Double-backflow sectional type fermentation process and system

Abstract

The invention relates to a double-reflux sectional fermentation process and system, and the fermentation process comprises the following steps: mixing organic wastes with reflux biogas slurry to obtain a raw material, carrying out hydrolytic acidification on the raw material to obtain a first material, controlling the reaction temperature of hydrolytic acidification at 50-55 DEG C, and controlling the first material in a transition section; mixing and reacting the first material with reflux biogas produced by a subsequent anaerobic fermentation section at the reaction temperature of 45-50 DEG C to obtain a second material, and feeding the second material into the anaerobic fermentation section; and fermenting the second material at 40-45 DEG C to produce biogas slurry and biogas. According to the method, different temperatures are set at different stages of the fermentation process, the efficiency of each reaction stage is greatly improved, and in the hydrolysis stage, the high temperature of 50-55 DEG C is combined with microorganisms provided by biogas slurry backflow, so that the cellulose decomposition rate is improved, and the hydrolysis period is shortened; in the anaerobic fermentation section, the optimum activity of methanogens can be maintained at the temperature of 40-45 DEG C, the methane yield is improved, and the methane purity in the biogas is improved.

Description

Technical Field

[0001] This invention relates to the field of biogas engineering fermentation technology, specifically to a dual-reflux segmented fermentation process and system. Background Technology

[0002] Although traditional biogas engineering technologies are mature, poor economic efficiency has been a persistent problem for the entire industry. In particular, the increasing costs of raw materials and energy have led to a rise in the unit production cost of biogas projects, further limiting the development of the biogas industry.

[0003] Currently, methods to improve unit gas production rate mainly involve optimizing the culture strain and controlling the types of raw materials, but their effect on reducing unit cost is very limited. Summary of the Invention

[0004] This invention provides a dual-reflux segmented fermentation process and system to improve biogas yield and purity, effectively reduce unit cost, and provide a new technical route for the biogas industry.

[0005] In a first aspect, the present invention provides a dual reflux staged fermentation process, comprising the following steps: Hydrolysis stage treatment: Organic waste is mixed with recycled biogas slurry to obtain raw material with a solid content of 15-20%. The raw material is hydrolyzed and acidified to obtain the first material. The reaction temperature of hydrolysis and acidification is 50-55℃. The first material enters the transition stage for regulation. Transition section control: The first material is mixed and reacted with biogas produced in the subsequent anaerobic fermentation section at a reaction temperature of 45-50℃ and a reflux ratio of 3-5%. When the dissolved oxygen is ≤0.2mg / L and the volatile fatty acid concentration is ≤5000mg / L, the second material is obtained and enters the anaerobic fermentation section. Anaerobic fermentation stage: The second material ferments at 40-45℃ for 20-25 days to produce biogas slurry and biogas.

[0006] In one optional embodiment, the biogas is desulfurized and dehydrated before being used to generate electricity; the power generation takes place in an internal combustion generator set; the flue gas generated by the internal combustion generator set is recycled to produce saturated steam and hot water, the saturated steam is used in the hydrolysis stage, and the hot water is circulated through pipelines to heat the anaerobic fermentation section.

[0007] In one alternative embodiment, the organic waste is treated to a particle size of <2 cm.

[0008] In one optional embodiment, the biogas slurry is injected into the hydrolysis tank at a reflux ratio of 50-100%; the hydrolysis acidification reaction time is 1-3 days.

[0009] In one optional embodiment, the raw material obtained after the biogas slurry is recycled has a carbon-to-nitrogen ratio of 20-30:1 and a pH value of 5.8-6.2.

[0010] In one alternative embodiment, the biogas is dispersed by a microporous gas distributor and then enters the first material regulated in the transition section.

[0011] In one optional embodiment, the diameter of the biogas bubbles dispersed by the microporous gas distributor is <0.5 mm.

[0012] Secondly, the present invention also provides a dual reflux segmented fermentation system, comprising: a hydrolysis tank, a transition tank, and a fermentation tank, which are connected by a controllable valve; Biogas slurry reflux unit: connects the fermenter outlet and the hydrolysis tank inlet, including a flow sensor and an alkalinity probe; Biogas recirculation unit: includes a microporous gas distributor and recirculation pipes; Detection module: Real-time detection of dissolved oxygen concentration, volatile fatty acid concentration, and pH value; Internal combustion generator set: The biogas produced by the fermentation tank is used for the internal combustion generator set.

[0013] In one optional embodiment, the hydrolysis tank and the transition tank are concentric tanks, with the hydrolysis tank being the inner tank and the transition tank being the outer tank, and the hydrolysis tank being 0.5-1.5m lower than the transition tank.

[0014] In one optional embodiment, the fermenter is an independent sealed tank with an insulation layer on the outer wall and a stirrer and a heater inside the tank. It also includes internal combustion generator sets that use biogas produced by fermentation tanks to generate electricity. The flue gas produced by the internal combustion generator sets is recycled to produce saturated steam and hot water. The saturated steam is used to heat the hydrolysis tank, and the hot water is circulated through pipelines to heat the fermentation tank.

[0015] The technical solution of this invention has the following advantages: 1. This invention provides a dual-reflux segmented fermentation process, comprising the following steps: Hydrolysis stage treatment: organic waste is mixed with refluxed biogas slurry to obtain raw material with a solid content of 15-20%. The raw material undergoes hydrolysis and acidification to obtain a first material. The hydrolysis and acidification reaction temperature is 50-55℃. The first material enters the transition stage for regulation. Transition stage regulation: the first material is mixed and reacted with biogas produced in the subsequent anaerobic fermentation stage at a reaction temperature of 45-50℃, with a reflux ratio of 3-5%. When dissolved oxygen ≤0.2mg / L and volatile fatty acid concentration ≤5000mg / L, a second material is obtained. The second material enters the anaerobic fermentation stage. Anaerobic fermentation stage: the second material is fermented at 40-45℃ for 20-25 days, producing biogas slurry and biogas.

[0016] This invention significantly improves the efficiency of each reaction stage by implementing different temperature settings at different stages of the fermentation process. In the hydrolysis stage, a high temperature of 50-55℃ combined with microorganisms provided by the biogas slurry reflux increases the cellulose decomposition rate by 50% and shortens the hydrolysis cycle to within 3 days. Since the reactants have a long contact time with air before fermentation, they contain a high concentration of dissolved oxygen, generally greater than 0.5 g / L. Excessive dissolved oxygen concentration inhibits the activity of methanogens. By controlling the biogas reflux to the transition stage, the inhibitory effect of dissolved oxygen on methanogens is eliminated, optimizing the anaerobic environment. The second material obtained from the transition stage, combined with a temperature of 40-45℃ in the anaerobic fermentation stage, maintains the optimal activity of methanogens, while simultaneously improving reaction mass transfer efficiency, enhancing gas-liquid mixing, promoting carbon dioxide participation in the acidification reaction, and increasing methane yield by 30-45%. Furthermore, the methane purity in the biogas increases to 62-67%, demonstrating remarkable effectiveness. Attached Figure Description

[0017] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0018] Figure 1 This is a flow chart of the fermentation process of this invention.

[0019] Figure 2 This is a process connection plan of the hydrolysis tank, transition tank and fermentation tank of the dual reflux segmented fermentation system of the present invention; Figure 3 This is an elevation view showing the process connection of the hydrolysis tank, transition tank, and fermentation tank in the dual reflux segmented fermentation system of the present invention.

[0020] Explanation of reference numerals in the attached figures: 1. Hydrolysis tank; 2. Transition tank; 3. Fermentation tank; 4. Raw material screw conveyor device; 5. Pipelines; 501. Biogas return pipeline, 502. Biogas slurry return pipeline, 503. Steam pipeline, 504. Feeding pipeline, 505. Biogas output pipeline. Detailed Implementation

[0021] The following embodiments are provided to better understand the present invention, but the following embodiments do not constitute a limitation on the content and scope of protection of the present invention. Any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the scope of protection of the present invention.

[0022] Unless otherwise specified, all experimental steps or conditions in the examples were performed according to conventional experimental procedures and conditions in the art. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0023] Example 1 A dual-reflux staged fermentation process, employing Figure 2 and Figure 3 The dual reflux staged fermentation system shown in the figure has the following specific process: Figure 1 As shown, proceed with the following steps: S1. Collect organic waste Collect high-solids organic waste such as livestock manure and crop straw, avoiding the introduction of impurities such as sand, gravel, woven bags, and plastic bags during the collection process.

[0024] S2, Raw material pretreatment The collected raw materials enter the pretreatment system, which includes devices such as stirring and screw conveyor. When there are multiple raw materials, they can be stirred and mixed first to ensure that the different materials are fully mixed, which is beneficial to the subsequent hydrolysis and fermentation stages. The mixed materials are sent to the hydrolysis tank 1 through the raw material screw conveyor 4.

[0025] S3, Hydrolysis Section Treatment Hydrolysis tank 1 is equipped with a steam heating system. The steam comes from the flue gas recovery and utilization system of the biogas internal combustion generator set. The steam enters the bottom of hydrolysis tank 1 through steam pipe 503. The steam pressure and quantity are determined according to the raw material processing volume to ensure that the hydrolysis section is stably maintained at 53℃ for 2 days. Simultaneously, a biogas slurry return system is installed to return biogas slurry to hydrolysis tank 1 through biogas slurry return pipe 502 to adjust the solid content of the raw material in hydrolysis tank 1 to 18%. The raw material is stirred and mixed by a stirrer. The biogas slurry return ratio is determined according to the moisture content of the raw material, generally 50-100%. In addition to adjusting the solid content of the raw material, the biogas slurry return also replenishes hydrogen-producing, acetic acid-producing, and methanogenic microorganisms in the hydrolysis tank, improving the hydrolysis reaction efficiency. The volatile fatty acid concentration of the raw material in the hydrolysis section is 7000-8000 mg / L.

[0026] S4, Transition Segment Control The hydrolyzed material enters transition tank 2, such as... Figure 2As shown, the hydrolysis tank 1 and the transition tank 2 are concentric tanks, with the hydrolysis tank being the inner tank and the transition tank being the outer tank. The height of the hydrolysis tank is 1m lower than that of the transition tank. When the hydrolysis tank is full, the material overflows into the outer tank. The material overflowing into the transition tank 2 is the first material. Biogas is returned from the fermentation tank 3 to the first material in the transition tank 2 through the biogas return pipe 501, with a return ratio of 4% of the gas production. A microporous gas distributor is installed in the transition tank 2, located at the end of the biogas return pipe 501. This microporous gas distributor ensures that the biogas returned through the biogas return pipe 501 is evenly distributed in the first material. The returned biogas can eliminate the inhibition of anaerobic microorganisms by dissolved oxygen in the first material and promote the participation of carbon dioxide in the acidification reaction. When the dissolved oxygen concentration of the first material in the transition tank 2 is ≤0.2mg / L and the volatile fatty acid concentration is ≤5000mg / L, the second material is obtained. The second material is fed into the fermentation tank 3 through the feed pipe 504 and a plunger pump installed on the feed pipe 504.

[0027] S5, Anaerobic Fermentation Section Fermentation tank 3 is an independent, sealed tank with an external insulation layer and an internal stirring device and heating system to ensure the second material is fermented at 43°C for a period of 23 days. After fermentation, the material is discharged to obtain digestate. The solid content of the digestate is generally 8-12%. After solid-liquid separation and dehydration, biogas slurry and biogas residue are obtained. The solid content of the biogas slurry is approximately 3-5%. The biogas slurry is returned to the hydrolysis tank through the biogas slurry return pipe 502 to adjust the material concentration. The biogas residue has a solid content of 30-35% and can be used to produce organic fertilizer. 4% of the daily biogas production is returned to the transition tank.

[0028] S6, biogas internal combustion generator set for power generation The biogas produced by anaerobic fermentation is desulfurized and dehydrated after being output through biogas output pipeline 505, and then enters the internal combustion generator set to generate electricity. The flue gas produced by the internal combustion engine is recycled to produce saturated steam and hot water. The saturated steam is used in the hydrolysis stage, and the hot water is circulated through pipelines to heat the fermentation tank.

[0029] In this embodiment, the biogas yield is 573 L / kgVS, and the methane purity in the biogas is 62.8%.

[0030] Example 2 A dual-reflux staged fermentation process includes the following steps: S1. Collect organic waste Collect high-solids organic waste such as livestock manure and crop straw, avoiding the introduction of impurities such as sand, gravel, woven bags, and plastic bags during the collection process.

[0031] S2, Raw material pretreatment The collected raw materials enter the pretreatment system, which includes devices such as stirring and screw conveyor. When there are multiple raw materials, they can be stirred and mixed first to ensure that the different materials are fully mixed, which is beneficial to the subsequent hydrolysis and fermentation stages. The mixed materials are then sent to the hydrolysis tank by screw conveyor.

[0032] S3, Hydrolysis Section Treatment The hydrolysis tank is equipped with a steam heating system. The steam comes from the flue gas recovery and utilization system of the biogas internal combustion generator set. The steam pressure and consumption are determined according to the raw material processing volume, ensuring that the hydrolysis section is stably maintained at 50℃ for one day. A biogas slurry reflux system is also installed to adjust the solid content of the raw materials in the hydrolysis tank to 15%. The raw materials are stirred and mixed by a stirrer. The biogas slurry reflux ratio is determined according to the moisture content of the raw materials, generally 50-100%. Besides adjusting the solid content of the raw materials, the biogas slurry reflux also replenishes hydrogen-producing, acetic acid-producing, and methanogenic microorganisms in the hydrolysis tank, improving the efficiency of the hydrolysis reaction. The volatile fatty acid concentration of the raw materials in the hydrolysis section is 7000-8000 mg / L.

[0033] S4, Transition Segment Control After hydrolysis, the material enters the transition tank, such as... Figure 2 As shown, the hydrolysis tank and the transition tank are concentric, with the hydrolysis tank being the inner tank and the transition tank the outer tank. The height of the hydrolysis tank is 1.5m lower than that of the transition tank. When the hydrolysis tank is full, the material overflows into the outer tank. The material overflowing into the transition tank is the first material. Biogas is returned from the fermentation tank to the transition tank at a return ratio of 3% of the gas production. The transition tank is equipped with a microporous gas distributor to ensure that the returned biogas is evenly distributed in the first material. The returned biogas can eliminate the inhibition of anaerobic microorganisms by dissolved oxygen in the first material and promote the participation of carbon dioxide in the acidification reaction. When the dissolved oxygen concentration of the first material in the transition tank is ≤0.2mg / L and the volatile fatty acid concentration is ≤5000mg / L, the second material is obtained. The second material is fed into the fermentation tank through a plunger pump.

[0034] S5, Anaerobic Fermentation Section The fermentation tank is an independent, sealed vessel with an external insulation layer and an internal stirring device and heating system to ensure the second material is fermented at 40°C. The fermentation cycle is 20 days. After fermentation, the digestate is discharged to obtain digestate. The solid content of the digestate is generally 8-12%. After solid-liquid separation and dehydration, biogas slurry and biogas residue are obtained. The solid content of the biogas slurry is about 3-5%. The biogas slurry is returned to the hydrolysis tank to adjust the material concentration. The biogas residue has a solid content of 30-35% and can be used to produce organic fertilizer. 3% of the daily biogas production is returned to the transition tank.

[0035] S6, biogas internal combustion generator set for power generation The biogas produced by anaerobic fermentation is desulfurized and dehydrated before entering the internal combustion generator set. The flue gas produced by the internal combustion engine is recycled to produce saturated steam and hot water. The saturated steam is used in the hydrolysis stage, and the hot water is circulated through pipelines to heat the fermentation tank.

[0036] In this embodiment, the biogas yield is 512 L / kgVS, and the methane purity in the biogas is 60.3%.

[0037] Example 3 A dual-reflux staged fermentation process, including S1. Collect organic waste Collect high-solids organic waste such as livestock manure and crop straw, avoiding the introduction of impurities such as sand, gravel, woven bags, and plastic bags during the collection process.

[0038] S2, Raw material pretreatment The collected raw materials enter the pretreatment system, which includes devices such as stirring and screw conveyor. When there are multiple raw materials, they can be stirred and mixed first to ensure that the different materials are fully mixed, which is beneficial to the subsequent hydrolysis and fermentation stages. The mixed materials are then sent to the hydrolysis tank by screw conveyor.

[0039] S3, Hydrolysis Section Treatment The hydrolysis tank is equipped with a steam heating system. The steam comes from the flue gas recovery and utilization system of the biogas internal combustion generator set. The steam pressure and consumption are determined according to the raw material processing volume, ensuring that the hydrolysis section is stably maintained at 55℃ for 3 days. A biogas slurry reflux system is also installed to adjust the solid content of the raw materials in the hydrolysis tank to 18%. The raw materials are stirred and mixed by a stirrer. The biogas slurry reflux ratio is determined according to the moisture content of the raw materials, generally 50-100%. Besides adjusting the solid content of the raw materials, the biogas slurry reflux also replenishes hydrogen-producing, acetic acid-producing, and methanogenic microorganisms in the hydrolysis tank, improving the efficiency of the hydrolysis reaction. The volatile fatty acid concentration of the raw materials in the hydrolysis section is 7000-8000 mg / L.

[0040] S4, Transition Segment Control After hydrolysis, the material enters the transition tank, such as... Figure 2 As shown, the hydrolysis tank and the transition tank are concentric, with the hydrolysis tank being the inner tank and the transition tank the outer tank. The height of the hydrolysis tank is 0.5m lower than that of the transition tank. When the hydrolysis tank is full, the material overflows into the outer tank. The material overflowing into the transition tank is the first material. Biogas is returned from the fermentation tank to the transition tank at a return ratio of 5% of the gas production. The transition tank is equipped with a microporous gas distributor to ensure that the returned biogas is evenly distributed in the first material. The returned biogas can eliminate the inhibition of anaerobic microorganisms by dissolved oxygen in the first material and promote the participation of carbon dioxide in the acidification reaction. When the dissolved oxygen concentration of the first material in the transition tank is ≤0.2mg / L and the volatile fatty acid concentration is ≤5000mg / L, the second material is obtained. The second material is fed into the fermentation tank through a plunger pump.

[0041] S5, Anaerobic Fermentation Section The fermentation tank is an independent, sealed vessel with an external insulation layer and an internal stirring device and heating system to ensure the second material is fermented at 45°C. The fermentation cycle is 25 days. After fermentation, the digestate is discharged to obtain digestate. The solid content of the digestate is generally 8-12%. After solid-liquid separation and dehydration, biogas slurry and biogas residue are obtained. The solid content of the biogas slurry is about 3-5%. The biogas slurry is returned to the hydrolysis tank to adjust the material concentration. The biogas residue has a solid content of 30-35% and can be used to produce organic fertilizer. 5% of the daily biogas production is returned to the transition tank.

[0042] S6, biogas internal combustion generator set for power generation The biogas produced by anaerobic fermentation is desulfurized and dehydrated before entering the internal combustion generator set. The flue gas produced by the internal combustion engine is recycled to produce saturated steam and hot water. The saturated steam is used in the hydrolysis stage, and the hot water is circulated through pipelines to heat the fermentation tank.

[0043] In this embodiment, the biogas yield is 665 L / kgVS, and the methane purity in the biogas is 65.2%.

[0044] Comparative Example 1 A segmented fermentation process, differing from Example 1 in that it lacks a transition stage control, includes: S1. Collect organic waste Collect high-solids organic waste such as livestock manure and crop straw, avoiding the introduction of impurities such as sand, gravel, woven bags, and plastic bags during the collection process.

[0045] S2, Raw material pretreatment The collected raw materials enter the pretreatment system, which includes devices such as stirring and screw conveyor. When there are multiple raw materials, they can be stirred and mixed first to ensure that the different materials are fully mixed, which is beneficial to the subsequent hydrolysis and fermentation stages. The mixed materials are then sent to the hydrolysis tank by screw conveyor.

[0046] S3, Hydrolysis Section Treatment The hydrolysis tank is equipped with a steam heating system. The steam comes from the flue gas recovery and utilization system of the biogas internal combustion generator set. The steam pressure and consumption are determined according to the raw material processing volume, ensuring that the hydrolysis section is stably maintained at 53℃ for 2 days. A biogas slurry reflux system is also installed to adjust the solid content of the raw materials in the hydrolysis tank to 18%. The raw materials are stirred and mixed by a stirrer. The biogas slurry reflux ratio is determined according to the moisture content of the raw materials, generally 50-100%. Besides adjusting the solid content of the raw materials, the biogas slurry reflux also replenishes hydrogen-producing, acetic acid-producing, and methanogenic microorganisms in the hydrolysis tank, improving the hydrolysis reaction efficiency. The volatile fatty acid concentration of the raw materials in the hydrolysis section is 7000-8000 mg / L.

[0047] S4, First Material Acquisition After hydrolysis, the material is fed directly into the fermenter via a plunger pump.

[0048] S5, Anaerobic Fermentation Section The fermentation tank is an independent, sealed vessel with an external insulation layer and an internal stirring device and heating system to ensure the initial material is fermented at 43°C for 23 days. After fermentation, the material is discharged to obtain digestate. The solid content of the digestate is generally 8-12%. After solid-liquid separation and dehydration, biogas slurry and biogas residue are obtained. The solid content of the biogas slurry is about 3-5%. The biogas slurry is returned to the hydrolysis tank to adjust the material concentration. The biogas residue has a solid content of 30-35% and can be used to produce organic fertilizer.

[0049] S6, biogas internal combustion generator set for power generation The biogas produced by anaerobic fermentation is desulfurized and dehydrated before entering the internal combustion generator set. The flue gas produced by the internal combustion engine is recycled to produce saturated steam and hot water. The saturated steam is used in the hydrolysis stage, and the hot water is circulated through pipelines to heat the fermentation tank.

[0050] In this comparative example, the biogas yield was 436 L / kgVS, and the methane purity in the biogas was 57.7%.

[0051] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A dual-reflux segmented fermentation process, characterized in that, Includes the following steps: Hydrolysis stage treatment: Organic waste is mixed with recycled biogas slurry to obtain raw material with a solid content of 15-20%. The raw material is hydrolyzed and acidified to obtain the first material. The reaction temperature of hydrolysis and acidification is 50-55℃. The first material enters the transition stage for regulation. Transition section control: The first material is mixed and reacted with biogas produced in the subsequent anaerobic fermentation section at a reaction temperature of 45-50℃ and a reflux ratio of 3-5%. When the dissolved oxygen is ≤0.2mg / L and the volatile fatty acid concentration is ≤5000mg / L, the second material is obtained and enters the anaerobic fermentation section. Anaerobic fermentation stage: The second material ferments at 40-45℃ for 20-25 days to produce biogas slurry and biogas.

2. The fermentation process according to claim 1, characterized in that, The biogas is desulfurized and dehydrated before being used to generate electricity. The power generation takes place in an internal combustion generator set. The flue gas generated by the internal combustion generator set is recycled to produce saturated steam and hot water. The saturated steam is used in the hydrolysis stage, and the hot water is circulated through pipelines to heat the anaerobic fermentation section.

3. The fermentation process according to claim 1, characterized in that, The organic waste is treated to a particle size of <2cm.

4. The fermentation process according to claim 1, characterized in that, The biogas slurry is injected into the hydrolysis tank at a reflux ratio of 50-100%; And / or, the reaction time for the hydrolysis and acidification is 1-3 days.

5. The fermentation process according to claim 4, characterized in that, The raw material obtained after the biogas slurry is recycled has a carbon-to-nitrogen ratio of 20-30:1 and a pH value of 5.8-6.

2.

6. The fermentation process according to claim 1, characterized in that, The biogas is dispersed by a microporous gas distributor and then enters the first material in the transition section for regulation.

7. The fermentation process according to claim 6, characterized in that, The diameter of the biogas bubbles dispersed by the microporous gas distributor is <0.5mm.

8. A dual-reflux segmented fermentation system for implementing the fermentation process according to any one of claims 1-7, characterized in that, include: The hydrolysis tank, transition tank, and fermentation tank are connected by controllable valves; Biogas slurry reflux unit: connects the fermenter outlet and the hydrolysis tank inlet, including a flow sensor and an alkalinity probe; Biogas recirculation unit: includes a microporous gas distributor and recirculation pipes; Detection module: Real-time detection of dissolved oxygen concentration, volatile fatty acid concentration, and pH value.

9. The fermentation system according to claim 8, characterized in that, The hydrolysis tank and the transition tank are concentric tanks, with the hydrolysis tank being the inner tank and the transition tank being the outer tank. The hydrolysis tank is 0.5-1.5m lower than the transition tank.

10. The fermentation system according to claim 8 or 9, characterized in that, The fermentation tank is an independent, sealed tank with an insulation layer on the outer wall and a stirrer and heater inside. And / or, it also includes an internal combustion generator set that generates electricity using biogas produced by the fermenter, wherein the flue gas produced by the internal combustion generator set is recovered to produce saturated steam and hot water, the saturated steam is used to heat the hydrolysis tank, and the hot water is circulated through pipelines to heat the fermenter.

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