A system and method for anaerobic digestion of a biomass synthesis gas to produce methane

Abstract

The application discloses a biomass synthesis gas anaerobic digestion methanogenesis system, which comprises an inlet flow controller, a high-temperature reaction device, a medium-temperature reaction device and a fermentation liquid transmission device. The inlet flow controller is connected with the bottom of the high-temperature reaction device through a pipeline, so that the metered biomass synthesis gas can be transported to the high-temperature reaction device. The top of the high-temperature reaction device is connected with the bottom of the medium-temperature reaction device through a pipeline, so that the gas fermented at a temperature of 45-65 DEG C can be transported to the medium-temperature reaction device. The side of the high-temperature reaction device, the fermentation liquid transmission device and the side of the medium-temperature reaction device are sequentially connected through pipelines, so that the organic acid fermented can be transported to the medium-temperature reaction device. The medium-temperature reaction device is used for secondary fermentation of the gas transported by the high-temperature reaction device at 25-40 DEG C and decomposition of the organic acid. The system can ferment the biomass synthesis gas to obtain gas with high methane yield and raw material utilization rate. The application further discloses a biomass synthesis gas anaerobic digestion methanogenesis method.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of biomass energy, and particularly relates to a system and method for producing methane by anaerobic digestion of biomass synthesis gas. BACKGROUND

[0002] Biomass energy, as an important part of renewable energy, plays an important role in accelerating the transformation of energy structure to low carbon and green. In addition to traditional utilization methods such as gasification, pyrolysis and combustion, converting synthesis gas after gasification or pyrolysis of biomass raw materials into methane through anaerobic fermentation is one of the effective ways to realize high value-added utilization of biomass, especially lignin and cellulose biomass. Compared with direct fermentation technology of biomass, the conversion of recalcitrant biomass into small molecule gas that can be easily digested by microorganisms through thermalization process can effectively avoid the rate-limiting problem in the hydrolysis process of biomass raw materials. Compared with chemical synthesis method, the anaerobic digestion of biomass synthesis gas to produce methane has the advantages of mild reaction conditions, simple reaction process, wide source of raw materials, less limiting conditions, high selectivity in reaction process, etc.

[0003] A method for improving the effect of directional hydrolysis acidification of mixed anaerobic digestion of urban organic waste is disclosed in Chinese patent CN103074382B. Different urban organic biomass raw materials are mixed in a certain proportion, and anaerobic sludge is inoculated in a certain proportion. The anaerobic digestion acidification hydrolysis treatment is carried out at an organic loading of 30-60 TS / L, i.e. 25.8-51.6 gVS / L, and a temperature of 35-55℃. The pH value is controlled in the range of 4.60-6.20. The content of organic acid in the product is significantly higher than that of the control group. The acid composition is directional control, mainly ethanol and acetic acid. The method is simple and easy to operate. Different raw materials are treated by anaerobic acidification technology at the same time. The appropriate proportioning of different raw materials helps to balance the elements in the system, so that the total organic acid yield is 72-216% higher than that without directional acidification. Ethanol and acetic acid account for 98% of the total acid, which can provide high-quality raw materials for organic acid production, directional control of organic acid, or subsequent methanation treatment of two-phase anaerobic digestion. The method disclosed in the patent produces a large amount of organic acid, but the production of methane is inhibited due to the large amount of organic acid, so the methane production is low.

[0004] A method for producing high-grade fuel gas based on biomass gasification-anaerobic digestion is disclosed in Chinese Patent Publication No. CN104830911B, which belongs to the field of environmental protection and renewable energy utilization. The steps are as follows: (1) Establish a regional biomass comprehensive utilization park, and build a biomass gasification system and a biomass anaerobic digestion system, respectively; (2) Gasify the collected difficult biodegradable biomass to produce synthesis gas, and anaerobically digest the collected biodegradable biomass to produce biogas; (3) Introduce the synthesis gas into the anaerobic digestion system to achieve biological methanation of the synthesis gas and purification of the biogas using the excess hydrogen in the synthesis gas, and finally produce high-grade fuel gas. The present invention integrates difficult biodegradable and biodegradable biomass into a high-grade fuel gas production system, effectively realizing regional comprehensive utilization of biomass, and the fermentation temperature of the single-phase anaerobic reactor of the biogas is 35°C. The present invention provides that under the condition of 35°C temperature, the rate of methane production by microbial community is slow, and the yield of methane is low.

[0005] Therefore, it is necessary to design an efficient biomass synthesis gas anaerobic digestion methane production system and method. SUMMARY

[0006] The present invention provides a biomass synthesis gas anaerobic digestion methane production system, which can ferment biomass synthesis gas to produce gas with high methane yield and raw material utilization rate.

[0007] A biomass synthesis gas anaerobic digestion methane production system, comprising:

[0008] An inlet gas flow controller connected to the bottom of the high-temperature reaction device through a pipeline to deliver the metered biomass synthesis gas to the high-temperature reaction device;

[0009] A high-temperature reaction device, the top of which is connected to the bottom of the medium-temperature reaction device through a pipeline to deliver the gas produced by fermentation at a temperature of 45-65°C to the medium-temperature reaction device, and the side of the high-temperature reaction device, the fermentation liquid delivery device and the side of the medium-temperature reaction device are sequentially connected through a pipeline to deliver the organic acid produced by fermentation to the medium-temperature reaction device;

[0010] A medium-temperature reaction device for secondary fermentation of the gas delivered by the high-temperature reaction device and decomposition of organic acid at 25-40°C.

[0011] It also includes a first gas circulating pump, one end of which is connected to the top of the high-temperature reaction device, and the other end is connected to the bottom of the high-temperature reaction device, to circulate the gas at the top of the high-temperature reaction device to the bottom of the high-temperature reaction device.

[0012] It also includes a first aeration device, which is located in the liquid phase of the high-temperature reaction device and connected to the first gas circulation pump, for dispersing gas into the liquid phase.

[0013] It also includes a second gas circulation pump, one end of which is connected to the top of the intermediate temperature reaction device and the other end of which is connected to the bottom of the intermediate temperature reaction device, so as to circulate the gas from the top of the intermediate temperature reaction device to the bottom of the intermediate temperature reaction device.

[0014] It also includes a second aeration device, which is located in the liquid phase of the mesothermal reaction device and connected to the second gas circulation pump, for dispersing gas into the liquid phase.

[0015] The high-temperature reaction apparatus includes:

[0016] A high-temperature reaction chamber is provided, the bottom of which is connected to the air inlet flow controller via a pipeline, and the top of which is connected to the bottom of the medium-temperature reaction device via a first exhaust pipeline. The first exhaust pipeline is provided with a first gas phase sampling port and a first gas phase control port. The high-temperature reaction chamber is located inside a first heating jacket. The side of the high-temperature reaction chamber is provided with a first liquid discharge and sludge discharge outlet and a first liquid phase sampling port, and is connected to the fermentation broth transmission device via a pipeline. A liquid phase sample is obtained through the first liquid phase sampling port. The first liquid discharge and sludge discharge outlet, the first heating jacket, and the first gas phase control port are respectively connected to a first PLC integrated control system.

[0017] The first liquid replenishment module has one end inserted into the high-temperature reaction chamber to replenish the culture medium, and the other end of the first liquid replenishment module is connected to the first PLC integrated control system.

[0018] The first monitoring module is located inside the high-temperature reaction chamber and provides monitoring information to the first PLC integrated control system. The first monitoring module includes a pressure sensor, a pH electrode, a temperature electrode, a liquid level sensor, and a dissolved oxygen electrode.

[0019] The first PLC integrated control system is used to regulate the temperature, sludge discharge, culture medium replenishment, pH value, and gas discharge of the first heating jacket based on monitoring information.

[0020] The first liquid phase sampling port (32) is used to measure the concentration of organic acid in the liquid phase sample obtained through the first liquid phase sampling port (32) offline. If the concentration of organic acid exceeds 3000 mg / L, the flow rate of the liquid peristaltic pump (42) is increased so that the fermentation liquid in the high temperature reaction device (3) flows into the medium temperature reaction device (5) to control the concentration of organic acid in the high temperature reaction device (3) to be below 3000 mg / L.

[0021] The intermediate-temperature reaction apparatus includes:

[0022] A medium-temperature reaction chamber is provided, the bottom of which is connected to the top of the high-temperature reaction device. The top of the medium-temperature reaction chamber is connected to the gas production quality detection system through a second exhaust pipe. The second exhaust pipe is provided with a second gas phase sampling port and a second gas phase control port. The medium-temperature reaction chamber is located inside a second heating jacket. The side of the medium-temperature reaction chamber is provided with a second liquid discharge outlet and a second liquid phase sampling port, which are connected to the fermentation broth transmission device through a pipeline. A liquid phase sample is obtained through the second liquid phase sampling port, and the organic acid concentration information in the measured liquid phase sample is provided to a second PLC integrated control system. The second liquid discharge outlet, the second heating jacket, and the second gas phase control port are respectively connected to the second PLC integrated control system.

[0023] The second liquid replenishment module has one end inserted into the high-temperature reaction chamber to replenish the culture medium, and the other end of the second liquid replenishment module is connected to the second PLC integrated control system.

[0024] The second monitoring module is located inside the high-temperature reaction chamber and provides monitoring information to the second PLC integrated control system. The second monitoring module includes a pressure sensor, a pH electrode, a temperature electrode, a liquid level sensor, and a dissolved oxygen electrode.

[0025] The second PLC integrated control system is used to regulate the temperature, sludge discharge, culture medium replenishment, pH value, and gas discharge of the heating jacket based on monitoring information.

[0026] The second liquid phase sampling port (52) is used to measure the concentration of organic acid in the liquid sample obtained through the second liquid phase sampling port (52) offline. If the concentration of organic acid exceeds 5000 mg / L, the opening of the valve of the second liquid discharge outlet (51) is increased, or the amount of culture medium replenished in the replenishment module (55) is increased, so as to control the concentration of organic acid in the medium temperature reaction device (5) to be below 5000 mg / L.

[0027] The fermentation broth transfer device includes a microbial filtration device and a liquid peristaltic pump. The microbial filtration device is connected to the side of the high-temperature reaction device, and the liquid peristaltic pump is connected to the side of the mesophilic reaction device.

[0028] The top of the intermediate-temperature reaction device is also connected to a gas production quality detection system, which includes a wet flow meter and an online gas analyzer. The top of the intermediate-temperature reaction device is connected to the wet flow meter and the online gas analyzer in sequence through pipelines to monitor the composition and content of the final methane mixture.

[0029] A method for anaerobic digestion of biomass syngas to produce methanogens, employing the aforementioned anaerobic digestion system for biomass syngas to produce methanogens, comprising:

[0030] (1) Place the first inoculum into the high-temperature reaction device (3), set the fermentation temperature in the high-temperature reaction device (3) to 45-65℃, the pH to 5.5-9.0, the amount of anaerobic granular sludge inoculated to 10-30% of the working volume of the reaction device, and supplement the culture medium so that the inoculation amount and the total amount of culture medium reach 60%-80% of the working volume of the reaction device. The first inoculum is anaerobic granular sludge that has been acclimated and enriched at a temperature of 45-65℃.

[0031] A second inoculum is placed in the mesophilic reaction device (5). The fermentation temperature in the mesophilic reaction device (5) is set to 25-40℃, the pH is 5.0-8.5, the amount of anaerobic granular sludge inoculated is 10-30% of the working volume of the reaction device, and the culture medium is added so that the inoculation amount and the total amount of culture medium reach 60%-80% of the working volume of the reaction device. The second inoculum is anaerobic granular sludge that has been acclimated and enriched at a temperature of 25-40℃.

[0032] (2) Biomass syngas is introduced and passed through a high-temperature reaction device (3) to obtain a mixed product gas, which includes hydrogen, carbon monoxide, carbon dioxide and methane, and the high-temperature reaction device is controlled.

[0033] (3) The concentration of organic acid in the mixture is below 3000 mg / L. The excess organic acid and the mixed gas are transferred to the medium temperature reaction device (5). The concentration of organic acid in the medium temperature reaction device (5) is controlled to be below 5000 mg / L. The mixed gas is subjected to secondary fermentation through the medium temperature reaction device (5), and the organic acid is decomposed to obtain the final mixed gas.

[0034] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0035] (1) In this invention, biomass syngas is first introduced into a high-temperature reaction device for fermentation reaction, that is, fermentation is carried out at 45-65℃. At this temperature, methane gas can be produced efficiently while producing less organic acid, thus having a high methane production efficiency.

[0036] (2) When the organic acid reaches a certain amount, in order to avoid the influence of the organic acid on the production of methane gas, the excess organic acid is transferred to the medium temperature reaction device. In the medium temperature reaction device, the excess organic acid is decomposed. That is, at a temperature of 25-40℃, the inoculum can efficiently decompose the organic acid to produce methane gas. At the same time, the methane mixed gas transported by the high temperature reaction device is subjected to secondary fermentation, thus achieving a high raw material utilization rate. Attached Figure Description

[0037] Figure 1 A schematic diagram of a biomass syngas anaerobic digestion methanogenization system provided for a specific implementation method;

[0038] Figure 2 A structural diagram of the high-temperature reaction device provided for a specific implementation method;

[0039] Figure 3 A structural diagram of a medium-temperature reaction apparatus provided for a specific implementation method.

[0040] Among them, 1-Inlet flow controller, 2-First gas circulation pump, 3-High temperature reaction device, 4-Fermentation broth transfer device, 5-Medium temperature reaction device, 6-Second gas circulation pump, 7-Gas production quality detection system, 8-First aeration device, 9-Second aeration device, 31-First liquid and sludge discharge outlet, 32-First liquid phase sampling port, 33-First gas phase sampling port, 34-First monitoring module, 35-First liquid replenishment module, 36-First gas phase control port, 37-First PLC integration Control system, 38-first heating jacket, 39-high temperature reaction chamber, 41-microbial filtration device, 42-liquid peristaltic pump, 51-second liquid and sludge discharge outlet, 52-second liquid phase sampling port, 53-second gas phase sampling port, 54-second monitoring module, 55-second liquid replenishment module, 56-second gas phase control port, 57-second PLC integrated control system, 58-second heating jacket, 59-high temperature reaction chamber, 71-wet flow meter, 72-online gas analyzer. Detailed Implementation

[0041] The following detailed explanation of the invention patent solution, using specific examples, illustrates the invention patent in detail.

[0042] This invention provides a biomass syngas anaerobic digestion methanogenesis system, such as... Figure 1 As shown, it includes:

[0043] The air intake flow controller 1 is connected to the bottom of the high-temperature reaction device through a pipeline so as to deliver the metered biomass syngas to the high-temperature reaction device 3.

[0044] The high-temperature reaction device 3 is connected to the bottom of the medium-temperature reaction device 5 by a pipeline, so as to transport the gas generated by fermentation at a temperature of 45-65℃ to the medium-temperature reaction device 5. The side of the high-temperature reaction device 3, the fermentation liquid transfer device 4 and the side of the medium-temperature reaction device 5 are connected in sequence by pipelines, so as to transport the organic acid generated by fermentation to the medium-temperature reaction device 5.

[0045] The first gas circulation pump 2 is connected at one end to the top of the high-temperature reaction device 3 and at the other end to the bottom of the high-temperature reaction device 3, so as to circulate the gas from the top of the high-temperature reaction device 3 to the bottom of the high-temperature reaction device 3, forming a gas circulation. The first aeration device 8 is located in the liquid phase of the high-temperature reaction device 3 and is connected to the first gas circulation pump 2, and is used to disperse the gas into the liquid phase.

[0046] The intermediate-temperature reaction device 5 is used to carry out secondary fermentation of the gas supplied by the high-temperature reaction device 3 and decompose organic acids at 25-40℃.

[0047] A second gas circulation pump 6 is connected at one end to the top of the mesothermal reaction device 5 and at the other end to the bottom of the mesothermal reaction device 5, so as to circulate the gas from the top of the mesothermal reaction device 5 to the bottom of the mesothermal reaction device 5. A second aeration device 9 is located in the liquid phase of the mesothermal reaction device 5 and is connected to the second gas circulation pump 6, used to disperse the gas into the liquid phase.

[0048] The medium-temperature reaction device 5 adopts a bottom-inlet method, and uses a second gas circulation pump 6 to circulate headspace gas to the bottom of the reactor and mix it with the gas delivered by the high-temperature reaction device. The gas is then dispersed into the liquid phase through the second aeration device 9.

[0049] The fermentation broth transfer device 4 includes a microbial filtration device 41 and a liquid peristaltic pump 42. The microbial filtration device 41 is connected to the side of the high-temperature reaction device 3, and the liquid peristaltic pump 42 is connected to the side of the mesophilic reaction device 5. The microbial filtration device 41 prevents the anaerobic mixed bacteria in the high-temperature reaction device 3 from entering the mesophilic reaction device 5, effectively isolating the two bacterial groups and maintaining their respective ecological niches. The liquid peristaltic pump 42 introduces the organic acids from the high-temperature reaction device 3 into the mesophilic reaction device 5.

[0050] The top of the intermediate-temperature reaction device 5 is also connected to the gas production quality detection system 7, which includes a wet flow meter 71 and an online gas analyzer 72. The top of the intermediate-temperature reaction device 5 is connected to the wet flow meter 71 and the online gas analyzer 72 in sequence through pipelines to monitor the composition and content of the final methane mixture.

[0051] High-temperature reaction device 3, such as Figure 2 As shown, it includes:

[0052] A high-temperature reaction chamber 39 is provided. The bottom of the high-temperature reaction chamber 39 is connected to the air inlet flow controller 1 through a pipeline. The top of the high-temperature reaction chamber 39 is connected to the bottom of the medium-temperature reaction device 5 through a first exhaust pipeline. The first exhaust pipeline is provided with a first gas phase sampling port 33 and a first gas phase control port 36. The high-temperature reaction chamber 39 is located inside a first heating jacket 38. The first heating jacket 38 heats the high-temperature reaction chamber 39 through a water bath. The side of the high-temperature reaction chamber 39 is provided with a first liquid discharge and sludge discharge outlet 31 and a first liquid phase sampling port 32, and is connected to the fermentation broth transmission device 4 through a pipeline. Liquid phase samples are obtained through the first liquid phase sampling port 32. The first liquid discharge and sludge discharge outlet 31, the first heating jacket 38, and the first gas phase control port 36 are respectively connected to the first PLC integrated control system 37.

[0053] The first replenishment module 35 has one end extending into the high-temperature reaction chamber 39 for replenishing the culture medium, and the other end of the first replenishment module 35 is connected to the first PLC integrated control system 37. The first replenishment module 35 includes a 4M NaOH solution replenishment bottle, a 4M HCl solution replenishment bottle, and a modified basic anaerobic culture medium replenishment bottle.

[0054] The first monitoring module 34 is located inside the high-temperature reaction chamber 39 and provides monitoring information to the first PLC integrated control system 37. The first monitoring module 34 includes a pressure sensor, a pH electrode, a temperature electrode, a liquid level sensor, and a dissolved oxygen electrode.

[0055] The first PLC integrated control system 37 is used to regulate the temperature, sludge discharge, culture medium replenishment, pH value, and gas discharge of the first heating jacket 38 based on monitoring information. The first liquid phase sampling port 32 is used to measure the organic acid concentration of the liquid sample obtained through the first liquid phase sampling port 32 offline. If the organic acid concentration exceeds 3000 mg / L, the flow rate of the liquid peristaltic pump 42 is manually increased to allow the fermentation broth in the high-temperature reaction device 3 to flow into the medium-temperature reaction device 5 as soon as possible, so as to control the organic acid concentration in the high-temperature reaction device 3 to be below 3000 mg / L.

[0056] Medium-temperature reaction apparatus 5, such as Figure 3 As shown, it includes:

[0057] The intermediate-temperature reaction chamber 59 is connected at its bottom to the top of the high-temperature reaction device 3. The top of the intermediate-temperature reaction chamber 59 is connected to the gas production quality detection system 4 through a second exhaust pipe. The second exhaust pipe is provided with a second gas phase sampling port 53 and a second gas phase control port 56. The intermediate-temperature reaction chamber 59 is located inside the second heating jacket 58. The side of the intermediate-temperature reaction chamber 59 is provided with a second liquid discharge and sludge discharge outlet 51 and a second liquid phase sampling port 52, and is connected to the fermentation broth transmission device 4 through a pipeline. Liquid phase samples are obtained through the second liquid phase sampling port 52. The second liquid discharge and sludge discharge outlet 51, the second heating jacket 58, and the second gas phase control port 56 are respectively connected to the second PLC integrated control system 57.

[0058] The second replenishment module 55 has one end extending into the mesothermal reaction chamber 59 for replenishing the culture medium, and the other end of the second replenishment module 55 is connected to the second PLC integrated control system 57. The second replenishment module 55 includes a 4M NaOH solution replenishment bottle, a 4M HCl solution replenishment bottle, and a modified basic anaerobic culture medium replenishment bottle.

[0059] The second monitoring module 54 is located inside the medium-temperature reaction chamber 59 and provides monitoring information to the second PLC integrated control system 57. The second monitoring module 54 includes a pressure sensor, a pH electrode, a temperature electrode, a liquid level sensor, and a dissolved oxygen electrode.

[0060] The second PLC integrated control system 57 is used to regulate the temperature of the heating jacket, the amount of liquid and sludge discharge, the amount of culture medium replenishment, the pH value, and the amount of gas discharge based on monitoring information. The second liquid phase sampling port 52 is used to manually increase the opening of the valve of the second liquid and sludge discharge outlet 51 or manually increase the amount of culture medium replenishment in the replenishment module 55 after the concentration of organic acid in the liquid sample obtained through the second liquid phase sampling port 52 is measured offline. This is done to control the concentration of organic acid in the mesophilic reaction device 5 to be below 5000 mg / L.

[0061] The anaerobic digestion process of microorganisms mainly utilizes components such as H2, CO2, and CO in syngas. At a mesophilic temperature of 35℃, anaerobic mixed microbial communities primarily convert syngas into methane-based product gas through a combination of hydrogen nutrient and acetate nutrient pathways. Under these conditions, the rate of methane production by the microbial community is slow, but it possesses a strong ability to produce and degrade organic acids. However, the presence of numerous reaction byproducts can easily lead to the accumulation of large amounts of organic acids, thus inhibiting the methanogenesis process and hindering long-term reactor operation. At a high temperature of 55℃, the anaerobic mixed microbial community primarily converts syngas into methane-based product gas through a hydrogen nutrient pathway. Compared to the mesophilic conditions, this process is rapid and produces fewer organic acid byproducts. However, the ability of anaerobic microbial communities to metabolize organic acids is weaker under high-temperature conditions, and long-term reactor operation still leads to the accumulation of organic acids, reducing both the reaction rate and the effective utilization rate of raw materials.

[0062] The beneficial effects of this invention are as follows:

[0063] (1) The present invention carries out the first stage of anaerobic digestion of syngas to produce methanogens in a high-temperature reaction device, taking advantage of the high efficiency of anaerobic mixed bacterial groups in producing methanogens and the low amount of by-products under high-temperature conditions, thus ensuring the high efficiency of the overall reaction.

[0064] (2) The present invention transfers the organic acids produced in the first stage of the anaerobic digestion of syngas to produce methanogens, effectively avoiding the problem of organic acid inhibition.

[0065] (3) This invention utilizes the strong ability of anaerobic mixed bacteria to produce methane from organic acids under mesophilic conditions to further convert the by-products of the first stage, thereby effectively improving the utilization rate of raw materials and the methane yield.

[0066] (4) The reaction device of the present invention uses the raw material gas as the stirring power, which can efficiently enhance gas-solid-liquid mass transfer and accelerate the anaerobic digestion rate, while avoiding energy consumption caused by mechanical stirring.

[0067] (5) Both stages of the present invention can be flexibly supplemented with additional raw material components according to production needs.

[0068] Example 1

[0069] A method for anaerobic digestion of biomass syngas to produce methanates, employing the aforementioned anaerobic digestion system for biomass syngas to produce methanates, comprising:

[0070] (1) The first inoculum is placed in the high-temperature reaction device 3. The fermentation temperature in the high-temperature reaction device 3 is set to 55℃, the pH is 6.5-7.5, the anaerobic granular sludge inoculum amount is 20% (v / v), and the culture medium content is 50% (v / v). The first inoculum is anaerobic granular sludge that has been domesticated and enriched by syngas with a composition of H2:CO2:CO:N2=10 / 15 / 25 / 50 (v / v / v / v) at a high temperature of 55℃ for a long time. The culture medium is a modified basic anaerobic culture medium. The chemical composition of its stock solution is shown in Table 1. Each liter of basic anaerobic culture medium contains 10mL of stock solution A, 2mL of stock solution B, 1mL of stock solution C and 1mL of stock solution D.

[0071] The second inoculum is placed in the mesophilic reaction device 5. The fermentation temperature in the mesophilic reaction device (5) is set to 35°C, the sludge inoculum amount is 20% (v / v), the culture medium content is 50% (v / v), and the pH is 6.5-7.8. The second inoculum is anaerobic granular sludge that has been acclimated and enriched by long-term mesophilic treatment at 35°C and acetic acid concentration of 1200 mg / L. The culture medium is a modified basic anaerobic culture medium. The chemical composition of its stock solution is shown in Table 1. Each liter of basic anaerobic culture medium contains 10 mL of A stock solution, 2 mL of B stock solution, 1 mL of C stock solution and 1 mL of D stock solution.

[0072] (2) Biomass syngas is introduced and passed through a high-temperature reaction device (3) to obtain an initial mixed product gas. The main components of the initial mixed product gas include hydrogen, carbon monoxide, carbon dioxide, and methane. The concentration of organic acid in the high-temperature reaction device (3) is controlled at 3000 mg / L. The excess organic acid and the initial methane mixed gas are transferred to a medium-temperature reaction device (5). The concentration of organic acid in the medium-temperature reaction device (5) is controlled at 5000 mg / L. The initial methane mixed gas is subjected to secondary fermentation through the medium-temperature reaction device (5), and the organic acid is decomposed to obtain the final methane mixed gas.

[0073] Table 1. Improved basal anaerobic culture medium stock solution

[0074]

[0075] (3) Evaluate the performance of the reaction apparatus. The inlet and outlet gas velocities are determined by the readings of the inlet flow controller and the outlet wet flow meter, and the product gas composition at the outlet is measured by an online gas analyzer.

[0076] When the inlet gas composition is H2:CO2:CO = 20%:30%:50%, the residence time (GRT) of the high-temperature reactor is 1.25 h, and the gas circulation rate of the high-temperature and medium-temperature reactors is 40 L / L. recAt a rate of [per unit] h, the composition of the outlet gas is: H2:CO2:CO:CH4 = 5.70%: 59.99%: 15.84%: 16.76%. The feedstock utilization rate for hydrogen is 79.45%, and for carbon monoxide it is 77.16%. Methane production is 1.68 mmol / L. rec / h. Methane yield was 88.74%.

[0077] In this embodiment, the feed gas composition contains more CO and less H2. If the H2 content of the feed gas is increased and the CO content is reduced, a better methanogenic effect will be achieved.

[0078] Example 2

[0079] Unlike Example 1, when the inlet gas composition is H2:CO2:CO = 20%:30%:50%, the residence time (GRT) of the high-temperature reactor is 1.25 h, and the gas circulation rate of the high-temperature and medium-temperature reactors becomes 113 L / L. rec At a rate of [per unit] h, the composition of the outlet gas is: H2:CO2:CO:CH4 = 3.52%:70.00%:8.60%:3.47%. The feedstock utilization rate for hydrogen is 85.05%, and for carbon monoxide it is 85.19%. Methane production is 1.82 mmol / L. rec / h. Methane yield is 95.01%.

[0080] Comparative Example 1

[0081] Unlike Example 1, the intermediate-temperature reaction unit 5 was removed, and the reaction proceeded only in one stage at the high-temperature unit 3. At this time, the composition of the outlet gas was: H2:CO2:CO:CH4 = 5.74%: 60.44%: 15.96%: 16.15%. The methane yield was 1.60 mmol / L. rec / h. The methane yield was 84.88%. Example 1 improved the methane yield by approximately 4.5% compared to Comparative Example 1.

[0082] Comparative Example 2

[0083] Unlike Example 1, the high-temperature reaction device 3 is removed, and the reaction is carried out in only one stage at the medium-temperature device 5. In addition, the gas circulation stirring is replaced with mechanical stirring.

[0084] When the inlet gas composition is H2:CO2:CO = 20%:30%:50%, the gas residence time (GRT) in the high-temperature reactor is 1.25 h, and the mechanical stirring speed is 250 rpm, the outlet gas composition is: H2:CO2:CO:CH4 = 13.61%:48.63%:31.77%:5.73%. The methane yield is 0.55 mmol / L. rec / h. Methane yield was 42.12%.

[0085] The two reasons for the poor operation of the reactor are: insufficient gas-liquid mass transfer capacity under mechanical stirring; and a large amount of organic acid byproducts from the methanation of syngas under intermediate temperature conditions, with an accumulation concentration exceeding 3000 mg / L, which negatively inhibited the efficient progress of the reaction.

Claims

1. A method for anaerobic digestion of biomass syngas to produce methanogens, characterized in that, A biomass syngas anaerobic digestion methanogenic system is employed, comprising: S1. Place the first inoculum in the high-temperature reaction device (3), set the fermentation temperature in the high-temperature reaction device (3) to 45-65℃, the pH to 5.5-9.0, the amount of anaerobic granular sludge inoculated to 10-30% of the working volume of the reaction device, and supplement the culture medium so that the inoculation amount and the total amount of culture medium reach 60%-80% of the working volume of the reaction device. The first inoculum is anaerobic granular sludge that has been acclimated and enriched with syngas with a composition of H2:CO2:CO:N2 = 10 / 15 / 25 / 50 (v / v / v / v) at a temperature of 45-65℃. The second inoculum is placed in the mesophilic reaction device (5). The fermentation temperature in the mesophilic reaction device (5) is set to 25-40℃, the pH is 5.0-8.5, the amount of anaerobic granular sludge inoculated is 10-30% of the working volume of the reaction device, and the culture medium is added so that the inoculation amount and the total amount of culture medium reach 60%-80% of the working volume of the reaction device. The second inoculum is anaerobic granular sludge that has been acclimated and enriched by acetic acid at a temperature of 25-40℃. S2. Biomass syngas is introduced and mixed product gas is obtained through a high-temperature reaction device (3). The mixed product gas includes hydrogen, carbon monoxide, carbon dioxide and methane. The concentration of organic acid in the high-temperature reaction device (3) is controlled to be below 3000 mg / L. The excess organic acid and the mixed gas are transferred to a medium-temperature reaction device (5). The concentration of organic acid in the medium-temperature reaction device (5) is controlled to be below 5000 mg / L. The mixed gas is subjected to secondary fermentation through the medium-temperature reaction device (5), and the organic acid is decomposed to obtain the final mixed gas. The biomass syngas anaerobic digestion methanogenic system includes: The air intake flow controller (1) is connected to the bottom of the high-temperature reaction device via a pipeline so as to transport the metered biomass syngas to the high-temperature reaction device (3). A high-temperature reaction device (3) is connected at its top to the bottom of a medium-temperature reaction device (5) via a pipeline to facilitate the transport of gas generated during fermentation at a temperature of 45-65°C to the medium-temperature reaction device (5). The sides of the high-temperature reaction device (3), the fermentation broth transfer device (4), and the sides of the medium-temperature reaction device (5) are sequentially connected via pipelines to transport the organic acids generated during fermentation to the medium-temperature reaction device (5). The intermediate temperature reaction device (5) is used to carry out secondary fermentation of the gas supplied by the high temperature reaction device (3) and decompose organic acids at 25-40℃. It also includes a first gas circulation pump (2), one end of which is connected to the top of the high-temperature reaction device (3) and the other end is connected to the bottom of the high-temperature reaction device (3) so as to circulate the gas at the top of the high-temperature reaction device (3) to the bottom of the high-temperature reaction device (3). It also includes a first aeration device, which is located in the liquid phase of the high-temperature reaction device (3) and connected to the first gas circulation pump (2) for dispersing gas into the liquid phase; It also includes a second gas circulation pump (6), one end of which is connected to the top of the intermediate temperature reaction device (5) and the other end is connected to the bottom of the intermediate temperature reaction device (5) so as to circulate the gas at the top of the intermediate temperature reaction device (5) to the bottom of the intermediate temperature reaction device (5). It also includes a second aeration device, which is located in the liquid phase of the mesothermal reaction device (5) and connected to the second gas circulation pump (6) for dispersing gas into the liquid phase.

2. The method for anaerobic digestion of biomass syngas to produce methanogens according to claim 1, characterized in that, The high-temperature reaction device (3) includes: A high-temperature reaction chamber (39) is connected to the air inlet flow controller (1) via a pipeline at its bottom. The top of the high-temperature reaction chamber (39) is connected to the bottom of the medium-temperature reaction device (5) via a first exhaust pipeline. The first exhaust pipeline is provided with a first gas phase sampling port (33) and a first gas phase control port (36). The high-temperature reaction chamber (39) is located inside a first heating jacket (38). The side of the high-temperature reaction chamber (39) is provided with a first liquid discharge outlet (31) and a first liquid phase sampling port (32), and is connected to the fermentation liquid transmission device (4) via a pipeline. Liquid phase samples are obtained through the first liquid phase sampling port (32). The first liquid discharge outlet (31), the first heating jacket (38), and the first gas phase control port (36) are respectively connected to the first PLC integrated control (37) system. The first replenishment module (35) has one end extending into the high-temperature reaction chamber (39) for replenishing culture medium, and the other end of the first replenishment module (35) is connected to the first PLC integrated control system (37). The first monitoring module (34), located inside the high-temperature reaction chamber (39), provides monitoring information to the first PLC integrated control system (37). The first monitoring module (34) includes a pressure sensor, a pH electrode, a temperature electrode, a liquid level sensor, and a dissolved oxygen electrode; and The first PLC integrated control system (37) is used to regulate the temperature, sludge discharge, culture medium replenishment, pH value and gas discharge of the first heating jacket (38) based on monitoring information, and is also used to control the concentration of organic acid in the high-temperature reaction device (3) to be below 3000 mg / L.

3. The method for anaerobic digestion of biomass syngas to produce methanogens according to claim 1, characterized in that, The intermediate temperature reaction apparatus (5) includes: The bottom of the intermediate temperature reaction chamber (59) is connected to the top of the high temperature reaction device (3), and the top of the intermediate temperature reaction chamber (59) is connected to the fermentation liquid transmission device (4) through a second exhaust pipe. The second exhaust pipe is provided with a second gas phase sampling port (53) and a second gas phase control port (56). The intermediate temperature reaction chamber (59) is located inside the second heating jacket (58). The side of the intermediate temperature reaction chamber (59) is provided with a second liquid discharge and sludge discharge outlet (51) and a second liquid phase sampling port (52), and is connected to the fermentation liquid transmission device (4) through a pipe. Liquid phase samples are obtained through the second liquid phase sampling port (52). The second liquid discharge and sludge discharge outlet (51), the second heating jacket (58), and the second gas phase control port (56) are respectively connected to the second PLC integrated control system (57). The second replenishment module (55) has one end inserted into the medium-temperature reaction chamber (59) for replenishing culture medium, and the other end of the second replenishment module (55) is connected to the second PLC integrated control system (57). The second monitoring module (54), located inside the intermediate-temperature reaction chamber (59), provides monitoring information to the second PLC integrated control system (57). The second monitoring module (54) includes a pressure sensor, a pH electrode, a temperature electrode, a liquid level sensor, and a dissolved oxygen electrode; and The second PLC integrated control system (57) is used to regulate the temperature of the heating jacket, the amount of liquid and sludge discharged, the amount of culture medium replenished, the pH value and the amount of gas discharged based on the monitoring information, and is also used to control the concentration of organic acid in the medium temperature reaction device (5) to be below 5000 mg / L.

4. The method for anaerobic digestion of biomass syngas to produce methanogens according to claim 1, characterized in that, The fermentation broth transfer device (4) includes a microbial filtration device (41) and a liquid peristaltic pump (42). The microbial filtration device (41) is connected to the side of the high-temperature reaction device (3), and the liquid peristaltic pump (42) is connected to the side of the medium-temperature reaction device (5).

5. The method for anaerobic digestion of biomass syngas to produce methanogens according to claim 1, characterized in that, The top of the intermediate temperature reaction device (5) is also connected to the gas production quality detection system (7), which includes a wet flow meter (71) and an online gas analyzer (72). The top of the intermediate temperature reaction device (5) is connected to the wet flow meter (71) and the online gas analyzer (72) in sequence through pipelines to monitor the composition and content of the final methane mixture.

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