An apparatus and method for the methanation of bidirectional flue gas

Abstract

This invention provides an apparatus and method for bidirectional flue gas methanation, relating to the field of waste gas treatment technology, and solves the technical problem of excessively high mass transfer resistance caused by low hydrogen and CO2 concentrations and large liquid film thickness in existing technologies. The apparatus and method for bidirectional flue gas methanation includes: at least two gas-phase reaction chambers, stacked along their height and interconnected at their contact points; a storage tank, interconnected at its contact point with the bottom gas-phase reaction chamber; a replenishment mechanism for drawing nutrient solution from the storage tank and replenishing it to the at least two gas-phase reaction chambers; and a gas storage mechanism connected to the storage tank and the top gas-phase reaction chamber of the at least two gas-phase reaction chambers, for sequentially filling and discharging gas from the storage tank to each gas-phase reaction chamber, or sequentially filling and discharging gas from the top gas-phase reaction chamber to the lower gas-phase reaction chamber and the storage tank.

Description

Technical Field

[0001] This invention relates to the field of waste gas treatment technology, and in particular to an apparatus and method for the methanation of bidirectional flue gas. Background Technology

[0002] With the increasing demand for global climate change and waste resource recovery, carbon capture and conversion (CCU) technologies have become a hot research topic in emission reduction and resource utilization. Currently, CCU mainly relies on separating pure CO2 from flue gas, but the high cost and complexity of this process pose significant challenges for industrial applications. In contrast, directly converting CO2 in flue gas into useful chemicals or energy not only avoids the high-cost carbon capture process but also achieves more efficient carbon resource utilization. Among these technologies, biomethanation, a process that utilizes microorganisms to convert CO2 into methane, has demonstrated great potential in waste gas treatment and energy recovery. The low-concentration methane generated can be further converted into PHB (poly-β-hydroxybutyrate), a solid and easily recyclable product, by methanogenic bacteria. This conversion not only solves the problem of effective utilization of low-concentration methane but also achieves the ultimate goal of flue gas resource utilization.

[0003] However, due to the large flue gas flow rate and relatively low CO2 concentration (approximately 10%), hydrogen needs to be added at a stoichiometric ratio (H2:CO2 = 4:1) during biomethanation. The very low concentrations of hydrogen and CO2 result in poor mass transfer efficiency and a limited reaction rate. Furthermore, traditional trickle-bed reactor (TBR) technology has several problems when handling large volumes of low-concentration substrates. Traditional TBR reactors typically use a continuous top spray method to provide nutrient solution to the packing biofilm, leading to an excessively thick liquid film on the biofilm surface. This increases the mass transfer resistance of the liquid film, limiting the mass transfer rates of CO2 and hydrogen, and further reducing the efficiency of the methanation reaction. Summary of the Invention

[0004] The purpose of this invention is to provide an apparatus and method for the methanation of bidirectional flue gas, thereby solving the technical problems of excessively high mass transfer resistance caused by low hydrogen and CO2 concentrations and large liquid film thickness in the prior art. The various technical effects of the preferred solutions among the many technical solutions provided by this invention are detailed below.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] An apparatus for the methanation of bidirectional flue gas includes:

[0007] At least two gas phase reaction chambers are provided, each of which is stacked along the height direction and the joints of adjacent gas phase reaction chambers are interconnected; the gas phase reaction chambers form a gas phase reaction cavity for microbial reaction, and a porous biofilm carrier, a ceramic packing layer and a porous plate are sequentially arranged along the height direction inside the gas phase reaction chamber, and a gas chamber is formed between the porous biofilm carrier and the top of the gas phase reaction cavity.

[0008] The liquid storage tank is stacked and fixedly connected to the lower part of the bottom gas phase reaction tank along the height direction, and is interconnected with the bottom gas phase reaction tank at the contact point.

[0009] The nutrient solution replenishment mechanism is located outside the storage tank and each gas phase reaction tank. It is used to draw nutrient solution from the storage tank and replenish it into at least two gas phase reaction tanks. The nutrient solution replenished into the gas phase reaction tank can flow back to the storage tank in sequence through the porous biofilm carrier, the ceramic packing layer, and the porous plate.

[0010] A gas storage mechanism is installed outside the liquid storage tank and each gas phase reaction tank, and is connected to the liquid storage tank and the top gas phase reaction tank of at least two gas phase reaction tanks respectively. It is used to realize the sequential filling and discharge of gas from the liquid storage tank to each gas phase reaction tank, or the sequential filling and discharge of gas from the top gas phase reaction tank to the gas phase reaction tank and the liquid storage tank below.

[0011] The gas storage mechanism also includes a top gas outlet pipe located in the top gas phase reaction chamber and a bottom gas outlet pipe located in the liquid storage tank.

[0012] Furthermore, the gas storage mechanism includes a secondary gas outlet pipe, which is installed on a sub-top gas phase reaction box that is interconnected with the top gas phase reaction box, for discharging flue gas when the nutrient solution in the top gas phase reaction box is soaked.

[0013] Furthermore, the gas storage mechanism also includes a throttle valve and an exhaust pipe; the throttle valve is located between the liquid storage tank and the gas phase reaction tank, and between two adjacent gas phase reaction tanks, for use in blocking the flow during the immersion process of the corresponding gas phase reaction tank; the exhaust pipe is located between two gas phase reaction tanks separated by one gas phase reaction tank, and between the liquid storage tank and a gas phase reaction tank separated by one gas phase reaction tank, and an exhaust valve is correspondingly provided on the exhaust pipe for realizing the flow of flue gas during the immersion process of the corresponding gas phase reaction tank.

[0014] Furthermore, when there are two gas phase reaction chambers, they are arranged from bottom to top as a first gas phase reaction chamber and a second gas phase reaction chamber, and the exhaust pipe is located between the liquid storage tank and the second gas phase reaction chamber; when there are three gas phase reaction chambers, they are arranged from bottom to top as a first, second, and third gas phase reaction chamber, and the exhaust pipes are respectively located between the liquid storage tank and the second gas phase reaction chamber, and between the first gas phase reaction chamber and the third gas phase reaction chamber.

[0015] Furthermore, the porous biofilm carrier is made of carbon-supported sponge particles with adsorption capacity, and its volume in the gas phase reaction chamber accounts for 80% to 90% of the total volume of the gas phase reaction chamber.

[0016] Furthermore, the ceramic packing layer is disposed below the porous biofilm carrier in the gas phase reaction chamber, and its volume accounts for 5% to 10% of the total volume of the gas phase reaction chamber.

[0017] Furthermore, the porous plate is laid at the bottom of the gas phase reaction chamber. The porous plate has a pore diameter of 2~3mm and a pore spacing of 1~1.5mm, which is used for uniform gas distribution.

[0018] Furthermore, the volume of the gas chamber accounts for 5% to 10% of the total volume of the gas phase reaction chamber, and the gas chamber forms a gas flow channel with the ceramic packing layer below through the porous biofilm carrier, which is used to achieve gas buffering, uniform distribution and full contact with the porous biofilm carrier during bidirectional inflation.

[0019] A method for a bidirectional flue gas methanation unit includes the following steps:

[0020] Step 1: After being regulated, the flue gas enters the storage area and flows sequentially through at least two gas phase reaction chambers stacked along the height direction, providing a substrate for hydrogen-loving methanogens on the surface and in the pores of the porous biofilm carrier in each gas phase reaction chamber. After biotransformation is completed on the carrier surface, the flue gas is collected from the top outlet.

[0021] Step 2: After running for 10-40 hours, perform layered soaking: Increase the flue gas flow rate and pump the nutrient solution in the storage area into the top gas phase reaction tank. After forming "flooding", reduce the nutrient solution flow rate to keep the liquid level at 90% of the height of the gas phase reaction tank and soak for 5-60 minutes.

[0022] Step 3: Turn off the water pump and reduce the flue gas flow rate to disrupt the flooding. The nutrient solution flows back to the storage area through the gas phase reaction tanks below.

[0023] Step 4: Repeat the above operation to soak the remaining gas phase reaction chambers in layers in sequence. After soaking, the flue gas is regulated and enters the top gas phase reaction chamber from the top air inlet. It then flows through each gas phase reaction chamber below (downstream air inlet) to provide a substrate for hydrogen-loving methanogens and complete biotransformation. The flue gas is then discharged from the bottom air outlet.

[0024] Step 5: After running for 10-40 hours, switch the flue gas inlet direction (upflow inlet) and repeat steps 1-4; switch the inlet direction every 10-40 hours (alternating between upflow and downflow), and complete the stratified soaking of all gas phase reaction chambers after each switch to achieve continuous operation and maintenance of microbial activity.

[0025] Furthermore, step 2 of the layered soaking process also includes:

[0026] Immerse the topmost gas phase reaction chamber;

[0027] Close the throttle valve between the top gas phase reaction chamber and the second-top gas phase reaction chamber, open the secondary outlet pipe on the second-top gas phase reaction chamber, and at the same time close the top outlet pipe of the top gas phase reaction chamber; maintain the flue gas flow rate, so that the flue gas flows through the liquid storage tank and the lower gas phase reaction chamber connected to the liquid storage tank in sequence, enters the second-top gas phase reaction chamber, and is finally discharged through the secondary outlet pipe;

[0028] When the gas phase reaction chamber below the top is immersed;

[0029] Close the exhaust valve on the exhaust pipe between the target gas phase reaction chamber and other gas phase reaction chambers or storage tanks, and simultaneously close the throttle valve between the target gas phase reaction chamber and the lower gas phase reaction chamber; allow the flue gas to flow from the storage tank through the unsoaked lower gas phase reaction chamber in sequence, then bypass the target soaking chamber through the preset exhaust pipe, enter the upper unsoaked gas phase reaction chamber, and finally be discharged from the top exhaust pipe of the top gas phase reaction chamber, thereby realizing the layered alternating soaking of each gas phase reaction chamber and the continuous operation of the device.

[0030] This invention replaces the traditional top continuous spraying method in TBRs with layered soaking. While ensuring nutrient supply to the biofilm, the biofilm surface remains free of flowing nutrient solution for most of the operating time. This reduces the liquid film thickness on the biofilm surface, decreases mass transfer resistance, and thus increases the mass transfer rates of CO2 and hydrogen, promoting efficient methanation. Furthermore, combined gas-water backwashing can be performed during layered soaking, effectively preventing bed blockage caused by excessive biofilm growth. In addition, this technology enables continuous operation and uninterrupted nutrient solution supply, helping to maintain stable reactor operation and improving the reliability of long-term continuous operation. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1 This is a schematic diagram of an overall structure provided by an embodiment of the present invention;

[0033] Figure 2 This is a schematic diagram of the liquid storage tank structure provided in an embodiment of the present invention;

[0034] Figure 3This is another overall structural schematic diagram provided by an embodiment of the present invention.

[0035] Explanation of reference numerals in the attached drawings: 100, Gas phase reaction chamber; 101, First gas phase reaction chamber; 102, Second gas phase reaction chamber; 103, Third gas phase reaction chamber; 110, Porous plate; 120, Ceramic packing layer; 130, Porous biofilm carrier; 140, Gas chamber; 200, Liquid storage tank; 210, Liquid inlet; 220, Liquid outlet; 300, Liquid replenishment mechanism; 310, Water pump; 320, Liquid inlet pipe; 330, Liquid inlet valve; 400, Gas storage mechanism; 410, Gas source pipe; 420, Mass flow meter; 430, Three-way valve; 440, Top air inlet pipe; 450, Bottom air inlet pipe; 460, Air inlet valve; 470, Exhaust pipe; 480, Exhaust valve; 491, Top air outlet pipe; 492, Secondary air outlet pipe; 493, Bottom air outlet pipe. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be described in detail below. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other implementation methods obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0037] In the description of this invention, it should be noted that, unless otherwise stated, "a plurality of" means two or more; the terms "upper," "lower," "left," "right," "inner," "outer," "front end," "rear end," "head," "tail," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first," "second," "third," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0038] In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0039] The following is in conjunction with the appendix Figure 1-3 This application will be described in further detail.

[0040] Example 1

[0041] Reference Figure 1 and Figure 2 As shown, a bidirectional flue gas methanation device includes: a liquid storage tank 200, a gas phase reaction tank 100, a liquid replenishment mechanism 300, and a gas storage mechanism 400. Its flue gas treatment primarily targets the actual emissions from coal-fired power plants, which includes not only CO2, N2, and O2, but also dust, H2O, SO2, and NO. X The gaseous components are pretreated. Flue gas containing only CO2 and nitrogen is then introduced into the device for treatment. Simultaneously, H2, at a volume equivalent to four times the volume of CO2 in the flue gas, is introduced to support methanation during the reaction.

[0042] The storage tank 200 is located at the bottom of the device during use. At least two gas phase reaction tanks 100 are stacked and fixedly installed on the storage tank 200. The number of gas phase reaction tanks 100 can be stacked according to site conditions. From the gas phase reaction tank 100 in contact with the storage tank 200 upwards, they are sequentially designated as the first gas phase reaction tank 101, the second gas phase reaction tank 102, and so on (if more are stacked, the order continues sequentially). The contact points of adjacent gas phase reaction tanks 100 are interconnected to ensure smooth gas-liquid flow along the stacking direction. A replenishment mechanism 300 is located outside the storage tank 200 and each gas phase reaction tank 100, used to draw nutrient solution from the storage tank 200 and replenish it into at least two gas phase reaction tanks 100. The gas storage mechanism 400 is located outside the liquid storage tank 200 and each gas phase reaction tank 100, and is connected to the liquid storage tank 200 and the top gas phase reaction tank 100 of at least two gas phase reaction tanks 100 respectively. It is used to realize the sequential charging of gas from the liquid storage tank 200 to each gas phase reaction tank 100, or the sequential charging of gas from the top gas phase reaction tank 100 to the lower gas phase reaction tank 100 and the liquid storage tank 200, and to discharge the treated flue gas from the device.

[0043] The gas phase reaction chamber 100 forms a gas phase reaction cavity for microbial reaction. Inside the chamber, a porous biofilm carrier 130, a ceramic packing layer 120, and a porous plate 110 are arranged sequentially from top to bottom along the height direction. Each component, through specific material, size, and layout design, works together to improve the flue gas methanation efficiency.

[0044] The porous biofilm carrier 130 is made of carbon-supported sponge particles with high adsorption capacity. Its rough surface and porous structure significantly increase the attachment area for hydrogenophilic methanogens. Compared with ordinary carriers, it can increase the amount of active microorganisms attached by more than 30%, providing sufficient reaction substrates for the bioconversion of CO2 / CH4 in flue gas. At the same time, the adsorption characteristics of the carbon-supported sponge can temporarily adsorb substrates in the flue gas, avoiding sudden drops in local substrate concentration and ensuring stable microbial metabolism. The carrier occupies 80% to 90% of the total volume of the gas-phase reaction chamber. This high proportion design maximizes the contact probability between microorganisms and flue gas, reduces mass transfer waste caused by ineffective space, and further improves conversion efficiency.

[0045] A ceramic packing layer 120 is disposed below the porous biofilm carrier 130, preferably with a specific surface area ≥450 m². 2 / m 3 The Raschig rings or honeycomb ceramics, with their large specific surface area, can disperse the rising flue gas into tiny airflows, avoiding the direct impact of the airflow on the porous biofilm carrier 130, which would cause microorganisms to detach. At the same time, they can achieve secondary buffering and uniform distribution of the gas, solving the problems of local over-reaction and local unreaction caused by concentrated airflow in traditional reactors.

[0046] Its volume accounts for 5% to 10% of the total volume of the reaction zone. This proportion satisfies the gas distribution requirements without encroaching on the effective space of the porous biofilm carrier 130, achieving a balance between function and space. Furthermore, the ceramic packing layer 120 can form a rigid skeleton during the subsequent flooding process. With its high strength characteristics, it resists liquid impact and packing compression, preventing the porous biofilm carrier 130 from being compressed and deformed. This ensures that the carrier can quickly rebound and restore its original pore structure after flooding, guaranteeing that the gas-liquid flow path is not blocked.

[0047] A porous plate 110 is laid at the bottom of the gas-phase reaction chamber, serving as a supporting base for the ceramic packing layer 120 and the porous biofilm carrier 130. A secondary gas distribution channel is formed between the porous plate 110 and the ceramic packing layer 120. The flue gas is first distributed through the porous plate 110 and then further dispersed through the ceramic packing layer 120. This dual gas distribution design can improve the uniformity of flue gas flow by more than 40%, while significantly reducing the pressure drop (by 25% compared to a structure without the porous plate 110). This reduction in pressure drop not only reduces the energy consumption of power equipment such as fans but also avoids the inhibition of microbial activity caused by high pressure.

[0048] The porous plate 110 is preferably 40-60mm in length and width (adapting to different specifications of gas phase reaction chamber 100, with strong compatibility), 1-1.2mm in thickness (reducing material usage and space occupation while ensuring support strength), and has a pore diameter of 2-3mm and a pore spacing of 1-1.5mm. This small pore diameter and dense pore spacing design can cut flue gas bubbles into microbubbles with a diameter ≤5mm, increasing the gas-liquid contact area by more than 50%, thereby improving the gas-liquid mass transfer coefficient and solving the problem of excessively large bubbles and insufficient contact in traditional reactors.

[0049] Furthermore, the height of the gas-phase reaction chamber is preferably around 15cm. Compared to the bed height of over 30cm in traditional reactors, this reduces the overall gravity pressure drop of the packing and carrier in the reaction zone by more than 60%, preventing the carbon-supported sponge from compacting and collapsing due to excessive bed height. Simultaneously, the lower bed shortens the flow path of the nutrient solution and flue gas, reducing flow resistance and lowering the energy consumption of the replenishment and aeration equipment, thus achieving the dual advantages of high-efficiency reaction and low-energy operation.

[0050] In this process, a gas chamber 140 is formed between the porous biofilm carrier 130 and the top of the gas phase reaction chamber. The volume of the gas chamber 140 accounts for 5% to 10% of the total volume of the gas phase reaction chamber. The gas chamber 140 forms a gas flow channel with the ceramic packing layer 120 below through the porous biofilm carrier 130, which is used to achieve gas buffering, uniform distribution and full contact with the porous biofilm carrier 130 during bidirectional inflation.

[0051] The storage tank 200 is located at the bottom of the device during use. As the core carrier for nutrient solution storage and reflux, its bottom layout can ensure the integrity of nutrient solution collection, avoid resource waste caused by liquid residue, and at the same time provide stable bottom support for the entire device, improving the overall structural stability of the equipment.

[0052] The gas storage mechanism 400 includes a top gas outlet pipe 491, a bottom gas outlet pipe 493, a secondary gas outlet pipe 492, a throttle valve, an exhaust pipe 470, and a gas source pipe 410. The components work together precisely to achieve directional flow and treatment of flue gas. At the same time, the bidirectional flow air intake design optimizes the flue gas treatment efficiency. The specific structure is as follows.

[0053] The top vent pipe 491 is fixedly connected to the top of the top gas phase reaction chamber 100 (such as the second gas phase reaction chamber 102), and the bottom vent pipe 493 is fixedly connected to the liquid storage tank 200. The bottom vent pipe 493 is positioned higher than the liquid level inside the liquid storage tank 200. Both serve as exhaust channels for the treated gas under different inlet directions. The secondary vent pipe 492 is installed on the secondary top gas phase reaction chamber 100, which is interconnected with the top gas phase reaction chamber 100, to discharge flue gas during nutrient solution soaking in the top gas phase reaction chamber 100.

[0054] The throttle valve is preferably an electrically controlled valve (similar in structure to a ball valve), which forms a precisely controllable airflow channel inside. It is respectively set between the liquid storage tank 200 and the gas phase reaction tank 100, and between two adjacent gas phase reaction tanks 100. It can also be electrically connected to external devices such as a central control system to realize automated control of the working conditions.

[0055] During the normal intake and reaction phases, the electronically controlled throttle valve remains open, ensuring a completely unobstructed airflow path. This guarantees that the flue gas passes through at a stable flow rate, avoiding airflow attenuation caused by valve throttling and ensuring a uniform and stable gas supply to each reaction unit.

[0056] During the stratified soaking stage, when the central control system receives an instruction from a certain layer of the gas phase reaction chamber 100 to be soaked, it can send a closing signal to the corresponding electronically controlled throttle valve in real time. The valve closes rapidly within 1-2 seconds, physically blocking the path of gas flow through that layer. Compared with traditional manual valves, the response speed of electronically controlled valves is effectively improved.

[0057] The exhaust pipe 470 is located between the liquid storage tank 200 and any gas phase reaction tank 100, or between two gas phase reaction tanks 100 separated by at least one gas phase reaction tank 100. All exhaust pipes 470 are equipped with exhaust valves 480. When soaking in a specific gas phase reaction tank 100, the exhaust valve 480 of the corresponding exhaust pipe 470 is opened to achieve the diversion of flue gas flow, avoiding the waste of resources caused by the stagnation of flue gas in the soaking area, while ensuring the supply of flue gas to the unsoaked area. This allows the stratified soaking and continuous reaction to be carried out simultaneously. Compared with the traditional shutdown soaking mode, the equipment effectively improves the operating time.

[0058] A mass flow meter 420 and a three-way valve 430 are sequentially connected to the gas source pipe 410 (flue gas source) for transporting flue gas and hydrogen. The top gas phase reaction chamber 100 is equipped with a top inlet pipe 440, and the liquid storage tank 200 is equipped with a bottom inlet pipe 450. The three-way valve 430 is connected to the top inlet pipe 440, the bottom inlet pipe 450, and the mass flow meter 420, respectively. An inlet valve 460 is installed between the three-way valve 430 and both types of inlet pipes. The mass flow meter 420 can monitor and regulate the flue gas flow rate in real time to ensure stable inlet gas concentration and flow rate (flow fluctuation range controlled within ±5%), avoiding fluctuations in biofilm activity caused by unstable airflow. The inlet valve 460 preferably uses a one-way valve to completely prevent flue gas backflow, avoid mixing of flue gas from different directions in the pipe, ensure the uniqueness and stability of the inlet path, and further improve the controllability of reaction efficiency.

[0059] This invention fundamentally solves the problem of uneven mass transfer caused by traditional single-sided air intake through a bidirectional air intake design (alternating between upflow and downflow), as detailed below.

[0060] Upflow intake

[0061] During the first time period, the three-way valve 430 switches to connect the bottom inlet pipe 450 and the mass flow meter 420. The flue gas to be treated in the gas source pipe 410 sequentially passes through the mass flow meter 420, the three-way valve 430, and the bottom inlet pipe 450 into the liquid storage tank 200, and then flows upward through the first gas phase reaction tank 101 and the second gas phase reaction tank 102. After treatment, the flue gas is discharged from the top outlet pipe 491 of the second gas phase reaction tank 102.

[0062] All exhaust valves 480 on exhaust pipe 470 are closed (to prevent flue gas from splitting), the intake valve 460 between the three-way valve 430 and the top intake pipe 440 is closed (to prevent backflow), and the intake valve 460 between the three-way valve 430 and the bottom intake pipe 450 is open (to ensure smooth flow), and the bottom exhaust pipe 493 is sealed (to prevent untreated flue gas from being directly discharged). The throttling valves between the liquid storage tank 200 and the first gas phase reaction tank 101, and between the first and second gas phase reaction tanks 102 are all open (to ensure smooth upward airflow).

[0063] Downflow air intake

[0064] During the second time period, the three-way valve 430 switches to connect the top air inlet pipe 440 and the mass flow meter 420. The flue gas passes through the mass flow meter 420, the three-way valve 430, and the top air inlet pipe 440 in sequence into the second gas phase reaction box 102, and then flows down through the first gas phase reaction box 101 and the liquid storage tank 200. After processing, the flue gas is discharged from the bottom air outlet pipe 493 of the liquid storage tank 200.

[0065] All exhaust valves 480 on exhaust pipe 470 are closed, intake valve 460 between three-way valve 430 and bottom intake pipe 450 is closed and intake valve 460 between top intake pipe 440 is open, and top exhaust pipe 491 is sealed; all throttle valves remain open.

[0066] The first time period (downstream) and the second time period (upstream) alternate, with no overlap in gas supply time. This tidal operation mode achieves seamless contact across all reaction units through airflow direction switching, solving the problem of localized reaction blind spots inherent in traditional single-sided air intake. Furthermore, the alternation process eliminates the need for shutdowns, enabling 24-hour continuous operation in conjunction with subsequent stratified soaking. This effectively improves equipment utilization and avoids uneven biofilm distribution caused by prolonged unidirectional airflow, further stabilizing methanation conversion efficiency and ensuring long-term compliance with treatment standards.

[0067] The replenishment mechanism 300 includes an inlet pipe 320, a water pump 310, and an inlet 210, an outlet 220, and various valves on the storage tank 200, which are responsible for the storage, replenishment, and directional delivery of the nutrient solution.

[0068] The storage tank 200 has an inlet 210 on its side wall for replenishing sludge inoculation solution and nutrient solution, and a drain 220 at the bottom for discharging expired or contaminated liquid. This top-filling and bottom-draining design allows for complete replacement of the liquid in the storage tank 200, preventing microbial contamination caused by bottom accumulation and spoilage. Both the inlet 210 and drain 220 are preferably equipped with one-way valves as drain valves. These valves restrict unidirectional liquid flow (the inlet 210 only allows liquid to flow in, and the drain 220 only allows liquid to flow out), preventing backflow of nutrient solution or sludge inoculation solution and preventing residual liquid in the pipes from contaminating the storage tank 200, thus ensuring the cleanliness of the nutrient solution.

[0069] One end of the inlet pipe 320 connects to the water pump 310 and the storage tank 200, while the other end extends to each gas phase reaction tank 100 and communicates with the gas chamber 140 of the gas phase reaction tank 100. This communication with the gas chamber 140 allows the nutrient solution to permeate downwards from the gas chamber 140 to the porous biofilm carrier 130, preventing microbial detachment caused by direct impact on the carrier. Simultaneously, one-way valves are preferably installed as inlet valves 330 between the inlet pipe 320 and the storage tank 200, and between each gas phase reaction tank 100. These one-way valves precisely control the nutrient solution delivery path, enabling on-demand supply to specific gas phase reaction tanks 100, avoiding cross-flow issues when supplying multiple tanks. This allows for independent adjustment of the replenishment volume for each reaction tank, adapting to the different microbial nutrient requirements of different reaction tanks and improving nutrient solution utilization.

[0070] As a power source, the water pump 310 can adjust the output flow rate according to the soaking requirements. It can provide high flow rate power during flooding soaking (meeting the initial liquid supply requirement of 70~100mL / s) and switch to low flow rate mode (10~20mL / s) when maintaining the liquid level. Compared with the traditional fixed flow rate water pump 310, it avoids the problems of nutrient solution waste due to excessive flow rate or insufficient soaking due to insufficient flow rate.

[0071] Reference Figure 3 As shown, there are two stratified soaking methods (taking top-flow air intake and three gas phase reaction chambers 100 as an example, from bottom to top, they are the first, second, and third gas phase reaction chambers 103).

[0072] This invention designs two layered soaking methods for different working conditions, both of which are carried out under an upflow air intake state, which can achieve synergy between soaking maintenance and flue gas treatment, avoiding downtime losses.

[0073] Method 1: Layer-by-layer soaking

[0074] Open the inlet valve 330 of the inlet pipe 320 between the water pump 310 and the storage tank 200, as well as the inlet valve 330 corresponding to the target gas phase reaction chamber 100. The water pump 310 draws nutrient solution from the storage tank 200 and fills the corresponding gas phase reaction chamber 100. At the same time, the upward flue gas continuously flows from the storage tank 200 to the first, second, and third gas phase reaction chambers 103, and the airflow speed gradually increases.

[0075] When the apparent velocity of the gas reaches the flooding gas velocity, the upward drag force of the gas counteracts the gravity of the liquid, and the liquid cannot flow downward and accumulates in the packing layer to form a flooding phenomenon, thus completing the soaking of the porous biofilm carrier 130.

[0076] At this time, the top exhaust pipe 491 is opened to discharge the treated flue gas, the bottom exhaust pipe 493 is closed to prevent flue gas short circuit, all throttle valves are opened to ensure smooth airflow, and the exhaust pipe 470 and exhaust valve 480 are closed to prevent flue gas branching.

[0077] After soaking for 5-10 minutes, reduce the flue gas flow rate to break up flooding, allowing the nutrient solution to flow naturally into the next layer of the gas phase reaction chamber 100. When the liquid level of the next layer reaches the preset height (90% of the reaction chamber height), increase the flue gas flow rate again to form flooding, and repeat the above operation to achieve layer-by-layer soaking.

[0078] This soaking method eliminates the need for manual switching of the liquid supply path, relying on the natural flow after flooding to achieve layer-by-layer soaking. Simultaneously, the upward-flowing flue gas continuously passes through the unsoaked reaction chamber, ensuring uninterrupted flue gas treatment during soaking. Compared to soaking with the equipment shut down, this increases the effective operating time and improves flue gas treatment efficiency.

[0079] Method 2: Throttling valve controlled immersion

[0080] Example: Immersion in the third gas phase reaction chamber 103

[0081] Close the throttle valve between the third and second gas phase reaction chambers 102 (blocking the air / liquid flow between the upper and lower layers), open the inlet valve 330 of the water pump 310 and the liquid storage tank 200 and the third gas phase reaction chamber 103, and the water pump 310 directly fills the third gas phase reaction chamber 103 with liquid to achieve precise soaking.

[0082] Close the top exhaust pipe 491 and the bottom exhaust pipe 493, close the exhaust valve 480 (to prevent crossflow) of the exhaust pipe 470 between the third and first gas phase reaction chambers 101, and open the secondary exhaust pipe 492; the upward flue gas passes through the liquid storage tank 200, the first and second gas phase reaction chambers 102 in sequence and is then discharged from the secondary exhaust pipe 492, continuously treating the flue gas.

[0083] Example: Immersion in the second gas phase reaction chamber 102:

[0084] Close the throttle valve between the second and first gas phase reaction chambers 101, open the inlet valve 330 between the water pump 310 and the second gas phase reaction chamber 102, and directly fill the second chamber with liquid for immersion.

[0085] Close the secondary outlet pipe 492 and the bottom outlet pipe 493, close the exhaust valve 480 of the exhaust pipe 470 between the second gas phase reaction chamber 102 and the liquid storage tank 200, and open the exhaust valve 480 of the exhaust pipe 470 between the top outlet pipe 491 and the first and third gas phase reaction chambers 103. The upflow flue gas passes through the liquid storage tank 200, the first gas phase reaction chamber 101, the exhaust pipe 470, and the third gas phase reaction chamber 103 before being discharged from the top outlet pipe 491, maintaining flue gas treatment.

[0086] By precisely isolating the target soaking layer through the throttle valve, the nutrient solution is prevented from flowing into other reaction tanks, thus improving soaking efficiency. At the same time, the flexible switching between the exhaust pipe 470 and the gas outlet pipe ensures that the unsoaked layer forms a complete flue gas treatment path, maintaining treatment efficiency. This method is applicable to, but not limited to, scenarios where a single reaction tank needs emergency maintenance. Furthermore, when multiple gas phase reaction tanks 100 are stacked, it is only necessary to close the exhaust valve 480 between the corresponding gas phase reaction tank 100 and other gas phase reaction tanks 100 or the liquid storage tank 200 to achieve the soaking treatment in the manner described in the second gas phase reaction tank 102 in the above treatment example.

[0087] The two soaking methods can be switched according to actual operating needs. Both rely on the valves of the liquid replenishment mechanism 300 and the gas storage mechanism 400 to achieve layered maintenance and continuous reaction, solving the efficiency loss problem caused by the shutdown soaking of traditional reactors, while ensuring the activity of microorganisms and providing support for long-term stable methanation reaction.

[0088] Example 2

[0089] A method for a bidirectional flue gas methanation unit includes the following steps:

[0090] Method 1:

[0091] Step 1: Fill each gas phase reaction chamber 100 with porous carriers, with a filling rate of 100%; pre-store the prepared sludge mixture in the storage tank 200, start the water pump 310 to pump the sludge mixture into the reactor, so that the sludge mixture completely fills the reactor to soak the porous carriers; after soaking for 2 days, discharge the sludge mixture from the reactor, and a biofilm with methanogenic ability will be formed in the packing bed of the porous carrier, completing the inoculation.

[0092] Step 2: Upflow flue gas reaction

[0093] The flue gas to be treated, after being regulated by mass flow meter 420 and three-way valve 430, enters the storage area from the bottom inlet pipe 450 of storage tank 200, and flows sequentially through at least two gas phase reaction chambers 100 stacked along the height direction (from bottom to top: lower and upper gas phase reaction chambers 100), with the throttling valves between each gas phase reaction chamber 100 remaining open. The flue gas provides a substrate for hydrogenophilic methanogens on the surface and in the pores of the porous biofilm carrier 130 within each gas phase reaction chamber 100. After biotransformation is completed on the carrier surface, the flue gas is discharged from the top outlet pipe 491 of the top gas phase reaction chamber 100.

[0094] Step 3: Flooding with stratified liquid

[0095] After running continuously for 10-40 hours in step 2, perform stratified soaking:

[0096] Increase the flue gas flow rate to 3-5 L / min, and start the water pump 310 to pump the nutrient solution in the storage area into the top gas phase reaction tank 100 through the inlet pipe 320. Within 3-6 seconds, the nutrient solution will flood in the top gas phase reaction tank 100. Then, reduce the nutrient solution flow rate to 10-20 mL / s to maintain the liquid level at 90% of the height of the gas phase reaction tank 100, and keep it soaking for 5-60 minutes. During this period, the throttling valves between the gas phase reaction tanks 100 remain open to ensure basic airflow.

[0097] Step 4: Break the flooding and return the nutrient solution

[0098] After soaking, turn off the water pump 310 and reduce the flue gas flow rate to 100~1000mL / min (determined according to the empty bed residence time under the current operating conditions) to break the flooding state; under the action of gravity, the nutrient solution flows through the lower gas phase reaction tanks 100 in sequence along the opened throttle valve channel and finally flows back to the storage area.

[0099] Step 5: Switching between layer-by-layer soaking and downflow immersion

[0100] Repeat steps 3-4 to sequentially perform stratified flooding soaking on the remaining gas phase reaction chambers 100 below; after all gas phase reaction chambers 100 are soaked, adjust the three-way valve 430 to switch to downflow air intake: the flue gas to be treated enters from the top air intake pipe 440 of the top gas phase reaction chamber 100 after regulation, flows through each gas phase reaction chamber 100 below in sequence (each throttle valve remains open), continues to provide substrate for hydrogenophilic methanogens and completes biotransformation, and finally is discharged from the bottom air outlet pipe 493 of the storage tank 200.

[0101] Step 6: Alternating and continuous intake direction

[0102] After running continuously for 10-40 hours in step 5, adjust the three-way valve 430 again to switch to upflow air intake, and repeat steps 2-5; switch the air intake direction every 10-40 hours (alternating between upflow and downflow), and complete the stratified flooding soaking of all gas phase reaction chambers 100 within 60 minutes after each switch to achieve continuous operation of the device and maintenance of microbial activity.

[0103] Method 2: A method for treating flue gas by closing the corresponding throttle valve and bypassing the exhaust pipe at 470°.

[0104] Step 1: Fill each gas phase reaction chamber 100 with porous carriers, with a filling rate of 100%; pre-store the prepared sludge mixture in the storage tank 200, start the water pump 310 to pump the sludge mixture into the reactor, so that the sludge mixture completely fills the reactor to soak the porous carriers; after soaking for 2 days, discharge the sludge mixture from the reactor, and a biofilm with methanogenic ability will be formed in the packing bed of the porous carrier, completing the inoculation.

[0105] Step 2: Upflow flue gas reaction

[0106] The flue gas to be treated, after being regulated by the mass flow meter 420 and the three-way valve 430, enters the storage area from the bottom inlet pipe 450 of the storage tank 200, and flows sequentially through at least two gas phase reaction chambers 100 stacked along the height direction (from bottom to top: first, second, ..., Nth gas phase reaction chamber 100), with the throttling valves between each gas phase reaction chamber 100 kept open, and the exhaust valves 480 on each exhaust pipe 470 kept closed. The flue gas provides a substrate for the hydrogenophilic methanogens on the surface and in the pores of the porous biofilm carrier 130 in each gas phase reaction chamber 100. After biotransformation is completed on the carrier surface, the flue gas is discharged from the top outlet pipe 491 of the top gas phase reaction chamber 100 (Nth gas phase reaction chamber 100).

[0107] Step 3: Layered soaking and smoke avoidance

[0108] After running continuously for 10 hours in Step 1, perform stratified soaking as follows:

[0109] (1) Soak the top gas phase reaction chamber 100 (Nth gas phase reaction chamber 100)

[0110] Close the throttle valve between the Nth gas phase reaction chamber 100 and the second-to-top gas phase reaction chamber 100 (N-1th gas phase reaction chamber 100), open the secondary outlet pipe 492 on the N-1th gas phase reaction chamber 100, and simultaneously close the top outlet pipe 491 of the Nth gas phase reaction chamber 100; maintain the flue gas flow rate at 100~1000mL / min, so that the flue gas flows sequentially through the storage tank 200 and the unsoaked gas phase reaction chambers 100 below (first to N-1th gas phase reaction chambers 100), and then is discharged from the secondary outlet pipe 492; start the water pump 310 to pump the nutrient solution from the storage area into the Nth gas phase reaction chamber 100, and soak for 5~10 minutes.

[0111] (2) Immersion in the top and below gas phase reaction chamber 100 (target immersion chamber, taking the Kth gas phase reaction chamber 100 as an example, K < N)

[0112] Close the throttle valve between the Kth gas phase reaction chamber 100 and the lower gas phase reaction chamber 100 (K-1th gas phase reaction chamber 100), and simultaneously close the exhaust valve 480 on the exhaust pipe 470 between the Kth gas phase reaction chamber 100 and other gas phase reaction chambers 100 / storage tank 200; allow the flue gas to flow from the storage tank 200 through the unsoaked lower gas phase reaction chambers 100 (first to K-1th gas phase reaction chambers 100), bypass the Kth gas phase reaction chamber 100 through the preset exhaust pipe 470, and enter the upper unsoaked gas phase reaction chambers 100 (K+1th to Nth gas phase reaction chambers 100), and finally discharge from the top exhaust pipe 491 of the Nth gas phase reaction chamber 100; start the water pump 310 to pump the nutrient solution from the storage area into the Kth gas phase reaction chamber 100, and soak for 5-10 minutes;

[0113] Step 4: Downstream Switching and Continuous Operation

[0114] After all gas phase reaction chambers 100 have been soaked, adjust the three-way valve 430 to switch to downflow air intake: the flue gas to be treated enters from the top air intake pipe 440 of the Nth gas phase reaction chamber 100 after regulation, flows through the unsoaked gas phase reaction chambers 100 below in sequence (each throttling valve is reopened and the exhaust valve 480 is reopened), continues to provide substrate for hydrogenophilic methanogens and completes biotransformation, and finally is discharged from the bottom air outlet pipe 493 of the storage tank 200.

[0115] After running continuously for 10 to 40 hours in step 5, adjust the three-way valve 430 again to switch to the upflow air intake, and repeat steps 2 to 4; switch the air intake direction every 10 to 40 hours (alternating between upflow and downflow), and complete the stratified soaking of all gas phase reaction chambers 100 within 60 minutes after each switch, so as to realize the stratified alternating soaking of each gas phase reaction chamber 100 and the continuous operation of the device.

[0116] The flooding phenomenon in this invention is closely related to the characteristics of the packing layer and the hydrodynamic mechanism of gas-liquid interaction. Specifically, it can be quantitatively and qualitatively analyzed through the classical Sherwood correlation and reactor structural characteristics.

[0117] The effect of packing layer characteristics on flooding gas velocity

[0118] The ceramic packing layer 120 inside the reactor, together with the porous carbon-supported sponge, constitutes a high specific surface area (a) and low porosity (a). The filling layer significantly reduces the flooding gas velocity of the system, allowing the device to enter the flooding zone at a lower gas velocity, thereby achieving the purpose of liquid retention and extending the residence time.

[0119] High specific surface area (a): The flooding gas velocity is inversely proportional to a. A high specific surface area causes the liquid to disperse into a thin liquid film or be retained in tiny pores. The drag effect is more significant when the gas flows through it, so a lower gas velocity can hinder the downward flow of the liquid and achieve flooding.

[0120] Low porosity The porous biofilm carrier 130 has a filling rate of 85%~100%, and the average porosity of the reaction zone is... Extremely low. Flooding velocity and Proportional to the decrease in porosity, the gas flow channels become narrower, and the local actual gas velocity is much higher than the apparent gas velocity. This leads to a sharp increase in the shear force and drag force exerted on the liquid, which significantly reduces the apparent gas velocity required for flooding.

[0121] Liquid holdup changes and flooding triggering mechanisms

[0122] Flooding is accompanied by a sharp increase in liquid holdup within the packing layer: the liquid holdup is stable in the normal operating zone, but when the gas velocity approaches the flooding point, the gas-liquid friction and liquid gravity reach a critical equilibrium, and the liquid holdup begins to rise non-linearly. In this invention, the carbon-supported sponge particles, with their ultra-high internal porosity and hydrophilicity, act like a liquid reservoir, trapping a large amount of liquid through capillary action and surface adsorption, resulting in a local liquid holdup far exceeding that of ordinary packing materials. This allows the system to reach the critical liquid holdup state required for flooding more quickly, ultimately achieving precise and efficient stratified soaking.

[0123] For flooding in packed towers, the classic Sherwood correlation reveals the quantitative relationship between various parameters:

[0124]

[0125] in:

[0126] Flooding gas velocity, which is the apparent gas velocity when flooding occurs;

[0127] Gravitational acceleration;

[0128] Specific surface area of ​​packing (surface area of ​​packing per unit volume);

[0129] : Porosity of the filler layer;

[0130] , : gas and liquid density;

[0131] Liquid viscosity;

[0132] , is the liquid-to-gas kinetic energy ratio;

[0133] : Empirical constant.

[0134] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. An apparatus for bi-flow flue gas methanation, characterized in that, The application relates to a gas phase reaction device for microbial reaction. The device comprises at least two gas phase reaction boxes (100), each of which is arranged in a stacking mode along a height direction and is communicated with each other at the abutting position of two adjacent gas phase reaction boxes (100); the gas phase reaction box (100) is internally formed with a gas phase reaction cavity for microbial reaction, which is internally sequentially provided with a porous biofilm carrier (130), a ceramic filler layer (120) and a porous plate (110) along the height direction, the porous biofilm carrier (130) and the top of the gas phase reaction cavity form a gas chamber (140), the porous plate (110) is laid at the bottom of the gas phase reaction cavity and serves as a supporting base of the ceramic filler layer (120) and the porous biofilm carrier (130), and a secondary gas distribution channel is formed between the porous plate (110) and the ceramic filler layer (120); a liquid storage tank (200) is fixedly connected to the lower part of the bottom gas phase reaction box (100) in a stacking mode along the height direction and is communicated with the abutting position of the bottom gas phase reaction box (100); a liquid supplementing mechanism (300) is arranged outside the liquid storage tank (200) and each gas phase reaction box (100) and is used for extracting nutrient solution from the liquid storage tank (200) and supplementing the nutrient solution into the at least two gas phase reaction boxes (100) respectively; the nutrient solution supplemented into the gas phase reaction box (100) can flow back to the liquid storage tank (200) through the porous biofilm carrier (130), the ceramic filler layer (120) and the porous plate (110) in sequence; a gas storage mechanism (400) is arranged outside the liquid storage tank (200) and each gas phase reaction box (100) and is communicated with the liquid storage tank (200) and the top gas phase reaction box (100) of the at least two gas phase reaction boxes (100) respectively, and is used for realizing the charging and discharging of the gas from the liquid storage tank (200) to each gas phase reaction box (100) in sequence or from the top gas phase reaction box (100) to the gas phase reaction box (100) below and the liquid storage tank (200) in sequence; the gas storage mechanism (400) further comprises a top gas outlet pipe (491) arranged in the top gas phase reaction box (100) and a bottom gas outlet pipe (493) arranged in the liquid storage tank (200).

2. A device for bi-flowing flue gas methanation according to claim 1, characterized in that, the gas storage mechanism (400) comprises a secondary gas outlet pipe (492) which is arranged on a secondary top gas phase reaction box (100) connected with the top gas phase reaction box (100) and is used for discharging flue gas when the top gas phase reaction box (100) is soaked with nutrient solution.

3. The apparatus for bi-flowing flue gas methanation according to claim 1, characterized in that, The gas storage mechanism (400) further comprises a throttle valve and an exhaust pipe (470); the throttle valve is arranged between the liquid storage tank (200) and the gas phase reaction tank (100), and between two adjacent gas phase reaction tanks (100), and is used for cutting off the flow during the soaking of the corresponding gas phase reaction tank (100); the exhaust pipe (470) is arranged between two gas phase reaction tanks (100) spaced by one gas phase reaction tank (100), and between the liquid storage tank (200) and the gas phase reaction tank (100) spaced by one gas phase reaction tank (100), and a corresponding exhaust valve (480) is arranged on the exhaust pipe (470), and is used for realizing the flow of flue gas during the soaking of the corresponding gas phase reaction tank (100).

4. A device for bi-flowing flue gas methanation according to claim 3, characterized in that, When the gas phase reaction tank (100) is two, the first gas phase reaction tank (101) and the second gas phase reaction tank (102) are arranged from bottom to top, and the exhaust pipe (470) is arranged between the liquid storage tank (200) and the second gas phase reaction tank (102); or when the gas phase reaction tank (100) is three, the first, second and third gas phase reaction tanks (103) are arranged from bottom to top, and the exhaust pipe (470) is arranged between the liquid storage tank (200) and the second gas phase reaction tank (102), and between the first gas phase reaction tank (101) and the third gas phase reaction tank (103).

5. The apparatus for bi-lateral flow flue gas methanation according to claim 1, wherein, The porous biological membrane carrier (130) is made of carbon-loaded sponge particles with adsorption capacity, and the volume of the porous biological membrane carrier (130) in the gas phase reaction cavity accounts for 80%-90% of the total volume of the gas phase reaction cavity.

6. The apparatus for bi-lateral flow flue gas methanation according to claim 1, wherein, The ceramic filler layer (120) is arranged below the porous biological membrane carrier (130) in the gas phase reaction cavity, and the volume of the ceramic filler layer (120) accounts for 5%-10% of the total volume of the gas phase reaction cavity.

7. The apparatus for bi-lateral flow flue gas methanation according to claim 1, wherein, The pore diameter of the porous plate (110) is 2-3 mm, and the hole distance is 1-1.5 mm, which is used for uniform gas distribution.

8. The apparatus for bi-flowing flue gas methanation according to claim 1, characterized in that, The volume of the gas chamber (140) accounts for 5%-10% of the total volume of the gas phase reaction cavity, and the gas chamber (140) forms a gas flow channel with the lower ceramic filler layer (120) through the porous biological membrane carrier (130), which is used for realizing gas buffering, uniform distribution and sufficient contact with the porous biological membrane carrier (130) during bidirectional aeration.

9. A method for a bi-flowing flue gas methanation plant according to any of claims 1 to 8, characterized in that, The method comprises the following steps: Step 1: After the flue gas is regulated, it enters the liquid storage area, and then flows through at least two gas phase reaction tanks (100) stacked in the height direction, so as to provide substrates for the hydrogenophilic methanogens on the surface and in the pores of the porous biological membrane carrier (130) in each gas phase reaction tank (100), and the biological conversion is completed on the surface of the carrier, and then the flue gas is collected from the top gas outlet; Step 2: After running for 10-40 hours, layered soaking is performed: the flue gas flow is increased, the nutrient solution in the liquid storage area is pumped into the topmost gas phase reaction tank (100), the liquid level is maintained at 90% of the height of the gas phase reaction tank (100) after the liquid level is lowered, and the liquid level is maintained at 90% of the height of the gas phase reaction tank (100) after the liquid level is lowered, and the liquid level is maintained at 90% of the height of the gas phase reaction tank (100) after the liquid level is lowered, and the liquid level is maintained at 90% of the height of the gas phase reaction tank (100) after the liquid level is lowered, and the liquid level is maintained at 90% of the height of the gas phase reaction tank (100) after the liquid level is lowered, and the liquid level is maintained at 90% of the height of the gas phase reaction tank (100) after the liquid level is lowered, and the liquid level is maintained at 90% of the height of the gas phase reaction tank (100) after the liquid level is lowered, and the liquid level is maintained at 90% of the height of the gas phase reaction tank (100) after the liquid level is lowered, and the liquid level is maintained at 90% of the height of the gas phase reaction tank (100) after the liquid level is lowered, and the liquid level is maintained at 90% of the height of the gas phase reaction tank (100) after the liquid level is lowered, and the liquid level is maintained at 90% of the height of the gas phase reaction tank (100) after the liquid level is lowered, and the liquid level is maintained at 90% of the height of the gas phase reaction tank (100) after the liquid level is lowered, and the liquid level is maintained at 90% of the height of the gas phase reaction tank (100) after the liquid level is lowered, and the liquid level is maintained at 90% of the height of the gas phase reaction tank (100) after the liquid level is lowered, and the liquid level is maintained at 90% of the height of the gas phase reaction tank (100) after the liquid level is lowered, and the liquid level is maintained at 90% of the height of the gas phase reaction tank (100) after the liquid level is lowered, and the liquid level is maintained at 90% of the height of the gas phase reaction tank (100) after the liquid level is lowered, and the liquid level is maintained at 90% of the height of the gas phase reaction tank (100) after the liquid level is lowered, and the liquid level is maintained at 90% of the height of the gas phase reaction tank (100) after the liquid level is lowered, and the liquid level is maintained at 90% of the height of the gas phase reaction tank (100) after the liquid level is lowered, and the liquid level is maintained at 90% of the height of the gas phase reaction tank (100) after the liquid level is lowered, and the liquid level is maintained at 90% of the height of the gas phase reaction tank (100) after the liquid level is lowered, and the liquid level is maintained at 90% of the height of the gas phase reaction tank (100) after the liquid level is lowered, and the liquid level is maintained at 90% of the height of the gas phase reaction tank (100) after the liquid level is lowered, and the liquid level is maintained at 90% of the height of the gas phase reaction tank (100) after the liquid level is lowered, and the liquid level is maintained at 90% of the height of the gas phase reaction tank (100) after the liquid level is lowered, and the liquid level is maintained at 90% of the height of the gas phase reaction tank (100) after the liquid level is lowered, and the liquid level is maintained at 90% of the height of the gas phase reaction tank (100) after the liquid level is lowered, and the liquid level is maintained at 90% of the height of the gas phase reaction tank (100) after the liquid level is lowered, and the liquid level is maintained at 90% of the height of the gas phase reaction tank (100) after the liquid level is lowered, and the liquid level is maintained at 90% of the height of the gas phase reaction tank (100) after the liquid level is lowered, and the liquid level is maintained at 90% of the height of the gas phase reaction tank (100) after the liquid level is lowered, and the liquid level is maintained at 90% of the height of the gas phase reaction tank (100) after the liquid level is lowered, and the liquid level is maintained at 90% of the height of the gas phase reaction tank (100) after the liquid level is lowered, and the liquid level is maintained at 90% of the height of the gas phase reaction tank (100) after the liquid level is lowered, and the liquid level is maintained at 90% of the height of the gas phase reaction tank (100) after the liquid level is lowered, and the liquid level is maintained at 90% of the height of the gas phase reaction tank (100) after the liquid level is lowered, and the liquid level is maintained at 90% of the height of the gas phase reaction tank (100) after the liquid level is lowered, and the liquid level is maintained at 90% of the height of the gas phase reaction tank (100) after the liquid level is lowered, and the liquid level is maintained at 90% of the height of the gas phase reaction tank (100) after the liquid level is lowered, and the liquid level is maintained at 90% of the height of the gas phase reaction tank (100) after the liquid level is lowered, and the liquid level is maintained at 90% of the height of the gas phase reaction tank (100) after the liquid level is lowered, and the liquid level is maintained at 90% of the height of the gas phase reaction tank (100) after the liquid level is lowered, and the liquid level is maintained at 90% of the height of the gas phase reaction tank (100) after the liquid level is lowered, and the liquid level is maintained at 90% of the height of the gas phase reaction tank (100) after the liquid level is lowered, and the liquid level is maintained at 90% of the height of the gas phase reaction tank (100) after the liquid level is lowered, and the liquid level is maintained at ​ Step 4: Repeat the above operation, sequentially layering the remaining gas phase reaction tank (100) below, after soaking, the flue gas enters the topmost gas phase reaction tank (100) from the top inlet after regulation, sequentially flows through each gas phase reaction tank (100) below, i.e. downflowing gas inlet, provides substrate for hydrogen-utilizing methanogens and completes biological conversion, and is discharged from the bottom gas outlet; Step 5: After running for 10-40 hours, switch the flue gas inlet direction, i.e. upflowing gas inlet, repeat steps 1-4; switch the inlet direction every 10-40 hours, i.e. upflowing and downflowing alternately, complete layering soaking of all gas phase reaction tanks (100) after each switch, and realize continuous operation and maintenance of microbial activity.

10. A process for a bi-flowing flue gas methanation unit as claimed in claim 9 wherein, The layering soaking in step 2 further comprises: Soaking the topmost gas phase reaction tank (100); Close the throttle valve between the topmost gas phase reaction tank (100) and the second topmost gas phase reaction tank (100), open the secondary gas outlet pipe (492) on the second topmost gas phase reaction tank (100), and close the top gas outlet pipe (491) of the topmost gas phase reaction tank (100); maintain the flue gas flow, so that the flue gas sequentially flows through the liquid storage tank (200), the lower gas phase reaction tank (100) connected with the liquid storage tank (200), enters the second topmost gas phase reaction tank (100), and is finally discharged from the secondary gas outlet pipe (492); When soaking the gas phase reaction tank (100) below the second topmost gas phase reaction tank (100); Close the exhaust valve (480) on the exhaust pipe (470) between the target gas phase reaction tank (100) and other gas phase reaction tanks (100) or the liquid storage tank (200), and close the throttle valve between the target gas phase reaction tank (100) and the lower gas phase reaction tank (100); make the flue gas sequentially flow through the lower gas phase reaction tank (100) which is not soaked from the liquid storage tank (200), then bypass the target soaking tank through the pre-set exhaust pipe (470), enter the upper gas phase reaction tank (100) which is not soaked, and finally be discharged from the top gas outlet pipe (491) of the topmost gas phase reaction tank (100), realizing layering and alternating soaking of each gas phase reaction tank (100) and continuous operation of the device.

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