A carbon dioxide and oxygen cogeneration system and its operating method

Abstract

This invention discloses a biomass gasification system and its operating method using carbon dioxide and oxygen as gasifying agents, belonging to the field of biomass gasification technology. It includes a biomass silo, a gasifier, a pyrolysis reactor, a biomass char silo, a burner, a high-temperature pyrolysis reactor, a gasification reactor, a heat exchanger, and a CO2 separation device. This invention achieves precise control of the biomass char to gasified gas ratio within a certain range by controlling the different proportions of CO2 and O2 in the gasifying agent within the gasification reactor, thus perfectly meeting the actual needs of engineering projects or users. This invention features a high degree of automation and flexible control, achieving CO2 fixation and reducing net CO2 emissions while simultaneously controlling the biomass char to gasified gas ratio within a certain range, thus perfectly meeting the actual needs of engineering projects or users and demonstrating promising application prospects.

Description

Technical Field

[0001] This invention belongs to the field of biomass gasification technology, specifically relating to a cogeneration system using carbon dioxide and oxygen as gasifying agents and its operating method. Background Technology

[0002] With the increasing depletion of fossil fuels and the growing prominence of environmental pollution, seeking a renewable energy source to replace fossil fuels has become a consensus. Biomass energy has attracted widespread attention due to its renewable and environmentally friendly advantages. Furthermore, in the context of a dual-carbon economy, achieving CO2 fixation and reducing CO2 emissions is particularly important for environmental protection and mitigating the greenhouse effect. Biomass, as a CO2-neutral and environmentally friendly new energy source, is formed by plants absorbing CO2 through photosynthesis. Its stored energy can be released through thermal conversions such as combustion and gasification, and it currently accounts for 14% of the world's energy consumption.

[0003] Biomass gasification is a highly promising technology that can generate not only heat but also high-calorific-value syngas for industrial production or power generation. Extensive experimental and simulation studies have been conducted on biomass gasification; however, the gasifying agents used are mostly air, water vapor, and mixtures thereof, with little research focusing on carbon dioxide gasification. CO2 is the primary contributor to global warming, and its treatment incurs significant economic costs. Therefore, carbon dioxide gasification technology is crucial for reducing CO2 emissions and improving industrial economics.

[0004] Furthermore, biomass, as a high-quality resource, produces high-calorific-value fuel gas during gasification, but also generates byproduct char. However, under normal conditions, the char produced by gasifiers is of low quality, insufficient in quality and activity for use as biomass char or activated carbon. Therefore, it is necessary to modify the pyrolysis conditions to improve the quality or activity of the byproduct char. Staged gasification allows for the control of reaction conditions, enabling the pyrolysis, reduction, and oxidation of biomass to occur in different reactors, and the reaction conditions of the pyrolysis stage can be adjusted to meet the demand for biomass char. However, the generation and utilization of biomass fuel gas are limited by geographical location and season. In areas rich in agricultural and forestry biomass, the biochar produced is of high quality and suitable for use in activated carbon, industrial char, and other industries, resulting in enormous demand. In summer, the demand for fuel gas for heating and warming from residential and industrial sources is lower than in winter, allowing byproduct char to be produced as the main product. Therefore, flexibly controlling the char-to-gas ratio is key to the future of industrial biomass gasification. Summary of the Invention

[0005] To address the aforementioned problems, the present invention aims to provide a biochar and gas cogeneration system and its operating method that uses carbon dioxide and oxygen as gasifying agents. This system achieves CO2 fixation and reduces net CO2 emissions while simultaneously allowing for the regulation of the ratio of biochar to gasified gas within a certain range, thereby perfectly meeting the actual needs of engineering projects or users.

[0006] This invention is achieved through the following technical solution:

[0007] The present invention discloses a cogeneration system for carbon dioxide and oxygen as gasification agents, comprising a biomass silo, a gasifier, a pyrolysis reactor, a biomass char silo, a burner, a high-temperature pyrolysis reactor, a gasification reactor, a heat exchanger, and a CO2 separation device.

[0008] The biomass feed silo is connected to the feed inlets of both the gasifier and the pyrolysis reactor. The gasification gas outlet of the gasifier is connected to the gasification gas inlet of the pyrolysis reactor, and the char outlet of the gasifier is connected to the char inlet of the burner. The gasifier is also connected to an O2 inlet pipe. The biomass char outlet of the pyrolysis reactor is connected to the first biomass char inlet of the biomass char silo, and the gasification gas outlet of the pyrolysis reactor is connected to the first gasification gas inlet of the high-temperature pyrolysis reactor. The biomass char outlet of the biomass char silo is connected to the biomass char inlet of the gasifier. The gasification gas outlet of the burner is connected to the second gasification gas inlet of the high-temperature pyrolysis reactor. The device is connected to an O2 inlet pipe; the gasification gas outlet of the high-temperature pyrolysis reactor is connected to the gasification gas inlet of the gasification reactor; the gasification gas outlet of the gasification reactor is connected to the gasification gas inlet of the heat exchanger; the O2 outlet of the heat exchanger is connected to the O2 inlet of the gasification reactor, and the gasification gas outlet of the heat exchanger is connected to the gasification gas inlet of the CO2 separation device; the heat exchanger is connected to an O2 inlet pipe; the first CO2 outlet of the CO2 separation device is connected to the CO2 inlet of the gasification reactor, and the second CO2 outlet of the CO2 separation device is connected to the CO2 inlet of the pyrolysis reactor; the CO2 separation device is connected to a gasification gas discharge pipe.

[0009] Preferably, a return valve is installed on the pipeline between the biomass silo and the raw material inlet of the gasifier and the pyrolysis reactor; a return valve is installed on the pipeline between the biomass char outlet of the biomass char silo and the biomass char inlet of the gasifier; a gasification gas inlet regulating valve is installed on the pipeline between the gasification gas outlet of the gasifier and the gasification gas inlet of the pyrolysis reactor; an O2 inlet regulating valve is installed on the pipeline between the O2 outlet of the heat exchanger and the O2 inlet of the gasifier; and a CO2 gas regulating valve is installed on the pipeline between the first CO2 outlet of the CO2 separator and the CO2 inlet of the gasifier.

[0010] Preferably, the high-temperature pyrolysis reactor includes a first chamber and a second chamber, which are separated by a partition. A high-temperature resistant ring pipe is provided in the first chamber. The inner inlet of the high-temperature resistant ring pipe is connected to the first gasification gas inlet, and the outer inlet of the high-temperature resistant ring pipe is connected to the second gasification gas inlet. The inner outlet and the outer outlet of the high-temperature resistant ring pipe are both connected to the second chamber. The gasification gas outlet of the high-temperature pyrolysis reactor is located on the second chamber.

[0011] More preferably, the inner tube of the high-temperature resistant ring tube is made of aluminum alloy, and the outer tube is made of stainless steel; the dimensions of the inner tube satisfy the following formula:

[0012]

[0013] In the formula, D i δ is the diameter of the inner tube, in meters; L is the length of the high-temperature resistant ring tube, in meters; δ is the wall thickness of the inner tube, in meters; the ratio of the gasification gas mass flow rate of the burner to the mass flow rate of the pyrolysis reactor is 3:1.

[0014] Preferably, the reaction temperature of the high-temperature pyrolysis reactor is 1100–1300°C.

[0015] Preferably, the heat exchanger is a shell-and-tube heat exchanger, with gasified gas in the tube side and O2 in the shell side.

[0016] Preferably, the oxygen concentration inside the burner is >70%.

[0017] Preferably, the CO2 separation device is a membrane separation type.

[0018] The operating method of the above-mentioned carbon dioxide and oxygen cogeneration system disclosed in this invention includes:

[0019] Biomass feedstock from the biomass silo enters a gasifier and a pyrolysis reactor. In the gasifier, the biomass feedstock undergoes a gasification reaction using O2 as the gasifying agent, producing char and gasified gas. In the pyrolysis reactor, the biomass feedstock undergoes a pyrolysis reaction under a CO2 atmosphere. The char produced by the gasifier is burned in a burner, and the resulting high-temperature gas enters a high-temperature pyrolysis reactor, providing heat for the pyrolysis reactor. The char produced by the pyrolysis reactor enters a biomass char bin and then enters the gasifier for the gasification reduction stage. The gasified gas produced by the gasifier enters the pyrolysis reactor, providing heat for the pyrolysis section. The gasified gas produced by the pyrolysis reactor enters the high-temperature pyrolysis reactor for high-temperature catalytic cracking of tar. The gasified gas produced by the high-temperature pyrolysis reactor enters the gasifier for gasification reduction, and the amount of system products is controlled by adjusting the amounts of CO2 and O2. The gasified gas produced by the gasifier enters a heat exchanger to exchange heat with O2, and the heated O2 enters the gasifier as a gasifying agent. The cooled gasified gas enters a CO2 separator, and the separated CO2 enters both the pyrolysis reactor and the gasifier.

[0020] Preferably, the temperature inside the gasification reactor is 800–900°C; the molar ratio of the gasifying agent to biochar inside the gasification reactor is 0.3–1.1, and the molar ratio of CO2 to O2 in the gasifying agent is 0–2.7; the final char yield is 10%–30%; the final char yield, the molar ratio of the gasifying agent to biochar, and the molar ratio of CO2 to O2 in the gasifying agent satisfy the following formula:

[0021]

[0022] In the formula, w is the final carbon yield, y is the molar ratio of gasifying agent to biochar, and z is the molar ratio of CO2 to O2 in the gasifying agent.

[0023] Compared with the prior art, the present invention has the following beneficial technical effects:

[0024] This invention discloses a cogeneration system for biomass char using carbon dioxide and oxygen as gasifying agents. Using CO2 as the gasifying agent, CO is produced through the gasification of CO2 and biomass char, achieving CO2 fixation, reducing net CO2 emissions, and providing good environmental benefits. It also reduces the energy required for water vapor evaporation; the H2 / CO ratio in the syngas is easily adjustable to meet specific industrial requirements; and it is beneficial for CO2 recycling and reducing net CO2 emissions. When used as a pyrolysis atmosphere, CO2 can improve and activate the structure of the char surface, thereby enhancing the quality and activity of the biomass char. In this invention, CO2 and O2 are introduced into the gasification reactor as gasifying agents. The reaction rate between char and O2 is extremely fast, being the main reaction consuming char, and the reaction rate varies with the O2 concentration. The reaction between char and CO2 is slower and also varies with the CO2 concentration. Furthermore, the reaction between char and CO2 is endothermic; adding CO2 lowers the temperature in the gasification reactor, thereby reducing the reaction rate between char and O2 and decreasing char consumption. Therefore, by controlling the different ratios of CO2 and O2 in the gasifying agent within the gasification reactor, the ratio of biochar to gasified gas can be regulated within a certain range, thus achieving a perfect match with the actual needs of the project or user. The system has feed inlets in both the gasifier and the pyrolysis reactor. The pyrolysis reactor produces high-quality biochar that meets the requirements of commercial biochar and can be discharged as a product, while the gasifier produces lower-quality by-product biochar that can be used for combustion to provide heat. Therefore, by controlling the ratio of biomass feedstock entering the two feed inlets, both high-quality and high-yield biochar can be achieved while simultaneously meeting heat supply requirements. The system connects the gasified gas outlet of the gasifier to the gasified gas inlet of the pyrolysis reactor, utilizing the high temperature of the gasified gas at the gasifier outlet to provide the heat required for the pyrolysis process. The high-temperature pyrolysis reactor in the system uses the heat provided by the combustion reaction in the burner to achieve high-temperature pyrolysis and removal of tar, significantly reducing the tar content in the gasified gas and its components. The system incorporates a heat exchanger that exchanges heat between the gas exiting the gasification reactor and the O2 gasifying agent entering the reactor. This prevents the gasifying agent from becoming too cold and lowering the reactor temperature, thus utilizing waste heat. The system consists of two complete gasification processes. One complete gasification process takes place in the gasifier furnace, where the drying, pyrolysis, oxidation, and reduction processes do not have clear boundaries, and the contact time between the gas and solid phases, and between the gasifying agent and the reactant, cannot be controlled. The other complete gasification process involves controlling different reaction conditions in separate reactors, achieving staged gasification of pyrolysis, oxidation, and reduction. This staged gasification allows for flexible distribution and control of the products.

[0025] Furthermore, by setting valves to control the rate at which the gasified gas enters the pyrolysis reactor, the temperature of the pyrolysis reactor can be controlled, thereby achieving rational utilization of heat while controlling the conditions of the pyrolysis reaction.

[0026] The working method of the biochar and gas cogeneration system using carbon dioxide and oxygen as gasifying agents disclosed in this invention has a high degree of automation and flexible control. While achieving CO2 fixation and reducing net CO2 emissions, it also enables the regulation of the ratio of biochar to gasified gas within a certain range, thus achieving a perfect fit with the actual needs of engineering projects or users and has good application prospects. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the overall system structure of the present invention.

[0028] In the diagram: 1-Biomass silo, 2-Gasifier, 21-Gasifier feed inlet, 22-Gasifier gas outlet, 23-Charcoal outlet, 24-Gasifier O2 inlet, 3-Pyrolysis reactor, 31-Pyrolysis reactor feed inlet, 32-Pyrolysis reactor gas outlet, 33-Pyrolysis reactor CO2 inlet, 34-Biomass char outlet, 35-Pyrolysis reactor gas outlet, 4-Biomass char silo, 41-First biomass char inlet, 42-Biomass char outlet, 43-Second biomass char inlet, 5-Burner, 51-Charcoal inlet, 52-Burner gas outlet, 53-Burner O2 inlet, 6-High-temperature pyrolysis reactor, 61-First gasification reactor 62-Second gasification gas inlet, 63-High-temperature pyrolysis reactor gasification gas outlet, 7-Gasification reactor, 71-Gasification reactor gasification gas inlet, 72-Biochar inlet, 73-Gasification reactor O2 inlet, 74-Gasification reactor CO2 inlet, 75-Gasification reactor gasification gas outlet, 76-Biochar outlet, 8-Heat exchanger, 81-Heat exchanger gasification gas inlet, 82-Heat exchanger O2 inlet, 83-O2 outlet, 84-Heat exchanger gasification gas outlet, 9-CO2 separation unit, 91-CO2 separation unit gasification gas inlet, 92-First CO2 outlet, 93-Second CO2 outlet, 94-CO2 separation unit gasification gas outlet. Detailed Implementation

[0029] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. This description is intended to explain the invention and not to limit it.

[0030] like Figure 1 The cogeneration system of carbon dioxide and oxygen as gasification agents of the present invention includes a biomass silo 1, a gasifier 2, a pyrolysis reactor 3, a biomass char silo 4, a burner 5, a high-temperature pyrolysis reactor 6, a gasification reactor 7, a heat exchanger 8, and a CO2 separation device 9.

[0031] The gasifier 2 is equipped with a gasifier raw material inlet 21, a gasifier gas outlet 22, a char outlet 23, and a gasifier O2 inlet 24.

[0032] The pyrolysis reactor 3 is equipped with a pyrolysis reactor raw material inlet 31, a pyrolysis reactor gasification gas inlet 32, a pyrolysis reactor CO2 inlet 33, a biochar outlet 34, and a pyrolysis reactor gasification gas outlet 35.

[0033] The biochar bin 4 is provided with a first biochar inlet 41, a biochar outlet 42, and a second biochar inlet 43.

[0034] The burner 5 is equipped with a carbon inlet 51, a burner gasification gas outlet 52, and a burner O2 inlet 53.

[0035] The high-temperature pyrolysis reactor 6 is provided with a first gasification gas inlet 61, a second gasification gas inlet 62, and a high-temperature pyrolysis reactor gasification gas outlet 63.

[0036] The gasification reactor 7 is equipped with a gasification gas inlet 71, a biomass char inlet 72, an O2 inlet 73, a CO2 inlet 74, a gasification gas outlet 75, and a biomass char outlet 76.

[0037] The heat exchanger 8 is provided with a heat exchanger vaporization gas inlet 81, a heat exchanger O2 inlet 82, an O2 outlet 83, and a heat exchanger vaporization gas outlet 84.

[0038] The CO2 separation device 9 is provided with a CO2 separation device gasification gas inlet 91, a first CO2 outlet 92, a second CO2 outlet 93 and a CO2 separation device gasification gas outlet 94.

[0039] Biomass silo 1 is connected to the gasifier feed inlet 21 and the pyrolysis reactor feed inlet 31 respectively. Gasifier gas outlet 22 is connected to pyrolysis reactor gas inlet 32. Charcoal outlet 23 is connected to charcoal inlet 51. Gasifier O2 inlet 24 is connected to an O2 inlet pipe. Biomass charcoal outlet 34 is connected to the first biomass charcoal inlet 41. Pyrolysis reactor gas outlet 35 is connected to the first gasifier gas inlet 61. Biomass charcoal outlet 42 is connected to biomass charcoal inlet 72. Burner gasification gas outlet 52 is connected to the second gasification gas inlet 62. Burner O2 inlet 53 is connected to an O2 inlet pipe. High-temperature pyrolysis reactor gasification gas outlet... Port 63 is connected to the gasification gas inlet 71 of the gasification reactor; the gasification gas outlet 75 of the gasification reactor is connected to the gasification gas inlet 81 of the heat exchanger; the O2 outlet 83 of the heat exchanger 8 is connected to the O2 inlet 73 of the gasification reactor, and the gasification gas outlet 84 of the heat exchanger is connected to the gasification gas inlet 91 of the CO2 separator, which is connected to an O2 inlet pipe; the first CO2 outlet 92 of the CO2 separator 9 is connected to the CO2 inlet 74 of the gasification reactor, and the second CO2 outlet 93 of the CO2 separator 9 is connected to the CO2 inlet 33 of the pyrolysis reactor; the gasification gas outlet 94 of the CO2 separator is connected to a gasification gas discharge pipe.

[0040] In a preferred embodiment of the present invention, a return valve is provided on the pipeline between the biomass silo 1 and the raw material inlet of the gasifier 2 and the pyrolysis reactor 3; a return valve is provided on the pipeline between the biomass char outlet of the biomass char silo 4 and the biomass char inlet 72 of the gasifier 7; a gasification gas inlet regulating valve is provided on the pipeline between the gasification gas outlet of the gasifier 2 and the gasification gas inlet of the pyrolysis reactor 3; an O2 inlet regulating valve is provided on the pipeline between the O2 outlet 83 of the heat exchanger 8 and the O2 inlet of the gasifier 7; and a CO2 gas regulating valve is provided on the pipeline between the first CO2 outlet 92 of the CO2 separation device 9 and the CO2 inlet of the gasifier 7.

[0041] In a preferred embodiment of the present invention, the high-temperature pyrolysis reactor 6 includes a first chamber and a second chamber, which are separated by a partition. A high-temperature resistant ring pipe is provided in the first chamber. The inner inlet of the high-temperature resistant ring pipe is connected to a first gasification gas inlet 61, and the outer inlet of the high-temperature resistant ring pipe is connected to a second gasification gas inlet 62. Both the inner and outer outlets of the high-temperature resistant ring pipe are connected to the second chamber. The gasification gas outlet of the high-temperature pyrolysis reactor 6 is located in the second chamber. Preferably, the inner tube of the high-temperature resistant ring pipe is made of aluminum alloy, and the outer tube is made of stainless steel. The dimensions of the inner tube satisfy the following formula:

[0042]

[0043] In the formula, D iδ is the diameter of the inner tube, in meters; L is the length of the high-temperature resistant ring tube, in meters; δ is the wall thickness of the inner tube, in meters; the ratio of the mass flow rate of the gasified gas in burner 5 to the mass flow rate of the pyrolysis reactor 3 is 3:1.

[0044] In a preferred embodiment of the present invention, the reaction temperature of the high-temperature pyrolysis reactor 6 is 1100–1300 °C.

[0045] In a preferred embodiment of the present invention, the heat exchanger 8 is a shell-and-tube heat exchanger, with gasified gas in the tube side and O2 in the shell side.

[0046] In a preferred embodiment of the invention, the oxygen concentration in the burner 5 is >70%.

[0047] In a preferred embodiment of the present invention, the CO2 separation device 9 is a membrane separation type.

[0048] The operating method of the above-mentioned cogeneration system using carbon dioxide and oxygen as gasifying agents includes:

[0049] Biomass silo 1 provides biomass feedstock to gasifier 2 and pyrolysis reactor 3. Gasifier 2 sequentially completes drying, pyrolysis, oxidation, and reduction processes to produce char and gasified gas. Pyrolysis reactor 3 performs the pyrolysis carbonization process. The gasifying agent in gasifier 2 is either O2 or air, with O2 being preferred. Pyrolysis reactor 3 has a CO2 inlet to create a CO2 atmosphere. It is worth noting that pyrolysis under a CO2 atmosphere is beneficial for the formation of a porous structure on the biochar surface and for increasing the aromatization degree of surface functional groups. Therefore, the char produced by gasifier 2 is of lower quality and has lower activity compared to that produced by pyrolysis reactor 3. Thus, the char produced in gasifier 2 is directly burned in burner 5 to provide heat to the system, while the char produced in pyrolysis reactor 3 is stored in biomass char bin 4 and then used in the gasification reduction stage via gasifier 7. Furthermore, for gasifier 2, since the gasified gas is discharged from the bottom of the gasifier, its temperature is relatively high. Considering the comprehensive utilization of energy, this portion of the gasified gas can be used to provide heat for the pyrolysis section in the pyrolysis reactor. Therefore, the gasifier gas outlet 22 of gasifier 2 is connected to the pyrolysis reactor gas inlet 32 ​​of pyrolysis reactor 3. Pyrolysis reactor 3 produces char and gasified gas through a pyrolysis reaction. However, the gasified gas produced during pyrolysis has a high tar content, so it needs to be introduced into high-temperature pyrolysis reactor 6 for high-temperature catalytic cracking of the tar. The energy required for high-temperature tar cracking is provided by the heat released when the char produced in gasifier 2 burns in burner 5. It is worth noting that the heat transfer is achieved through a gaseous medium, that is, the gas produced in burner 5 is directly introduced into high-temperature pyrolysis reactor 6, and the energy carried by the high-temperature gas provides a high-temperature atmosphere for tar cracking. In addition, the high-temperature pyrolysis reactor 6 integrates the gasified gas from gasifier 2, pyrolysis reactor 3, and burner 5, so that these three streams of gasified gas from different sources can be integrated into one stream and introduced into gasification reactor 7 for gasification and reduction. The main components of the gasified gas from gasifier 2 are CO, H2, and CO2; the main components of the gasified gas from pyrolysis reactor 3 after tar removal in high-temperature pyrolysis reactor 6 are CO, CO2, and CH4; and the main components of the gasified gas from burner 5 are CO and CO2. In gasification reactor 7, a CO2 / O2 mixture is introduced, and biochar is added to change the composition of the gasified gas. At this time, the following reaction occurs in gasification reactor 7:

[0050] C + O₂ → CO₂ R₁

[0051]

[0052] C + CO₂ → 2CO R₃

[0053] C+H2→CH4 R4

[0054]

[0055] C + H₂O → CO + H₂ R₇

[0056] CO + H₂O → CO₂ + H₂ (R₈)

[0057] Biomass gasification is a complex system. The addition of biochar, O2, and CO2 makes R1, R2, and R3 the main reactions in the above process. R1 and R2 are the complete and incomplete combustion reactions of the biochar, respectively, with high reaction rates and are the main reactions consuming the biochar. Both R1 and R2 are exothermic reactions, providing heat for other reactions in the gasification reactor 7. R3 is the CO2 reduction reaction, a reversible reaction with a lower reaction rate compared to the other two. The reaction rate of R3 is:

[0058]

[0059] In the formula, The rate constant of the reduction reaction is... The surface concentration of CO2;

[0060] As can be seen from the above formula, CO2, acting as a gasifying agent, increases the CO2 concentration, causing the R3 reaction to proceed more vigorously to the right. Since the R3 reaction is a typical endothermic reaction, it lowers the temperature of the gasification reactor, thus reducing the reactivity and rate of the reaction between the solid and gas phases, i.e., reducing the reaction rates of R1 and R2, and consequently decreasing the biochar consumption rate. Simultaneously, the O2 concentration also affects the reaction rates of R1 and R2. Therefore, the gas-solid products can be controlled by jointly regulating the CO2 and O2 content in the gasifying agent. Furthermore, the rightward shift of the R3 reaction reduces net CO2 emissions and increases CO content, thus providing a carbon source while achieving CO2 fixation. Additionally, the temperature of the gasified gas exiting gasification reactor 7 remains between 700 and 800°C. Therefore, a heat exchanger is installed to exchange heat between the gasified gas and O2. The resulting O2 is then introduced into gasification reactor 7 as a gasifying agent. This prevents the temperature of gasification reactor 7 from being too low, which would reduce gasification efficiency and the calorific value of the gasified gas. Meanwhile, a CO2 separation device is installed after heat exchanger 8 to separate CO2 from the gasification gas, thereby changing the main components of the gasification gas into CO, H2, and CH4, which can be used directly. The separated CO2 can be used to provide a CO2 atmosphere for pyrolysis reactor 3 and a CO2 gasification agent for gasification reactor 7.

[0061] The temperature inside gasification reactor 7 is 800–900℃; the molar ratio of gasifying agent to biochar inside gasification reactor 7 is 0.3–1.1, and the molar ratio of CO2 to O2 in the gasifying agent is 0–2.7; the final char yield is 10%–30%; the final char yield, the molar ratio of gasifying agent to biochar, and the molar ratio of CO2 to O2 in the gasifying agent satisfy the following formula:

[0062]

[0063] In the formula, w is the final carbon yield, y is the molar ratio of gasifying agent to biochar, and z is the molar ratio of CO2 to O2 in the gasifying agent.

[0064] The system operation process of the present invention will be further explained and illustrated below with a specific embodiment:

[0065] Biomass silo 1 feeds biomass feedstock into gasifier 2 and pyrolysis reactor 3 for reaction. The ratio of biomass feedstock in gasifier 2 to pyrolysis reactor 3 is controlled at 1:3 via a return valve. Gasifier 2 sequentially completes drying, pyrolysis, oxidation, and reduction reactions from top to bottom, yielding char and gasified gas as the final products after the reduction reaction. O2 is introduced into the oxidation section of gasifier 2, causing a vigorous oxidation reaction that provides heat for the drying, pyrolysis, and reduction sections. Furthermore, the char yield of gasifier 2 is approximately 18%, and the tar content in the gasified gas is 20 g / m³. 3 Subsequently, the charcoal in gasifier 2 directly enters the burner for combustion to provide the heat required for the high-temperature pyrolysis reaction, while the discharged medium-temperature gasified gas enters pyrolysis reactor 3 to provide heat for the pyrolysis reaction. Because the gasified gas from gasifier 2 exits directly from the bottom after leaving the reduction section, its temperature is approximately 600–700°C. The rate at which the gasified gas enters pyrolysis reactor 3 is controlled by a valve, thereby controlling the temperature of pyrolysis reactor 3 to approximately 400–500°C. For pyrolysis reactor 3, the favorable temperature conditions result in a char yield of approximately 40%, and at this point, the tar concentration in the gasified gas is relatively high at 100 g / m³. 3 Subsequently, the gasified gas from gasifier 2 and pyrolysis reactor 3 are jointly fed into high-temperature pyrolysis reactor 6, while the high-quality biochar produced by pyrolysis reactor 3 is transported to biochar bin 4. The high-temperature gas provided by the combustion reaction in burner 5 maintains the temperature of high-temperature pyrolysis reactor 6 at approximately 1100–1300°C, thereby achieving tar removal from the gasified gas. At this point, the tar concentration after the high-temperature pyrolysis reaction is approximately 20 mg / m³. 3Approximately 30% of the biomass char enters the biochar bin, while the yield of the integrated gasified gas is approximately 70%. Subsequently, the integrated gasified gas is fed into the gasification reactor 7, where it mixes with the biomass char provided by the biomass char bin 4, and CO2 and O2 provided by the CO2 separator 9 and heat exchanger 8 respectively, achieving a component transformation of the gasified gas. The gas-solid product is regulated by controlling the ratio of CO2 to O2. When the molar ratio of O2 to biomass char is controlled at 1:4 and the molar ratio of CO2 to O2 is 1:1, the final biomass char yield exiting the gasification reactor is 24%, and the final product gasified gas to biomass char yield ratio is approximately 3:1.

[0066] The above description is merely an embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention, or equivalent structural or procedural transformations made using the content of the present invention's specification and drawings, or direct or indirect applications in other related technical fields, should all be covered within the scope of protection of the present invention.

Claims

1. A cogeneration system using carbon dioxide and oxygen as gasifying agents, characterized in that, It includes a biomass silo (1), a gasifier (2), a pyrolysis reactor (3), a biomass char silo (4), a burner (5), a high-temperature pyrolysis reactor (6), a gasification reactor (7), a heat exchanger (8), and a CO2 separation device (9); The biomass silo (1) is connected to the raw material inlets of the gasifier (2) and the pyrolysis reactor (3) respectively. The gasification gas outlet of the gasifier (2) is connected to the gasification gas inlet of the pyrolysis reactor (3). The carbon outlet (23) of the gasifier (2) is connected to the carbon inlet (51) of the burner (5). The gasifier (2) is connected to an O2 inlet pipe. The biomass carbon outlet (34) of the pyrolysis reactor (3) is connected to the first biomass carbon inlet (41) of the biomass carbon silo (4). The gasification gas outlet of the pyrolysis reactor (3) is connected to the first gasification gas inlet (61) of the high-temperature pyrolysis reactor (6). The biomass carbon outlet of the biomass carbon silo (4) is connected to the biomass carbon inlet (72) of the gasifier (7). The gasification gas outlet of the burner (5) is connected to the second gasification gas inlet of the high-temperature pyrolysis reactor (6). (62) Connection: The burner (5) is connected to an O2 inlet pipe; the gasification gas outlet of the high-temperature pyrolysis reactor (6) is connected to the gasification gas inlet of the gasification reactor (7); the gasification gas outlet of the gasification reactor (7) is connected to the gasification gas inlet of the heat exchanger (8); the O2 outlet (83) of the heat exchanger (8) is connected to the O2 inlet of the gasification reactor (7), the gasification gas outlet of the heat exchanger (8) is connected to the gasification gas inlet of the CO2 separation device (9), and the heat exchanger (8) is connected to an O2 inlet pipe; the first CO2 outlet (92) of the CO2 separation device (9) is connected to the CO2 inlet of the gasification reactor (7), and the second CO2 outlet (93) of the CO2 separation device (9) is connected to the CO2 inlet of the pyrolysis reactor (3); the CO2 separation device (9) is connected to a gasification gas discharge pipe.

2. The carbon dioxide and oxygen cogeneration system according to claim 1, characterized in that, A return valve is provided on the pipeline between the biomass silo (1) and the raw material inlet of the gasifier (2) and the pyrolysis reactor (3); a return valve is provided on the pipeline between the biomass char outlet of the biomass char silo (4) and the biomass char inlet (72) of the gasifier (7); a gasification gas inlet regulating valve is provided on the pipeline between the gasification gas outlet of the gasifier (2) and the gasification gas inlet of the pyrolysis reactor (3); an O2 inlet regulating valve is provided on the pipeline between the O2 outlet (83) of the heat exchanger (8) and the O2 inlet of the gasifier (7); and a CO2 gas regulating valve is provided on the pipeline between the first CO2 outlet (92) of the CO2 separation device (9) and the CO2 inlet of the gasifier (7).

3. The cogeneration system using carbon dioxide and oxygen as gasifying agents according to claim 1, characterized in that, The high-temperature pyrolysis reactor (6) includes a first chamber and a second chamber, which are separated by a partition. The first chamber is provided with a high-temperature resistant ring pipe. The inner inlet of the high-temperature resistant ring pipe is connected to the first gasification gas inlet (61), and the outer inlet of the high-temperature resistant ring pipe is connected to the second gasification gas inlet (62). The inner outlet and the outer outlet of the high-temperature resistant ring pipe are both connected to the second chamber. The gasification gas outlet of the high-temperature pyrolysis reactor (6) is located on the second chamber.

4. The cogeneration system using carbon dioxide and oxygen as gasifying agents according to claim 3, characterized in that, The inner tube of the high-temperature resistant ring pipe is made of aluminum alloy, and the outer tube is made of stainless steel; the dimensions of the inner tube satisfy the following formula: In the formula, D i δ is the diameter of the inner tube, m; L is the length of the high-temperature resistant ring tube, m; δ is the wall thickness of the inner tube, m; the ratio of the gasification gas mass flow rate of the burner (5) to the mass flow rate of the pyrolysis reactor (3) is 3:

1.

5. The cogeneration system using carbon dioxide and oxygen as gasifying agents according to claim 1, characterized in that, The reaction temperature of the high-temperature pyrolysis reactor (6) is 1100-1300℃.

6. The cogeneration system using carbon dioxide and oxygen as gasifying agents according to claim 1, characterized in that, The heat exchanger (8) is a shell-and-tube heat exchanger, with gasified gas in the tube side and O2 in the shell side.

7. The cogeneration system using carbon dioxide and oxygen as gasifying agents according to claim 1, characterized in that, The oxygen concentration inside the burner (5) is >70%.

8. The cogeneration system using carbon dioxide and oxygen as gasifying agents according to claim 1, characterized in that, The CO2 separation device (9) is a membrane separation type.

9. The operating method of the cogeneration system using carbon dioxide and oxygen as gasifying agents according to any one of claims 1 to 8, characterized in that, include: Biomass feedstock from biomass silo (1) enters gasifier (2) and pyrolysis reactor (3) respectively. In gasifier (2), biomass feedstock undergoes gasification reaction with O2 as gasification agent to produce char and gasification gas. Biomass feedstock undergoes pyrolysis in a CO2 atmosphere within the pyrolysis reactor (3); char produced by the gasifier (2) enters the burner (5) for combustion, and the resulting high-temperature gas enters the high-temperature pyrolysis reactor (6) to provide heat for the high-temperature pyrolysis reactor (6); char produced by the pyrolysis reactor (3) enters the biomass char bin (4) and then enters the gasification reactor (7) for the gasification reduction stage; gasified gas produced by the gasifier (2) enters the pyrolysis reactor (3) to provide heat for the pyrolysis section; gasified gas produced by the pyrolysis reactor (3) enters... The high-temperature cracking reactor (6) performs high-temperature cracking catalysis of tar; the gas produced by the high-temperature cracking reactor (6) enters the gasification reactor (7) for gasification reduction, and the amount of system products is regulated by controlling the amount of CO2 and O2; the gas produced by the gasification reactor (7) enters the heat exchanger (8) to exchange heat with O2, and the heated O2 enters the gasification reactor (7) as a gasification agent; the cooled gas enters the CO2 separation device (9), and the separated CO2 enters the pyrolysis reactor (3) and the gasification reactor (7) respectively.

10. The operating method of the carbon dioxide and oxygen cogeneration system according to claim 9, characterized in that, The temperature inside the gasification reactor (7) is 800–900℃; the molar ratio of the gasifying agent to biochar inside the gasification reactor (7) is 0.3–1.1, and the molar ratio of CO2 to O2 in the gasifying agent is 0–2.7; the final char yield is 10%–30%; the final char yield, the molar ratio of the gasifying agent to biochar, and the molar ratio of CO2 to O2 in the gasifying agent satisfy the following formula: In the formula, w is the final carbon yield, y is the molar ratio of gasifying agent to biochar, and z is the molar ratio of CO2 to O2 in the gasifying agent.

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