Method for treating waste oil from kitchen grease traps

Abstract

The application provides a treatment method for waste oil of a kitchen grease trap. The treatment method comprises the following steps: S1, first stirring and mixing waste oil of a kitchen grease trap with hydrogen peroxide to obtain a first slurry; S2, after second stirring and mixing of the first slurry with a solution containing Fe 2+ , Fenton reaction is performed to obtain a second slurry; S3, the second slurry is sequentially subjected to standing and solid-liquid separation to obtain a separated liquid and a separated residue; S4, after blending of the separated liquid with a kitchen waste slurry, anaerobic fermentation is performed; the stirring rate of the first stirring and mixing is 25000-40000 r / min. The separated liquid obtained by the treatment method has no secondary pollution or inhibition effect on a downstream anaerobic fermentation system, is simple and easy to implement, green and environmentally friendly, low in cost, high in applicability, and effectively realizes resource utilization of waste oil by anaerobic fermentation; the treatment method is not only suitable for waste oil of a kitchen grease trap, but also suitable for treatment of any high-oil fermentation substrate.

Description

Technical Field

[0001] This invention relates to the field of waste grease from kitchen grease traps, and more specifically, to a method for treating waste grease from kitchen grease traps. Background Technology

[0002] Grease traps are specialized pretreatment devices that separate grease and debris from water in canteen wastewater. They primarily collect various types of grease and food residue, most of which are high-molecular-weight fatty acids that are not easily biodegradable. Entering the environmental system poses a significant environmental pollution risk to water, air, and soil. Although waste grease from grease traps presents a potential environmental pollution risk, it is also an organic waste rich in organic carbon sources and can be recycled as a renewable resource. This is a primary way to prevent or solve the aforementioned problems.

[0003] In recent years, anaerobic fermentation technology has effectively converted organic waste into valuable resources such as volatile fatty acids, methane, and hydrogen. It boasts advantages such as simple operation, environmental friendliness, and high efficiency, and has garnered significant attention for the resource utilization of organic waste, particularly in the area of ​​food waste recycling. However, numerous studies have shown that waste oils not only easily form viscous aggregates with other substances, affecting the flowability of the fermentation broth, but also that large amounts of long-chain fatty acids severely damage the microbial community in the anaerobic fermentation system, thereby inhibiting its normal operation and hindering the resource utilization of the fermentation substrate. Therefore, food waste and other oily fermentation substrates cannot be directly introduced into the anaerobic fermentation system; certain pretreatment measures are necessary to mitigate their impact.

[0004] In actual anaerobic fermentation processes, centrifugation, flotation, and cooking are commonly used to pre-separate oils from the fermentation substrate. While this ensures the normal operation of the anaerobic fermentation system, it does not fundamentally solve the problems of oil removal and resource utilization. This not only wastes organic resources but also poses environmental pollution and food safety risks due to the separated oils. Some researchers have attempted to use physical, chemical, and biological pretreatment methods to reduce the impact of oils in the anaerobic fermentation substrate on the fermentation system. While these methods have some effect, they mainly target small amounts of waste oil in the fermentation substrate, typically less than 5% of the total substrate content. Therefore, for high-concentration waste oils in grease traps, it is essential to pre-degrade the chemical properties of the waste oils, reducing their viscosity, increasing their solubility and biodegradability, in order to achieve resource utilization of waste oils from grease traps through anaerobic fermentation.

[0005] Waste oil from grease traps is mainly composed of inert long-chain fatty acids with stable chemical structures that are not easily broken. Previous studies have mostly used pyrolysis combined with strong alkalis to modify its properties. This method typically operates at temperatures around 200℃, resulting in high energy consumption, operational difficulties, and limited treatment effectiveness. In recent years, some researchers have proposed using microorganisms with oil-degrading capabilities to modify its chemical properties. This method is highly efficient and environmentally friendly, but it requires solving the problems of screening, cultivating, and acclimatizing dominant strains, leading to high initial investment costs, high levels of expertise required, and limited applicability. Furthermore, related research is still in its early exploratory stages, and no mature and stable strains have been found to effectively degrade waste oil from grease traps. Therefore, to address the shortcomings of existing technologies, it is urgent to develop methods for regulating and treating waste oil from grease traps to enhance its resource utilization through anaerobic fermentation. Summary of the Invention

[0006] The main objective of this invention is to provide a method for treating waste grease from kitchen grease traps, thereby solving the problem of the difficulty in degrading waste grease from kitchen grease traps in the prior art.

[0007] To achieve the above objectives, according to one aspect of the present invention, a method for treating waste grease from a kitchen grease trap is provided, the method comprising the following steps: Step S1, mixing the waste grease from the kitchen grease trap with hydrogen peroxide to obtain a first slurry; Step S2, mixing the first slurry with Fe... 2+ After the solution is stirred and mixed for the second time, a Fenton reaction is carried out to obtain a second slurry; in step S3, the second slurry is allowed to stand and then separated into solid and liquid to obtain a separated liquid and a separated residue; and in step S4, the separated liquid is mixed with the kitchen waste slurry and then subjected to anaerobic fermentation; the stirring and mixing rate of the first time is 25,000 to 40,000 r / min.

[0008] Furthermore, in step S1 above, the solid content of the waste oil in the kitchen grease trap is 20-60 wt%, preferably the solid content of the waste oil in the kitchen grease trap and the mass concentration of hydrogen peroxide satisfy the following relationship: mass concentration of hydrogen peroxide = 0.1 × solid content of waste oil in the kitchen grease trap.

[0009] Furthermore, the mixing time for the first stirring step is 3 to 5 minutes.

[0010] Furthermore, in step S2 above, Fe is contained 2+ In solution, Fe 2+ Calculated, containing Fe 2+ The molar ratio of the solution to hydrogen peroxide is 1:200-280, preferably containing Fe. 2+ The solution is selected from any one or more of ferrous sulfate and ferrous chloride.

[0011] Further, in step S2 above, the second stirring and mixing includes high-speed stirring followed by low-speed stirring. Preferably, the high-speed stirring speed is 3000-4000 r / min, and the high-speed stirring time is 1-3 min. Preferably, the low-speed stirring speed is 100-250 r / min, and the low-speed stirring time is 20-50 min.

[0012] Furthermore, the temperature for the Fenton reaction described above is 90–95°C.

[0013] Furthermore, the above processing method also includes: subjecting the mixture obtained from the first stirring and mixing to a third stirring and mixing to obtain a first slurry; preferably, the temperature of the third stirring is 40-60°C, preferably the speed of the third stirring and mixing is 50-100 r / min, and preferably the time of the third stirring and mixing is 10-30 min.

[0014] Furthermore, in step S3 above, the settling time is 6 to 10 hours.

[0015] Furthermore, in step S3 above, the solid-liquid separation is filtration, preferably using a sieve with a pore size of 38 to 100 μm.

[0016] Furthermore, the volume ratio of the separated liquid to the kitchen waste slurry is 1:1 to 9.

[0017] Applying the technical solution of this application, the first stirring rate of this invention ensures that hydrogen peroxide can fully dissolve into the waste oil molecules in the kitchen grease trap, providing a guarantee for the strong oxidation of the waste oil molecular chains. Fe acts as a reaction catalyst. 2+ When hydrogen peroxide approaches the interior of waste oil molecules, it instantaneously triggers a higher-order oxidative Fenton reaction, generating a large number of hydroxyl radicals. These radicals further attack and destroy the oil molecular chains, oxidizing them into soluble small molecules and weakening the adhesion between oil molecules. This enhances the fluidity of the waste oil, ensuring mass transfer for anaerobic microorganisms and stable operation of the anaerobic system. Simultaneously, the synergistic effect of coagulation and oxidation in the Fenton reaction promotes the complexation and bridging of iron with insoluble substances, ultimately forming large aggregates that are separated and removed along with the iron. This ensures that the resulting liquid does not cause secondary pollution or inhibition to the downstream anaerobic fermentation system. This treatment method is simple, environmentally friendly, low-cost, and highly applicable, effectively realizing the resource utilization of waste oil through anaerobic fermentation. It is suitable not only for waste oil from grease traps but also for the treatment of any high-oil-content fermentation substrate. Detailed Implementation

[0018] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the embodiments.

[0019] As analyzed in the background section of this application, the waste grease in the prior art of kitchen grease traps is difficult to degrade. In order to solve this problem, this application provides a method for treating waste grease in kitchen grease traps.

[0020] In a typical embodiment of this application, a method for treating waste grease from a kitchen grease trap is provided. The method includes the following steps: Step S1, mixing the waste grease from the kitchen grease trap with hydrogen peroxide to obtain a first slurry; Step S2, mixing the first slurry with Fe... 2+ After the solution is stirred and mixed for the second time, a Fenton reaction is carried out to obtain a second slurry; in step S3, the second slurry is allowed to stand and then separated into solid and liquid to obtain a separated liquid and a separated residue; and in step S4, the separated liquid is mixed with the kitchen waste slurry and then subjected to anaerobic fermentation; the stirring and mixing rate of the first time is 25,000 to 40,000 r / min.

[0021] The first stirring rate of this invention ensures that hydrogen peroxide can fully dissolve into the waste oil molecules in the kitchen grease trap, providing a guarantee for the strong oxidation of the waste oil molecular chains. Fe acts as a reaction catalyst. 2+ When hydrogen peroxide approaches the interior of waste oil molecules, it instantaneously triggers a higher-order oxidative Fenton reaction, generating a large number of hydroxyl radicals. These radicals further attack and destroy the oil molecular chains, oxidizing them into soluble small molecules and weakening the adhesion between oil molecules. This enhances the fluidity of the waste oil, ensuring mass transfer for anaerobic microorganisms and stable operation of the anaerobic system. Simultaneously, the synergistic effect of coagulation and oxidation in the Fenton reaction promotes the complexation and bridging of iron with insoluble substances, ultimately forming large aggregates that are separated and removed along with the iron. This ensures that the resulting liquid does not cause secondary pollution or inhibition to the downstream anaerobic fermentation system. This treatment method is simple, environmentally friendly, low-cost, and highly applicable, effectively realizing the resource utilization of waste oil through anaerobic fermentation. It is suitable not only for waste oil from grease traps but also for the treatment of any high-oil-content fermentation substrate.

[0022] In one embodiment of this application, in step S1 above, the solid content of the waste oil in the kitchen grease trap is 20-60 wt%. Preferably, the solid content of the waste oil in the kitchen grease trap and the mass concentration of hydrogen peroxide satisfy the following relationship: mass concentration of hydrogen peroxide = 0.1 × solid content of waste oil in the kitchen grease trap.

[0023] Too high a concentration of hydrogen peroxide can affect the activity of anaerobic fermentation microorganisms and waste resources. Too low a concentration of hydrogen peroxide cannot trigger a strong instantaneous oxidation effect, thus failing to destroy the inert fatty acid chains in the waste oil from the kitchen grease trap. Optimizing the relationship between the solid content of the waste oil from the kitchen grease trap and the concentration of hydrogen peroxide helps to maximize the conversion of inert long-chain fatty acids into small-molecule organic matter and weaken the adhesion strength between oil molecules.

[0024] To ensure that hydrogen peroxide can penetrate the waste oil aggregates and enter the oil molecules, in some embodiments of this application, the first stirring and mixing time is preferably 3 to 5 minutes.

[0025] In one embodiment of this application, in step S2 above, Fe is included. 2+ In solution, Fe 2+ Calculated, containing Fe 2+ The molar ratio of the solution to hydrogen peroxide is 1:200-280, preferably containing Fe. 2+ The solution is selected from any one or more of ferrous sulfate and ferrous chloride.

[0026] During the Fenton reaction, a large number of hydroxyl radicals are instantaneously generated. These hydroxyl radicals react with inert fatty acids in the waste grease from the kitchen grease trap, oxidizing them into low-molecular-weight compounds, Fe. 2+ As a catalyst in the reaction, hydrogen peroxide can accelerate the rate at which hydroxyl radicals are generated. Simultaneously, to ensure the Fenton reaction occurs within the waste oil molecules, it is preferable to perform the initial stirring and mixing at a high stirring speed to allow hydrogen peroxide to enter the oil molecules. However, during the initial stirring and mixing process, under the external force of high-speed stirring, some hydrogen peroxide easily decomposes into water and oxygen. Therefore, to ensure a sufficient supply of hydroxyl radicals in the reaction, it is preferable to add an excess of hydrogen peroxide, preferably Fe. 2+ The molar concentration ratio of the solution to hydrogen peroxide is within the above-mentioned range; further, the above-mentioned Fe... 2+ The variety of solutions enriches Fe 2+ Selectivity of solutions.

[0027] In one embodiment of this application, in step S2 above, the second stirring and mixing includes first stirring at high speed and then stirring at low speed. Preferably, the speed of high-speed stirring is 3000-4000 r / min, and the time of high-speed stirring is 1-3 min. Preferably, the speed of low-speed stirring is 100-250 r / min, and the time of low-speed stirring is 20-50 min.

[0028] High-speed stirring first helps maintain good dispersion of waste oil in the first slurry, while also increasing Fe... 2+ The mass transfer and diffusion rate in the first slurry, which in turn promotes Fe 2+Similarly, it penetrates the fat molecules and rapidly comes into contact with hydrogen peroxide. Subsequently, under low-speed stirring, the hydrogen peroxide reacts with Fe... 2+ Contact triggers the Fenton reaction, which instantaneously generates a large number of hydroxyl radicals within the oil molecules, thereby destroying the molecular structure of waste oils and altering their physicochemical properties.

[0029] In one embodiment of this application, the temperature of the Fenton reaction is 90–95°C.

[0030] Based on heat transfer and fluid dynamics mechanisms, the optimal temperature range for the Fenton reaction is within the aforementioned range, which helps to control the reaction temperature of hydrogen peroxide and Fe. 2+ The study investigated the dissolution and diffusion rates inside and outside waste oil molecules, as well as the Fenton reaction rate. It also utilized endogenous acids generated during the oxidation process of organic matter to further enhance the oxidative strength of the Fenton reaction, resulting in a maximum dissolved organic carbon content of 95 g·L⁻¹ in waste oil. -1 Compared with untreated waste oil, the organic matter release rate can reach up to 529%, which fundamentally realizes the release of carbon sources and the change of performance in waste oil.

[0031] In one embodiment of this application, the above-mentioned processing method further includes: subjecting the mixture obtained by the first stirring and mixing to a third stirring and mixing to obtain a first slurry; preferably, the temperature of the third stirring is 40-60°C, preferably the speed of the third stirring and mixing is 50-100 r / min, and preferably the time of the third stirring and mixing is 10-30 min.

[0032] The third stirring, using the aforementioned preferred temperature, speed, and time, helps to promote the dissolution and diffusion of hydrogen peroxide in oil molecules.

[0033] In order to promote the rapid sedimentation of the precipitate formed by the combination of insoluble aggregates and polyvalent iron elements and their hydrates during the reaction, in one embodiment of this application, the settling time in step S3 is preferably 6 to 10 hours.

[0034] After the Fenton reaction is completed, in order to achieve sufficient solid-liquid separation between the separation liquid and the insoluble aggregates and to reduce costs, in some embodiments of this application, the solid-liquid separation is preferably performed by filtration. The filtration is preferably performed using a sieve with a pore size of 38 to 100 μm, which helps to separate the insoluble aggregates from the separation liquid as thoroughly as possible.

[0035] In one embodiment of this application, the volume ratio of the separated liquid to the kitchen waste slurry is 1:1 to 9.

[0036] The separated liquid is rich in organic matter, which can serve as an organic carbon source in the anaerobic fermentation process. The preferred volume ratio of the separated liquid to the food waste slurry is within the aforementioned range, such as 1:1, 1:2, 1:3, 1:4, 1:5, or 1:9. This ratio helps to fully utilize the organic carbon source in the separated liquid, ultimately achieving the resource utilization of waste oil from the food waste separator, while simultaneously promoting the further resource utilization of other food waste. Furthermore, to improve the dispersion uniformity and synergistic effect of the separated liquid and the food waste slurry, the solids content of the food waste slurry in this application is preferably 5-10%.

[0037] The beneficial effects of this application will be further illustrated below with reference to the embodiments.

[0038] Example 1

[0039] Taking waste oil from a kitchen waste separator in the Liuta mining area of ​​Shendong Group as an example, the sampling period was from September to October 2022:

[0040] 1) First, the solid content of the waste oil in the kitchen grease trap was determined by gravimetric method to be 29%. Based on this, the mass concentration of hydrogen peroxide to be added was determined to be 0.1 × 29% = 2.9%. Then, the waste oil in the grease trap was mixed with hydrogen peroxide and stirred at a first stirring speed of 40000 r / min for a first stirring time of 5 min to obtain a mixed slurry of waste oil and hydrogen peroxide.

[0041] 2) The mixed slurry was stirred at a constant temperature of 60℃ and a rotation speed of 100 r / min for 30 min to promote the dissolution and diffusion of hydrogen peroxide in the oil molecules; the molar concentration of hydrogen peroxide in the mixed slurry was further determined by spectrophotometry to be 0.36 mol / L, thereby determining the appropriate Fe addition. 2+ The molar concentration is 0.0018 mol / L (Fe 2+ (Molar ratio with hydrogen peroxide = 1:200);

[0042] 3) Add 0.0018 mol / L Fe to the mixed slurry. 2+ The reaction temperature was then increased to 90℃, and the mixture was first stirred at a high speed of 4000 r / min for 3 min to promote Fe production. 2+ After thorough contact with hydrogen peroxide, an advanced oxidation reaction is induced by stirring at a low speed of 250 r / min for 50 min, thereby regulating the physicochemical properties of waste oil.

[0043] 4) The above mixed slurry was left to stand at room temperature for 8 hours, and the mixed slurry after standing was filtered with a stainless steel screen with a pore size of 100μm to remove insoluble aggregates. The resulting filtrate was mixed with the kitchen waste slurry at a volume ratio of 1:4 for anaerobic fermentation to produce acid.

[0044] As shown in Table 1, compared with the untreated waste oil from the grease trap, the viscosity of the waste oil after enhanced treatment decreased by 99%; the dissolved organic carbon content decreased from 14 g·L⁻¹. -1 Increased to 88 g·L -1 The iron content in the waste oil filtrate was only 9.7 mg / L, with up to 90% of the iron being removed; the solid content was reduced to 2%, and the oil content was undetectable, achieving efficient leaching and performance control of organic matter in the waste oil of the oil separator.

[0045] Table 1

[0046]

[0047]

[0048] Example 2

[0049] Taking waste oil from a kitchen waste separator in the Liuta mining area of ​​Shendong Group as an example, the sampling period was November-December 2022:

[0050] 1) First, the solid content of the waste oil in the kitchen grease trap was determined by gravimetric method to be 49%. Based on this, the mass concentration of hydrogen peroxide to be added was determined to be 0.1 × 49% = 4.9%. Then, the waste oil in the grease trap was mixed with hydrogen peroxide and stirred at 35000 r / min for 4 min to obtain a mixed slurry of waste oil and hydrogen peroxide.

[0051] 2) The mixed slurry was stirred at a constant temperature of 50℃ and a rotation speed of 80 r / min for 20 min to promote the dissolution and diffusion of hydrogen peroxide in the oil molecules; the molar concentration of hydrogen peroxide in the mixed slurry was further determined by spectrophotometry to be 0.47 mol / L, thus determining the appropriate Fe addition. 2+ The molar concentration was 0.00188 mol / L (Fe). 2+ (Molar ratio with hydrogen peroxide = 1:250);

[0052] 3) Add 0.00188 mol / L of Fe to the mixed slurry. 2+ The reaction temperature was then increased to 92℃, and the mixture was first dispersed at 4000 r / min for 2 min to promote Fe... 2+ After being fully contacted with hydrogen peroxide, the reaction was carried out at 200 r / min for 30 min to induce an advanced oxidation reaction, thereby regulating the physicochemical properties of waste oil.

[0053] 4) The above mixed slurry was left to stand at room temperature for 10 hours, and the mixed slurry after standing was filtered with a stainless steel screen with a pore size of 38μm to remove insoluble aggregates. The resulting filtrate was mixed with the kitchen waste slurry at a volume ratio of 1:1 for anaerobic fermentation to produce acid.

[0054] As shown in Table 2, compared with the untreated waste oil from the grease trap, the viscosity of the waste oil after enhanced treatment was reduced by 99%; the dissolved organic carbon content decreased from 30 g·L⁻¹. -1 Increased to 95 g·L -1 The iron content in the waste oil filtrate was only 7.8 mg / L, with more than 90% of the iron being retained and removed. The solid content was reduced to 3%, and the oil content was undetectable, achieving efficient dissolution and performance control of organic matter in the waste oil of the oil separator.

[0055] Table 2

[0056]

[0057]

[0058] Example 3

[0059] Taking waste oil from a kitchen waste separator in the Liuta mining area of ​​Shendong Group as an example, the sampling period was from March to April 2023:

[0060] 1) First, the solid content of the waste oil in the kitchen grease trap was determined by gravimetric method to be 33%. Based on this, the mass concentration of hydrogen peroxide to be added was determined to be 0.1 × 33% = 3.3%. Then, the waste oil in the grease trap was mixed with hydrogen peroxide and stirred at 25000 r / min for 3 min to obtain a mixed slurry of waste oil and hydrogen peroxide.

[0061] 2) The mixed slurry was stirred at a constant temperature of 40℃ and a rotation speed of 50 r / min for 10 min to promote the dissolution and diffusion of hydrogen peroxide in the oil molecules; the molar concentration of hydrogen peroxide in the mixed slurry was further determined by spectrophotometry to be 0.41 mol / L, thus determining the appropriate Fe addition. 2+ The molar concentration was 0.00178 mol / L (Fe). 2+ (Molar ratio with hydrogen peroxide = 1:230);

[0062] 3) Add 0.00178 mol / L of Fe to the mixed slurry. 2+ The reaction temperature was then increased to 95℃, and the mixture was first dispersed at 3000 r / min for 1 min to promote Fe... 2+ After being fully contacted with hydrogen peroxide, the reaction was carried out at 100 r / min for 20 min to induce an advanced oxidation reaction, thereby regulating the physicochemical properties of waste oil.

[0063] 4) The above mixed slurry was left to stand at room temperature for 6 hours, and the mixed slurry after standing was filtered with a stainless steel screen with a pore size of 75μm to remove insoluble aggregates. The resulting filtrate was mixed with the kitchen waste slurry at a volume ratio of 1:2 for anaerobic fermentation to produce acid.

[0064] As shown in Table 3, compared with the untreated waste oil from the grease trap, the viscosity of the waste oil after enhanced treatment was reduced by 99%; the dissolved organic carbon content decreased from 20 g·L⁻¹. -1 Increased to 61 g·L -1 The iron content in the waste oil filtrate was only 8.8 mg / L, with more than 90% of the iron being retained and removed. The solid content was reduced to 3%, and the oil content was undetectable, achieving efficient dissolution and performance control of organic matter in the waste oil of the oil separator.

[0065] Table 3

[0066]

[0067]

[0068] Example 4

[0069] Taking the waste oil from the grease trap of a university canteen in Xi'an as an example, the sampling period was from February to March 2023:

[0070] 1) First, the solid content of the waste oil in the kitchen grease trap was determined to be 46% by gravimetric method. Based on this, the mass concentration of hydrogen peroxide to be added was determined to be 0.1 × 46% = 4.6%. Then, the waste oil in the grease trap was mixed with hydrogen peroxide and stirred at 30,000 r / min for 4 min to obtain a mixed slurry of waste oil and hydrogen peroxide.

[0071] 2) The mixed slurry was stirred at a constant temperature of 50℃ and a rotation speed of 75 r / min for 15 min to promote the dissolution and diffusion of hydrogen peroxide in the oil molecules; the molar concentration of hydrogen peroxide in the mixed slurry was further determined by spectrophotometry to be 0.48 mol / L, thus determining the appropriate dosage of Fe. 2+ The molar concentration was 0.00171 mol / L (Fe). 2+ (Molar ratio with hydrogen peroxide = 1:280);

[0072] 3) Add 0.00171 mol / L Fe to the mixed slurry. 2+ The reaction temperature was then increased to 93℃, and the mixture was first dispersed at 3500 r / min for 2 min to promote Fe... 2+ After being fully contacted with hydrogen peroxide, the reaction was carried out at 150 r / min for 35 min to induce an advanced oxidation reaction, thereby regulating the physicochemical properties of waste oil.

[0073] 4) The above mixed slurry was left to stand at room temperature for 7 hours, and the mixed slurry after standing was filtered with a stainless steel screen with a pore size of 53μm to remove insoluble aggregates. The resulting filtrate was mixed with the kitchen waste slurry at a volume ratio of 1:9 for anaerobic fermentation to produce acid.

[0074] As shown in Table 4, compared with the untreated waste oil from the grease trap, the viscosity of the waste oil after enhanced treatment was reduced by 99%; the dissolved organic carbon content decreased from 34 g·L⁻¹. -1 Increased to 74 g·L -1 The iron content in the waste oil filtrate was only 8.4 mg / L, with up to 90% of the iron being removed; the solid content was reduced to 4%, and the oil content was undetectable, achieving efficient leaching and performance control of organic matter in the waste oil of the oil separator.

[0075] Table 4

[0076]

[0077]

[0078] Example 5

[0079] Taking the waste oil from the grease trap of a university canteen in Xi'an as an example, the sampling period was from May to June 2023:

[0080] 1) First, the solid content of the waste oil in the kitchen grease trap was determined by gravimetric method to be 39%. Based on this, the mass concentration of hydrogen peroxide to be added was determined to be 0.1 × 39% = 3.9%. Then, the waste oil in the grease trap was mixed with hydrogen peroxide and stirred at 32000 r / min for 5 min to obtain a mixed slurry of waste oil and hydrogen peroxide.

[0081] 2) The mixed slurry was stirred at a constant temperature of 45℃ and a rotation speed of 60 r / min for 25 min to promote the dissolution and diffusion of hydrogen peroxide in the oil molecules; the molar concentration of hydrogen peroxide in the mixed slurry was further determined by spectrophotometry to be 0.37 mol / L, thus determining the appropriate Fe addition. 2+ The molar concentration was 0.00176 mol / L (Fe). 2+ (Molar ratio with hydrogen peroxide = 1:210);

[0082] 3) Add 0.00176 mol / L of Fe to the mixed slurry. 2+ The reaction temperature was then increased to 90℃, and the mixture was first dispersed at 4000 r / min for 1 min to promote Fe... 2+ After being fully contacted with hydrogen peroxide, the reaction was carried out at 100 r / min for 45 min to induce an advanced oxidation reaction, thereby regulating the physicochemical properties of waste oil.

[0083] 4) The above mixed slurry was left to stand at room temperature for 9 hours, and the mixed slurry after standing was filtered with a stainless steel screen with a pore size of 90μm to remove insoluble aggregates. The resulting filtrate was mixed with the kitchen waste slurry at a volume ratio of 1:3 for anaerobic fermentation to produce acid.

[0084] As shown in Table 5, compared with the untreated waste oil from the grease trap, the viscosity of the waste oil after enhanced treatment was reduced by 99%; the dissolved organic carbon content decreased from 23 g·L⁻¹. -1 Increased to 88 g·L -1 The iron content in the waste oil filtrate was only 7.3 mg / L, with up to 90% of the iron being removed; the solid content was reduced to 3%, and the oil content was undetectable, achieving efficient dissolution and performance control of organic matter in the waste oil of the oil separator.

[0085] Table 5

[0086]

[0087]

[0088] Example 6

[0089] The difference from Example 1 is that the first stirring and mixing rate is 30,000 r / min, and the final waste oil filtrate is obtained. The treatment results are shown in Table 6.

[0090] Table 6

[0091]

[0092] Example 7

[0093] The difference from Example 1 is that the first stirring and mixing rate is 25000 r / min, and the final waste oil filtrate is obtained. The treatment results are shown in Table 7.

[0094] Table 7

[0095]

[0096] Example 8

[0097] The difference from Example 1 is that the first stirring and mixing time is 3 minutes, and the waste oil filtrate is finally obtained. The treatment results are shown in Table 8.

[0098] Table 8

[0099]

[0100] Example 9

[0101] The difference from Example 1 is that Fe 2+ The molar ratio of waste oil to hydrogen peroxide was 1:240, and the final waste oil filtrate was obtained. The treatment results are shown in Table 9.

[0102] Table 9

[0103]

[0104] Example 10

[0105] The difference from Example 1 is that Fe 2+ The molar ratio of waste oil to hydrogen peroxide was 1:280, and the final waste oil filtrate was obtained. The treatment results are shown in Table 10.

[0106] Table 10

[0107]

[0108]

[0109] Example 11

[0110] The difference from Example 1 is that Fe 2+ The molar ratio of waste oil to hydrogen peroxide was 1:180, and the final waste oil filtrate was obtained. The treatment results are shown in Table 11.

[0111] Table 11

[0112]

[0113] Example 12

[0114] The difference from Example 1 is that the high-speed stirring speed is 3000 r / min and the low-speed stirring speed is 100 r / min, and the waste oil filtrate is finally obtained. The treatment results are shown in Table 12.

[0115] Table 12

[0116]

[0117]

[0118] Example 13

[0119] The difference from Example 1 is that the high-speed stirring speed is 2800 r / min and the low-speed stirring speed is 80 r / min, and the waste oil filtrate is finally obtained. The treatment results are shown in Table 13.

[0120] Table 13

[0121]

[0122] Example 14

[0123] The difference from Example 1 is that the temperature of the third stirring is 40°C, the speed of the third stirring is 50 r / min, and the time of the third stirring is 10 min. The final waste oil filtrate is obtained, and the treatment results are shown in Table 14.

[0124] Table 14

[0125]

[0126] Comparative Example 1

[0127] The difference from Example 1 is that the first stirring and mixing rate is 20,000 r / min, and the final waste oil filtrate is obtained. The treatment results are shown in Table 15.

[0128] Table 15

[0129]

[0130] As can be seen from the above examples, compared with the original grease trap waste oil, the performance of the grease trap waste oil after enhanced treatment has changed significantly. The grease is almost 100% completely removed, and the dissolved organic carbon can reach up to 95 g·L. -1 The highest increase rate reached 529%, which effectively solved the problems existing in the traditional anaerobic fermentation and resource utilization process of waste oil in grease traps. It also has the advantages of low cost, simple operation and no secondary pollution.

[0131] As can be seen from the above description, the embodiments of the present invention achieve the following technical effects:

[0132] The first stirring rate of this invention ensures that hydrogen peroxide can fully dissolve into the waste oil molecules in the kitchen grease trap, providing a guarantee for the strong oxidation of the waste oil molecular chains. Fe acts as a reaction catalyst. 2+ When hydrogen peroxide approaches the interior of waste oil molecules, it instantaneously triggers a higher-order oxidative Fenton reaction, generating a large number of hydroxyl radicals. These radicals further attack and destroy the oil molecular chains, oxidizing them into soluble small molecules and weakening the adhesion between oil molecules. This enhances the fluidity of the waste oil, ensuring mass transfer for anaerobic microorganisms and stable operation of the anaerobic system. Simultaneously, the synergistic effect of coagulation and oxidation in the Fenton reaction promotes the complexation and bridging of iron with insoluble substances, ultimately forming large aggregates that are separated and removed along with the iron. This ensures that the resulting liquid does not cause secondary pollution or inhibition to the downstream anaerobic fermentation system. This treatment method is simple, environmentally friendly, low-cost, and highly applicable, effectively realizing the resource utilization of waste oil through anaerobic fermentation. It is suitable not only for waste oil from grease traps but also for the treatment of any high-oil-content fermentation substrate.

[0133] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for treating waste grease from a kitchen grease trap, characterized in that, The processing method includes the following steps: Step S1: Mix the waste grease from the kitchen grease trap with hydrogen peroxide to obtain the first slurry. Step S2, the first slurry is mixed with Fe... 2+ After the solution is stirred and mixed a second time, a Fenton reaction is carried out to obtain a second slurry; Step S3 involves sequentially allowing the second slurry to stand and then performing solid-liquid separation to obtain a separated liquid and a separated residue; and Step S4: The separated liquid is mixed with the kitchen waste slurry and then subjected to anaerobic fermentation; The first stirring and mixing rate is 25,000~40,000 r / min; In step S1, the solid content of the waste oil in the kitchen grease trap is 20-60 wt%. The temperature for the Fenton reaction is 90~95℃.

2. The processing method according to claim 1, characterized in that, The solid content of the waste oil in the kitchen grease trap and the mass concentration of the hydrogen peroxide satisfy the following relationship: the mass concentration of the hydrogen peroxide = 0.1 × the solid content of the waste oil in the kitchen grease trap.

3. The processing method according to claim 1 or 2, characterized in that, The first stirring and mixing time is 3 to 5 minutes.

4. The processing method according to claim 1 or 2, characterized in that, In step S2, the Fe-containing 2+ In solution, Fe 2+ The Fe-containing 2+ The molar ratio of the solution to the hydrogen peroxide is 1:200~280.

5. The processing method according to claim 1 or 2, characterized in that, The Fe-containing 2+ The solution is selected from any one or more of ferrous sulfate solution and ferrous chloride solution.

6. The processing method according to claim 1 or 2, characterized in that, In step S2, the second stirring and mixing includes first high-speed stirring and then low-speed stirring.

7. The processing method according to claim 6, characterized in that, The high-speed stirring speed is 3000~4000 r / min.

8. The processing method according to claim 6, characterized in that, The high-speed stirring time is 1 to 3 minutes.

9. The processing method according to claim 6, characterized in that, The low-speed stirring speed is 100~250 r / min.

10. The processing method according to claim 6, characterized in that, The low-speed stirring time is 20-50 minutes.

11. The processing method according to claim 1 or 2, characterized in that, The processing method further includes: After the mixture obtained by the first stirring and mixing is stirred and mixed a third time, the first slurry is obtained.

12. The processing method according to claim 11, characterized in that, The temperature of the third stirring is 40~60℃.

13. The processing method according to claim 11, characterized in that, The third stirring and mixing speed is 50~100 r / min.

14. The processing method according to claim 11, characterized in that, The third mixing time is 10-30 minutes.

15. The processing method according to claim 1 or 2, characterized in that, In step S3, the settling time is 6-10 hours.

16. The processing method according to claim 1 or 2, characterized in that, In step S3, the solid-liquid separation is filtration.

17. The processing method according to claim 16, characterized in that, The filter uses a sieve with a pore size of 38~100μm.

18. The processing method according to claim 1 or 2, characterized in that, The volume ratio of the separated liquid to the kitchen waste slurry is 1:1~9.

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