Efficient separation method of kitchen materials

Abstract

The application discloses a kind of high-efficiency separation methods of kitchen material, after kitchen material is ground into pulp, by selecting different boiling range and mutually soluble extractant, two-stage extraction is carried out at suitable temperature, and combined separation process can efficiently separate out grease, lipid organic matter, starch cellulose organic matter, sewage phase and large particle impurities etc. in kitchen waste, wherein the highest recovery rate of grease extraction can reach 97%, extractant is recycled, and the energy consumption of separation extractant is low, and cost is controllable, the method has the beneficial effects of small footprint, easy operation, environment-friendly, safe and reliable, high grease recovery rate, high quality of recovered grease etc.

Description

Technical Field

[0001] This invention relates to a method for efficient separation of food waste materials, and more particularly to a method that can simultaneously and efficiently separate components such as oil, lipid organic matter, starch and cellulose organic matter, wastewater phase, and large particulate impurities from food waste materials, belonging to the field of food waste treatment. Background Technology

[0002] Food waste generated in modern catering and home kitchens is rich in organic matter such as grease, lipids, starch, cellulose, and protein, as well as a large amount of water and solid impurities. The treatment of this waste presents enormous potential for resource utilization, such as extracting biofuels or converting it into animal feed and industrial raw materials. However, current food waste treatment technologies are insufficient in terms of efficiency and separation effectiveness, typically only separating the material into grease, wastewater, and solid residue. These methods, including but not limited to sedimentation, membrane separation, centrifugation, extrusion, and filtration, struggle to simultaneously achieve low-cost and high-efficiency separation, especially when faced with highly mixed organic matter and impurities.

[0003] The difficulties encountered in existing technologies are mainly twofold:

[0004] (1) There is a large density difference between oil, sewage and solid sludge, so they can be separated relatively easily by centrifugation, sedimentation and other methods. However, the density difference between solid components such as lipid organic matter, starch and cellulose organic matter and large particulate impurities is small and they stick together to each other, making it difficult to achieve fine separation.

[0005] (2) The mixture of grease, wastewater and solid residue makes it impossible to achieve efficient separation, resulting in resource waste and increased difficulty and cost of subsequent treatment and disposal. For example, the emulsification and dispersal of oil droplets, the coagulation and adhesion of animal fats, the suspension and surface adsorption of solid particles often lead to the entanglement of grease, water and solids, resulting in resource loss and increased operation and maintenance costs.

[0006] In summary, existing separation methods in the food waste treatment industry (such as sedimentation, coarse granulation, filtration, membrane separation, centrifugation, flotation, and adsorption) cannot quickly and cost-effectively separate organic matter such as grease, lipids, starch, and cellulose, as well as moisture and impurities from food waste. On the one hand, this results in resource waste due to the inefficient utilization of organic resources such as grease, starch, and lipids. On the other hand, residual grease and impurities in the material adversely affect subsequent wastewater and solid waste treatment systems. For example, grease in food wastewater inhibits the activity of anaerobic and aerobic bacteria, increasing wastewater treatment costs; impurities in food wastewater not only cause equipment wear but also accumulate at the bottom of equipment, making them difficult to clean, reducing the effective volume of the equipment, and lowering processing capacity.

[0007] Although extraction methods have demonstrated advantages in separating oils, such as lower energy consumption, faster extraction speed, and higher oil recovery rates, and because extractants are inexpensive and recyclable, their application in the efficient separation of kitchen waste into five components has not yet been reported. Existing extraction technologies exhibit a trade-off between energy consumption and extraction efficiency when dealing with the high oil content of kitchen waste. High oil extraction rates are often accompanied by high energy consumption, and the material temperature is directly proportional to oil extraction efficiency, necessitating the use of high-boiling-point extractants to avoid excessive evaporation. This, in turn, increases the energy consumption and cost of subsequent extractant recovery. These factors make it difficult for existing processes to be widely applied to the deep oil extraction of kitchen waste, highlighting the urgent need for innovative technologies that are both environmentally friendly and economical to meet this demand. Summary of the Invention

[0008] To address the shortcomings of existing methods for separating kitchen waste materials, the present invention aims to provide a highly efficient method for separating kitchen waste materials. This method utilizes two-stage extraction, combining the boiling range characteristics of the extractant with the temperature of the extracted material, and employing centrifugation and other methods to efficiently separate kitchen waste materials into five phases: oil, lipid organic matter, starch and cellulose organic matter, wastewater, and large particulate impurities. This not only solves the problem of impurities easily accumulating at the bottom of kitchen wastewater treatment equipment but also achieves excellent oil extraction rates with relatively low extraction energy consumption.

[0009] To achieve the above technical objectives, the present invention provides a method for efficient separation of kitchen waste materials, the method comprising the following steps:

[0010] S1. After grinding and pulping the kitchen materials, adjust the temperature to T1 and add extractant A1 for extraction and separation. The separation results in five parts: high-temperature extraction phase, lipid organic phase, starch and cellulose organic phase, sewage phase and large particulate impurities.

[0011] S2. Evaporate the high-temperature extractive phase at temperature T2 to obtain oil and extractant A1. Reuse extractant A1 in step S1.

[0012] S3. After adjusting the temperature of the wastewater phase to T3, add extractant A2 for extraction treatment to separate the low-temperature extract phase and the low-temperature raffinate phase.

[0013] S4. Evaporate the low-temperature extract phase at temperature T4, condense to obtain extractant A2 and reuse it in step S3. Then evaporate the low-temperature extract phase at temperature T2, condense to obtain extractant A1 and reuse it in step S1. The raffinate phase is oil.

[0014] S5. The low-temperature raffinate obtained in step S3 is separated into five parts: extract, lipid organic matter, raffinate, starch and cellulose organic matter, and large particulate impurities. The extract is returned to step S4 and evaporated at temperature T4 to separate lipid organic matter, starch and cellulose organic matter, and large particulate impurities. The raffinate is evaporated at temperature T4 and condensed to obtain extractant A2, which is then reused in step S3 for extraction.

[0015] T1 is 50–100°C, T2 is the final distillation temperature of extractant A1, T3 is 25–50°C, and T4 is the final distillation temperature of extractant A2. Extractant A1 is at least one of petroleum ether, diethyl ether, n-hexane, ethyl acetate, and carbon tetrachloride with a boiling range of 60–90°C; extractant A2 is petroleum ether and / or acetone with a boiling range of 30–60°C.

[0016] This invention utilizes miscible extractants with different boiling ranges to perform a two-stage extraction combined with separation processes such as centrifugation, ultrasound, or high-frequency vibration. This method efficiently separates oils, lipid-based organic matter, starch-cellulose-based organic matter, wastewater phase, and large particulate impurities from kitchen waste, achieving an oil recovery rate of up to 97%. Furthermore, the extractants in this invention are reusable, and the two-stage separation method effectively solves the technical problem that higher oil extraction rates lead to higher energy consumption for the separation extractants.

[0017] The key to this invention lies in using a "high-temperature extraction + low-temperature extraction" process to resolve the contradiction between oil extraction rate and energy consumption. The principle is as follows: First, a small amount of extractant A1 is thoroughly mixed with high-temperature kitchen materials at temperature T1. Under high-temperature conditions, the oil in the kitchen materials is easily extracted, has low viscosity, and high solubility in the extractant, facilitating the transfer of oil from the kitchen materials to extractant A1, reducing the difficulty of oil extraction and separation, and increasing the oil extraction rate. This maximizes the transfer of oil from the kitchen materials to extractant A1. Then, the material temperature is lowered, utilizing the difference in solubility of oil in extractant A1 and extractant A2 at low temperatures. Extractant A2 displaces the oil-containing extractant A1, and the miscibility of extractant A2 with extractant A1 further facilitates the displacement of extractant A1, while simultaneously reducing the amount of extractant A2 used. Since the oil in the kitchen materials has been largely transferred to extractant A1 during the high-temperature extraction stage, the oil is easily extracted even when the wastewater temperature is lowered.

[0018] The inventors discovered that the advantages of using a "high-temperature extraction + low-temperature extraction" process compared to using either "high-temperature extraction" or "low-temperature extraction" alone are: it retains the advantage of high-temperature extraction in increasing oil extraction rate while combining the advantage of low-temperature extraction in reducing the energy consumption of extractant separation. Furthermore, the types of extractants selected in this invention can achieve both excellent oil extraction rates and low energy consumption.

[0019] As a preferred embodiment, the temperature range of T2-T1 is 10–40℃, and the temperature range of T4-T3 is 10–30℃. The temperature differences between T2-T1 and T4-T3 in this invention directly affect the extraction effect and energy consumption. If these two temperature differences are too large, the energy consumption for extractant separation is high; conversely, if these two temperature differences are too small, the extractant is prone to volatility, which is detrimental to the normal progress of extraction.

[0020] As a preferred embodiment, the kitchen materials can be subjected to three-phase separation before being extracted with extractant A1 to separate most of the oil. Then, the separated wastewater and solid residue can be used to extract oil, which can further improve the oil extraction rate.

[0021] As a preferred embodiment, the volume ratio of the extractant A1 to the kitchen materials is (0.1-2):1.

[0022] As a preferred embodiment, the volume ratio of the extractant A2 to the wastewater phase is (1-2):1.

[0023] This invention achieves efficient oil extraction using only small amounts of extractant A1 and extractant A2, significantly reducing production costs. During the separation process, the amount of extractant A2 should be greater than or equal to the amount of extractant A1 to ensure the efficiency of extractant A2 in displacing extractant A1.

[0024] As a preferred embodiment, the extraction time in step S3 is 3 to 15 minutes.

[0025] As a preferred embodiment, the particle size of the kitchen waste material after grinding and pulping is less than 10 mm. By controlling the particle size of the kitchen waste material to be smaller, it can have more sufficient contact with the extractant, which is beneficial to improving the oil extraction rate.

[0026] As a preferred embodiment, in step S3, the extractant A2 and the wastewater phase are in a continuous countercurrent manner, that is, the extractant A2 continuously enters from one end of the low-temperature mixer, and the wastewater phase also continuously enters from the other end of the low-temperature mixer. The two flow towards each other. After the extractant A2 dissolves with the oil in the wastewater phase, the extractant phase flows out from the wastewater phase inlet end, and the raffinate phase flows out from the extractant A2 inlet end.

[0027] As a preferred embodiment, the feed flow ratio of extractant A2 to the wastewater phase is (1-6):1. By controlling the flow rates of both, it can be ensured that the extract phase and the raffinate phase rapidly separate, keeping the extract phase clear and free of impurities. More preferably, a two-stage or multi-stage series cryogenic mixer is provided, with the wastewater phase passing through each cryogenic mixer sequentially.

[0028] As a preferred embodiment, the evaporation process in steps S2 to S5 is carried out under a slight negative pressure, which can accelerate the evaporation rate of the extractant. More preferably, the evaporation process is performed using a two-stage or multi-stage high-temperature evaporator connected in series, with the extract phase passing through each evaporator sequentially to ensure complete evaporation of the extractant within the extract phase.

[0029] The present invention provides a method for efficient separation of kitchen waste materials, which specifically includes the following steps:

[0030] S1: Grinding and pulping. Grind and pulp the kitchen materials to minimize the particle size as much as possible.

[0031] S2: Adjust the temperature. Adjust the temperature of the kitchen materials to T1 (50-100℃). More preferably, the temperature should be adjusted to 60-70℃.

[0032] S3: High-temperature extraction. Select extractant A1 with a final distillation temperature higher than that of the kitchen materials in S2. Mix the two in a certain proportion in a high-temperature mixer to ensure that extractant A1 and kitchen materials are fully dissolved to form a mixture.

[0033] S4: Separation. Using methods such as centrifugation, ultrasound, or high-frequency vibration, the mixture can be separated into five parts: a high-temperature extraction phase, a lipid-based organic phase, a starch-cellulose-based organic phase, a wastewater phase, and large particulate impurities. The extraction phase is separated and evaporated at high temperature T2, separating the extractant A1 from the oil. The evaporated extractant A1 is condensed and recovered before being pumped back into the high-temperature mixer, while the oil is pumped into an oil storage tank. The lipid-based and starch-cellulose-based organic phases are separated, cleaned, and then utilized as resources. Large particulate impurities are separated, dehydrated, and transported for disposal. The wastewater phase continues with the following steps.

[0034] S5: Adjust the temperature. Adjust the temperature of the wastewater phase separated in S4 to T3 (25-50℃).

[0035] S6: Low-temperature extraction. Select extractant A2 with a final distillation temperature higher than that of the wastewater phase in S5, mix and stir it with the wastewater phase in a low-temperature mixer to fully dissolve extractant A2 and wastewater, while simultaneously causing the extract phase and raffinate phase to separate into layers.

[0036] As a preferred embodiment, the stirring speed of S6 should be controlled between 30 and 180 rpm. If it is too fast, the extractant A2 and the wastewater phase will not easily separate into layers, and if it is too slow, the extractant A2 and the wastewater phase will not be fully mixed.

[0037] S7: Evaporation and separation of the extract phase from the low-temperature extractant A2. The extract phase separated from the low-temperature mixer is heated in the low-temperature evaporator to the final distillation temperature T4 of the low-temperature extractant A2 while continuously stirring, so that the low-temperature extractant A2 is evaporated and separated by heating. The evaporated low-temperature extractant A2 is collected, condensed and recovered and then pumped back into the low-temperature mixer for recycling.

[0038] S8: Evaporation and separation of the extract phase from the high-temperature extractant A1. The extract phase from the separation of the low-temperature extractant A2 enters the high-temperature evaporator, where it is heated to the final distillation temperature T2 of the high-temperature extractant A1 while continuously stirred, causing the high-temperature extractant A1 to evaporate and separate. The evaporated extractant A1 is collected, condensed, and recycled into a high-temperature mixer. The remaining extract is the oil. After the extractant A1 has completely evaporated, the oil is transferred to a storage tank.

[0039] S9: Raffinate Separation. The raffinate separated in S6 is separated using centrifugation, ultrasound, or high-frequency vibration to separate it into five parts: extract, lipid-based organic matter, raffinate, starch and cellulose-based organic matter, and large particulate impurities. The separated extract is sent to a low-temperature evaporator. Lipid-based organic matter, starch, and cellulose-based organic matter are separated, cleaned, and then utilized as resources. Large particulate impurities are separated, dehydrated, and then transported for disposal. The raffinate portion continues with the following steps.

[0040] S10: Low-temperature evaporation and separation of extractant A2 from the raffinate. The separated raffinate is fed into a heater and heated to the final distillation temperature T4 of the low-temperature extractant A2 while continuously stirring to ensure that the extractant A2 remaining in the raffinate is fully evaporated, collected, condensed, and recovered, then pumped into a low-temperature mixer for recycling. The remaining kitchen wastewater is subjected to anaerobic digestion to produce biogas.

[0041] Compared with the prior art, the technical solution of the present invention brings the following beneficial technical effects:

[0042] 1) The method provided by this invention has advantages such as low cost and low energy consumption. It can efficiently separate five parts from kitchen waste materials: oil, lipid organic matter, starch and cellulose organic matter, sewage phase and large particulate impurities. It avoids the problem of impurities easily accumulating at the bottom of kitchen wastewater treatment equipment. In addition, it has the beneficial effects of small footprint, easy operation, environmental friendliness, safety and reliability, high oil recovery rate and high quality of recovered oil.

[0043] 2) This invention makes full use of the relationship between the boiling range characteristics of the extractant and the temperature of the extracted material, and adopts the "high temperature extraction + low temperature extraction" process to solve the technical contradiction between the oil extraction rate and the extraction energy consumption. It retains the advantages of high temperature extraction in improving the oil extraction rate, and combines the advantages of low temperature extraction in reducing the energy consumption of extractant separation.

[0044] 3) The oil, lipid organic matter and starch and cellulose organic matter separated by the efficient separation method of kitchen waste of the present invention can be recycled and reused, while large particulate impurities and wastewater phase can be harmlessly treated, thus maximizing the utilization of resources. Attached Figure Description

[0045] Figure 1 This is a process diagram of food waste separation according to Embodiment 1 of the present invention.

[0046] Figure 2 The images show the kitchen materials before and after separation in Embodiment 1 of the present invention. Detailed Implementation

[0047] The following embodiments are only specific descriptions of preferred embodiments of the present invention and are not intended to limit the scope of the present invention. For those skilled in the art, any improvements made without departing from the present invention should be considered within the scope of protection of the present invention.

[0048] Example 1

[0049] This embodiment describes a highly efficient method for separating kitchen waste materials. The kitchen waste materials used are kitchen waste materials recycled from restaurants, canteens, and home kitchens in Changsha. The specific steps of the separation method are as follows:

[0050] Step 1: First, remove large impurities such as plastic bottles, glass bottles, and plastic bags from the recycled kitchen waste. Then, grind the cleaned material into a pulp to reduce its particle size to below 10mm.

[0051] Step 2: Adjust the temperature of the slurry to 60℃.

[0052] Step 3: Add petroleum ether solvent extractant A1 with a boiling range of 60-80℃ and high-temperature slurry to a high-temperature mixer in a 1:1 volume ratio, stir vigorously to fully mix the two and form a mixture.

[0053] Step 4: The mixture is separated into five phases using centrifugation: the extract phase, the lipid-based organic phase, the starch- and cellulose-based organic phase, the wastewater phase, and large particulate impurities. Centrifugation is performed at 3500 rpm for 20 seconds. The extract phase is separated and then evaporated at 80°C to separate the extractant A1 from the oil. The evaporated extractant A1 is condensed and recovered before being pumped back into the high-temperature mixer, while the oil is pumped into an oil storage tank. The oil extraction rate in this step is 53%. The lipid-based organic phase, starch- and cellulose-based organic phases are then separated, cleaned, and used to make feed for resource utilization. Large particulate impurities are separated, dehydrated, and transported for disposal. The wastewater phase continues with the following steps.

[0054] Step 5: Adjust the temperature of the wastewater phase separated in Step 4 to 30℃.

[0055] Step 6: Select petroleum ether extractant A2 with a boiling range of 30-60℃, mix it with the wastewater phase in a low-temperature mixer and stir (stirring speed 180 rpm) to fully mix and dissolve the extractant A2 with the wastewater phase, and at the same time, separate the extract phase and the raffinate phase into layers.

[0056] The extractant A2 and wastewater phase are fed in a continuous counter-current manner. Extractant A2 enters continuously from the bottom of the cryogenic mixer and flows upwards at a velocity controlled at 1 mm / s. The wastewater phase enters continuously from the top of the cryogenic mixer and flows downwards, with a residence time of approximately 10 minutes. The volume ratio of extractant A2 to wastewater phase is maintained at 1:1, and their feed flow rates are also maintained at a 1:1 ratio. After extractant A2 and the oil in the wastewater phase dissolve to form the extractable phase, the extractable phase flows out from the top of the mixer. The wastewater phase inlet is lower than the extractable phase overflow outlet to prevent the wastewater phase from flowing out with the extractable phase. The raffinate phase is discharged from the bottom of the mixer. It is essential to ensure rapid stratification of the extractable and raffinate phases, with the extractable phase being clear and free of impurities. To improve the oil extraction recovery rate, a two-stage cryogenic extraction mixer is used. The wastewater phase first enters the first-stage cryogenic mixer, then the second-stage. This step can achieve an oil extraction rate of 90% for kitchen waste materials.

[0057] Step 7: Separate the extract phase from the low-temperature mixer into the low-temperature evaporator. Heat the extract phase to the final distillation temperature of the low-temperature extractant A2 (60°C) while continuously stirring to evaporate and separate the extractant A2. The evaporated extractant A2 is collected, condensed, and recycled back into the low-temperature mixer for reuse. Maintain a slight negative pressure inside the low-temperature evaporator to accelerate the evaporation rate of extractant A2.

[0058] Step 8: The extract phase of the low-temperature extractant A2 is separated and fed into a high-temperature evaporator. The extract phase is heated to the final distillation temperature of the high-temperature extractant A1, 80°C, and stirred continuously to allow the high-temperature extractant A1 to evaporate and separate. The evaporated extractant A1 is collected, condensed and recovered, and then fed into a high-temperature mixer for recycling.

[0059] The remaining extract is the oil. After the extractant has completely evaporated, the oil is transferred to a storage tank.

[0060] Maintain a slight negative pressure inside the high-temperature evaporator to accelerate the evaporation rate of the extractant. A two-stage high-temperature evaporator series is used, with the extract phase passing through each evaporator sequentially.

[0061] Step Nine: The raffinate phase separated in Step Six is ​​separated by centrifugation into five parts: extract, lipid-based organic matter, raffinate, starch and cellulose-based organic matter, and large particulate impurities. The centrifugation speed is 3800 rpm for 20 seconds. The separated extract is sent to a low-temperature evaporator. This step can achieve an oil extraction rate of 92% for kitchen waste. Lipid-based organic matter, starch, and cellulose-based organic matter are separated, cleaned, and then utilized as resources. Large particulate impurities are separated, dehydrated, and then transported for disposal. The raffinate portion continues with the following steps.

[0062] Step 10: The separated raffinate is fed into a heater and heated to the final distillation temperature of the low-temperature extractant A2 (60°C) while continuously stirring. This ensures that the remaining extractant A2 in the raffinate is fully evaporated, collected, condensed, and then pumped into a low-temperature mixer for recycling. The remaining kitchen wastewater undergoes anaerobic digestion to produce biogas. A slight negative pressure is maintained inside the heater to accelerate the evaporation rate of extractant A2. A two-stage series heater is installed, with the raffinate phase passing through each heater sequentially.

[0063] The separation results of processing 1 ton of food waste in this embodiment are shown in Table 1:

[0064] Table 1. Separation of food waste materials (wet weight)

[0065] Component Name grease lipid organic matter Starch, cellulose and other organic matter sewage Large particulate impurities Mass ratio (%) 6 7 16 58 13

[0066] With all core parameters unchanged, the two-stage extraction process saves 23% energy compared to using high-temperature extraction alone and 27% energy compared to using low-temperature extraction alone. This is because low-temperature extraction has low efficiency, requires a large amount of extractant, and takes a long time, thus consuming more energy than high-temperature extraction.

[0067] Example 2

[0068] This embodiment describes a highly efficient method for separating kitchen waste materials. The kitchen waste materials used are kitchen waste materials recycled from restaurants, canteens, and home kitchens in Changsha. The specific steps of the separation method are as follows:

[0069] Step 1: First, the recycled kitchen waste is pre-treated by removing impurities, pulping, heating, and three-phase separation to separate the kitchen waste into three parts: grease, sewage, and solid residue. Then, the sewage and solid residue are mixed and further ground into pulp to reduce the particle size to below 10mm.

[0070] Step 2: Adjust the temperature of the slurry to 70℃.

[0071] Step 3: Add petroleum ether solvent extractant A1 with a boiling range of 70-90℃ and high-temperature slurry to a high-temperature mixer at a volume ratio of 0.5:1, and stir vigorously to ensure that the two are fully mixed to form a mixture.

[0072] Step 4: The mixture is separated into five phases using centrifugation: the extract phase, the lipid-based organic phase, the starch- and cellulose-based organic phase, the wastewater phase, and large particulate impurities. Centrifugation is performed at 4000 rpm for 30 seconds. The extract phase is separated and then evaporated at 90°C to separate the extractant A1 from the oil. The evaporated extractant A1 is condensed and recovered before being pumped back into the high-temperature mixer, while the oil is pumped into an oil storage tank. The oil extraction rate in this step is 68%. The lipid-based organic phase, starch- and cellulose-based organic phases are then separated, cleaned, and used to make feed for resource utilization. Large particulate impurities are separated, dehydrated, and transported for disposal. The wastewater phase continues with the following steps.

[0073] Step 5: Adjust the temperature of the wastewater phase separated in Step 4 to 40℃.

[0074] Step 6: Select petroleum ether extractant A2 with a boiling range of 40-60℃, mix it with the wastewater phase in a low-temperature mixer and stir (stirring speed 180 rpm) to fully mix and dissolve the extractant A2 with the wastewater phase, and at the same time, separate the extract phase and the raffinate phase into layers.

[0075] The extractant A2 and wastewater phase are fed in a continuous counter-current manner. Extractant A2 enters continuously from the bottom of the cryogenic mixer and flows upwards at a velocity controlled at 1 mm / s. The wastewater phase enters continuously from the top of the cryogenic mixer and flows downwards, with a residence time of approximately 10 minutes. The volume ratio of extractant A2 to wastewater phase is maintained at 1:1, and their feed flow rates are also maintained at 1:1. After extractant A2 and the oil in the wastewater phase dissolve to form the extractable phase, the extractable phase flows out from the top of the mixer. The wastewater phase inlet is lower than the extractable phase overflow outlet to prevent the wastewater phase from flowing out with the extractable phase. The raffinate phase is discharged from the bottom of the mixer. It is essential to ensure rapid stratification of the extractable and raffinate phases, with the extractable phase being clear and free of impurities. To improve the oil extraction recovery rate, a two-stage cryogenic extraction mixer is used. The wastewater phase first enters the first-stage cryogenic mixer, then the second-stage. This step can achieve an oil extraction rate of 94% for kitchen waste materials.

[0076] Step 7: Separate the extract phase from the low-temperature mixer into the low-temperature evaporator. Heat the extract phase to the final distillation temperature of the low-temperature extractant A2 (60°C) while continuously stirring to evaporate and separate the extractant A2. The evaporated extractant A2 is collected, condensed, and recycled back into the low-temperature mixer for reuse. Maintain a slight negative pressure inside the low-temperature evaporator to accelerate the evaporation rate of extractant A2.

[0077] Step 8: The extract phase of the low-temperature extractant A2 is separated and fed into a high-temperature evaporator. The extract phase is heated to the final distillation temperature of the high-temperature extractant A1, 90°C, and stirred continuously to allow the high-temperature extractant A1 to evaporate and separate. The evaporated extractant A1 is collected, condensed and recovered, and then fed into a high-temperature mixer for recycling.

[0078] The remaining extract is the oil. After the extractant A1 has completely evaporated, the oil is transferred to a storage tank.

[0079] Maintain a slight negative pressure inside the high-temperature evaporator to accelerate the evaporation rate of extractant A1. Set up a two-stage high-temperature evaporator in series, with the extract phase passing through each evaporator sequentially.

[0080] Step Nine: The raffinate phase separated in Step Six is ​​separated by centrifugation into five parts: extract, lipid-based organic matter, raffinate, starch and cellulose-based organic matter, and large particulate impurities. The centrifugation speed is 3000 rpm for 20 seconds. The separated extract is sent to a low-temperature evaporator. This step can achieve an oil extraction rate of 97% for kitchen waste. Lipid-based organic matter, starch, and cellulose-based organic matter are separated, cleaned, and then utilized as resources. Large particulate impurities are separated, dehydrated, and then transported for disposal. The raffinate portion continues with the following steps.

[0081] Step 10: The separated raffinate is fed into a heater and heated to the final distillation temperature of the low-temperature extractant A2 (60°C) while continuously stirring. This ensures that the remaining extractant A2 in the raffinate is fully evaporated, collected, condensed, and then pumped into a low-temperature mixer for recycling. The remaining kitchen wastewater undergoes anaerobic digestion to produce biogas. A slight negative pressure is maintained inside the heater to accelerate the evaporation rate of extractant A2. A two-stage series heater is installed, with the raffinate phase passing through each heater sequentially.

[0082] The separation results of processing 1 ton of food waste in this embodiment are shown in Table 2:

[0083] Table 2. Separation of food waste materials (wet weight)

[0084] Component Name grease lipid organic matter Starch, cellulose and other organic matter sewage Large particulate impurities Mass ratio (%) 7 6 17 57 13

[0085] The main difference between Example 2 and Example 1 is that: (1) the kitchen materials are separated into three phases before extraction to separate most of the oil, and then the separated wastewater and solid residue are subjected to deep oil extraction using the method of the present invention; (2) the high temperature extraction temperature and the low temperature extraction temperature are both increased by 10°C, which is conducive to oil leaching.

[0086] Compared to Example 1, Example 2 has the advantages of using less extractant, achieving a higher oil extraction rate, and reducing energy consumption by 40%.

Claims

1. A method for efficient separation of kitchen waste materials, characterized in that: Includes the following steps: S1. After grinding and pulping the kitchen materials, adjust the temperature to T1 and add extractant A1 for extraction and separation. The separation results in five parts: high-temperature extraction phase, lipid organic phase, starch and cellulose organic phase, sewage phase and large particulate impurities. S2. Evaporate the high-temperature extractive phase at temperature T2 to obtain oil and extractant A1. Reuse extractant A1 in step S1. S3. After adjusting the temperature of the wastewater phase to T3, add extractant A2 for extraction treatment to separate the low-temperature extract phase and the low-temperature raffinate phase. S4. Evaporate the low-temperature extract phase at temperature T4, condense to obtain extractant A2 and reuse it in step S3. Then evaporate the low-temperature extract phase at temperature T2, condense to obtain extractant A1 and reuse it in step S1. The raffinate phase is oil. S5. The low-temperature raffinate obtained in step S3 is separated into five parts: extract, lipid organic matter, raffinate, starch and cellulose organic matter, and large particulate impurities. The extract is returned to step S4 and evaporated at temperature T4 to separate lipid organic matter, starch and cellulose organic matter, and large particulate impurities. The raffinate is evaporated at temperature T4 and condensed to obtain extractant A2, which is then reused in step S3 for extraction. T1 is 50-100℃, T2 is the final distillation temperature of extractant A1, T3 is 25-50℃, and T4 is the final distillation temperature of extractant A2. The extractant A1 is at least one of petroleum ether, diethyl ether, n-hexane, ethyl acetate and carbon tetrachloride with a boiling range of 60~90℃. The extractant A2 is petroleum ether and / or acetone with a boiling range of 30~60℃; The range of T2-T1 is 10~40℃; The temperature range of T4-T3 is 10–30℃; In step S3, the extractant A2 and the wastewater phase are continuously countercurrent.

2. The efficient separation method for kitchen waste materials according to claim 1, characterized in that: The volume ratio of the extractant A1 to the kitchen materials is (0.1~2):

1.

3. The efficient separation method for kitchen waste materials according to claim 2, characterized in that: The volume ratio of the extractant A2 to the wastewater phase is (1~2):

1.

4. The efficient separation method for kitchen waste materials according to claim 3, characterized in that: The particle size of the kitchen materials after grinding and pulping is less than 10mm.

5. The efficient separation method for kitchen waste materials according to claim 4, characterized in that: The feed flow rate ratio of extractant A2 to wastewater phase is (1~6):1.

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