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CN-115710076-B - Method and device for producing methane by anaerobic fermentation of sludge based on pretreatment of free ammonia

CN115710076BCN 115710076 BCN115710076 BCN 115710076BCN-115710076-B

Abstract

The invention provides an in-situ biogas upgrading method and device for producing methane by anaerobic fermentation of sludge based on free ammonia pretreatment, wherein the method comprises the steps of adding a free ammonia preparation solution into sludge to be pretreated of a pretreatment unit, enabling the concentration of the free ammonia to reach 500-1500 mg/L, treating for 12-36 hours to obtain a fermentation substrate with the pH value of about 6.5-8.3, and inputting the fermentation substrate pretreated by the free ammonia into an anaerobic bioreactor for fermentation so as to produce biological natural gas mainly comprising methane. The method is implemented based on the principle that free ammonia damages the concentration balance of protons and potassium ions inside and outside cells in a fermentation matrix, accelerates the dissolution of organic matters in the cells of sludge in pretreatment and hydrolysis stages, improves the release amount of soluble organic matters and the release amount of total organic matters, and further utilizes the principle that the free ammonia specifically regulates and controls the hydrogen nutrition type methane production path to cooperatively improve the methane concentration and yield of methane.

Inventors

  • YU DAWEI
  • SHEN JIAHUI
  • WEI YUANSONG
  • LIN XINYU
  • GUO XINYU
  • Sun Guanlai

Assignees

  • 中国科学院生态环境研究中心

Dates

Publication Date
20260508
Application Date
20221116

Claims (7)

  1. 1. An in-situ methane upgrading method for producing methane by anaerobic fermentation of sludge based on free ammonia pretreatment is characterized by comprising the following steps: adding a free ammonia preparation solution into sludge to be pretreated of a pretreatment unit, wherein the pH value of the free ammonia preparation solution is 8.05-8.35, the concentration of free ammonia is 200-1500 mg/L, standing for 12-36 hours after the concentration of free ammonia reaches 200-1500 mg/L to obtain a fermentation substrate with the pH value of 6.5-8.3 and the concentration of free ammonia of 380-580 mg/L, and Inputting the fermentation substrate into an anaerobic bioreactor inoculated with anaerobic digested sludge for fermentation to generate methane-based biogas; Delivering the effluent in the anaerobic bioreactor to a biological membrane tank to continue fermentation, and separating the effluent from sludge in the biological membrane tank to realize sludge recycling and biogas production; delivering biogas in the anaerobic bioreactor to the biofilm tank to further absorb carbon dioxide in the biogas and perform aeration on a membrane component of the biofilm tank to control membrane pollution, and Returning the biogas in the biological membrane tank to the anaerobic bioreactor again through a gas circulation inlet of the anaerobic bioreactor to form circulation of the biogas and circulation interception and absorption of carbon dioxide in the biogas, wherein the gas circulation inlet is positioned at the bottom of the anaerobic bioreactor.
  2. 2. The method of claim 1, wherein the free ammonia modulating solution comprises free ammonia and at least one base selected from the group consisting of sodium hydroxide and potassium hydroxide.
  3. 3. The method of claim 2, wherein the free ammonia is derived from ammonium chloride or anaerobic digester effluent from sewage treatment.
  4. 4. The method according to claim 2, wherein the pretreatment is performed at a temperature of 20 ℃ to 40 ℃ for 12 to 36 hours.
  5. 5. The method of claim 1, wherein the step of determining the position of the substrate comprises, Adding the free ammonia preparation solution into sludge to be pretreated of a pretreatment unit, and carrying out standing treatment for 12-36 hours to obtain a fermentation substrate with a pH value of 6.5-8.3 and a free ammonia concentration of 380-580 mg/L, wherein the preparation method comprises the following steps: adding the free ammonia preparation solution into sludge to be pretreated of a pretreatment unit to obtain a pretreatment substrate with pH of 7.5-8.6 and free ammonia concentration of 200-1500 mg/L; And standing the pretreated substrate at 20-40 ℃ for 12-36 h to obtain the fermentation substrate with the pH value of 6.5-8.3 and the free ammonia concentration of 380-580 mg/L.
  6. 6. The method of claim 1, wherein the step of determining the position of the substrate comprises, Before the fermentation substrate is input into the anaerobic bioreactor inoculated with anaerobic digested sludge for fermentation, the method further comprises: And (3) introducing inert gas into the anaerobic bioreactor after the standing treatment to enable the fermentation substrate to be in an anaerobic state.
  7. 7. The method according to claim 1, wherein the anaerobic digestion sludge is granular sludge subjected to ammonia nitrogen inhibition domestication, and the sludge to be pretreated is concentrated sludge from a sedimentation tank in sewage treatment.

Description

Method and device for producing methane by anaerobic fermentation of sludge based on pretreatment of free ammonia Technical Field The invention relates to the technical field of solid waste recycling and new energy, in particular to an in-situ biogas upgrading method and device for producing methane by anaerobic fermentation of sludge based on free ammonia pretreatment. Background In the urban water environment treatment process, the harmless treatment rate of the urban sludge reaches 90 percent. With the continuous upgrading of treatment technology and the development and change of novel energy sources, urban sludge recycling is becoming a new focus. Biogas is produced through anaerobic fermentation degradation of organic matters in sludge, can partially replace renewable energy sources of natural gas and fossil fuel, and provides various applications in heat supply and power generation and as vehicle fuel. At present, the generation of methane through anaerobic fermentation is the first technical approach of municipal sludge resources, but because organic matters in the sludge are encapsulated by extracellular polymers and are bound by cell walls, the organic matters are difficult to utilize and convert into methane, and the low methane yield and concentration limit the sludge recycling and high-value utilization. In the existing sludge recycling technology, the method for accelerating the dissolution of organic matters and strengthening the methane production through sludge pretreatment is still a key core technology for improving the methane yield and realizing sludge recycling. At present, the method for improving the methane yield is mainly focused on the research of sludge pretreatment technology. The methane yield can be effectively improved through the high-temperature thermal hydrolysis pretreatment of the sludge, but the requirement on the equipment process level is high and the initial investment is large. The pretreatment can effectively destroy the extracellular polymer, the cell wall and other protective substances of the sludge to realize cell lysis and wall breaking, promote the release of intracellular and extracellular organic matters, and improve the hydrolysis rate and biodegradability of the sludge, thereby accelerating the reaction and anaerobic digestion process and finally improving the methane yield. However, most pretreatment methods still need to input a large amount of energy or chemicals, so that the recovery benefit of the sludge is reduced, and the large-scale application is hindered. Disclosure of Invention In order to at least partially solve at least one of the technical defects, the embodiment of the invention mainly provides an in-situ biogas upgrading method and device for producing methane by anaerobic fermentation of sludge based on pretreatment of free ammonia, which promote release of intracellular small molecular organic matters of the extracellular polymers under the action of ammonia osmotic pressure by promoting concentration balance of protons and potassium ions inside and outside extracellular polymers of the organic matters in a fermentation matrix to accelerate dissolution of the organic matters in a hydrolysis stage. In order to achieve the above purpose, as an embodiment of one aspect of the invention, an in-situ biogas upgrading method for producing methane based on anaerobic fermentation of sludge pretreated by free ammonia is provided, which comprises the steps of adding a free ammonia preparation solution into sludge to be pretreated of a pretreatment unit, standing for 12-36 h after the concentration of the free ammonia reaches 200-1500 mg/L to obtain a fermentation substrate with a pH value of 6.5-8.3 and a concentration of the free ammonia of 380-580 mg/L, and inputting the fermentation substrate into an anaerobic bioreactor inoculated with anaerobic digested sludge for fermentation to produce biogas mainly comprising methane (the volume occupation area is larger than 80-85%). As another embodiment of the invention, an in-situ biogas upgrading method for carrying out the sludge anaerobic fermentation methane production based on free ammonia pretreatment is provided, which comprises a pretreatment unit, an anaerobic bioreactor, a water inlet of the anaerobic bioreactor and a water outlet of the pretreatment unit, wherein the pretreatment unit is suitable for adding a free ammonia preparation solution into sludge to be pretreated, standing for 12-36 hours after the free ammonia concentration reaches 200-1500 mg/L to obtain a fermentation substrate with a pH value of 6.5-8.3 and the free ammonia concentration of 380-580 mg/L, and the anaerobic bioreactor is suitable for receiving the fermentation substrate of the pretreatment unit and inoculating anaerobic digested sludge to ferment the fermentation substrate to produce biogas with methane as a main component (the volume is more than 80-85 percent). According to the in-situ methane upgrading method and