A device and method for producing methane by hydrothermal catalysis of biomass, which can realize solid-state residue enrichment

Abstract

The application provides a biomass hydrothermal catalytic methanation reaction device and method capable of realizing solid-state residue enrichment. The reaction device is provided with inner and outer baffle tubes at the lower part, so that biomass slurry and high-temperature and high-pressure water can be fully mixed, and water-phase reforming reaction occurs under the condition of no catalyst, in which mineral elements from the biomass are converted into inorganic salts. Since the solubility of the inorganic salts in high-temperature and high-pressure (near the critical point) water is extremely low, the inorganic salts are precipitated in the form of solid-state residues and deposited at the bottom of the reaction device under the action of gravity. The scheme can effectively avoid the inorganic salts from entering the pores of the catalyst to affect the catalytic performance, can significantly improve the service life of the catalyst, and is favorable for efficient and stable reaction process.

Description

Technical Field

[0001] This invention belongs to the field of biomass hydrothermal technology and relates to a biomass hydrothermal catalytic reaction device and method for producing methane by enriching solid slag. Background Technology

[0002] Biomass is an important renewable energy source, characterized by low pollution, carbon balance, abundant reserves, and wide distribution. The main methods of biomass utilization include direct combustion power generation, pyrolysis gasification, pyrolysis liquefaction, and anaerobic fermentation. While these technologies have powerfully promoted the diversified development of biomass energy, they generally suffer from low energy efficiency, high emission reduction costs, poor raw material adaptability, and difficulties in large-scale production. Hydrothermal catalytic biomass-to-methane conversion is an emerging biomass conversion technology. It utilizes the unique physicochemical properties of high-temperature, high-pressure water to convert carbon, hydrogen, and oxygen elements in biomass into CH4 and CO2, thereby achieving natural CO2 enrichment while producing methane. Compared with traditional biomass thermochemical conversion processes, this technology has lower reaction temperatures, stronger material adaptability, eliminates the need for energy-intensive drying steps, and achieves net-zero CO2 emissions during the production process, resulting in significant economic and ecological benefits. Currently, the biomass hydrothermal catalytic methane production process mainly uses a fixed-bed catalytic reactor. The mixed fluid of biomass slurry and high-temperature, high-pressure water passes through a fixed bed layer covered with catalyst particles, and a series of complex chemical reactions occur under the action of the catalyst. After the reaction products flow out of the fixed-bed catalytic reactor, they are cooled, depressurized, separated, and purified to finally obtain the target product.

[0003] Although fixed-bed catalytic reactors have achieved satisfactory results in the laboratory, they still face challenges for large-scale industrial application. The composition of real biomass feedstocks is extremely complex, containing not only essential elements for organic matter such as C, H, and O, but also mineral elements such as K, Na, Ca, Mg, Cl, and Br. These mineral elements precipitate as inorganic salts in a hydrothermal environment, forming solid slag deposited inside the fixed-bed catalytic reactor bed. This hinders the contact between the catalyst and the reaction stream, severely impacting the efficiency of biomass conversion. How to avoid the impact of mineral element precipitation from biomass on the catalytic reaction effect has become one of the major challenges restricting the industrial application of biomass hydrothermal catalytic methane production technology. Summary of the Invention

[0004] The purpose of this invention is to overcome the aforementioned problems and provide a biomass hydrothermal catalytic methane production reactor and method that can achieve solid slag enrichment. Through a special structural design, combined with the unique physicochemical properties of high-temperature and high-pressure water, inorganic salts formed from mineral elements in biomass are enriched in the form of solid slag at the bottom of the reactor and periodically discharged, thereby avoiding the impact of mineral element precipitation on the catalytic reaction effect.

[0005] This invention is achieved through the following technical solution:

[0006] A biomass hydrothermal catalytic methane production reactor capable of enriching solid slag includes: a reactor body, a biomass slurry inlet pipe, a high-temperature and high-pressure water inlet pipe, an inner baffle, an outer baffle, and a catalyst support structure.

[0007] The device body has a feed inlet at the bottom, and a biomass slurry inlet pipe and a high-temperature and high-pressure water inlet pipe converge and connect to the feed inlet; the device body has a reaction product outlet at the top.

[0008] The inner baffle is an open structure at the top and bottom, arranged vertically and connected at the bottom to the inner wall of the device body. The inner baffle is connected to the feed inlet at the bottom of the device body. The outer baffle is an open structure at the bottom and sealed at the top. The outer baffle is connected to the inner wall of the device body and covers the inner baffle. There is a gap between the top of the inner baffle and the top inner wall of the outer baffle.

[0009] The catalyst support structure is connected to the inner wall of the device body, and the catalyst support structure is located above the outer baffle.

[0010] Preferably, the device body includes: an upper end cap, a cylinder, and a lower end cap; the upper end cap and the lower end cap are respectively connected to the upper end and the lower end of the cylinder.

[0011] Preferably, the catalyst support structure includes a lower support ceramic disk and an upper support ceramic disk arranged opposite each other, and both the lower support ceramic disk and the upper support ceramic disk have a mesh structure; in use, the catalyst is filled between the lower support ceramic disk and the upper support ceramic disk.

[0012] Furthermore, the lower support ceramic plate and the upper support ceramic plate are connected to the inner wall of the device body via movable hooks.

[0013] Preferably, the outer baffle tube is connected to the inner wall of the device body by a fixed bracket.

[0014] Preferably, the inner and outer baffles are arranged coaxially with the device body.

[0015] Preferably, the lower end of the device body is connected to a slag discharge port.

[0016] Furthermore, the lower end of the device body is connected to the slag discharge port through a slag discharge pipe, and a discharge valve is installed on the slag discharge pipe.

[0017] Furthermore, a slag cooler is installed on the slag discharge pipe, and the slag cooler is located between the discharge valve and the slag discharge port.

[0018] A biomass hydrothermal catalytic methane production method with solid slag enrichment is disclosed. Based on the aforementioned apparatus, biomass slurry and water enter the bottom of the apparatus body from the biomass slurry inlet pipe and the high-temperature, high-pressure water inlet pipe, respectively, forming a mixed fluid of biomass slurry and water. This mixed fluid flows upward along the inner baffle tube, then downwards after encountering the outer baffle tube, and reaches the bottom of the apparatus body along the annular space between the inner and outer baffle tubes. During the flow, the mixed fluid undergoes an aqueous reforming reaction, and the mineral elements in the biomass slurry precipitate out as inorganic salts, which are deposited at the bottom of the apparatus body under gravity to form solid slag. The mixed fluid then flows upward into the catalyst to carry out a methanation reaction, and the generated gaseous products are discharged from the reaction product outlet.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] The reaction apparatus of this invention incorporates inner and outer baffles in its lower part, allowing for thorough mixing of biomass slurry and high-temperature, high-pressure water. This enables an aqueous reforming reaction to occur without a catalyst, during which mineral elements from the biomass are converted into inorganic salts. Because inorganic salts have extremely low solubility in high-temperature, high-pressure water (near the critical point), they precipitate as solid slag and deposit at the bottom of the reaction apparatus under gravity. This design effectively prevents inorganic salts from entering the catalyst pores and affecting catalytic performance, significantly improving catalyst lifespan and promoting efficient and stable reaction processes.

[0021] Furthermore, the bottom of the reaction device is equipped with a slag discharge port, which can be adjusted by opening and closing the discharge valve to achieve periodic discharge and enrichment and recovery of solid slag, ensuring continuous, efficient and stable operation of the reaction device.

[0022] Furthermore, the downstream slag cooler of the discharge valve can cool the discharged high-temperature slag-water mixture to ensure discharge safety, and can also recover and utilize this heat, thereby improving the overall energy efficiency of the biomass hydrothermal catalytic methane production system. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the biomass hydrothermal catalytic methane production reactor that enables the enrichment of solid slag according to the present invention.

[0024] Figure 2 This is a schematic diagram of the fixed installation of the inner and outer baffles of the present invention.

[0025] The labels in the diagram have the following meanings: 1-Upper head; 2-Cylinder body; 3-Lower head; 4-Biomass slurry inlet pipe; 5-High temperature and high pressure water inlet pipe; 6-Drain valve; 7-Cold slag cooler; 8-Slag discharge port; 9-Inner baffle; 10-Outer baffle; 11-Lower support ceramic disc; 12-Catalyst; 13-Upper support ceramic disc; 14-Reaction product outlet; 15-Fixed bracket. Detailed Implementation

[0026] 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.

[0027] See attached document Figure 1 The present invention provides a biomass hydrothermal catalytic methane production reactor capable of enriching solid slag, comprising: a device body, a biomass slurry inlet pipe 4, a high-temperature and high-pressure water inlet pipe 5, an inner baffle 9, an outer baffle 10, and a catalyst support structure.

[0028] The device body has a feed inlet at its bottom, where biomass slurry inlet pipe 4 and high-temperature, high-pressure water inlet pipe 5 converge and connect. The device body also has a reaction product outlet 14 at its top. A slag discharge port 8 is connected to the lower end of the device body.

[0029] The inner baffle 9 has an open top and bottom structure, is vertically arranged, and its bottom is connected to the inner wall of the bottom of the device body. The inner baffle 9 is connected to the feed inlet at the bottom of the device body. The outer baffle 10 has an open bottom and a sealed top structure. The outer baffle 10 is connected to the inner wall of the device body through a fixed bracket 15. The outer baffle 10 covers the inner baffle 9, and there is a gap between the top of the inner baffle 9 and the top inner wall of the outer baffle 10.

[0030] The catalyst support structure is connected to the inner wall of the device body, and the catalyst support structure is located above the outer baffle 10.

[0031] Example

[0032] See attached document Figure 1 In a specific embodiment of the present invention, the device body includes: an upper end cap 1, a cylindrical body 2, and a lower end cap 3; the upper end cap 1 and the lower end cap 3 are respectively connected and fixed to the upper and lower ends of the cylindrical body 2 by welding. The upper and lower end caps and the cylindrical body are all made of high-temperature resistant alloy steel, and their wall thickness is required to allow for a certain corrosion allowance.

[0033] The biomass slurry inlet pipe 4 and the high-temperature, high-pressure water inlet pipe 5 are symmetrically arranged and connected to the feed port at the bottom of the lower head 3 by welding via a vertical connecting pipe. An opening with its axis at a 45° angle to the cylinder axis is located on the lower side of the lower head 3. This opening connects to a slag discharge pipe, which is sequentially equipped with a discharge valve 6, a slag cooler 7, and a slag discharge port 8. The discharge valve is a high-temperature resistant, electrically controlled valve, which has good throughput for small solid particles. The slag cooler is a shell-and-tube heat exchanger made of high-temperature alloy steel. The fluid on the tube side is a mixture of solid slag and high-temperature, high-pressure water, while the fluid on the shell side is external circulating cooling water.

[0034] The catalyst support structure includes a lower support ceramic disc 11 and an upper support ceramic disc 13. The lower and upper support ceramic discs 11 and 13 are mounted on the upper inner wall of the cylinder 2 via movable hooks. The catalyst 12 is tightly packed between the two support ceramic discs and cannot pass through the mesh structure. The reaction product outlet 14 is connected and fixed to the top of the upper head 1 by welding via a vertical connecting pipe. The upper and lower support ceramic discs are made of high-temperature resistant ceramic material and have a mesh structure.

[0035] The bottom of the inner baffle 9 is connected and fixed to the inner wall of the bottom of the lower head 3 by welding. The inner baffle 9 is coaxial with the vertical connecting pipe at the bottom of the lower head 3.

[0036] See attached document Figure 2 In this invention, the inner baffle 9 and the outer baffle 10 are coaxially installed with the cylinder 2, and the annular area serves as a flow channel for the reactants. The outer baffle 10 is connected to the inner wall of the cylinder 2 by four fixed supports, which are symmetrically distributed along the circumference and at a 90° angle to each other, ensuring that the outer baffle 10 will not deform or shift position due to fluid scouring during the operation of the reaction device. The inner and outer baffles only withstand high temperatures and not high pressures, and are made of high-temperature resistant alloy steel to ensure that they will not deform under the scouring and impact of high-temperature fluids.

[0037] This invention relates to a biomass hydrothermal catalytic methane production reactor that can achieve solid slag enrichment. The design operating pressure is 20-30 MPa, the operating temperature is 350-500℃, the applicable raw material is biomass slurry, and the applicable catalyst is solid granules (the particle size is required to be larger than the mesh size of the upper and lower supporting ceramic discs).

[0038] The typical operating process of the reaction device of the present invention is as follows:

[0039] Biomass slurry at 150℃ and demineralized water at 400℃ are introduced into the biomass slurry inlet 4 and the high-temperature, high-pressure water inlet 5, respectively. After mixing, they enter the bottom of the reactor through a vertical pipe. The mixed fluid flows upward along the inner baffle 9, then downward after encountering the outer baffle 10, and reaches the bottom of the reactor through the annular space between the inner and outer baffles. During this process, the mixed fluid mainly undergoes an aqueous reforming reaction, where the organic macromolecules in the biomass are broken down into smaller molecules, and the mineral elements precipitate out as inorganic salts, which are deposited at the bottom of the reactor under gravity to form solid slag. Subsequently, the high-temperature, high-pressure water that dissolves the small organic molecules flows upward along the annular space between the outer baffle 10 and the cylinder 2, passes through the lower support ceramic disc 11, contacts the catalyst 12, and undergoes a series of methanation reactions, converting the C, H, and O elements in the small organic molecules into CH4 and CO2. Finally, the reaction products continue to flow upward through the upper support ceramic disc 13 and flow out through the reaction product outlet 14. After subsequent cooling, depressurization, and separation and purification, high-purity CH4 and CO2 products can be obtained.

[0040] This invention enables the operation of a biomass hydrothermal catalytic methane production reactor with solid slag enrichment. Slag can be discharged periodically by opening the discharge valve 6 to ensure unobstructed flow in the bottom channel of the reactor. The reactor operates at a constant pressure of 23 MPa. When the discharge valve 6 is open, the deposited solid slag and a small amount of high-temperature, high-pressure water will enter the slag cooler 7 through the discharge valve 6 under the influence of pressure difference. Inside the slag cooler 7, the high-temperature slag-water mixture exchanges heat with external circulating cooling water, and the cooled slag-water mixture is discharged through the slag discharge port 8. The frequency of periodic slag discharge depends on the content and composition of mineral elements in the selected biomass raw materials and can be adjusted according to actual conditions. The discharged solid slag and liquid water can be recycled as needed.

[0041] This invention relates to a biomass hydrothermal catalytic methane production reactor that enables the enrichment of solid residue. It is suitable for various biomass feedstocks, including but not limited to straw, corn cobs, rice husks, sawdust, seaweed, and kitchen waste. The biomass feedstocks need to be pre-crushed and stirred into a slurry before entering the reactor for methane production. For biomass feedstocks with high moisture content, there is no need for an energy-intensive drying process, thus significantly reducing the energy consumption of the methane production process.

[0042] 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 biomass hydrothermal catalytic methane production reactor capable of enriching solid slag, characterized in that, include: The device body, biomass slurry inlet pipe (4), high temperature and high pressure water inlet pipe (5), inner baffle (9), outer baffle (10) and catalyst support structure; The device body has a feed inlet at the bottom, and the biomass slurry inlet pipe (4) and the high temperature and high pressure water inlet pipe (5) converge and connect to the feed inlet; the device body has a reaction product outlet (14) at the top. The inner baffle (9) has an open top and bottom structure. The inner baffle (9) is vertically arranged and its bottom is connected to the inner wall of the bottom of the device body. The inner baffle (9) is connected to the feed inlet at the bottom of the device body. The outer baffle (10) has an open bottom and a sealed top structure. The outer baffle (10) is connected to the inner wall of the device body. The outer baffle (10) covers the inner baffle (9), and there is a gap between the top of the inner baffle (9) and the top inner wall of the outer baffle (10). The catalyst support structure is connected to the inner wall of the device body, and the catalyst support structure is located above the outer baffle (10); During use, biomass slurry and water enter the bottom of the device body from the biomass slurry inlet pipe (4) and the high-temperature and high-pressure water inlet pipe (5), respectively, forming a mixed fluid of biomass slurry and water. The fluid flows upward along the inner baffle (9), then flows downward after encountering the outer baffle (10), and reaches the bottom of the device body along the annular space gap between the inner baffle (9) and the outer baffle (10). During the flow, the mixed fluid undergoes an aqueous reforming reaction, and the mineral elements in the biomass slurry precipitate out in the form of inorganic salts and are deposited at the bottom of the device body under the action of gravity to form solid slag.

2. The biomass hydrothermal catalytic methane production reactor capable of solid slag enrichment according to claim 1, characterized in that, The device body includes: an upper end cap (1), a cylinder (2) and a lower end cap (3); the upper end cap (1) and the lower end cap (3) are respectively connected to the upper end and the lower end of the cylinder (2).

3. The biomass hydrothermal catalytic methane production reactor capable of solid slag enrichment according to claim 1, characterized in that, The catalyst support structure includes a lower support ceramic disk (11) and an upper support ceramic disk (13) arranged opposite each other. Both the lower support ceramic disk (11) and the upper support ceramic disk (13) have a mesh structure. When in use, the catalyst (12) is filled between the lower support ceramic disk (11) and the upper support ceramic disk (13).

4. The biomass hydrothermal catalytic methane production reactor capable of solid slag enrichment according to claim 3, characterized in that, The lower support ceramic plate (11) and the upper support ceramic plate (13) are connected to the inner wall of the device body through movable hooks.

5. The biomass hydrothermal catalytic methane production reactor capable of solid slag enrichment according to claim 1, characterized in that, The outer baffle tube (10) is connected to the inner wall of the device body by a fixed bracket (15).

6. The biomass hydrothermal catalytic methane production reactor capable of solid slag enrichment according to claim 1, characterized in that, The inner baffle (9) and outer baffle (10) are arranged coaxially with the main body of the device.

7. The biomass hydrothermal catalytic methane production reactor capable of solid slag enrichment according to claim 1, characterized in that, The lower end of the device body is connected to a slag discharge port (8).

8. The biomass hydrothermal catalytic methane production reactor capable of solid slag enrichment according to claim 7, characterized in that, The lower end of the device body is connected to the slag discharge port (8) through a slag discharge pipe, and a discharge valve (6) is provided on the slag discharge pipe.

9. The biomass hydrothermal catalytic methane production reactor capable of solid slag enrichment according to claim 8, characterized in that, A slag cooler (7) is installed on the slag discharge pipe, and the slag cooler (7) is located between the discharge valve (6) and the slag discharge port (8).

10. A method for biomass hydrothermal catalytic methane production that enables the enrichment of solid slag, characterized in that, Based on the device according to any one of claims 1-9, the working pressure is 20-30 MPa and the working temperature is 350-500 ℃. Biomass slurry and water enter the bottom of the device body from the biomass slurry inlet pipe (4) and the high temperature and high pressure water inlet pipe (5) respectively, forming a mixed fluid of biomass slurry and water. It flows upward along the inner baffle (9), and after encountering the outer baffle (10), it flows downward and reaches the bottom of the device body along the annular space gap between the inner baffle (9) and the outer baffle (10). During the flow process, the mixed fluid undergoes an aqueous reforming reaction. The mineral elements in the biomass slurry precipitate in the form of inorganic salts and are deposited at the bottom of the device body under the action of gravity to form solid slag. The mixed fluid flows upward into the catalyst to carry out the methanation reaction, and the gaseous products produced are discharged from the reaction product outlet.

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