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CN-122012631-A - Method for preparing methane by anaerobic fermentation of straw

CN122012631ACN 122012631 ACN122012631 ACN 122012631ACN-122012631-A

Abstract

The invention provides a method for preparing methane by anaerobic fermentation of straw, and relates to the technical field of production methods of biogas. The method for preparing methane by utilizing straw anaerobic fermentation comprises the steps of mixing kitchen waste with anaerobic granular sludge, adjusting pH to 5.5-6.2, performing dark fermentation to prepare hydrogen to obtain dark fermentation biogas slurry, performing pretreatment on the straw by using the dark fermentation biogas slurry in the step S1, and performing anaerobic fermentation to produce methane. The invention adopts the dark fermentation biogas slurry prepared by a specific process to pretreat the straw, and then carries out anaerobic fermentation to produce methane, so that the methane production effect is good. The invention also realizes the multistage utilization of organic waste and the simultaneous output of two green energy sources of hydrogen and methane by carrying out anaerobic fermentation on the straw pretreated by the dark fermentation biogas slurry, and the dark fermentation biogas slurry is used for producing methane by anaerobic fermentation.

Inventors

  • HAO XIAONAN
  • ZUO XIAOYU
  • Guan Xuyang
  • WANG NANNAN

Assignees

  • 贞一绿碳(北京)能源科技有限公司

Dates

Publication Date
20260512
Application Date
20260119

Claims (10)

  1. 1. The method for preparing methane by utilizing anaerobic fermentation of straw is characterized by comprising the following steps: S1, mixing kitchen waste with anaerobic granular sludge, regulating pH to 5.5-6.2, and performing dark fermentation to prepare dark fermentation biogas slurry; s2, soaking and preprocessing the straws by using the dark fermentation biogas slurry in the step S1, and performing anaerobic fermentation on the preprocessed straws to produce methane.
  2. 2. The method for preparing methane by anaerobic fermentation of straw according to claim 1, wherein in the step S1, the organic load of the kitchen waste is 38-42 TS/L.
  3. 3. The method for preparing methane by anaerobic fermentation of straw according to claim 1 or 2, wherein in step S1, the anaerobic granular sludge is subjected to a thermal pretreatment at a temperature of 85-100 ℃, preferably 90-95 ℃, before the kitchen waste is mixed with the anaerobic granular sludge.
  4. 4. The method for preparing methane by anaerobic fermentation of straw according to claim 1 or 3, wherein in the step S1, the organic load ratio of the kitchen waste to the anaerobic granular sludge is 1 (1-2).
  5. 5. The method for preparing methane by anaerobic fermentation of straw according to claim 1 or 4, wherein in the step S1, the temperature of the dark fermentation hydrogen production is 34-36 ℃.
  6. 6. The method for preparing methane by anaerobic fermentation of straw according to claim 1 or 5, wherein in the step S1, the time for preparing hydrogen by dark fermentation is 22-28 h.
  7. 7. The method for preparing methane by anaerobic fermentation of straw according to claim 1 or 6, wherein in the step S2, the mass ratio of the straw to the dark fermentation biogas slurry is 1 (6-10).
  8. 8. The method for preparing methane by anaerobic fermentation of straw according to claim 1 or 7, wherein in the step S2, the specific condition of the soaking pretreatment is that the straw is soaked in the dark fermentation biogas slurry for 24-72 hours at 34-36 ℃.
  9. 9. The method for preparing methane by anaerobic fermentation of straw according to claim 1 or 8, wherein in the step S2, the specific conditions for anaerobic fermentation and methane production comprise mixing the pretreated straw with animal waste for anaerobic fermentation and methane production, and the organic load ratio of the straw to the animal waste before pretreatment is 1 (1-2).
  10. 10. The method for preparing methane by anaerobic fermentation of straw according to claim 1 or 9, wherein in the step S2, the specific conditions for anaerobic fermentation and methane production further comprise adjusting the pH of an anaerobic fermentation system to 7.5-8.2, and performing anaerobic fermentation and methane production at a fermentation temperature of 34-36 ℃.

Description

Method for preparing methane by anaerobic fermentation of straw Technical Field The invention relates to the technical field of biogas production methods, in particular to a method for preparing methane by utilizing anaerobic fermentation of straws. Background The main chemical component of straw biomass is lignocellulose, and the compact crystal structure of the straw biomass seriously hinders the digestion and degradation of anaerobic fermentation substrates, so that the problems of slow system start, long fermentation time and the like are caused. Therefore, more complex pretreatment steps are often required to improve the biodegradability of the substrate prior to anaerobic fermentation of straw-based feedstock. Existing pretreatment techniques include physical, chemical and biological methods. The physical pretreatment is to change the structure of the straw by grinding, crushing, extruding and other methods, reduce the polymerization degree of the straw to ensure that the straw is easy to decompose, generally has high equipment cost and high energy consumption, the chemical pretreatment is to break the covalent bond of lignocellulose by various chemical reagents and dissolve part of hemicellulose and lignin, thereby increasing the contact surface of cellulose and anaerobic microorganisms, improving the digestibility, generally requiring to purchase expensive chemical reagents, having high economic cost and easy secondary pollution, and in addition, the straw is required to be cleaned into neutrality after the pretreatment in order to avoid the residual chemical reagents inhibiting the activity of anaerobic fermentation microorganisms, and the biological pretreatment is to secrete enzymes for degrading the lignocellulose by specific microorganisms, so that the straw is easy to digest, has good degradation effect, no pollution and low cost, and has great development potential. The biogas slurry pretreatment is used as one of biological methods, is rich in various microorganisms capable of degrading lignocellulose, can recycle the biogas slurry, and effectively improves the hydrolytic acidification effect of the straw. However, at present, anaerobic fermentation biogas slurry is mostly utilized for soaking pretreatment, a microbial community is relatively single, after the microbial community is consumed in multiple methanogenesis stages, the concentration of partial nutrient components is low, and the effect of promoting the growth of methanogenesis bacteria is limited. Disclosure of Invention The invention aims to solve the problem of low methane yield in the prior art by preprocessing straw anaerobic fermentation by using biogas slurry, and provides a method for preparing methane by preprocessing straw by using dark fermentation to produce hydrogen and anaerobic fermentation so as to realize remarkable improvement of methane yield of straw. The invention provides a method for preparing methane by anaerobic fermentation of straw, which comprises the following steps: S1, mixing kitchen waste with anaerobic granular sludge, regulating pH to 5.5-6.2, and performing dark fermentation to prepare dark fermentation biogas slurry; s2, soaking and preprocessing the straws by using the dark fermentation biogas slurry in the step S1, and performing anaerobic fermentation on the preprocessed straws to produce methane. The term "TS" according to the invention means the total solids mass content and the term "VS" means the volatile solids mass content. Preferably, in step S1, the organic load of the kitchen waste is 38 to 42 TS/L. Further preferably, in step S1, the organic load of the kitchen waste is 40gTS/L. In the scheme, in the step S1, the organic load of the kitchen waste is controlled to be 40g TS/L, and in the process of preparing hydrogen by dark fermentation, not only can enough organic load be ensured to generate enough Volatile Fatty Acids (VFAs), but also the system rancidity caused by excessive organic load can be avoided, and the microbial activity is inhibited. Preferably, in step S1, the particle size of the kitchen waste is <5mm. Preferably, in step S1, the anaerobic granular sludge is subjected to a heat pretreatment at a temperature of 85 to 100 ℃, preferably 90 to 95 ℃, before the kitchen waste is mixed with the anaerobic granular sludge. In the scheme, in the step S1, before kitchen waste and anaerobic granular sludge are mixed, the anaerobic granular sludge is subjected to heat pretreatment, the temperature of the heat pretreatment is 85-100 ℃, and hydrogen-consuming microorganisms in the anaerobic granular sludge can be removed. Preferably, in step S1, the organic load ratio of the kitchen waste to the anaerobic granular sludge is 1 (1-2). Further preferably, in step S1, the organic load ratio of the kitchen waste to the anaerobic granular sludge is 1:1. Preferably, in step S1, the temperature of the dark fermentation hydrogen production is 34 to 36 ℃. Preferably, in step S1, the time for pr