A tidal carbon dioxide biomethanation device and method

Abstract

A tidal carbon dioxide efficient biological methanogenesis device and method, mainly including a gas diffusion zone, a liquid phase reaction zone and a gas phase reaction zone; a microporous aerator is arranged between the gas diffusion zone and the liquid phase reaction zone, and a porous plate is arranged between the liquid phase reaction zone and the gas phase reaction zone. Granular anaerobic biofilm and biofilm carrier with good carbon dioxide methanogenesis activity are respectively filled in the liquid phase reaction zone and the gas phase reaction zone. Under the tidal operation mode, the granular anaerobic biofilm is always immersed in the nutrient solution and is in an expanded or fluidized state, while the biofilm carrier is in a static state and a dry-wet alternating environment. Carbon dioxide and hydrogen are converted by the granular anaerobic biofilm and the biofilm carrier in turn, and finally high-grade methane is generated. The present invention can improve the active biomass and gas-liquid mass transfer efficiency under low-cost conditions, realize CO2 efficient biological methanogenesis, and provide an effective way for CO2 resource utilization.

Description

Technical Field

[0001] The present invention belongs to the technical field of environmental protection, relates to the resource application of carbon dioxide, and in particular to a tidal carbon dioxide biomethanation device and method. Background Art

[0002] The main methods for CO2 conversion include hydrogenation conversion, electrochemical conversion, photochemical conversion, and biological conversion. The first three are pure chemical catalytic processes with high conversion rates, but they have high requirements for catalysts and are currently facing problems such as poor selectivity and high operating costs. Bioconversion uses enzymes in microorganisms as catalysts and can achieve high selectivity in CO2 conversion under mild conditions. The products of CO2 bioconversion mainly include energy substances or chemicals such as methane, acids, and alcohols. Among them, methane as the target product has the advantages of easy product separation and high applicability.

[0003] The most studied CO2 biomethanation devices at present include CSTR, fixed bed, trickle bed and membrane reactor. However, due to the limitation of gas-liquid mass transfer, these devices all face the problem of low CO2 conversion efficiency. Summary of the invention

[0004] In order to overcome the shortcomings of the above-mentioned prior art, the purpose of the present invention is to provide a tidal carbon dioxide biomethanation device and method, which can further increase the gas-liquid contact area, improve the gas-liquid mass transfer efficiency, and achieve efficient CO2 biomethanation.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is:

[0006] A tidal carbon dioxide biomethanation device comprises a gas diffusion zone, a liquid phase reaction zone and a gas phase reaction zone which are sequentially distributed from bottom to top, a microporous aerator is arranged between the gas diffusion zone and the liquid phase reaction zone, a porous plate is arranged between the liquid phase reaction zone and the gas phase reaction zone, and the gas diffusion zone is connected to an air inlet with an air inlet valve; the liquid phase reaction zone is filled with a nutrient solution and loaded with a granular anaerobic biofilm, during the operation of the device, the granular anaerobic biofilm is always immersed in the nutrient solution and is in an expanded or fluidized state; the gas phase reaction zone is filled with a biofilm carrier, during the working interval of the device, the biofilm carrier is immersed in the nutrient solution so that the microorganisms in the biofilm can obtain nutrient elements and promote the growth and reproduction of the microorganisms, and during the operation of the device, the biofilm carrier is not immersed in the nutrient solution and is in a static state.

[0007] Preferably, the upper part of the liquid phase reaction zone is connected to the bottom of the nutrient solution tank through pipeline 1 with a water pump; the top of the gas phase reaction zone is connected to the top of the nutrient solution tank through pipeline 2; an air outlet is provided at the top of the nutrient solution tank; and an air outlet valve is provided at the air outlet.

[0008] Preferably, the gas diffusion zone occupies 5%-10% of the total volume of the device, the liquid phase reaction zone occupies 20%-40% of the total volume of the device, and the gas phase reaction zone occupies 50%-75% of the total volume of the device.

[0009] Preferably, the effective volume of the nutrient solution tank is 1.2-1.5 times the volume of the gas phase reaction zone.

[0010] Preferably, the nutrient solution filling rate in the liquid phase reaction zone is 70%-90%.

[0011] Preferably, the granular anaerobic biofilm is anaerobic granular sludge formed by self-fixation or an anaerobic biofilm attached and grown on a granular carrier.

[0012] Preferably, the filling rate of the biofilm carriers in the gas phase reaction zone is 80%-100%.

[0013] The present invention also provides a tidal carbon dioxide biomethanation method based on the tidal carbon dioxide biomethanation device, comprising the following steps:

[0014] Step 1: in an anaerobic environment, a granular anaerobic biofilm and a biofilm carrier having carbon dioxide methanogenic activity are respectively loaded into a liquid phase reaction zone and a gas phase reaction zone, and a nutrient solution is pumped into the liquid phase reaction zone until the liquid level rises to the porous plate;

[0015] Step 2: Carbon dioxide and hydrogen enter the gas diffusion zone from the air inlet at a volume ratio of 0.2-0.3, and enter the liquid phase reaction zone and the gas phase reaction zone in turn through the microporous aerator, and the granular anaerobic biofilm and the biofilm carrier convert CO2 and H2 to generate methane;

[0016] Step 3: After the device has been running continuously for 5-30 days, the air inlet valve is closed, and the nutrient solution is pumped into the liquid phase reaction zone again until the nutrient solution in the gas phase reaction zone submerges all the biofilm carriers, and the biofilm carriers are continuously immersed in the nutrient solution for 5-30 minutes;

[0017] Step 4: Pump out the nutrient solution until the liquid level in the device drops to the porous plate, wait for 30-60 minutes, and then open the air inlet valve;

[0018] Step 5: Repeat steps 2 to 4.

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

[0020] 1. The present invention adopts a tidal operation mode to put the biofilm carrier with CO2 methanogenesis activity in a dry-wet alternating state. On the one hand, it increases the gas-liquid contact area and improves the gas-liquid mass transfer efficiency. On the other hand, it fully guarantees the nutrient supply of microorganisms and can greatly improve the CO2 biomethanization efficiency.

[0021] 2. The present invention simultaneously utilizes the high biomass characteristics of granular anaerobic biofilm to simultaneously achieve efficient bioconversion of intermediate metabolites such as CO2 and acetic acid.

[0022] 3. The device and method described in the present invention can realize efficient biomethanization of CO2 at low cost, providing an effective way for CO2 resource utilization. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic diagram of the structure of the present invention. DETAILED DESCRIPTION

[0024] The embodiments of the present invention are described in detail below with reference to the accompanying drawings and examples.

[0025] like Figure 1 As shown, the present invention is a tidal carbon dioxide biomethanization device, comprising a gas diffusion zone 1, a liquid phase reaction zone 2 and a gas phase reaction zone 3 which are sequentially distributed from bottom to top. The gas diffusion zone 1, the liquid phase reaction zone 2 and the gas phase reaction zone 3 can be arranged in a cylindrical, square or other container. For example, the gas diffusion zone 1 occupies 5%-10% of the total volume of the device, the liquid phase reaction zone 2 occupies 20%-40% of the total volume of the device, and the gas phase reaction zone 3 occupies 50%-75% of the total volume of the device. In a specific embodiment of the present invention, the total volume of the device is 60L, the gas diffusion zone 1 occupies 5% of the total volume of the device, i.e. 3L; the liquid phase reaction zone 2 occupies 5% of the total volume of the device, i.e. 15L; the gas phase reaction zone 3 occupies 70% of the total volume of the device, i.e. 42L.

[0026] The gas diffusion zone 1 is connected to an air inlet 4 with an air inlet valve 13 . A microporous aerator 5 is arranged between the gas diffusion zone 1 and the liquid phase reaction zone 2 . A porous plate 7 is arranged between the liquid phase reaction zone 2 and the gas phase reaction zone 3 .

[0027] The gas inlet 4 may be arranged on the side wall of the gas diffusion zone 1 to feed a mixed gas of carbon dioxide and hydrogen into the gas diffusion zone 1 , where the mixed gas can be fully diffused.

[0028] The microporous aerator 5 may be circular or square in shape, and the average diameter of the micropores is 2-5 microns. The function of the microporous aerator 5 is to form tiny bubbles into the gas entering the liquid phase reaction zone 2, thereby increasing the gas-liquid mass transfer area.

[0029] The porous plate 7 may be circular or square in shape, with a pore size of 10 mm, and its function is to intercept the biofilm carriers 8 filled in the gas phase reaction zone 3 .

[0030] The liquid phase reaction zone 2 is filled with nutrient solution and loaded with granular anaerobic biofilm 6. The nutrient solution contains a variety of nutrient elements required for the growth of anaerobic microorganisms, and its filling rate is 70%-90%. In this embodiment, 80% is selected, and the corresponding nutrient solution volume is 12L. For example, a feasible specific formula of the nutrient solution is as follows:

[0031] Each liter of nutrient solution is diluted by five nutrient solutions: A (10 mL), B (2 mL), C (1 mL), D (1 mL), and E (5 mL). The components of the five nutrient solutions A (main inorganic salts), B (phosphates), C (sulfates), D (trace elements), and E (vitamins) are shown in the following table:

[0032]

[0033] During the operation of the device, the granular anaerobic biofilm 6 should always be immersed in the nutrient solution and in an expanded or fluidized state. The granular anaerobic biofilm 6 has good carbon dioxide methanogenic activity, and can be, for example, anaerobic granular sludge formed by self-fixation or anaerobic biofilm attached to and grown on a granular carrier.

[0034] The gas phase reaction zone 3 is filled with biofilm carriers 8, and the filling rate thereof is 80%-100% by way of example, and 100% is selected in this embodiment. During the operation of the device, the biofilm carriers 8 are not immersed in the nutrient solution and are in a static state. During the working interval of the device, the biofilm carriers 8 are immersed in the nutrient solution so that the microorganisms in the biofilm can obtain nutrient elements, thereby promoting the growth and reproduction of the microorganisms.

[0035] Carbon dioxide and hydrogen are successively converted by the granular anaerobic biofilm 6 and the biofilm carrier 8, and finally high-grade methane is generated. The biofilm carrier 8 has good carbon dioxide methanogenic activity, and can be a carbon sponge particle with a size of 2-4 cm.

[0036] Based on the above device, the tidal carbon dioxide biomethanation method of the present invention comprises the following steps:

[0037] Step 1: In an anaerobic environment, a granular anaerobic biofilm 6 and a biofilm carrier 8 having carbon dioxide methanogenic activity are respectively loaded into the liquid phase reaction zone 2 and the gas phase reaction zone 3, and a nutrient solution is pumped into the liquid phase reaction zone 2 until the liquid level rises to the porous plate 7;

[0038] Step 2: Carbon dioxide and hydrogen enter the gas diffusion zone 1 from the air inlet 4 at a volume ratio of 0.2-0.3, and enter the liquid phase reaction zone 2 and the gas phase reaction zone 3 in turn through the microporous aerator 5, and the granular anaerobic biofilm 6 and the biofilm carrier 8 convert CO2 and H2 to generate methane;

[0039] Step 3: After the device has been running continuously for 5-30 days, the air inlet valve 13 is closed, and the nutrient solution is pumped into the liquid phase reaction zone 2 again until the nutrient solution in the gas phase reaction zone 3 submerges all the biofilm carriers 8, and the biofilm carriers 8 are continuously immersed in the nutrient solution for 5-30 minutes;

[0040] Step 4: Pump out the nutrient solution until the liquid level in the device drops to the porous plate 7, wait for 30-60 minutes, and then open the air inlet valve 13;

[0041] Step 5: Repeat steps 2 to 4.

[0042] In a specific embodiment of the present invention, the upper part of the liquid phase reaction zone 2 is connected to the bottom of the nutrient solution tank 10 through a pipeline 1 9 with a water pump 11; the top of the gas phase reaction zone 3 is connected to the top of the nutrient solution tank 10 through a pipeline 2 9; the top of the nutrient solution tank 10 is provided with an air outlet 12; the air outlet 12 is provided with an air outlet valve 14. For example, the effective volume of the nutrient solution tank 10 is 1.2-1.5 times the volume of the gas phase reaction zone 3, and 1.25 times is selected in this embodiment, corresponding to a volume of 52.5L.

[0043] At this time, the tidal carbon dioxide efficient biological methanogenesis method of the present invention comprises the following steps:

[0044] Step 1: In an anaerobic environment, a granular anaerobic biofilm 6 and a biofilm carrier 8 with good carbon dioxide methanogenesis activity are respectively loaded into the liquid phase reaction zone 2 and the gas phase reaction zone 3, and a water pump 11 is started to pump nutrient solution from the nutrient solution tank 10 into the liquid phase reaction zone 2 until the liquid level in the device rises to the porous plate 7, and then the water pump 11 is turned off;

[0045] Step 2: Carbon dioxide and hydrogen enter the gas diffusion zone 1 from the air inlet 4 at a ratio of 0.25, and enter the liquid phase reaction zone 2 and the gas phase reaction zone 3 in turn through the microporous aerator 5. The granular anaerobic biofilm 6 and the biofilm carrier 8 convert CO2 and H2 to generate methane, which enters the nutrient solution tank 10 through the pipeline 1, and finally the methane is discharged from the air outlet 12 and collected by the air bag;

[0046] Step 3: After the device has been running continuously for 15 days, close the air inlet valve 13 and the air outlet valve 14, start the water pump, and pump the nutrient solution from the nutrient solution tank 10 into the liquid phase reaction zone 2 until the nutrient solution in the gas phase reaction zone 3 submerges all the biofilm carriers 8, then close the water pump 11, and allow the biofilm carriers 8 to continue to soak in the nutrient solution for 5 minutes;

[0047] Step 4, reverse start the water pump 11, pump the nutrient solution from the liquid phase reaction zone 2 to the nutrient solution tank 10, until the liquid level in the device drops to the porous plate 7, turn off the water pump 11, wait for 30 minutes, and then open the air inlet valve 13 and the air outlet valve 14.

[0048] Step 5: Repeat steps 2 to 4.

[0049] The device and method of the present invention were used to carry out a three-month biomethanization experiment on CO2. The results showed that when the treatment flow rate was 1m 3 / d conditions, the methane content in the product gas is maintained above 95%, and the purity meets the requirements for gas utilization.

[0050] 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 in the protection scope of the present invention.

Claims

1. A tidal carbon dioxide biomethanation device, characterized in that: The device comprises a gas diffusion zone (1), a liquid phase reaction zone (2) and a gas phase reaction zone (3) which are sequentially arranged from bottom to top; a microporous aerator (5) is arranged between the gas diffusion zone (1) and the liquid phase reaction zone (2); a porous plate (7) is arranged between the liquid phase reaction zone (2) and the gas phase reaction zone (3); the gas diffusion zone (1) is connected to an air inlet (4) with an air inlet valve (13); the liquid phase reaction zone (2) is filled with a nutrient solution and a granular anaerobic biofilm (6); during the operation of the device, the granular anaerobic biofilm (6) is always immersed in the nutrient solution and is in an expanded or fluidized state; the gas phase reaction zone (3) is filled with a biofilm carrier (8); during the working interval of the device, the biofilm carrier (8) is immersed in the nutrient solution so that the microorganisms in the biofilm obtain nutrient elements; during the operation of the device, the biofilm carrier (8) is not immersed in the nutrient solution and is in a static state; The upper part of the liquid phase reaction zone (2) is connected to the bottom of the nutrient solution tank (10) via a pipeline (9) with a water pump (11); the top of the gas phase reaction zone (3) is connected to the top of the nutrient solution tank (10) via a pipeline (9); the top of the nutrient solution tank (10) is provided with an air outlet (12); the air outlet (12) is provided with an air outlet valve (14); The gas diffusion zone (1) occupies 5%-10% of the total volume of the device, the liquid phase reaction zone (2) occupies 20%-40% of the total volume of the device, and the gas phase reaction zone (3) occupies 50%-75% of the total volume of the device; The filling rate of the nutrient solution in the liquid phase reaction zone (2) is 70%-90%, and the filling rate of the biofilm carrier (8) in the gas phase reaction zone (3) is 80%-100%.

2. The tidal carbon dioxide biomethanation device according to claim 1, characterized in that: The effective volume of the nutrient solution tank (10) is 1.2-1.5 times the volume of the gas phase reaction zone (3).

3. The tidal carbon dioxide biomethanation device according to claim 1, characterized in that: The granular anaerobic biofilm (6) is an anaerobic granular sludge formed by self-fixation or an anaerobic biofilm attached and grown on a granular carrier.

4. A tidal carbon dioxide biomethanation method based on the tidal carbon dioxide biomethanation device according to claim 1, characterized in that: The following steps are involved: Step 1: In an anaerobic environment, a granular anaerobic biofilm (6) having carbon dioxide methanogenic activity and a biofilm carrier (8) are respectively loaded into a liquid phase reaction zone (2) and a gas phase reaction zone (3), and a nutrient solution is pumped into the liquid phase reaction zone (2) until the liquid level rises to the porous plate (7); Step 2: Carbon dioxide and hydrogen enter the gas diffusion zone (1) from the air inlet (4) at a volume ratio of 0.2-0.3, and enter the liquid phase reaction zone (2) and the gas phase reaction zone (3) in sequence through the microporous aerator (5), and the granular anaerobic biofilm (6) and the biofilm carrier (8) convert CO2 and H2 to generate methane; Step 3: After the device has been running continuously for 5-30 days, the air inlet valve (13) is closed, and the nutrient solution is pumped into the liquid phase reaction zone (2) again until the nutrient solution in the gas phase reaction zone (3) submerges all the biofilm carriers (8), and the biofilm carriers (8) are continuously immersed in the nutrient solution for 5-30 minutes; Step 4: Pump out the nutrient solution until the liquid level in the device drops to the porous plate (7), wait for 30-60 minutes, and then open the air inlet valve (13); Step 5: Repeat steps 2 to 4.

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