Preparation of modified carbon material and application of modified carbon material in enhancing high-concentration anaerobic digestion of organic waste to produce hydrogen-suitable feed gas
Iron-modified carbon materials were prepared by a one-pot hydrothermal carbonization reaction, and added to the anaerobic digestive substrate to alleviate ammonia inhibition and promote methane generation, which solved the problem that existing modified carbon materials could not effectively improve the methane production performance of anaerobic digestive substrates that were greatly affected by ammonia inhibition, and achieved efficient methane generation and low-cost recovery of materials.
Patent Information
- Application Number
- CN202411739781.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2024-11-26
- Filing Date
- 2024-11-29
- Publication Date
- 2025-03-21
AI Technical Summary
Existing modified carbon materials cannot effectively improve the methane production performance of anaerobic digestive substrates that are greatly affected by ammonia inhibition.
Iron-modified carbon material with rich porous structure and high specific surface area was prepared by performing a one-pot hydrothermal carbonization reaction of biomass waste, Fe6+ source and water, and was added to the anaerobic digestive substrate to alleviate ammonia inhibition and promote methane generation.
The methane yield and generation rate of anaerobic digestion are significantly improved, the anaerobic digestion cycle is shortened, and the magnetic properties of the material are easy to separate and recycle, with the advantages of low cost and high efficiency.
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Figure CN119660734A_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of carbon material preparation and organic waste treatment, and more specifically, relates to the preparation of modified carbon materials and their application in enhancing high-concentration anaerobic digestion of organic waste to produce hydrogen-suitable feed gas. Background Art
[0002] As an effective means of treating organic waste, anaerobic digestion technology not only promotes the recovery of clean energy biogas (rich in methane and carbon dioxide), but also realizes the resource utilization of biogas residue, a nutrient, showing significant green technology advantages. However, the biogas industry currently faces two core challenges: one is the low value of biogas products, and the other is the dilemma of large biogas slurry production and high difficulty in processing. These two major problems seriously restrict the further development of the biogas industry.
[0003] In response to the low-value biogas problem, biogas reforming and conversion technology, especially the conversion of methane into hydrogen, is seen as a key way to increase the value of biogas and promote carbon dioxide emission reduction, with potential economic and environmental benefits. On the other hand, biogas slurry is rich in nutrients but also contains antibiotic residues. Its high treatment cost means that most biogas slurry cannot be properly utilized, and the treatment and resource utilization of biogas slurry has become a problem that needs to be solved urgently.
[0004] In order to promote the sustainable development of the biogas industry, high-concentration anaerobic digestion technology has attracted much attention because it can increase the volumetric gas production rate and reduce the generation of biogas slurry. However, when treating high-nitrogen raw materials (such as livestock and poultry manure and food waste), the high-concentration anaerobic digestion process is easily inhibited by intermediates such as ammonia nitrogen and volatile fatty acids, resulting in reduced methanogen activity, impaired system stability, and a significant decrease in methane production and production rate.
[0005] In response to acid inhibition or ammonia inhibition, mixed anaerobic digestion has a certain effect, but it is accompanied by the large-scale production of scum and sludge. Therefore, exploring the application of exogenous promoters such as clay minerals, hydrochar and other modified carbon-based materials to optimize the anaerobic digestion performance of organic waste has become a research hotspot. Among them, hydrochar is highly favored due to its wide range of raw materials, simple preparation and low cost. Its porous structure provides an ideal attachment environment for microorganisms, and the rich surface functional groups help alleviate the accumulation of volatile acids under ammonia stress through the direct electron transfer (DIET) mechanism.
[0006] Although studies have reported on the use of pig manure (pig manure is a nitrogen-rich substrate, but less affected by ammonia inhibition) digestate FeSO4 modification, anaerobic digestion homologous raw materials KOH modification, biomass waste ball milling modification and other methods to enhance anaerobic digestion, these technologies mainly focus on the modified carbon materials prepared by the two-step method and are aimed at improving the methanogenic performance under conditions of no ammonia or low ammonia inhibition. These modified carbon materials cannot effectively improve the methanogenic performance of anaerobic digestion substrates that are greatly affected by ammonia inhibition (such as chicken manure).
[0007] Therefore, there is an urgent need to develop a new type of modified carbon material to effectively alleviate ammonia inhibition and improve methane production efficiency. Summary of the invention
[0008] The technical problem to be solved by the present invention is to overcome the defects and shortcomings of the existing technology that mainly focuses on the modified carbon materials prepared by the two-step method to improve the methane production performance under ammonia-free or low ammonia inhibition conditions. These modified carbon materials cannot effectively improve the methane production performance of anaerobic digestion substrates that are greatly affected by ammonia inhibition (such as chicken manure), and provide a method for preparing a modified carbon material.
[0009] Another object of the present invention is to provide a modified carbon material prepared by the preparation method.
[0010] Another object of the present invention is to provide application of the modified carbon material in anaerobic digestion.
[0011] Another object of the present invention is to provide a method for producing methane by utilizing organic waste.
[0012] The above-mentioned purpose of the present invention is achieved through the following technical solutions:
[0013] The present invention relates to a method for preparing a modified carbon material, comprising the following steps: mixing biomass waste, a solvent and Fe 6+ The sources are uniformly mixed, and a hydrothermal carbonization reaction is carried out at 150-280° C. The reaction is complete, and then post-processed to obtain a modified carbon material.
[0014] The present invention combines biomass waste, Fe 6+The modified carbon material was prepared by one-pot hydrothermal carbonization of the source and water. The obtained modified carbon material significantly increased the specific surface area compared with the unmodified carbon material, and had a richer porous structure, providing adsorption sites for relieving ammonia inhibition and providing attachment sites for the growth, metabolism and reproduction of functional microorganisms. In addition, on the one hand, iron is an important nutrient element in the metabolic process of anaerobic microorganisms. On the other hand, the chemical bonds between iron atoms and carbon skeletons can act as electron shuttles to promote direct interspecies electron transfer, thereby accelerating the generation of methane and increasing methane production. Adding the above-mentioned modified carbon material to the substrate in situ alleviates the ammonia inhibition of the anaerobic digestion process, accelerates the conversion of volatile fatty acids under ammonia stress, promotes the increase in the generation rate of methane, and is beneficial to improving the efficiency of anaerobic digestion, thereby shortening the anaerobic digestion cycle. In addition, the above-mentioned iron-modified carbon material is magnetic, easy to separate and recycle after anaerobic digestion, and has the advantages of low cost and high efficiency.
[0015] Furthermore, the Fe 6+ Sources include potassium ferrate, ferric acid, sodium ferrate, or ferric periodate.
[0016] Preferably, the biomass waste and Fe 6+ The mass ratio of the sources is (5-20):1, and more preferably (10-20):1.
[0017] Preferably, the solvent is water, biogas slurry or other nitrogen-containing wastewater. Previous studies have explored the use of biogas slurry or other nitrogen-containing wastewater as an alternative solvent for hydrothermal carbonization to successfully prepare carbon materials.
[0018] Furthermore, the biogas slurry is a bright brown liquid formed after the organic matter is fermented, and contains a variety of beneficial substances, such as amino acids, cellulose, protein, etc.
[0019] Furthermore, the other nitrogen-containing wastewaters include papermaking wastewater, leather wastewater, food industry wastewater, and textile wastewater. These wastewaters usually contain high concentrations of nitrogen-containing organic matter, such as protein, carbohydrates, oils, etc., which come from the papermaking, leather, food, textile and other industries respectively.
[0020] Preferably, the solid-liquid ratio of the biomass waste to the solvent is 1:(1-25) g / mL, more preferably 1:(5-10).
[0021] Furthermore, the biomass waste includes one or more of livestock and poultry manure, agricultural waste, and forestry waste.
[0022] Preferably, the biomass waste is agricultural waste and / or forestry waste.
[0023] Furthermore, the agricultural waste is crop straw or crop residues.
[0024] Furthermore, the crop straw includes corn straw, wheat straw, rice straw, soybean straw or tobacco straw.
[0025] Furthermore, the crop residues include bagasse, rice husks, peanut shells, corn cobs, tea straws, oil tea shells, fruit peels or nut shells.
[0026] Furthermore, the forestry waste includes wood chips, and the wood chips include bamboo chips or pine chips.
[0027] Furthermore, the livestock and poultry manure includes one or more of chicken manure, duck manure, and pig manure.
[0028] Preferably, the temperature of the hydrothermal carbonization reaction is 200-240°C.
[0029] Preferably, the heating rate of the hydrothermal carbonization reaction is 3 to 30° C. / min, more preferably 3 to 10° C. / min.
[0030] Preferably, the hydrothermal carbonization reaction time is 1 to 24 hours, more preferably 1 to 3 hours.
[0031] Further, as an optional implementation manner, the uniform mixing method is stirring, and the stirring speed is 100 to 1000 rpm.
[0032] Furthermore, the post-treatment includes cooling, solid-liquid separation, washing and drying.
[0033] Furthermore, the cooling is cooling to room temperature.
[0034] Furthermore, the solid-liquid separation is performed using a vacuum filtration device and a 0.22-0.45 μm filter membrane.
[0035] Furthermore, the washing is performed using water and ethanol.
[0036] Furthermore, the drying is oven drying.
[0037] Furthermore, the drying temperature is 80-105° C., and the drying time is 1-3 hours.
[0038] The present invention protects the modified carbon material prepared by the preparation method.
[0039] The present invention also protects the use of the modified carbon material in anaerobic digestion.
[0040] The present invention protects a method for producing methane by utilizing organic waste, comprising the following steps: fully mixing an anaerobic digestion substrate with an inoculum, adding the modified carbon material therein, and performing anaerobic digestion to produce methane.
[0041] Furthermore, the TS (total solid content) of the anaerobic digestion substrate is greater than 10%.
[0042] Furthermore, the anaerobic digestion substrate includes one or more of livestock and poultry manure, crop waste, and municipal organic waste.
[0043] Furthermore, the livestock and poultry manure includes one or more of chicken manure, duck manure, and pig manure, preferably chicken manure.
[0044] Furthermore, the crop waste is crop straw or crop residue.
[0045] Furthermore, the crop straw includes one or more of rice straw, corn straw, and wheat straw.
[0046] Furthermore, the crop residues include sugarcane leaves and / or rice straw.
[0047] Furthermore, the municipal organic waste includes one or more of sewage, sludge, restaurant waste, and garden waste.
[0048] Further, as a common embodiment, the inoculum comprises hydrolytic acidogenic bacteria and methanogenic archaea.
[0049] Furthermore, the main feature of the hydrolytic acid-producing bacteria is that they hydrolyze insoluble macromolecular organic matter (such as starch, protein, fat, etc.) into soluble small molecule organic matter (such as monosaccharides, amino acids, fatty acids, etc.) by secreting extracellular enzymes, and further convert these soluble organic matter into organic acids (such as acetic acid, propionic acid, butyric acid, etc.) and other metabolites. Furthermore, the dominant bacterial flora of the hydrolytic acid-producing bacteria includes one or more of Firmicutes, Bacteroidota, Spirochaetota, Proteobacteria, Cloacimonadota, Chloroflexi, and Caldatribacteriota.
[0050] Furthermore, the abundance of the dominant bacterial flora of the hydrolytic acid-producing bacteria is greater than 2%.
[0051] Furthermore, the methanogenic archaea include one or more of Methanosarcina, Methanosaeta, Methanobacterium, Methanothermobacter, and Methanoculleus.
[0052] Furthermore, the abundance of the methanogenic archaea is >2%.
[0053] This application mainly explores the addition of modified carbon materials to the substrate to enhance the methane production capacity of anaerobic digestion. This application does not set any special requirements for the use of inoculants, and the use of conventional anaerobic digestion methane production inoculants can meet the experimental requirements.
[0054] Furthermore, the VS (volatile solid content) content in the inoculum is 3 to 10 wt %, preferably 4 to 8 wt %.
[0055] Furthermore, the TS content in the inoculum is 6-15%, preferably 8-12wt%.
[0056] Furthermore, the mixing ratio of the anaerobic digestion substrate to the inoculum is 1:(0.25-4) (based on VS), that is, the above mixing ratio means that the mass ratio of the VS content in the anaerobic digestion substrate to the VS content in the inoculum is 1:(0.25-4).
[0057] Preferably, the mixing ratio of the anaerobic digestion substrate to the inoculum is 1:(0.8-1.5) (based on VS).
[0058] As a more preferred embodiment, the mixing ratio of the anaerobic digestion substrate to the inoculum is 1:1 (based on VS).
[0059] Preferably, the temperature of anaerobic digestion to produce methane is 25-40°C.
[0060] More preferably, the temperature of anaerobic digestion to produce methane is 32-38°C.
[0061] As a most preferred embodiment, the temperature of anaerobic digestion to produce methane is 35-37°C.
[0062] Preferably, the stirring shaft speed of the anaerobic digestion and methane production reactor is 60-120 rpm.
[0063] Compared with the prior art, the present invention has the following beneficial effects:
[0064] The present invention combines biomass waste, Fe 6+The modified carbon material was prepared by one-pot hydrothermal carbonization of the source and water. The obtained modified carbon material significantly increased the specific surface area compared with the unmodified carbon material, and had a richer porous structure, providing adsorption sites for relieving ammonia inhibition and providing attachment sites for the growth, metabolism and reproduction of functional microorganisms. In addition, on the one hand, iron is an important nutrient element in the metabolic process of anaerobic microorganisms. On the other hand, the chemical bonds between iron atoms and carbon skeletons can act as electron shuttles to promote direct interspecies electron transfer, thereby accelerating the generation of methane and increasing methane production. Adding the above-mentioned modified carbon material to the substrate in situ alleviates the ammonia inhibition of the anaerobic digestion process, accelerates the conversion of volatile fatty acids under ammonia stress, promotes the increase in the generation rate of methane, and is beneficial to improving the efficiency of anaerobic digestion, thereby shortening the anaerobic digestion cycle. In addition, the above-mentioned iron-modified carbon material is magnetic, easy to separate and recycle after anaerobic digestion, and has the advantages of low cost and high efficiency. BRIEF DESCRIPTION OF THE DRAWINGS
[0065] Figure 1 This is a statistical chart showing the effect of ammonia inhibition on anaerobic digestion of different livestock and poultry manures.
[0066] Figure 2 SEM images of carbon materials prepared with different potassium ferrate doping amounts.
[0067] Figure 3 This is a statistical chart of the data for enhancing anaerobic digestion of chicken manure with different iron content and different addition amounts of K2FeO4-HC. DETAILED DESCRIPTION
[0068] The present invention is further described below in conjunction with the accompanying drawings and specific examples, but the examples do not limit the present invention in any form. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the art.
[0069] Unless otherwise specified, the reagents and materials used in the following examples are commercially available.
[0070] Inoculum: The initial inoculum was provided by Hanlan Green Power Solid Waste Treatment (Foshan) Co., Ltd. and was continuously cultured in a pilot plant in the laboratory of the Institute of Biomass Engineering of South China Agricultural University. Its substrates were crop straw, livestock and poultry manure, and food waste. The inoculum contained abundant hydrolytic acid-producing bacteria, and its dominant bacterial flora mainly included (abundance>2%) Firmicutes, Bacteroidota, Spirochaetota, Proteobacteria, Cloacimonadota, Chloroflexi, and Caldatribacteriota. In addition, it also contained abundant methanogenic archaea, and its dominant flora mainly included (abundance>2%) Methanosarcina, Methanosaeta, Methanobacterium, Methanothermobacter, and Methanoculleus.
[0071] Example 1 Preparation of carbon materials from different agricultural and forestry wastes
[0072] 1. Preparation of carbon materials from biomass waste
[0073] Sugarcane bagasse, tea branches, bamboo chips and pine sawdust were mixed with deionized water at a ratio of 1:5 (g / mL) and stirred evenly. The mixture was transferred to a reactor and hydrothermally carbonized at 220°C for 1h, with a heating rate of 5°C / min and a stirring speed of 300rpm. After the hydrothermal carbonization, it was cooled to room temperature. A vacuum filtration device and a 0.45μm filter membrane were used for solid-liquid separation, and the solids were washed with deionized water and ethanol and then dried (105°C, 1h). The dried solids were different types of agricultural and forestry waste hot charcoal (HC).
[0074] 2. Regulating high-concentration anaerobic digestion of chicken manure to produce hydrogen raw gas using different agricultural and forestry waste carbon materials
[0075] The substrate used for anaerobic digestion to produce hydrogen raw gas is chicken manure, which was collected from the large-scale breeding farm of Wen's Group. The total solids (TS) and volatile solids (VS) of the raw materials were 17.86% and 15.47%, respectively. The inoculum was taken from the laboratory of the Institute of Biomass Engineering of South China Agricultural University, and its TS and VS were 8.12% and 4.85%, respectively. Chicken manure and inoculum were diluted to 12% by a certain amount of deionized water at a ratio of 7:3 (based on VS), and different agricultural and forestry waste carbon materials were added, and the addition amount of carbon materials was 0.5g / g VS chicken manure. No carbon material was added, and other conditions were the same as the control group.
[0076] The BIPGAS Endeavour instrument was used to monitor the methane production process of high-concentration anaerobic digestion of chicken manure in real time and to standardize the methane production.
[0077] 3. Experimental results
[0078] In the field of anaerobic digestion methanogenesis, the technical digestion time (T80) of 80% of the maximum cumulative methane production is often used to describe the anaerobic digestion methanogenesis performance and efficiency. The present invention uses T80 to characterize the anaerobic digestion methanogenesis performance and efficiency of different agricultural and forestry waste carbon materials. From the measurement results, it can be seen that the T80 of the control group is 23-24 days, the T80 of sugarcane bagasse carbon material is 17-18 days, the T80 of bamboo chips carbon material is 18-19 days, the T80 of pine sawdust carbon material is 18-19 days, and the T80 of tea branch carbon material is 17-18 days. Among them, the T80 of the added carbon material is shortened by up to 7 days compared with the control group, indicating that the addition of carbon material can effectively shorten the methane production cycle.
[0079] Example 2: Application of agricultural and forestry waste carbon materials in anaerobic digestion of different substrates
[0080] 1. Preparation of carbon materials from agricultural and forestry wastes
[0081] The tea branch carbon material was prepared according to the method of Example 1.
[0082] 2. Anaerobic digestion of different substrates to produce hydrogen feed gas
[0083] The substrates used for anaerobic digestion to produce hydrogen raw gas methane are chicken manure, duck manure, pig manure, sugarcane leaves, rice straw and sludge. Chicken manure, duck manure and pig manure were taken from the large-scale breeding farm of Wen's Group. Sugarcane leaves and rice were taken from the South China Agricultural Experimental Base. Sludge was taken from Hanlan Green Power Solid Waste Treatment (Foshan) Co., Ltd. The total solids (TS) and volatile solids (VS) of the raw materials are shown in Table 1. The inoculum was taken from the laboratory of the Biomass Engineering Research Institute of South China Agricultural University, and its TS and VS were 12.5% and 7.39%, respectively. Chicken manure and inoculum were diluted to 12% by a certain amount of deionized water according to a ratio of 7:3 (based on VS), and tea branch carbon material was added. The amount of carbon material added was 0.25g / g VS raw material. No carbon material was added, and other conditions were the same as the control group. In the anaerobic digestion reactor system, the digestion time was a total of 30 days.
[0084] The BIPGAS Endeavour instrument was used to monitor the methane production process of high-concentration anaerobic digestion of organic waste in real time and to standardize the methane production.
[0085] 3. Effect of ammonia inhibition on anaerobic digestion of different substrates
[0086] Ammonia nitrogen concentration was tested using Hach standard reagent. First, the sample to be tested was centrifuged at 8000rpm / min for 10 minutes, filtered through a 0.45μm filter membrane, and then 100μL of the sample to be tested was diluted several times. 100μL of the diluted sample to be tested was added to the reagent tube, and then salicylic acid reagent and cyanuric acid reagent were added first, the lid was closed, and the sample to be tested and the reagent powder were evenly mixed. After 20 minutes, the reading was taken using a DR 3900 (Hach, USA) spectrophotometer.
[0087] 4. Experimental Results
[0088] (1) Results of anaerobic digestion of different substrates to produce hydrogen feed gas
[0089] Table 1 Physical and chemical properties of different raw materials
[0090]
[0091] Note: Ash means ash content.
[0092] Table 2 Effect of carbon materials on improving methane yield in anaerobic digestion of different substrates
[0093]
[0094] The results are shown in Table 2. The methane yield of chicken manure is 193.12 mL / gVS, and the methane yield of chicken manure after adding carbon material is 254.30 mL / gVS, which is 31.68% higher than that without adding carbon material. From the table, the methane yield of duck manure is 221.93 mL / gVS, and the methane yield of duck manure after adding carbon material is 250.34 mL / gVS, which is 12.80% higher than that without adding carbon material. From the table, the methane yield of pig manure is 207.99 mL / gVS, and the methane yield of pig manure after adding carbon material is 235.58 mL / gVS, which is 13.27% higher than that without adding carbon material. From the table, the methane yield of sugarcane leaves is 165.74 mL / gVS, and the methane yield of sugarcane leaves after adding carbon material is 190.34 mL / gVS, which is 14.84% higher than that without adding carbon material. From the table, we know that the methane yield of rice straw is 164.81mL / gVS, and the methane yield of chicken manure after adding carbon material is 182.61mL / gVS, which is 10.80% higher than that without adding carbon material. From the figure, we know that the methane yield of sludge is 142.74mL / gVS, and the methane yield of sludge after adding carbon material is 155.85mL / gVS, which is 9.19% higher than that without adding carbon material.
[0095] It can be seen that the addition of carbon materials alleviated the ammonia inhibition in the anaerobic digestion process of livestock and poultry manure to varying degrees. Among them, the carbon material had the best ammonia inhibition effect on the anaerobic digestion process of chicken manure, and its methane yield was the highest.
[0096] (2) Results of anaerobic digestion of different livestock and poultry manures under the influence of ammonia inhibition
[0097] Depend on Figure 1 It is known that during the anaerobic digestion of three types of livestock and poultry manure, the ammonia nitrogen concentration of the reactor with added carbon materials was lower than that of the experimental group without added carbon materials, indicating that the addition of carbon materials in this application can reduce the ammonia nitrogen concentration, alleviate the ammonia inhibition phenomenon during anaerobic digestion, and effectively increase the methane yield. Among them, compared with pig manure and duck manure, chicken manure is most seriously affected by ammonia inhibition during high-concentration anaerobic digestion, and the addition of carbon materials has the best effect on increasing the methane yield of chicken manure.
[0098] Example 3 Preparation of Iron-modified Carbon Materials with Different Valence States
[0099] 1. Preparation of Iron-modified Carbon Materials with Different Valence States
[0100] Tea branch powder was mixed with deionized water at a ratio of 1:5 (g / mL), and tea branch powder was mixed with five iron sources at a mass ratio of 10:1 to prepare five different types of iron-modified carbon materials. The five iron sources were zero-valent iron (Fe), ferric oxide (Fe2O3), γ-ferric oxide (γFe2O3), ferric oxide (Fe3O4) and potassium ferrate (K2FeO4). After stirring evenly, the mixture was transferred to a reactor and hydrothermally carbonized at 220°C for 1h, with a heating rate of 5°C / min and a stirring speed of 300rpm. After the hydrothermal carbonization was completed, it was cooled to room temperature. A vacuum filtration device and a 0.45μm filter membrane were used for solid-liquid separation, and the solid was washed with deionized water and ethanol and then dried (105°C, 1h). The dried solid was different iron-modified carbon materials. The five carbon materials are: nano zero-valent iron modified carbon material (Fe-HC), nano iron oxide modified carbon material (Fe2O3-HC), nano γ-iron oxide modified carbon material (γFe2O3-HC), nano ferrosoferric oxide modified carbon material (Fe3O4-HC) and potassium ferrate modified carbon material (K2FeO4-HC). The carbon material prepared without adding iron source is non-modified carbon material.
[0101] 2. Carbon materials modified with different valence iron to regulate high-concentration anaerobic digestion of chicken manure to produce hydrogen raw gas
[0102] The substrate used for anaerobic digestion to produce hydrogen raw gas is chicken manure, which was collected from the large-scale breeding farm of Wen's Group. The total solids (TS) and volatile solids (VS) of the raw materials were 18.49% and 16.06%, respectively. The inoculum was taken from the laboratory of the Institute of Biomass Engineering of South China Agricultural University, and its TS and VS were 8.70% and 5.04%, respectively. Chicken manure and inoculum were diluted to 12% by a certain amount of deionized water according to the ratio of 7:3 (based on VS), and iron-modified carbon material was added at a dosage of 0.5g / g VS chicken manure. The control group was used without adding carbon material and other conditions were the same.
[0103] The BIPGAS Endeavour instrument was used to monitor the methane production process of high-concentration anaerobic digestion of chicken manure in real time and to standardize the methane production.
[0104] 3. Effects of different iron-modified carbon materials on high-concentration anaerobic fermentation of chicken manure
[0105] The T80 of the control group was 21-22 days, the T80 of the unmodified carbon material (HC) was 19-20 days, the T80 of Fe-HC was 15-16 days, the T80 of Fe2O3-HC was 18-19 days, the T80 of γ-Fe2O3-HC was 15-16 days, the T80 of Fe3O4-HC was 18-19 days, and the T80 of K2FeO4-HC was 11-12 days. The T80 of the unmodified carbon material was only 3 days shorter than the control at most. The T80 of the carbon material modified with potassium ferrate was up to 11 days shorter than the control group, 9 days shorter than the HC group, and 5 days shorter than other iron-modified carbon materials. This shows that Fe 6+ The source-modified carbon material has a better effect of shortening the fermentation cycle.
[0106] Example 4 Preparation of carbon materials with different iron doping amounts
[0107] 1. Preparation of carbon materials with different iron doping amounts
[0108] Tea branch powder was mixed with deionized water at a ratio of 1:5 (g / mL), and tea branch powder was mixed with potassium ferrate at a mass ratio of 5:1, 10:1, and 20:1, respectively, to prepare three iron-modified carbon materials with different iron-doped amounts. After stirring evenly, the mixture was transferred to a reactor and hydrothermally carbonized at 220°C for 1h, with a heating rate of 5°C / min and a stirring speed of 300rpm. After the hydrothermal carbonization was completed, it was cooled to room temperature. A vacuum filtration device and a 0.45μm filter membrane were used for solid-liquid separation, and the solid was washed with deionized water and ethanol. The dried solid was the carbon material with different iron-doped amounts (according to the mass ratio of tea branch powder to potassium ferrate, the obtained hydrothermal carbons were named K2FeO4-HC-5:1, K2FeO4-HC-10:1, and K2FeO4-HC-20:1, respectively)
[0109] 2. Elements and specific surface area determination
[0110] (1) Determination of elements and specific surface area
[0111] The mass contents of C, H, N and S in the raw materials and carbon materials were determined using an elemental analyzer (Vario EL cube, Hanau, Germany); the specific surface area (BET) of the carbon materials was determined using a Micromeritics ASAP 2460 (fully automatic specific surface and porosity analyzer). Before the measurement, the samples were pretreated at 120 °C under vacuum for 2 hours using the standard degassing station of the MIC instrument. The samples were subjected to nitrogen adsorption and desorption tests under 77K liquid nitrogen conditions. After instrumental analysis, isothermal adsorption and desorption curves were obtained, and the total specific surface area of the material was obtained by the BET method.
[0112] (2) Morphology measurement
[0113] The surface morphology of carbon materials with different iron doping amounts was observed using a Czech TESCAN MIRALMS (scanning electron microscope). Before testing, the samples were ultrasonically dispersed in ethanol and then dropped on the conductive glue. After the ethanol evaporated, the samples were sputtered with gold ions for 45 seconds at a current of 10 mA. Finally, the samples were observed at an acceleration voltage of 15 kV and a magnification of 2000-50000x.
[0114] 3. Carbon materials with different iron content regulate high-concentration anaerobic digestion of chicken manure to produce hydrogen raw gas
[0115] The substrate used for anaerobic digestion to produce hydrogen raw gas is chicken manure, which was collected from the large-scale breeding farm of Wen's Group. The total solids (TS) and volatile solids (VS) of the raw materials were 18.43% and 15.99%, respectively. The inoculum was taken from a continuous stirred anaerobic digestion reactor that was operating normally under medium temperature conditions (36±1℃) with chicken manure in the laboratory, and its TS% and VS% were 8.35% and 4.90%, respectively. Chicken manure and inoculum were mixed at a ratio of 7:3 (based on VS), and a certain amount of deionized water was added to dilute the TS content to 12%, and iron-modified carbon materials (K2FeO4-HC) with different iron doping amounts were added. The addition amount of carbon material was 0.25g / g VS chicken manure~0.5g / g VS chicken manure.
[0116] The BIPGAS Endeavour instrument was used to monitor the methane production process of high-concentration anaerobic digestion of chicken manure in real time and to standardize the methane production.
[0117] 4. Experimental Results
[0118] (1) Physical and chemical analysis results of modified carbon materials
[0119] Table 3 Measurement results of elements and specific surface area
[0120]
[0121] The results of elements and specific surface area are shown in Table 3. Compared with the unmodified carbon materials, the carbon and nitrogen elements of all modified carbon materials decreased significantly. Compared with the unmodified carbon materials, the specific surface area of K2FeO4-HC with different iron doping amounts was significantly improved, providing more adsorption sites for relieving ammonia inhibition and providing attachment sites for the growth, metabolism and reproduction of microorganisms. Among them, the specific surface area of the lower iron doping amount (20:1) was the highest, reaching 38.74m 2 / g, which is 2.07 times that of the unmodified carbon material.
[0122] (2) Morphology analysis
[0123] The results are as follows Figure 2 As shown, the iron element in the K2FeO4-HC carbon materials with different doping ratios is evenly distributed, so it has a larger specific surface area. In addition, the pore structure can be seen on the surface of the modified carbon material, which is an ideal place for the attachment of microorganisms.
[0124] (3) Effects of modified carbon materials with different iron doping amounts on anaerobic fermentation of high-concentration chicken manure
[0125] The results are as follows Figure 3 As shown, the daily methane yield peak time of the modified carbon materials with different iron doping amounts (K2FeO4-HC-5:1, K2FeO4-HC-10:1, K2FeO4-HC-20:1) and different added amounts of K2FeO4-HC-20:1 in this embodiment is shortened by 8 to 12 days compared with the control group, and the peak yield is increased by 6.39 to 21.16%, which indicates that the above-mentioned different iron doping amounts and different added amounts of K2FeO4-HC can increase the methane production rate and have a good effect of shortening the fermentation cycle.
[0126] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.
Claims
1. A method for preparing a modified carbon material, characterized in that: The steps include: mixing biomass waste, solvent and Fe 6+ The sources are uniformly mixed, and a hydrothermal carbonization reaction is carried out at 150-280° C. The reaction is complete, and then post-processed to obtain a modified carbon material.
2. The preparation method according to claim 1, characterized in that: The Fe 6+ Sources include potassium ferrate, ferric acid, sodium ferrate, or ferric periodate.
3. The preparation method according to claim 1, characterized in that: The biomass waste and Fe 6+ The mass ratio of the source is (5~20):
1.
4. The preparation method according to claim 1, characterized in that: The solvent includes water, biogas slurry or other nitrogen-containing wastewater.
5. The preparation method according to claim 1, characterized in that: The biomass waste includes one or more of livestock and poultry manure, agricultural waste, and forestry waste.
6. The modified carbon material prepared by the preparation method according to any one of claims 1 to 5.
7. Use of the modified carbon material according to claim 6 in anaerobic digestion.
8. A method for producing methane using organic waste, characterized in that: The method comprises the following steps: fully mixing the anaerobic digestion substrate and the inoculum, adding the modified carbon material according to claim 6 thereto, and performing anaerobic digestion to produce methane.
9. The method according to claim 8, characterized in that: The anaerobic digestion substrate includes one or more of livestock and poultry manure, crop residues, and municipal organic waste.
10. The method according to claim 9, characterized in that: The livestock and poultry manure includes one or more of chicken manure, duck manure and pig manure.