Method for strengthening medium-high temperature anaerobic methane production

Abstract

The invention belongs to the technical field of organic solid waste recycling, and provides a method for strengthening medium-high temperature anaerobic methane production. According to the invention, the iron composite material is added into a medium-high temperature anaerobic biogas production system (including sludge and a substrate) for medium-high temperature biogas production; the iron composite material comprises zero-valent iron and an electric conductor (comprising gamma-Fe2O3 and / or Fe3O4). Zero-valent iron in the iron composite material can accelerate the organic matter degradation rate of microorganisms; the electric conductor can attract key medium-high temperature anaerobic active microorganisms (such as medium-high temperature syntrophic acetic acid oxidizing bacteria and methanogens) which are difficult to grow and enrich the key medium-high temperature anaerobic active microorganisms on the iron composite material, so that the loss of the key medium-high temperature anaerobic active microorganisms is avoided, and the methane production efficiency is improved; meanwhile, key medium-high-temperature anaerobic active microorganisms and zero-valent iron coexist on the iron composite material, so that the electron mass transfer path in the biogas production process is shortened, the electron transfer efficiency is improved, the organic matter degradation rate of the microorganisms is increased, and the biogas production efficiency is enhanced.

Description

Technical Field

[0001] The invention relates to the technical field of organic solid waste resource utilization, and in particular to a method for enhancing medium- and high-temperature anaerobic biogas production. Background Art

[0002] Anaerobic biogas production refers to the process in which organic matter is stabilized through the metabolic activities of microorganisms under controlled anaerobic conditions, while producing gases such as methane and carbon dioxide. Since it can produce a large amount of clean biogas energy while reducing waste, anaerobic biogas production is often used for the treatment and disposal of various organic wastes such as urban organic domestic waste, farm manure, agricultural organic waste, and sewage plant sludge.

[0003] In recent years, more and more research and engineering applications have focused on the development of technologies for efficient anaerobic biogas production in the transition zone between medium and high temperatures (“medium and high temperatures”, 41-49°C). At present, the efficiency of medium and high temperature anaerobic biogas production is low and needs to be further improved. Summary of the invention

[0004] In view of this, an object of the present invention is to provide a method for enhancing medium- and high-temperature anaerobic biogas production. The method provided by the present invention has high efficiency of medium- and high-temperature anaerobic biogas production.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0006] The present invention provides a method for enhancing medium- and high-temperature anaerobic biogas production, comprising the following steps:

[0007] Adding the iron composite material to the medium-high temperature anaerobic biogas production system to produce biogas at medium-high temperature;

[0008] The iron composite material comprises zero-valent iron and a conductor;

[0009] The conductor includes γ-Fe 2 O 3 and / or Fe 3 O 4 ;

[0010] The medium- and high-temperature anaerobic biogas production system comprises sludge and a substrate.

[0011] Preferably, the mass ratio of zero-valent iron to the conductor in the iron composite material is 1:1 to 1.44.

[0012] Preferably, the iron composite material further comprises a carrier, and the carrier comprises biochar; the mass ratio of zero-valent iron, the conductor and the carrier in the iron composite material is 1:1.42 to 2:28 to 30.

[0013] Preferably, the iron composite material is added in an amount of 0.1 to 10 wt % in the medium-high temperature anaerobic biogas production system.

[0014] Preferably, the solid content of the sludge is 3-10%; the substrate includes restaurant waste, kitchen waste, perishable waste leachate, livestock and poultry manure or straw.

[0015] Preferably, the medium-high temperature biogas production method includes batch production or continuous production.

[0016] Preferably, when the medium-high temperature biogas production method is batch production, in the medium-high temperature anaerobic biogas production system, the mass ratio of sludge to substrate is 1 to 6:1, calculated on a dry basis by the mass of volatile solids.

[0017] Preferably, the adding of the iron composite material to the medium- and high-temperature anaerobic biogas production system comprises the following steps: the iron composite material and sludge are first mixed to obtain a first mixed system; the first mixed system and the substrate are second mixed; the rotation speed of the first mixing is 10 to 20 r / min, and the time is greater than or equal to 1 hour; the rotation speed of the second mixing is 5 to 15 r / min, and the time is 4 to 6 hours.

[0018] Preferably, when the medium-high temperature biogas production mode is continuous production, the medium-high temperature biogas production is carried out in a medium-high temperature anaerobic biogas production reactor, and the filling amount of the sludge is 1 / 3 to 1 / 2 of the effective volume of the medium-high temperature anaerobic biogas production reactor; the hydraulic retention time of the substrate in the medium-high temperature anaerobic biogas production reactor is 2 to 4 days.

[0019] Preferably, during the medium-high temperature biogas production process, the iron-composite material is collected at the water outlet for reuse.

[0020] The invention provides a method for strengthening medium- and high-temperature anaerobic biogas production.

[0021] The inventors found that there are few types of microorganisms adapted to medium-high temperature anaerobic biogas production, and the key medium-high temperature anaerobic active microorganisms are all microorganisms with extremely long growth cycles such as syntrophic acetic acid oxidizing bacteria and methanogenic archaea, which leads to these key medium-high temperature anaerobic active microorganisms being easily lost with the sludge at a short residence time, causing the biogas production efficiency to decrease in stability, greatly limiting the efficiency of medium-high temperature anaerobic biogas production. The present invention adds an iron composite material to the medium-high temperature anaerobic biogas production system. The zero-valent iron in the iron composite material can accelerate electron transfer, thereby accelerating the rate at which microorganisms degrade organic matter; the conductor can attract key medium-high temperature anaerobic active microorganisms that are difficult to grow, and enrich them on the iron composite material, avoiding the loss of key medium-high temperature anaerobic active microorganisms and improving the biogas production efficiency; at the same time, the enriched key medium-high temperature anaerobic active microorganisms and zero-valent iron coexist on the iron composite material, shortening the electron mass transfer path in the biogas production process, improving the electron transfer efficiency, accelerating the rate at which microorganisms degrade organic matter, and enhancing the biogas production efficiency.

[0022] Furthermore, the iron composite material also includes a carrier, and the carrier includes biochar. Biochar is a conductive material, which can assist the conductor to attract key medium- and high-temperature anaerobic active microorganisms and promote the enrichment of key medium- and high-temperature anaerobic active microorganisms; at the same time, biochar has a porous structure, which can absorb a large amount of organic matter in the substrate, promote the efficiency of electron transfer, and thus enhance the biogas production efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 The Fe-γ-Fe 2 O 3 Composite material addition group, Fe-γ-Fe 2 O 3 -The effect diagram of medium and high temperature biogas production in the biomass charcoal composite material addition group and the blank control group;

[0024] Figure 2 The Fe-Fe of Example 3 3 O 4 Composite material addition group, Fe-Fe of Example 4 3 O 4 -The effect diagram of medium and high temperature biogas production in the biomass charcoal composite material addition group and the blank control group;

[0025] Figure 3 The diagram shows the effect of the iron composite material on microbial enrichment in Examples 1 to 4. DETAILED DESCRIPTION

[0026] Terminology explanation:

[0027] Food waste usually refers to food residues generated in the daily operation of the catering industry (such as restaurants and canteens), including but not limited to leftovers, food processing scraps, etc. Kitchen waste mainly comes from household food waste generated in the daily cooking process, such as leftovers, vegetable peels, fish bones, etc.

[0028] The present invention provides a method for enhancing medium- and high-temperature anaerobic biogas production, comprising the following steps:

[0029] Adding the iron composite material to the medium-high temperature anaerobic biogas production system to produce biogas at medium-high temperature;

[0030] The iron composite material comprises zero-valent iron and a conductor;

[0031] The conductor includes γ-Fe 2 O 3 and / or Fe 3 O 4 ;

[0032] The medium- and high-temperature anaerobic biogas production system comprises sludge and a substrate.

[0033] Unless otherwise specified, the raw materials used in the present invention are preferably commercially available products.

[0034] In the present invention, the iron composite material comprises zero-valent iron and a conductor; the conductor comprises γ-Fe 2 O 3 and / or Fe 3 O 4 The iron composite material preferably further comprises a carrier, and the carrier preferably comprises biomass charcoal. In a specific embodiment of the present invention, the iron composite material is preferably Fe-γ-Fe 2 O 3 Composite materials, Fe-γ-Fe 2 O 3 -Biomass carbon composites, Fe-Fe 3 O 4 Composite material or Fe-Fe 3 O 4 -Biomass charcoal composites.

[0035] In the present invention, when the iron composite material comprises zero-valent iron and a conductor, the mass ratio of the zero-valent iron to the conductor is preferably 1:1 to 1.44.

[0036] In the present invention, when the iron composite material comprises zero-valent iron, a conductor and a carrier, the mass ratio of the zero-valent iron, the conductor and the carrier is preferably 1:1.42 to 2:28 to 30.

[0037] In the present invention, the Fe-γ-Fe 2 O 3 The preparation method of the composite material preferably comprises the following steps: dissolving a soluble iron salt to obtain an iron salt solution; preparing NaBH 4 solution; the NaBH 4 The solution is added dropwise to the iron salt solution to perform a composite reaction (referred to as the first composite reaction) to obtain the Fe-γ-Fe 2 O 3 In the present invention, the soluble iron salt is preferably ferric chloride, and more preferably ferric chloride hexahydrate (FeCl 3 6H 2 O); the reagent for dissolving the soluble iron salt is preferably water, more preferably deionized water; the concentration of the iron salt solution is preferably 1 to 5 g / L, specifically preferably 1 g / L, 2 g / L, 3 g / L, 4 g / L or 5 g / L. In the present invention, the NaBH 4The concentration of the solution is preferably 10 to 20 g / L, and specifically preferably 10 g / L, 11 g / L, 12 g / L, 13 g / L, 14 g / L, 15 g / L, 16 g / L, 17 g / L, 18 g / L, 19 g / L or 20 g / L; the NaBH 4 The solvent of the solution is preferably water, more preferably deionized water; the NaBH 4 The method for preparing the solution preferably comprises the following steps: 4 Dissolve in water and stir to obtain the NaBH 4 The stirring time is preferably 0.2 to 1 h, and more preferably 0.2 h, 0.3 h, 0.5 h, 0.6 h or 1 h. In the present invention, the NaBH 4 The volume ratio of the solution and the iron salt solution is preferably 1 to 1.5:3, specifically preferably 1:3, 1.1:3, 1.2:3, 1.3:3, 1.4:3 or 1.5:3; the dropwise addition is preferably carried out in an ice-water atmosphere; the first composite reaction is preferably carried out in an ice-water atmosphere, the time of the first composite reaction is preferably 1 to 3 hours, specifically preferably 1 hour, 2 hours or 3 hours, and the first composite reaction is preferably carried out under static conditions; the time of the first composite reaction is from the NaBH 4 After the solution is added dropwise, the timing starts. After the first composite reaction, the present invention preferably further comprises: centrifuging the obtained first composite reaction liquid to obtain a solid; washing, drying, grinding and sieving the solid in sequence to obtain the Fe-γ-Fe 2 O 3 Composite material; the washing agent is preferably water, more preferably deionized water; the number of washing times is preferably 3 to 5 times; the drying is preferably vacuum drying, the vacuum drying temperature is preferably 100 to 110°C, specifically preferably 100°C, 105°C or 110°C, the time is preferably 1 to 3h, specifically preferably 1h, 2h or 3h; the mesh number of the sieve used for sieving is preferably 100 mesh.

[0038] In a specific embodiment of the present invention, the Fe-γ-Fe 2 O 3 The preferred method for preparing the composite material is as follows: (1) 9 g FeCl 3 6H 2 O was dissolved in 3L deionized water and stirred to obtain a ferric chloride solution; (2) 18g NaBH 4 Dissolve in 1.2L deionized water and stir for 0.5h to obtain NaBH 4 (3) In an ice bath, add 1.2L NaBH 4 The solution was added dropwise to the mixed 3L ferric chloride solution, NaBH 4After the solution was added dropwise, it was allowed to stand for 2 hours; (4) the reaction solution obtained in (3) was centrifuged to collect the solid; the solid was washed with deionized water for 3 to 5 times, vacuum dried at 105°C for 2 hours, and ground through a 100-mesh sieve to obtain Fe-γ-Fe 2 O 3 Composite materials.

[0039] In the present invention, the Fe-γ-Fe 2 O 3 The method for preparing the biomass-carbon composite material preferably comprises the following steps: mixing a soluble iron salt, a carbon material and water to obtain an iron-carbon system; preparing NaBH 4 solution; the NaBH 4 The solution is added dropwise to the iron-carbon system to undergo a composite reaction (referred to as the second composite reaction) to obtain the Fe-γ-Fe 2 O 3 - Biomass carbon composite material. In the present invention, the carbon material is preferably bamboo charcoal, and the particle size of the bamboo charcoal is preferably 100 mesh; the soluble iron salt is preferably ferric chloride, and more preferably ferric chloride hexahydrate (FeCl 3 6H 2 O); the water is preferably deionized water; in the iron-carbon system, the concentration of the soluble iron salt is preferably 1-5 g / L, specifically preferably 1 g / L, 2 g / L, 3 g / L, 4 g / L or 5 g / L; the concentration of the carbon material is preferably 5-10 g / L, specifically preferably 5 g / L, 6 g / L, 7 g / L, 8 g / L, 9 g / L or 10 g / L. In the present invention, the NaBH 4 The solvent, concentration and preparation method of the solution are preferably consistent with the above technical solution, which will not be repeated here. 4 The volume ratio of the solution to the iron-carbon system is preferably 1 to 1.5:3, specifically preferably 1:3, 1.1:3, 1.2:3, 1.3:3, 1.4:3 or 1.5:3; the dropwise addition is preferably carried out under an ice-water atmosphere; the second composite reaction is preferably carried out under an ice-water atmosphere, the time of the second composite reaction is preferably 1 to 3 hours, specifically preferably 1 hour, 2 hours or 3 hours, and the time of the second composite reaction is from NaBH 4 After the solution is added dropwise, the timing starts; the second composite reaction is preferably carried out under static conditions. After the second composite reaction, the present invention preferably further comprises: centrifuging the obtained second composite reaction liquid to obtain a solid; washing, drying, grinding and sieving the solid in sequence to obtain the Fe-γ-Fe 2 O 3-biomass charcoal composite material; the washing agent is preferably water, more preferably deionized water; the number of washings is preferably 3 to 5 times; the drying is preferably vacuum drying, the vacuum drying temperature is preferably 100 to 110°C, specifically preferably 100°C, 105°C or 110°C, the time is preferably 1 to 3h, specifically preferably 1h, 2h or 3h; the mesh size of the sieve used for screening is preferably 100 mesh.

[0040] In a specific embodiment of the present invention, the Fe-γ-Fe 2 O 3 -The preferred method for preparing the biomass carbon composite material is as follows: (1) 9g FeCl 3 6H 2 O and 18 g of 100-mesh bamboo charcoal were added to 3 L of deionized water and stirred for 4 h to obtain an iron-carbon system; (2) 18 g of NaBH 4 Dissolve fully in 1.2L deionized water and stir for 0.5h to obtain NaBH 4 (3) In an ice bath, add 1.2L NaBH 4 The solution was added dropwise to the mixed 3L iron-carbon system, NaBH 4 After the solution was added dropwise, it was allowed to stand for 2 hours; (4) the reaction solution obtained in (3) was centrifuged to collect the solid; the solid was washed with deionized water for 3 to 5 times, vacuum dried at 105°C, and ground through a 100-mesh sieve to obtain Fe-γ-Fe 2 O 3 -Biomass charcoal composites.

[0041] In the present invention, the Fe-Fe 3 O 4 The preparation method of the composite material preferably comprises the following steps: dissolving a soluble iron salt to obtain an iron salt solution; preparing NaBH 4 solution; the NaBH 4 The solution is added dropwise to the iron salt solution to carry out a composite reaction (referred to as the third composite reaction); after the composite reaction is completed, air is introduced into the composite reaction solution to obtain the Fe-Fe 3 O 4 Composite material. In the present invention, the raw material and concentration of the iron salt solution are preferably consistent with the above technical solution, which will not be repeated here. In the present invention, the NaBH 4 The solvent, concentration and preparation method of the solution are preferably consistent with the above technical solution, which will not be repeated here. 4The volume ratio of the solution and the iron salt solution is preferably consistent with the above technical solution, which will not be repeated here. In the present invention, the time of the third composite reaction is preferably 1 to 3 hours, and specifically preferably 1 hour, 2 hours or 3 hours; the time of the third composite reaction is from the NaBH 4 The timing starts after the solution is added dropwise. In the present invention, the air introduction flow rate is preferably 0.1-1 L / min, specifically preferably 0.1 L / min, 0.2 L / min, 0.3 L / min, 0.4 L / min, 0.5 L / min, 0.6 L / min, 0.7 L / min, 0.8 L / min, 0.9 L / min or 1 L / min; the air introduction time is preferably 1-3 h, specifically preferably 1 h, 2 h or 3 h. After the air is introduced, the present invention preferably further comprises: centrifuging the obtained reaction liquid to obtain a solid; washing, drying, grinding and sieving the solid in sequence to obtain the Fe-Fe 3 O 4 Composite material; the washing agent is preferably water, more preferably deionized water; the number of washing times is preferably 3 to 5 times; the drying is preferably vacuum drying, the vacuum drying temperature is preferably 100 to 110°C, specifically preferably 100°C, 105°C or 110°C, the time is preferably 1 to 3h, specifically preferably 1h, 2h or 3h; the mesh number of the sieve used for sieving is preferably 100 mesh.

[0042] In a specific embodiment of the present invention, the Fe-Fe 3 O 4 The preferred method for preparing the composite material is as follows: (1) 9 g FeCl 3 6H 2 O was dissolved in 3L of deionized water and stirred to obtain a ferric chloride solution; (2) 6g of NaBH 4 Dissolve in 1.2L deionized water and stir for 0.5h to obtain NaBH 4 (3) In an ice bath, add 1.2L NaBH 4 The solution was added dropwise to the mixed 3L ferric chloride solution, NaBH 4 After the solution was added dropwise, it was allowed to stand for 2 h; (4) air was then introduced into the mixed solution at a flow rate of 0.5 L / min for 2 h; (5) the reaction solution obtained in (4) was centrifuged to collect the solid; the solid was washed with deionized water for 3 to 5 times, vacuum dried at 105 °C for 2 h, and ground through a 100-mesh sieve to obtain Fe-Fe 3 O 4 Composite materials.

[0043] In the present invention, the Fe-Fe 3 O 4The method for preparing the biomass-carbon composite material preferably comprises the following steps: mixing a soluble iron salt, a carbon material and water to obtain an iron-carbon system; preparing NaBH 4 solution; the NaBH 4 The solution is added dropwise to the iron-carbon system to perform a composite reaction (referred to as the fourth composite reaction) to obtain a precursor; the precursor is calcined to obtain the Fe-Fe 3 O 4 -biomass carbon composite material. In the present invention, the raw materials, concentration and preparation method of the iron-carbon system are consistent with the above technical solution, which will not be repeated here. In the present invention, the NaBH 4 The solvent, concentration and preparation method of the solution are preferably consistent with the above scheme, which will not be repeated here. 4 The volume ratio of the solution and the iron-carbon system is preferably consistent with the above technical solution, which will not be repeated here. In the present invention, the time of the fourth composite reaction is preferably 1 to 3 hours, and specifically preferably 1 hour, 2 hours or 3 hours; the time of the fourth composite reaction is from the NaBH 4 The timing starts after the solution is added dropwise. In the present invention, the addition and the fourth composite reaction are preferably carried out under an ice-water atmosphere. After the fourth composite reaction, the present invention preferably further comprises: centrifuging the obtained fourth composite reaction liquid, drying the obtained solid, and obtaining a precursor. In the present invention, the calcination temperature is preferably 200-300°C, specifically preferably 200°C, 250°C or 300°C; the calcination atmosphere is preferably a nitrogen-air mixed system, and the volume ratio of the nitrogen-air mixed system is preferably 5:1; the calcination time is preferably 0.5-1.5h, specifically preferably 0.5h, 1h or 1.5h. After the calcination, the present invention preferably cools the obtained calcined material to room temperature, and then washes, dries, grinds and sieves in sequence; the washing agent is preferably water, and more preferably deionized water; the number of washings is preferably 3 to 5 times; the drying is preferably vacuum drying, the vacuum drying temperature is preferably 100 to 110°C, specifically preferably 100°C, 105°C or 110°C, the time is preferably 1 to 3h, specifically preferably 1h, 2h or 3h; the mesh number of the sieve used for sieving is preferably 100 mesh.

[0044] In a specific embodiment of the present invention, the Fe-Fe 3 O 4 -The preferred method for preparing the biomass carbon composite material is as follows: (1) 9 g FeCl 3 6H 2 O and 18 g of 100-mesh bamboo charcoal were added to 3 L of deionized water and stirred for 4 h to obtain an iron-carbon system; (2) 12 g of NaBH 4Dissolve fully in 1.2L deionized water and stir for 0.5h to obtain NaBH 4 (3) In an ice bath, add 1.2L NaBH 4 The solution was added dropwise to the mixed 3L iron-carbon system, NaBH 4 After the solution was added dropwise, the mixture was allowed to stand for 2 h; the obtained reaction solution was centrifuged to collect the solid; (4) the solid was calcined at 250 °C for 1 h in a nitrogen-air mixed atmosphere (5:1); (5) after cooling, the obtained product was washed with deionized water for 3 to 5 times, vacuum dried at 105 °C, and ground through a 100-mesh sieve to obtain Fe-Fe 3 O 4 -Biomass charcoal composites.

[0045] In the present invention, the zero-valent iron in the iron composite material can accelerate electron transfer and accelerate the rate of microbial degradation of organic matter; the presence of the conductor can attract key medium-high temperature anaerobic active microorganisms (such as medium-high temperature syntrophic acetic acid oxidizing bacteria and methanogenic methanogens) that are difficult to grow, and enrich them on the iron composite material, avoiding the loss of key medium-high temperature anaerobic active microorganisms and improving the efficiency of biogas production; the high enrichment rate of key medium-high temperature anaerobic active microorganisms strengthens the efficiency of electron transfer between microorganisms and improves the efficiency of medium-high temperature anaerobic biogas production; at the same time, the enrichment of key medium-high temperature anaerobic active microorganisms on the iron composite material, combined with the zero-valent iron of the iron composite material, the co-existence of the two on the iron composite material shortens the electron mass transfer path in the biogas production process, improves the electron transfer efficiency, and thus enhances the biogas production efficiency. Further, the iron composite material also includes a carrier, and the carrier includes biochar. Biochar is a conductive material that can assist conductors in attracting key medium- and high-temperature anaerobic active microorganisms and promote the enrichment of key medium- and high-temperature anaerobic active microorganisms; at the same time, the porous structure of biochar can adsorb a large amount of organic matter in the substrate, promote electron transfer efficiency, and thus enhance biogas production efficiency.

[0046] In the present invention, the addition amount of the iron composite material in the medium and high temperature anaerobic biogas production system is preferably 0.1-10wt%, specifically preferably 0.1wt%, 0.2wt%, 0.3wt%, 0.4wt%, 0.5wt%, 0.6wt%, 0.7wt%, 0.8wt%, 0.9wt%, 1wt%, 2wt%, 3wt%, 4wt%, 5wt%, 6wt%, 7wt%, 8wt%, 9wt% or 10wt%.

[0047] In the present invention, the medium-high temperature anaerobic biogas production system includes sludge and a substrate. In the present invention, the solid content of the sludge is preferably 3-10%, and specifically preferably 3%, 3.35%, 3.53%, 4%, 5%, 6%, 7%, 8%, 9% or 10%. In the present invention, the sludge is the sludge stably operated in the medium-high temperature anaerobic biogas production reactor; the sludge needs to correspond to the substrate to be treated, that is, when the substrate is food waste, the sludge is the sludge stably operated in the medium-high temperature anaerobic biogas production reactor of food waste.

[0048] In the present invention, the substrate preferably includes food waste, kitchen waste, perishable waste leachate, livestock and poultry manure or straw. In the present invention, the solid content of the substrate is preferably 10-20%, specifically preferably 10%, 11%, 11.38%, 11.46%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19% or 20%.

[0049] In the present invention, the solid content of the mixed system formed by the iron composite material and the medium-high temperature anaerobic biogas production system is preferably 3-10%, specifically preferably 3%, 4%, 5%, 6%, 7%, 8%, 9% or 10%.

[0050] In the present invention, the temperature of the medium-high temperature biogas production is preferably 41-49°C, specifically preferably 41°C, 42°C, 43°C, 44°C, 45°C, 46°C, 47°C, 48°C or 49°C.

[0051] In the present invention, the medium-high temperature biogas production method preferably includes batch production or continuous production.

[0052] In the present invention, when the medium-high temperature biogas production method is batch production, the mass ratio of sludge to substrate in the medium-high temperature anaerobic biogas production system is preferably 1 to 6:1, specifically preferably 1:1, 2:1, 3:1, 4:1, 5:1 or 6:1, calculated on a dry basis with respect to the mass of volatile solids.

[0053] In the present invention, when the medium-high temperature biogas production method is batch production, the addition of the iron-composite material to the medium-high temperature anaerobic biogas production system includes the following steps: the iron-composite material and sludge are first mixed to obtain a first mixed system; the first mixed system and the substrate are second mixed. In the present invention, the first mixing is preferably carried out under stirring conditions, the stirring method is preferably full mixing stirring, the rotation speed of the first mixing is preferably 10 to 20 r / min, and the time is preferably greater than or equal to 1h. In the present invention, the rotation speed of the second mixing is preferably 5 to 15 r / min, and the time is preferably 4 to 6h. In the present invention, the medium-high temperature biogas production is carried out in a medium-high temperature anaerobic biogas production reactor.

[0054] In the present invention, when the medium-high temperature biogas production mode is continuous production, the medium-high temperature biogas production is carried out in a medium-high temperature anaerobic biogas production reactor, and the filling amount of the sludge is preferably 1 / 3 to 1 / 2 of the effective volume of the medium-high temperature anaerobic biogas production reactor; the hydraulic retention time of the substrate in the medium-high temperature anaerobic biogas production reactor is preferably 2 to 4 days, and specifically preferably 3 days. In the present invention, when the medium-high temperature biogas production mode is continuous production, during the medium-high temperature biogas production process, the present invention preferably further includes: collecting iron composite materials at the outlet and recycling them to medium-high temperature biogas production; the collection method is preferably magnetic collection, and the magnetic collection method preferably includes an electromagnet or a magnetic drum. The present invention collects the iron composite materials in the effluent and reuses them to medium-high temperature anaerobic biogas production, which greatly reduces the loss of key medium-high temperature anaerobic active microorganisms such as syntrophic acetic acid oxidizing bacteria and methanogens, maintains the concentration of key medium-high temperature anaerobic active microorganisms and system stability in the medium-high temperature anaerobic biogas production process, and further improves the efficiency of medium-high temperature anaerobic biogas production; at the same time, the present invention uses γ-Fe 2 O 3 and / or Fe 3 O 4 As a conductor, it not only enhances the conductivity of the iron composite material, but also imparts magnetic properties, making it easier to recycle and achieve cost reduction and efficiency improvement.

[0055] In the present invention, when the medium-high temperature biogas production method is continuous production, the added iron composite material is always in contact with the sludge and the substrate entering the medium-high temperature anaerobic biogas production reactor; and in continuous production, the sludge and the substrate entering the medium-high temperature anaerobic biogas production reactor will fill the entire medium-high temperature anaerobic biogas production reactor; at this time, the addition amount of the iron composite material in the medium-high temperature anaerobic biogas production system refers to the system formed by the sludge and the substrate entering the medium-high temperature anaerobic biogas production reactor, and the size of this system is exactly the effective volume of the medium-high temperature anaerobic biogas production reactor; therefore, when the medium-high temperature biogas production method is continuous production, the addition amount of the iron composite material in the medium-high temperature anaerobic biogas production system also refers to: the addition amount of the iron composite material in the medium-high temperature anaerobic biogas production reactor, that is, the addition amount relative to the effective volume of the medium-high temperature anaerobic biogas production reactor.

[0056] The present invention uses an iron composite material with Fe as the core as a microbial directional enrichment carrier in the medium-high temperature biogas production process, which can effectively improve the enrichment efficiency of key medium-high temperature anaerobic active microorganisms such as medium-high temperature syntrophic acetic acid oxidizing bacteria and methanogens on the surface of the iron composite material, and directly improve the efficiency of medium-high temperature anaerobic biogas production by enhancing the efficiency of electron transfer between microorganisms. 2 O 3 and / or Fe 3 O 4, so that the iron composite material can be magnetically recovered; the present invention adopts a magnetic recovery method to collect the iron composite material in the medium and high temperature anaerobic digestion discharge material and the key medium and high temperature anaerobic active microorganisms enriched on the surface and return them to the medium and high temperature anaerobic digestion process, which greatly reduces the loss of key medium and high temperature anaerobic active microorganisms in the medium and high temperature anaerobic digestion process, maintains the concentration and system stability in the high temperature anaerobic digestion process, and further improves the efficiency of medium and high temperature anaerobic digestion; and reduces the use cost of magnetic materials, achieving cost reduction and efficiency improvement.

[0057] The method for enhancing medium- and high-temperature anaerobic biogas production provided by the present invention is described in detail below in conjunction with the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0058] Example 1

[0059] A method for strengthening medium-high temperature anaerobic biogas production, the specific method is:

[0060] The iron composite material is Fe-γ-Fe 2 O 3 Composite material, the preparation method is:

[0061] (1) 9 g FeCl 3 6H 2 O was dissolved in 3 L of deionized water and stirred to obtain a ferric chloride solution.

[0062] (2) 18 g NaBH 4 Dissolve in 1.2L deionized water and stir for 0.5h to obtain NaBH 4 Solution.

[0063] (3) In an ice bath, add 1.2 L NaBH 4 The solution was added dropwise to the mixed 3L ferric chloride solution, NaBH 4 After the solution was added, it was allowed to stand for 2 h.

[0064] (4) The reaction solution obtained in (3) was centrifuged to collect the solid; after washing with deionized water 5 times, it was vacuum dried at 105°C for 2 h and ground through a 100-mesh sieve to obtain Fe-γ-Fe 2 O 3 Composite material, wherein Fe and γ-Fe 2 O 3 The mass ratio is 1:1.44.

[0065] Fe-γ-Fe 2 O 3The composite material is added into a fully mixed (CSTR) medium-high temperature anaerobic digestion system of food waste at an addition amount of 0.5wt%. The system uses the stably operated sludge in the medium-high temperature anaerobic digestion reactor of food waste as inoculum (total solid content is 3.35-3.53%, and the volatile solid content in dry basis is 40.81-41.56%), and uses food waste as substrate (total solid content is 11.38-11.46%, and 83.87-84.94% in dry basis). The mass ratio of the inoculum to the substrate is 1:1 based on the mass of the volatile solids in the dry basis. The enhanced effect of methane production by anaerobic digestion of food waste is verified at 45°C.

[0066] The specific operation is: Fe-γ-Fe 2 O 3 The composite material was added into the high-temperature anaerobic biogas reactor of food waste (the high-temperature anaerobic biogas reactor of food waste contained stable running sludge), and stirred at 15r / min for 1h to achieve the sludge and Fe-γ-Fe 2 O 3 The composite material was mixed; kitchen waste was added continuously and stirred at 10 r / min for 5 h; the solid content of the mixed system was 4.40%; and biogas production was carried out at a medium-high temperature of 45°C. 2 O 3 The composite material served as the blank control group.

[0067] Fe-γ-Fe of Example 1 2 O 3 The results of medium and high temperature biogas production in the composite material addition group and the blank control group are shown in the figure below. Figure 1 As shown. Figure 1 It can be seen that the cumulative methane production of the blank control group is 79.53mL / gVS added , Fe-γ-Fe 2 O 3 The cumulative methane production of the composite material addition group was 86.36 mL / gVS added Compared with the blank control group, Fe-γ-Fe 2 O 3 The cumulative methane production in the composite material addition group increased significantly by 8.59%.

[0068] After 7 days of medium-high temperature biogas production, the microbial enrichment effect was tested. The specific process is as follows:

[0069] (1) Take 20 mL of reactor sludge sample and add it to a 50 mL sterile centrifuge tube;

[0070] (2) Use a strong magnet to stick to the outer wall of the centrifuge tube, and repeatedly and slowly shake the centrifuge tube to fully adsorb the iron composite material in the sample to the centrifuge tube wall where the magnet is located, and pour all the unabsorbed sample parts into a new sterile centrifuge tube;

[0071] (3) Repeat the operation in (2) for 4 times for the unabsorbed sample until the magnetic substance in the unabsorbed sample is basically completely adsorbed;

[0072] (4) The sample part of the iron composite material and the remaining unadsorbed sample part were subjected to real-time fluorescence quantitative PCR (qPCR) analysis of two functional genes, mcrA (for methanogenic microorganisms) and FTHFS (for syntrophic acetic acid oxidizing microorganisms), to determine the spatial distribution ratio of methanogenic microorganisms and syntrophic acetic acid oxidizing microorganisms loaded on the iron composite material and suspended in the fermentation broth in each experiment. Figure 3 shown.

[0073] The amplification primers for the mcrA gene are ME3MF (5′-ATGTCNGGTGGHGTMGGSTTYAC-3′, SEQ ID NO.1) and ME2′R (5′-TCATBGCRTAGTTDGGRTAGT-3′, SEQ ID NO.2), and the amplification primers for the FTHFS gene are FTHFSF (5′-TTYACWGGHGAYTTCCATGC-3′, SEQ ID NO.3) and FTHFSR (5′-GTATTGDGTYTTRGCCATACA-3′, SEQ ID NO.4), wherein M=A / C, N=A / G / T / C, S=G / C, B=G / T / C; Y=C / T, W=A / T, R=A / G, H=A / C / T, D=A / G / T).

[0074] from Figure 3 It can be seen that Fe-γ-Fe 2 O 3 The composite material (added at 0.5wt%) enriched 22.35% of methanogenic archaea and 0.61% of syntrophic acetic acid oxidizing bacteria in the entire system. This shows that the iron composite material can effectively promote the enrichment of medium- and high-temperature key microorganisms on the surface of the iron composite material and enhance the methane production efficiency of anaerobic digestion of food waste.

[0075] Example 2

[0076] A method for strengthening medium-high temperature anaerobic biogas production, the specific method is:

[0077] The iron composite material is Fe-γ-Fe 2 O 3 -Biomass carbon composite material, the preparation method is:

[0078] (1) 9 g FeCl 3 6H 2 O and 18 g of 100-mesh bamboo charcoal were added into 3 L of deionized water and stirred for 4 h to obtain an iron-carbon system.

[0079] (2) 18 g NaBH 4 Dissolve fully in 1.2L deionized water and stir for 0.5h to obtain NaBH 4 Solution.

[0080] (3) In an ice bath, add 1.2 L NaBH 4 The solution was added dropwise to the mixed 3L iron-carbon system, NaBH 4 After the solution was added dropwise, it was allowed to stand for 2 h.

[0081] (4) The reaction solution obtained in (3) was centrifuged to collect the solid; the obtained product was washed with deionized water 5 times, vacuum dried at 105° C., and ground through a 100-mesh sieve to obtain Fe-γ-Fe 2 O 3 -Biomass carbon composite material, wherein Fe, γ-Fe 2 O 3 The mass ratio of carbon to biochar is 1:1.42:28.

[0082] Fe-γ-Fe 2 O 3 -The biomass carbon composite material was added to the CSTR food waste medium- and high-temperature anaerobic digestion system at an addition amount of 0.5wt%. The system used the stable operating sludge in the food waste medium- and high-temperature anaerobic digestion reactor as the inoculum (the total solid content was 3.35% to 3.53%, and the volatile solid content on a dry basis was 40.81% to 41.56%), and the food waste as the substrate (the total solid content was 11.38% to 11.46%, and the volatile solid content on a dry basis was 83.87% to 84.94%). The mass ratio of the inoculum to the substrate was 1:1 based on the mass of the volatile solids on a dry basis. The enhanced effect of anaerobic digestion of food waste on methane production was verified at 45°C.

[0083] The specific operation is: Fe-γ-Fe 2 O 3 - The biomass carbon composite material was added into the high temperature anaerobic digestion reactor of food waste (the high temperature anaerobic digestion reactor of food waste contains stable running sludge), and stirred at 15r / min for 1h to achieve the sludge and Fe-γ-Fe 2 O 3 -mixing of biomass-carbon composite materials; continuing to add food waste and stirring at 10r / min for 5h; the solid content of the formed mixed system is 4.40%; medium-high temperature biogas production is carried out at 45°C.

[0084] Fe-γ-Fe of Example 2 2 O 3 -The effect of medium and high temperature biogas production in the biomass charcoal composite material adding group is shown in the figure Figure 1 As shown, from Figure 1 It can be seen that the cumulative methane production of the blank control group is 79.53mL / g VS added , Fe-γ-Fe 2 O 3 -The cumulative methane production of the biochar composite material group was 105.35mL / gVS added Compared with the blank control group, Fe-γ-Fe 2 O 3 -The cumulative methane production of the biomass carbon composite magnetic material addition group increased significantly by 32.46%.

[0085] The microbial enrichment effect was tested according to the method of Example 1. The results are as follows Figure 3 As shown, from Figure 3 It can be seen that Fe-γ-Fe 2 O 3 The composite material (added at 0.5wt%) enriched 44.04% of methanogenic archaea and 11.40% of syntrophic acetic acid oxidizing bacteria in the entire system. This shows that the iron composite material can effectively promote the enrichment of medium- and high-temperature key microorganisms on the surface of the iron composite material and enhance the methane production efficiency of anaerobic digestion of food waste.

[0086] Example 3

[0087] A method for strengthening medium-high temperature anaerobic biogas production, the specific method is:

[0088] Iron composite material is Fe-Fe 3 O 4 Composite material, the preparation method is:

[0089] (1) 9 g FeCl 3 6H 2 O was dissolved in 3 L of deionized water and stirred to obtain a ferric chloride solution.

[0090] (2) 6gNaBH 4 Dissolve in 1.2L deionized water and stir for 0.5h to obtain NaBH 4 Solution.

[0091] (3) In an ice bath, add 1.2 L NaBH 4 The solution was added dropwise to the mixed 3L ferric chloride solution, NaBH 4 After the solution was added dropwise, it was allowed to stand for 2 h.

[0092] (4) Then, air was introduced into the mixed solution at a flow rate of 0.5 L / min for 2 h;

[0093] (5) The reaction solution obtained in (4) was centrifuged to collect the solid; after washing with deionized water for 3 to 5 times, it was vacuum dried at 105° C. for 2 h, and ground through a 100-mesh sieve to obtain Fe-Fe 3 O 4 Composite materials, in which Fe and Fe 3 O 4 The mass ratio is 1:1.

[0094] Will Fe-Fe 3 O 4 The composite material (the addition amount relative to the effective volume of the medium-temperature anaerobic digestion reactor of perishable landfill leachate is 1wt%) is added to the medium-temperature anaerobic digestion CSTR system of perishable landfill leachate. The system uses the stably operated sludge in the medium-temperature anaerobic digestion reactor of perishable landfill leachate as inoculum (the sludge occupies 1 / 3 of the effective volume of the reactor, and the total solid content is 4.02-6.24%), and the perishable landfill leachate as substrate (COD is 20283-23167 mg / L, and the water inlet is 3275-3500 mL / d). The enhanced effect of anaerobic digestion of perishable landfill leachate on methane production is continuously verified at 45°C, the daily hydraulic retention time of the inlet and outlet water is 3 days, and the magnetic sludge in the effluent water is collected by an electromagnet and then re-injected into the reactor with the influent water.

[0095] In the specific process: Fe-Fe 3 O 4 The composite material was added into a medium-high temperature anaerobic digestion reactor for perishable landfill leachate (filled with stable sludge from the medium-high temperature anaerobic digestion reactor for perishable landfill leachate, and the sludge accounted for 1 / 3 of the effective volume of the reactor), the substrate was introduced from the water inlet, and the liquid after medium-high temperature digestion was discharged from the water outlet. By controlling the flow rates of the water inlet and the water outlet, the hydraulic retention time of the substrate in the medium-high temperature anaerobic digestion reactor for perishable landfill leachate was 3 days. At the same time, the magnetic sludge in the effluent was collected by an electromagnet and then re-injected into the medium-high temperature anaerobic digestion reactor for perishable landfill leachate with the inlet water, and the medium-high temperature anaerobic digestion was measured without adding Fe-Fe. 3 O 4 The composite material was used as a blank control group; the Fe-Fe 3 O 4 The results of medium-high temperature biogas production in the composite material addition group and the blank control group are as follows: Figure 2 shown.

[0096] from Figure 2 It can be seen that during the 20 days of relatively stable operation starting from the 8th day, the average daily methane production rate of the blank control group was 162.51 mL / g COD, and the Fe-Fe3 O 4 The average daily methane production rate of the composite material addition group was 195.29 mL / g COD. Compared with the blank control group, the Fe-Fe 3 O 4 The average daily methane production rate of the composite material addition group increased significantly by 20.17%.

[0097] The microbial enrichment effect was tested according to the method of Example 1. The results are as follows Figure 3 As shown, from Figure 3 It can be seen that Fe-γ-Fe 3 O 4 The composite material (added at 1wt%) enriched 26.64% of methanogenic archaea and 3.18% of syntrophic acetic acid oxidizing bacteria in the whole system. This shows that the iron composite material can effectively promote the enrichment of medium- and high-temperature key microorganisms on the surface of the iron composite material and enhance the methanogenic efficiency of medium- and high-temperature anaerobic digestion of perishable landfill leachate.

[0098] Example 4

[0099] A method for strengthening medium-high temperature anaerobic biogas production, the specific method is:

[0100] Iron composite material is Fe-Fe 3 O 4 -Biomass carbon composite material, the preparation method is:

[0101] (1) 9 g FeCl 3 6H 2 O and 18 g 100 mesh bamboo charcoal were added into 3 L deionized water and stirred for 4 h.

[0102] (2) 12 g NaBH 4 Dissolve fully in 1.2L deionized water and stir for 0.5h to obtain NaBH 4 Solution.

[0103] (3) In an ice bath, add 1.2 L NaBH 4 The solution was added dropwise to the mixed 3L solution, and NaBH 4 After the solution was added dropwise, it was allowed to stand for 2 hours, and the obtained reaction solution was centrifuged to collect the solid.

[0104] (4) The solid was calcined at 250 °C for 1 h in a nitrogen-air mixed atmosphere (5:1).

[0105] (5) After cooling, the obtained product was washed with deionized water for 3 to 5 times, dried under vacuum at 105°C, and ground through a 100-mesh sieve to obtain Fe-Fe 3 O 4 -Biomass carbon composite material, wherein Fe, Fe 3O 4 The mass ratio of carbon to biochar is 1:2:30.

[0106] Will Fe-Fe 3 O 4 -Biomass carbon composite material (the addition amount relative to the effective volume of the medium-temperature anaerobic digestion reactor of perishable landfill leachate is 1wt%) is added to the medium-temperature anaerobic digestion system of CSTR perishable landfill leachate. The system uses the stable operating sludge in the medium-temperature anaerobic digestion reactor of perishable landfill leachate as inoculum (the inoculum sludge accounts for 1 / 3 of the total volume of the reactor, and the total solid content is 4.02-6.24%), and the perishable landfill leachate as substrate (COD is 20283-23167 mg / L, and the water inlet is 3275-3500 mL / d). The enhanced effect of anaerobic digestion of perishable landfill leachate on methane production is continuously verified at 45°C, with water inlet and outlet every day, and the hydraulic retention time is 3 days. The magnetic sludge in the effluent is collected by an electromagnet and then re-injected into the reactor with the influent.

[0107] In the specific process: Fe-Fe 3 O 4 - The biomass carbon composite material was added to a medium-high temperature anaerobic digestion reactor for perishable landfill leachate (filled with stable sludge in the medium-high temperature anaerobic digestion reactor for perishable landfill leachate, and the sludge accounted for 1 / 3 of the effective volume of the reactor), the substrate was introduced from the water inlet, and the liquid after medium-high temperature digestion was discharged from the water outlet. By controlling the flow rates of the water inlet and the water outlet, the hydraulic retention time of the substrate in the medium-high temperature anaerobic digestion reactor for perishable landfill leachate was 3 days; at the same time, the magnetic sludge in the effluent was collected by an electromagnet and then re-injected into the medium-high temperature anaerobic digestion reactor for perishable landfill leachate with the inlet water, and the medium-high temperature anaerobic digestion situation was measured. The Fe-Fe 3 O 4 -The results of the medium and high temperature biogas production in the biomass charcoal composite material group are as follows Figure 2 As shown. Figure 2 It can be seen that during the 20 days of relatively stable operation starting from the 8th day, the average daily methane production rate of the blank control group was 162.51 mL / g COD, and the Fe-Fe 3 O 4 -The average daily methane production rate of the biomass carbon composite material group was 225.26mL / g COD, compared with the blank control group, the Fe-Fe 3 O 4 -The average daily methane production rate of the biochar composite material addition group increased significantly by 38.61%.

[0108] The microbial enrichment effect was tested according to the method of Example 1. The results are as follows Figure 3 As shown, from Figure 3 It can be seen that Fe-γ-Fe3 O 4 The composite material (added at 1wt%) enriched 48.96% of methanogenic archaea and 15.32% of syntrophic acetic acid oxidizing bacteria in the whole system. This shows that the iron composite material can effectively promote the enrichment of medium- and high-temperature key microorganisms on the surface of the iron composite material and enhance the methanogenic efficiency of medium- and high-temperature anaerobic digestion of perishable landfill leachate.

[0109] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for strengthening medium- and high-temperature anaerobic biogas production, characterized in that: The following steps are involved: Adding the iron composite material to the medium-high temperature anaerobic biogas production system to produce biogas at medium-high temperature; The iron composite material comprises zero-valent iron and a conductor; The electrical conductor includes γ-Fe2O3 and / or Fe3O4; The medium- and high-temperature anaerobic biogas production system comprises sludge and a substrate.

2. The method according to claim 1, characterized in that The mass ratio of zero-valent iron to the conductor in the iron composite material is 1:1-1.

44.

3. The method according to claim 1, characterized in that The iron composite material also includes a carrier, and the carrier includes biomass charcoal; the mass ratio of zero-valent iron, conductor and carrier in the iron composite material is 1:1.42-2:28-30.

4. The method according to claim 1, characterized in that: The iron composite material is added in an amount of 0.1 to 10 wt % in the medium-high temperature anaerobic biogas production system.

5. The method according to claim 1, characterized in that The solid content of the sludge is 3-10%; the substrate includes restaurant waste, kitchen waste, perishable waste leachate, livestock and poultry manure or straw.

6. The method according to claim 1, characterized in that The medium-high temperature biogas production method includes batch production or continuous production.

7. The method according to claim 6, characterized in that When the medium-high temperature biogas production method is batch production, in the medium-high temperature anaerobic biogas production system, the mass ratio of sludge to substrate is 1 to 6:1, calculated on a dry basis by the mass of volatile solids.

8. The method according to claim 7, characterized in that The method of adding the iron composite material to the medium-high temperature anaerobic biogas production system comprises the following steps: first mixing the iron composite material and sludge to obtain a first mixed system; second mixing the first mixed system and a substrate; the first mixing speed is 10 to 20 r / min, and the time is greater than or equal to 1 hour; the second mixing speed is 5 to 15 r / min, and the time is 4 to 6 hours.

9. The method according to claim 6, characterized in that When the medium-high temperature biogas production method is continuous production, the medium-high temperature biogas production is carried out in a medium-high temperature anaerobic biogas production reactor, and the filling amount of the sludge is 1 / 3 to 1 / 2 of the effective volume of the medium-high temperature anaerobic biogas production reactor; the hydraulic retention time of the substrate in the medium-high temperature anaerobic biogas production reactor is 2 to 4 days.

10. The method according to claim 9, characterized in that During the medium-high temperature biogas production process, the iron composite material is collected at the water outlet for reuse.

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