System and method for hydrothermal catalytic production of methane from biomass

Abstract

The present application provides a kind of biomass hydrothermal catalytic system and method for preparing methane, biomass slurry is preheated in slurry preheater into fixed bed catalytic reactor, the water of water tank is heated with the product of fixed bed catalytic reactor after being pressurized, the energy of product is recovered and further heated into fixed bed catalytic reactor, biomass slurry and high temperature and high pressure water react in fixed bed catalytic reactor to generate methane and carbon dioxide, the product is heated and water-cooled, then gas-liquid separation is carried out, the separated high-pressure gas is separated to obtain methane and carbon dioxide in separation and purification device, and the separated liquid is treated by acidic water stripping tower and returned to water tank, to realize circulation.The present application maximizes the recovery of heat energy while using biomass to prepare methane through reasonable system design, prepares high temperature and high pressure steam that can be directly used, and separates and enriches methane and CO2, to realize the scale application of biomass hydrothermal catalytic methane preparation technology.

Description

Technical Field

[0001] This invention belongs to the field of biomass hydrothermal technology, specifically relating to a system and method for biomass hydrothermal catalytic production of methane. Background Technology

[0002] Hydrothermal catalytic biomass-to-methane conversion is an emerging biomass conversion technology. Utilizing the unique physicochemical properties of high-temperature, high-pressure water, and with the aid of a catalyst, it converts carbon, hydrogen, and oxygen in biomass into CH4 and CO2, simultaneously producing methane and enriching CO2. Compared to traditional biomass thermochemical conversion processes, this technology features lower reaction temperatures, greater material adaptability, no need for energy-intensive drying steps, net-zero CO2 emissions during production, and completely harmless byproducts, resulting in significant economic and ecological benefits.

[0003] Although biomass hydrothermal catalytic methane production technology has achieved satisfactory results in the laboratory, most experiments have used batch reactors or small continuous reactors, which cannot continuously produce methane on a large scale, and the systems cannot operate for extended periods, resulting in low energy utilization. How to rationally design a system to efficiently, cleanly, and in large quantities produce methane while maximizing energy utilization, how to separate and enrich methane and CO2, and how to construct a reaction system capable of continuous production and large-scale industrial application remain pressing problems to be solved. Summary of the Invention

[0004] The purpose of this invention is to overcome the above-mentioned problems and provide a system and method for biomass hydrothermal catalytic methane production. Through reasonable system design, while utilizing biomass to produce methane, heat energy is maximized for recovery, and methane and CO2 are separated and enriched, thereby realizing the large-scale application of biomass hydrothermal catalytic methane production technology.

[0005] This invention is achieved through the following technical solution: A system for biomass hydrothermal catalytic production of methane includes a biomass storage silo, a high-pressure slurry pump, a slurry preheater, a fixed-bed catalytic reactor, an auxiliary heater, a regenerator, a water cooler, a back pressure valve, a gas-liquid separator, a separation and purification device, an acidic water stripping tower, a water tank, and a high-pressure water supply pump. The biomass storage silo is connected to the inlet of the high-pressure slurry pump, the outlet of the high-pressure slurry pump is connected to the cold side inlet of the slurry preheater, and the cold side outlet of the slurry preheater is connected to the inlet of the fixed-bed catalytic reactor. The outlet of the fixed-bed catalytic reactor is connected to the hot-side inlet of the regenerator, the hot-side outlet of the regenerator is connected to the inlet of the water cooler, and the outlet of the water cooler is connected to the inlet of the gas-liquid separator via a back pressure valve. The gas outlet of the gas-liquid separator is connected to the inlet of the separation and purification device, the liquid outlet of the gas-liquid separator is connected to the inlet of the acidic water stripper, and the liquid outlet of the acidic water stripper is connected to the inlet of the water tank. The water tank is connected to the cold-side inlet of the regenerator via a high-pressure water pump, and the cold-side outlet of the regenerator is connected to the inlet of the fixed-bed catalytic reactor via an auxiliary heater. The separation and purification device is used to separate methane and carbon dioxide.

[0006] Preferably, it also includes a steam generator, a water tank connected to the water pump inlet; the water pump outlet connected to the cold side inlet of the steam generator, the cold side outlet of the regenerator being divided into two branches, one branch connected to the fixed bed catalytic reactor inlet via an auxiliary heater, and the other branch connected to the hot side inlet of the steam generator, the hot side outlet of the steam generator connected to the hot side inlet of the slurry preheater, and the hot side outlet of the slurry preheater connected to the water cooler inlet via a flow regulating valve.

[0007] Furthermore, the water pump outlet is divided into two branches: one branch connects to the cold side inlet of the steam generator, and the other branch connects to the auxiliary heater and outputs steam.

[0008] Preferably, the auxiliary heater is a gas-fired boiler, and the fuel for the gas-fired boiler is methane separated by the separation and purification device.

[0009] Preferably, the water pump is a deaerator water pump.

[0010] A method for biomass hydrothermal catalytic methane production, based on the aforementioned system, involves storing biomass slurry in a biomass storage silo. The biomass slurry is pressurized by a high-pressure slurry pump and then enters a slurry preheater for further heating before entering a fixed-bed catalytic reactor. Water in a water tank is pressurized by a high-pressure water supply pump and then enters a regenerator for further heating before entering the fixed-bed catalytic reactor. The biomass slurry and high-temperature, high-pressure water are mixed in the fixed-bed catalytic reactor and react under the action of a catalyst to produce methane and CO2. The product from the fixed-bed catalytic reactor is cooled by a water cooler after heat recovery in the regenerator. After cooling, it enters a gas-liquid separator via a back-pressure valve for gas-liquid separation. The separated gas enters a separation and purification unit for the separation of methane and carbon dioxide. The separated liquid is removed from dissolved carbon dioxide by an acidic water stripping tower before entering a water tank.

[0011] A method for biomass hydrothermal catalytic methane production, based on the aforementioned system, involves storing biomass slurry in a biomass storage silo. The biomass slurry is pressurized by a high-pressure slurry pump and then enters the cold side of a slurry preheater for further heating before entering a fixed-bed catalytic reactor. Water from a water tank is pressurized by a high-pressure water supply pump and enters the cold side of a regenerator, then splits into two branches. Water from one branch is heated by an auxiliary heater and enters the fixed-bed catalytic reactor, while water from the other branch is heated by a steam generator before entering the slurry preheater to preheat the biomass slurry. The biomass slurry is then heated by a high-pressure water supply pump and then enters the fixed-bed catalytic reactor. High-pressure water is mixed in a fixed-bed catalytic reactor and reacts with a catalyst to produce methane and CO2. The products from the fixed-bed catalytic reactor are cooled by a water cooler after heat recovery by a regenerator. After cooling, they enter a gas-liquid separator through a back pressure valve for gas-liquid separation. The separated gas enters a separation and purification unit to separate methane and carbon dioxide. The separated liquid is removed from dissolved carbon dioxide by an acidic water stripper and then enters a water tank. The water in the tank is pumped into the cold side inlet of a steam generator, where it exchanges heat and outputs steam.

[0012] Preferably, the water after being pumped is divided into two branches. One branch enters the cold side inlet of the steam generator, and outputs steam after heat exchange in the steam generator. The water in the other branch is heated in the auxiliary heater and outputs steam. The auxiliary heater uses methane separated by the separation and purification unit as fuel.

[0013] Preferably, the water in the water tank is demineralized water.

[0014] Preferably, the temperature of the biomass slurry entering the fixed-bed catalytic reactor is 130~200℃ and the pressure is 20~25MPa, and the temperature of the water entering the fixed-bed catalytic reactor is 370~450℃ and the pressure is 20~25MPa.

[0015] Compared with the prior art, the present invention has the following beneficial effects: The present invention relates to a biomass hydrothermal catalytic methane production system. Biomass slurry is preheated in a slurry preheater before entering a fixed-bed catalytic reactor. Water in a tank is pressurized and exchanges heat with the products in the fixed-bed catalytic reactor. After recovering the energy from the products, the water is further heated before entering the fixed-bed catalytic reactor. The biomass slurry reacts with high-temperature, high-pressure water in the fixed-bed catalytic reactor to produce methane and carbon dioxide. After heat exchange and water cooling, the products undergo gas-liquid separation. The separated high-pressure gas is further separated into methane and carbon dioxide in a separation and purification unit. The separated liquid is treated by an acidic water stripper and returned to the tank, achieving a cycle. This invention effectively recovers the waste heat from the products in the fixed-bed catalytic reactor through the slurry preheater and regenerator. The slurry preheater and regenerator preheat the biomass slurry and water participating in the reaction, which is beneficial to the reaction. This invention utilizes the unique physicochemical properties of high-temperature, high-pressure water to efficiently convert carbon, hydrogen, and oxygen elements in biomass into methane and CO2. Therefore, it eliminates the need for energy-intensive drying processes for biomass feedstocks with high moisture content, significantly reducing energy consumption in the methane production process. The gas exiting the gas-liquid separator is high-pressure CH4 and CO2, and the gas pressure entering the separation and purification unit can be adjusted as needed, eliminating the need for gas pressurization during separation and purification, thus saving energy. This invention's system can operate continuously for extended periods, overcoming the limitations of previous technologies in continuous methane production. It is suitable for large-scale, industrial applications, enabling large-scale production of CH4 and CO2, achieving natural CO2 enrichment, and features a compact design, small footprint, and low investment.

[0016] Furthermore, the system of the present invention is also equipped with a steam generator. The cold side outlet of the regenerator has two branches, which are respectively connected to the auxiliary heater and the hot side inlet of the steam generator. This arrangement allows for flexible adjustment of the flow rate through the branches, ensuring that the cold side flow rate of the regenerator and the slurry preheater is equal to the hot side flow rate, which is beneficial for heat recovery and utilization. At the same time, it can produce high-temperature and high-pressure steam as a byproduct. The high-temperature and high-pressure steam produced can be used directly or sold to create economic benefits.

[0017] Furthermore, a portion of the water in the tank is pumped into the auxiliary heater to generate high-temperature, high-pressure steam, which can be produced as a byproduct of methane production. At the same time, when the auxiliary heater uses the methane produced by the system of this invention as fuel, resource reuse can be achieved. By adjusting the amount of pressurized steam generated and the amount of methane burned, the final product of the system can be flexibly adjusted to achieve applications in different directions.

[0018] Furthermore, the water pump is a deaerator pump, which removes oxygen from the water, thus avoiding the influence of oxygen on high-temperature and high-pressure steam. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of a biomass hydrothermal catalytic methane production system according to the present invention.

[0020] The labels in the diagram have the following meanings: 1-Biomass storage silo; 2-High-pressure slurry pump; 3-Slurry preheater; 4-Fixed bed catalytic reactor; 5-Auxiliary heater; 6-Steam generator; 7-Regenerator; 8-Water cooler; 9-Back pressure valve; 10-Gas-liquid separator; 11-Separation and purification device; 12-Acidic water stripping tower; 13-Water tank; 14-High-pressure water supply pump; 15-Water pump; 16-Flow regulating valve. Detailed Implementation

[0021] To further understand the present invention, the present invention will be described below with reference to embodiments. These descriptions are only for further explaining the features and advantages of the present invention and are not intended to limit the claims of the present invention.

[0022] See attached document Figure 1 This invention relates to a system for biomass hydrothermal catalytic methane production, comprising a biomass storage silo 1, a high-pressure slurry pump 2, a slurry preheater 3, a fixed-bed catalytic reactor 4, an auxiliary heater 5, a steam generator 6, a regenerator 7, a water cooler 8, a back pressure valve 9, a gas-liquid separator 10, a separation and purification device 11, an acidic water stripping tower 12, a water tank 13, a high-pressure water supply pump 14, a water pump 15, and a flow regulating valve 16. The biomass storage silo 1 is connected to the inlet of the high-pressure slurry pump 2; the outlet of the high-pressure slurry pump 2 is connected to the cold-side inlet of the slurry preheater 3; the cold-side outlet of the slurry preheater 3 is connected to the inlet of the fixed-bed catalytic reactor 4; the hot-side inlet of the slurry preheater 3 is connected to the hot-side outlet of the steam generator 6; and the hot-side outlet of the slurry preheater 3 is connected to the inlet of the water cooler 8 via the flow regulating valve 16. The fixed-bed catalytic reactor 4... The inlet is also connected to the auxiliary heater 5. The outlet of the fixed-bed catalytic reactor 4 is connected to the hot-side inlet of the regenerator 7. The hot-side outlet of the regenerator 7 is connected to the inlet of the water cooler 8. The cold-side outlet of the regenerator 7 is divided into two branches, which are connected to the auxiliary heater 5 and the hot-side inlet of the steam generator 6, respectively. The cold-side inlet of the regenerator 7 is connected to the high-pressure water supply pump 14. The outlet of the water cooler 8 is connected to the inlet of the gas-liquid separator 10 via the back pressure valve 9. The gas outlet of the gas-liquid separator 10 is connected to the separation and purification device 11. The liquid outlet of the gas-liquid separator 10 is connected to the acidic water stripper 12. The acidic water stripper 12 is connected to the water tank 13. The water tank 13 is connected to the inlet of the high-pressure water supply pump 14. The water tank 13 is also connected to the inlet of the water pump 15. The outlet of the water pump 15 is divided into two branches, which are connected to the cold-side inlet of the steam generator 6 and the auxiliary heater 5, respectively.

[0023] The auxiliary heater 5 can be selected from various forms such as electric heater, gas boiler or coal boiler. While heating water to provide heat for the reaction, the auxiliary heater 5 also produces high-temperature and high-pressure steam that can be directly used, thereby improving energy utilization efficiency.

[0024] When the auxiliary heater 5 is a gas-fired boiler, its fuel is methane separated by the separation and purification device 11.

[0025] The water pump 15 described in this invention is a deoxygenating water pump, which can remove oxygen from the water to prevent oxygen from affecting the generation of steam. The water tank 13 contains demineralized water.

[0026] The fixed-bed catalytic reactor 4 of this invention is a container that can withstand pressure of 22~30MPa and temperature of 300~500℃. It is filled with a catalyst and, combined with the unique physicochemical properties of high-temperature and high-pressure water, can efficiently convert carbon, hydrogen, and oxygen elements in biomass into CH4 and CO2. The methanation reaction is carried out only in the fixed-bed catalytic reactor 4. It can be manufactured using commonly used pressure vessel steels such as 13MnNiMoR.

[0027] This invention discloses a system for biomass hydrothermal catalytic methane production, applicable to, but not limited to, various materials such as straw, corn cobs, industrial organic wastewater, municipal waste, livestock and poultry waste, and aquatic waste. It can continuously produce CH4 on a large scale while achieving natural enrichment of CO2, and by producing high-temperature and high-pressure steam as a byproduct.

[0028] Its typical working process is as follows: The biomass slurry is stored in the biomass storage silo 1. The biomass slurry is first pressurized to 23 MPa by the high-pressure slurry pump 2, and then enters the slurry preheater 3 to be heated to 130~200℃ (preferably 150℃). It then enters the fixed-bed catalytic reactor 4. The demineralized water is supplied by the water tank 13. It is first pressurized to 23 MPa by the high-pressure water supply pump 14, and then enters the cold side of the regenerator 7 to be heated to 330℃. Then, part of the demineralized water enters the hot side of the steam generator 6, and part enters the auxiliary heater 5 to be heated to 400℃, and then enters the fixed-bed catalytic reactor 4.

[0029] The demineralized water provided by water tank 13 is partially deoxygenated by water pump 15 and then enters the cold side of steam generator 6 to generate high-temperature and high-pressure steam at 197°C and 0.9 MPa. Another portion is deoxygenated by water pump 15 and then enters the auxiliary heater 5 to generate high-temperature and high-pressure steam at 197°C and 0.9 MPa. This high-temperature and high-pressure steam can be used directly or sold to generate economic benefits. A further portion of the demineralized water is pressurized by a high-pressure water supply pump and then enters the cold side of regenerator 7 to be heated to 330°C, fully recovering the waste heat from the products of the fixed-bed catalytic reactor. Further, the demineralized water heated by regenerator 7 is divided into two parts: one part is heated by auxiliary heater 5 and then enters the fixed-bed catalytic reactor 4 to participate in the reaction; the other part enters the hot side of steam generator 6 and is cooled to 170°C, then enters the hot side of slurry preheater 3 and is cooled to 50°C, then enters the water cooler 8 through flow regulating valve 16, where it mixes with the products of the fixed-bed catalytic reactor 4 and is cooled to 40°C. The regenerator 7, steam generator 6 and slurry preheater 3 can all be shell-and-tube heat exchangers, which can be manufactured using steel such as Q345. Sufficient corrosion allowance should be left at the heat exchange tubes.

[0030] The fixed-bed catalytic reactor 4 is designed to operate at a pressure of 23 MPa and a temperature of 400 °C. The suitable feedstock is biomass slurry, and the suitable catalyst is solid granules. Biomass slurry at 150 °C and demineralized water at 400 °C enter the bottom of the fixed-bed catalytic reactor 4. Under the action of the catalyst, a series of reactions occur, converting C, H, and O elements in small organic molecules into CH4 and CO2. Inorganic salts formed from mineral elements in the biomass slurry are enriched as solid slag at the bottom of the fixed-bed catalytic reactor 4 and periodically discharged. The products in the fixed-bed catalytic reactor (including a mixture of high-temperature, high-pressure water, methane, and CO2) are cooled to 50 °C after the waste heat is fully recovered by the regenerator 7, and then cooled to 40 °C by the water cooler 8 via a flow regulating valve.

[0031] After being cooled by the water cooler 8, the fluid passes through the back pressure valve 9 and then enters the gas-liquid separator 10. The gas phase enters the separation and purification device 11 to obtain methane and CO2 products, while the liquid water is treated by the acidic water stripping tower 12 and then returned to the water tank 13.

[0032] Through the above specific embodiments, the original intention, technical solution, implementation process, and scientific value of the present invention have been further clarified. It should be particularly emphasized that these embodiments are merely illustrative examples of the present invention and are not intended to limit the invention. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A system for biomass hydrothermal catalytic production of methane, characterized in that, It includes a biomass storage silo (1), a high-pressure slurry pump (2), a slurry preheater (3), a fixed-bed catalytic reactor (4), an auxiliary heater (5), a regenerator (7), a water cooler (8), a back pressure valve (9), a gas-liquid separator (10), a separation and purification device (11), an acidic water stripping tower (12), a water tank (13), and a high-pressure water supply pump (14). The biomass storage silo (1) is connected to the inlet of the high-pressure slurry pump (2), the outlet of the high-pressure slurry pump (2) is connected to the cold side inlet of the slurry preheater (3), and the cold side outlet of the slurry preheater (3) is connected to the inlet of the fixed bed catalytic reactor (4). The outlet of the fixed-bed catalytic reactor (4) is connected to the hot-side inlet of the regenerator (7), the hot-side outlet of the regenerator (7) is connected to the inlet of the water cooler (8), and the outlet of the water cooler (8) is connected to the inlet of the gas-liquid separator (10) via the back pressure valve (9); the gas outlet of the gas-liquid separator (10) is connected to the inlet of the separation and purification device (11), the liquid outlet of the gas-liquid separator (10) is connected to the inlet of the acidic water stripper (12), and the liquid outlet of the acidic water stripper (12) is connected to the inlet of the water tank (13); the water tank (13) is connected to the cold-side inlet of the regenerator (7) via the high-pressure water pump (14), and the cold-side outlet of the regenerator (7) is connected to the inlet of the fixed-bed catalytic reactor (4) via the auxiliary heater (5); the separation and purification device (11) is used to separate methane and carbon dioxide.

2. The system for biomass hydrothermal catalytic methane production according to claim 1, characterized in that, It also includes a steam generator (6), a water tank (13) connected to the inlet of a water pump (15); the outlet of the water pump (15) is connected to the cold side inlet of the steam generator (6), and the cold side outlet of the regenerator (7) is divided into two branches. One branch is connected to the inlet of the fixed bed catalytic reactor (4) via an auxiliary heater (5), and the other branch is connected to the hot side inlet of the steam generator (6). The hot side outlet of the steam generator (6) is connected to the hot side inlet of the slurry preheater (3), and the hot side outlet of the slurry preheater (3) is connected to the inlet of the water cooler (8) via a flow regulating valve (16).

3. The system for biomass hydrothermal catalytic methane production according to claim 2, characterized in that, The outlet of the water pump (15) is divided into two branches. One branch is connected to the cold side inlet of the steam generator (6), and the other branch is connected to the auxiliary heater (5) and outputs steam.

4. The system for biomass hydrothermal catalytic methane production according to claim 1, characterized in that, The auxiliary heater (5) is a gas-fired boiler, and the fuel for the gas-fired boiler is methane separated by the separation and purification device (11).

5. The system for biomass hydrothermal catalytic methane production according to claim 1, characterized in that, The water pump (15) is a deaerator.

6. A method for biomass hydrothermal catalytic production of methane, characterized in that, Based on the system described in claim 1, the biomass slurry is stored in the biomass storage silo (1). After being pressurized by the high-pressure slurry pump (2), the biomass slurry enters the cold side of the slurry preheater (3) for heating, and then enters the fixed bed catalytic reactor (4). The water in the water tank (13) is pressurized by the high-pressure water supply pump (14) and enters the cold side of the regenerator (7). Then, it is heated by the auxiliary heater (5) and enters the fixed bed catalytic reactor (4). The biomass slurry and high-temperature high-pressure water are mixed in the fixed bed catalytic reactor (4) and react under the action of the catalyst to generate methane and CO2. The product of the fixed bed catalytic reactor (4) is cooled by the regenerator after heat recovery and enters the water cooler (8). After cooling, it enters the gas-liquid separator through the back pressure valve (9) for gas-liquid separation. The separated gas enters the separation and purification device for the separation of methane and carbon dioxide. The separated liquid enters the water tank (13) after the dissolved carbon dioxide is removed by the acidic water stripping tower (12).

7. A method for biomass hydrothermal catalytic production of methane, characterized in that, Based on the system described in claim 2, the biomass slurry is stored in a biomass storage silo (1). After being pressurized by a high-pressure slurry pump (2), the biomass slurry enters the cold side of the slurry preheater (3) for heating, and then enters the fixed-bed catalytic reactor (4). The water in the water tank (13) is pressurized by a high-pressure water supply pump (14) and enters the cold side of the regenerator (7), and then splits into two branches. The water in one branch is heated by an auxiliary heater (5) and enters the fixed-bed catalytic reactor (4). The water in the other branch is heated by a steam generator (6) and then enters the slurry preheater (3) to preheat the biomass slurry. The biomass slurry and the high-temperature and high-pressure water are in a fixed bed catalytic reactor (4). In the fixed-bed catalytic reactor (4), the mixture reacts under the action of the catalyst to produce methane and CO2. The product of the fixed-bed catalytic reactor (4) is cooled by a water cooler (8) after the heat is recovered by the regenerator. After cooling, it enters the gas-liquid separator through the back pressure valve (9) for gas-liquid separation. The separated gas enters the separation and purification device (11) for the separation of methane and carbon dioxide. The separated liquid enters the water tank (13) after the dissolved carbon dioxide is removed by the acidic water stripping tower (12). The water in the water tank (13) enters the cold side inlet of the steam generator (6) through the water pump (15). After heat exchange in the steam generator (6), steam is output.

8. The method for biomass hydrothermal catalytic production of methane according to claim 7, characterized in that, Water from the pump (15) is divided into two branches. One branch enters the cold side inlet of the steam generator (6), and steam is output after heat exchange in the steam generator (6). The water from the other branch is heated in the auxiliary heater (5) and then outputs steam. The auxiliary heater (5) uses methane separated by the separation and purification device (11) as fuel.

9. The method for biomass hydrothermal catalytic production of methane according to any one of claims 6 to 8, characterized in that, The water in the water tank (13) is demineralized water.

10. The method for biomass hydrothermal catalytic production of methane according to any one of claims 6 to 8, characterized in that, The temperature of the biomass slurry entering the fixed-bed catalytic reactor (4) is 130~200℃ and the pressure is 20~25MPa. The temperature of the water entering the fixed-bed catalytic reactor (4) is 370~450℃ and the pressure is 20~25MPa.

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