Apparatus and method for bidirectional flow hydrogenotrophic carbon dioxide methanation

Abstract

A bidirectional flow hydrogenophilic carbon dioxide methanation apparatus and method comprises two stages: cultivation and normal operation. Both stages include a dry biomethanation mode and a wet immersion mode on a biofilm carrier. In the dry biomethanation mode of the cultivation stage, cultivation is initially performed using an upward flow inlet, then switched to a downward flow inlet. During normal operation, a mixture of hydrogen and carbon dioxide is alternately introduced into the gas-phase reaction zone from both ends of the apparatus, flowing upwards and downwards. The biofilm, in a static, drained state, converts the hydrogen and carbon dioxide into methane and water. In the wet immersion mode on the biofilm carrier, the porous biofilm carrier is immersed in a nutrient solution, allowing the microorganisms attached to its pores and surface to obtain nutrients, promoting microbial growth and reproduction. This invention can improve biomass and carbon dioxide conversion efficiency under low-cost conditions, providing an effective pathway for carbon dioxide resource utilization.

Description

Technical Field

[0001] This invention belongs to the field of carbon dioxide resource utilization technology, and relates to carbon dioxide methanation treatment, particularly to a bidirectional flow hydrogenophilic carbon dioxide methanation apparatus and method. Background Technology

[0002] Carbon dioxide can be converted into a range of clean fuels and chemicals, such as methane, methanol, ethanol, acetic acid, or hexanoic acid, through technologies such as catalytic conversion, electrochemical reduction, photochemical conversion, photoelectrocatalytic conversion, and bioconversion. The first four conversion technologies are chemical catalytic processes, which, while achieving high conversion rates, require highly selective catalysts and suffer from poor selectivity and high operating costs. Bioconversion, using enzymes within microorganisms as catalysts, can achieve high selectivity, low energy consumption, low cost, and low environmental pollution in carbon dioxide conversion under mild conditions. Methane produced from the methanation of hydrogen and carbon dioxide, once it reaches the required purity, can be directly injected into existing mature natural gas grid infrastructure or compressed into liquefied natural gas for energy storage or utilization. This method has high energy storage potential and relatively high energy utilization efficiency, offering excellent utilization value and favorable existing infrastructure.

[0003] Currently, the most studied hydrogenophilic carbon dioxide methanation devices include continuous stirred reactors (e.g., WAHID R, HORN S J. The effect of mixing rate and gas recirculation on biological CO2methanation in two-stage CSTR systems[J]. Biomass and Bioenergy, 2021, 144: 105918; ORGILL JJ, ATIYEH HK, DEVARAPALLI M, et al. A comparison of mass transfer coefficients between trickle-bed, hollow fiber membrane and stirredtank reactors[J]. Bioresource Technology, 2013, 133: 340-6) and trickle bed reactors (e.g., ARYAL N, ODDE M, PETERSEN C,et al.Methane production from syngasusing a trickle-bed reactor setup[J].Bioresource Technology,2021,333:125183;SPOSOB M,WAHID R,FISCHER K.Ex-situ biological CO2 methanation using tricklebed reactor:review and recent advances[J].Reviews in Environmental Scienceand Bio / Technology,2021;ULLRICH T,LINDNER J, K, et al. Influence of operating pressure on the biological hydrogen methanation in trickle-bed reactors[J]. Bioresource Technology, 2018, 247: 7-13) and membrane reactors (e.g., PRATOFIORITOG, HACKBARTH M, MANDEL C, et al. A membrane biofilm reactor for hydrogenotrophicmethanation[J]. Bioresource Technology, 2021, 321: 124444). However, continuous stirred reactors have high energy consumption, trickle-bed reactors have uneven biomass distribution, membrane reactors have expensive membrane materials and are prone to membrane fouling, and generally suffer from low gas-liquid mass transfer rates and low biomass, resulting in low carbon dioxide conversion efficiency. Summary of the Invention

[0004] In order to overcome the shortcomings of the prior art, the present invention aims to provide a bidirectional flow hydrogenophilic carbon dioxide methanation apparatus and method to improve gas-liquid mass transfer and address the problem of uneven biomass distribution, thereby increasing carbon dioxide conversion efficiency.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A bidirectional flow hydrogenophilic carbon dioxide methanation device includes a chamber, which is divided from top to bottom into a gas phase reaction zone, a liquid phase reaction zone, and a gas phase diffusion zone. The gas phase reaction zone and the liquid phase reaction zone are filled with porous biofilm carriers. A microplate is disposed between the gas phase diffusion zone and the liquid phase reaction zone. An upper sampling port is provided at the upper part of the gas phase reaction zone and a lower sampling port is provided at the lower part.

[0007] The liquid phase reaction zone forms a loop with the buffer bottle, which stores a mixture of sludge and nutrient solution. The loop is configured to control the flow rate of the mixture so that the porous biofilm carrier in the gas phase reaction zone is in an alternating state of soaking and draining.

[0008] In the drained state, the hydrogen and carbon dioxide mixture is configured in an upflow inlet mode and a downflow inlet mode. In the upflow inlet mode, the mixture enters the gas phase reaction zone through the gas phase diffusion zone and the liquid phase reaction zone, where it undergoes biotransformation by hydrogenophilic methanogens, and the effluent is collected through the upper sampling port. In the downflow inlet mode, the mixture enters the gas phase reaction zone through the upper sampling port, where it undergoes biotransformation by hydrogenophilic methanogens, and the effluent is collected through the lower sampling port.

[0009] In one embodiment, the porous biofilm carrier is a carbon-supported sponge particle with adsorption capacity, having a filling rate of 80-100%, and active hydrogenophilic methanogenic bacteria are attached to its surface and internal pores.

[0010] In one embodiment, the gas phase diffusion zone occupies 5-10% of the total chamber volume, the gas phase reaction zone occupies 65-70% of the total chamber volume, and the liquid phase reaction zone occupies 20-30% of the total chamber volume.

[0011] In one embodiment, a peristaltic pump is installed on the circuit, and the amount of mixed liquid in the gas phase reaction zone and the circulation of the circuit are controlled by adjusting the direction and flow rate of the peristaltic pump; a mass flow controller and a gas path valve are installed on the gas supply pipeline of the mixed gas.

[0012] The present invention also provides a method for bidirectional flow hydrogenophilic carbon dioxide methanation, implemented based on the bidirectional flow hydrogenophilic carbon dioxide methanation apparatus, including a cultivation stage and a normal operation stage;

[0013] The cultivation phase includes:

[0014] Step 1.1: Pump the mixture into the liquid phase reaction zone and the gas phase reaction zone until the biofilm carrier is submerged. The biofilm carrier is continuously immersed in the mixture. Then, drain all the mixture from the gas phase reaction zone to keep the liquid phase reaction zone submerged in the mixture.

[0015] Step 1.2: Adjust the flow rate of the mixture so that the mixture circulates in the loop;

[0016] Step 1.3: The mixed gas is fed into the gas phase diffusion zone, passes through the liquid phase reaction zone via a microporous plate, and finally enters the gas phase reaction zone in an upflow manner. The mixed gas is biotransformed by hydrogenophilic methanogens. The gas is collected through the upper sampling port, and then the gas supply is stopped.

[0017] Step 1.4: Repeat steps 1.1 to 1.3 until the biofilm on the porous biofilm carrier has achieved the required hydrogenophilic carbon dioxide methanation effect, and then complete the upflow culture stage.

[0018] Step 1.5: The mixed gas is fed into the gas phase reaction zone through the upper sampling port and then fed into the gas phase reaction zone by a flow meter. Hydrogen-loving methanogens biotransform the mixed gas. The gas produced during the process is collected through the lower sampling port, and then the gas supply is stopped.

[0019] Step 1.6, repeat steps 1.1, 1.2 and 1.5 until efficient hydrogenophilic carbon dioxide methanation can be achieved, that is, the carbon dioxide conversion efficiency can be stably maintained at 80%-90%, and then the downflow culture stage is completed.

[0020] The normal operation phase includes:

[0021] The cycle of steps 1.1, 1.2, 1.3, and 1.5 involves the biofilm in a static, draining state converting hydrogen and carbon dioxide into methane and water until the carbon dioxide conversion efficiency is stably maintained at over 95%.

[0022] In one embodiment, during the cultivation and normal operation phases, the device maintains an anaerobic constant temperature environment with a reaction temperature of 35-37°C and a chamber pressure of 0-5 bar.

[0023] In one embodiment, in step 1.1, the biofilm carrier is continuously immersed in the mixed solution for 30-60 minutes; in step 1.3, during the upflow culture stage, the dry biomethanation mode lasts for 1-5 days, and during normal operation, the upflow dry biomethanation mode lasts for 1-3 days; in step 1.5, during the downflow culture stage, the dry biomethanation mode lasts for 1-5 days, and during normal operation, the downflow dry biomethanation mode lasts for 1-3 days; in step 1.4, the upflow culture stage is completed after the empty bed residence time reaches 30-40 minutes; in step 1.6, the downflow culture stage is completed after the empty bed residence time reaches 10-20 minutes.

[0024] In one embodiment, step 1.1 is a wet immersion mode of the biofilm carrier, and steps 1.2 to 1.3 and step 1.5 are all dry biomethanation modes; steps 1.1, 1.2 and 1.3 constitute an upflow culture stage, and steps 1.1, 1.2 and 1.5 constitute a downflow culture stage.

[0025] The upflow culture stage and the downflow culture stage (downflow culture begins only after upflow culture is completed) each consist of a soaking cycle of 72±2 hours, during which the biofilm carrier is kept in wet soaking mode for 1 hour, and the remaining time is in dry biomethanation mode; the normal operation stage consists of a soaking cycle of 96±2 hours, during which the biofilm carrier is kept in wet soaking mode for 1 hour, and the remaining time is spent running steps 1.3 and 1.5, etc.

[0026] In one embodiment, the duration of the upstream gas supply during the normal operation phase is the same as the duration of the downstream gas supply.

[0027] In one embodiment, the volume ratio of hydrogen to carbon dioxide in the mixed gas is 3:1 to 5:1; the carbon dioxide in the mixed gas serves as the sole carbon source for the microorganisms, and the nutrient solution components do not contain any carbon source.

[0028] Compared with the prior art, the beneficial effects of the present invention are:

[0029] 1. The dry biomethanation mode and the wet soaking mode of the biofilm carrier are operated in an alternating soaking and draining state of the hydrogen-producing methanogen biofilm. Under the soaking state, the nutrient supply of the hydrogen-producing methanogen is fully guaranteed, while under the draining state, the gas-liquid contact area and gas-liquid mass transfer efficiency can be greatly improved, which can significantly improve the carbon dioxide methanation efficiency of the hydrogen-producing methanogen.

[0030] 2. The bidirectional air intake method ensures that the microbial communities at both ends of the device are alternately in the carbon source abundance period, which improves the unidirectional substrate reduction phenomenon of traditional bioreactors, makes the biomass evenly distributed, and further increases the abundance of hydrogenophilic methanogens in the reactor.

[0031] 3. The method described in this invention can achieve efficient bioconversion of carbon dioxide hydrogenation under low cost and mild conditions, providing an effective way for carbon dioxide resource utilization. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of a bidirectional flow hydrogenophilic carbon dioxide methanation device according to the present invention.

[0033] Figure 2 This is a schematic diagram showing the changes in gas composition at the outlet of the methanation unit under different empty bed residence times.

[0034] Figure 3 This is a schematic diagram showing the change in methane content at the outlet of the methanation unit over time after soaking for different empty bed residence times. Detailed Implementation

[0035] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings and examples.

[0036] like Figure 1 As shown, this invention relates to a bidirectional flow hydrogenophilic carbon dioxide methanation device, comprising a chamber divided from top to bottom into a gas phase reaction zone 1, a liquid phase reaction zone 2, and a gas phase diffusion zone 3. The gas phase reaction zone 1 and the liquid phase reaction zone 2 are filled with porous biofilm carriers 4 with good methanogenic capabilities. A microporous plate 12 is disposed between the gas phase diffusion zone 3 and the liquid phase reaction zone 2. An upper sampling port 13 is provided at the upper part of the gas phase reaction zone 1, and a lower sampling port 15 is provided at the lower part.

[0037] In this invention, the chamber is preferably located in an anaerobic constant-temperature environment. To maintain the constant temperature, a temperature control system 16 is installed outside the gas phase reaction zone 1, and the temperature control system 16 regulates the constant temperature conditions between 35-37°C.

[0038] In this invention, the porous biofilm carrier 4 is a carbon-supported sponge particle with adsorption capacity, with a size of approximately 5-10 mm, more preferably 10 mm × 10 mm × 10 mm, and a filling rate of 80-100%. Hydrogen-loving methanogenic bacteria with good activity are attached to its surface and internal pores.

[0039] In this invention, the liquid phase reaction zone 2 and the buffer bottle 7 form a loop. The buffer bottle 7 stores a mixture of sludge and nutrient solution. The loop can be configured to control the flow rate of the mixture so that the porous biofilm carrier 4 in the gas phase reaction zone 1 is in an alternating state of soaking and draining.

[0040] In the drained state, the hydrogen and carbon dioxide mixture is configured in both an upflow and a downflow inlet mode. In the upflow inlet mode, the mixture enters the gas phase reaction zone 1 through the gas phase diffusion zone 3 and the liquid phase reaction zone 2, where it undergoes biotransformation by hydrogenophilic methanogens. The effluent is collected through the upper sampling port 13. The microporous plate 12 forms microbubbles from the gas leaving the gas phase diffusion zone 3, improving gas-liquid mass transfer. In other words, in the upflow inlet mode, the effluent is discharged and collected through the upper sampling port 13. Similarly, in the downflow inlet mode, the mixture enters the gas phase reaction zone 1 through the upper sampling port 13, where it undergoes biotransformation by hydrogenophilic methanogens. The effluent is collected through the lower sampling port 15. The biofilm carrier 4 in a drained state can convert hydrogen and carbon dioxide into methane and water. Furthermore, the gas-liquid contact area and gas-liquid mass transfer efficiency are both improved in this state, thus enhancing the carbon dioxide methanation efficiency of hydrogenophilic methanogens. The drained state can also be referred to as the dry biomethanation mode.

[0041] In the soaking state, the gas supply is stopped, and the biofilm carrier 4 is immersed in the mixed solution to ensure that the microorganisms in the biofilm obtain nutrients, thus guaranteeing sufficient nutrient supply for the hydrogenophilic methanogens and promoting their growth and reproduction. This soaking state can also be referred to as the wet soaking mode of the biofilm carrier.

[0042] In this invention, soaking and draining are performed alternately to enhance gas-liquid mass transfer efficiency. During the cultivation stage under draining conditions, it is preferable to first execute the upflow air intake mode and then the downflow air intake mode. During the normal operation stage under draining conditions, the upflow and downflow air intake modes are alternated, which can eliminate the unidirectional substrate limitation of the bioreactor. Through the bidirectional air intake method, the microbial communities at both ends can be alternately in the carbon source abundance period, avoiding the problem of gradual substrate reduction in traditional bioreactors, so as to achieve uniform biomass distribution, further increase the abundance of hydrogenophilic methanogens in the reactor, and stably maintain the uniform distribution, high abundance and high activity of anaerobic hydrogenophilic methanogens in the device, ultimately achieving efficient bioconversion of carbon dioxide hydrogenation.

[0043] In some embodiments of the present invention, the gas phase diffusion zone 3 occupies 5-10% of the total volume of the chamber, the gas phase reaction zone 1 occupies 65-70% of the total volume of the chamber, and the liquid phase reaction zone 2 occupies 20-30% of the total volume of the chamber. The effective volume of the buffer bottle 7 is approximately 1.2-1.5 times the volume of the gas phase reaction zone 1, and the pressure on the inner surface of the chamber can be set to 0-5 bar.

[0044] In some embodiments of the present invention, a peristaltic pump 5 is provided on the circuit. By adjusting the direction and flow rate of the peristaltic pump 5, the volume of the mixed liquid in the gas phase reaction zone 1 and the circulation of the circuit are controlled. Specifically, the inlet of the liquid phase reaction zone 2 is located at its lower part, and the outlet is located at its upper part. The inlet is connected to the buffer bottle 7 through an inlet pipe 6, and the outlet is connected to the buffer bottle 7 through an outlet pipe 8. The peristaltic pump 5 can be a bidirectional pump, which can control the flow rate and also control the pumping in and out.

[0045] In some embodiments of the present invention, a mass flow controller 9 and a gas path valve 10 are provided on the gas supply pipeline 11 of the mixed gas. The mass flow controller 9 can control the gas supply amount, and the gas path valve 10 can control whether gas is supplied.

[0046] Based on the above-described bidirectional flow hydrogenophilic carbon dioxide methanation apparatus, the corresponding bidirectional flow hydrogenophilic carbon dioxide methanation method of the present invention includes a cultivation stage and a normal operation stage, and throughout the process, the apparatus maintains an anaerobic constant temperature environment, wherein the reaction temperature is 35-37°C.

[0047] The cultivation stage includes:

[0048] Step 1.1: Pump the mixture into the liquid phase reaction zone 2 and the gas phase reaction zone 1 until the biofilm carrier 4 is submerged. The biofilm carrier 4 is continuously immersed in the mixture. Then, drain all the mixture from the gas phase reaction zone 1 to keep the liquid phase reaction zone 2 submerged in the mixture.

[0049] For example, with the peristaltic pump 5, inlet line 6, and outlet line 8 configured as described above, the peristaltic pump 5 is started, pumping the mixture from the buffer bottle 7 through the inlet line 6 into the gas phase reaction zone 1 via the liquid phase reaction zone 2, until the mixture completely submerges the biofilm carrier 4. The peristaltic pump 5 is then turned off. The biofilm carrier 4 remains immersed in the mixture for approximately 30-60 minutes. Then, the peristaltic pump 5 is turned around and then turned on again, pumping all the mixture in the gas phase reaction zone 1 back into the buffer bottle 7. The peristaltic pump 5 is then turned off, while the liquid phase reaction zone 2 remains submerged in the mixture.

[0050] Step 1.1 constitutes the wet immersion mode of the biofilm carrier in the cultivation stage.

[0051] Step 1.2: Adjust the flow rate of the mixture so that the mixture circulates in the circuit.

[0052] For example, when the peristaltic pump 5, the inlet pipe 6 and the outlet pipe 8 are configured as described above, the peristaltic pump 5 is started to pump the mixture from the buffer bottle 7 into the liquid phase reaction zone 2 through the inlet pipe 6, and continuously pump it back into the buffer bottle 7 through the outlet pipe 8, so that the mixture in the entire liquid phase reaction zone 2 is in an anaerobic circulation state during the operation of the device.

[0053] Step 1.3: The mixed gas is fed into the gas phase diffusion zone 3, passes through the liquid phase reaction zone 2 via the microporous plate 12, and finally enters the gas phase reaction zone 1 by an upward flow. The mixed gas is biotransformed by hydrogenophilic methanogens. The gas is collected through the upper sampling port 13, and then the gas supply is stopped.

[0054] For example, when the gas supply line 11, gas valve 10 and mass flow controller 9 are configured as described above, the mixed gas of hydrogen and carbon dioxide is made to flow out of the mass flow controller 9 by adjusting the gas valve 10, and then enter the gas phase diffusion zone 3 through the gas supply line 11. After passing through the microporous plate 12, it passes through the liquid phase reaction zone 2, and finally enters the gas phase reaction zone 1 in an upward flow. The mixed gas is biotransformed by hydrogenophilic methanogens. The gas is collected through the upper sampling port 13, and this transformation mode can be maintained for 1-5 days.

[0055] Steps 1.2 to 1.3 constitute the dry bio-methanation mode of the upflow culture stage.

[0056] Step 1.4: Repeat steps 1.1 to 1.3 until the empty bed in the device has been in contact with the substrate for approximately 30-40 minutes, at which point the upflow culture stage is complete. That is, steps 1.1, 1.2, and 1.3 constitute the upflow culture stage.

[0057] Step 1.5: The mixed gas is fed into the gas phase reaction zone 1 through the upper sampling port 13 and then biotransformed by hydrogenophilic methanogens. The gas produced during the process is collected through the lower sampling port 15, and then the gas supply is stopped.

[0058] For example, when the gas supply line 11, gas valve 10 and mass flow controller 9 are configured as described above, the gas valve 10 is adjusted so that the mixed gas of hydrogen and carbon dioxide flows out from the mass flow controller 9 and directly enters the gas phase reaction zone 1 in a downflow manner through the upper sampling port 13. The mixed gas is bioconverted by hydrogen-loving methanogens, and the gas produced during the process is collected through the lower sampling port 15. This conversion mode can be maintained for 1-5 days.

[0059] Steps 1.2 to 1.5 constitute the dry bio-methanation mode of the downflow culture stage.

[0060] Step 1.6: Repeat steps 1.1, 1.2, and 1.5 until the empty bed residence time reaches 10-20 minutes, completing the downflow culture stage. The entire culture stage ends, and the normal operation stage begins. That is, steps 1.1, 1.2, and 1.5 constitute the downflow culture stage.

[0061] In this invention, after the upflow culture stage is completed, the downflow culture stage begins. 72±2 hours is one soaking cycle of either the upflow or downflow culture stage. Within one soaking cycle, the biofilm carrier is kept in wet soaking mode for 1 hour, and the remaining time is in dry biomethanation mode.

[0062] The normal operation phase is a cycle of steps 1.1, 1.2, 1.3, and 1.5. Specifically, it can be described as follows:

[0063] Step 2.1: Close the gas valve 10, start the peristaltic pump 5, and pump the mixture into the gas phase reaction zone 1 from the buffer bottle 7 through the inlet pipe 6 until the mixture submerges all the biofilm carriers 4. Then, turn off the peristaltic pump 5. The biofilm carriers 4 continue to soak in the mixture. After about 30-60 minutes, turn the peristaltic pump 5 back to the buffer bottle 7 to pump all the mixture in the gas phase reaction zone 1 back to the buffer bottle 7. Finally, turn off the peristaltic pump 5.

[0064] Step 2.2: Start the peristaltic pump 5 to pump the mixture from the buffer bottle 7 into the liquid phase reaction zone 2 through the inlet pipe 6, and continuously pump it back into the buffer bottle through the outlet pipe 8, so that the mixture in the entire liquid phase reaction zone 2 is in a state of circulation during the operation of the device.

[0065] Step 2.3: Under anaerobic constant temperature environment, adjust the gas path valve 10 so that the mixed gas of hydrogen and carbon dioxide flows out from the mass flow controller 9 and enters the gas phase diffusion zone 3 through the gas supply pipeline 11. After passing through the microporous plate 12 and the liquid phase reaction zone 2, it finally enters the gas phase reaction zone 1 in an upward flow. The mixed gas is biotransformed by hydrogen-loving methanogenic bacteria. The gas is collected through the upper sampling port 13. This transformation mode can be maintained for 1-3 days.

[0066] Step 2.4: Adjust the gas path valve 10 so that the hydrogen and carbon dioxide mixed gas flows out from the mass flow controller 9 and directly enters the gas phase reaction zone 1 in a downflow manner through the upper sampling port 13. The mixed gas is bioconverted by hydrogen-loving methanogenic bacteria. The gas produced during the process is collected through the lower sampling port 15. This conversion mode can be maintained for 1-3 days and can be the same as the upflow gas supply time.

[0067] Step 2.5, repeat steps 2.1 through 2.4.

[0068] In the normal operation phase of this invention, one soaking cycle is 96±2 hours. Within one soaking cycle, the wet soaking mode of the biofilm carrier is maintained for 1 hour. During the remaining time, the upstream dry biomethanation mode and the downstream dry biomethanation mode operate for the same amount of time.

[0069] In this invention, carbon dioxide in the mixed gas serves as the sole carbon source for the microorganisms, and the nutrient solution components do not contain any carbon source. For example, the microbial nutrient solution of this invention is prepared by diluting five nutrient stock solutions (A (10 mL / L), B (2 mL / L), C (1 mL / L), D (5 mL / L), and E (5 mL / L) with 4.2 g / L NaHCO3, as shown in the specific formula below:

[0070] The microbial nutrient solution is prepared by diluting five nutrient stock solutions (A (10 mL / L), B (2 mL / L), C (1 mL / L), D (5 mL / L), and E (5 mL / L) with 4.2 g / L NaHCO3. The specific formula is as follows:

[0071]

[0072] Each component in the nutrient stock solution is added one by one according to the concentration specified in the specific formula.

[0073] In one specific embodiment of the present invention, the total volume of the chamber is approximately 3.3 L, the gas phase diffusion zone 3 occupies 5% of the total volume, approximately 0.17 L, the gas phase reaction zone 1 occupies 65% of the total volume, approximately 2.15 L, and the liquid phase reaction zone 2 occupies 30% of the total volume, approximately 1.00 L. The porous biofilm carrier 14 is 100% filled, and the temperature is 35°C. The internal pressure of the chamber is 0 bar.

[0074] Using the above-mentioned nutrient solution, the dry bio-methanation mode was maintained for 3 days in both the upflow and downflow culture stages, and the wet immersion mode of the biofilm carrier was maintained for 60 minutes. In the normal operation stage, the dry bio-methanation mode in both the upflow and downflow stages was maintained for 2 days each, and the wet immersion mode of the biofilm carrier was maintained for 60 minutes.

[0075] During the upflow and downflow culture stages, a soaking cycle was set at 72 hours, with the dry bio-methanation mode maintained for 71 hours and the biofilm carrier wet soaking mode maintained for 1 hour. During the normal operation stage, a soaking cycle was set at 96 hours, with the dry conversion mode of both the upflow and downflow stages maintained for 47.5 hours and the biofilm carrier wet soaking mode maintained for 1 hour.

[0076] The method of this invention was used for the bioconversion of a hydrogen-carbon dioxide mixture with a volume ratio of 4:1. Results showed that the carbon dioxide conversion efficiency remained above 95%. Figure 2 and Figure 3 As shown.

[0077] In summary, this invention improves gas-liquid mass transfer efficiency by placing the biofilm carrier in a static state and an alternating wet and dry environment. The bidirectional air inlet method improves the problems of gradual decrease in microbial abundance and uneven biomass distribution in traditional bioreactors, and can improve biomass and carbon dioxide conversion efficiency under low cost conditions, providing an effective way for carbon dioxide resource utilization.

[0078] For those skilled in the art, based on the above principles, several changes and improvements can be made to the method of the present invention, and these changes and improvements should also be included within the scope of protection of the present invention.

Claims

1. A method for bidirectional flow hydrogenophilic carbon dioxide methanation, implemented using a bidirectional flow hydrogenophilic carbon dioxide methanation apparatus, the apparatus comprising a chamber, the chamber being divided from top to bottom into a gas phase reaction zone (1), a liquid phase reaction zone (2), and a gas phase diffusion zone (3), wherein the gas phase reaction zone (1) and the liquid phase reaction zone (2) are filled with a porous biofilm carrier (4), wherein active hydrogenophilic methanogenic bacteria are attached to the surface and internal pores of the porous biofilm carrier (4), and a microporous plate (12) is provided between the gas phase diffusion zone (3) and the liquid phase reaction zone (2) to form microbubbles from the gas leaving the gas phase diffusion zone (3); an upper sampling port (13) is provided at the upper part of the gas phase reaction zone (1), and a lower sampling port (15) is provided at the lower part. The liquid phase reaction zone (2) and the buffer bottle (7) form a loop. The buffer bottle (7) stores a mixture of sludge and nutrient solution. The loop is configured to control the flow rate of the mixture so that the porous biofilm carrier (4) in the gas phase reaction zone (1) is in an alternating soaking and draining state. A peristaltic pump (5) is installed on the loop. By adjusting the direction and flow rate of the peristaltic pump (5), the volume of the mixture in the gas phase reaction zone (1) and the circulation of the loop are controlled. In the drained state, the mixed gas of hydrogen and carbon dioxide is configured in an upflow inlet mode and a downflow inlet mode. In the upflow inlet mode, the mixed gas enters the gas phase reaction zone (1) through the gas phase diffusion zone (3) and the liquid phase reaction zone (2), where it is biotransformed by hydrogen-producing methanogens, and the gas is discharged and collected through the upper sampling port (13). In the downflow inlet mode, the mixed gas enters the gas phase reaction zone (1) through the upper sampling port (13), where it is biotransformed by hydrogen-producing methanogens, and the gas is discharged and collected through the lower sampling port (15). The carbon dioxide in the mixed gas serves as the sole carbon source for the microorganisms, and the nutrient solution components do not contain any carbon source. characterized in that The method includes a cultivation phase and a normal operation phase; The cultivation phase includes: Step 1.1: Pump the mixture into the liquid phase reaction zone (2) and the gas phase reaction zone (1) until the biofilm carrier (4) is submerged. The biofilm carrier (4) is continuously soaked in the mixture. Then, drain all the mixture from the gas phase reaction zone (1) to keep the liquid phase reaction zone (2) submerged in the mixture. Step 1.2: Adjust the flow rate of the mixture so that the mixture circulates in the loop; Step 1.3: The mixed gas is sent into the gas phase diffusion zone (3), passes through the liquid phase reaction zone (2) via the microporous plate (12), and finally enters the gas phase reaction zone (1) by upflow. The mixed gas is biotransformed by hydrogen-loving methanogens. The gas is collected through the upper sampling port (13), and then the gas supply is stopped. Step 1.4, repeat steps 1.1 to 1.3, and after the biofilm on the porous biofilm carrier (4) has achieved the required hydrogenophilic carbon dioxide methanation effect, the upflow culture stage is completed; wherein, the empty bed residence time of the device reaches 30-40 min; Step 1.5: The mixed gas is fed into the gas phase reaction zone (1) through the upper sampling port (13) by flow metering. The mixed gas is biotransformed by hydrogen-loving methanogens. The gas produced during the process is collected through the lower sampling port (15), and then the gas supply is stopped. Step 1.6, repeat steps 1.1, 1.2 and 1.5 until efficient hydrogenophilic carbon dioxide methanation can be achieved, that is, the carbon dioxide conversion efficiency can be stably maintained at 80%-90%, then complete the downflow culture stage, in which the empty bed residence time of the device reaches 10-20 min; The normal operation phase includes: The cycle of steps 1.1, 1.2, 1.3 and 1.5 involves the biofilm in a static, draining state converting hydrogen and carbon dioxide into methane and water until the carbon dioxide conversion efficiency is stably maintained at over 95%. Wherein, step 1.1 is a wet immersion mode of biofilm carrier, and steps 1.2 to 1.3 and step 1.5 are all dry biomethanation modes; steps 1.1, 1.2 and 1.3 constitute the upflow culture stage, and steps 1.1, 1.2 and 1.5 constitute the downflow culture stage; In the upstream and downstream culture stages, each soaking cycle lasts 72±2 hours, during which the biofilm carrier is kept in wet soaking mode for 1 hour, and the remaining time is in dry biomethanation mode. In the normal operation stage, each soaking cycle lasts 96±2 hours, during which the biofilm carrier is kept in wet soaking mode for 1 hour, and the remaining time is used for steps 1.3 and 1.

5.

2. The process for the methanation of carbon dioxide according to claim 1, wherein, During the cultivation and normal operation phases, the device maintains an anaerobic constant temperature environment with a reaction temperature of 35-37°C and a chamber pressure of 0-5 bar.

3. The method for bidirectional flow hydrogenophilic carbon dioxide methanation according to claim 1, characterized in that, In step 1.1, the biofilm carrier (4) is continuously soaked in the mixed solution for 30-60 minutes; in step 1.3, during the upflow culture stage, the dry biomethanation mode is maintained for 1-5 days, and during the normal operation stage, the upflow dry biomethanation mode is maintained for 1-3 days; in step 1.5, during the downflow culture stage, the dry biomethanation mode is maintained for 1-5 days, and during the normal operation stage, the downflow dry biomethanation mode is maintained for 1-3 days.

4. The process for the methanation of carbon dioxide according to claim 1, wherein, The duration of the upstream gas supply during the normal operation phase is the same as the duration of the downstream gas supply.

5. The process for the methanation of carbon dioxide according to claim 1, wherein, The volume ratio of hydrogen to carbon dioxide in the mixed gas is 3:1 to 5:

1.

6. The method for bidirectional flow hydrogenophilic carbon dioxide methanation according to claim 1, characterized in that, The porous biofilm carrier (4) is a carbon-supported sponge particle with adsorption capacity, and the filling rate is 80-100%.

7. The process for the methanation of carbon dioxide according to claim 1, wherein, The gas phase diffusion zone (3) occupies 5-10% of the total volume of the chamber, the gas phase reaction zone (1) occupies 65-70% of the total volume of the chamber, and the liquid phase reaction zone (2) occupies 20-30% of the total volume of the chamber.

8. The method for bidirectional flow hydrogenophilic carbon dioxide methanation according to claim 1, characterized in that, A mass flow controller (9) and a gas valve (10) are installed on the gas supply pipeline (11) of the mixed gas.

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