A method for recovering and processing by-products of edible vegetable oil processing

Abstract

The present application belongs to the technical field of waste oil recycling, and particularly relates to a method for recycling and processing by-products of edible vegetable oil processing, comprising the following steps: S1, mixing raw materials with deionized water and potassium permanganate, wherein the raw materials comprise soapstock, oil foot and deodorized distillate; S2, performing gradient separation treatment on the mixed liquid obtained in step S1, wherein the gradient separation treatment comprises centrifugal separation, mixed solvent extraction and ultrasonic-assisted separation; and S3, recycling oil and fat products and solid products obtained in step S2. The present application realizes the collaborative treatment of multiple types of by-products, the comprehensive recovery rate of oil and fat reaches more than 85%, the energy consumption is reduced by 35%, the use of strong acid and strong base is avoided, it is green and environmentally friendly, the operation is simple, and it is suitable for industrial application.

Description

Technical Field

[0001] This invention belongs to the field of waste oil recycling technology, specifically relating to a method for recycling and processing by-products from edible vegetable oil processing. Background Technology

[0002] Traditional refining processes for edible vegetable oils use crude oil as raw material, involving a series of steps including degumming, deacidification, decolorization, deodorization, and dewaxing. While purifying the oil, these processes generate numerous byproducts: the degumming process produces oil residue containing phospholipids, proteins, and metal ions; alkali refining and deacidification produce soap residue containing saponified compounds and neutral oils; the decolorization process produces waste bleaching clay that has absorbed pigments and impurities; and the deodorization process produces deodorized distillates containing free fatty acids, tocopherols, and sterols. These byproducts, as waste oil, typically contain free fatty acids, neutral oils, glycerol, phospholipids, and pigments, and thus have high comprehensive utilization value.

[0003] Currently, the recycling and processing of by-products from edible vegetable oil processing mainly faces the following technical challenges: (1) Traditional acidification processes cause serious environmental pollution. Existing soap residue treatments mostly use high-concentration sulfuric acid acidification processes, which generate a large amount of high-COD acidic wastewater. The wastewater is difficult to treat and improper treatment can easily cause environmental pollution. At the same time, the extraction rate of acidified oil is less than 30%, and the remaining oil is discharged with the wastewater or treated as low-value waste, resulting in a waste of resources.

[0004] (2) The treatment of decolorized waste bleaching clay is energy-intensive and has a low residual oil recovery rate. Existing waste bleaching clay treatment technologies usually use solvent leaching to recover residual oil, which requires a large amount of organic solvent and has high energy consumption for solvent recovery; although pressing does not require solvent, the residual oil rate is still as high as 6% to 8%, and the oil recovery is incomplete.

[0005] (3) The deodorized distillate extraction process is complex and has poor selectivity. Existing technologies mostly use molecular distillation, saponification reaction and other methods to extract high value-added components such as vitamin E and phytosterols from deodorized distillates, but the process is long, the equipment investment is large, and it is difficult to achieve the separation selectivity of different components.

[0006] (4) The processing of various by-products is scattered and lacks coordination. Existing technologies usually design independent processing schemes for a single type of by-product, without considering the possibility of coordinated processing between different by-products, resulting in low overall resource utilization.

[0007] (5) Secondary pollution problems caused by strong base and strong acid systems. In the existing technology, strong bases (such as sodium hydroxide) and strong acids (such as concentrated sulfuric acid) are commonly used, which not only cause serious corrosion to equipment, but also generate a large amount of acid and base waste liquid that needs further treatment.

[0008] Based on the above-mentioned technical problems, this invention proposes a novel method for recycling and processing by-products from edible vegetable oil processing. Summary of the Invention

[0009] To address the aforementioned problems in the existing technology, the present invention provides a method for recycling and processing by-products from edible vegetable oil processing, comprising the following steps: S1. Mix the raw materials with deionized water and potassium permanganate. The raw materials include soap residue, oil residue and deodorized distillate. S2. The mixture obtained in step S1 is subjected to gradient separation treatment, which includes centrifugation, mixed solvent extraction and ultrasonic-assisted separation. S3. Recycle the oil and solid products obtained in step S2.

[0010] Preferably, in step S1, the amount of potassium permanganate added is 0.5-1.0% of the mass of the mixed raw materials.

[0011] Preferably, in step S1, the mixing mass ratio of soap residue, oil residue and deodorized distillate is (2~4):(1~2):(0.5~1).

[0012] Preferably, in step S2, the gradient separation process includes the following sub-steps: S21. Centrifugal separation: The mixed liquid is centrifuged at a speed of 3000~5000 rpm for a time of 10~30 min to obtain an upper clear liquid and a lower solid residue. S22. Mixed solvent extraction: Heat the supernatant obtained in step S21 to 50℃~70℃, add a mixed solvent of paraffin oil and toluene, stir and let stand to separate the layers, and collect the organic phase; S23. Ultrasonic-assisted separation: The lower solid residue obtained in step S21 is mixed with waste decolorizing white clay, water is added to adjust the moisture content, and then ultrasonic treatment is performed to further release the oil in the solid residue. S24. Post-processing: The organic phase obtained in step S22 and the slurry obtained in step S23 are subjected to further processing.

[0013] Preferably, in step S22, the volume ratio of paraffin oil to toluene is (1~3):1.

[0014] Preferably, in step S23, the mass ratio of the lower solid residue to the waste bleaching clay is 1:(0.5~1.5); water is added to adjust the moisture content to 40%~60%.

[0015] Preferably, in step S23, the conditions for ultrasonic treatment are: ultrasonic frequency 20~40kHz; ultrasonic treatment time 15~45min.

[0016] Preferably, in step S24, the post-processing specifically includes the following steps: solvent evaporation and recovery of the organic phase to obtain a mixed fatty acid product; pressure filtration separation of the slurry to recover the oil in the filtrate; and drying of the filter cake for use as an organic fertilizer substrate or soil conditioner raw material.

[0017] The beneficial effects of this invention are: (1) Significantly improved comprehensive recovery rate of by-products. This invention incorporates by-products such as soap residue, oil residue, deodorized distillate, and waste bleaching clay into a unified co-processing flow, avoiding the losses caused by the dispersed recovery of various by-products in traditional segmented processing. In particular, after selective oxidation treatment of by-products with potassium permanganate, unsaturated components are moderately oxidized (while the structure of saturated fatty acids is not destroyed), the molecular structure changes, and the hydrophilicity is enhanced. This makes it easier to separate from saturated fatty acids and other components in subsequent centrifugation and solvent extraction processes, thus improving the efficiency of subsequent separation. Experimental data show that using the method of this invention, the comprehensive recovery rate based on oil equivalent can reach more than 85%, and some preferred schemes can reach more than 89%, which is about 20 percentage points higher than the existing segmented processing schemes (usually with a comprehensive recovery rate between 65% and 70%).

[0018] (2) Avoid using strong acids and alkalis to reduce equipment corrosion and operational risks. Current soap residue treatment commonly uses concentrated sulfuric acid (98%) for acidification, causing severe corrosion to equipment such as reactors, pipelines, and pumps, typically reducing equipment lifespan to only 2-3 years. Furthermore, the storage and use of concentrated sulfuric acid pose significant safety hazards. This invention uses potassium permanganate as an oxidant to replace strong acids. Potassium permanganate is a solid powder, safe to use, easy to store, and its oxidation reaction conditions are mild (40℃~80℃, normal pressure), producing no highly corrosive intermediate products. In addition, this invention does not use strong alkalis such as sodium hydroxide throughout the entire process, avoiding the treatment problems of traditional alkali refining waste liquid.

[0019] (3) Reduce organic solvent usage and volatilization loss. Existing methods for recovering residual oil from waste decolorizing bleaching clay often employ solvent oil leaching (No. 6 solvent), with a solvent-to-clay mass ratio typically of (2-4):1. This solvent recovery process is energy-intensive, and solvent volatilization causes a decline in air quality in the working environment. This invention employs a physical separation method of "ultrasonic assistance + pressure filtration" in the treatment of waste decolorizing bleaching clay. Only a small amount of water is added to adjust the moisture content when mixing the lower layer solid residue with the bleaching clay, eliminating the need for large amounts of organic solvent. Only a mixed solvent of paraffin oil and toluene is used during the mixed solvent extraction (upper clear liquid treatment) process. The addition of paraffin oil reduces the volatility of toluene, resulting in approximately 70% less solvent usage compared to traditional solvent leaching methods. The solvent loss rate after evaporation and recovery is less than 2%.

[0020] (4) Reduced overall energy consumption. In existing technologies, the extraction of vitamin E and phytosterols from deodorized distillates typically requires multi-stage molecular distillation, which involves high operating temperatures (150℃~200℃) and high vacuum requirements (0.1~10Pa), resulting in enormous energy consumption. This invention co-processes the deodorized distillate with soapstock, oilstock, and rough edge oil, eliminating the pursuit of high-purity component extraction and instead focusing on obtaining mixed fatty acids. This significantly reduces the separation precision requirements, thereby avoiding the energy-intensive molecular distillation step. Furthermore, ultrasonic-assisted separation is performed at room temperature or low temperature, eliminating the need for heating. Overall, the energy consumption per unit of by-product processed in this invention is approximately 35% lower than that of existing mainstream technologies.

[0021] (5) High-value utilization of by-products. The solid filter cake (mainly composed of decolorized clay, cellulose substances, and a small amount of residual organic matter) generated during the treatment process can be dried and used as an organic fertilizer substrate or soil conditioner raw material, realizing the resource utilization of solid waste and avoiding the environmental problems caused by traditional landfill or incineration. At the same time, the recovered mixed fatty acid products can be further used to prepare industrial raw materials such as biodiesel, soap, and surfactants, which has good economic benefits.

[0022] (6) The process is simple to operate and the equipment investment is low. The process of this invention uses conventional equipment such as reaction kettles, centrifuges, ultrasonic equipment, and filter presses. It does not require expensive special equipment such as molecular distillation towers and supercritical extraction devices. The equipment investment is reduced by about 50% compared with the existing high-end recovery routes. At the same time, the operating conditions are mild (atmospheric pressure, medium and low temperature, weak oxidation system), and the technical requirements for operators are low, making it easy to promote and implement in edible oil processing enterprises. Detailed Implementation

[0023] The present invention will now be clearly described with reference to specific embodiments. These descriptions are merely illustrative and are not intended to limit the scope of the invention. Any modifications, equivalent substitutions, or improvements made by those skilled in the art based on the embodiments of the present invention without inventive effort to obtain all other embodiments should be included within the scope of protection of the present invention.

[0024] Example 1 150 kg of soap residue, 75 kg of oil residue, and 40 kg of deodorized distillate, all byproducts of edible oil processing, were added to a reaction vessel along with 20 kg of deionized water and 1.5 kg of potassium permanganate. The mixture was stirred until homogeneous. The mixture was centrifuged at 4000 rpm for 20 min, and the supernatant was collected. 100 L of a 2:1 mixture of paraffin oil and toluene was added to the supernatant, and the mixture was stirred at 50 °C for 30 min. After standing and separating the layers, the organic phase was collected. The lower solid residue obtained from centrifugation was mixed with 80 kg of waste bleaching clay, and water was added to adjust the moisture content to 50%. The mixture was treated with ultrasound at 30 kHz for 30 min, followed by pressure filtration. After solvent evaporation and recovery, 86 kg of mixed fatty acids were obtained from the organic phase. 12 kg of oil was recovered from the filtrate. 85 kg of organic fertilizer matrix was obtained after drying the filter cake. The overall recovery rate was 87.3%.

[0025] Example 2 The difference between this embodiment and Example 1 is as follows: 180 kg of soap residue, 90 kg of oil residue, and 45 kg of deodorized distillate were added to 25 kg of deionized water and 2.0 kg of potassium permanganate, and mixed thoroughly. The mixture was then centrifuged at 3500 rpm for 25 min; the volume ratio of paraffin oil to toluene was 2.5:1; and the ultrasonic treatment frequency was 35 kHz for 25 min. 92 kg of mixed fatty acids, 14 kg of recovered oil, and 90 kg of organic fertilizer substrate were obtained; the overall recovery rate was 89.1%.

[0026] In summary, it can be seen that the various process steps in this invention have significant synergistic effects, and there are unexpected synergistic effects among the three core steps of potassium permanganate oxidation, mixed solvent extraction, and ultrasound-assisted separation: First, after oxidation treatment with potassium permanganate, the polarity of the by-product changes, making it easier to be extracted by the paraffin oil-toluene system in subsequent mixed solvent extraction, with the extraction rate increasing by about 25% compared to the unoxidized treatment. Secondly, the manganese oxide particles produced by the oxidation treatment act as a filter aid during the centrifugal separation process, reducing the moisture content of the solid residue, which is beneficial for subsequent ultrasonic treatment. Furthermore, ultrasonic treatment not only releases the oils adsorbed in the bleached clay, but also further decomposes the trace amounts of potassium permanganate remaining in the solid, reducing the COD of the solid filter cake and improving its quality as an organic fertilizer substrate.

[0027] The embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A method for recycling and processing by-products from edible vegetable oil processing, characterized in that: Includes the following steps: S1. Mix the raw materials with deionized water and potassium permanganate. The raw materials include soap residue, oil residue and deodorized distillate. S2. The mixture obtained in step S1 is subjected to gradient separation treatment, which includes centrifugation, mixed solvent extraction and ultrasonic-assisted separation. S3. Recycle the oil and solid products obtained in step S2.

2. The method for recycling and treating by-products from edible vegetable oil processing according to claim 1, characterized in that: In step S1, the amount of potassium permanganate added is 0.5-1.0% of the mass of the mixed raw materials.

3. The method for recycling and treating by-products from edible vegetable oil processing according to claim 1, characterized in that: In step S1, the mass ratio of soap residue, oil residue and deodorized distillate is (2~4):(1~2):(0.5~1).

4. The method for recycling and treating by-products from edible vegetable oil processing according to claim 1, characterized in that: In step S2, the gradient separation process includes the following sub-steps: S21. Centrifugal separation: The mixed liquid is centrifuged at a speed of 3000~5000 rpm for a time of 10~30 min to obtain an upper clear liquid and a lower solid residue. S22. Mixed solvent extraction: Heat the supernatant obtained in step S21 to 50℃~70℃, add a mixed solvent of paraffin oil and toluene, stir and let stand to separate the layers, and collect the organic phase; S23. Ultrasonic-assisted separation: The lower solid residue obtained in step S21 is mixed with waste decolorizing white clay, water is added to adjust the moisture content, and then ultrasonic treatment is performed to further release the oil in the solid residue. S24. Post-processing: The organic phase obtained in step S22 and the slurry obtained in step S23 are subjected to further processing.

5. The method for recycling and treating by-products from edible vegetable oil processing according to claim 4, characterized in that: In step S22, the volume ratio of paraffin oil to toluene is (1~3):

1.

6. The method for recycling and treating by-products from edible vegetable oil processing according to claim 4, characterized in that: In step S23, the mass ratio of the lower solid residue to the waste bleaching clay is 1:(0.5~1.5); water is added to adjust the moisture content to 40%~60%.

7. The method for recycling and treating by-products from edible vegetable oil processing according to claim 4, characterized in that: In step S23, the conditions for ultrasonic treatment are: ultrasonic frequency 20~40kHz; ultrasonic treatment time 15~45min.

8. The method for recycling and treating by-products from edible vegetable oil processing according to claim 4, characterized in that: In step S24, the post-processing specifically includes the following steps: solvent evaporation and recovery of the organic phase to obtain a mixed fatty acid product; pressure filtration separation of the slurry to recover the oil in the filtrate; and drying of the filter cake for use as an organic fertilizer substrate or soil conditioner raw material.