Vertical flow type anaerobic fermentation system and method based on bionic function

Abstract

The invention belongs to the field of biogas engineering, and particularly relates to a vertical-flow anaerobic fermentation system and method based on a bionic function, and the system comprises an anaerobic fermentation tank which is sequentially divided into a gas chamber area, a rumen bionic area, an anaerobic methane production area and a discharge sand setting area from top to bottom; the feeding system is connected with the top of the anaerobic fermentation tank and comprises a material mixing unit and a feeding unit which are connected in sequence; the marsh gas collecting system is connected with the gas chamber area and comprises a marsh gas purifying unit, a pressurizing unit and a marsh gas utilizing unit which are connected in sequence; the discharging system is connected with the discharging sand setting area; the feeding system and the biogas collecting system are respectively connected with the anaerobic fermentation tank, and the double-circulation backflow system comprises a material circulation backflow system and a biogas circulation backflow system. According to the invention, rapid hydrolysis and efficient anaerobic conversion of the fiber raw material can be realized, and the biogas yield, methane concentration and organic matter degradation rate of the fiber raw material are improved.

Description

Technical Field

[0001] The present invention relates to the field of biogas engineering, and particularly to an upflow anaerobic fermentation system and method based on bionic functions. Background Art

[0002] Agricultural waste is rich in resources. According to statistics, the amount of manure and sewage produced in cattle farms in 2023 reached more than 1.4 billion tons, and the amount of crop straw produced was about 734 million tons. It contains huge biogas production potential. Considering the comprehensive utilization rate of agricultural waste and biogas resource utilization channels in various regions, it is estimated that the annual biogas production can reach 23 billion cubic meters, accounting for more than 5% of the natural gas consumption in 2023. However, due to the high content of cellulose, hemicellulose, lignin, etc. in crop straw, cow dung and other organic wastes, their stable structure increases the difficulty of biogas resource utilization and seriously affects the stable operation of biogas projects.

[0003] Cows are typical ruminants. Their rumen digestive system contains a variety of microorganisms such as bacteria and fungi, which can achieve efficient conversion of roughage such as silage, straw, and hay. Taking adult large cows as an example, the volume of their rumen is about 140 - 230L, and the daily gas production in the rumen is as high as 600 - 700L·d -1 , and mainly consists of 50% - 70% CO 2 and 20% - 45% CH 4 and other gases. As an efficient fibrous raw material fermentation system, the volumetric gas production rate of the rumen system reaches 3.0 - 4.2L·L -1 ·d -1 , much higher than the volumetric gas production rate of 0.8 - 1.2m 3 ·m -3 ·d -1 in current biogas projects using straw, cow dung, etc. In addition, due to the lack of low-cost and efficient pretreatment means, the operation stability is also poor. Especially when adopting high-concentration fermentation processes, such as the intelligent continuous fermentation system for simulating rumen digestion disclosed in Patent CN104893965B, the dry matter content in the fermentation tank is high, the material fluidity is poor, and the mass transfer is uneven, which is more likely to cause local acidification or ammonia nitrogen accumulation, thereby inhibiting the activity of methanogens and further exacerbating problems such as low fermentation efficiency and poor operation stability in biogas projects. Summary of the Invention

[0004] To solve the problems of low hydrolysis efficiency in the fermentation tank during high-concentration fermentation of fibrous raw materials, uneven mass transfer and local acidification caused by poor material fluidity mentioned in the background art, the present invention provides an upflow anaerobic fermentation system and method based on bionic functions, which utilizes the material density difference and vertical temperature gradient distribution at different heights in the upflow anaerobic fermentation tank to achieve efficient rumen-like biological conversion of fibrous raw materials, and improves the methane production rate and organic matter degradation rate of fibrous raw materials.

[0005] In the first aspect, the present invention provides an upflow anaerobic fermentation system based on bionic functions, comprising: An anaerobic fermentation tank, which is divided into a gas chamber area, a rumen bionic area, an anaerobic methane production area and a discharge sand sedimentation area from top to bottom in sequence; A feeding system connected to the top of the anaerobic fermentation tank, the feeding system comprising a mixing unit and a feeding unit connected in sequence; A biogas collection system connected to the gas chamber area, the biogas collection system comprising a biogas purification unit, a pressurization unit and a biogas utilization unit connected in sequence; A discharge system connected to the discharge sand sedimentation area; A double-cycle reflux system composed of the feeding system and the biogas collection system respectively connected to the anaerobic fermentation tank, the double-cycle reflux system comprising a material cycle reflux system and a biogas cycle reflux system.

[0006] The upflow anaerobic fermentation process provided by the present invention adopts an upflow anaerobic fermentation tank, and utilizes the gravity sedimentation of raw materials in the fermentation tank, the gas production of the fermentation tank and the reflux biogas to make the internal materials float to form a certain density difference, thereby strengthening the rumen bionic hydrolysis process and anaerobic methane production fermentation in the fermentation tank, prolonging the residence time of light fiber materials in the fermentation tank, and improving the utilization rate of raw materials; the set fermentation liquid circulation reflux fully mixes and prepares the raw materials and the fermentation liquid, and then through the crushing of the feeding device, it not only simulates the chewing and digestion of ruminants, but also realizes the adjustment of the concentration, pH value of the fermentation raw materials and the purpose of microbial inoculation, increases the contact area and time between the raw materials and the strains, and improves the conversion and utilization efficiency of the raw materials; the set temperature control measures include preheating the mixing unit and heating the middle and lower parts of the upflow fermentation tank, and utilizing the vertical temperature gradient distribution characteristics in the upflow fermentation tank to make the upper rumen bionic area of the fermentation tank at the optimal reaction temperature, strengthening the hydrolysis and acid production reaction of fiber materials, thereby improving the conversion and utilization rate of raw materials.

[0007] Preferably, the mixing unit is a double-helix silo structure, which can achieve the purpose of forward feeding and reverse mixing of materials.

[0008] Preferably, the mixing unit is provided with temperature increase and heat preservation measures, which can realize the pre-temperature increase of materials.

[0009] Preferably, a feeding crushing device is arranged in the feeding system to further homogenize and crush the mixed materials, increasing the contact area between the raw materials and the strains and improving the utilization efficiency of microorganisms in the subsequent upflow anaerobic fermenter.

[0010] Preferably, the feeding system includes no less than 3 inlet branches into the tank.

[0011] Preferably, the feeding sequence of the inlet branches is controlled by a PLC program to ensure uniform feeding.

[0012] Preferably, no less than 3 biogas reflux inlets are arranged in the anaerobic methane production area, which can not only strengthen the formation of the upflow state of the materials in the fermenter to form material density differences at different heights, but also strengthen the reduction of carbon dioxide gas in the biogas by methane-producing microorganisms to generate methane, thereby increasing the methane concentration in the biogas.

[0013] Furthermore, the biogas circulation reflux system forms a cycle by connecting the pressurizing unit and the anaerobic methane production area.

[0014] Furthermore, the flow rate of the biogas introduced into the anaerobic methane production area is 7 - 10 m / s.

[0015] Furthermore, the material circulation reflux system forms a cycle by connecting the discharge sand settling area and the mixing unit.

[0016] Furthermore, the height-diameter ratio of the anaerobic fermenter is ≥2.

[0017] In a second aspect, the present invention provides a method for anaerobic fermentation using the above-mentioned upflow anaerobic fermentation system based on bionic functions, including the following steps: 1) Mixing and crushing the anaerobic sludge obtained by anaerobic domestication of cow dung with fiber raw materials to obtain fermentation raw materials; 2) Feeding the fermentation raw materials into the anaerobic fermenter to sequentially carry out rumen bionic hydrolysis acidification and anaerobic methane production to obtain biogas and fermentation broth; 3) Mixing and crushing the rumen bionic hydrolysis materials, fermentation broth and fiber raw materials to obtain fermentation materials, and repeating step 2), wherein the mixing ratio of the rumen bionic hydrolysis materials to the fiber raw materials is (1 - 2):1, and the mixing ratio of the fermentation materials to the fiber raw materials is (2 - 3):1.

[0018] Through the reflux circulation inoculation of the hydrolysis materials and fermentation broth in the rumen bionic area, the present invention not only realizes the adjustment of the concentration and pH value of the fermentation raw materials, but also achieves the purpose of microorganism inoculation, and simulates the chewing, saliva secretion and digestion of ruminants, etc., improving the methane conversion rate and organic matter degradation rate of fiber raw materials.

[0019] Furthermore, the fiber raw material is cow dung or straw fiber raw material.

[0020] Further, in step 1), the fermentation raw materials are pre-warmed to 35°C ± 2°C, and the TS concentration of the raw materials reaches 15% - 20%.

[0021] Further, in step 2), the temperature for rumen bionic hydrolysis to produce acid is 39°C ± 2°C, the pH value is 6.5 - 7.2, and the ORP value is -450 mV - -250 mV.

[0022] Further, in step 2), the temperature in the anaerobic fermentation methane production area is 37°C ± 2°C, the pH value is 7.2 - 8.0, and the ORP value is -450 mV - -300 mV.

[0023] Further, in step 3), the mixing ratio of the rumen bionic hydrolysis material to the fiber raw material is (1 - 2):1.

[0024] Further, in step 3), the mixing ratio of the fermentation material to the fiber raw material is (2 - 3):1.

[0025] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. The upflow anaerobic fermentation tank adopted in the present invention utilizes the gravity sedimentation of the raw materials in the fermentation tank, the gas production in the fermentation tank, and the reflux biogas to make the internal materials float to form a certain density difference, thereby strengthening the rumen bionic hydrolysis process and anaerobic methane fermentation in the fermentation tank, prolonging the residence time of the light fiber materials in the fermentation tank, and improving the utilization rate of the raw materials.

[0026] 2. The present invention has a strong biological conversion effect on fiber materials such as cow dung or straw. Through pre-fermentation by mixing and formulation, rumen bionic hydrolysis, and anaerobic methane fermentation, it simulates the functions of chewing and saliva secretion digestion of bionic ruminants, and improves the methane conversion rate and organic matter degradation rate of fiber raw materials.

[0027] 3. In the present invention, through preheating the mixing unit and temperature control of the upflow fermentation tank, a vertical temperature gradient distribution is formed in the fermentation tank, so that the rumen bionic area in the upper part of the fermentation tank is at the optimal reaction temperature, strengthening the hydrolysis and acid production reaction of fiber materials.

[0028] 4. In the technology of the present invention, through the regulation of key parameters such as temperature, pH value, and ORP value of different process units, precise control of each process unit is achieved, improving the overall fermentation efficiency of the system. Description of the Drawings

[0029] Figure 1 It is the process flow chart in the present invention. Detailed Embodiments

[0030] The following further describes the present invention in combination with embodiments.

[0031] General Embodiment A vertical flow anaerobic fermentation system comprises an anaerobic fermentation tank, which is divided into a gas chamber area, a rumen biomimetic area, an anaerobic methanogenic area and a discharge sand settling area from top to bottom. A mixed feed port is arranged at the top of the anaerobic fermentation tank, a biogas outlet is arranged at the upper part of the gas chamber area of ​​the anaerobic fermentation tank, a biogas reflux inlet is arranged at the lower part of the anaerobic methanogenic area, detection ports are arranged at the upper, middle and lower parts of the anaerobic fermentation tank, a discharge port is arranged in the middle part of the discharge sand settling area, and a sand discharge port is arranged at the bottom.

[0032] like Figure 1 As shown, a vertical flow anaerobic fermentation system based on bionic function, cow dung or straw fiber raw materials enter the mixing unit for mixing, are mixed and crushed by the feeding unit, and then enter the anaerobic fermentation tank, from top to bottom, they pass through the gas chamber area, are hydrolyzed and acidified in the rumen bionic area, and are fermented and produced biogas in the anaerobic methanogenesis area. After the fermentation is completed, they are discharged from the bottom discharge sand settling area. At this point, a part of the fermentation liquid returns to the mixing unit to be re-mixed with the fiber raw material, passes through the feeding unit into the anaerobic fermentation tank, undergoes bionic hydrolysis and anaerobic methanogenesis, and then passes through the discharge sand settling area to return to the mixing unit again, forming a material circulation reflux system, and another part of the fermentation liquid is discharged from the system to enter the biogas residue and liquid treatment unit for further treatment. The biogas generated during the fermentation process enters the biogas collection system, flows out through the biogas outlet, and is processed by the biogas purification unit and the booster unit. A part of it circulates back to the anaerobic methanogenic area in the anaerobic fermentation tank, that is, the biogas is introduced from the bottom of the anaerobic fermentation tank to form reflux biogas, thereby forming a biogas circulation reflux system, and the other part enters the biogas utilization unit, among which a part of the hydrolyzed and acidified materials in the rumen bionic area flows back to the mixing unit for back-mixing with the raw materials.

[0033] The method for anaerobic fermentation using the vertical flow anaerobic fermentation system comprises the following steps: 1) Raw material preparation Anaerobic sludge obtained by anaerobic domestication of cow dung is mixed and crushed with fiber raw materials to obtain fermentation raw materials. The temperature of the mixture of anaerobic sludge and fiber raw materials is 35°C±2°C, and the TS concentration of the raw materials is 15%-20%.

[0034] 2) Start operation The fermentation raw materials are subjected to rumen bionic hydrolysis and anaerobic fermentation to obtain biogas and fermentation liquid, wherein the temperature of rumen bionic hydrolysis is 39°C±2°C, the pH value is 6.5-7.2, and the ORP value is -450--250mV; the temperature of anaerobic fermentation is 37°C±2°C, the pH value is 7.2-8.0, and the ORP value is -450--300mV.

[0035] 3) Stable operation Mix the rumen biomimetic hydrolyzed material, fermentation broth, and fiber raw material, and then crush them to obtain the fermentation material. Repeat step 2), where the mixing ratio of the rumen biomimetic hydrolyzed material to the fiber raw material is (1 - 2):1, and the mixing ratio of the fermentation material to the fiber raw material is (2 - 3):1.

[0036] Specifically, part of the biogas generated in step 2) is introduced from the bottom of the anaerobic fermentation. The flow rate of the introduced biogas is 7 - 10 m / s.

[0037] 4) Calculate the yield Calculate the biogas production rate, methane content, and organic matter degradation rate.

[0038] Among them, the VS gas production rate: In the formula, R vs is the VS gas production rate, m 3 ·kg -1 VS; P b is the biogas production, m 3 ·d -1 ; Q is the feed rate, m 3 ; S 0 is the raw material concentration, kgVS·m -3 .

[0039] Organic matter degradation rate: In the formula, VS R is the VS degradation rate %; VS T is the VS measurement value % of the fermentation substrate on the Tth day; VS 0 is the VS measurement value % of the anaerobic sludge.

[0040] Example 1 1) Raw material preparation Mix and crush the anaerobic sludge obtained by anaerobic domestication of cow dung with the fiber raw material to obtain the initial fermentation raw material. Among them, the temperature of the mixed material of anaerobic sludge and fiber raw material is 35 °C, and the raw material TS concentration is 20%.

[0041] 2) Start-up operation After subjecting the fermentation raw material to rumen biomimetic hydrolysis and anaerobic fermentation, biogas and fermentation broth are obtained. Among them, the temperature of the rumen biomimetic hydrolysis is 39 °C, the pH value is 6.5, and the ORP value is -300 mV. Among them, the temperature of the anaerobic fermentation is 37 °C, the pH value is 7.5, and the ORP value is -450 mV. Among them, part of the biogas generated is introduced from the bottom of the anaerobic fermentation. The flow rate of the introduced biogas is 8 m / s.

[0042] 3) Stable operation Mix the rumen bionic hydrolyzed material, fermentation broth and fiber raw material, and crush them to obtain a fermentation material. Repeat step 2), where the mixing ratio of the rumen bionic hydrolyzed and acidified material to the fiber raw material is 1:1, and the mixing ratio of the fermentation material to the fiber raw material is 2:1.

[0043] 4) Calculate the yield Calculate the biogas production rate, methane content, and organic matter degradation rate.

[0044] Comparative Example 1 The difference between this comparative example and Example 1 is only that in this comparative example, in step 3), the rumen bionic hydrolyzed and acidified material is not mixed with the fiber raw material, and the rest of the process is the same as that of Example 1. The specific process is as follows: 1) Raw material preparation Mix and crush the anaerobic sludge obtained by anaerobic domestication of cow dung with the fiber raw material to obtain a fermentation raw material. Among them, the temperature of the mixed material of anaerobic sludge and fiber raw material is 35°C, and the raw material TS concentration is 20%.

[0045] 2) Start-up operation After rumen bionic hydrolysis and anaerobic fermentation of the fermentation raw material, biogas and fermentation broth are obtained. Among them, the temperature of rumen bionic hydrolysis is 39°C, the pH value is 6.5, and the ORP value is -300 mV. Among them, the temperature of anaerobic fermentation is 37°C, the pH value is 7.5, and the ORP value is -450 mV. Part of the biogas generated is introduced from the bottom of the anaerobic fermentation, and the flow rate of the introduced biogas is 8 m / s.

[0046] 3) Stable operation Mix and crush the fermentation broth with the fiber raw material to obtain an initial fermentation material. Repeat step 2), where the mixing ratio of the fermentation material to the fiber raw material is 2:1.

[0047] 4) Calculate the yield Calculate the biogas production rate, methane content, and organic matter degradation rate.

[0048] Comparative Example 2 The difference between this comparative example and Example 1 is only that in this comparative example, in step 3), the mixing ratio of the rumen bionic hydrolyzed and acidified material to the fiber raw material is 0.5:1, and the rest of the process is the same as that of Example 1. The specific steps are as follows: 1) Raw material preparation Mix and crush the anaerobic sludge obtained by anaerobic domestication of cow dung with the fiber raw material to obtain an initial fermentation raw material. Among them, the temperature of the mixed material of anaerobic sludge and fiber raw material is 35°C, and the raw material TS concentration is 20%.

[0049] 2) Start-up operation The fermentation raw materials are subjected to rumen bionic hydrolysis and anaerobic fermentation to obtain biogas and fermentation broth. Among them, the temperature of rumen bionic hydrolysis is 39 °C, the pH value is 6.5, and the ORP value is -300 mV. Among them, the temperature of anaerobic fermentation is 37 °C, the pH value is 7.5, and the ORP value is -450 mV. Part of the biogas generated is introduced from the bottom of anaerobic fermentation, and the flow rate of the introduced biogas is 8 m / s.

[0050] 3) Stable operation The rumen bionic hydrolysis materials, fermentation broth and fiber raw materials are mixed and crushed to obtain fermentation materials, and step 2) is repeated. Among them, the mixing ratio of rumen bionic hydrolysis materials to fiber raw materials is 0.5:1, and the mixing ratio of fermentation materials to fiber raw materials is 2:1.

[0051] 4) Calculate the yield Calculate the biogas production rate, methane content, and organic matter degradation rate.

[0052] Comparative example 3 The difference between this comparative example and Example 1 is only that in this comparative example, in step 3), the mixing ratio of rumen bionic hydrolysis materials to fiber raw materials is 5:1, and the rest of the processes are the same as those in Example 1. The specific steps are as follows: 1) Raw material preparation The anaerobic sludge obtained by anaerobic domestication of cow dung and fiber raw materials are mixed and crushed to obtain the initial fermentation raw materials. Among them, the temperature of the mixed materials of anaerobic sludge and fiber raw materials is 35 °C, and the raw material TS concentration is 20%.

[0053] 2) Start-up operation The fermentation raw materials are subjected to rumen bionic hydrolysis and anaerobic fermentation to obtain biogas and fermentation broth. Among them, the temperature of rumen bionic hydrolysis is 39 °C, the pH value is 6.5, and the ORP value is -300 mV. Among them, the temperature of anaerobic fermentation is 37 °C, the pH value is 7.5, and the ORP value is -450 mV. Part of the biogas generated is introduced from the bottom of anaerobic fermentation. Among them, the flow rate of the introduced biogas is 8 m / s.

[0054] 3) Stable operation The rumen bionic hydrolysis materials, fermentation broth and fiber raw materials are mixed and crushed to obtain fermentation materials, and step 2) is repeated. Among them, the mixing ratio of rumen bionic hydrolysis materials to fiber raw materials is 5:1, and the mixing ratio of fermentation materials to fiber raw materials is 2:1.

[0055] 4) Calculate the yield Calculate the biogas production rate, methane content, and organic matter degradation rate.

[0056] Table 1 Influence of rumen bionic hydrolysis material reflux on fermentation Bionic hydrolysis material and raw material reflux ratio <![CDATA[VS gas production rate m 3 / kgVS]]> Methane content % Organic matter (VS) degradation rate % Example 1 1:1 345 63.9 39.3 Comparative Example 1 0:1 290 60.2 36.2 Comparative Example 2 0.5:1 310 61.3 37.5 Comparative Example 3 5:1 355 64.1 40.8 From the data in Table 1, it can be seen that compared with the comparative example, the reflux of rumen biomimetic hydrolyzed materials will promote parameters such as the VS gas production rate, methane content, and organic matter degradation rate of the anaerobic system. When the mixing ratio is 1:1, the improvement rates compared to the blank group are 18.97%, 6.15%, and 11.11% respectively. When the mixing ratio is 0.5:1, the efficiency of the anaerobic system will decrease, and when the mixing ratio is further increased to 5:1, the operating cost of the reflux equipment will increase.

[0057] Comparative Example 4 The difference between this comparative example and Example 1 is only that in this comparative example, in step 3), the fermentation materials were not mixed with the fiber raw materials, and the rest of the processes were the same as in Example 1. The specific steps are as follows: 1) Raw material preparation The anaerobic sludge obtained by anaerobic domestication of cow dung sewage was mixed and crushed with the fiber raw materials to obtain the initial fermentation raw materials. Among them, the temperature of the mixed materials of anaerobic sludge and fiber raw materials was 35°C, and the TS concentration of the raw materials was 20%.

[0058] 2) Start-up operation The fermentation raw materials were subjected to rumen biomimetic hydrolysis and anaerobic fermentation to obtain biogas and fermentation broth. Among them, the temperature of rumen biomimetic hydrolysis was 39°C, the pH value was 6.5, and the ORP value was -300 mV. Among them, the temperature of anaerobic fermentation was 37°C, the pH value was 7.5, and the ORP value was -450 mV. Part of the biogas produced was introduced from the bottom of the anaerobic fermentation, and the flow rate of the introduced biogas was 8 m / s.

[0059] 3) Stable operation The rumen biomimetic hydrolyzed materials were mixed and crushed with the fiber raw materials to obtain the fermentation materials, and step 2) was repeated, where the mixing ratio of the rumen biomimetic hydrolyzed materials to the fiber raw materials was 1:1.

[0060] 4) Calculate the yield Calculate the biogas production rate, methane content, and organic matter degradation rate.

[0061] Comparative Example 5 The difference between this comparative example and Example 1 is only that in this comparative example, in step 3), the mixing ratio of the fermentation materials to the fiber raw materials was 1:1, and the rest of the processes were the same as in Example 1. The specific steps are as follows: 1) Raw material preparation The anaerobic sludge obtained by anaerobic domestication of cow dung was mixed and crushed with the fiber raw materials to obtain the initial fermentation raw materials. Among them, the temperature of the mixed materials of anaerobic sludge and fiber raw materials was 35°C, and the TS concentration of the raw materials was 20%.

[0062] 2) Start-up operation After subjecting the fermentation raw materials to rumen bionic hydrolysis and anaerobic fermentation, biogas and fermentation broth are obtained. Among them, the temperature of rumen bionic hydrolysis is 39 °C, the pH value is 6.5, and the ORP value is -300 mV. Among them, the temperature of anaerobic fermentation is 37 °C, the pH value is 7.5, and the ORP value is -450 mV. Part of the biogas generated is introduced from the bottom of the anaerobic fermentation, and the flow rate of the introduced biogas is 8 m / s..

[0063] 3) Stable operation Mix and crush the rumen bionic hydrolysis materials, fermentation broth and fiber raw materials to obtain fermentation materials, and repeat step 2). Among them, the mixing ratio of rumen bionic hydrolysis materials to fiber raw materials is 1:1, and the mixing ratio of fermentation materials to fiber raw materials is 1:1.

[0064] 4) Calculate the yield Calculate the biogas production rate, methane content, and organic matter degradation rate.

[0065] Comparative Example 6 The difference between this comparative example and Example 1 is only that in this comparative example, in step 3), the mixing ratio of fermentation materials to fiber raw materials is 5:1, and the rest of the process is the same as that in Example 1. The specific steps are as follows: 1) Raw material preparation Mix and crush the anaerobic sludge obtained by anaerobic domestication treatment of cow dung and fiber raw materials to obtain fermentation raw materials.

[0066] Specifically, the temperature of the mixed material of anaerobic sludge and fiber raw materials is 35 °C, and the raw material TS concentration is 20%.

[0067] 2) Start-up operation After subjecting the fermentation raw materials to rumen bionic hydrolysis and anaerobic fermentation, biogas and fermentation broth are obtained. Among them, the temperature of rumen bionic hydrolysis is 39 °C, the pH value is 6.5, and the ORP value is -300 mV. The temperature of anaerobic fermentation is 37 °C, the pH value is 7.5, and the ORP value is -450 mV. Part of the biogas generated is introduced from the bottom of the anaerobic fermentation, and the flow rate of the introduced biogas is 8 m / s..

[0068] 3) Stable operation Mix and crush the rumen bionic hydrolysis materials, fermentation broth and fiber raw materials to obtain fermentation materials, and repeat step 2). Among them, the mixing ratio of rumen bionic hydrolysis materials to fiber raw materials is 1:1, and the mixing ratio of fermentation materials to fiber raw materials is 5:1.

[0069] 4) Calculate the yield Calculate the biogas production rate, methane content, and organic matter degradation rate.

[0070] Table 2 Influence of fermentation material reflux on fermentation It can be obtained from the data in Table 2 that, compared with the comparative example, the reflux of the fermentation material will promote parameters such as the VS gas production rate, methane content, and organic matter degradation rate of the anaerobic system. Recycling and inoculating the fermentation material can increase the types of microorganisms in the mixed material, increase the fermentation time of the mixed material and microorganisms, and improve the fermentation efficiency. When the mixing ratio of the fermentation material to the fiber raw material is 2:1, the improvement rates compared to the blank group are 15.77%, 3.73%, and 5.36% respectively; when the mixing ratio is 1:1, the efficiency of the anaerobic system will be reduced, and when the mixing ratio is further increased to 5:1, the operating cost of the reflux equipment will increase.

[0071] Comparative Example 7 The difference between this comparative example and Example 1 is only that in this comparative example, in step 3), biogas reflux is not carried out, and the rest of the processes are the same as those in Example 1. The specific steps are as follows: 1) Raw material preparation The anaerobic sludge obtained by anaerobic domestication of cow dung is mixed and crushed with the fiber raw material to obtain the initial fermentation raw material. The temperature of the mixed material of anaerobic sludge and fiber raw material is 35°C, and the TS concentration of the raw material is 20%.

[0072] 2) Start-up operation The fermentation raw material is subjected to rumen bionic hydrolysis and anaerobic fermentation to obtain biogas and fermentation liquid. Among them, the temperature of rumen bionic hydrolysis is 39°C, the pH value is 6.5, the ORP value is -300 mV, the temperature of anaerobic fermentation is 37°C, the pH value is 7.5, and the ORP value is -450 mV.

[0073] 3) Stable operation The rumen bionic hydrolysis material, fermentation liquid and fiber raw material are mixed and crushed to obtain the fermentation material, and step 2) is repeated. Among them, the mixing ratio of the rumen bionic hydrolysis material to the fiber raw material is 1:1, and the mixing ratio of the fermentation material to the fiber raw material is 2:1.

[0074] 4) Calculate the yield Calculate the biogas production rate, methane content, and organic matter degradation rate.

[0075] Table 3 Influence of biogas reflux on fermentation Whether biogas reflux is carried out <![CDATA[VS gas production rate m 3 / kgVS]]> Methane content % Organic matter (VS) degradation rate % Example 1 Yes 345 63.9 39.3 Comparative Example 7 No 339 60.1 38.5 It can be obtained from the data in Table 2 that, compared with the comparative example, biogas reflux will introduce CO of biogas 2 , and the purified biogas uniformly enters the anaerobic methane production area from the bottom of the anaerobic fermentation area, strengthening the density difference of the materials in the anaerobic fermentation area, and at the same time promoting H 2 to reduce CO 2 and generate CH through the way 4The reaction improves the methane concentration in biogas, thereby increasing the fermentation rate and promoting the methane content in biogas to increase by 6.32%.

[0076] Example 2 1) Raw material preparation The anaerobic sludge obtained by anaerobic domestication of cow dung is mixed and crushed with the fiber raw material to obtain the initial fermentation raw material. The temperature of the mixed material of anaerobic sludge and fiber raw material is 37°C, and the TS concentration of the raw material is 15%.

[0077] 2) Start-up operation The fermentation raw material is subjected to rumen biomimetic hydrolysis and anaerobic fermentation to obtain biogas and fermentation broth. The temperature of rumen biomimetic hydrolysis is 41°C, the pH value is 7.0, the ORP value is -250 mV, the temperature of anaerobic fermentation is 39°C, the pH value is 8.0, and the ORP value is -400 mV. Part of the biogas generated is introduced from the bottom of the anaerobic fermentation, and the flow rate of the introduced biogas is 10 m / s.

[0078] 3) Stable operation The rumen biomimetic hydrolysis acidification material, fermentation broth and fiber raw material are mixed and crushed to obtain the fermentation material, and step 2) is repeated, where the mixing ratio of the rumen biomimetic hydrolysis material to the fiber raw material is 1.2:1, and the mixing ratio of the fermentation material to the fiber raw material is 2.5:1.

[0079] Unless otherwise specified, the raw materials and equipment used in the present invention are common raw materials and equipment in the art; unless otherwise specified, the methods used in the present invention are conventional methods in the art.

[0080] The above are only the preferred embodiments of the present invention, and do not impose any limitations on the present invention. Any simple modifications, changes and equivalent transformations made to the above embodiments according to the technical essence of the present invention still fall within the protection scope of the technical solution of the present invention.

Claims

1. A vertical flow anaerobic fermentation system based on bionic function, characterized in that: include: Anaerobic fermentation tank, which is divided into gas chamber area, rumen biomimetic area, anaerobic methanogenesis area and discharge sand settling area from top to bottom; A feeding system connected to the top of the anaerobic fermentation tank, the feeding system comprising a mixing unit and a feeding unit connected in sequence; A biogas collection system connected to the gas chamber area, the biogas collection system comprising a biogas purification unit, a pressurizing unit and a biogas utilization unit connected in sequence; A discharge system connected to the discharge sand settling area; A double circulation reflux system is composed of a feeding system and a biogas collection system respectively connected to the anaerobic fermentation tank, and the double circulation reflux system includes a material circulation reflux system and a biogas circulation reflux system.

2. A vertical flow anaerobic fermentation system based on bionic function according to claim 1, characterized in that: The height-to-diameter ratio of the anaerobic fermentation tank is ≥2.

3. The vertical flow anaerobic fermentation system based on bionic function according to claim 1, characterized in that: The biogas circulation reflow system connects the booster unit and the anaerobic methanogenizing area to form a cycle.

4. A vertical flow anaerobic fermentation system based on bionic function according to claim 1 or 3, characterized in that: The biogas flow rate entering the anaerobic fermentation tank is 7 to 10 m / s.

5. A vertical flow anaerobic fermentation system based on bionic function according to claim 1 or 2, characterized in that: The material circulation reflux system connects the discharge sand settling area and the mixing unit to form a circulation.

6. A method for anaerobic fermentation using the vertical flow anaerobic fermentation system based on bionic function as claimed in any one of claims 1 to 5, characterized in that: The following steps are involved: 1) mixing and crushing anaerobic sludge obtained by anaerobic domestication of cow dung with fiber raw materials to obtain initial fermentation raw materials; 2) sending the fermentation raw materials into the anaerobic fermentation tank to carry out rumen bionic hydrolysis and acidification and anaerobic methanogenesis in sequence to obtain biogas and fermentation liquid; 3) Pre-fermenting the rumen bionic hydrolysis acidified material, the fermentation liquid and the fiber raw material to obtain the fermentation raw material, and repeating step 2), wherein the mixing ratio of the rumen bionic hydrolysis acidified material to the fiber raw material is (1-2):1, and the mixing ratio of the fermentation liquid to the fiber raw material is (2-3):

1.

7. The method according to claim 6, characterized in that In step 1), the TS concentration of the fermentation raw material after being treated by the mixing unit is 15% to 20%.

8. The method according to claim 6, characterized in that In step 2), the temperature of rumen bionic hydrolysis acidification is 39°C±2°C, the pH value is 6.5-7.2, and the ORP value is -450mV--250mV.

9. The method according to claim 6 or 8, characterized in that: In step 2), the temperature of the anaerobic fermentation methanogenic zone is 37°C ± 2°C, the pH value is 7.2 to 8.0, and the ORP value is -450mV to -300mV.

10. The method according to claim 6, characterized in that In step 3), the temperature of the fermentation raw material after being processed by the mixing unit is 35°C±2°C.

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