Kitchen waste resource recycling system and method

Abstract

The present application relates to the field of solid waste treatment and resource utilization, and particularly relates to a kitchen waste resource recycling system and method, which efficiently extracts organic matter in kitchen waste, uses different types of microorganisms to fully degrade various organic matters in kitchen waste, produces industrial raw materials such as lactic acid and hexanoic acid, produces clean energy such as biological natural gas and liquid food-grade carbon dioxide, realizes deep high-value resource utilization of kitchen waste, and realizes maximum resource recycling and utilization. The present application fully utilizes the organic matter in kitchen waste, obtains industrial raw materials (organic acids), biological natural gas (methane content of more than 97%) and food-grade liquid carbon dioxide, realizes efficient conversion of kitchen waste and high-value and diversification of conversion products.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of solid waste treatment and resource utilization, and in particular to a kitchen waste resource recycling system and method. BACKGROUND

[0002] Kitchen waste is food waste generated in daily life of residents in restaurants, hotels, and canteens of units, including vegetable leaves, leftovers, fruit peels, eggshells, etc., and has the characteristics of high oil content, high water content, and rich organic matter content. The organic matter is mainly composed of sugars (starch), fats, and proteins. These physical properties cause kitchen waste to have hazards such as environmental sanitation destruction, groundwater pollution, and food chain safety hazards.

[0003] Although kitchen waste has many hazards, it is rich in organic matter and has very high recycling value. Resource utilization of kitchen waste can turn waste into treasure and produce valuable raw materials and energy. The current mainstream treatment process is "pretreatment + anaerobic biogas production + synergistic incineration", but the comprehensive resource utilization rate of this technology is not high, and the resource utilization products produced are only clean energy biogas. The revenue model of biogas is heat production, power generation, and purification of natural gas. Although there is a certain economic benefit, it is not very impressive. In addition to the high cost of waste treatment, these kitchen waste treatment projects often have very little economic benefit. For kitchen waste treatment projects, it is urgent to improve product value, increase carbon emission reduction, and achieve economic and ecological benefits. SUMMARY

[0004] The present application provides a kitchen waste resource recycling system and method to solve the problem of kitchen waste treatment projects having very little economic benefit in the prior art. The organic matter in kitchen waste is efficiently extracted, and different types of microorganisms are used to fully degrade the organic matter in kitchen waste to produce industrial raw materials such as lactic acid and hexanoic acid, clean energy such as biogas, and liquid food-grade carbon dioxide, achieving deep high-value resource utilization of kitchen waste and maximizing resource recycling.

[0005] The present application provides a kitchen waste resource recycling system, comprising:

[0006] An organic matter extraction unit is used to separate and extract the organic matter from the kitchen waste to obtain slurry and impurities.

[0007] An organic acid production unit is connected to the organic matter extraction unit and is used to receive the slurry prepared by the organic matter extraction unit and perform directional fermentation and purification of organic acids to obtain organic acids.

[0008] A biogas production unit is connected to the organic acid production unit and is used to receive the organic acid fermentation residues produced by the organic acid production unit and perform biogas fermentation.

[0009] A methane-dioxide carbon separation unit is connected to the biogas production unit and used to receive the biogas produced by the biogas production unit and perform cooling separation to obtain methane and dioxide carbon;

[0010] A biogas residue and slurry separation unit is connected to the biogas production unit and used to receive the biogas fermentation residue produced by the biogas production unit and perform solid-liquid separation and then discharge for treatment.

[0011] According to the kitchen waste recycling system, the organic matter extraction unit comprises a pulper, and a sieve plate is detachably arranged at an outlet of the pulper to form an impurity slagging-off port above the sieve plate and a pulp discharging port below the sieve plate.

[0012] According to the kitchen waste recycling system, the organic acid production unit comprises:

[0013] An organic acid fermentation tank is used to receive the pulp prepared by the organic matter extraction unit and perform organic acid fermentation.

[0014] An oxidation-reduction control device is installed in the organic acid fermentation tank and used to control the oxidation-reduction potential value in the organic acid fermentation tank.

[0015] An organic acid purification device is connected to the organic acid fermentation tank, and the organic acid purification device is provided with an organic acid outlet and an organic acid fermentation residue outlet.

[0016] An organic acid storage tank is connected to the organic acid outlet of the organic acid purification device.

[0017] According to the kitchen waste recycling system, the oxidation-reduction control device comprises an oxidation-reduction potential online analyzer, an oxidizing gas supply end and a reducing gas supply end, so as to monitor the oxidation-reduction potential value in the organic acid fermentation tank through the oxidation-reduction potential online analyzer and control the oxidizing gas supply end or the reducing gas supply end to ventilate the organic acid fermentation tank.

[0018] According to the kitchen waste recycling system, the organic acid purification device comprises a solid-liquid separation device and a membrane separation system.

[0019] The membrane separation system comprises a main separation pipeline and a plurality of bypass pipelines, and an ultrafiltration membrane, a nanofiltration membrane and a reverse osmosis membrane are sequentially connected in series on the main separation pipeline, and the bypass pipelines are connected in parallel to the ultrafiltration membrane, the nanofiltration membrane and the reverse osmosis membrane on the main separation pipeline.

[0020] The solid-liquid separation device is connected to the organic acid fermentation tank, a liquid phase outlet of the solid-liquid separation device is communicated with the main separation pipeline, and the main separation pipeline is communicated with the organic acid storage tank.

[0021] The separation residual liquid outlets of the ultrafiltration membrane, the nanofiltration membrane and the reverse osmosis membrane are mixedly communicated with a solid phase outlet of the solid-liquid separation device to form the organic acid fermentation residue outlet.

[0022] According to the kitchen waste resource recycling system provided by the application, the biogas production unit comprises an anaerobic fermentation tank, the anaerobic fermentation tank is provided with an organic acid fermentation residue inlet, a biogas outlet and a biogas fermentation residue outlet, the anaerobic fermentation tank is communicated with the organic acid production unit through the organic acid fermentation residue inlet and is used for receiving the organic acid fermentation residue generated by the organic acid production unit, the anaerobic fermentation tank is communicated with the methane carbon dioxide separation unit through the biogas outlet, and the anaerobic fermentation tank is communicated with the biogas residue and biogas liquid separation unit through the biogas fermentation residue outlet.

[0023] According to the kitchen waste resource recycling system provided by the application, the methane carbon dioxide separation unit comprises a first cooler, a first separation tower, a second cooler and a second separation tower which are sequentially communicated.

[0024] The first cooler is communicated with the biogas production unit and receives the biogas generated by the biogas production unit.

[0025] The first separation tower is provided with a heavy impurity outlet, the heavy impurity outlet is externally connected with a flare through a pipeline and is communicated with the redox control device of the organic acid production unit through another pipeline.

[0026] The second separation tower is externally connected with a carbon dioxide storage tank and a biogas storage tank.

[0027] According to the kitchen waste resource recycling system provided by the application, the methane carbon dioxide separation unit further comprises a water storage tank, a vacuum pump and a compressor.

[0028] The vacuum pump is communicated with the water storage tank, an outlet of a cooling system of the first cooler and an outlet of a cooling system of the second cooler are respectively communicated with an inlet of the vacuum pump, and an inlet of the cooling system of the first cooler and an inlet of the cooling system of the second cooler are respectively communicated with an outlet of the vacuum pump.

[0029] The compressor is connected in series on a pipeline through which the first cooler is communicated with the biogas production unit.

[0030] According to the kitchen waste resource recycling system provided by the application, the biogas residue separation unit comprises a centrifugal machine, an inlet of the centrifugal machine is communicated with the biogas production unit to obtain the biogas fermentation residue generated by the biogas production unit, and the centrifugal machine is provided with an outlet for outputting biogas residue and biogas liquid.

[0031] The application further provides a kitchen waste resource recycling method, comprising:

[0032] S1, pulp preparation and separation of kitchen waste, impurities are removed and uniform slurry is obtained;

[0033] S2, organic acid directional fermentation and purification of the uniform slurry obtained in step S1 are performed to obtain organic acid and organic acid fermentation residue, and the obtained organic acid is stored;

[0034] S3, biogas fermentation is performed on the organic acid fermentation residue obtained in step S2 to obtain biogas and biogas fermentation residue;

[0035] S4, cooling separation is performed on the biogas obtained in step S3 to obtain heavy impurities, methane and carbon dioxide, the heavy impurities are discharged for combustion or used as reducing gas for the organic acid directional fermentation process in step S2, and the methane and the carbon dioxide are respectively stored;

[0036] S5, separation is performed on the biogas fermentation residue obtained in step S3 to obtain biogas residue and biogas liquid, which are then sent out for treatment.

[0037] The kitchen waste resource recycling system and method provided by the application efficiently extract organic matter in kitchen waste, fully degrade various organic matters in kitchen waste by using different types of microorganisms, produce industrial raw materials such as lactic acid and caproic acid, produce clean energy such as biological natural gas and liquid food-grade carbon dioxide, realize deep high-value resourceization of kitchen waste, and realize maximum resource recycling and utilization. BRIEF DESCRIPTION OF DRAWINGS

[0038] In order to more clearly illustrate the technical solutions in the application or prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description are some embodiments of the application, and other drawings can be obtained by those skilled in the art without creative labor.

[0039] Figure 1is a schematic diagram of a kitchen waste resource recycling system provided by the present application;

[0040] Figure 2 is a working process schematic diagram of an organic acid purification device provided by the present application.

[0041] Reference signs:

[0042] 1, organic matter extraction unit; 10, pulper; 11, sieve plate; 12, impurity slagging port; 13, pulp discharging port; 2, organic acid production unit; 20, organic acid fermentation tank; 21, oxidation-reduction control device; 22, organic acid purification device; 23, organic acid storage tank; 3, biogas production unit; 30, anaerobic fermentation tank; 4, methane carbon dioxide separation unit; 40, first cooler; 41, first separation column; 42, second cooler; 43, second separation column; 44, flare; 45, carbon dioxide storage tank; 46, biogas storage tank; 47, water storage tank; 48, vacuum pump; 49, compressor; 5, biogas residue and biogas liquid separation unit; 50, centrifuge; 6, solid-liquid separation device; 7, membrane separation system; 70, ultrafiltration membrane; 71, nanofiltration membrane; 72, reverse osmosis membrane. DETAILED DESCRIPTION

[0043] In order to make the objects, technical solutions and advantages of the present application clearer, the technical solutions in the present application will be described clearly and completely below with reference to the drawings in the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work belong to the protection scope of the present application.

[0044] In the description of the embodiments of the present application, it should be noted that the orientations or positional relationships indicated by the terms "center", "longitudinal", "transverse", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer" and the like are based on the orientations or positional relationships shown in the drawings, and are only for the convenience of describing the embodiments of the present application and simplifying the description, and therefore cannot be understood as indicating or implying that the devices or elements indicated thereby must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the embodiments of the present application. In addition, the terms "first", "second", "third" are only for the purpose of description, and cannot be understood as indicating or implying relative importance.

[0045] In the description of the embodiments of the present application, it should be noted that unless specifically defined and limited, the terms "connected", "connected" should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or it can be integrally connected; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium. For those skilled in the art, the specific meaning of the above terms in the embodiments of the present application can be understood according to the specific circumstances.

[0046] In the embodiments of the present application, unless specifically defined and limited, the first feature is "on" or "under" the second feature. The first and second features can be in direct contact, or the first and second features can be in indirect contact through an intermediate medium. Moreover, the first feature "above", "above" and "above" the second feature can be the first feature directly above or obliquely above the second feature, or it can only mean that the first feature is higher than the second feature in horizontal height. The first feature "below", "below" and "below" the second feature can be the first feature directly below or obliquely below the second feature, or it can only mean that the first feature is lower than the second feature in horizontal height.

[0047] In the description of the present application, the description of the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In the present application, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in the present application and the features of different embodiments or examples without contradiction.

[0048] The following will be described in conjunction with Figure 1 and Figure 2 The kitchen waste resource recycling system and method of the present application are described.

[0049] One specific embodiment of the present application provides a kitchen waste resource recycling method, as shown in Figure 1 The method comprises the following steps:

[0050] S1, the kitchen waste is pulped and separated, the impurities are removed and the uniform slurry is obtained. The kitchen waste is made into uniform slurry in the pulper 10 (hydrocyclone pulper), the impurities and slurry are separated by the sieve plate 11, the impurities are discharged from the impurity discharge port 12, and the slurry is discharged from the slurry discharge port 13 into the organic acid production unit 2;

[0051] S2, the uniform slurry obtained in step S1 enters the organic acid fermentation tank 20, the oxidation-reduction control device 21 is used to adjust the ORP value (oxidation-reduction potential value) of the fermentation system in the organic acid fermentation tank 20, so that the directional fermentation of different organic acids (such as lactic acid and hexanoic acid) is realized, the fermentation liquid rich in a large amount of organic acid enters the organic acid purification device 22, the product after purification enters the organic acid storage tank 23, and the residual enters the biogas production unit 3;

[0052] S3, the residual of the organic acid fermentation in step S2 is subjected to biogas fermentation in the anaerobic fermentation tank 30, the biogas produced by the anaerobic fermentation tank 30 enters the methane-carbon dioxide separation unit 4, and the fermentation residual enters the biogas residue-biogas liquid separation unit 5;

[0053] S4, the biogas obtained in step S3 enters the compressor 49, is then subjected to preliminary cooling through the first cooler 40, and the heavy impurities are separated in the first separation tower 41, the impurities contain hydrogen sulfide and hydrocarbons, are mostly combustible, enter the flare 44 for combustion, a bypass is reserved and connected with the oxidation-reduction control device 21, so that the oxidation-reduction control device 21 is provided with a reducing gas.

[0054] S5, the biogas fermentation residual obtained in step S3 is subjected to solid-liquid separation of the anaerobic fermentation residual into biogas residue and biogas liquid through the centrifugal machine 50, and is then externally sent for treatment.

[0055] The kitchen waste resource recycling method of the embodiment can efficiently extract organic matter in the kitchen waste, fully degrade various organic matters in the kitchen waste by using different types of microorganisms, produce industrial raw materials such as lactic acid and hexanoic acid, produce clean energy such as biogas and liquid food-grade carbon dioxide, realize deep and high-value resourceization of the kitchen waste, and realize maximum resource recycling. The kitchen waste resource recycling process fully utilizes the organic matter in the kitchen waste, obtains industrial raw materials (organic acids), biogas (methane content of more than 97%) and food-grade liquid carbon dioxide, and realizes efficient conversion of the kitchen waste and high-value and diversification of the conversion products.

[0056] The kitchen waste resource recycling system provided by the application is described below, and the kitchen waste resource recycling system described below can be correspondingly referred to the kitchen waste resource recycling method described above.

[0057] Another embodiment of the application provides a kitchen waste resource recycling system suitable for the kitchen waste resource recycling method described above, which is described again with reference to Figure 1As shown, the system includes an organic matter extraction unit 1, an organic acid production unit 2, a biogas production unit 3, a methane-carbon dioxide separation unit 4, and a biogas residue-biogas liquid separation unit 5. The organic matter extraction unit 1 is used for slurry separation of kitchen waste to obtain slurry and impurities; the organic acid production unit 2 is connected to the organic matter extraction unit 1 and used for receiving the slurry prepared by the organic matter extraction unit 1 and performing organic acid directional fermentation and purification to obtain organic acid; the biogas production unit 3 is connected to the organic acid production unit 2 and used for receiving the organic acid fermentation residue generated by the organic acid production unit 2 and performing biogas fermentation; the methane-carbon dioxide separation unit 4 is connected to the biogas production unit 3 and used for receiving the biogas produced by the biogas production unit 3 and performing cooling separation to obtain methane and carbon dioxide; and the biogas residue-biogas liquid separation unit 5 is connected to the biogas production unit 3 and used for receiving the biogas fermentation residue generated by the biogas production unit 3 and performing solid-liquid separation before being discharged for treatment.

[0058] The organic matter extraction unit 1, the organic acid production unit 2, the biogas production unit 3, the methane-carbon dioxide separation unit 4, and the biogas residue-biogas liquid separation unit 5 will be described in detail below.

[0059] In one embodiment, the organic matter extraction unit 1 includes a slurry maker 10, and a sieve plate 11 is detachably arranged at the outlet of the slurry maker 10 to form an impurity discharge port 12 above the sieve plate 11 and a slurry discharge port 13 below the sieve plate 11.

[0060] It can be understood that the kitchen waste is made into uniform slurry in the slurry maker 10 (a hydrocyclone slurry maker), and the impurities and the slurry are separated by the sieve plate 11, the impurities are discharged from the impurity discharge port 12, and the slurry is discharged from the slurry discharge port 13 into the organic acid fermentation tank 20. Among them, the sieve plate 11 with a suitable pore size can be selected according to the properties of the waste to achieve the maximum impurity removal rate and the highest organic matter extraction rate, and the impurities are discharged from the impurity discharge port 12 and finally sent out for treatment together with the solid-phase biogas residue separated by the centrifugal machine 50 in the biogas residue-biogas liquid separation unit 5.

[0061] In another embodiment, the organic acid production unit 2 includes an organic acid fermentation tank 20, an oxidation-reduction control device 21, an organic acid purification device 22, and an organic acid storage tank 23. The organic acid fermentation tank 20 is used for receiving the slurry prepared by the organic matter extraction unit 1 and performing organic acid fermentation; the oxidation-reduction control device 21 is installed in the organic acid fermentation tank 20 and used for controlling the oxidation-reduction potential value in the organic acid fermentation tank 20; the organic acid purification device 22 is connected to the organic acid fermentation tank 20, and the organic acid purification device 22 is provided with an organic acid outlet and an organic acid fermentation residue outlet; and the organic acid storage tank 23 is connected to the organic acid outlet of the organic acid purification device 22.

[0062] It can be understood that the uniform slurry obtained through the pulper 10 enters the organic acid fermentation tank 20, the redox regulating device 21 adjusts the ORP value (oxidation-reduction potential value) of the fermentation system in the organic acid fermentation tank 20, realizes the directional fermentation of different organic acids (such as lactic acid and hexanoic acid), the fermentation liquor rich in a large amount of organic acid enters the organic acid purification device 22, the purified product enters the organic acid storage tank 23, and the residue enters the biogas production unit 3.

[0063] Specifically, in some embodiments, the redox regulating device 21 comprises an oxidation-reduction potential online analyzer, an oxidizing gas supply end and a reducing gas supply end, so as to monitor the oxidation-reduction potential value in the organic acid fermentation tank 20 through the oxidation-reduction potential online analyzer, and control the oxidizing gas supply end or the reducing gas supply end to ventilate the organic acid fermentation tank 20.

[0064] The redox regulating device 21 can micro-ventilate the oxidizing gas (air) and the reducing gas (hydrogen sulfide) into the organic acid fermentation tank 20, so as to change the oxidation-reduction potential of the system. The organic slurry made of kitchen waste enters the organic acid fermentation tank 20 to produce acid, and research shows that the optimal ORP value of the acid-producing microorganisms of organic acids such as acetic acid, lactic acid and hexanoic acid is different (this example takes lactic acid as an example). The lactic acid bacteria can become the dominant species by adjusting the ORP value of the fermentation system. In this embodiment, the ORP value is adjusted by the redox regulating device 21, and the oxidation-reduction potential online analyzer is installed on the organic acid fermentation tank 20 to monitor the ORP value of the fermentation system. According to the ORP value, the oxidizing gas (air) or the reducing gas (hydrogen sulfide) is automatically ventilated into the organic acid fermentation tank 20 by the oxidizing gas supply end or the reducing gas supply end, so as to ensure that the fermentation system maintains the required ORP value for lactic acid fermentation. The ORP value is maintained at a certain level, and the directional fermentation of organic acids is realized.

[0065] In the existing acid production technology, the electric fermentation technology is generally used to promote acid production, but a large part of electric energy is consumed, and the electrodes in the fermentation tank also need to be maintained. In this embodiment, the ORP of the system is adjusted to promote acid production, and the oxidizing gas (air) and the reducing gas (hydrogen sulfide separated from the produced biogas) are ventilated into the system to adjust the ORP, which greatly reduces the cost.

[0066] In other embodiments, see Figure 2As shown, the organic acid purification device 22 comprises the solid-liquid separation device 6 and the membrane separation system 7, the membrane separation system 7 comprises a main separation pipeline and a plurality of bypass pipelines, the main separation pipeline is sequentially connected with the ultrafiltration membrane 70, the nanofiltration membrane 71 and the reverse osmosis membrane 72, and the ultrafiltration membrane 70, the nanofiltration membrane 71 and the reverse osmosis membrane 72 are respectively connected with the bypass pipelines in parallel on the main separation pipeline; the solid-liquid separation device 6 is connected with the organic acid fermentation tank 20, the liquid phase outlet of the solid-liquid separation device 6 is communicated with the main separation pipeline, and the main separation pipeline is communicated with the organic acid storage tank 23; the separation residual liquid outlets of the ultrafiltration membrane 70, the nanofiltration membrane 71 and the reverse osmosis membrane 72 are mixedly communicated with the solid phase outlet of the solid-liquid separation device 6 to form the organic acid fermentation residue outlet.

[0067] It can be understood that the organic acid fermentation mode is continuous fermentation, the discharge contains a large amount of organic acid, and the discharge enters the organic acid purification device 22 for purification, firstly passes through the solid-liquid separation device 6 for solid-liquid separation, the separated solid phase enters the biogas production unit 3, and the separated liquid phase enters the membrane separation system 7, which is described again with reference to Figure 2 , the membrane separation system 7 uses the ultrafiltration membrane 70, the nanofiltration membrane 71 and the reverse osmosis membrane 72 in series, and has bypass pipelines which can bypass any one membrane, through the opening and closing of each valve in the pipeline, flexible combination of the three membranes can be realized according to the product quality requirement, and finally separated organic acid enters the organic acid storage tank 23 for storage, the residual liquid separated by the ultrafiltration membrane 70, the nanofiltration membrane 71 and the reverse osmosis membrane 72 can enter the anaerobic fermentation tank 30 of the biogas production unit 3 together with the solid phase separated by the solid-liquid separation device 6 through the pipeline.

[0068] The main use of organic acid is sugar in the material, and there are still a large amount of fat, protein and residual sugar in the material. In order to improve the resource utilization rate of garbage, the residue of organic acid fermentation can continue to be subjected to anaerobic fermentation. In an embodiment, the biogas production unit 3 comprises an anaerobic fermentation tank 30, the anaerobic fermentation tank 30 is provided with an organic acid fermentation residue inlet, a biogas outlet and a biogas fermentation residue outlet, the anaerobic fermentation tank 30 is communicated with the organic acid production unit 2 through the organic acid fermentation residue inlet, and is used for receiving the organic acid fermentation residue generated by the organic acid production unit 2; the anaerobic fermentation tank 30 is communicated with the methane carbon dioxide separation unit 4 through the biogas outlet; and the anaerobic fermentation tank 30 is communicated with the biogas residue and liquid separation unit 5 through the biogas fermentation residue outlet.

[0069] The residue of organic acid fermentation is subjected to biogas fermentation in the anaerobic fermentation tank 30, the biogas produced by the anaerobic fermentation tank 30 enters the methane carbon dioxide separation unit 4, and the fermentation residue enters the biogas residue and liquid separation unit 5. It can be understood that the residue of existing organic acid fermentation is generally used as a carbon source for sewage treatment, and the resource utilization level is very low. In the embodiment, the residue of organic acid fermentation is used as a substrate for anaerobic fermentation, and the organic matter of the kitchen waste is further utilized, so that the overall resource utilization rate is greatly improved.

[0070] In some embodiments, the methane-carbon dioxide separation unit 4 comprises a first cooler 40, a first separation tower 41, a second cooler 42 and a second separation tower 43 connected in sequence; the first cooler 40 is connected to the biogas production unit 3 to receive the biogas produced by the biogas production unit 3; the first separation tower 41 is provided with a heavy impurity outlet connected to a flare 44 by a pipeline and connected to the redox control device 21 of the organic acid production unit 2 by another pipeline; the second separation tower 43 is connected to a carbon dioxide storage tank 45 and a biogas storage tank 46.

[0071] The biogas obtained by the biogas production unit 3 is preliminarily cooled by the first cooler 40 and the heavy impurities, including hydrogen sulfide and hydrocarbons, are separated out in the first separation tower 41. The heavy impurities are mostly combustible materials and are burned in the flare 44. A bypass is reserved to connect the first separation tower 41 to the redox control device 21. The hydrogen sulfide and other gases separated out by the first separation tower 41 provide reducing gas for the redox control device 21. After the biogas passes through the first separation tower 41, it is deeply cooled by the second cooler 42 and then high-precision separation of methane and carbon dioxide is achieved in the second separation tower 43. The carbon dioxide is stored in the carbon dioxide storage tank 45 in liquid form and the methane is stored in the biogas storage tank 46 in gaseous form.

[0072] In other embodiments, the methane-carbon dioxide separation unit 4 further comprises a water storage tank 47, a vacuum pump 48 and a compressor 49. The vacuum pump 48 is connected to the water storage tank 47. The outlet of the cooling system of the first cooler 40 and the outlet of the cooling system of the second cooler 42 are respectively connected to the inlet of the vacuum pump 48. The inlet of the cooling system of the first cooler 40 and the inlet of the cooling system of the second cooler 42 are respectively connected to the outlet of the vacuum pump 48. The compressor 49 is connected in series to the pipeline connecting the biogas production unit 3 to the first cooler 40.

[0073] In these embodiments, the first cooler 40 and the second cooler 42 use the water vaporization absorption heat method under vacuum to cool down the gas and make it liquefy. The second separation tower 43 directly produces liquid food-grade carbon dioxide and high-pressure biogas, without the need for further liquefaction or pressurization of the products.

[0074] Specifically, the biogas obtained by the biogas production unit 3 is first introduced into the compressor 49 to be pressurized to 2.4 MPa and then introduced into the first cooler 40 to be preliminarily cooled, so that the impurities with relatively large molecular weight in the biogas are condensed into liquid state (at this time, the impurities removed mainly include hydrogen sulfide and some large-molecular hydrocarbon gases), and the gas-liquid mixture is introduced into the first separation column 41 to be separated, and the impurities in liquid state flow out of the bottom of the column, and the impurities are basically combustible materials, a part of which is introduced into the flare 44 to be combusted, and the other part is introduced into the redox control device 21 to provide reducing gas. The mixed gas of methane, carbon dioxide and a small amount of air flows out of the top of the first separation column 41, and then is introduced into the second cooler 42 to be deeply cooled, so that the carbon dioxide is condensed into liquid state, and the gas-liquid mixture is introduced into the second separation column 43 to be separated, and the liquid carbon dioxide flows out of the bottom of the column, and the bio-natural gas flows out of the top of the column and is introduced into the carbon dioxide storage tank 45 and the bio-natural gas storage tank 46 respectively to be stored.

[0075] Under the pressure of 2.4 MPa, the boiling point of carbon dioxide is -12℃, and in this embodiment, the water vaporization under vacuum is used for cooling, and when the pressure is lower than 200 pa, the vaporization temperature of water is lower than -12℃, and a suitable vacuum pump 48 is used to reduce the pressure of the water refrigeration system to make the water vaporize and cool, and the water storage tank 47 is arranged to make the water circulate in the refrigeration system. The pressure of the second separation column 43 is about 2.4 MPa, and high-pressure bio-natural gas product and food-grade liquid carbon dioxide product can be directly obtained,

[0076] In this embodiment, the biogas is used to produce two products, i.e. food-grade liquid carbon dioxide and bio-natural gas, and the purity of the food-grade carbon dioxide can be as high as 99.9%. It can be understood that in the existing low-temperature rectification technology for purifying carbon dioxide from biogas, liquid ammonia or the like is generally used as refrigerant to produce cooling capacity by phase change, but liquid ammonia or the like needs certain cost and has certain pollution as chemical agent, and in this embodiment, the phase change of water under negative pressure is used to produce cooling capacity as the cold source for low-temperature rectification, and the raw material cost is low and there is no pollution.

[0077] The biogas residue separation unit 5 includes a centrifuge 50, the inlet of the centrifuge 50 is connected to the biogas production unit 3 to obtain the biogas fermentation residue produced by the biogas production unit 3, and the centrifuge 50 is provided with outlets for outputting biogas residue and biogas liquid.

[0078] The organic acid fermentation residue is introduced into the anaerobic fermentation tank 30 to be anaerobically fermented, and the biogas fermentation residue is introduced into the centrifuge 50 to be separated into solid phase and liquid phase, the solid phase is jointly transported out of the system together with the impurities produced during pulping, and the liquid phase is sent to a sewage plant for treatment.

[0079] It should be pointed out finally that the above embodiments are only used to illustrate the technical solutions of the present application, but not to limit the same; and although the present application has been described in detail with reference to the foregoing embodiments, it should be appreciated by those skilled in the art that the technical solutions recorded in the foregoing embodiments can be modified, or some technical features thereof can be replaced equivalently; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A kitchen waste recycling system, characterized in that, include: Organic matter extraction unit (1) is used to pulp and separate kitchen waste to obtain pulp and impurities; The organic acid production unit (2) includes an organic acid fermentation tank (20), a redox control device (21), an organic acid purification device (22), and an organic acid storage tank (23). The organic acid fermentation tank (20) is connected to the organic matter extraction unit (1) and is used to receive the slurry prepared by the organic matter extraction unit (1) and to carry out organic acid fermentation. The redox control device (21) is installed in the organic acid fermentation tank (20) and includes an online redox potential analyzer, an oxidizing gas supply end, and a reducing gas supply end. The online redox potential analyzer is used to monitor the redox potential value in the organic acid fermentation tank (20) and control the oxidizing gas supply end or the reducing gas supply end to ventilate the organic acid fermentation tank (20). The organic acid storage tank (23) includes a solid-liquid separation device (6) and a membrane separation system (7). The membrane separation system (7) includes a main separation pipeline and multiple bypass pipelines. An ultrafiltration membrane (70), a nanofiltration membrane (71), and a reverse osmosis membrane (72) are connected in series on the main separation pipeline. The bypass pipelines are connected in parallel to the ultrafiltration membrane (70), the nanofiltration membrane (71), and the reverse osmosis membrane (72) on the main separation pipeline. The solid-liquid separation device (6) is connected to the organic acid fermentation tank (20). The liquid phase outlet of the solid-liquid separation device (6) is connected to the main separation pipeline. The main separation pipeline is connected to the organic acid storage tank (23). The separation residue outlets of the ultrafiltration membrane (70), the nanofiltration membrane (71), and the reverse osmosis membrane (72) are mixed and connected with the solid phase outlet of the solid-liquid separation device (6) to form an organic acid fermentation residue outlet. The organic acid storage tank (23) is connected to the organic acid outlet of the organic acid purification device (22). The biogas production unit (3) is connected to the organic acid production unit (2) and is used to receive the organic acid fermentation residue produced by the organic acid production unit (2) and carry out biogas fermentation. The methane carbon dioxide separation unit (4) comprises a first cooler (40), a first separation tower (41), a second cooler (42) and a second separation tower (43) connected in sequence, the first cooler (40) is connected with the biogas production unit (3) to receive the biogas produced by the biogas production unit (3); the first separation tower (41) is provided with a heavy impurity outlet, the heavy impurity outlet is connected with a flare (44) through a pipeline and connected with the redox control device (21) through another pipeline; the second separation tower (43) is connected with a carbon dioxide storage tank (45) and a biogas storage tank (46); the methane carbon dioxide separation unit (4) further comprises a water storage tank (47), a vacuum pump (48) and a compressor (49); the vacuum pump (48) is connected with the water storage tank (47), the outlet of the cooling system of the first cooler (40) and the outlet of the cooling system of the second cooler (42) are respectively connected with the inlet of the vacuum pump (48), and the inlet of the cooling system of the first cooler (40) and the inlet of the cooling system of the second cooler (42) are respectively connected with the outlet of the vacuum pump (48); the compressor (49) is connected in series on the pipeline connecting the first cooler (40) with the biogas production unit (3); The biogas residue and liquid separation unit (5) is connected with the biogas production unit (3) to receive the biogas fermentation residues produced by the biogas production unit (3) and to discharge after solid-liquid separation.

2. The kitchen waste recycling system according to claim 1, characterized in that, The organic matter extraction unit (1) comprises a pulper (10), and a sieve plate (11) is detachably arranged at the outlet of the pulper (10) to form an impurity residue outlet (12) above the sieve plate (11) and a pulp discharge port (13) below the sieve plate (11).

3. The kitchen waste recycling system according to claim 1, characterized in that, The biogas production unit (3) comprises an anaerobic fermentation tank (30), the anaerobic fermentation tank (30) is provided with an organic acid fermentation residue inlet, a biogas outlet and a biogas fermentation residue outlet, the anaerobic fermentation tank (30) is connected with the organic acid production unit (2) through the organic acid fermentation residue inlet to receive the organic acid fermentation residues produced by the organic acid production unit (2); the anaerobic fermentation tank (30) is connected with the methane carbon dioxide separation unit (4) through the biogas outlet; the anaerobic fermentation tank (30) is connected with the biogas residue and liquid separation unit (5) through the biogas fermentation residue outlet.

4. The kitchen waste recycling system according to claim 1, characterized in that, The biogas residue and liquid separation unit (5) comprises a centrifugal machine (50), the inlet of the centrifugal machine (50) is connected with the biogas production unit (3) to obtain the biogas fermentation residues produced by the biogas production unit (3), and the centrifugal machine (50) is provided with an outlet for outputting biogas residue and biogas liquid.

5. A kitchen waste resource recycling method, which is suitable for the kitchen waste resource recycling system according to any one of claims 1-4, characterized in that, Comprise: S1, pulping and separating the kitchen waste to remove impurities and obtain uniform slurry; S2, the uniform slurry obtained in step S1 is subjected to organic acid directional fermentation and purification to obtain organic acid and organic acid fermentation residues, and the obtained organic acid is stored; S3, carrying out biogas fermentation on the organic acid fermentation residue obtained in step S2 to obtain biogas and biogas fermentation residue; S4, carrying out cooling separation on the biogas obtained in step S3 to obtain heavy impurities, methane and carbon dioxide, discharging the heavy impurities for combustion or using the heavy impurities as the organic acid directed fermentation process in step S2, and respectively storing the methane and the carbon dioxide; S5, carrying out separation on the biogas fermentation residue obtained in step S3 to obtain biogas residue and biogas liquid, and then externally sending the biogas residue and the biogas liquid for treatment.

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