System and method for preparing biological aviation kerosene by biotransformation of biogas

Abstract

The invention discloses a system and a method for preparing biological aviation kerosene by biotransformation of biogas, and belongs to the technical field of biotransformation. The system comprises a kitchen waste anaerobic digestion unit, a biomass production unit, a grease extraction unit and a biological jet fuel production unit. The kitchen waste anaerobic digestion unit is used for converting kitchen waste into biogas; the biomass production unit is used for carrying out biological fermentation on methane and carbon dioxide in the biogas under the action of methanophilic bacteria and photoautotrophic microorganisms to obtain grease-containing biomass of the methanophilic bacteria and the photoautotrophic microorganisms; the grease extraction unit is used for breaking cells and purifying grease in the grease-containing biomass obtained in the biomass production unit; the biological aviation kerosene production unit is used for performing hydrodeoxygenation on the grease obtained by the grease extraction unit to obtain the biological aviation kerosene. Therefore, the system uses the kitchen waste as the raw material and fixes methane and carbon dioxide at the same time, so that the preparation cost of the biological jet fuel can be reduced, and the conversion rate of the biological jet fuel is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of bioconversion, and in particular relates to a system and a method for preparing bio-jet fuel by utilizing biogas bioconversion. Background Art

[0002] Greenhouse gas emissions from the aviation industry are one of the fastest growing sources of greenhouse gas emissions. Biojet fuel, as an aviation fuel produced from renewable resources, has the advantage of low carbon emissions and has become an effective way to achieve the goal of zero-carbon aviation. Although many companies are currently conducting research on the manufacture of biojet fuel, its high production cost still limits its large-scale promotion, and achieving low-cost, green, low-carbon and sustainable biojet fuel production faces huge challenges. Therefore, exploring practical and efficient biojet fuel manufacturing processes is of great practical significance to the development of the aviation industry.

[0003] Different types of raw materials can be converted into bio-jet fuel through different technical paths, including alcohol-based jet fuel, oil-based jet fuel, gas-based jet fuel and sugar-based jet fuel. However, the prices of alcohol and oil raw materials are relatively high. When using synthesis gas as raw material, the technology is difficult and the equipment cost is high. The conversion rate of sugar raw materials is low. Therefore, there is an urgent need for a low-cost, high-conversion method for preparing bio-jet fuel.

[0004] As an important part of urban domestic waste, food waste is generated in large quantities and grows rapidly. There are various treatment methods but the efficiency varies. The accumulation of large amounts of food waste has important impacts on the environment, ecology, economy and other aspects. Therefore, how to utilize food waste as a resource is an urgent problem to be solved in the process of urban development. Summary of the invention

[0005] In order to overcome the above-mentioned shortcomings of the prior art, the purpose of the present invention is to provide a system and method for preparing bio-jet fuel by biogas biological conversion, so as to solve the problems of high cost and low conversion rate of the existing bio-jet fuel preparation methods.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions: The first aspect of the present invention discloses a system for preparing bio-jet fuel by bio-conversion of biogas, characterized in that it comprises an anaerobic digestion unit for food waste, a biomass production unit, a fat extraction unit and a bio-jet fuel production unit connected in sequence; Anaerobic food waste digestion unit, which converts food waste into biogas containing methane and carbon dioxide, mixed with oxygen; A biomass production unit for converting a mixture of biogas containing methane and carbon dioxide and oxygen into oil-containing biomass; Oil extraction unit for converting oil-containing biomass into oil; Bio-jet fuel production unit, used to convert oils and fats into bio-jet fuel.

[0007] Preferably, it also includes a cogeneration unit, which is respectively connected to the anaerobic digestion unit of food waste, the biomass production unit, the oil extraction unit and the bio-jet fuel production unit, and is used to convert waste into electricity, heat and nitrogen-containing sludge.

[0008] Further preferably, the cogeneration unit includes a second anaerobic fermentation tank, a fourth flash tank, a fourth mixer, a combustion chamber and a seventh compressor, the second anaerobic fermentation tank is respectively connected to the food waste anaerobic digestion unit, the oil extraction unit and the bio-jet fuel production unit, the second anaerobic fermentation tank, the fourth flash tank, the fourth mixer and the combustion chamber are connected in sequence, and the seventh compressor is connected to the combustion chamber.

[0009] Preferably, the anaerobic digestion unit for food waste comprises an anaerobic fermentation tank, a first mixer and a desulfurization device connected in sequence; the biomass production unit comprises a fermentation tank and a second separator connected in sequence, the fermentation tank is connected to the desulfurization device, the fermentation tank is inoculated with methanophilic bacteria and photoautotrophic microorganisms, and the second separator is connected to the oil extraction unit.

[0010] Further preferably, the kitchen waste anaerobic digestion unit further comprises a grinder and a dryer, and the grinder, the dryer and the anaerobic fermentation tank are connected in sequence.

[0011] Preferably, the kitchen waste anaerobic digestion unit further comprises a second compressor and a pressure swing adsorption device, and the second compressor, the pressure swing adsorption device and the first mixer are connected in sequence.

[0012] Preferably, the biomass production unit further comprises a first storage tank and a first pump, wherein the first storage tank is used to provide the fermentation tank with buffer and nutrients required for biological reaction, and the first storage tank, the first pump and the fermentation tank are connected in sequence.

[0013] Preferably, the oil extraction unit comprises a second storage tank, a dissolved air flotation reactor, a cell disruption reactor and a separation and purification module connected in sequence, and the second storage tank is connected to the second separator; the bio-jet fuel production unit comprises a hydrodeoxygenation reactor, and the separation and purification module is connected to the hydrodeoxygenation reactor.

[0014] Further preferably, the oil extraction unit further comprises an extractive distillation tower and a vacuum distillation tower, and the separation and purification module, the extractive distillation tower, the vacuum distillation tower and the hydrodeoxygenation reactor are connected in sequence.

[0015] The second aspect of the present invention discloses a method for preparing bio-jet fuel by utilizing biogas biological conversion, comprising: performing anaerobically digestion on food waste to obtain biogas containing methane and carbon dioxide; mixing oxygen with the biogas containing methane and carbon dioxide to obtain an oxygen-biogas mixture; and subjecting the oxygen-biogas mixture to biological fermentation, separation, oil extraction, and hydrogenation and deoxygenation to generate bio-jet fuel.

[0016] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides a method for preparing bio-jet fuel by biogas bioconversion, which uses food waste as raw material, generates biogas through anaerobic digestion; uses biogas as raw material, introduces oxygen for biological fermentation and cell crushing to obtain oil, and then uses oil as raw material to synthesize bio-jet fuel, thereby resource-utilizing food waste bioconversion to obtain bio-jet fuel. In this method, firstly, using food waste as raw material to prepare bio-jet fuel can reduce production costs while reducing greenhouse gas emissions, and achieve the successful preparation of negative-cost carbon resources to high-value-added bio-jet fuel; secondly, biogas containing methane and carbon dioxide is produced by fermentation of food waste, and methane and carbon dioxide are simultaneously fixed by co-cultivation in the same bioreactor, which can improve the conversion efficiency of one carbon gas in biogas. Therefore, this method can solve the problems of high cost and low conversion rate in existing bio-jet fuel preparation methods.

[0017] Furthermore, the heat and power cogeneration unit can ferment the wastewater generated by the whole process with the solid biomass produced as a byproduct of the oil extraction unit to produce biogas, burn the biogas and unreacted methane waste gas and use them to generate electricity, and the generated electricity and heat energy can be used to supply power and heat for the system of the present invention, thereby realizing efficient energy recovery and utilization. The wastewater generated by the whole process and the solid biomass produced as a byproduct of the oil extraction unit are fermented to produce nitrogen-containing sludge, and the nitrogen-containing sludge is dehydrated and sold as a nitrogen fertilizer byproduct, thereby improving the economic efficiency of the process.

[0018] Furthermore, by installing a desulfurization device in the anaerobic digestion unit of food waste to remove hydrogen sulfide, it is possible to prevent corrosion of the system and avoid affecting the stable operation of the process system.

[0019] Furthermore, since a high yield cannot be guaranteed when the food waste particle size is large, a grinder is added to pre-grind the food waste to increase the biogas yield of anaerobic digestion of the food waste. Since the moisture content of food waste is generally as high as 60% to 80%, too high a moisture content will affect the subsequent reaction, so a dryer is added to reduce the moisture content of the food waste.

[0020] Furthermore, the second compressor and the pressure swing adsorption device provided in the anaerobic digestion unit of food waste can reduce process costs by directly preparing oxygen from air. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 The process flow chart of preparing bio-jet fuel by bio-conversion of biogas according to the present invention; Figure 2 Schematic diagram of the system for preparing bio-jet fuel by bio-conversion of biogas according to the present invention.

[0022] In the figure: 1- grinder; 2- dryer; 3- anaerobic fermentation tank; 4- first compressor; 5- first mixer; 6- LO-CAT; 7- first separator; 8- second compressor; 9- pressure swing adsorption device; 10- first centrifuge; 11- third compressor; 12- fermentation tank; 13- second separator; 14- first storage tank; 15- first pump; 16- second storage tank; 17- second pump; 18- dissolved air flotation reactor; 19- fourth compressor; 20- air storage tank; 21- cell disruption reactor; 22 -second centrifuge; 23-extractive distillation tower; 24-vacuum distillation tower; 25-fifth compressor; 26-first heater; 27-hydrodeoxygenation reactor; 28-first flash tank; 29-first cooler; 30-second flash tank; 31-third flash tank; 32-sixth compressor; 33-third mixer; 34-second anaerobic fermentation tank; 35-fourth flash tank; 36-seventh compressor; 37-fourth mixer; 38-combustion chamber; 39-gas turbine; 40-second cooler; 41-third centrifuge. DETAILED DESCRIPTION

[0023] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0024] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0025] In this article, the term "kitchen waste" refers to a mixture of food residues, food processing waste and waste cooking oils generated in food processing, catering services, unit catering and other activities other than residents' daily lives. It mainly comes from collective catering units such as the catering industry and canteens, including leftovers, fruit peels and cores, vegetable leaves, animal offal, bones and other perishable waste. Its characteristics are high organic content: it contains a large amount of organic matter such as starch, cellulose, protein, etc., which are easy to decompose under suitable conditions; high water content: the water content is usually high, and it is difficult to collect and treat; perishability: due to the large amount of organic matter and water, kitchen waste is easy to rot and deteriorate, produce bad odors and breed bacteria.

[0026] Herein, the term "waste" includes waste gas, waste residue and waste water. The term "waste residue" includes digestate and biomass residue.

[0027] See also Figure 1 The present invention provides a method for preparing bio-jet fuel by bioconversion of biogas, comprising: (1) Anaerobic digestion of food waste: The food waste is pre-treated by grinding and drying and then anaerobically digested to obtain biogas containing methane and carbon dioxide. Oxygen is mixed with the biogas containing methane and carbon dioxide to obtain an oxygen-biogas mixture. (2) Biomass production: The oxygen-biogas mixture is subjected to biological fermentation, the fermentation product is subjected to gas-liquid separation and solid-liquid separation, and the solid precipitate is taken to obtain oil-containing biomass; (3) Oil extraction: The obtained oil-containing biomass is subjected to cell crushing, separation and purification to obtain oil; (4) Bio-jet fuel production: The obtained oil is subjected to a hydrogenation and deoxygenation reaction to obtain bio-jet fuel.

[0028] Furthermore, a heat and power cogeneration step may be added to the above method.

[0029] (5) Cogeneration: The waste residues and wastewater from the entire process are subjected to anaerobic fermentation to produce biogas and nitrogen-containing sludge. The biogas and waste gas are mixed and burned. The combustion gas is used to generate electricity and heat through heat exchange equipment to supply the electricity and heat energy required for the entire process. The nitrogen-containing sludge is sold as a by-product of nitrogen fertilizer.

[0030] The present invention provides a system for preparing bio-jet fuel by utilizing biogas bioconversion, comprising a restaurant waste anaerobic digestion unit, a biomass production unit, a grease extraction unit and a bio-jet fuel production unit which are connected in sequence.

[0031] The anaerobic digestion unit of food waste is used for anaerobic fermentation of food waste after grinding and drying to produce biogas containing methane and carbon dioxide, and mix it with oxygen to form an oxygen-biogas mixture to supply microbial growth.

[0032] The biomass production unit is used to allow the oxygen-biogas mixture to undergo biological fermentation under the action of methanophilic bacteria and photoautotrophic microorganisms, and to perform gas-liquid separation and solid-liquid separation on the biological fermentation product to obtain oil-containing biomass.

[0033] The oil extraction unit is used to break the cells of oil-containing biomass, extract and purify it through acid-base method to obtain oil.

[0034] The biojet fuel production unit is used to hydrodeoxygenate oils and fats to produce biojet fuel.

[0035] Furthermore, a cogeneration unit may be added to the above system.

[0036] The cogeneration unit is used to produce biogas and nitrogen-containing sludge through anaerobic fermentation of waste residues and wastewater in the entire process, and utilizes the combustion of biogas to supply the required electricity and heat energy for the entire process.

[0037] The present invention is described in further detail below in conjunction with embodiments: A system for preparing bio-jet fuel by bioconversion of biogas, see Figure 2 , including a restaurant kitchen waste anaerobic digestion unit, a biomass production unit, a fat extraction unit and a bio-jet fuel production unit connected in sequence. It also includes a heat and power cogeneration unit, which is connected to the restaurant kitchen waste anaerobic digestion unit, the biomass production unit, the fat extraction unit and the bio-jet fuel production unit.

[0038] The anaerobic digestion unit for food waste comprises a grinder 1, a dryer 2, an anaerobic fermentation tank 3, a first compressor 4, a first mixer 5, a LO-CAT 6, a first separator 7, a second compressor 8, a pressure swing adsorption device 9 and a first centrifuge 10. The grinder 1 is used to receive and grind the food waste, the discharge port of the grinder 1 is connected to the feed port of the dryer 2, the outlet of the dryer 2 is connected to the inlet of the anaerobic fermentation tank 3, the anaerobic fermentation tank 3 is used to ferment the food waste into biogas containing methane and carbon dioxide, the anaerobic fermentation tank 3 is provided with a biogas outlet and a waste outlet, the biogas outlet of the anaerobic fermentation tank 3 is connected to the inlet of the first compressor 4, the first compressor 4 is used to compress the biogas generated by anaerobic fermentation; the waste outlet of the anaerobic fermentation tank 3 is connected to the first centrifuge 10, the first centrifuge 10 is provided with a waste gas outlet and a waste residue and waste water outlet, the first centrifuge 10 is used to separate the waste generated by anaerobic fermentation; the outlet of the first compressor 4 is connected to the inlet of the first mixer 5. The second compressor 8 is used to receive and pressurize air, and the outlet of the second compressor 8 is connected to the inlet of the pressure swing adsorption device 9; the pressure swing adsorption device 9 is used to separate oxygen from the pressurized air, and the oxygen outlet of the pressure swing adsorption device 9 is connected to the inlet of the first mixer 5. The first mixer 5 is used to mix the biogas generated by the fermentation of food waste with the oxygen separated from the air to obtain an oxygen-biogas mixture; the outlet of the first mixer 5 is connected to the inlet of the LO-CAT 6, and the LO-CAT 6 is used to remove hydrogen sulfide from the oxygen-biogas mixture. The outlet of the LO-CAT 6 is connected to the inlet of the first separator 7, and the first separator 7 is used to remove sulfur from the oxygen-biogas mixture and output an oxygen-biogas mixture that does not contain hydrogen sulfide and sulfur.

[0039] The biomass production unit includes a third compressor 11, a fermentation tank 12, a second separator 13, a first storage tank 14 and a first pump 15. The outlet of the first separator 7 is connected to the inlet of the third compressor 11, and the third compressor 11 is used to pressurize the oxygen-biogas mixture of the anaerobic digestion unit of the food waste and transport it to the fermentation tank 12. The first storage tank 14 is used to receive buffer and nutrients for biological reaction; the buffer includes but is not limited to pH buffer, and the nutrients include but are not limited to nitrogen sources and trace elements. The outlet of the first storage tank 14 is connected to the inlet of the first pump 15, and the outlet of the first pump 15 is connected to the inlet of the fermentation tank 12. The first pump 15 is used to pressurize the buffer and nutrients and transport them to the fermentation tank 12; the fermentation tank 12 is inoculated with methanophilic bacteria and photoautotrophic microorganisms, and the fermentation tank 12 is used to allow the oxygen-biogas mixture, buffer and nutrients that do not contain hydrogen sulfide to be in the fermentation tank 12. Biological fermentation is carried out under the action of methanophilic bacteria and photoautotrophic microorganisms to obtain fermentation liquid, which is formed by converting carbon dioxide and methane in biogas into oil-containing biomass; the outlet of the fermentation tank 12 is connected to the inlet of the second separator 13, and the second separator 13 is used to separate the biogas and fermentation liquid remaining after biological fermentation; the second separator 13 body is provided with a fermentation liquid outlet and a waste gas outlet of the second separator 13, and the waste gas outlet of the second separator 13 and the waste gas outlet of the first centrifuge 10 are both connected to the inlet of the sixth compressor 32, and the sixth compressor 32 is used to compress the waste gas.

[0040] The oil extraction unit includes a second storage tank 16, a second pump 17, a dissolved air flotation reactor 18, a fourth compressor 19, an air storage tank 20, a cell disruption reactor 21, a second centrifuge 22, an extractive distillation tower 23 and a vacuum distillation tower 24. The fermentation liquid outlet of the second separator 13 from the biomass production unit is connected to the second storage tank 16, the second storage tank 16 is used to receive the fermentation liquid from the biomass production unit, the outlet of the second storage tank 16 is connected to the inlet of the second pump 17, the second pump 17 is used to pressurize the fermentation liquid, the outlet of the second pump 17 is connected to the inlet of the dissolved air flotation reactor 18, and the dissolved air flotation reactor 18 is used to separate the fermentation liquid. The fourth compressor 19 is used to receive and compress air, the outlet of the fourth compressor 19 is connected to the air storage tank 20, the air storage tank 20 is used to store compressed air, and the outlet of the air storage tank 20 is connected to the inlet of the dissolved air flotation reactor 18 for dissolving air. The outlet of the dissolved air flotation reactor 18 is connected to the inlet of the cell disruption reactor 21, which is used to disrupt the separated fermentation liquid, release the oil in the cells through cell disruption, and obtain a mixed oil liquid; the outlet of the cell disruption reactor 21 is connected to the inlet of the second centrifuge 22, and the second centrifuge 22 is used to separate the mixed oil liquid; the second centrifuge 22 body is provided with a oil outlet and a waste residue and wastewater outlet, the oil outlet of the second centrifuge 22 is connected to the inlet of the extraction distillation tower 23, the extraction distillation tower 23 is used to extract the oil in the mixed oil liquid by the extraction agent, the outlet of the extraction distillation tower 23 is connected to the inlet of the vacuum distillation tower 24, the vacuum distillation tower 24 is used to separate the extraction agent and the extracted oil, the extraction agent flows out through the top of the vacuum distillation tower 24, and enters the extraction distillation tower 23 for reuse, the bottom outlet of the vacuum distillation tower 24 is connected to the inlet of the first heater 26, and the extracted oil flows into the bio-jet fuel production unit from the bottom outlet. The waste residue and waste water outlets of the second centrifuge 22 and the waste residue and waste water outlets of the first centrifuge 10 are all connected to the third mixer 33 .

[0041] The bio-jet fuel production unit includes a fifth compressor 25, a first heater 26, a hydrodeoxygenation reactor 27, a first flash tank 28, a first cooler 29, a second flash tank 30 and a third flash tank 31. The fifth compressor 25 is used to receive and compress hydrogen. The outlet of the fifth compressor 25, the outlet of the bottom of the vacuum distillation tower 24 in the oil extraction unit and the third flash tank 31 are all connected to the inlet of the first heater 26. The first heater 26 is used to heat oil and compress hydrogen. The outlet of the first heater 26 is connected to the inlet of the hydrodeoxygenation reactor 27. The hydrodeoxygenation reactor 27 is used to hydrodeoxygenate oil to generate bio-jet fuel. The outlet of the hydrodeoxygenation reactor 27 is connected to the inlet of the first flash tank 28. The first flash tank 28 is used to separate the incompletely reacted hydrogen for reuse. The first flash tank 28 has a A hydrogen outlet and a bio-jet fuel outlet are provided. The hydrogen outlet of the first flash tank 28 is connected to the third flash tank 31, and the bio-jet fuel outlet of the first flash tank 28 is connected to the inlet of the first cooler 29; the outlet of the first cooler 29 is connected to the inlet of the second flash tank 30. The second flash tank 30 is used for purifying bio-jet fuel. A bio-jet fuel outlet and a waste residue outlet are provided on the body of the second flash tank 30. The waste residue outlet of the second flash tank 30 is connected to the third mixer 33. The purified bio-jet fuel flows out from the bio-jet fuel outlet of the second flash tank 30, and the separated waste residue enters the third mixer 33 from the waste residue outlet of the second flash tank 30.

[0042] The cogeneration unit includes a sixth compressor 32, a third mixer 33, a second anaerobic fermentation tank 34, a fourth flash tank 35, a seventh compressor 36, a fourth mixer 37, a combustion chamber 38, a gas turbine 39, a second cooler 40 and a third centrifuge 41. The waste residue and wastewater generated in the whole process enter the second anaerobic fermentation tank 34 through the third mixer 33, and waste gas and nitrogen-containing sludge are generated by fermentation in the second anaerobic fermentation tank 34. The outlet of the second anaerobic fermentation tank 34 is connected to the liquid inlet of the fourth flash tank 35. The fourth flash tank 35 body is provided with a waste gas outlet and a nitrogen-containing sludge outlet. The waste gas outlet is connected to the inlet of the fourth mixer 37, and the outlet of the fourth mixer 37 is connected to the inlet of the combustion chamber 38. The waste gas separated from the fourth flash tank 35 and the waste gas collected by the sixth compressor 32 are mixed in the fourth mixer 37 and then enter the combustion chamber 38, and are mixed with the compressed air from the seventh compressor 36 for combustion. The outlet of the combustion chamber 38 is connected to the inlet of the gas turbine 39, and the outlet of the gas turbine 39 is connected to the inlet of the second cooler 40, and the process tail gas is output through the second cooler 40. The nitrogen-containing sludge outlet of the fourth flash tank 35 is connected to the inlet of the third centrifuge 41, and the nitrogen-containing sludge produced by the fermentation of the fourth flash tank 35 is centrifuged by the third centrifuge 41 to output the process byproduct nitrogen fertilizer.

[0043] In the whole system, the arrangement of the first compressor 4, the second compressor 8, the third compressor 11, the fourth compressor 19, the fifth compressor 25, the sixth compressor 32 and the seventh compressor 36 can provide power for the operation of the system by compressing gas.

[0044] A method for preparing bio-jet fuel using the above system specifically comprises: (1) Food waste anaerobic digestion unit: Food waste with a moisture content of 75% is ground into food waste particles of 1.4-2.0 mm in a grinder 1; then it is dehydrated in a dryer 2, and then anaerobically fermented in an anaerobic fermentation tank 3 at 35°C and a pressure of 1 bar to generate biogas containing methane and carbon dioxide, and waste is generated at the same time. The biogas in the anaerobic fermentation tank 3 is compressed in the first compressor 4 and pressurized to 3 bar, and enters the first mixer 5. At the same time, the air is pressurized to 3 bar in the second compressor 8, and then oxygen is separated in the pressure swing adsorption device 9 and enters the first mixer 5. The biogas in the first mixer 5 is mixed with oxygen to obtain an oxygen-biogas mixture. The oxygen-biogas mixture is desulfurized in the LO-CAT 6 and converted into sulfur and desulfurized biogas; then the sulfur is desulfurized in the first separator 7 and the oxygen-desulfurized biogas mixture is output.

[0045] The waste generated by the anaerobic fermentation tank 3 is separated into waste gas, waste residue and waste water in the first centrifuge 10 . The waste gas enters the sixth compressor 32 , and the waste residue and waste water enter the third mixer 33 .

[0046] (2) Biomass production unit: Sodium hydroxide solution is used as a buffer to adjust the pH value in the fermentation tank so that the fermentation conditions are maintained at a weakly acidic pH value of about 6.0 to 6.5. Ammonia is used as a nutrient for biological fermentation. After the sodium hydroxide solution and ammonia are mixed in the first storage tank 14, they are pressurized to 2 bar by the first pump 15 and then enter the fermentation tank 12. The oxygen-desulfurized biogas mixture from the anaerobic digestion unit of food waste enters the fermentation tank 12. The oxygen-desulfurized biogas mixture, sodium hydroxide solution and ammonia are fermented at 30°C and 1 bar with the participation of methanophilic bacteria and photoautotrophic microorganisms, and the methane and carbon dioxide in the desulfurized biogas are converted into oil-containing biomass to obtain fermentation liquid. The fermentation liquid in the fermentation tank 12 and the remaining oxygen-desulfurized biogas mixture are separated in the second separator 13, and the separated fermentation liquid is received by the second storage tank 16.

[0047] The remaining oxygen-desulfurized biogas mixture enters the sixth compressor 32 as exhaust gas.

[0048] (3) Oil extraction unit: The fermentation liquid from the second separator 13 enters the second storage tank 16, is pressurized to 2 bar by the second pump 17, and then enters the dissolved air flotation reactor 18. After the air is pressurized to 3 bar by the fourth compressor 19, it enters the dissolved air flotation reactor 18 through the air storage tank 20. At the same time, 100 mg / L flocculant is added to the dissolved air flotation reactor 18 to assist in oil recovery. In the dissolved air flotation reactor 18, air is introduced into the fermentation liquid to generate tiny bubbles, thereby separating the oil-containing biomass and waste residue in the fermentation liquid. Under the action of the flocculant, the recovery efficiency of the oil-containing biomass can reach 90%. 2 wt% sulfuric acid and 1 wt% sodium hydroxide are added to the separated oil-containing biomass to perform cell disruption in the cell disruption reactor 21 to obtain an oil mixture; the oil mixture is preliminarily separated into oil-containing liquid, waste residue and wastewater in the second centrifuge 22. The separated oil-containing liquid is extracted in the extractive distillation tower 23 (with hexane as the extractant), with an extraction rate of 90%, and then distilled in the vacuum distillation tower 24, and high-purity oil flows out from the bottom outlet of the vacuum distillation tower 24.

[0049] The waste residue and waste water separated by the second centrifuge 22 enter the third mixer 33 for subsequent treatment.

[0050] During the distillation process, hexane flows out from the top of the vacuum distillation tower 24 and enters the extractive distillation tower 23 for reuse.

[0051] (4) Bio-jet fuel production unit: The hydrogen is pressurized to 20 bar by the fifth compressor 25, heated to 390°C by the first heater 26, and then subjected to a hydrodeoxygenation reaction with the high-purity oil extracted by the oil extraction unit in the hydrodeoxygenation reactor 27. The reaction conditions are 390°C and 20 bar to produce crude bio-jet fuel with a conversion rate of up to 99%. The crude bio-jet fuel is cooled to 25°C by the first cooler 29, and then further purified by the second flash tank 30 to obtain bio-jet fuel with a purity of 98.7%.

[0052] The excess hydrogen is separated through the first flash tank 28 and enters the third flash tank 31, and then re-enters the first heater 26 from the third flash tank 31 to be heated to 390°C for reuse.

[0053] (5) Cogeneration unit: The waste residue and wastewater generated in the whole process are mixed and enter the second anaerobic fermentation tank 34. Under the conditions of 35°C and 1 bar, waste gas and nitrogen-containing sludge are produced by anaerobic fermentation. After that, the waste gas and nitrogen-containing sludge are separated in the fourth flash tank 35.

[0054] The waste gas separated from the fourth flash tank 35 is mixed with the waste gas generated by the anaerobic fermentation unit of the food waste and the biomass production unit in the fourth mixer 37 and then enters the combustion chamber 38. At the same time, the air from the seventh compressor 36 is compressed to 3 bar and then enters the combustion chamber 38. Methane, hydrogen and other waste gases are burned with oxygen in the combustion chamber 38 at 1600°C. The combustion process generates a large amount of high-temperature waste heat, which is used to generate electricity through the gas turbine 39. At the same time, high-temperature waste heat is obtained and used to heat the anaerobic digestion of food waste, biomass production, oil extraction and bio-jet fuel production units through heat exchange equipment. The high-temperature gas generated by the gas turbine 39 for power generation is cooled by the second cooler 40 to obtain cooling gas, which is discharged as process tail gas.

[0055] The nitrogen-containing sludge separated in the fourth flash tank 35 is centrifuged in the third centrifuge 41 to become a process by-product nitrogen fertilizer with a moisture content of about 52%, which is used for agricultural production.

[0056] The present invention constructs a process simulation for preparing bio-jet fuel from biogas, analyzes the energy flow and material flow, and couples the components to determine the corresponding key operating parameters, and provides a technical path for preparing bio-jet fuel directly from biogas produced by anaerobic digestion of food waste through bio-fermentation technology. This process can reduce the dependence on fossil fuels in the process of social development and realize the preparation of high-value-added bio-jet fuel from biogas derived from negative-cost food waste.

[0057] The above contents are only for explaining the technical idea of ​​the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. A system for preparing bio-jet fuel by bioconversion of biogas, characterized in that: It includes a restaurant kitchen waste anaerobic digestion unit, a biomass production unit, a fat extraction unit and a bio-jet fuel production unit connected in sequence; Anaerobic food waste digestion unit, which converts food waste into biogas containing methane and carbon dioxide, mixed with oxygen; A biomass production unit for converting a mixture of methane and carbon dioxide and oxygen into oily biomass; Oil extraction unit for converting oil-containing biomass into oil; Bio-jet fuel production unit, used to convert oils and fats into bio-jet fuel.

2. The system for preparing bio-jet fuel by biogas bioconversion according to claim 1, characterized in that: It also includes a cogeneration unit, which is respectively connected to the anaerobic digestion unit of food waste, the biomass production unit, the oil extraction unit and the bio-jet fuel production unit. The cogeneration unit is used to convert waste into electricity, heat energy and nitrogen-containing sludge.

3. The system for preparing bio-jet fuel by biogas bioconversion according to claim 2, characterized in that: The cogeneration unit comprises a second anaerobic fermentation tank (34), a fourth flash tank (35), a fourth mixer (37), a combustion chamber (38) and a seventh compressor (36); the second anaerobic fermentation tank (34) is respectively connected to the kitchen waste anaerobic digestion unit, the oil extraction unit and the bio-jet fuel production unit; the second anaerobic fermentation tank (34), the fourth flash tank (35), the fourth mixer (37) and the combustion chamber (38) are connected in sequence; and the seventh compressor (36) is connected to the combustion chamber (38).

4. A system for preparing bio-jet fuel by biogas bioconversion according to any one of claims 1 to 3, characterized in that: The kitchen waste anaerobic digestion unit comprises an anaerobic fermentation tank (3), a first mixer (5) and a desulfurization device which are connected in sequence; the biomass production unit comprises a fermentation tank (12) and a second separator (13) which are connected in sequence, the fermentation tank (12) is connected to the desulfurization device, the fermentation tank (12) is inoculated with methanophilic bacteria and photoautotrophic microorganisms, and the second separator (13) is connected to the oil extraction unit.

5. The system for preparing bio-jet fuel by biogas bioconversion according to claim 4, characterized in that: The kitchen waste anaerobic digestion unit further comprises a grinder (1) and a dryer (2), and the grinder (1), the dryer (2) and the anaerobic fermentation tank (3) are connected in sequence.

6. The system for preparing bio-jet fuel by biogas bioconversion according to claim 4, characterized in that: The kitchen waste anaerobic digestion unit further comprises a second compressor (8) and a pressure swing adsorption device (9), and the second compressor (8), the pressure swing adsorption device (9) and the first mixer (5) are connected in sequence.

7. The system for preparing bio-jet fuel by biogas bioconversion according to claim 4, characterized in that: The biomass production unit further comprises a first storage tank (14) and a first pump (15). The first storage tank (14) is used to provide the fermentation tank (12) with a buffer and nutrients required for a biological reaction. The first storage tank (14), the first pump (15) and the fermentation tank (12) are connected in sequence.

8. A system for preparing bio-jet fuel by biogas bioconversion according to any one of claims 1 to 3, characterized in that: The oil extraction unit comprises a second storage tank (16), a dissolved air flotation reactor (18), a cell disruption reactor (21) and a separation and purification module which are connected in sequence, the second storage tank (16) being connected to the second separator (13); the bio-jet fuel production unit comprises a hydrodeoxygenation reactor (27), and the separation and purification module being connected to the hydrodeoxygenation reactor (27).

9. The system for preparing bio-jet fuel by biogas bioconversion according to claim 8, characterized in that: The oil extraction unit further comprises an extractive distillation tower (23) and a vacuum distillation tower (24), and the separation and purification module, the extractive distillation tower (23), the vacuum distillation tower (24) and the hydrodeoxygenation reactor (27) are connected in sequence.

10. A method for preparing bio-jet fuel by bioconversion of biogas, characterized in that: Anaerobic digestion of food waste produces biogas containing methane and carbon dioxide; oxygen is mixed with the biogas containing methane and carbon dioxide to produce an oxygen-biogas mixture; the oxygen-biogas mixture is processed through biological fermentation, separation, oil extraction, and hydrogenation and deoxygenation to produce biojet fuel.

Images