ethane, and ethylene; the gasifying agent s22 is a mixture of introduced oxygen and water.

[0037] More specifically, the coal fuel s1 is input into the pyrolysis furnace 1 through a conveying pipeline, and a pyrolysis reaction occurs to obtain semicoke particles s2, a mixture s16 of tar and pyrolysis gas. Among them, the semicoke particles s2 are conveyed through a pipeline connection to the gasification furnace 4 for a gasification reaction and release heat. The mixture s16 of tar and pyrolysis gas is conveyed through another pipeline to the pyrolysis product purification and separation unit 3. Through the separation device in the pyrolysis product purification and separation unit 3, the mixture s16 of tar and pyrolysis gas is separated. The separated tar is conveyed through a branch pipeline to the gasification furnace 4 for a gasification reaction to prepare high-temperature synthesis gas s4 and release heat. The separated pyrolysis gas is conveyed through another branch pipeline to the waste heat boiler 5. Among them, the heat released by the gasification reaction of tar and semicoke particles s2 with the preheated gasifying agent s23 in the gasification furnace 4 to prepare high-temperature synthesis gas s4 is used to preheat the preheated gasifying agent s23 before entering the gasification furnace and drive the reforming of pyrolysis gas. Among them, the sensible heat of the high-temperature synthesis gas s4 is used to preheat the gasifying agent, saving the supplementary combustion equipment before the gasifying agent enters the gasification furnace. The preheated gasifying agent s23 is then introduced into the gasification furnace to react with the semicoke particles s2, reducing the preheat of the reactants. Then, the sensible heat of the high-temperature synthesis gas s4 is used to drive the reforming reaction of pyrolysis gas s17 to drive the reforming of methane, ethylene, and ethane therein, decoupling carbon and hydrogen in the pyrolysis gas s17, reducing the direct oxidation share of coal fuel, realizing the cascade utilization of chemical energy, and reducing the irreversible loss in the gasification process.

[0038] In an embodiment of the present invention, the waste heat boiler 5 uses the heat in the first temperature range of the high-temperature synthesis gas s4 from the gasification furnace 4 to preheat the gasifying agent s22 required for the gasification reaction; and the waste heat boiler 5 uses the heat in the second temperature range of the high-temperature synthesis gas s4 from the gasification furnace 4 to provide energy for the reforming reaction of pyrolysis gas s17; the temperature in the first temperature range is higher than that in the second temperature range. Through the cascade utilization of different temperature segments, the full utilization of chemical energy is further realized, and the heat transfer temperature difference in the gasification furnace is further reduced.

[0039] In an embodiment of the present invention, a first mixer 6 is further provided in the waste heat boiler 5 and the syngas purification unit 7. The inlet of the first mixer 6 is connected to the waste heat boiler 5 through a pipeline, so that the syngas s5 from the waste heat boiler 5 is introduced into the first mixer 6; the other inlet of the first mixer 6 is connected to the reforming reaction device from the waste heat boiler 5 through a pipeline, so that the reformed gas s18 is input into the first mixer 6 through the pipeline to be fully mixed with the syngas s5. The temperature of the high-temperature syngas s4 discharged from the gasifier is 1300-1500°C, and the temperature of the syngas s5 obtained when it is discharged through the branch pipeline after heat exchange and cooling in the waste heat boiler 5 is 210-250°C. It should be noted that the components of the reformed gas s18 include hydrogen and carbon monoxide, and the components of the syngas s5 include a mixture of hydrogen, carbon monoxide, carbon dioxide and water vapor. The two only have slightly different contents of hydrogen and carbon monoxide components. Therefore, after being fully mixed in the first mixer 6, the mixture gas formed when flowing out of the first mixer 6 is collectively referred to as the mixture gas s6 of syngas.

[0040] In an embodiment of the present invention, the combustion system further includes: an air separation unit 2, which is suitable for purifying the introduced oxygen; and a second mixer 13, which is suitable for mixing air with the purified oxygen to obtain the gasifying agent s22 and introducing the gasifying agent s22 into the waste heat boiler 5. The air separation unit 2 has a double-flow structure, including a container-type outer shell and an internal partition. The processes are connected by pipelines, and the processes can be composed of fillers or membranes as needed. The air separation unit 2 is mainly used to separate and purify the introduced air s3, so that the gas flowing out of the air separation unit 2 is oxygen s20. The introduced water s21 enters the second mixer 13 to be fully mixed with the oxygen s20 from the air separation unit 2, and forms the gasifying agent s22 to be transported to the waste heat boiler 5 through a pipeline for preheating.

[0041] In an embodiment of the present invention, the combustion system further includes: a syngas purification unit 7 and a pre-combustion CO2 capture unit 8. Among them, the syngas purification unit 7 is suitable for purifying the syngas s5; and the pre-combustion CO2 capture unit 8 is suitable for reacting CO in the syngas to obtain CO2 and capturing the CO2 and discharging it from the combustion system.

[0042] Specifically, the syngas purification unit 7 is mainly used to remove impurities and ash in the syngas s5, so as to ensure the purity and quality of the syngas s5. The syngas purification unit 7 is provided with a filter. For example, mechanical filtration can be used to remove large particle impurities in the syngas s5, and then a chemical adsorbent is added to the adsorption tower to adsorb the ash and other impurity gases in the syngas s5. The syngas purification unit 7 can also be equipped with a demister as needed to remove the liquid water and grease in the adsorbed syngas, so as to avoid affecting the subsequent equipment. The pre-combustion CO2 capture unit 8 is used to capture carbon dioxide in the mixed gas s7 of the syngas, reduce its emissions, thereby reducing greenhouse gas emissions and being beneficial to environmental protection.

[0043] Further, the pre-combustion CO2 capture unit 8 includes a CO2 conversion unit and a CO2 capture unit. The CO2 conversion unit is suitable for oxidizing CO in the syngas to obtain CO2; the CO2 capture unit is suitable for capturing the obtained carbon dioxide s8 and discharging it from the combustion system. The pre-combustion CO2 capture unit 8 can also be provided with an air inlet and a pressure relief device. The mixed gas s7 of the syngas is introduced into the pre-combustion CO2 capture unit 8 through the air inlet. First, the CO in the mixed gas s7 of the syngas is oxidized by the CO2 conversion unit to generate CO2. The gas coming out of the outlet of the CO2 conversion unit only includes water vapor, CO2 and hydrogen. Then, it passes through the CO2 capture unit, and the adsorbent layer therein is used to capture and store the carbon dioxide s8. Then, the pressure relief device is used to treat the adsorbent layer adsorbed with carbon dioxide, release the carbon dioxide s8 therein and discharge it from the system. For example, a gas capture bag can be used to capture the carbon dioxide s8 discharged from the system. Using this capture method, 90% of the CO2 in the combustion system can be captured, realizing the clean, efficient and low-carbon utilization of coal and being beneficial to environmental protection.

[0044] In the embodiment of the present invention, the combustion system further includes: a gas turbine 9, a diverter 10, a waste heat boiler 11 and a steam turbine 12.

[0045] The gas turbine 9 is suitable for mixing and burning hydrogen in the mixed gas s9 of hydrogen and water vapor with the introduced air (not shown in the figure) to obtain flue gas and generate a first heat and a second heat, and converting the generated first heat into electric energy and outputting it from the system.

[0046] The diverter 10 is suitable for diverting the second heat from the gas turbine, transferring a part of the second heat to the pyrolyzer 1 to provide heat for the pyrolysis reaction of the coal fuel s1, and transferring another part of the second heat to the waste heat boiler 11.

[0047] The waste heat boiler 11 is suitable for recovering sensible heat from the high-temperature flue gas s11 from the gas turbine 9 and another part of the second heat.

[0048] The steam turbine 12 expands and generates electricity by using the water vapor s13 from the waste heat boiler 11.

[0049] Specifically, continuing as Figure 1 shown, the gas turbine 9 is provided with a first outlet and a second outlet. The mixture s9 of hydrogen and water vapor is introduced into the gas turbine 9 through a pipeline. The hydrogen therein burns in the gas turbine to heat and expand the introduced air, driving the turbine to rotate, and then driving the generator to work. The gas turbine 9 is provided with a compressor, a combustion chamber and a turbine as required. The compressor compresses the introduced air through a series of rotor blades and then enters the combustion chamber. Hydrogen fuel is injected into the combustion chamber, and after ignition and combustion, the first heat and the second heat are generated. The first heat drives mechanical equipment through the turbine for power output P of electricity.

[0050] The diverter 10 diverts the second heat from the gas turbine 9, transports a part of the second heat to the pyrolyzer 1 through a closed conveying pipeline to provide heat for the pyrolysis reaction of the coal fuel, and transfers another part of the second heat to the waste heat boiler 11 through a pipeline.

[0051] The structure of the waste heat boiler 11 mainly consists of a furnace body, a smoke exhaust duct, a waste heat recovery device and a condenser. The waste heat boiler 11 recovers the heat contained in the high-temperature flue gas s11 through devices such as the waste heat recovery device and the condenser, and then transfers the heat to the introduced water s12, so that the water vapor s13 is heated when flowing out of the waste heat boiler 11, thus making sufficient preparations for the next step of power generation. Therefore, the waste heat boiler is also a kind of heat exchanger. Compared with the waste heat boiler 5, the waste heat boiler 11 has a higher heat recovery efficiency, can greatly reduce energy consumption, and can also strengthen environmental protection and protect the environment.

[0052] Furthermore, the steam turbine 12 uses the energy generated by the water vapor s13 from the waste heat boiler 11 to drive the generator. The structure of the steam turbine 12 mainly includes a steam turbine. The steam turbine is a relatively key component of the steam turbine. There are a series of blades inside it. The water vapor s13 impacts the blades to generate a relatively large power in the turbine, thereby driving the mechanical equipment to work and finally driving the generator to generate electricity to achieve the power output P of electricity.

[0053] Figure 2 shows the method flow chart of staged gasification combustion of coal fuel in an embodiment of the present invention. As Figure 2 shown, the method of staged gasification combustion of coal fuel includes S201 - S203.

[0054] In operation S201, the coal fuel s1 is introduced into the pyrolyzer 1 for pyrolysis reaction and heat absorption to obtain a mixture s16 of semi-coke particles s2, tar and pyrolysis gas.

[0055] In operation S202, the mixture s16 of tar and pyrolysis gas obtained by pyrolysis is introduced into the pyrolysis product purification and separation unit 3 for separation. The separated tar s19 and the semi-coke particles s2 obtained by pyrolysis are respectively input into the gasifier 4 and gasified with the gasifying agent s23 preheated by the waste heat boiler to prepare high-temperature syngas s4.

[0056] In operation S203, the pyrolysis gas s17 from the pyrolysis product purification and separation unit 3 is introduced into the waste heat boiler 5 and reformed with the water in the high-temperature syngas s4 to obtain reformed gas s18.

[0057] In an embodiment of the present invention, the reformed gas includes CO and H2; the syngas includes CO, H2, H2O, and CO2.

[0058] In an embodiment of the present invention, the temperature of the high-temperature syngas s4 before entering the waste heat boiler 5 is 1300 - 1500 °C; the temperature of the mixture of the low-temperature syngas s5 and the reformed gas s18 at the outlet of the waste heat boiler 5 is 200 - 300 °C. Specifically, after the semi-coke particles s2 and the tar s19 enter the gasifier 4 from different inlets respectively, gasification reactions are carried out to release heat, so that the temperature of the high-temperature syngas s4 discharged from the gasifier 4 is 1300 - 1500 °C. The high-temperature syngas s4 is introduced into the waste heat boiler 5 to release heat, and the heat is transferred to the gasifying agent s22 introduced into another inlet of the waste heat boiler 5, raising the temperature of the gasifying agent s22 to between 800 - 1000 °C. The preheated gasifying agent s23 is introduced into the gasifier 4; the pyrolysis gas s17 from the pyrolysis product purification and separation unit 3, including methane, ethylene, and ethane, is heated to 700 - 900 °C after heat exchange in the waste heat boiler 5. Through the setting of the waste heat boiler 5, the sensible heat release of the syngas 4 is applied to the preheating and supplementary combustion of the gasifying agent s22 and the pyrolysis gas s17, further realizing the cascade utilization of chemical energy and reducing the heat exchange temperature difference in the gasifier.

[0059] It should be noted that a staged gasification combustion system and combustion method for coal fuel proposed in the embodiments of the present invention can decouple the coal gasification process into a pyrolysis process and a gasification process. The partial flue gas of the gas turbine 9 is used to heat the pyrolysis process of the coal fuel. The heat in the first temperature range of the high-temperature syngas s4 is used to preheat the gasifying agent s22 required by the gasifier 4, and the heat in the second temperature range of the high-temperature syngas s4 is used to drive the reforming of the pyrolysis gas s17. The heat in the first temperature range and the heat in the second temperature range are both heats with temperatures higher than 900 °C. The remaining heat lower than 900 °C is used for transfer in the combustion system, and finally steam is generated to drive the steam turbine to do work. In this way, by grading the utilization of the heat obtained from the combustion and gasification of coal fuel, the proportion of direct coal combustion can be reduced, and the oxygen demand and air separation energy consumption can be lowered. At the same time, the pre-combustion CO2 capture method can capture 90% of the CO2 in the system, and finally realize the clean, efficient and low-carbon utilization of coal.

[0060] The following further describes the staged gasification combustion system and combustion method for coal fuel in the embodiments of the present invention in conjunction with a specific embodiment. It should be understood that this specific embodiment is only for facilitating those skilled in the art to better understand the technical solution of the present invention, and should not be regarded as an inappropriate limitation of the protection scope of the present invention.

[0061] Embodiment 1

[0062] Continue as Figures 1 to 2As shown, the flow rate of coal fuel s1 fed into the staged gasification combustion system of the coal fuel used in the embodiment of the present invention is 62,727.34 kg / h, the pressure is 1.01 bar, and the temperature is 25 °C. This coal fuel s1 undergoes a pyrolysis reaction in the pyrolyzer 1 to obtain char particles s2 and a mixture s16 of tar and pyrolysis gas. The flow rate of the obtained char particles s2 is 41,553.54 kg / h, the pressure is 1.01 bar, and the temperature is 600 °C. The flow rate of the obtained mixture s16 of tar and pyrolysis gas is 20,821.80 kg / h, the pressure is 1.067 bar, and the temperature is 600 °C. After the mixture s16 of tar and pyrolysis gas is fed into the pyrolysis product purification and separation unit 3 for separation and purification treatment, the flow rate of the obtained pyrolysis gas s17 is 10,235.15 kg / h, the pressure is 1.067 bar, and the temperature is 76.40 °C. The flow rate of the obtained tar s19 is 8,843.33 kg / h, the pressure is 1.067 bar, and the temperature is 76.40 °C. The tar s19 and the char particles s2 respectively undergo a gasification reaction with the gasifying agent s23 in the gasifier 4 to obtain a high-temperature synthesis gas s4 with a flow rate of 158,862.82 kg / h, a pressure of 34.00 bar, and a temperature of 1400 °C. This high-temperature synthesis gas s4 includes CO2 with a mole fraction of 0.09, CO with a mole fraction of 0.27, H2 with a mole fraction of 0.25, H2O with a mole fraction of 0.28, and also includes N2 with a mole fraction of 0.11.

[0063] The flow rate of the fed water s21 is 54,434.57 kg / h, the pressure is 34.00 bar, and the temperature is 25.00 °C. The flow rate of the fed air s3 is 144,910.24 kg / h, the pressure is 1.01 bar, and the temperature is 25.00 °C. The air s3 flows through the air separation unit 2 for purification to obtain oxygen s20 with a flow rate of 35,277.70 kg / h, a pressure of 34.00 bar, and a temperature of 300.55 °C, and the proportion of the obtained oxygen is more than 95%. The oxygen s20 and the water s21 are mixed in the second mixer 13 to obtain a gasifying agent s22 with a flow rate of 89,712.27 kg / h, a pressure of 34.00 bar, and a temperature of 58.20 °C. After heat exchange with the high-temperature synthesis gas s4 in the waste heat boiler 5, the flow rate and pressure of the obtained gasifying agent s23 remain unchanged, and the temperature rises from 58.2 °C to 900.01 °C. Then, the gasifying agent s23 is fed into the gasifier 4 to undergo a gasification reaction with the char particles s2 and the tar s19.

[0064] The pyrolysis gas s17 separated by the pyrolysis product purification and separation unit 3 is introduced into the waste heat boiler 5 for reforming reaction. The heat released by the high-temperature syngas s4 is provided for the reforming reaction, so that the flow rate of the reformed gas s18 coming out of the waste heat boiler 5 is 10235.15 kg / h, the pressure is 1.067 bar, and the temperature is 850 °C. It is further mixed with the syngas s5 flowing out of the waste heat boiler 5 in the first mixer 6. The flow rate of the syngas s5 is 158862.82 kg / h, the pressure is 32.86 bar, and the temperature is 216.01 °C. After mixing, the flow rate and pressure of the mixed gas s6 of the syngas and the mixed gas s7 of the syngas after being treated by the syngas purification unit 7 do not change, which are 164610.27 kg / h and 32.58 bar respectively, and the temperature drops from 210.05 °C of s6 to 199.42 °C of s7. Then, CO2 is captured by the pre-combustion CO2 capture unit, and the obtained carbon dioxide s8 has a temperature of 39.37 °C, a pressure of 100.00 bar, and a flow rate of 121435.44 kg / h. The flow rate of the mixed gas s9 of hydrogen and water vapor after separation is 60837.34 kg / h, the pressure is 30.00 bar, and the temperature is 169.55 °C. It passes through the gas turbine 9 to make the hydrogen in it mix and burn with the introduced air to release heat. The flow rate of the high-temperature flue gas s10 coming out of the gas turbine 9 is 889224.32 kg / h, the pressure is 1.067 bar, and the temperature is 650 °C. The high-temperature flue gas s10 is split into s11 and s14 by the splitter 10. Among them, the flow rate of the high-temperature flue gas s11 is 806834.64 kg / h, the pressure is 1.067 bar, and the temperature is 650 °C. The flow rate of the high-temperature flue gas s14 is 82389.69 kg / h, the pressure is 1.067 bar, and the temperature is 650 °C. This high-temperature flue gas s14 is used to provide the heat for the pyrolysis of the coal fuel s1 in the pyrolyzer 1. The introduced water s12 has a temperature of 25 °C. After being heated by the high-temperature flue gas s11 in the waste heat boiler 11, the temperature of the water s13 when it comes out is 566 °C, and it flows into the steam turbine 12 for expansion power generation.

[0065] The simulation calculation is carried out on a coal fuel staged gasification combustion system in Embodiment 1 of the present invention, and it is compared with a conventional coal gasification pre-combustion CO2 capture power generation system. The parameters of each system are shown in Table 1.

[0066] Table 1 Energy balance table of two coal gasification power generation systems

[0067]

[0068] As can be seen from Table 1, under the conditions that the input energy is 397.78 MW and the carbon capture rate is 90% for both, the net power output of the coal fuel staged gasification combustion system is 160.13 MW, which is 7.11% higher than that of the conventional coal gasification combustion system with pre-combustion CO2 capture (149.50 MW). On the one hand, the electricity output from the gas turbine in the coal fuel staged gasification combustion system is much higher than that in the conventional coal gasification combustion system with pre-combustion CO2 capture. On the other hand, the energy consumption of the air separation unit and oxygen compressor in the coal fuel staged gasification combustion system is lower than that in the conventional coal gasification combustion system with pre-combustion CO2 capture. In the coal fuel staged gasification combustion system of the embodiment of the present invention, the waste heat of the gas turbine exhaust and sensible heat of the syngas are used to replace the heat released by direct coal combustion in the gasification process through the method of chemical recuperation. Finally, the net power generation efficiency of the power generation system reaches 40.26%, which is 2.68% higher than that of the conventional coal gasification combustion system with pre-combustion CO2 capture (37.58%). At the same time, the CO2 emission per kWh is 84.64 g / kWh, which is 6.63% lower than that of the conventional coal gasification combustion system with pre-combustion CO2 capture (90.65 g / kWh).

[0069] The coal fuel staged gasification combustion system and combustion method provided by the embodiment of the present invention mainly include: pyrolyzer 1, air separation unit 2, pyrolysis product purification and separation unit 3, gasifier 4, waste heat boiler 5, first mixer 6, syngas purification unit 7, pre-combustion CO2 capture unit 8, gas turbine 9, diverter 10, waste heat boiler 11, steam turbine 12. This combustion system decouples the coal gasification process into a pyrolysis process and a gasification process, uses the waste heat of the gas turbine 9 exhaust to provide heat for the coal pyrolysis process, obtains a part of pyrolysis gas s16, and the remaining product semi-coke particles s2 and tar s19 are sent to the gasifier 4 for gasification, reducing the share of direct coal fuel s1 combustion and the irreversible loss in the gasification process. In addition, the sensible heat of the high-temperature syngas s4 at the outlet of the gasifier 4 is used to preheat the gasifying agent s22 and drive the reforming of pyrolysis gas s17 respectively, realizing the cascade utilization of heat energy while reducing the heat transfer temperature difference in the gasifier 4, and completely decoupling the carbon and hydrogen in CH4, C2H4, and C2H6 in the pyrolysis gas s17. In addition, 90% of the CO2 in the system is captured by the pre-combustion CO2 capture unit 8, realizing the clean, efficient, and low-carbon utilization of coal fuel s1.

[0070] The specific embodiments described above further elaborate on the purpose, technical solutions, and beneficial effects of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not used to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A staged gasification combustion system for coal fuel, comprising: A pyrolyzer, adapted to subject the coal fuel to a pyrolysis reaction and absorb heat to obtain char particles, tar, and pyrolysis gas; A pyrolysis product purification and separation unit, adapted to separate the tar and pyrolysis gas from the pyrolyzer to obtain separated tar and separated pyrolysis gas; A gasifier, adapted to subject the char particles from the pyrolyzer and the tar from the pyrolysis product purification and separation unit to a gasification reaction with a gasifying agent preheated by a waste heat boiler and release heat to produce syngas; And A waste heat boiler, adapted to subject the pyrolysis gas from the pyrolysis product purification and separation unit to a reforming reaction with the water in the syngas to obtain reformed gas; Wherein, the pyrolysis gas includes methane, ethane, and ethylene; the waste heat boiler uses the heat in the first temperature range of the syngas from the gasifier to preheat the gasifying agent required for the gasification reaction; The waste heat boiler uses the heat in the second temperature range of the syngas from the gasifier to provide energy for the reforming reaction of the pyrolysis gas; Wherein, the temperature of the first temperature range is higher than that of the second temperature range. Through the setting of the waste heat boiler, the sensible heat release of the syngas is respectively applied to the preheating of the gasifying agent and the reforming of the pyrolysis gas.

2. The staged gasification combustion system according to claim 1, further comprising: A syngas purification unit, adapted to purify the syngas; And A pre-combustion CO2 capture unit, adapted to react the CO in the syngas to obtain CO2, capture the CO2, and discharge it from the staged gasification combustion system.

3. The staged gasification combustion system according to claim 2, further comprising: A gas turbine, adapted to mix and burn the hydrogen in the syngas with the introduced air to obtain high-temperature flue gas and generate first heat and second heat, and convert the generated first heat into electrical energy for output from the system; A diverter, adapted to divert the second heat from the gas turbine, so that a part of the second heat is transferred to the pyrolyzer to provide heat for the pyrolysis reaction of the coal fuel, and another part of the second heat is transferred to the waste heat boiler; A waste heat boiler, adapted to recover the sensible heat of the high-temperature flue gas from the gas turbine and another part of the second heat; And A steam turbine, which uses the steam from the waste heat boiler for expansion power generation.

4. The staged gasification combustion system according to claim 1, further comprising An air separation unit, adapted to purify the introduced oxygen; and A second mixer, adapted to mix air with the purified oxygen to obtain the gasifying agent and introduce the gasifying agent into the waste heat boiler.

5. The staged gasification combustion system according to claim 2, wherein, A first mixer is further provided between the waste heat boiler and the syngas purification unit.

6. The staged gasification combustion system according to claim 2, wherein The pre-combustion CO2 capture unit includes a CO2 conversion unit and a CO2 capture unit, The CO2 conversion unit is adapted to oxidize the CO in the syngas to obtain CO2; The CO2 capture unit is adapted to capture the obtained CO2 and discharge it from the staged gasification combustion system.

7. A combustion method using a staged gasification combustion system as described in any one of claims 1-6, the method comprising: Feeding coal fuel into a pyrolyzer for pyrolysis reaction and heat absorption to obtain char particles, tar, and pyrolysis gas; Feeding the tar and pyrolysis gas obtained by pyrolysis into a pyrolysis product purification and separation unit for separation, and respectively inputting the separated tar and the char particles obtained by pyrolysis into a gasifier to react with a gasifying agent preheated by a waste heat boiler to prepare synthesis gas; And Feeding the pyrolysis gas from the pyrolysis product purification and separation unit into the waste heat boiler to perform a reforming reaction with the water in the synthesis gas to obtain reformed gas.

8. The combustion method according to claim 7, wherein The reformed gas comprises CO and H2; The synthesis gas comprises CO, H2, H2O, and CO2.

9. The combustion method according to claim 7, wherein The temperature of the synthesis gas before entering the waste heat boiler is 1300-1500 °C; The temperature of the mixture of the low-temperature synthesis gas and the reformed gas at the outlet of the waste heat boiler is 200-300 °C.

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