CN118389183A - Natural gas extraction method based on kitchen waste - Google Patents
Natural gas extraction method based on kitchen waste Download PDFInfo
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- CN118389183A CN118389183A CN202410855240.3A CN202410855240A CN118389183A CN 118389183 A CN118389183 A CN 118389183A CN 202410855240 A CN202410855240 A CN 202410855240A CN 118389183 A CN118389183 A CN 118389183A
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- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 title claims abstract description 180
- 239000003345 natural gas Substances 0.000 title claims abstract description 89
- 239000010806 kitchen waste Substances 0.000 title claims abstract description 87
- 238000000605 extraction Methods 0.000 title claims abstract description 26
- 238000000855 fermentation Methods 0.000 claims abstract description 158
- 239000007789 gas Substances 0.000 claims abstract description 123
- 238000002485 combustion reaction Methods 0.000 claims abstract description 94
- 239000002002 slurry Substances 0.000 claims abstract description 59
- 238000001035 drying Methods 0.000 claims abstract description 44
- 239000004519 grease Substances 0.000 claims abstract description 41
- 238000000746 purification Methods 0.000 claims abstract description 17
- 239000012535 impurity Substances 0.000 claims abstract description 6
- 239000010802 sludge Substances 0.000 claims abstract description 6
- 230000004151 fermentation Effects 0.000 claims description 118
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 60
- 238000000926 separation method Methods 0.000 claims description 54
- 238000006477 desulfuration reaction Methods 0.000 claims description 37
- 230000023556 desulfurization Effects 0.000 claims description 37
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 claims description 26
- 239000012528 membrane Substances 0.000 claims description 25
- 238000000034 method Methods 0.000 claims description 24
- 230000018044 dehydration Effects 0.000 claims description 15
- 238000006297 dehydration reaction Methods 0.000 claims description 15
- 229910002092 carbon dioxide Inorganic materials 0.000 claims description 13
- 239000001569 carbon dioxide Substances 0.000 claims description 13
- 238000005261 decarburization Methods 0.000 claims description 9
- 238000012544 monitoring process Methods 0.000 claims description 8
- 238000005262 decarbonization Methods 0.000 claims description 7
- 238000002156 mixing Methods 0.000 claims description 5
- 239000000203 mixture Substances 0.000 claims description 4
- 238000001704 evaporation Methods 0.000 claims description 3
- 238000010438 heat treatment Methods 0.000 claims description 3
- 125000004122 cyclic group Chemical group 0.000 description 16
- 244000005700 microbiome Species 0.000 description 13
- 239000000126 substance Substances 0.000 description 8
- 230000000694 effects Effects 0.000 description 7
- 230000007423 decrease Effects 0.000 description 5
- 238000004064 recycling Methods 0.000 description 5
- 150000003568 thioethers Chemical class 0.000 description 5
- 230000008859 change Effects 0.000 description 4
- 210000003608 fece Anatomy 0.000 description 4
- 244000144972 livestock Species 0.000 description 4
- 239000010871 livestock manure Substances 0.000 description 4
- 244000144977 poultry Species 0.000 description 4
- 238000012360 testing method Methods 0.000 description 4
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 description 3
- 229910002091 carbon monoxide Inorganic materials 0.000 description 3
- 238000006243 chemical reaction Methods 0.000 description 3
- 239000003344 environmental pollutant Substances 0.000 description 3
- MWUXSHHQAYIFBG-UHFFFAOYSA-N nitrogen oxide Inorganic materials O=[N] MWUXSHHQAYIFBG-UHFFFAOYSA-N 0.000 description 3
- 239000003895 organic fertilizer Substances 0.000 description 3
- 239000012466 permeate Substances 0.000 description 3
- 231100000719 pollutant Toxicity 0.000 description 3
- 239000000047 product Substances 0.000 description 3
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 2
- RWSOTUBLDIXVET-UHFFFAOYSA-N Dihydrogen sulfide Chemical compound S RWSOTUBLDIXVET-UHFFFAOYSA-N 0.000 description 2
- 239000004695 Polyether sulfone Substances 0.000 description 2
- 239000003463 adsorbent Substances 0.000 description 2
- 229920002301 cellulose acetate Polymers 0.000 description 2
- 238000000354 decomposition reaction Methods 0.000 description 2
- 230000003247 decreasing effect Effects 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
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- 229910000037 hydrogen sulfide Inorganic materials 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 239000002207 metabolite Substances 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 239000001301 oxygen Substances 0.000 description 2
- 229910052760 oxygen Inorganic materials 0.000 description 2
- 229920002492 poly(sulfone) Polymers 0.000 description 2
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- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- OTMSDBZUPAUEDD-UHFFFAOYSA-N Ethane Chemical compound CC OTMSDBZUPAUEDD-UHFFFAOYSA-N 0.000 description 1
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 1
- 229930182558 Sterol Natural products 0.000 description 1
- 230000002053 acidogenic effect Effects 0.000 description 1
- 239000012670 alkaline solution Substances 0.000 description 1
- 229910021529 ammonia Inorganic materials 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 238000004364 calculation method Methods 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 238000004891 communication Methods 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 235000014113 dietary fatty acids Nutrition 0.000 description 1
- 230000029087 digestion Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000003912 environmental pollution Methods 0.000 description 1
- 239000000194 fatty acid Substances 0.000 description 1
- 229930195729 fatty acid Natural products 0.000 description 1
- 150000004665 fatty acids Chemical class 0.000 description 1
- 239000010794 food waste Substances 0.000 description 1
- 239000012634 fragment Substances 0.000 description 1
- 229930195733 hydrocarbon Natural products 0.000 description 1
- 150000002430 hydrocarbons Chemical class 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 125000004435 hydrogen atom Chemical class [H]* 0.000 description 1
- 230000003301 hydrolyzing effect Effects 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 230000004060 metabolic process Effects 0.000 description 1
- 230000037323 metabolic rate Effects 0.000 description 1
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- 239000002808 molecular sieve Substances 0.000 description 1
- 150000007524 organic acids Chemical class 0.000 description 1
- 150000002989 phenols Chemical class 0.000 description 1
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- 239000004033 plastic Substances 0.000 description 1
- 229920003023 plastic Polymers 0.000 description 1
- 238000010248 power generation Methods 0.000 description 1
- 238000004537 pulping Methods 0.000 description 1
- 150000003839 salts Chemical class 0.000 description 1
- 239000002893 slag Substances 0.000 description 1
- URGAHOPLAPQHLN-UHFFFAOYSA-N sodium aluminosilicate Chemical compound [Na+].[Al+3].[O-][Si]([O-])=O.[O-][Si]([O-])=O URGAHOPLAPQHLN-UHFFFAOYSA-N 0.000 description 1
- 239000002689 soil Substances 0.000 description 1
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- 235000003702 sterols Nutrition 0.000 description 1
- UFTFJSFQGQCHQW-UHFFFAOYSA-N triformin Chemical compound O=COCC(OC=O)COC=O UFTFJSFQGQCHQW-UHFFFAOYSA-N 0.000 description 1
- 241001148471 unidentified anaerobic bacterium Species 0.000 description 1
Classifications
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E50/00—Technologies for the production of fuel of non-fossil origin
- Y02E50/30—Fuel from waste, e.g. synthetic alcohol or diesel
Landscapes
- Processing Of Solid Wastes (AREA)
Abstract
The invention relates to the technical field of kitchen waste treatment, in particular to a natural gas extraction method based on kitchen waste. Comprising the following steps: sorting kitchen waste to obtain organic matters and inorganic matter impurities; separating the organic matters from the grease to obtain grease and residual organic matters; crushing the residual organic matters to obtain organic slurry; anaerobic fermentation of the organic slurry and anaerobic sludge to obtain primary biogas, biogas slurry and primary biogas residue; the primary biogas residue and/or grease is/are subjected to anoxic combustion to generate CO-containing hot gas, and simultaneously the biogas slurry generated by combustion is dried at high temperature to obtain secondary biogas and secondary biogas residue; and purifying the heat-carrying gas generated by burning the grease and the primary biogas residues with the primary biogas and the secondary biogas to obtain the mixed natural gas. According to the invention, primary biogas residues generated by grease and anaerobic fermentation in kitchen waste are utilized to provide heat for anaerobic fermentation and biogas slurry drying, and meanwhile, hot gas generated by burning the grease and the primary biogas residues is mixed with primary biogas and secondary biogas for purification to obtain mixed natural gas, so that the kitchen waste is recycled to the maximum.
Description
Technical Field
The invention relates to the technical field of kitchen waste treatment, in particular to a natural gas extraction method based on kitchen waste.
Background
Along with the rapid development of social economy and the improvement of the living standard of people, the kitchen waste production is increased day by day, and the kitchen waste has become an important pollution source affecting the living environment. The anaerobic fermentation technology is adopted to treat the kitchen waste to become an optional treatment method, and anaerobic microorganisms (such as anaerobic bacteria) are utilized to decompose organic matters in an anaerobic or low-oxygen environment to generate biogas and other biochemical substances, and the generated biogas can be prepared into biogas, so that the resource utilization of the kitchen waste is realized, the environmental pollution is reduced, and meanwhile, the power generation or the heat supply is realized.
Chinese patent publication No.: CN112191665B discloses a system for preparing biological natural gas by cooperatively treating kitchen waste and livestock and poultry manure and a preparation method thereof, comprising the following steps: the system comprises a kitchen waste pretreatment system, a kitchen waste treatment and livestock and poultry manure mixing system, an anaerobic fermentation system, a biogas purification system and an anaerobic fermentation and digestion liquid preparation organic fertilizer system, wherein the treated kitchen waste and livestock and poultry manure are mixed and subjected to anaerobic fermentation, and biogas is prepared after dehydration, desulfurization and decarbonization through biogas purification and purification.
Therefore, although the technical scheme can prepare the biological natural gas by cooperatively treating kitchen waste and livestock and poultry manure and produce the organic fertilizer by utilizing anaerobic fermentation biogas slurry and biogas residues, the following problems exist: although the biogas residue can be used for preparing organic fertilizer, the fertilizer efficiency of the biogas residue is possibly inferior to that of the traditional fertilizer, and the biogas residue needs additional treatment to meet the market demand, and the biogas residue contains higher organic matters and salts and can pollute the environment and soil if the biogas residue is improperly treated. Therefore, a method for maximizing the utilization of kitchen waste and improving the treatment efficiency and avoiding excessive treatment steps is urgently needed.
Disclosure of Invention
Therefore, the invention provides a natural gas extraction method based on kitchen waste, which is used for solving the problem of low recycling rate of the kitchen waste in the prior art.
In order to achieve the above object, the present invention provides a method for extracting natural gas based on kitchen waste, comprising:
step S1, sorting kitchen waste to obtain organic matters and inorganic matter impurities;
S2, separating grease from the organic matters to obtain grease and residual organic matters;
S3, crushing the residual organic matters to obtain organic slurry;
s4, mixing the organic slurry and anaerobic sludge according to a preset proportion, adding the mixture into an anaerobic reactor, and performing anaerobic fermentation to obtain primary biogas, biogas slurry and primary biogas residues;
s5, throwing the primary biogas residues and/or part of the grease into a combustion bin for anoxic combustion to generate a heat-carrying gas containing CO, and simultaneously, drying the biogas slurry at a high temperature generated by anoxic combustion to separate the biogas slurry into secondary biogas and secondary biogas residues;
The primary biogas residue is dried before being put into a combustion bin and then subjected to anoxic combustion, and the air inlet proportion is determined according to the water content and the biogas residue density of the primary biogas residue after being dried;
Step S6, purifying the heat-carrying gas generated by burning the primary biogas residues and/or the grease and the mixed gas of the secondary biogas extracted based on the biogas slurry and the primary biogas generated by anaerobic fermentation together to obtain mixed natural gas,
And determining a separation ratio of a gas membrane according to the carbon dioxide content in the mixed gas so as to separate the carbon dioxide in the mixed gas and obtain the purified mixed natural gas.
Further, in step S4, during anaerobic fermentation, a plurality of fermentation sections are provided, and fermentation temperatures in the respective fermentation sections are different, including:
In an initial fermentation section, the fermentation temperature is a first fermentation temperature;
in the active fermentation section, the fermentation temperature is a second fermentation temperature;
in the stable fermentation section, the fermentation temperature is a first fermentation temperature;
Wherein the range of the first fermentation temperature is 30-40 ℃, and the range of the second fermentation temperature is 41-55 ℃.
Further, in the step S5, adjusting the fermentation temperature in the anaerobic reactor by using the grease and/or the heat-carrying gas generated by the primary biogas residue combustion during the anaerobic fermentation process, including:
if the fermentation temperature is lower than the preset temperature range, increasing the flow of the heat carrying gas;
And if the fermentation temperature is higher than the preset temperature range, reducing the flow of the heat carrying gas.
Further, in the step S5, determining the air inlet ratio for the first anoxic combustion according to the density and the water content of the biogas residue after the primary biogas residue drying includes:
obtaining the quality, the volume and the water content of the biogas residue after primary drying;
Calculating the biogas residue density of the primary biogas residue based on the biogas residue mass and the biogas residue volume;
And determining the air inlet proportion based on the biogas residue density and the water content.
Further, in the step S5, extracting the heat-carrying gas based on the primary biogas residue includes:
Monitoring the CO content in the heat-carrying gas in the primary biogas residue combustion process, and adjusting the air inlet proportion based on the CO content percentage, wherein,
If the CO content percentage is lower than the preset CO content percentage, reducing the air inlet proportion or adding primary biogas residues into the combustion bin, wherein the water content of the primary biogas residues added into the combustion bin after drying is 15-20%.
Further, in the step S5, according to the difference between the percentage of CO content and the percentage of the preset CO content, the water content of the biogas residues put into the combustion bin is determined.
Further, in the step S5, the treatment of the primary biogas residue includes:
The primary biogas residue is subjected to drying treatment before combustion, so that the water content of the primary biogas residue is within the range of 10% -20%.
Further, in the step S6, a step of separating CO 2 in the mixed gas includes:
Step S61, obtaining the mole fraction of CO 2 in the mixed gas;
Step S62, separating CO 2 in the mixed gas through a gas membrane based on preset pressure and calculating the separation ratio of CO 2 in the mixed gas;
Step S63, adjusting the preset pressure based on the separation ratio, including:
And if the separation ratio is lower than the preset separation ratio, increasing the separation pressure.
Further, in step S5, the step of drying the biogas slurry at a high temperature to separate the secondary biogas includes:
heating the biogas slurry to a first temperature value, and then starting secondary biogas collection;
When the increment value of the secondary biogas yield in the preset time range is lower than a preset threshold value, judging that the secondary biogas collection is finished;
and increasing the first temperature value to a second temperature value, and evaporating the biogas slurry by water vapor based on the second temperature value to obtain secondary biogas residues.
Further, the purification further comprises dehydration, decarburization and desulfurization;
if the desulfurization is dry desulfurization, the purification sequence is dehydration, desulfurization and decarburization;
If the desulfurization is wet desulfurization or biological desulfurization, the purification sequence is desulfurization, dehydration and decarburization.
Compared with the prior art, the method has the beneficial effects that grease obtained by sorting kitchen waste and primary biogas residues generated by anaerobic fermentation are utilized to provide heat for the anaerobic fermentation process and biogas slurry generated by high-temperature drying anaerobic fermentation, so that the smooth progress of anaerobic fermentation is ensured. Simultaneously, the grease, the heat-carrying gas generated after the primary biogas residue is combusted and the secondary biogas extracted based on the biogas slurry and the primary biogas generated by anaerobic fermentation are purified together to obtain the mixed natural gas, so that the purity of the finally obtained mixed natural gas is ensured, the extraction amount of the natural gas extracted from the kitchen waste is improved, and the maximization of the cyclic utilization of the kitchen waste is realized.
Furthermore, the method sets the initial fermentation section, the active fermentation section and the stable fermentation section based on the change condition of the microbial activity in the anaerobic fermentation process, and sets different fermentation temperatures in different fermentation sections, so that the fermentation process is controlled more effectively, the microbes can obtain the most suitable growth environment in different sections, the fermentation efficiency and the product quality are improved, the extraction amount of natural gas extracted from kitchen waste is further improved, the purity of the finally obtained mixed natural gas is ensured, and the maximization of the recycling of the kitchen waste is realized.
Furthermore, the invention provides heat for the anaerobic fermentation process through burning grease and/or heat-carrying gas generated by primary biogas residues, thereby effectively solving the problem that the fermentation temperature is difficult to control. Meanwhile, the flow of the heat-carrying gas is regulated in real time by monitoring the fermentation temperatures in different sections of the anaerobic reactor, so that the fermentation temperature is ensured to be stabilized in a preset range, and the kitchen waste is ensured to be completely fermented, thereby further improving the extraction amount of the natural gas extracted from the kitchen waste, ensuring the purity of the finally obtained mixed natural gas and realizing the maximization of the cyclic utilization of the kitchen waste.
Further, the invention determines the air inlet proportion by obtaining the quality, the volume and the water content of the biogas residue after primary biogas residue drying, ensures the uniform combustion of primary biogas residue, improves the combustion efficiency, and simultaneously obtains more heat-carrying gas containing CO to the greatest extent, thereby further improving the extraction amount of natural gas extracted from kitchen waste, ensuring the purity of the finally obtained mixed natural gas and realizing the maximization of the recycling of the kitchen waste.
Further, the CO content in the heat-carrying gas generated in the primary biogas residue combustion process is monitored, the air inlet proportion is adjusted in real time, the CO yield of the target gas is improved, the quality of the finally extracted mixed natural gas is improved, the purity of the finally obtained mixed natural gas is further ensured, and the maximization of the cyclic utilization of kitchen wastes is realized.
Further, the water content of the biogas residues put into the combustion bin is determined according to the difference between the CO content percentage and the preset CO content percentage, so that the CO content of the heat-carrying gas generated after primary biogas residue combustion is further improved, the extraction amount of natural gas extracted from kitchen wastes is improved, the purity of the finally obtained mixed natural gas is ensured, and the maximization of the cyclic utilization of the kitchen wastes is realized.
Furthermore, the invention carries out drying treatment before the primary biogas residue is combusted, so that the water content of the primary biogas residue is reduced, thereby improving the combustion efficiency and facilitating the subsequent combustion of the primary biogas residue to provide heat for anaerobic fermentation. Thereby further improving the extraction quantity of the natural gas extracted from the kitchen waste, ensuring the purity of the finally obtained mixed natural gas and realizing the maximization of the cyclic utilization of the kitchen waste.
Furthermore, the preset pressure is adjusted by monitoring the separation ratio of CO 2 in the mixed gas in real time, so that the separation pressure in the gas membrane separation process is always in the optimal state, and the separation efficiency of CO 2 is improved. Thereby further improving the extraction quantity of the natural gas extracted from the kitchen waste, ensuring the purity of the finally obtained mixed natural gas and realizing the maximization of the cyclic utilization of the kitchen waste.
Further, the secondary biogas and the secondary biogas residues can be effectively extracted from the biogas slurry again by drying the biogas slurry at a high temperature, so that the energy utilization rate is greatly improved, the extraction amount of the natural gas extracted from the kitchen waste is further improved, the purity of the finally obtained mixed natural gas is ensured, and the maximization of the cyclic utilization of the kitchen waste is realized.
Furthermore, the mixed gas is subjected to purification treatment such as dehydration, desulfurization, decarbonization and the like, so that the purified natural gas can reach the urban natural gas standard, the combustion value generated after the natural gas is combusted is higher, the pollutant emission during the combustion of the mixed natural gas is further reduced, the utilization value of the mixed natural gas is improved, the purity of the finally obtained mixed natural gas is further ensured, and the maximization of the cyclic utilization of kitchen wastes is realized.
Drawings
FIG. 1 is a flow chart of a method for extracting natural gas based on kitchen waste according to the invention;
FIG. 2 is a schematic diagram of a kitchen waste-based natural gas extraction process of the present invention;
FIG. 3 is a flow chart of the invention for separating CO 2 from a mixed gas;
FIG. 4 is a flow chart of the process for obtaining secondary biogas by drying biogas slurry at high temperature.
Detailed Description
In order that the objects and advantages of the invention will become more apparent, the invention will be further described with reference to the following examples; it should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention.
Preferred embodiments of the present invention are described below with reference to the accompanying drawings. It should be understood by those skilled in the art that these embodiments are merely for explaining the technical principles of the present invention, and are not intended to limit the scope of the present invention.
It should be noted that, in the description of the present invention, terms such as "upper," "lower," "left," "right," "inner," "outer," and the like indicate directions or positional relationships based on the directions or positional relationships shown in the drawings, which are merely for convenience of description, and do not indicate or imply that the apparatus or elements must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as limiting the present invention.
Furthermore, it should be noted that, in the description of the present invention, unless explicitly specified and limited otherwise, the terms "mounted," "connected," and "connected" are to be construed broadly, and may be either fixedly connected, detachably connected, or integrally connected, for example; can be mechanically or electrically connected; can be directly connected or indirectly connected through an intermediate medium, and can be communication between two elements. The specific meaning of the above terms in the present invention can be understood by those skilled in the art according to the specific circumstances.
Referring to fig. 1 and 2, fig. 1 is a flow chart of a method for extracting natural gas based on kitchen waste according to the present invention, and fig. 2 is a schematic diagram of a method for extracting natural gas based on kitchen waste according to the present invention. Specifically, the invention provides a natural gas extraction method based on kitchen waste, which comprises the following steps:
step S1, sorting kitchen waste to obtain organic matters and inorganic matter impurities;
S2, separating grease from the organic matters to obtain grease and residual organic matters;
S3, crushing the residual organic matters to obtain organic slurry;
s4, mixing the organic slurry and anaerobic sludge according to a preset proportion, adding the mixture into an anaerobic reactor, and performing anaerobic fermentation to obtain primary biogas, biogas slurry and primary biogas residues;
s5, throwing the primary biogas residues and/or part of the grease into a combustion bin for anoxic combustion to generate a heat-carrying gas containing CO, and simultaneously, drying the biogas slurry at a high temperature generated by anoxic combustion to separate the biogas slurry into secondary biogas and secondary biogas residues;
The primary biogas residue is dried before being put into a combustion bin and then subjected to anoxic combustion, and the air inlet proportion is determined according to the water content and the biogas residue density of the primary biogas residue after being dried;
Step S6, purifying the heat-carrying gas generated by burning the primary biogas residues and/or the grease and the mixed gas of the secondary biogas extracted based on the biogas slurry and the primary biogas generated by anaerobic fermentation together to obtain mixed natural gas,
And determining a separation ratio of a gas membrane according to the carbon dioxide content in the mixed gas so as to separate the carbon dioxide in the mixed gas and obtain the purified mixed natural gas.
It is understood that the kitchen waste contains not only organic matters (food residues and grease) but also inorganic matters (tableware fragments and plastics), so that the kitchen waste is firstly separated to separate the organic matters from the inorganic matters; grease is separated from the organic matters to obtain grease and residual organic matters, the obtained grease can be used for providing heat for anaerobic fermentation, and the residual organic matters are crushed to obtain organic slurry which is easier to carry out anaerobic fermentation; anaerobic sludge contains a large amount of microorganisms including methanogens and the like, and the microorganisms can accelerate the decomposition and conversion of organic substances in organic slurry. After anaerobic fermentation, primary biogas residues, biogas slurry and primary biogas are generated. As for the specific embodiments of sorting, grease separation and pulping kitchen waste, any of the prior art can be adopted, and details thereof are omitted herein.
It can be understood that the primary biogas residue contains some substances such as unfermented organic slurry, unsorted inorganic impurities and the like, and hot gas is generated in the primary biogas residue combustion process, which comprises the following steps: carbon monoxide, carbon dioxide, water vapor, sulfides, nitrogen oxides, hydrogen, hydrocarbons (e.g., methane, ethane), the amount and composition of these gases being affected by the combustion conditions. Therefore, the air inlet proportion is determined, so that the carbon monoxide yield obtained by primary biogas residue under the incomplete combustion condition is the greatest. The biogas slurry contains some organic matters and inorganic impurities, and the organic matters comprise organic acid, ammonia, alcohol and phenols, so that the primary biogas residue is put into a combustion bin for anoxic combustion to generate heat-carrying gas containing CO. Meanwhile, the biogas slurry is dried by utilizing the high temperature generated by anoxic combustion, so that the biogas slurry is separated into secondary biogas and secondary biogas residues. And purifying the grease, the heat-carrying gas generated after the primary biogas residue is combusted, the secondary biogas extracted based on the biogas slurry and the primary biogas generated by anaerobic fermentation together to obtain the mixed natural gas.
According to the invention, grease obtained by sorting kitchen waste and primary biogas residues generated by anaerobic fermentation are utilized to provide heat for the anaerobic fermentation process and biogas slurry generated by high-temperature drying anaerobic fermentation, so that the smooth progress of anaerobic fermentation is ensured. Simultaneously, the grease, the heat-carrying gas generated after the primary biogas residue is combusted and the secondary biogas extracted based on the biogas slurry and the primary biogas generated by anaerobic fermentation are purified together to obtain the mixed natural gas, so that the purity of the finally obtained mixed natural gas is ensured, the extraction amount of the natural gas extracted from the kitchen waste is improved, and the maximization of the cyclic utilization of the kitchen waste is realized.
Specifically, in step S4, a plurality of fermentation sections are provided during anaerobic fermentation, and fermentation temperatures in the respective fermentation sections are different, including:
In an initial fermentation section, the fermentation temperature is a first fermentation temperature;
in the active fermentation section, the fermentation temperature is a second fermentation temperature;
in the stable fermentation section, the fermentation temperature is a first fermentation temperature;
Wherein the range of the first fermentation temperature is 30-40 ℃, and the range of the second fermentation temperature is 41-55 ℃.
It is understood that anaerobic fermentation involves a variety of microorganisms, including hydrolytic, acidogenic, methanogenic, and the like, among anaerobic sludge. These microorganisms have different optimum growth temperatures. In different fermentation sections, dominant microorganism species may change and activity may also change, so that three fermentation sections are set to correspond to different fermentation temperatures. The initial fermentation section is designed to activate and start the microorganisms during fermentation, so that the fermentation temperature is a first fermentation temperature, in which the microorganisms start to activate, decompose organic substances and produce the desired metabolites. In order to maintain high activity of the microorganism, the active fermentation section promotes rapid decomposition of organic substances and formation of metabolites, so that the fermentation temperature is set to a second fermentation temperature, and the chemical reaction rate is accelerated by a higher fermentation temperature. The fermentation temperature in the stable fermentation stage is the third fermentation temperature, and in this section, the activity of the microorganism starts to decrease, and the decrease of the fermentation temperature can slow down the metabolic rate, and simultaneously ensure the stability and quality of the product.
In practice, the value of the initial fermentation zone ranges from 1 day to 3 days, and the preferred value of the initial fermentation zone is 2 days; the value range of the active fermentation section is 7-10 days, and the optimal value of the active fermentation section is 7 days; the value of the stable fermentation section ranges from 15 days to 30 days, and the preferred value of the stable fermentation section is 20 days. The value range of the first fermentation temperature is 30-40 ℃, and the optimal value of the first fermentation temperature is 35 ℃; the value of the second fermentation temperature is 41-55 ℃, and the preferred value of the second fermentation temperature is 42 ℃. The initial fermentation section, the active fermentation section, the stable fermentation section, the first fermentation temperature, the second fermentation temperature, the value range and the preferred value are determined according to actual conditions, and are not described herein.
According to the invention, the initial fermentation section, the active fermentation section and the stable fermentation section are set based on the change condition of the activity of microorganisms in the anaerobic fermentation process, and different fermentation temperatures are set in different fermentation sections, so that the fermentation process is controlled more effectively, the microorganisms can obtain the most suitable growth environment in different sections, the fermentation efficiency and the product quality are improved, the extraction amount of natural gas extracted from kitchen wastes is further improved, the purity of the finally obtained mixed natural gas is ensured, and the maximization of the cyclic utilization of the kitchen wastes is realized.
Specifically, in the step S5, the adjustment of the fermentation temperature in the anaerobic reactor during the anaerobic fermentation process by using the heat-carrying gas generated by the combustion of the grease and/or the primary biogas residue includes:
if the fermentation temperature is lower than the preset temperature range, increasing the flow of the heat carrying gas;
And if the fermentation temperature is higher than the preset temperature range, reducing the flow of the heat carrying gas.
It can be understood that the grease and the primary biogas residue can be reused, and the heat-carrying gas generated by the combustion of the grease and/or the primary biogas residue can provide heat for anaerobic fermentation so as to maintain a certain fermentation temperature, thereby ensuring that the fermentation process can be carried out within a preset temperature range. The fermentation temperature in the anaerobic reactor is monitored in different fermentation sections, the preset temperature range corresponding to the different fermentation temperatures of the different sections. When the fermentation temperature is monitored to be lower than the preset temperature range, the flow rate of the heat carrying gas needs to be increased, so that the fermentation temperature is increased. When the fermentation temperature is higher than the preset temperature range, the flow rate of the heat carrying gas needs to be reduced, so that the fermentation temperature is reduced.
It will be appreciated that the production and flow of the heat carrying gas may be increased or decreased by increasing or decreasing the amount of fat and/or slag burned. Heat is transferred to the organic slurry by heat exchange between the heat carrying gas and the anaerobic reactor to maintain the optimal temperature for anaerobic fermentation.
According to the invention, heat is provided for the anaerobic fermentation process by burning grease and/or heat-carrying gas generated by primary biogas residues, so that the problem that the fermentation temperature is difficult to control is effectively solved. Meanwhile, the flow of the heat-carrying gas is regulated in real time by monitoring the fermentation temperatures in different sections of the anaerobic reactor, so that the fermentation temperature is ensured to be stabilized in a preset range, and the kitchen waste is ensured to be completely fermented, thereby further improving the extraction amount of the natural gas extracted from the kitchen waste, ensuring the purity of the finally obtained mixed natural gas and realizing the maximization of the cyclic utilization of the kitchen waste.
Specifically, in the step S5, determining the air inlet ratio according to the density and the water content of the biogas residue after primary biogas residue drying includes:
obtaining the quality, the volume and the water content of the biogas residue after primary drying;
Calculating the biogas residue density of the primary biogas residue based on the biogas residue mass and the biogas residue volume;
And determining the air inlet proportion based on the biogas residue density and the water content.
Specifically, the air inlet ratioThe calculation formula is as follows:
（1）
（2）
（3）
Wherein, For the initial air-in quantity,Is the quality of the biogas residue after primary biogas residue drying,Is the volume of the once dried biogas residue,Is the mass ratio of the initial air inlet amount to the mass of primary biogas residue with 15% of water content after drying,Is the density of the once dried biogas residue,For the density of primary biogas residue with 15% of water content after drying,For the water content of the once dried biogas residue,The water content of the primary biogas residue is 15% after drying.The ratio of the initial air inflow amount with the largest CO content generated in the limited anoxic combustion test to the mass of primary biogas residue with 15% of water content after drying is set.
It can be understood that the air inlet ratio determines the content of CO in the heat-carrying gas generated after primary biogas residue combustion, and the air inlet ratio is related to the density and the water content of the biogas residue after primary biogas residue drying. If the water content of the primary biogas residue after drying is high, more air is needed for combustion, and water is taken away. If the density of the primary biogas residue after drying is high, the primary biogas residue after drying is closely accumulated, the gaps are less, and the biogas residue at the moment is not fully combusted to easily generate CO, so that more air can be used.
According to the invention, the air inlet proportion is determined by obtaining the quality, the volume and the water content of the biogas residue after primary biogas residue drying, so that the primary biogas residue is ensured to be uniformly combusted, the combustion efficiency is improved, and meanwhile, more CO-containing heat-carrying gas is obtained to the greatest extent, so that the extraction amount of natural gas extracted from kitchen waste is further improved, the purity of the finally obtained mixed natural gas is ensured, and the maximization of the recycling of the kitchen waste is realized.
Specifically, in the step S5, extracting the heat-carrying gas based on the primary biogas residue includes:
Monitoring the CO content in the heat-carrying gas in the primary biogas residue combustion process, and adjusting the air inlet proportion based on the CO content percentage, wherein,
If the CO content percentage is lower than the preset CO content percentage, reducing the air inlet proportion or adding primary biogas residues into the combustion bin, wherein the water content of the primary biogas residues added into the combustion bin after drying is 15-20%.
Specifically, if the difference between the CO content percentage and the preset CO content percentage is smaller than the preset difference, judging that the air inlet proportion is reduced, and reducing the current air inlet amount to 75% -85% of the initial air inlet amount;
And if the difference value of the CO content percentage and the preset CO content percentage is larger than or equal to the preset difference value, determining that the biogas residue is put into the combustion bin once, determining the biogas residue input amount according to the initial air input amount and the air input proportion, and determining the water content of the biogas residue put into the combustion bin according to the difference value of the CO content percentage and the preset CO content percentage.
It can be appreciated that the primary biogas residue is put in for several times, the CO content in the heat-carrying gas is monitored in the primary biogas residue combustion process, and the air inlet proportion is adjusted based on the CO content percentage, so that the content of carbon monoxide extracted after the primary biogas residue combustion can reach the maximum, if the difference between the CO content percentage and the preset CO content percentage is smaller than the preset difference, the air inlet proportion is reduced, the primary biogas residue combustion is incomplete, thereby generating more CO, and if the air inlet proportion is too high, excessive carbon dioxide (CO 2) and water vapor are generated.
It can be understood that if the difference between the CO content percentage and the preset CO content percentage is greater than or equal to the preset difference, which indicates that much CO is generated at this time, continuously feeding biogas residues into the combustion bin once, determining the biogas residue feeding amount according to the initial feeding amount of air and the air feeding ratio of the last biogas residue combustion, and determining the water content of the biogas residues fed into the combustion bin according to the difference between the CO content percentage and the preset CO content percentage.
In implementation, the preset percentage of CO content ranges from 2% to 5%, preferably 3%. The mass of biogas residues is 10kg respectively after 2 times of feeding, the initial air inflow amount is 45kg, and the air inflow ratio is 2.25:1, wherein the content percentage of the generated CO is 2.56% and is lower than the preset content percentage of the CO by 3%, the air inlet amount is adjusted, the air inlet amount is reduced by 15% -25% of the initial air inlet amount, and preferably the reduction amount is 20% of the initial air inlet amount. The initial air inflow amount, the primary biogas residue throwing times, the air inflow proportion, the reduction amount, the value range and the optimal value of the preset CO content percentage are determined according to actual conditions, and are not repeated here.
According to the invention, the CO content in the heat-carrying gas generated in the primary biogas residue combustion process is monitored, the air inlet proportion is adjusted in real time, the CO yield of the target gas is improved, and the quality of the finally extracted mixed natural gas is improved, so that the purity of the finally obtained mixed natural gas is further ensured, and the maximization of the cyclic utilization of kitchen wastes is realized.
Specifically, in the step S5, the water content of the biogas residues put into the combustion bin is determined according to the difference between the CO content percentage and the preset CO content percentage.
It can be understood that if the difference between the CO content percentage and the preset CO content percentage is higher than the preset difference, it is indicated that the CO content percentage is low, the CO 2 content percentage is high, and the combustion is too complete, and it is determined that biogas residue with higher water content (i.e. the first water content) should be added into the combustion bin, so as to reduce the combustion efficiency and increase the generation of CO.
In practice, the preset difference value ranges from 0.2% to 0.5%, and preferably, the preset difference value is 0.3%. The first water content is 15% -20%, preferably 20%. The preset difference value, the value range of the first water content and the preferred value need to be determined according to limited tests according to different conditions of actual biogas residues, and are not described herein.
According to the difference between the CO content percentage and the preset CO content percentage, the water content of the biogas residues put into the combustion bin is determined, so that the CO content in the heat-carrying gas generated after primary biogas residue combustion is further improved, the extraction amount of natural gas extracted from kitchen waste is improved, the purity of the finally obtained mixed natural gas is ensured, and the maximization of the cyclic utilization of the kitchen waste is realized.
Specifically, in the step S5, the treatment of the primary biogas residue includes:
The primary biogas residue is subjected to drying treatment before combustion, so that the water content of the primary biogas residue is within the range of 10% -20%.
It can be appreciated that the primary biogas residue needs to be dried before being combusted, so that the water content of the primary biogas residue is reduced, the combustion efficiency is improved, and the subsequent combustion of the primary biogas residue is facilitated to provide heat for anaerobic fermentation. In the implementation, the water content of the primary biogas residue after drying is 10% -20%, and the preferable value of the water content is 15%. The value range and the optimal value of the water content of the primary biogas residue after drying are determined according to actual conditions, and are not repeated here.
According to the invention, the primary biogas residue is dried before being combusted, so that the water content of the primary biogas residue is reduced, the combustion efficiency is improved, and the subsequent combustion of the primary biogas residue is facilitated to provide heat for anaerobic fermentation. Thereby further improving the extraction quantity of the natural gas extracted from the kitchen waste, ensuring the purity of the finally obtained mixed natural gas and realizing the maximization of the cyclic utilization of the kitchen waste.
Referring to fig. 3, fig. 3 is a flowchart of the present invention for separating CO 2 from a mixed gas, specifically, in the step S6, a step of separating CO 2 from the mixed gas includes:
Step S61, obtaining the mole fraction of CO 2 in the mixed gas;
Step S62, separating CO 2 in the mixed gas through a gas membrane based on preset pressure and calculating the separation ratio of CO 2 in the mixed gas;
Step S63, adjusting the preset pressure based on the separation ratio, including:
And if the separation ratio is lower than the preset separation ratio, increasing the separation pressure.
In practice, the separation ratio is calculated as follows:
（4）
Wherein, ，The mole number of CO 2 in the mixed gas at the raw material side,The sum of the mole numbers of N gases in the mixed gas at the raw material side,，Is the mole fraction of CO 2 on the feed side (i.e., in the mixed gas).，For the number of moles of CO 2 in the permeate side mixed gas,In a mixed gas at the permeation sideSum of moles of individual gases, j=1..m,Is the mole fraction of CO 2 on the permeate side (i.e., after separation by the gas membrane).
In practice, the gas membranes used can be selected according to a predetermined separation ratio, and generally, the separation ratio of the selected gas membranes should be ensured to be within the range of 90% to 98% of the predetermined separation ratio. The separation ratio of the selected gas membrane may be adjusted in the range of the preset separation ratio according to actual situations, which is not described herein.
It is understood that the separation ratio is the ratio of the mole fraction of CO 2 in the mixed gas on the feed side before separation to the mole fraction of CO 2 on the permeate side after separation, and the initial concentration of CO 2 in the mixed gas without separation can be obtained by obtaining the mole fraction of CO 2 in the mixed natural gas, which provides basic data for the subsequent separation process. Then, CO 2 in the mixed gas was subjected to gas membrane separation based on a preset pressure and a separation ratio was calculated, and the separation effect was evaluated by the separation ratio. If the separation ratio is lower than the preset separation ratio, meaning that the effect of separating carbon dioxide is less than ideal, the separation effect can be improved by increasing the separation pressure. Conversely, if the separation ratio is greater than or equal to the pre-separation ratio, no adjustment of the separation pressure is required. In implementation, the preset pressure value range is 0.6MPa to 0.9MPa, preferably, the preset pressure is 0.7MPa, and the value range and the preferred value of the preset pressure need to be determined according to actual conditions, which are not described herein.
According to the invention, the preset pressure is adjusted by monitoring the separation ratio of CO 2 in the mixed gas in real time, so that the separation pressure in the gas membrane separation process is always in the optimal state, and the separation efficiency of CO 2 is improved. Thereby further improving the extraction quantity of the natural gas extracted from the kitchen waste, ensuring the purity of the finally obtained mixed natural gas and realizing the maximization of the cyclic utilization of the kitchen waste.
Referring to fig. 4, fig. 4 is a flow chart of the present invention for obtaining secondary biogas by high-temperature drying biogas slurry, specifically, in step S5, the step of high-temperature drying biogas slurry to separate secondary biogas includes:
heating the biogas slurry to a first temperature value, and then starting secondary biogas collection;
When the increment value of the secondary biogas yield in the preset time range is lower than a preset threshold value, judging that the secondary biogas collection is finished;
and increasing the first temperature value to a second temperature value, and evaporating the biogas slurry by water vapor based on the second temperature value to obtain secondary biogas residues.
It can be understood that secondary biogas and secondary biogas residues can be obtained again by drying the biogas slurry at high temperature, so that more natural gas is extracted. And (3) drying the biogas slurry at a high temperature, and collecting secondary biogas after the biogas slurry reaches the first temperature value. Monitoring the yield of the secondary biogas in the process of collecting the secondary biogas, and if the increased value of the yield of the secondary biogas is lower than a preset threshold value within a preset time range, indicating that the secondary biogas collection is finished. At the moment, the drying temperature is increased from the first temperature value to the second temperature value, and at the second temperature value, the water in the biogas slurry begins to evaporate, steam is generated, and the secondary biogas residue is finally obtained.
In implementation, the value range of the first temperature value is 40-50 ℃, preferably, the value range of the first temperature value is 45 ℃, the value range of the second temperature value is 80-95 ℃, preferably, the value range of the second temperature value is 90 ℃, the value range of the preset time range is 10-15 h, the value range of the preset threshold value for increasing the secondary biogas yield in the preset time range is 5 cm/h-10 cm/h, preferably, the value range of the preset threshold value is 7 cm/h, and the value ranges and the preferred value ranges of the first temperature value, the second temperature value, the preset time range and the preset threshold value need to be determined according to actual conditions and are not repeated here.
According to the invention, the biogas slurry is dried at high temperature, so that secondary biogas and secondary biogas residues can be effectively extracted from the biogas slurry again, and the energy utilization rate is greatly improved, thereby further improving the extraction amount of natural gas extracted from kitchen waste, ensuring the purity of the finally obtained mixed natural gas and realizing the maximization of the cyclic utilization of the kitchen waste.
Specifically, the purification further comprises dehydration, decarburization and desulfurization;
if the desulfurization is dry desulfurization, the purification sequence is dehydration, desulfurization and decarburization;
If the desulfurization is wet desulfurization or biological desulfurization, the purification sequence is desulfurization, dehydration and decarburization.
It is understood that the mixed gas obtained after anaerobic fermentation of the kitchen waste comprises grease, heat-carrying gas generated after primary biogas residue combustion, primary biogas generated by anaerobic fermentation and secondary biogas extracted from biogas slurry. The mixed gas is purified through the steps of dehydration, desulfurization and decarbonization, so that the purified mixed natural gas is obtained, pollutants generated when the mixed natural gas burns are reduced, the combustion value is increased, and the utilization value of the mixed natural gas is improved.
In a specific embodiment, the purification sequence is dehydration, desulfurization, decarbonization. Firstly, the mixed gas is dehydrated through a water separator, the dehydrated mixed gas enters a desulfurization tower to be contacted with adsorbents (such as active carbon, molecular sieve and the like) filled in the tower, and sulfides such as hydrogen sulfide in the mixed gas are adsorbed through the adsorbents, so that the purpose of desulfurization is achieved. And then removing carbon dioxide in the dehydrated and desulfurized mixed gas by using a membrane separation method. The material of the gas membrane for separating carbon dioxide in the membrane separation method may be cellulose acetate membrane, polysulfone membrane, polyethersulfone membrane, or the like.
In another specific embodiment, the purification sequence is desulfurization, dehydration, decarbonization. Firstly, the mixed gas is desulfurized in a wet desulfurization or biological desulfurization mode, and the wet desulfurization is carried out through chemical reaction of a solution (such as an alkaline solution) and sulfides such as hydrogen sulfide in the mixed gas, so that the mixed gas is converted into soluble sulfides, and the purpose of desulfurization is achieved. Biological desulfurization is to remove sulfides in mixed gas by using the metabolism of microorganisms. And (3) dehydrating the desulfurized mixed gas through a water separator. The dehydrated mixed gas enters a decarburization step, and carbon dioxide in the mixed gas is separated by a membrane separation method. The material of the gas membrane for separating carbon dioxide in the membrane separation method may be cellulose acetate membrane, polysulfone membrane, polyethersulfone membrane, or the like.
According to the invention, through the purification treatment such as dehydration, desulfurization and decarbonization on the mixed gas, the purified natural gas can reach the urban natural gas standard, the combustion value generated after the natural gas is combusted is higher, meanwhile, the pollutant emission during the combustion of the mixed natural gas is further reduced, the utilization value of the mixed natural gas is improved, the purity of the finally obtained mixed natural gas is further ensured, and the maximization of the recycling of kitchen wastes is realized.
Example 1
In this embodiment, an anoxic combustion test is performed on primary biogas residues extracted from kitchen waste to obtain content percentage data of CO in anoxic combustion under different water contents of the biogas residues, see table 1 below, wherein the content of air introduced is 30kg, and the mass of the biogas residues is 15kg.
TABLE 1
Example 1 shows that as the water content of the primary biogas residue increases, the water absorbs part of the heat, resulting in a decrease in combustion temperature, thereby affecting combustion efficiency, and in an incomplete combustion state, the corresponding CO content increases gradually. Meanwhile, as the water content of the primary biogas residue increases, the combustible substances in the biogas residue decrease, and the content of generated CO also decreases. In addition, the grease separated from the kitchen waste mainly comprises organic substances such as triglyceride, fatty acid, phospholipid, sterol and the like, and the substances react with oxygen in the air in the combustion process and generate CO in an incomplete combustion state, so that the CO content in the heat-carrying gas generated after the combustion of biogas residue and grease is higher than the CO content in the heat-carrying gas generated by the independent combustion of biogas residue.
Example 2
In this embodiment, an anoxic combustion test was performed using primary biogas residues extracted from kitchen waste to obtain content percentage data of CO of the biogas residues under different initial air inflow conditions, see table 2 below, wherein the biogas residues have the same mass of 15kg.
TABLE 2
Example 2 shows that under the same condition of primary biogas residue water content, primary biogas residue combustion is more complete and generated CO is less along with the increase of initial air inflow. And under the same initial air inflow, the CO content in the heat-carrying gas generated by the primary biogas residue and grease combustion with higher water content is more.
Example 3
In this example, in the method for extracting natural gas using kitchen waste, the above-mentioned implementation method was used to prepare biogas and CO respectively, and the natural gas therein was extracted by mixing, crushing, and dividing into three parts, the method of the present invention (primary biogas+secondary biogas+hot gas) was used to prepare natural gas, the anaerobic combustion was used to prepare CO (primary biogas+hot gas), and the conventional method was used to prepare biogas (primary biogas), wherein the effective extraction amount of natural gas is shown in table 3 below.
TABLE 3 Table 3
Example 3 shows that the method of the invention is based on primary biogas generated by anaerobic fermentation of kitchen waste, heat-carrying gas generated by combustion of primary biogas residue and grease, and secondary biogas generated by high-temperature drying of biogas slurry, and the mixed gas of the three has the maximum content of extracted CO.
Examples 1-3 above show that, by using the method of the present invention, grease and primary biogas residues with a water content of about 15% after drying are mixed and purified with heat-carrying gas generated by co-combustion under the air intake of 27kg, primary biogas generated by anaerobic fermentation based on kitchen waste, and secondary biogas generated by high-temperature drying of biogas slurry, and the extraction amount of natural gas is the greatest.
Thus far, the technical solution of the present invention has been described in connection with the preferred embodiments shown in the drawings, but it is easily understood by those skilled in the art that the scope of protection of the present invention is not limited to these specific embodiments. Equivalent modifications and substitutions for related technical features may be made by those skilled in the art without departing from the principles of the present invention, and such modifications and substitutions will be within the scope of the present invention.
Claims (10)
1. The natural gas extraction method based on the kitchen waste is characterized by comprising the following steps of:
step S1, sorting kitchen waste to obtain organic matters and inorganic matter impurities;
S2, separating grease from the organic matters to obtain grease and residual organic matters;
S3, crushing the residual organic matters to obtain organic slurry;
s4, mixing the organic slurry and anaerobic sludge according to a preset proportion, adding the mixture into an anaerobic reactor, and performing anaerobic fermentation to obtain primary biogas, biogas slurry and primary biogas residues;
s5, throwing the primary biogas residues and/or part of the grease into a combustion bin for anoxic combustion to generate a heat-carrying gas containing CO, and simultaneously, drying the biogas slurry at a high temperature generated by anoxic combustion to separate the biogas slurry into secondary biogas and secondary biogas residues;
The primary biogas residue is dried before being put into a combustion bin and then subjected to anoxic combustion, and the air inlet proportion is determined according to the water content and the biogas residue density of the primary biogas residue after being dried;
Step S6, purifying the heat-carrying gas generated by burning the primary biogas residues and/or the grease and the mixed gas of the secondary biogas extracted based on the biogas slurry and the primary biogas generated by anaerobic fermentation together to obtain mixed natural gas,
And determining a separation ratio of a gas membrane according to the carbon dioxide content in the mixed gas so as to separate the carbon dioxide in the mixed gas and obtain the purified mixed natural gas.
2. The method of extracting natural gas from kitchen waste according to claim 1, wherein in step S4, a plurality of fermentation sections are provided during anaerobic fermentation, and fermentation temperatures in the respective fermentation sections are different, comprising:
In an initial fermentation section, the fermentation temperature is a first fermentation temperature;
in the active fermentation section, the fermentation temperature is a second fermentation temperature;
in the stable fermentation section, the fermentation temperature is a first fermentation temperature;
Wherein the range of the first fermentation temperature is 30-40 ℃, and the range of the second fermentation temperature is 41-55 ℃.
3. The method according to claim 2, wherein in step S5, the fermentation temperature in the anaerobic reactor is adjusted by using the grease and/or the heat-carrying gas generated by the primary biogas residue combustion during the anaerobic fermentation, comprising:
if the fermentation temperature is lower than the preset temperature range, increasing the flow of the heat carrying gas;
And if the fermentation temperature is higher than the preset temperature range, reducing the flow of the heat carrying gas.
4. The method for extracting natural gas from kitchen waste as claimed in claim 3, wherein in the step S5, determining the air intake ratio for the primary anaerobic combustion according to the density and the water content of the biogas residue after the primary drying of the biogas residue comprises:
obtaining the quality, the volume and the water content of the biogas residue after primary drying;
Calculating the biogas residue density of the primary biogas residue based on the biogas residue mass and the biogas residue volume;
And determining the air inlet proportion based on the biogas residue density and the water content.
5. The method according to claim 4, wherein in the step S5, the extracting the heat-carrying gas based on the primary biogas residue comprises:
Monitoring the CO content in the heat-carrying gas in the primary biogas residue combustion process, and adjusting the air inlet proportion based on the CO content percentage, wherein,
If the CO content percentage is lower than the preset CO content percentage, reducing the air inlet proportion or adding primary biogas residues into the combustion bin, wherein the water content of the primary biogas residues added into the combustion bin after drying is 15-20%.
6. The method according to claim 5, wherein in step S5, the water content of the biogas residue introduced into the combustion chamber is determined based on the difference between the CO content percentage and the predetermined CO content percentage.
7. The method for extracting natural gas based on kitchen waste according to claim 6, wherein in the step S5, the treatment of the primary biogas residue comprises:
The primary biogas residue is subjected to drying treatment before combustion, so that the water content of the primary biogas residue is within the range of 10% -20%.
8. The method for extracting natural gas based on kitchen waste according to claim 1, wherein in the step S6, the step of separating CO 2 from the mixed gas comprises:
Step S61, obtaining the mole fraction of CO 2 in the mixed gas;
Step S62, separating CO 2 in the mixed gas through a gas membrane based on preset pressure and calculating the separation ratio of CO 2 in the mixed gas;
Step S63, adjusting the preset pressure based on the separation ratio, including:
And if the separation ratio is lower than the preset separation ratio, increasing the separation pressure.
9. The method for extracting natural gas based on kitchen waste according to claim 1, wherein in step S5, the step of drying the biogas slurry at a high temperature to separate the secondary biogas comprises:
heating the biogas slurry to a first temperature value, and then starting secondary biogas collection;
When the increment value of the secondary biogas yield in the preset time range is lower than a preset threshold value, judging that the secondary biogas collection is finished;
and increasing the first temperature value to a second temperature value, and evaporating the biogas slurry by water vapor based on the second temperature value to obtain secondary biogas residues.
10. The method for extracting natural gas based on kitchen waste according to claim 1, wherein the purification further comprises dehydration, decarbonization and desulfurization;
if the desulfurization is dry desulfurization, the purification sequence is dehydration, desulfurization and decarburization;
If the desulfurization is wet desulfurization or biological desulfurization, the purification sequence is desulfurization, dehydration and decarburization.
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