A deep dewatering treatment process for oily scum

Abstract

This invention relates to a deep dewatering process for scum containing oil, comprising the following steps: alkalization treatment, ultrasonic demulsification, thermal sedimentation to achieve water-oil separation, discharge of the aqueous phase after oxidative degradation, and recovery of the oil layer after distillation of the oil phase. The scum treatment process developed in this invention can reduce the amount of oily scum through dewatering. Under the synergistic effect of ultrasound and dewatering agents, the water content of the treated sediment can be reduced to 12%, achieving high dewatering efficiency. After water-oil separation, the treated scum undergoes oxidative degradation of the aqueous phase and distillation recovery of the oil phase. The COD removal rate of the aqueous phase is high, meeting national emission standards, and the oil phase recovery rate is high, achieving resource recycling and utilization, resulting in significant economic and social benefits.

Description

Technical Field

[0001] This invention relates to the field of environmental pollution treatment agents, and more specifically, to a deep dewatering treatment process for oily scum. Background Technology

[0002] Oily sludge refers to the oily sludge produced in the flotation stage of petrochemical wastewater treatment plants. After flocculants are added, oil droplets and solid particles in the water adhere to tiny air bubbles and are carried to the surface. It is mainly composed of negatively charged hydrophilic colloidal particles, has a complex composition, is difficult to dewater, and its volume increases significantly as the quality of the crude oil deteriorates. Currently, companies typically mix the sludge with other oily sludge, add flocculants, and then mechanically separate and dewater it until the water content is reduced to about 85% before landfilling it as hazardous waste. Due to severe emulsification of the sludge, the dewatering effect of existing processes is limited, and crude oil recovery is difficult, increasing the company's hazardous waste treatment burden and wasting crude oil resources.

[0003] Methods for demulsifying scum can be broadly categorized into three types: physical, chemical, and biological. Physical methods primarily include gravity settling, centrifugation, filtration, electric field methods, microwave radiation, ultrasonic methods, and membrane demulsification. Chemical methods mainly involve adding demulsifiers. For the deep treatment of complex oily scum, relying on a single treatment method is unlikely to achieve ideal results. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention aims to utilize an oily scum dewatering agent composed of demulsifier, flocculant and surfactant, combined with ultrasonic action, to perform deep dewatering of scum.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] A deep dewatering process for scum includes the following steps:

[0007] 1. Pass the scum into the pH adjustment tank, add sodium carbonate to the tank for alkalization treatment, and adjust the pH to 7~7.5;

[0008] 2. After adjusting the pH, the scum is introduced into an ultrasonic treatment tank. A dehydrating agent is added to the tank, and the temperature is raised to 40~60℃. Demulsification is carried out under the action of the ultrasonic standing wave field.

[0009] Third, after ultrasonic treatment, the scum enters the sludge settling tank for thermal settling to achieve water-oil separation;

[0010] 4. Separate the aqueous phase and pass it into an oxidation degradation tank. Add hydrogen peroxide to the aqueous phase for oxidation degradation and then discharge it. Pass the oil phase into a distillation tank and recover the oil layer after distillation.

[0011] The oily scum dewatering agent comprises, by mass percentage:

[0012] 50-70% multi-branched demulsifier, 20-40% quaternary ammonium salt surfactant, 10% flocculant and the balance water;

[0013] The multi-branched demulsifier is first prepared by using triethylenetetramine as a reaction initiator and methyl acrylate as a monomer through Michael addition reaction and amidation reaction to obtain hyperbranched polyamide-amine; then, under alkaline conditions, propylene oxide, ethylene oxide and propylene oxide are added sequentially to polymerize and obtain a multi-branched polyether type demulsifier.

[0014] The bisquaternary ammonium salt surfactant is based on rhamnolipid as a starting material. Its terminal carboxyl group is first subjected to acylation reaction, then amidation reaction to introduce an amino group, and then it forms a bisquaternary ammonium salt with ammonium bromide.

[0015] Furthermore, the preparation process of the multi-branched demulsifier is as follows:

[0016] 1) Add a certain amount of triethylenetetramine to a reaction flask, add methanol as a solvent and stir to mix it evenly. Then, under the protection of an ice-water bath and nitrogen, slowly add an equimolar amount of methyl acrylate. After the addition is complete, heat to 35°C and stir for 48 h. Then, heat to 60, 80, 100, 120 and 140°C in stages and react for 2 h each time. Vacuum is drawn during the reaction. The resulting viscous liquid is hyperbranched polyamide-amine.

[0017] 2) Add hyperbranched polyamide-amine to the reactor, add a catalytic amount of potassium hydroxide, evacuate, heat to 120°C, and then slowly introduce propylene oxide. When the reactor pressure drops to a negative pressure and stabilizes, introduce ethylene oxide and propylene oxide into the reactor in sequence, and react at a constant temperature until the reactor pressure drops to a negative pressure and stabilizes, thus obtaining the product.

[0018] Further, in step 2), the amounts of raw materials added are as follows: 1 part hyperbranched polyamide-amine, 10 parts propylene oxide, 200 parts ethylene oxide, and 200 parts propylene oxide.

[0019] Furthermore, the preparation process of the bisquaternary ammonium salt surfactant is as follows:

[0020] S1. Add rhamnolipid and a catalytic amount of DMAP to the reaction flask, and add thionyl chloride dropwise to carry out the acyl chloride reaction. The product after the reaction is completed is dissolved in dichloromethane and placed in an ice-water bath for later use.

[0021] S2. Dissolve methyl 6-aminohexanoate hydrochloride and triethylamine in dichloromethane, and then slowly add them dropwise to step S1. After the addition is complete, heat to 30°C and continue stirring for 24 hours. Add sodium hydroxide solution, collect the organic phase, dry and filter, and use the product for later use.

[0022] S3. Dissolve the product of step S2 in dichloromethane and place it in an ice-water bath. Under nitrogen protection, slowly add 3-dimethylaminopropylamine dropwise. After the addition is complete, move the mixture to room temperature and continue stirring for 24 hours. Distill under reduced pressure to obtain a viscous liquid.

[0023] S4. Dissolve the viscous liquid from step S3 in ethanol, then add 3-bromo-propyltrimethylammonium bromide, heat to 90°C and stir for 24 hours, cool to room temperature, remove the solvent by vacuum distillation, recrystallize with a mixed solution of ethanol and acetone, and dry to obtain the final product.

[0024] Furthermore, the flocculant is cationic polyacrylamide.

[0025] Furthermore, in step two, the dosage of the dehydrating agent is 5~10 mg / L.

[0026] Furthermore, in step two, the ultrasonic conditions are: ultrasonic frequency 20~40 kHz, power 200~400 W, and ultrasonic time 5~7 min.

[0027] Compared with the prior art, the beneficial effects of the present invention are:

[0028] The scum treatment process developed in this invention can reduce the amount of oily scum through dehydration. Under the synergistic effect of ultrasound and dehydrating agent, the water content of the bottom mud after scum treatment can be reduced to 12%, with high dehydration efficiency. After water-oil separation, the treated scum undergoes oxidative degradation of the aqueous phase and distillation recovery of the oil phase. The COD removal rate of the aqueous phase is high, meeting national emission standards, and the oil phase recovery rate is high, realizing resource recycling and utilization, which has good economic and social benefits. Attached Figure Description

[0029] Figure 1 These are microscope images of scum before and after ultrasonic demulsification. a is the image before ultrasonic demulsification, and b is the image after ultrasonic demulsification.

[0030] Figure 2 Figures showing the water content of bottom sediment under different ultrasonic powers;

[0031] Figure 3 Figure showing the sediment moisture content at different treatment temperatures;

[0032] Figure 4 The graph shows the moisture content of the sediment after treatment with different dewatering agents. Detailed Implementation

[0033] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0034] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0035] Example:

[0036] This application focuses on the oily scum from the flotation section of Yangzhou Petrochemical. Through on-site sampling and analysis, the scum from this flotation section contained 97% water, 1.2% oil, had a pH of 6.4, an average volumetric particle size of 28.3 μm, and a specific surface area of ​​0.62 m². 2 / g.

[0037] The above-mentioned scum is subjected to deep dewatering, and the steps are as follows:

[0038] 1. Pass the scum into the pH adjustment tank, add sodium carbonate to the tank for alkalization treatment, and adjust the pH to 7~7.5;

[0039] 2. After adjusting the pH, the scum is introduced into an ultrasonic treatment tank. 5~10mg / L of dehydrating agent is added to the tank, and the temperature is raised to 40~60℃. Demulsification is carried out under the action of ultrasonic standing wave field. The ultrasonic frequency is 20~40 kHz, the power is 200~400 W, and the ultrasonic time is 5~7 min.

[0040] Third, after ultrasonic treatment, the scum enters the sludge settling tank for thermal settling to achieve water-oil separation;

[0041] 4. Separate the aqueous phase and pass it into an oxidation degradation tank. Add hydrogen peroxide to the aqueous phase for oxidation degradation and then discharge it. Pass the oil phase into a distillation tank and recover the oil layer after distillation.

[0042] The oily scum dewatering agent comprises, by mass percentage: 50-70% multi-branched demulsifier, 20-40% quaternary ammonium salt surfactant, and 10% flocculant.

[0043] By adjusting the mass ratio, the following dehydrating agent sample was obtained:

[0044] Sample 1: 50% multi-branched demulsifier, 30% quaternary ammonium salt surfactant, 10% flocculant and 10% water;

[0045] Sample 2: 50% multi-branched demulsifier, 20% quaternary ammonium salt surfactant, 10% flocculant and 20% water;

[0046] Sample 3: 60% multi-branched demulsifier, 20% quaternary ammonium salt surfactant, 10% flocculant and 10% water;

[0047] In the above samples, the multi-branched demulsifier is first prepared by using triethylenetetramine as a reaction initiator and methyl acrylate as a monomer through Michael addition reaction and amidation reaction to obtain hyperbranched polyamide-amine; then, under alkaline conditions, propylene oxide, ethylene oxide and propylene oxide are added sequentially to polymerize and obtain a multi-branched polyether type demulsifier.

[0048] The specific preparation process is as follows:

[0049] 1) Add a certain amount of triethylenetetramine to a reaction flask, add methanol as a solvent and stir to mix it evenly. Then, under the protection of an ice-water bath and nitrogen, slowly add an equimolar amount of methyl acrylate. After the addition is complete, heat to 35°C and stir for 48 h. Then, heat to 60, 80, 100, 120 and 140°C in stages and react for 2 h each time. Vacuum is drawn during the reaction. The resulting viscous liquid is hyperbranched polyamide-amine.

[0050] 2) Add 1 part of hyperbranched polyamide-amine to the reactor, add a catalytic amount of potassium hydroxide, evacuate, heat to 120°C, and then slowly introduce 10 parts of propylene oxide. When the reactor pressure drops to a negative pressure and stabilizes, introduce 200 parts of ethylene oxide and 200 parts of propylene oxide into the reactor in sequence, and react at a constant temperature until the reactor pressure drops to a negative pressure and stabilizes, thus obtaining the product.

[0051] In the above samples, the bisquaternary ammonium salt surfactant is based on rhamnolipid as a starting material. Its terminal carboxyl group is first subjected to acylation reaction, then amidation reaction to introduce amino groups, and then it forms a bisquaternary ammonium salt with ammonium bromide.

[0052] The specific preparation process is as follows:

[0053] S1. Add rhamnolipid and a catalytic amount of DMAP to the reaction flask, and add thionyl chloride dropwise to carry out the acyl chloride reaction. The product after the reaction is completed is dissolved in dichloromethane and placed in an ice-water bath for later use.

[0054] S2. Dissolve methyl 6-aminohexanoate hydrochloride and triethylamine in dichloromethane, and then slowly add them dropwise to step S1. After the addition is complete, heat to 30°C and continue stirring for 24 hours. Add sodium hydroxide solution, collect the organic phase, dry and filter, and use the product for later use.

[0055] S3. Dissolve the product of step S2 in dichloromethane and place it in an ice-water bath. Under nitrogen protection, slowly add 3-dimethylaminopropylamine dropwise. After the addition is complete, move the mixture to room temperature and continue stirring for 24 hours. Distill under reduced pressure to obtain a viscous liquid.

[0056] S4. Dissolve the viscous liquid from step S3 in ethanol, then add 3-bromo-propyltrimethylammonium bromide, heat to 90°C and stir for 24 hours, cool to room temperature, remove the solvent by vacuum distillation, recrystallize with a mixed solution of ethanol and acetone, and dry to obtain the final product.

[0057] As a comparison, based on sample 1, the multi-branched demulsifier was replaced with PEO-PPO-PEO to obtain control sample 1; and the bisquaternary ammonium salt surfactant was replaced with rhamnolipid to obtain control sample 2.

[0058] Example 1:

[0059] 1. Pass the scum into the pH adjustment tank, add sodium carbonate to the tank for alkalization treatment, and adjust the pH to 7.25;

[0060] 2. After adjusting the pH, the scum is introduced into the ultrasonic treatment tank. 10 mg / L dehydrating agent sample 1 is added to the tank. The temperature is raised to 50℃ and demulsification is carried out under the action of the ultrasonic standing wave field. The ultrasonic frequency is fixed at 20 kHz, the ultrasonic power is adjusted to 100~600W, and the ultrasonic time is 5 min.

[0061] 3. After ultrasonic treatment, the scum enters the sludge settling tank for thermal settling to achieve water-oil separation; the water content of the bottom sediment is tested, and the water content is determined in accordance with GB / T 260—2016 "Determination of Water Content in Petroleum Products by Distillation Method";

[0062] 4. The aqueous phase is separated and introduced into an oxidation degradation tank. Hydrogen peroxide is added to the aqueous phase for oxidation degradation before discharge. The oil phase is introduced into a distillation tank and the oil layer is recovered after distillation.

[0063] The water content of the bottom sediment under different ultrasonic powers in Example 1 is as follows: Figure 2 As shown, with the increase of acoustic power, the water content of the treated scum first decreases and then increases, indicating that there is an optimal value for ultrasonic power during ultrasonic dehydration. Microscopic images of the scum before and after ultrasonic demulsification are shown below. Figure 1 As shown, before treatment, the oil droplets and solid particles in the scum were of varying sizes and randomly dispersed in the aqueous phase. The emulsified oil was in an O / W state, with some particles suspended in the continuous aqueous phase and others encased within the oil droplets. After adding only a demulsifier without ultrasonic treatment, the sediment moisture content decreased to 38%. After ultrasonic demulsification treatment, the oil droplet size significantly increased, with small droplets colliding, coagulating, and merging into larger droplets. Most of the suspended solid particles were encased in oil droplets and detached from the continuous aqueous phase, making the aqueous phase clearer than before treatment. With increasing acoustic power, the corresponding ultrasonic intensity also increased. When the ultrasonic intensity exceeded the cavitation threshold, cavitation occurred, leading to new emulsification of the sludge and increasing the difficulty of dehydration. The results showed that a significant decrease in sediment moisture content occurred when the ultrasonic power was controlled between 200 and 400 W, with the best effect observed at 300 W.

[0064] Table 1

[0065]

[0066] Example 2:

[0067] 1. Pass the scum into the pH adjustment tank, add sodium carbonate to the tank for alkalization treatment, and adjust the pH to 7.25;

[0068] 2. After adjusting the pH, the scum was introduced into the ultrasonic treatment tank. 10 mg / L dehydrating agent sample 1 was added to the tank and the temperature was adjusted to 40~70℃. Demulsification was carried out under the action of ultrasonic standing wave field. The ultrasonic frequency was fixed at 20 kHz, the ultrasonic power was adjusted to 300W, and the ultrasonic time was 5 min.

[0069] 3. After ultrasonic treatment, the scum enters the sludge settling tank for thermal settling to achieve water-oil separation; the water content of the bottom sediment is tested, and the water content is determined in accordance with GB / T 260—2016 "Determination of Water Content in Petroleum Products by Distillation Method";

[0070] 4. The aqueous phase is separated and introduced into an oxidation degradation tank. Hydrogen peroxide is added to the aqueous phase for oxidation degradation before discharge. The oil phase is introduced into a distillation tank and the oil layer is recovered after distillation.

[0071] The sediment moisture content at different treatment temperatures in Example 2 is as follows: Figure 3 As shown, the results indicate that when the temperature is controlled at 50~60℃, the moisture content of the bottom sediment decreases significantly, and the effect is best at 55℃, with a high dehydration rate.

[0072] As the ultrasonic temperature increases, the viscosity of the scum decreases. Under the action of ultrasonic mechanical vibration, the movement of oil droplets intensifies, the number of collisions and aggregations between oil droplets increases, and large oil droplets are quickly formed, improving the dehydration effect. At the same time, the increase in temperature leads to a decrease in the film stability and mechanical strength of the oil-water interface, making it easier for oil droplets to coalesce. The scum dehydration rate gradually decreases at high temperatures because at low temperatures, ultrasonic cavitation increases with increasing temperature, improving the dehydration effect; however, after exceeding the critical temperature point of the sample, the sound intensity and cavitation effect of ultrasound gradually weaken, resulting in a poorer dehydration effect.

[0073] Example 3:

[0074] 1. Pass the scum into the pH adjustment tank, add sodium carbonate to the tank for alkalization treatment, and adjust the pH to 7.25;

[0075] 2. After adjusting the pH, the scum was introduced into the ultrasonic treatment tank. 10 mg / L of dehydrating agent (samples 1-3 and control samples 1-2) was added to the tank. The temperature was adjusted to 55℃, and demulsification was carried out under the action of the ultrasonic standing wave field. The ultrasonic frequency was fixed at 20kHz, the ultrasonic power was adjusted to 300 W, and the ultrasonic time was 5 min.

[0076] 3. After ultrasonic treatment, the scum enters the sludge settling tank for thermal settling to achieve water-oil separation; the water content of the bottom sediment is tested, and the water content is determined in accordance with GB / T 260—2016 "Determination of Water Content in Petroleum Products by Distillation Method";

[0077] 4. The aqueous phase is separated and introduced into an oxidation degradation tank. Hydrogen peroxide is added to the aqueous phase for oxidation degradation before discharge. The oil phase is introduced into a distillation tank and the oil layer is recovered after distillation.

[0078] The moisture content of the sediment after treatment with different dewatering agents in Example 3 is as follows: Figure 4 As shown, the results indicate that the dehydration effect achieved using samples 1-3 of this application is far superior to that of control sample 1 and control sample 2.

[0079] Oily sludge from refineries has a complex composition, and it is difficult to achieve the desired dehydration effect using a single demulsifier or flocculant. This application prepares a dual-headed quaternary ammonium salt surfactant and a multi-branched polyether demulsifier, which are combined with cationic polyacrylamide flocculant to form a dehydrating agent with high dehydration efficiency when used to treat oily sludge. Firstly, cationic polyacrylamide is used as a flocculant to flocculate sludge in scum, forming loose small flocs for removal. Secondly, the bisquaternary ammonium salt surfactant is obtained by modifying rhamnolipin, a biodegradable biosurfactant with demulsifying properties. Through modification, a bisquaternary ammonium salt is grafted onto its surface, resulting in high solubility and adsorption bridging, further promoting flocculation. Thirdly, the multi-branched demulsifier is based on hyperbranched polyamide-amine polymers, utilizing the amino groups on the chains as active sites to polymerize PEO-PPO-PEO chains. Multiple branched polyether chains diffuse out from the hyperbranched polymer chain structure, making it more conducive to contact with oil droplet surfaces in three-dimensional space. With the synergistic effect of the bisquaternary ammonium salt surfactant reducing the interfacial film strength, it can also disperse more quickly at the oil-water interface, promoting oil droplet co-aggregation, improving demulsification efficiency, and facilitating oil-water separation.

[0080] In addition, this application further tested the treatment effect of aqueous phase degradation and oil phase distillation in step four. The results showed that the treatment process provided by this application achieved a COD removal rate of over 95% and an oil phase recovery rate of over 97% in the final discharged aqueous phase after scum treatment, thus completing environmental governance and resource recovery. This technology can be applied and promoted as an effective treatment method for scum dewatering in refineries to save energy and protect the environment.

[0081] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and illustrations shown and described herein.

Claims

1. A process for the deep dewatering of oil-containing scum, characterized in that, It comprises the following steps: I. The dregs are passed into a pH adjusting tank, and sodium carbonate is added to the tank for alkalization treatment, so as to adjust the pH to 7-7.5; II. The dregs after pH adjustment are passed into an ultrasonic treatment tank, and a dehydrating agent is added to the tank, the temperature is raised to 40-60℃, and demulsification is carried out under the action of ultrasonic standing wave field; III. After ultrasonic treatment, the dregs are passed into a waste oil settling tank for thermal settling, so as to realize water-oil separation; IV. The water layer is cut off and passed into an oxidation degradation tank, and hydrogen peroxide is added to the water phase for oxidation degradation, and then discharged; The oil phase is passed into a distillation tank, and the oil layer is recovered after distillation; The oil-containing dregs dehydrating agent comprises, by mass percentage: 50-70% multi-branched demulsifier, 20-40% double quaternary ammonium salt surfactant, 10% flocculant, and the balance of water; The multi-branched demulsifier is first prepared by Michael addition reaction and amidation reaction using triethylenetetramine as a reaction initiator and methyl acrylate as a monomer to obtain hyperbranched polyamide-amine; then under alkaline conditions, propylene oxide, ethylene oxide and propylene oxide are sequentially added to polymerize a multi-branched polyether demulsifier; The preparation process of the double quaternary ammonium salt surfactant is as follows: S1. In a reaction bottle, add rhamnolipid and a catalytic amount of DMAP, and drop acyl chloride with sulfur monochloride. The reaction product is dissolved in dichloromethane and placed in an ice water bath for standby; S2. Dissolve 6-aminohexanoic acid methyl ester hydrochloride and triethylamine in dichloromethane, then slowly drop into step S1, after the drop is completed, the temperature is raised to 30℃, and the stirring reaction is continued for 24h. Add sodium hydroxide solution, collect the organic phase, dry and filter, and the product is ready for use; S3. Dissolve the product of step S2 in dichloromethane and place it in an ice water bath. Slowly drop 3-dimethylaminopropylamine under nitrogen protection. After the drop is completed, the temperature is raised to room temperature and the stirring reaction is continued for 24h. Distillation under reduced pressure gives a viscous liquid; S4. Dissolve the viscous liquid of step S3 in ethanol, then add 3-bromo-propyl trimethyl ammonium bromide, stir at 90℃ for 24h, cool to room temperature, distill under reduced pressure, recrystallize with a mixed solution of ethanol and acetone, and dry to obtain the product.

2. The process for the deep dewatering of oil-containing scum according to claim 1, characterized in that, The preparation process of the multi-branched demulsifier is as follows: 1) In a reaction bottle, add a certain amount of triethylenetetramine, add methanol as a solvent and stir to mix uniformly, then slowly drop equal molar amount of methyl acrylate under ice water bath and nitrogen protection, after the drop is completed, the temperature is raised to 35℃ and the stirring reaction is continued for 48h; then the temperature is raised to 60, 80, 100, 120 and 140 in stages, respectively, and reacted for 2h each time. Vacuum is applied during the reaction process. The obtained viscous liquid is hyperbranched polyamide-amine; 2) Add hyperbranched polyamide-amine to a reaction kettle, add a catalytic amount of potassium hydroxide, vacuumize, raise the temperature to 120℃, then slowly pass in propylene oxide, when the kettle pressure drops to negative pressure and stabilizes, sequentially pass in ethylene oxide and propylene oxide into the kettle, and keep the temperature constant until the kettle pressure drops to negative pressure and stabilizes.

3. The process for the deep dewatering of oil-containing scum according to claim 2, characterized in that, In step 2), the addition amount of raw materials is as follows: hyperbranched polyamide-amine 1 part, propylene oxide 10 parts, ethylene oxide 200 parts, propylene oxide 200 parts.

4. The process for the deep dewatering of oil containing scum according to claim 1, characterized in that, The flocculant is cationic polyacrylamide.

5. The process for the deep dewatering of oil containing scum according to claim 1, characterized in that, In the second step, the amount of the dehydrating agent is 5-10 mg / L.

6. The process of deep dewatering of oil containing scum according to claim 1, characterized in that, In the second step, the ultrasonic conditions are as follows: ultrasonic frequency 20-40 kHz, power 200-400 W, and ultrasonic time 5-7 min.

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