Cascade coupling extraction method for cold-rolled oil sludge

Abstract

The invention relates to the technical field of environmental protection and resource reutilization, in particular to a cascade coupling extraction method for cold-rolled oil sludge, which comprises the following steps: based on the random intersolubility of acetone, petroleum hydrocarbon substances and water and the complete immiscibility of water and petroleum hydrocarbon, carrying out primary extraction on the oil sludge by using low-dose acetone; after the recoverable oil product with relatively high solubility is fully extracted into the acetone solution, adding a large dosage of water needle to carry out secondary extraction on the acetone, so that the acetone is extracted into the water, and the recovered oil product is separated from the acetone and floats up to the acetone dilute solution based on the density to achieve the purpose of separating the acetone from the recovered oil product; the method disclosed by the invention has the characteristics that the process is simple, the use amount of acetone is small, the recovery rate of oil products in the oil sludge is high, and the extraction agent can be recycled, and the efficiency and the economical efficiency of the extraction method in the reduction and recycling processes of the cold-rolled oil sludge can be effectively improved.

Description

Technical Field

[0001] The invention relates to the technical field of environmental protection and resource recycling, and in particular to a step-coupling extraction method for cold rolling sludge. Background Art

[0002] In the process of cold rolling production in steel mills, a large amount of lubricating oil is used to reduce mechanical friction, reduce wear, improve the stable operation rate of equipment and reduce maintenance costs, thereby improving production efficiency, ensuring the normal operation of equipment and the stability of product quality. However, with the continuous expansion of production scale and continuous optimization of production technology, the use of lubricating oil has greatly increased, and a large amount of cold rolling sludge has been generated in this process.

[0003] Cold rolling sludge is a typical hazardous solid waste in the steel industry. It is an extremely complex mixture of oil, water and solid. Its main components are water, lubricating oil and iron powder. It is severely emulsified, has a bad smell, is black and viscous, and is difficult to biodegrade. During the rolling process, the lubricating oil is repeatedly rolled, washed and settled, and is gradually oxidized and deteriorated by various factors such as temperature, pressure, air, dust and metal mechanical impurities. In the waste rolling liquid collection tank, the rolling oil sludge that sinks to the bottom is the rolling oil sludge. Because of its complex composition, high solid content of about 6% to 40%, and high degree of emulsification, it is difficult to handle.

[0004] The appearance of steel rolling sludge is dark black and viscous, and the internal structure is oil-in-water. The continuous oil phase wraps the solid iron particles and emulsified water droplets. The oil, water and solid phases are intertwined and highly emulsified. The emulsified water droplets are almost spherical. The oil phase in cold rolling sludge is mainly composed of fatty acid colloids such as palmitic acid, oleic acid, and stearic acid, and the solid phase minerals are mainly Fe 3 O 4 and metallic Fe.

[0005] In the steel refining and processing industry, especially in the cold rolling production process, a large amount of cold rolling sludge is generated. There are about 20% lubricating oil with recycling potential and about 50% iron-based particles in these sludges. However, since this type of sludge is highly stable and highly emulsified oil-containing sludge, and contains more than 40% colloids and asphalt, the cold rolling sludge is highly viscous and stable in nature, making it difficult to extract this type of sludge. Conventional extraction methods use a large amount of extractant and are less economical.

[0006] In the existing cold rolling sludge treatment methods, the composition of sludge from different sources varies greatly, and the applicable treatment methods are also different. Due to the drastic impact of the cold rolling process, the iron-based particles in the cold rolling sludge have a strong adsorption capacity for oil. If the oil and sludge are to be separated, a large amount of water vapor and hot water are required to heat and wash the oily sludge, resulting in high energy consumption in the process; the volume of oily sludge is large, and the proportion of harmful substances per unit mass of sludge is high, which poses great harm to the environment and requires high treatment. If the treatment is not appropriate, the separation of oil and sludge in the cold rolling sludge will not be complete. Even if the oil content in the sludge is reduced, the purpose of sludge separation is not completely achieved, and pollution will still occur; in the process of treating cold rolling sludge, safety issues are a challenge that cannot be ignored. Since oil sludge contains hazardous substances, such as iron powder, grease, etc., if it is not handled properly, it may cause safety accidents; the oil content in oil sludge is high, sometimes as high as 20% to 30%. Although there are research and technical attempts to recycle resources in cold rolling oil sludge, such as by preparing biodiesel, the recovery rate is low when oil products are recovered; and only using a single physical and chemical method to separate oily sludge cannot meet environmental standards. Therefore, the existing cold rolling oil sludge treatment methods have the problems of high treatment cost, easy to cause secondary pollution, insufficient safety, and low resource recovery rate. Summary of the invention

[0007] In view of the deficiencies of the above-mentioned prior art, the object of the present invention is to provide a cascade coupled extraction method for cold rolling sludge. Based on the arbitrary miscibility of acetone, petroleum hydrocarbon substances and water, and the complete immiscibility of water and petroleum hydrocarbons, the present invention uses low-dose acetone to perform preliminary extraction on the sludge, and after the recoverable oil products with greater solubility are fully extracted into the acetone solution, a large dose of water is added to perform secondary extraction on the acetone, so as to achieve the purpose of extracting acetone into water, separating the recovered oil products from the acetone and floating on the acetone dilute solution based on density to achieve the purpose of separating acetone and recovered oil, completing the cascade coupled extraction process of cold rolling sludge with low-dose acetone and large-dose water, and after this process, separating and recovering the acetone in the aqueous solution by boiling point difference and recycling it.

[0008] In order to solve the above technical problems, the present invention adopts the following technical solutions: A step-coupling extraction method for cold rolling sludge comprises the following steps: Under room temperature conditions, acetone is added to the cold-rolled sludge, and the mixture is fully stirred for extraction, so that the recoverable oil in the cold-rolled sludge is dissolved in acetone to obtain an acetone solution after the oil is extracted.

[0009] Water is added to the acetone solution after the oil is extracted, and the solution is stirred at room temperature for secondary extraction, so that the acetone is extracted into the water to obtain a mixed solution containing recoverable oil, acetone and water and a solid residue.

[0010] The mixed liquid is centrifuged, and the upper oil phase is directly recovered after separation, the lower acetone aqueous solution is distilled to recover acetone, and the solid phase residue is recovered and reused to achieve the step-by-step coupled extraction of cold rolling sludge.

[0011] The invention first adds acetone to the cold-rolled oil sludge, fully stirs and performs an extraction, based on the arbitrary miscibility of acetone, petroleum hydrocarbon substances and water, and the complete immiscibility of water and petroleum hydrocarbons, uses low-dose acetone to perform preliminary extraction on the oil sludge, dissolves the recoverable oil in the cold-rolled oil sludge in acetone, and obtains an acetone solution after the recoverable oil with greater solubility is fully extracted into the acetone solution, and then adds a large dose of water to the acetone solution after the oil is extracted to perform secondary extraction on the acetone, so as to extract the acetone into the water and obtain a mixed solution containing recoverable oil, acetone and water; finally, the mixed solution is centrifuged, the recovered oil is separated from the acetone and floats on the acetone dilute solution based on density, so as to achieve the purpose of separating the acetone and the recovered oil, and complete the step-coupling extraction process of the cold-rolled oil sludge by low-dose acetone and large-dose water. The treatment method of the invention has the characteristics of small amount of extractant, high extraction efficiency, simple process and low operation cost.

[0012] The cold rolling sludge of the present invention comprises oil, water and solid phase residue. After adding acetone to the cold rolling sludge for primary extraction, the recoverable oil in the cold rolling sludge is dissolved in acetone to obtain an extracted acetone solution, and the extracted acetone solution also contains solid phase residue. Then, water is directly added to the extracted acetone solution for secondary extraction, and acetone is extracted into water to obtain a mixed solution containing recoverable oil, acetone and water and solid phase residue. Finally, centrifugal separation is performed, and the upper oil phase is directly recovered after separation, and the lower acetone aqueous solution is distilled to recover acetone, and the solid phase residue is recovered and reused, so as to realize the step-coupling extraction of the cold rolling sludge.

[0013] In a preferred embodiment of the present invention, the usage ratio of acetone to cold rolling sludge is 2 mL~3 mL:1 g.

[0014] In a preferred embodiment of the present invention, the usage ratio of deionized water to cold rolling sludge is 9 mL~11 mL:1 g.

[0015] In a preferred embodiment of the present invention, the volume percentage concentration of acetone is 75% to 85%, the acetone is commercially available industrial grade acetone with a purity of 99.5%, and a dilution solution of deionized water is added to dilute it to a volume percentage concentration of 75% to 85%.

[0016] In a preferred embodiment of the present invention, the distillation temperature is 40°C.

[0017] In a preferred embodiment of the present invention, the extraction time is 30 min to 40 min.

[0018] In a preferred embodiment of the present invention, the secondary extraction time is 30 min to 40 min.

[0019] In a preferred embodiment of the present invention, the centrifugal separation time is 14 min to 15 min.

[0020] In a preferred embodiment of the present invention, the cold-rolled sludge is composed of three phases: oil, water and solid, wherein the three phases may be in any proportion. The cold-rolled sludge containing the three phases of oil, water and solid obtained from industrial production may be processed by the step-coupling extraction method of the present invention.

[0021] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention first adds acetone to the cold-rolled sludge, fully stirs and performs an extraction, based on the arbitrary miscibility of acetone, petroleum hydrocarbon substances and water, and the complete immiscibility of water and petroleum hydrocarbons, uses low-dose acetone to perform preliminary extraction on the sludge, dissolves the recoverable oil in the cold-rolled sludge in acetone, and after the recoverable oil with a larger solubility is fully extracted into the acetone solution, an acetone solution after the oil is extracted is obtained, and then a large dose of water is added to the acetone solution after the oil is extracted to perform secondary extraction on the acetone, so as to extract the acetone into the water and obtain a mixed solution containing recoverable oil, acetone and water; finally, the mixed solution is centrifuged, the recovered oil is separated from the acetone and floats on the acetone dilute solution based on density, so as to achieve the purpose of separating acetone and recovered oil, and complete the low-dose acetone and large-dose water cascade coupling extraction process of cold-rolled sludge. The treatment method of the present invention has the characteristics of small amount of extractant, high extraction efficiency, simple process and low operating cost.

[0022] 2. The present invention makes use of the fact that the extraction method can recover petroleum hydrocarbons in cold-rolled sludge quickly and efficiently, and that acetone as an extractant is completely miscible with lubricating oil and water. A small amount of acetone is used to quickly extract the recyclable components in the sludge. Based on the characteristics that water is miscible with acetone but not with the recyclable oil components dissolved in acetone, and the specific gravity of the recyclable components is lower than that of water, a large amount of water is used to wash the acetone solution containing petroleum hydrocarbons, so that the recyclable components are precipitated on the water surface, thereby achieving the purpose of efficiently extracting the recyclable components in the cold-rolled sludge with a limited extractant, and recovering the acetone for recycling through water extraction and distillation.

[0023] 3. The method of the present invention has the characteristics of simple process, small amount of acetone, high oil recovery rate in sludge, and recyclable extractant, which can effectively improve the efficiency and economy of the extraction method in the process of reducing and recycling cold rolling sludge. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1It is a process flow chart of the present invention.

[0025] Figure 2 Among them, (a) ~ (b) are macroscopic images of the cold-rolled sludge of the present invention, and (c) is a microscopic image of the cold-rolled sludge.

[0026] Figure 3 The figure is the variation curve of oil content of the residue after extraction with acetone of different concentrations in the present invention.

[0027] Figure 4 The figure is the variation curve of oil content of the residue after extraction with different acetone dosages in the present invention.

[0028] Figure 5 This is the curve showing the effect of the amount of deionized water on the oil recovery rate in the present invention.

[0029] Figure 6 This is the influence curve of the distillation temperature on the acetone recovery rate of the present invention.

[0030] Figure 7 In the figure, (a) is the microscopic morphology of the bottom mud of the oil-water separation tank of the oilfield joint station, and (b) is the microscopic morphology of the oil-containing slag in the flotation tank of the refinery wastewater station.

[0031] Figure 8 In the figure, (a)~(b) are the extraction and separation effect diagrams before and after the tank bottom mud treatment, and (c)~(d) are the extraction and separation effect diagrams before and after the oily scum treatment.

[0032] Fig. 9 In the figure, (a) is the extraction effect diagram of acetone solution before and after extracting the oil content of cold rolling sludge; (b) is the effect diagram of deionized water extraction of acetone and centrifugal separation to recover the oil product; (c) is the recovered cold rolling oil; (d) is a comparison diagram of the properties of the recovered oil product and the commercially available product.

[0033] Fig.10 In the figure, (a) is the microstructure before solid phase treatment; (b) is the microstructure of the remaining particles after solid phase treatment; (c) is the appearance after drying after solid phase treatment; (d) is the main component of the solid phase. DETAILED DESCRIPTION

[0034] The following is a detailed description of the technical solutions in the embodiments of the present invention in combination with the preferred embodiments and the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0035] It should be noted that all professional terms used in the present invention are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention. Unless otherwise specifically stated, various raw materials, reagents, instruments and equipment used in the following embodiments of the present invention can be purchased from the market or prepared by existing methods.

[0036] The prior art patent with publication number CN113004926A discloses a method and device for extracting oil from oil-containing substances using a solvent and recovering the solvent. One of the important key points for recovering high-purity solvents is that the solvent used has the characteristic that its miscibility with water decreases as the temperature increases. Therefore, when separating the solvent and oils with a boiling point close to the solvent, it can be achieved by adding water, changing the temperature, and performing liquid-liquid separation. The prior art patent with publication number CN114057365A discloses a chemical extraction method and extraction system for oil sludge separation. In this technology, an organic extract containing equal weights of acetone and carbon disulfide is added to generate an extract containing organic matter and a precipitate.

[0037] In the existing cold rolling sludge treatment methods, the composition of sludge from different sources is quite different, and the applicable treatment methods are also different. In view of the problems of high treatment cost, easy secondary pollution, insufficient safety and low resource recovery rate in the existing cold rolling sludge treatment methods, the present invention proposes a step-coupling extraction method for cold rolling sludge. Based on the arbitrary solubility of acetone, petroleum hydrocarbon substances and water, and the complete immiscibility of water and petroleum hydrocarbons, the present invention uses low-dose acetone to extract the sludge once. In the first extraction, the ratio of acetone to cold rolling sludge is 2 mL~3 mL:1 g. After the recoverable oil with larger solubility is fully extracted into the acetone solution, a large dose of water is added to perform secondary extraction on acetone. In the secondary extraction, the ratio of water to cold rolling sludge is 8 mL~12 mL:1 g, to extract acetone into water, separate the recovered oil from acetone and float on the acetone dilute solution based on density to achieve the purpose of separating acetone and recovered oil, and complete the low-dose acetone and high-dose water cascade coupling extraction process of cold rolling sludge. The process flow is as follows Figure 1 The operation of using solvent for extraction is well known. The innovation of the present invention mainly lies in the step-coupling extraction method of using low-dose acetone for primary extraction and large-dose water for secondary extraction. The treatment method of the present invention has the characteristics of small amount of extractant, high extraction efficiency, simple process and low operating cost.

[0038] Example 1 A step-coupling extraction method for cold rolling sludge comprises the following steps: (1) Take a certain amount of cold-rolled sludge and add an acetone solution with a volume concentration of 80% to the cold-rolled sludge at room temperature. The ratio of acetone solution to cold-rolled sludge is 30 mL:15 g. Stir thoroughly for one extraction. The extraction time is 35 min. The recoverable oil in the cold-rolled sludge is dissolved in acetone to obtain an acetone solution after the oil is extracted.

[0039] (2) Deionized water was added to the acetone solution after the oil was extracted. The ratio of deionized water to cold rolling sludge was 150 mL:15 g. The solution was fully stirred at room temperature for secondary extraction. The secondary extraction time was 35 min. The acetone was extracted into the deionized water to obtain a mixed solution containing recoverable oil, acetone and water, as well as a solid residue.

[0040] (3) The mixture obtained in step (2) is subjected to three-phase separation by centrifuging at 2500 rpm for 15 min. After separation, the upper oil phase is directly recovered, and the solid phase residue is further recovered by thermal decomposition to recover oil and iron. The lower acetone aqueous solution liquid phase is distilled at 40° C. to recover acetone and recycle it, thereby realizing the step-by-step coupled extraction of cold rolling sludge. In this process, the water content of the recovered oil is less than 1%, the oil recovery rate is greater than 80%, the acetone recovery rate is more than 80%, and the water content is less than 5%.

[0041] Example 2 A step-coupling extraction method for cold rolling sludge comprises the following steps: (1) Take a certain amount of cold-rolled sludge and add an acetone solution with a volume concentration of 80% to the cold-rolled sludge at room temperature. The ratio of acetone solution to cold-rolled sludge is 45 mL:15 g. The mixture is fully stirred for one extraction. The extraction time is 35 min. The recoverable oil in the cold-rolled sludge is dissolved in acetone to obtain an acetone solution after the oil is extracted.

[0042] (2) Deionized water was added to the acetone solution after the oil was extracted. The ratio of deionized water to cold rolling sludge was 150 mL:15 g. The solution was fully stirred at room temperature for secondary extraction. The secondary extraction time was 35 min. The acetone was extracted into the deionized water to obtain a mixed solution containing recoverable oil, acetone and water, as well as a solid residue.

[0043] (3) The mixture obtained in step (2) is subjected to three-phase separation by centrifuging at 2500 rpm for 15 min. After separation, the upper oil phase is directly recovered, and the solid phase residue is further recovered by thermal decomposition to recover oil and iron. The lower acetone aqueous solution liquid phase is distilled at 40° C. to recover acetone and recycle it, thereby realizing the step-by-step coupled extraction of cold rolling sludge.

[0044] Example 3 A step-coupling extraction method for cold rolling sludge comprises the following steps: (1) Take a certain amount of cold-rolled sludge and add 75% acetone solution to the cold-rolled sludge at room temperature. The ratio of acetone solution to cold-rolled sludge is 30 mL:15 g. Stir thoroughly for one extraction. The extraction time is 30 min. Dissolve the recoverable oil in the cold-rolled sludge in acetone to obtain an acetone solution after the oil is extracted.

[0045] (2) Deionized water was added to the acetone solution after the oil was extracted. The ratio of deionized water to cold rolling sludge was 135 mL:15 g. The solution was fully stirred at room temperature for secondary extraction. The secondary extraction time was 30 min. The acetone was extracted into the deionized water to obtain a mixed solution containing recoverable oil, acetone and water, as well as a solid residue.

[0046] (3) The mixture obtained in step (2) is subjected to three-phase separation at 2500 rpm for 15 min by centrifuging. After separation, the upper oil phase is directly recovered, and the solid phase residue is further recovered by thermal decomposition to recover oil and iron. The lower acetone aqueous solution liquid phase is distilled at 40° C. to recover acetone and recycle it, thereby realizing the step-by-step coupled extraction of cold rolling sludge.

[0047] Example 4 (1) Take a certain amount of cold-rolled sludge and add an acetone solution with a volume concentration of 85% to the cold-rolled sludge at room temperature. The ratio of acetone solution to cold-rolled sludge is 30 mL:15 g. Stir thoroughly for one extraction. The extraction time is 40 min. The recoverable oil in the cold-rolled sludge is dissolved in acetone to obtain an acetone solution after the oil is extracted.

[0048] (2) Deionized water was added to the acetone solution after the oil was extracted. The ratio of deionized water to cold rolling sludge was 165 mL:15 g. The solution was fully stirred at room temperature for secondary extraction. The secondary extraction time was 40 min. The acetone was extracted into the deionized water to obtain a mixed solution containing recoverable oil, acetone and water, as well as a solid residue.

[0049] (3) The mixture obtained in step (2) is subjected to three-phase separation at 2500 rpm for 15 min by centrifuging. After separation, the upper oil phase is directly recovered, and the solid phase residue is further recovered by thermal decomposition to recover oil and iron. The lower acetone aqueous solution liquid phase is distilled at 40° C. to recover acetone and recycle it, thereby realizing the step-by-step coupled extraction of cold rolling sludge.

[0050] Comparative Example 1 Take a certain amount of cold-rolled sludge, add 60% acetone solution by volume to the cold-rolled sludge at room temperature, the ratio of acetone solution to cold-rolled sludge is 30 mL:15 g, stir thoroughly for one extraction, the extraction time is 40 min, dissolve the recoverable oil in the cold-rolled sludge in acetone, and obtain the acetone solution after the oil is extracted.

[0051] Comparative Example 2 Take a certain amount of cold-rolled sludge, add acetone solution with a volume concentration of 70% to the cold-rolled sludge at room temperature, the dosage ratio of acetone solution to cold-rolled sludge is 30 mL:15 g, stir thoroughly for one extraction, the extraction time is 40 min, dissolve the recoverable oil in the cold-rolled sludge in acetone, and obtain an acetone solution after the oil is extracted.

[0052] Comparative Example 3 Take a certain amount of cold-rolled sludge, add 90% acetone solution to the cold-rolled sludge at room temperature, the ratio of acetone solution to cold-rolled sludge is 30 mL:15 g, stir thoroughly for one extraction, the extraction time is 40 min, dissolve the recoverable oil in the cold-rolled sludge in acetone, and obtain the acetone solution after the oil is extracted.

[0053] Comparative Example 4 Take a certain amount of cold-rolled sludge, add acetone solution with a volume concentration of 80% to the cold-rolled sludge at room temperature, the dosage ratio of acetone solution to cold-rolled sludge is 15 mL:15 g, stir thoroughly for one extraction, the extraction time is 40 min, dissolve the recoverable oil in the cold-rolled sludge in acetone, and obtain an acetone solution after the oil is extracted.

[0054] Comparative Example 5 Take a certain amount of cold-rolled sludge, add acetone solution with a volume concentration of 80% to the cold-rolled sludge at room temperature, the dosage ratio of acetone solution to cold-rolled sludge is 60 mL:15 g, stir thoroughly for one extraction, the extraction time is 40 min, dissolve the recoverable oil in the cold-rolled sludge in acetone, and obtain an acetone solution after the oil is extracted.

[0055] Comparative Example 6 (1) Take a certain amount of cold-rolled sludge and add an acetone solution with a volume concentration of 80% to the cold-rolled sludge at room temperature. The ratio of acetone solution to cold-rolled sludge is 30 mL:15 g. The mixture is fully stirred for one extraction. The extraction time is 40 min. The recoverable oil in the cold-rolled sludge is dissolved in acetone to obtain an acetone solution after the oil is extracted.

[0056] (2) Deionized water was added to the acetone solution after the oil was extracted. The ratio of deionized water to cold rolling sludge was 50 mL:15 g. The solution was fully stirred at room temperature for secondary extraction. The secondary extraction time was 40 min. The acetone was extracted into the deionized water to obtain a mixed solution containing recoverable oil, acetone and water, as well as a solid residue.

[0057] Comparative Example 7 (1) Take a certain amount of cold-rolled sludge and add an acetone solution with a volume concentration of 80% to the cold-rolled sludge at room temperature. The ratio of acetone solution to cold-rolled sludge is 30 mL:15 g. The mixture is fully stirred for one extraction. The extraction time is 40 min. The recoverable oil in the cold-rolled sludge is dissolved in acetone to obtain an acetone solution after the oil is extracted.

[0058] (2) Deionized water was added to the acetone solution after the oil was extracted. The ratio of deionized water to cold-rolled sludge was 100 mL:15 g. The solution was fully stirred at room temperature for secondary extraction. The secondary extraction time was 40 min. The acetone was extracted into the deionized water to obtain a mixed solution containing recoverable oil, acetone and water, as well as a solid residue.

[0059] Comparative Example 8 (1) Take a certain amount of cold-rolled sludge and add an acetone solution with a volume concentration of 80% to the cold-rolled sludge at room temperature. The ratio of acetone solution to cold-rolled sludge is 30 mL:15 g. The mixture is fully stirred for one extraction. The extraction time is 40 min. The recoverable oil in the cold-rolled sludge is dissolved in acetone to obtain an acetone solution after the oil is extracted.

[0060] (2) Deionized water was added to the acetone solution after the oil was extracted. The ratio of deionized water to cold-rolled sludge was 200 mL:15 g. The solution was fully stirred at room temperature for secondary extraction. The secondary extraction time was 40 min. The acetone was extracted into the deionized water to obtain a mixed solution containing recoverable oil, acetone and water, as well as a solid residue.

[0061] Comparative Example 9 A step-coupling extraction method for cold rolling sludge comprises the following steps: (1) Take a certain amount of cold-rolled sludge and add an acetone solution with a volume concentration of 80% to the cold-rolled sludge at room temperature. The ratio of acetone solution to cold-rolled sludge is 30 mL:15 g. Stir thoroughly for one extraction. The extraction time is 35 min. The recoverable oil in the cold-rolled sludge is dissolved in acetone to obtain an acetone solution after the oil is extracted.

[0062] (2) Deionized water was added to the acetone solution after the oil was extracted. The ratio of deionized water to cold rolling sludge was 150 mL:15 g. The solution was fully stirred at room temperature for secondary extraction. The secondary extraction time was 35 min. The acetone was extracted into the deionized water to obtain a mixed solution containing recoverable oil, acetone and water, as well as a solid residue.

[0063] (3) The mixture obtained in step (2) is subjected to three-phase separation at 2500 rpm for 15 min by centrifuging. After separation, the upper oil phase is directly recovered, and the solid phase residue is further recovered by thermal decomposition to recover oil and iron. The lower acetone aqueous solution liquid phase is distilled at 30° C. to recover acetone and recycle it, thereby realizing the step-by-step coupled extraction of cold rolling sludge.

[0064] Comparative Example 10 A step-coupling extraction method for cold rolling sludge comprises the following steps: (1) Take a certain amount of cold-rolled sludge and add an acetone solution with a volume concentration of 80% to the cold-rolled sludge at room temperature. The ratio of acetone solution to cold-rolled sludge is 30 mL:15 g. Stir thoroughly for one extraction. The extraction time is 35 min. The recoverable oil in the cold-rolled sludge is dissolved in acetone to obtain an acetone solution after the oil is extracted.

[0065] (2) Deionized water was added to the acetone solution after the oil was extracted. The ratio of deionized water to cold rolling sludge was 150 mL:15 g. The solution was fully stirred at room temperature for secondary extraction. The secondary extraction time was 35 min. The acetone was extracted into the deionized water to obtain a mixed solution containing recoverable oil, acetone and water, as well as a solid residue.

[0066] (3) The mixture obtained in step (2) is subjected to three-phase separation at 2500 rpm for 15 min by centrifuging. After separation, the upper oil phase is directly recovered, and the solid phase residue is further recovered by thermal decomposition to recover oil and iron. The lower acetone aqueous solution liquid phase is distilled at 35° C. to recover acetone and recycle it, thereby realizing the step-by-step coupled extraction of cold rolling sludge.

[0067] Comparative Example 11 A step-coupling extraction method for cold rolling sludge comprises the following steps: (1) Take a certain amount of cold-rolled sludge and add an acetone solution with a volume concentration of 80% to the cold-rolled sludge at room temperature. The ratio of acetone solution to cold-rolled sludge is 30 mL:15 g. Stir thoroughly for one extraction. The extraction time is 35 min. The recoverable oil in the cold-rolled sludge is dissolved in acetone to obtain an acetone solution after the oil is extracted.

[0068] (2) Deionized water was added to the acetone solution after the oil was extracted. The ratio of deionized water to cold rolling sludge was 150 mL:15 g. The solution was fully stirred at room temperature for secondary extraction. The secondary extraction time was 35 min. The acetone was extracted into the deionized water to obtain a mixed solution containing recoverable oil, acetone and water, as well as a solid residue.

[0069] (3) The mixture obtained in step (2) is subjected to three-phase separation at 2500 rpm for 15 min by centrifuging. After separation, the upper oil phase is directly recovered, and the solid phase residue is further recovered by thermal decomposition to recover oil and iron. The lower acetone aqueous solution liquid phase is distilled at 45° C. to recover acetone and recycle it, thereby realizing the step-by-step coupled extraction of cold rolling sludge.

[0070] The undisclosed steps in Comparative Examples 1 to 11 of the present invention are the same as the steps in Example 1.

[0071] Results Analysis Analysis of properties of cold rolling sludge Cold rolling sludge is an oily sludge composed of oil, water and solid phases. The properties of cold rolling sludge are shown in Table 1. Its macroscopic and microscopic morphology is as follows Figure 2 As shown in (a) to (c), Figure 2 In the figure, (a) to (b) are macroscopic images of the cold-rolled sludge of the present invention, and (c) is a microscopic image of the cold-rolled sludge. Through morphological observation and microscope detection, it can be found that the appearance of the cold-rolled sludge is dark black and viscous. Although the water content and oil content are high, it does not have obvious fluidity due to its high viscosity. Microscopic observation shows that the cold-rolled sludge has a highly emulsified oil-in-water structure, and it is difficult for chemical detergents, surfactants and other substances to pass through the oil layer to release the internal water. Based on the above analysis, it can be found that the cold-rolled sludge has high viscosity and high stability, and it is difficult to reduce viscosity and separate oil and water using conventional methods.

[0072] Table 1 Properties of cold rolling sludge

[0073] 30 mL of acetone solutions with concentrations of 60%, 70%, 80%, and 90% were added into a 500 mL beaker containing 15.0 g of cold-rolled oil sludge, respectively. After fully stirring and extracting at room temperature for 40 min, the residue was filtered by suction, and the oil content of the residue after extraction with acetone solutions of different concentrations was determined. The effect of acetone solution concentration on the extraction efficiency was investigated based on the change in the oil content of the residue.

[0074] Figure 3The figure shows the extraction effect of different acetone concentrations on cold rolling sludge. As can be seen from the figure, with the increase of acetone concentration, the oil content in the remaining residue after extraction shows a downward trend. When the acetone concentration increases from 60% to 80%, the oil content of the residue decreases significantly, indicating that most of the recoverable oil in the sludge is successfully extracted into the acetone solution, but as the acetone concentration continues to increase, the oil content in the residue continues to decrease. Considering the control of acetone volatilization rate and economic efficiency, acetone with a concentration of 80% is more suitable as an extractant for this type of sludge, and acetone concentrations within 75%~85% have a good extraction effect.

[0075] 15 mL, 30 mL, 45 mL, and 60 mL of 80% acetone solution with liquid-to-sludge ratios of 1:1, 2:1, 3:1, and 4:1 were added into a 500 mL beaker containing 15.0 g of cold-rolled sludge. After fully stirring and extracting at room temperature for 40 min, the residue was filtered by suction, and the oil content of the residue after extraction with different acetone solutions was determined. The effect of the amount of acetone solution added on the extraction efficiency of the recovered oil was investigated according to the change in the oil content of the residue.

[0076] Figure 4 The figure shows the changes in the extraction effect of cold rolling oil sludge with different 80% acetone dosages. It can be seen from the figure that with the increase of acetone dosage, the oil content in the remaining residue after extraction tends to decrease. When the acetone dosage increases from 15 mL to 45 mL, the liquid-sludge ratio increases from 1 mL:1 g to 3 mL:1 g, and the oil content of the residue decreases significantly. However, as the acetone dosage continues to increase, the oil content in the residue continues to decrease. Among them, the liquid-sludge ratio can achieve a good oil sludge extraction effect when it is 2 mL~3 mL:1 g, and the dosage is moderate. The above experimental results show that the acetone solution has the best extraction effect when the liquid-sludge ratio is 3 mL:1 g, and the sludge-liquid ratio has good economy and extraction effect in the range of 2 mL~3 mL:1 g.

[0077] 30 mL of 80% acetone solution was added into four 500 mL beakers containing 15.0 g of cold-rolled oil sludge. After fully stirring and extracting at room temperature for 40 min, 50 mL, 100 mL, 150 mL and 200 mL of deionized water were added respectively. After fully stirring and extracting for 40 minutes, the samples were centrifuged at 2500 rpm and the oil recovery rates of different samples after centrifugation were determined. The effect of the amount of deionized water added on the acetone extraction efficiency was investigated according to the changes in the oil recovery rate.

[0078] Figure 5The figure shows the separation effect of different deionized water dosages on the mixture of acetone and recovered oil products. It can be seen from the figure that with the increase of water dosage, the amount of separated oil products first increases and then decreases. When the water dosage increases from 50 mL to 150 mL, the extraction capacity of water for acetone gradually increases, and acetone and recovered oil products are effectively separated. After 150 mL of deionized water is used to extract acetone, the oil recovery rate is the highest, and the proportion of oil products obtained by centrifugal separation is greater than 90%. As the water dosage continues to increase to 200 mL, the oil separation efficiency does not increase significantly. The possible reason is that most of the acetone has been extracted by deionized water. Continuing to increase or even excessive deionized water cannot significantly improve the oil recovery efficiency. The results of this study show that when the water dosage for extracting acetone is 150 mL and the cement ratio is 10 mL:1 g, the highest extraction efficiency and oil recovery rate are achieved. The water dosage and oil-sludge ratio are in the range of 135 mL~165 mL:15 g, and the oil recovery efficiency is relatively high.

[0079] 30 mL of 80% acetone solution was added into four 500 mL beakers containing 15.0 g of cold-rolled sludge, respectively. After fully stirring and extracting at room temperature for 40 min, 150 mL of deionized water was added, and after fully stirring and extracting for 40 minutes, centrifuged at 2500 rpm for 15 min. The acetone distillation temperatures of 30℃, 35℃, 40℃, and 45℃ were used respectively, and the effect of distillation temperature on the acetone recovery rate was investigated by the change of acetone recovery rate.

[0080] Figure 6 The effect of different distillation temperatures on the acetone recovery rate can be seen from the figure that as the temperature rises, the acetone recovery rate shows a trend of first rising and then falling. When the distillation temperature rises from 30°C to 40°C, the acetone distillation recovery efficiency gradually increases. When the temperature exceeds 40°C, the recovery rate begins to decrease. This is mainly caused by the increased loss of the acetone collection process due to the high temperature. Therefore, the optimal acetone distillation recovery temperature of the present invention is 40°C.

[0081] Using the optimal process conditions, at room temperature, 75%~85% acetone solution was added, the ratio of acetone solution to cold rolling sludge was 2 mL~3 mL:1 g, and after fully stirring and extracting for 30 min~40 min, water was added, and the ratio of water to cold rolling sludge was 8mL~12 mL:1 g. After fully stirring and secondary extraction for 30 min~40 min, a centrifuge was used for three-phase separation for 15 min. After separation, the upper oil phase was directly recovered, and the liquid phase was distilled at 40°C to recover acetone and recycled.

[0082] The oil-water separation tank sludge of the oilfield joint station and the oily slag in the flotation tank of the refinery sewage station are respectively measured. The specific properties are shown in Table 2 and Figure 7 , conduct process adaptability and oil recovery verification experiments, Figure 7 In the figure, (a) is the microscopic morphology of the bottom mud of the oil-water separation tank of the oilfield joint station, and (b) is the microscopic morphology of the oil-containing slag in the flotation tank of the refinery sewage station. It can be seen that the above two types of sludge are similar to the cold-rolled sludge in the oil-in-water structure, with high viscosity and high stability.

[0083] Table 2 Basic properties and oil recovery rates of oily scum in tank sludge and flotation tank of refinery wastewater station

[0084] The step-coupling extraction process of the present invention was used to conduct process adaptability experiments on the bottom mud of the oil-water separation tank of the oilfield joint station and the oily scum in the flotation tank of the refinery sewage station, which have similar properties to the cold rolling sludge. Figure 8 In the figure, (a)~(b) are the extraction and separation effect diagrams before and after the tank bottom mud treatment, and (c)~(d) are the extraction and separation effect diagrams before and after the oily scum treatment. The results show that this process can be effectively applied to the oil recovery in the above two other fields with similar oil-in-water microstructure, high viscosity and high stability of oily sludge, and the recovery rate can reach more than 80%.

[0085] The specific process parameters of the cascade coupled extraction of the sludge at the bottom of the oil-water separation tank of the oilfield joint station are as follows: at room temperature, add 80% acetone solution, the ratio of acetone solution to cold-rolled sludge is 2 mL:1 g, and fully stir and extract for 40 minutes. Then add deionized water, the ratio of water to cold-rolled sludge is 12 mL:1 g. After fully stirring and secondary extraction for 40 minutes, use a centrifuge at 2500 rpm for three-phase separation for 15 minutes. After separation, the upper oil phase is directly recovered, and the residue containing a small amount of oil does not contain iron elements. The solid can be subsequently treated by thermal decomposition or incineration. The liquid phase is distilled at 40°C to recover acetone and recycled.

[0086] The specific process parameters of the step-by-step coupled extraction of oily slag in the flotation tank of the refinery sewage station are as follows: at room temperature, 85% acetone solution was added, and the ratio of acetone solution to cold-rolled oil sludge was 3 mL:1g. After fully stirring and extracting for 40 min, deionized water was added, and the ratio of water to cold-rolled oil sludge was 8 mL:1 g. After fully stirring and secondary extraction for 40 min, the three-phase separation was carried out at 2500 rpm by a centrifuge for 15 min. After separation, the upper oil phase was directly recovered, and the residue containing a small amount of oil did not contain recoverable iron elements, so it could be subsequently treated by pyrolysis or incineration. The liquid phase was distilled at 40°C to recover acetone and recycled.

[0087] Fig. 9The figures are the effects of oil sludge extraction at each stage of the process, including (a) before and after acetone solution dissolves and extracts the oil content of cold-rolled sludge; (b) deionized water extracts acetone and centrifuges to recover the oil; (c) recovers cold-rolled oil; (d) compares the properties of the recovered oil with those of commercially available cold-rolled sludge products. It can be seen from Figure a that the addition of acetone significantly reduces the difficulty of centrifugal separation of cold-rolled sludge. Compared with the original centrifugation result in the left figure, the acetone-extracted sample shows obvious stratification, indicating that the oil / water / solid interface stability of the cold-rolled sludge is reduced, and the oil and water are effectively extracted by acetone; and as shown in Figure a, Fig. 9 As shown in (b), in the subsequent secondary extraction step, by adding a large amount of deionized water, the acetone solution containing the extracted oil in the test tube is separated from the oil product for a second time, wherein the upper layer is the oil insoluble in water, and the lower layer is the deionized water containing low concentration of acetone. The recovered oil product after the upper layer is separated is as follows Fig. 9 As shown in (c), Fig. 9 (d) shows the infrared detection results of the upper recovered oil and the commercial cold rolling oil sludge product. It can be seen that there is no obvious difference in the functional group composition between the two, and they have the ability to be recycled. The above results show that this method can effectively utilize acetone and water as two extractants, step-coupling extraction of cold rolling oil and recycling of acetone solution.

[0088] Fig.10 The following are the test results of the solid phase of cold rolling sludge: (a) microstructure before solid phase treatment; (b) microstructure of the remaining particles after solid phase treatment; (c) appearance after solid phase drying; (d) main components of the solid phase. It can be seen that the remaining cold rolling sludge residue after treatment by this method has a simple structure, loose organization, and a single component, mainly Fe, which can be subsequently recovered as an iron resource.

[0089] In summary, the present invention takes advantage of the fact that the extraction method can recover petroleum hydrocarbons in cold-rolled sludge quickly and efficiently, and that acetone as an extractant is completely miscible with lubricating oil and water. After a small amount of acetone is used to quickly extract the recyclable components in the sludge, based on the characteristics that water and acetone are miscible but not miscible with the recoverable oil components dissolved in acetone, and the specific gravity of the recyclable components is lower than that of water, the acetone solution containing petroleum hydrocarbons is washed with a large amount of water, so that the recyclable components are precipitated on the water surface, and the purpose of efficiently extracting the recyclable components in the cold-rolled sludge by using a limited extractant, and recycling the acetone by water extraction and distillation. The method of the present invention has the characteristics of simple process, small amount of acetone, high oil recovery rate in the sludge, and recyclable extractant, which can effectively improve the efficiency and economy of the extraction method in the process of reducing and recycling cold-rolled sludge.

[0090] It should be noted that when the present invention relates to a numerical range, it should be understood that the two endpoints of each numerical range and any value between the two endpoints can be selected. Since the steps and methods used are the same as those in the embodiment, in order to avoid redundant description, the present invention describes a preferred embodiment. Although the preferred embodiments of the present invention have been described, once those skilled in the art know the basic creative concept, they can make other changes and modifications to these embodiments. Therefore, the attached protection scope is intended to be interpreted as including the preferred embodiment and all changes and modifications that fall within the scope of the present invention.

[0091] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the protection scope of the present invention and its equivalent technology, the present invention is also intended to include these changes and variations.

Claims

1. A step-coupling extraction method for cold rolling sludge, characterized in that: The following steps are involved: Under room temperature, acetone is added to the cold-rolled oil sludge, and the mixture is fully stirred for extraction, so that the recoverable oil in the cold-rolled oil sludge is dissolved in acetone to obtain an acetone solution after the oil is extracted; Adding water to the acetone solution after the oil is extracted, stirring at room temperature for secondary extraction, extracting the acetone into the water, and obtaining a mixed solution containing recoverable oil, acetone and water and a solid residue; The mixed liquid is centrifuged, and the upper oil phase is directly recovered after separation, the lower acetone aqueous solution is distilled to recover acetone, and the solid phase residue is recovered and reused to achieve the step-by-step coupled extraction of cold rolling sludge.

2. The step-coupling extraction method for cold rolling sludge according to claim 1, characterized in that: The dosage ratio of acetone to cold rolling sludge is 2 mL~3 mL:1 g.

3. The step-coupling extraction method for cold rolling sludge according to claim 1, characterized in that: The usage ratio of water to cold rolling sludge is 9 mL~11 mL:1 g.

4. The step-coupling extraction method for cold rolling sludge according to claim 1, characterized in that: The volume percentage concentration of acetone is 75%~85%.

5. The step-coupling extraction method for cold rolling sludge according to claim 1, characterized in that: The distillation temperature was 40°C.

6. The step-coupling extraction method for cold rolling sludge according to claim 1, characterized in that: The extraction time is 30 min~40 min.

7. The step-coupling extraction method for cold rolling sludge according to claim 1, characterized in that: The secondary extraction time is 30 min~40 min.

8. The step-coupling extraction method for cold rolling sludge according to claim 1, characterized in that: The centrifugation time is 14 min~16 min.

9. The step-coupling extraction method for cold rolling sludge according to claim 1, characterized in that: The cold rolling sludge consists of three phases: oil, water and solid.

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