A method for extracting hot rolling sludge by using waste alkali solution enhanced with CO2 supercritical fluid

Abstract

The invention discloses a method for enhancing the supercritical CO2 extraction of hot-rolled oil sludge with waste alkali liquor, belonging to the technical field of oil sludge treatment. The method of the invention is as follows: first, the hot-rolled oil sludge after stacking and draining is mixed and stirred with the waste alkali liquor to obtain a muddy water mixture of the hot-rolled oil sludge and the waste alkali liquor, and then the supercritical CO2 extraction technology is used for extraction. After extraction, the extraction phase enters a separator, and the extractant is separated from the extract by cooling and depressurization. After the CO2 gasifies, it enters a storage tank for recycling, and the separated oil fraction is collected; the raffinate is subjected to solid-liquid separation treatment to obtain dry iron powder and concentrated brine; the concentrated brine is filtered to remove colloid, suspended particles, chromaticity and macromolecular organic matters, and then concentrated, evaporated and crystallized and dried and dehydrated to finally obtain Na2CO3 products. The technical scheme of the invention effectively reduces the difficulty of supercritical extraction, improves the extraction efficiency, and uses waste alkali liquor for enhancement, treating waste with waste, with low treatment cost, safety and environmental protection.

Description

Technical Field

[0001] The invention belongs to the technical field of oil sludge treatment, and more specifically, relates to a method for extracting hot rolling oil sludge by using waste alkali liquor-enhanced CO2 supercritical extraction. Background Art

[0002] Hot rolling turbid water is mainly used for high-pressure water dephosphorization in billet rolling, cooling and flushing of rolling mills, rolls and rollers, etc. Hot rolling sludge is hot rolling turbid water containing billet dephosphorization iron oxide scale and equipment lubricating grease. After the large particles of iron oxide scale are removed by the cyclone well, the small particles of iron sludge and impurities are precipitated in the advection tank. The dry basis total iron content of hot rolling sludge is more than 60%, and the dry basis oil content is 1-10wt%. Due to the high oil content, it is difficult to directly return to the internal processes such as sintering and steelmaking for use. The amount of hot rolling sludge produced is large, and it is generally an oil-containing hazardous waste. It not only causes a huge waste of high-quality ferrous resources, but also makes enterprises pay high disposal costs.

[0003] The methods used by domestic and foreign steel companies to treat hot-rolled sludge are mainly divided into two categories: pyrolysis and wet processing. The pyrolysis method includes sintering and ore blending, briquetting rotary furnace, blast furnace injection, rotary kiln roasting, cement kiln co-treatment, high-temperature distillation, thermal desorption, tunnel kiln reduction, rotary hearth furnace roasting, etc., which generally have problems of high energy consumption and secondary pollution of oil fume; the wet method includes room temperature chemical cleaning, hot washing, chemical solvent extraction, etc., but due to the large consumption and high price of chemical agents, the wastewater generated needs deep treatment, etc., its large-scale application is restricted.

[0004] Supercritical fluid extraction is the most advanced physical extraction technology in the world. Supercritical fluid is a special fluid between gas and liquid with a temperature and pressure above the critical temperature and critical pressure. It has the dual physical properties of gas and liquid, with a large density and solubility similar to that of liquid, while the viscosity and diffusion rate are close to those of ordinary gas. Therefore, supercritical fluid has good permeability and solubility, as well as a very high mass transfer rate and the ability to quickly reach extraction equilibrium. It is an ideal extractant. After supercritical fluid extraction, it changes from a supercritical state to an ordinary gas state by isothermal decompression or isobaric heating, which makes it easy to separate from the extract. There is no residue in the extract after separation, and it is then compressed and cooled and sent back to the extractor for recycling.

[0005] Supercritical CO2 is the most widely used supercritical fluid. CO2 is favored because of its easy availability, safety, stability, non-toxicity, economy, low supercritical point (Tc = 31.1℃ 3Pc = 7.28MPa), and mild operating conditions. Supercritical CO2 has a diffusion coefficient similar to that of gas, a solubility of liquid, and zero surface tension. It can penetrate quickly and effectively separate, extract and purify the extract from the matrix. It has the characteristics of high efficiency, pure natural, not easy to oxidize, good extract quality, reusable extractant, no chemical pollution and three waste emissions (waste gas, waste residue, waste water).

[0006] After searching, there are related patents published on the method of extracting oily sludge using supercritical fluid. For example, the patent application number 201010514047.1 "Method of Ultrasonic Enhanced Supercritical Extraction of Oil Sludge" puts the oil sludge and the extractant into a supercritical extraction device with an enhanced ultrasonic device, sets the supercritical extraction pressure and supercritical extraction temperature, and performs supercritical extraction.

[0007] For example, the patent "A method for treating oil-based mud" with application number 201911289968.X heats the oil-based mud in a heating furnace to form a mixture of oil, mud and water, and then adds the mixture, extractant and co-extractant to a supercritical extraction device for supercritical extraction to obtain dried sludge and extraction phase. The extraction phase is cooled and decompressed in a separator to obtain heavy oil, clear oil and water. The separated water is introduced into a flotation device to remove residual oil in the wastewater to achieve wastewater treatment.

[0008] For another example, the patent application number 201910512276.0, "A method and device for recovering crude oil from oily sludge", mixes oily sludge with liquid carbon dioxide to form a mixture, converts the carbon dioxide in the mixture into a supercritical fluid, puts the mixture containing supercritical fluid carbon dioxide into a reactor, and extracts crude oil from the oily sludge. This method has a high raw material utilization rate. The formed sludge-dry ice particles are squeezed several times, and the oily sludge and liquid carbon dioxide can be mixed evenly. The pores inside the particles increase, and the specific surface area increases, which helps to improve the extraction rate.

[0009] The above three applications all strengthen and improve the conventional supercritical extraction method, such as through ultrasonic treatment, addition of co-extraction agents, microwave and vibration treatment, etc. Although the extraction efficiency can be improved to a certain extent, the above schemes still have shortcomings such as long extraction time and high requirements for extraction pressure and temperature, which ultimately lead to relatively low extraction efficiency. Summary of the invention

[0010] 1. Problem to be solved

[0011] The purpose of the present invention is to provide a method for supercritical extraction of hot-rolled oil sludge by CO2 enhanced by waste alkali liquor, so as to solve the problems of long extraction time and low extraction efficiency in treating oil sludge by using existing supercritical extraction technology. The technical solution of the present invention adopts the method of adding cold-rolled waste alkali liquor to hot-rolled oil sludge to enhance supercritical extraction, and can realize the coordinated treatment of waste alkali liquor and the fixed reduction and productization of CO2.

[0012] 2. Technical solution

[0013] In order to solve the above problems, the technical solution adopted by the present invention is as follows:

[0014] The method of the present invention for extracting hot rolling sludge by using waste alkali solution enhanced with CO2 supercritical CO2 specifically comprises the following steps:

[0015] Step 1, mixing and stirring the hot rolling sludge after being piled and drained with the waste alkali solution to obtain a muddy water mixture of the hot rolling sludge and the waste alkali solution;

[0016] Step 2: The hot rolling sludge and the mud-water mixture of the waste alkali liquor enter into a CO2 supercritical extraction device for supercritical extraction, the oil phase is extracted and separated from the mud-water phase, the waste alkali liquor is gradually neutralized, and the extraction phase and the residue (mud-water mixture) are obtained;

[0017] Step 3: After extraction, the extract phase enters the separator, the extractant is separated from the extract by cooling and reducing pressure, CO2 is gasified and enters the storage tank for recycling, and the precipitated oil is collected and can be used internally as fuel or sent to chemical enterprises for processing;

[0018] Step 4: The residue after removing the oil is subjected to solid-liquid separation treatment, and the obtained dry iron powder has an extremely low oil content, which is returned to the sintering or steelmaking process for internal use, and the obtained concentrated brine enters the next treatment step;

[0019] Step 5: After the concentrated brine is ultrafiltered to remove colloids, suspended particles, chromaticity and macromolecular organic matter, the produced water enters the concentration system for concentration. After concentration, the produced water is evaporated and crystallized to obtain a mixed salt of Na2CO3 and NaHCO3, which is then further dried and dehydrated to finally obtain the Na2CO3 product.

[0020] The present invention adds waste alkali liquor strengthening on the basis of CO2 supercritical extraction. The waste alkali liquor can be cold rolling waste alkali liquor, which is a waste liquor obtained by surface cleaning of the strip steel before entering the annealing furnace in order to remove rolling oil and iron powder adhered to the surface of the cold-rolled strip steel to improve the cleanliness of the strip steel surface. The waste liquor mainly contains about 3wt% NaOH, 200-1000mg / L oil, a small amount of iron powder and a surfactant, while the water treatment process of the traditional cold rolling waste alkali liquor is adjustment and neutralization-reaction clarification-biochemical treatment-filtration-standard discharge. The present invention can make full use of the active ingredients in the cold rolling waste alkali liquor by adding waste alkali liquor to the oil-containing hot rolling mud, and treat waste with waste, thereby replacing the pH adjustment and oil removal process of the conventional water treatment of the original waste alkali liquor, saving the cost of water treatment agents and energy consumption, and realizing the coordinated treatment of the waste alkali liquor; this treatment method does not rely on expensive conventional cleaning agents, and also saves the cost of cleaning agents. At the same time, the method of the present invention has a good oil removal effect on hot rolling sludge. The treated hot rolling sludge has a low oil content, stable composition, and no extractant residue, and can be directly returned to production for utilization, which not only reduces the huge waste of high-quality ferrous resources in hot rolling sludge, but also reduces the waste of high-quality ferrous resources in waste alkali liquid, saving high disposal costs for enterprises.

[0021] As a further optimization of the present invention, the water content of the hot rolling sludge raw material used is ≤10wt%, the oil content is 1-10wt%, and the solid-liquid mass ratio of the hot rolling sludge to the waste alkali liquid is 1:1-1:4. More optimized, the stirring time of the hot rolling sludge and the waste alkali liquid is 30-120s, the stirring speed is 50-200r / min, and the stirring temperature is 20-80°C. The present invention utilizes the active ingredients NaOH and surfactants in the waste alkali liquid to produce saponification on the oil film coated on the surface of the fine iron scale, and enhances the wetting and penetration ability of the liquid, greatly reduces the interfacial tension between the oil and water phases, can effectively destroy the stable oil-water-solid structure between the fine iron scale particles, accelerate the stripping and dissolution of the oil film coated on the surface of the fine iron scale, and improve the mass transfer capacity of the oil between the phases, thereby reducing the difficulty of supercritical extraction, improving the extraction efficiency, and achieving a better degreasing and oil removal effect. In addition, by optimizing the mixing mass ratio of hot-rolled sludge and waste alkali solution, stirring temperature and duration, the stable oil-water-solid structure between fine iron scale particles can be further broken, and the oil film coating on the surface of fine iron scale can be accelerated to be peeled off and dissolved into the water phase, thereby further improving the degreasing and oil removal effect.

[0022] As a further optimization of the present invention, in step 2, the mass ratio of hot rolling sludge to supercritical CO2 extractant is 1:1-1:10, and more optimally, the supercritical extraction pressure is 8-15MPa, the supercritical extraction temperature is 35-80°C, and the supercritical extraction time is 40-110min. The hot rolling sludge treatment method of the present invention can effectively reduce the difficulty of subsequent supercritical extraction after being strengthened by waste alkali solution, the temperature conditions of the whole operation process are mild, the energy consumption is low, CO2 is stable, easy to obtain, economical, non-toxic and harmless, and can be recycled, and the treatment process has no three wastes (waste gas, waste residue, waste water), no secondary pollution, safety and environmental protection, and has more advantages than traditional chemical extraction, and the waste alkali solution is neutralized to generate Na2CO3 and NaHCO3 as another degreasing agent, which also plays a role in strengthening grease removal, and significantly improves the degreasing and degreasing effect of hot rolling sludge.

[0023] As a further optimization of the present invention, CO2 supercritical extraction is a continuous or intermittent operation.

[0024] As a further optimization of the present invention, in step three, the separation pressure during separation of the extraction phase is 4-6 MPa, and the separation temperature is 30-50°C.

[0025] As a further optimization of the present invention, in step four, the solid-liquid separation treatment method includes gravity sedimentation, centrifugal separation, filter press separation, etc.

[0026] As a further optimization of the present invention, the SDI value of the ultrafiltration water is less than 5, the brine concentration can be carried out by reverse osmosis membrane concentration or electrodialysis concentration, the salt content of the concentrated water is greater than 10wt%, and the evaporation crystallization can be carried out by MED, MVR, spray drying and the like. The purity of the Na2CO3 product is ≥98wt%. The hot-rolled sludge treatment method of the present invention is different from the conventional CO2 supercritical extraction technology. The conventional CO2 supercritical extraction only captures and utilizes CO2, and the total amount of CO2 is not reduced. The present invention allows part of the CO2 to participate in the reaction as a neutralizer and finally obtains a Na2CO3 carbon fixation product, thereby achieving a fixed reduction in CO2, contributing to the realization of the "dual carbon" goal, and truly realizing the reduced utilization of CO2.

[0027] 3. Beneficial effects

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] (1) The present invention discloses a method for supercritical CO2 extraction of hot rolling sludge by using waste alkali liquor. On the basis of supercritical extraction, the active components (NaOH, surfactant, etc.) in the waste alkali liquor of cold rolling are used to clean and strengthen the hot rolling sludge, so as to treat waste with waste, enhance the stripping and dissolving ability of the oil film coated on the surface of fine iron scale, accelerate the separation of oil and solid phases, thereby reducing the difficulty of supercritical extraction, improving the extraction efficiency, and enhancing the degreasing and oil removal effect; the remaining components in the waste alkali liquor are similar to the hot rolling sludge, and no other substances are introduced, so the method has good adaptability;

[0030] (2) A method of extracting hot-rolled oil sludge by supercritical CO2 with waste alkali liquor of the present invention uses supercritical CO2 as both a neutralizing agent and an extracting agent to replace the pH adjustment and oil removal process of the waste alkali liquor in the original conventional water treatment, thereby achieving the coordinated treatment of the waste alkali liquor;

[0031] (3) The method of the present invention is a method for extracting hot-rolled oil sludge by supercritical CO2 with waste alkali liquid, which uses part of the supercritical CO2 to neutralize the waste alkali liquid to generate Na2CO3 and NaHCO3. On the one hand, it serves as another degreasing agent and also plays a role in accelerating the removal of oil and fat, thereby improving the extraction effect. On the other hand, after a complete treatment process, a Na2CO3 carbon fixation product is finally obtained, which truly realizes the reduced utilization of CO2 compared to the use of supercritical CO2 simply as an extraction agent. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a schematic diagram of the overall process of a method for extracting hot-rolled oil sludge by using waste alkali solution enhanced with CO2 supercritical CO2 according to the present invention;

[0033] Figure 2 These are the performance indicators of the oil-containing hot-rolled sludge before and after squeezing and drying in each embodiment of the present invention. DETAILED DESCRIPTION

[0034] The present invention is further described below in conjunction with specific embodiments.

[0035] Example 1

[0036] like Figure 1 As shown, the method of waste alkali solution enhanced CO2 supercritical extraction of hot rolling sludge in this embodiment comprises the following steps:

[0037] Step 1: Mix and stir the hot-rolled sludge with a water content of 5wt% and an oil content of 2wt% after being piled and drained, with the solid-liquid mass ratio of the sludge to the waste alkali liquid being 1:1, with a stirring time of 30s, a stirring speed of 50r / min, and a stirring temperature of 20°C to obtain a muddy-water mixture of the hot-rolled sludge and the waste alkali liquid;

[0038] Step 2: The hot rolling sludge and the mud-water mixture of the waste alkali liquor enter into a CO2 supercritical extraction device for supercritical extraction, the mass ratio of the sludge to the supercritical CO2 extractant is 1:1, the supercritical extraction pressure is 8MPa, the supercritical extraction temperature is 35°C, the supercritical extraction time is 40min, the oil phase is extracted and separated from the mud-water phase, the waste alkali liquor is gradually neutralized, and the extraction phase and the mud-water mixture (extract residue) are obtained;

[0039] Step 3: After extraction, the extract phase enters the separator, and the extractant is separated from the extract by cooling and reducing pressure. The separation pressure is 4MPa and the separation temperature is 30℃. CO2 is gasified and enters the storage tank for recycling. The precipitated oil is collected and used internally as fuel or sent to chemical enterprises for processing.

[0040] Step 4: The residue from which the oil is removed in step 2 is centrifuged to obtain dry iron powder with extremely low oil content, which is returned to the sintering or steelmaking process for internal use, and the concentrated brine obtained enters the next treatment step;

[0041] Step 5: The concentrated brine is ultrafiltered to remove colloids, suspended particles, chromaticity and macromolecular organic matter, and the SDI value of the produced water is 3. It enters the electrodialysis system for concentration. After concentration, the salt content of the produced water reaches 10wt%, and then MVR evaporation and crystallization are performed to obtain a mixed salt of Na2CO3 and NaHCO3, and then further dried and dehydrated to finally obtain the Na2CO3 product;

[0042] The dry iron mud and Na2CO3 product obtained by the above treatment were tested, and the results of the oil content of the dry iron mud and the purity of the Na2CO3 product are shown in Table 2.

[0043] Example 2

[0044] like Figure 1 As shown, the method of waste alkali solution enhanced CO2 supercritical extraction of hot rolling sludge in this embodiment comprises the following steps:

[0045] Step 1: Mix and stir the hot rolling sludge with a water content of 5wt% and an oil content of 6wt% after being piled and drained, with the solid-liquid mass ratio of the sludge to the waste alkali liquid being 1:2.5, the stirring time being 75s, the stirring speed being 125r / min, and the stirring temperature being 50°C, to obtain a muddy-water mixture of the hot rolling sludge and the waste alkali liquid;

[0046] Step 2: The hot rolling sludge and the mud-water mixture of the waste alkali liquor enter into a CO2 supercritical extraction device for supercritical extraction, the mass ratio of the sludge to the supercritical CO2 extractant is 1:5, the supercritical extraction pressure is 11.5MPa, the supercritical extraction temperature is 57.5°C, the supercritical extraction time is 80min, the oil phase is extracted and separated from the mud-water phase, the waste alkali liquor is gradually neutralized, and the extraction phase and the mud-water mixture (extract residue) are obtained;

[0047] Step 3: After extraction, the extract phase enters the separator, and the extractant is separated from the extract by cooling and reducing pressure. The separation pressure is 5MPa and the separation temperature is 40℃. CO2 is gasified and enters the storage tank for recycling. The precipitated oil is collected and used internally as fuel, or enters the chemical enterprise for processing;

[0048] Step 4: The residue from which the oil is removed in step 2 is centrifuged to obtain dry iron powder with extremely low oil content, which is returned to the sintering or steelmaking process for internal use, and the concentrated brine obtained enters the next treatment step;

[0049] Step 5: The concentrated brine is ultrafiltered to remove colloids, suspended particles, chromaticity and macromolecular organic matter, and the SDI value of the produced water is 4. It enters the electrodialysis system for concentration. After concentration, the salt content of the produced water reaches 15wt%, and then MVR evaporation and crystallization are performed to obtain a mixed salt of Na2CO3 and NaHCO3, and then further dried and dehydrated to finally obtain the Na2CO3 product;

[0050] The dry iron mud and Na2CO3 product obtained by the above treatment were tested, and the results of the oil content of the dry iron mud and the purity of the Na2CO3 product are shown in Table 2.

[0051] Example 3

[0052] like Figure 1 As shown, the method of waste alkali solution enhanced CO2 supercritical extraction of hot rolling sludge in this embodiment comprises the following steps:

[0053] Step 1: Mix and stir the hot-rolled sludge with a moisture content of 5wt% and an oil content of 10wt% after being piled and drained, with the solid-liquid mass ratio of the sludge to the waste alkali liquid being 1:4, the stirring time being 120s, the stirring speed being 200r / min, and the stirring temperature being 80°C, to obtain a muddy-water mixture of the hot-rolled sludge and the waste alkali liquid;

[0054] Step 2: The hot rolling sludge and the mud-water mixture of the waste alkali liquor enter into a CO2 supercritical extraction device for supercritical extraction, the mass ratio of the sludge to the supercritical CO2 extractant is 1:10, the supercritical extraction pressure is 15MPa, the supercritical extraction temperature is 80°C, the supercritical extraction time is 110min, the oil phase is extracted and separated from the mud-water phase, the waste alkali liquor is gradually neutralized, and the extraction phase and the mud-water mixture (extract residue) are obtained;

[0055] Step 3: After extraction, the extract phase enters the separator, and the extractant is separated from the extract by cooling and reducing pressure. The separation pressure is 6MPa and the separation temperature is 50℃. CO2 is gasified and enters the storage tank for recycling. The precipitated oil is collected and used internally as fuel or sent to chemical enterprises for processing.

[0056] Step 4: The residue from which the oil is removed in step 2 is centrifuged to obtain dry iron powder with extremely low oil content, which is returned to the sintering or steelmaking process for internal use, and the concentrated brine obtained enters the next treatment step;

[0057] Step 5: The concentrated brine is ultrafiltered to remove colloids, suspended particles, chromaticity and macromolecular organic matter, and the SDI value of the produced water is 3. It enters the electrodialysis system for concentration. After concentration, the salt content of the produced water reaches 20wt%, and then MVR evaporation and crystallization are performed to obtain a mixed salt of Na2CO3 and NaHCO3, and then further dried and dehydrated to finally obtain the Na2CO3 product;

[0058] The dry iron mud and Na2CO3 product obtained by the above treatment were tested, and the results of the oil content of the dry iron mud and the purity of the Na2CO3 product are shown in Table 2.

[0059] Comparative Example 1

[0060] The method for CO2 supercritical extraction of hot-rolled oil sludge in this comparative example has the same main processing steps as Example 1. The main difference between it and Example 1 is that no waste alkali solution is added, and the other process parameters are the same as Example 1.

[0061] The dry mud obtained by the above treatment was tested and the results of the oil content of the dry iron mud were measured and shown in Table 2.

[0062] Comparative Example 2

[0063] The method of CO2 supercritical extraction of hot-rolled oil sludge in this comparative example has the same main processing steps as Example 1, and the main difference between it and Example 1 is that no waste alkali solution is added, and during extraction, the supercritical extraction pressure is controlled to be 18MPa, the supercritical extraction temperature is 55°C, and the supercritical extraction time is 120min.

[0064] The dry mud obtained by the above treatment was tested and the results of the oil content of the dry iron mud were measured and shown in Table 2.

[0065] Comparative Example 3

[0066] The method for CO2 supercritical extraction of hot-rolled sludge in this comparative example has the same main processing steps as Example 1. The main difference between it and Example 1 is that the solid-liquid mass ratio of the added sludge to the waste alkali liquid is 1:0.5, and the other process parameters are the same as Example 1.

[0067] The dry mud obtained by the above treatment was tested, and the results of the oil content of the dry iron mud and the purity of the Na2CO3 product were measured and shown in Table 2.

[0068] The present invention has been described in detail above in conjunction with specific exemplary embodiments. However, it should be understood that various modifications and variations may be made without departing from the scope of the present invention as defined by the appended claims. The detailed description and the accompanying drawings should be considered only as illustrative and not restrictive, and if there are any such modifications and variations, they will fall within the scope of the present invention described herein. In addition, the background technology is intended to illustrate the current status and significance of the research and development of the present technology and is not intended to limit the present invention or the application field of the present application and the present invention.

[0069] More specifically, although exemplary embodiments of the present invention have been described herein, the present invention is not limited to these embodiments, but includes any and all embodiments that are recognizable by those skilled in the art based on the foregoing detailed description, such as combinations between the various embodiments, adaptive changes and / or replacements. The limitations in the claims may be interpreted broadly based on the language used in the claims and are not limited to the examples described in the foregoing detailed description or during the implementation of the application, which examples should be considered non-exclusive. Any steps listed in any method or process claim may be performed in any order and are not limited to the order presented in the claim. Therefore, the scope of the present invention should be determined solely by the attached claims and their legal equivalents, rather than by the description and examples given above.

[0070] Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those of ordinary skill in the art to which the present invention belongs. When there is a conflict, the definition in this specification sheet shall prevail. When rate, pressure, temperature, time or other values ​​or parameters are expressed as ranges, preferred ranges, or a series of upper preferred values ​​and lower preferred values, this should be understood to specifically disclose all ranges formed by any pairing of any upper range limit or preferred value and any lower range limit or preferred value, regardless of whether the range is disclosed separately. For example, a range of 1-50 is understood to include any number, combination of numbers, or subrange selected from 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, or 50, and all decimal values ​​between the above integers, for example, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, and 1.9. With respect to subranges, "nested subranges" extending from any endpoint within the range are specifically contemplated. For example, nested sub-ranges of the exemplary range 1-50 may include 1-10, 1-20, 1-30, and 1-40 in one direction, or 50-40, 50-30, 50-20, and 50-10 in the other direction.

Claims

1. A method for extracting hot rolling sludge by supercritical CO2 with waste alkali liquor, characterized in that: The specific steps include the following: Step 1, mixing and stirring the hot rolling sludge after being piled and drained with the waste alkali solution to obtain a muddy water mixture of the hot rolling sludge and the waste alkali solution; Step 2: The hot rolling sludge and the mud-water mixture of the waste alkali liquor enter into a CO2 supercritical extraction device for supercritical extraction, the oil phase is extracted and separated from the mud-water phase, the waste alkali liquor is gradually neutralized, and an extract phase and a residue are obtained; Step 3: After extraction, the extract phase enters the separator, the extractant is separated from the extract by cooling and reducing pressure, CO2 is gasified and enters the storage tank for recycling, and the precipitated oil is collected; Step 4: performing solid-liquid separation on the residue to obtain dry iron powder and concentrated brine; Step 5: After the concentrated brine is ultrafiltered to remove colloids, suspended particles, chromaticity and macromolecular organic matter, it is concentrated and evaporated to crystallize to obtain a mixed salt of Na2CO3 and NaHCO3, and then further dried and dehydrated to finally obtain the Na2CO3 product.

2. The method for extracting hot rolling sludge by using waste alkali solution enhanced with CO2 supercritical CO2 according to claim 1, characterized in that: In step 1, the solid-liquid mass ratio of the hot rolling sludge to the waste alkali liquid is 1:1 to 1:

4.

3. The method for extracting hot rolling sludge by using waste alkali solution enhanced with CO2 supercritical CO2 according to claim 2, characterized in that: The stirring time of hot rolling sludge and waste alkali solution is 30 to 120 seconds, the stirring speed is 50 to 200 r / min, and the stirring temperature is 20 to 80°C.

4. The method for extracting hot rolling sludge by using waste alkali solution enhanced with CO2 supercritical CO2 according to claim 3, characterized in that: In step 2, the mass ratio of hot-rolled sludge to supercritical CO2 extractant is 1:1 to 1:

10.

5. The method for extracting hot rolling sludge by using waste alkali solution enhanced with CO2 supercritical CO2 according to claim 4, characterized in that: The supercritical extraction pressure is 8-15 MPa, the supercritical extraction temperature is 35-80°C, and the supercritical extraction time is 40-110 min.

6. A method for extracting hot rolling sludge by supercritical CO2 enhanced with waste alkali solution according to any one of claims 1 to 5, characterized in that: CO2 supercritical extraction is a continuous or intermittent operation.

7. A method for extracting hot rolling sludge by supercritical CO2 enhanced with waste alkali solution according to any one of claims 1 to 5, characterized in that: In step 3, the separation pressure during separation of the extraction phase is 4-6 MPa, and the separation temperature is 30-50°C.

8. A method for extracting hot rolling sludge by supercritical CO2 enhanced with waste alkali solution according to any one of claims 1 to 5, characterized in that: In step 4, the solid-liquid separation treatment method includes gravity sedimentation, centrifugal separation, and filter press separation.

9. A method for extracting hot rolling sludge by supercritical CO2 enhanced with waste alkali solution according to any one of claims 1 to 5, characterized in that: In step 1, the water content of the hot-rolled sludge raw material used is ≤10wt% and the oil content is 1-10wt%.

10. A method for extracting hot rolling sludge by supercritical CO2 enhanced by waste alkali solution according to any one of claims 1 to 5, characterized in that: In step 5, the SDI value of the water produced by filtering the concentrated brine is less than 5, the salt content of the water produced after concentration is greater than 10wt%, and the purity of the Na2CO3 product obtained after evaporation and crystallization is ≥98wt%.

Images