A method and system for cleaning of salt-containing wastewater

Abstract

The present application belongs to the technical field of wastewater treatment, and particularly relates to a method and system for clean treatment of salt-containing wastewater. The method comprises: subjecting the wastewater to evaporation crystallization treatment to obtain waste salt and crystallization mother liquor; and subjecting the waste salt or the waste salt and a catalyst to carbonization treatment to obtain carbonized salt. When the soluble COD content of the waste salt is less than 6000 g / t, the carbonization treatment is performed at a carbonization temperature of 400-600 DEG C and a rotation speed of 1-3 rpm. When the soluble COD content of the waste salt is not less than 6000 g / t, the carbonization treatment is performed at a carbonization temperature of 500-600 DEG C in the presence of a catalyst and a rotation speed of 1-1.5 rpm. The method for clean treatment of salt-containing wastewater can produce carbonized salt with significantly reduced COD content and water-soluble color by adjusting the carbonization operation conditions for waste salt with high soluble COD content and waste salt with low soluble COD content, respectively.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment technology, specifically relating to a method and system for the clean treatment of saline wastewater. Background Technology

[0002] Wastewater from industries such as electroplating, smelting, chemicals, and pharmaceuticals has a complex composition, containing not only high salt content but also high levels of COD, ammonia nitrogen, and heavy metals. Conventional treatment methods include wet oxidation, photocatalysis, oxidation, and electroprecipitation. For example, CN113548751A describes a COD removal process for high-salinity wastewater, specifically involving transferring the high-salinity wastewater to a pH-adjusting tank with stirring, adding acid while stirring, feeding the effluent into a Fenton oxidation tank, adding H2O2 and ferrous sulfate and stirring thoroughly, feeding the effluent into an activated carbon adsorption tank, adding powdered activated carbon and stirring thoroughly, feeding the effluent into a concentration tank, adding alkali while stirring, and finally pumping the wastewater into a tubular microfiltration system. Methods such as wet oxidation suffer from problems such as complex equipment, harsh operating conditions, high energy consumption, and secondary pollution.

[0003] The proposed process is "evaporation crystallization + pyrometallurgical smelting." Specifically, wastewater undergoes pretreatment such as coagulation and flocculation, followed by evaporation crystallization to produce waste salt. This waste salt has a high COD (Chemical Oxygen Demand), which is then further treated through pyrometallurgical smelting to produce secondary salt. However, the secondary salt produced by pyrometallurgical smelting still has a high COD content, and direct recycling would generate even more waste.

[0004] In response to this, there is an urgent need in the field for a method and system for the clean treatment of saline wastewater that can effectively reduce the COD content of waste salt recovered from wastewater. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of existing technologies where secondary salts produced by pyrometallurgical processes still have a high COD content, and to provide a method and system for the clean treatment of saline wastewater. This treatment method effectively reduces the COD content of waste salts recovered from wastewater.

[0006] To achieve the above objectives, in a first aspect, the present invention provides a method for cleaning up saline wastewater, the method comprising:

[0007] Wastewater is subjected to evaporation and crystallization treatment to obtain waste salt and crystallization mother liquor;

[0008] The waste salt or the waste salt and catalyst are subjected to carbonization treatment to obtain carbonized salt; the catalyst is a metal sulfate or metal oxide, and the metal sulfate or metal oxide is selected from at least one sulfate or oxide of copper, nickel, iron and zinc.

[0009] Wherein, when the soluble COD content of the waste salt is less than 6000g / t, the conditions for the carbonization treatment include: the carbonization temperature is 400℃~600℃, and the rotation speed of the kiln used for the carbonization treatment is controlled to be 1~3rpm.

[0010] When the soluble COD content of the waste salt is not less than 6000 g / t, the carbonization treatment conditions include: in the presence of a catalyst, the carbonization temperature is 500℃~600℃, and the rotation speed of the kiln used for the carbonization treatment is controlled to be 1~1.5 rpm.

[0011] In some preferred embodiments, when the soluble COD content of the waste salt is less than 6000 g / t and the carbonization treatment is carried out in the presence of a catalyst, the ratio of the amount of catalyst added to the mass of the waste salt is 0.002 to 0.02; and / or, the carbonization treatment conditions further include: a carbonization time of 0.5 to 2 h;

[0012] Preferably, the rotation speed of the kiln used for carbonization is: 1.5 rpm < 3.0 rpm, and the carbonization temperature is: 400℃ ≤ carbonization temperature < 550℃.

[0013] In some preferred embodiments, when the soluble COD content of the waste salt is less than 6000 g / t and the carbonization treatment is carried out in the absence of a catalyst, the rotation speed of the kiln used for the carbonization treatment satisfies: 1 rpm ≤ rotation speed of the kiln used for the carbonization treatment ≤ 1.5 rpm, and the carbonization temperature satisfies: 550℃ ≤ carbonization temperature ≤ 600℃.

[0014] Preferably, the carbonization treatment conditions further include a carbonization time of 1 to 2 hours.

[0015] In some preferred embodiments, when the soluble COD content of the waste salt is not less than 6000 g / t, the ratio of the amount of catalyst added to the mass of the waste salt is 0.01-0.1; and / or, the carbonization treatment conditions further include: a carbonization time of 0.5 to 2 h.

[0016] In some preferred embodiments, the kiln body used for the carbonization process includes a heating section and a non-heating section, wherein the length L of the heating section is... 加热 The ratio of the diameter D of the heating section to the diameter of the heating section is 6 to 15, and / or the horizontal inclination angle of the kiln body is 3 to 5°;

[0017] Preferably, the heating method for the carbonization treatment is external heating of the kiln;

[0018] Preferably, the kiln body is equipped with lifting lifters.

[0019] In some preferred embodiments, the carbonization raw material for the carbonization treatment is the waste salt, or the waste salt and the catalyst, and the water content of the carbonization raw material is ≤5wt%.

[0020] In some preferred embodiments, the processing method further includes:

[0021] After the carbonization treatment, the carbonized salt is subjected to a slurry dissolution treatment to obtain a salt solution;

[0022] The salt solution is subjected to impurity removal treatment to obtain purified salt;

[0023] The salt concentration in the salt solution is 15 wt% to 25 wt%.

[0024] More preferably, when the fluoride concentration of the salt solution is below a threshold, the impurity removal treatment includes removing fluoride ions with an aluminum-based defluorinating agent; when the fluoride concentration of the salt solution is not below the threshold, the impurity removal treatment includes removing fluoride ions with a calcium-based defluorinating agent; the threshold is 25–55 ppm; preferably, when the dry basis sodium chloride content in the waste salt is higher than the dry basis sodium sulfate content, the threshold is 25–35 ppm; when the dry basis sodium sulfate content in the waste salt is higher than the dry basis sodium chloride content, the threshold is 45–55 ppm.

[0025] In a second aspect, the present invention provides a treatment system for the saline wastewater clean treatment method described in the first aspect, the system comprising: an evaporation crystallization module and a carbonization module; the evaporation crystallization module is provided with a wastewater inlet, a waste salt outlet, and a crystallization mother liquor outlet; the carbonization module comprises: a catalyst supply unit and a carbonization unit, the carbonization unit being provided with a waste salt inlet, a catalyst inlet, and a carbonized salt outlet, the waste salt inlet being connected to the waste salt outlet of the evaporation crystallization module, and the catalyst inlet being connected to the catalyst supply unit; and the system further comprises:

[0026] A soluble COD detection unit, which is connected to the evaporation crystallization module or the carbonization unit, is used to detect the soluble COD content of the waste salt.

[0027] The first control unit is connected to the dissolved COD detection unit, the carbonization unit, and the catalyst supply unit, respectively, and is used to perform the following actions: when the dissolved COD content of the waste salt is detected to be less than 6000 g / t, introduce or not introduce the catalyst into the waste salt; when the dissolved COD content of the waste salt is detected to be not less than 6000 g / t, introduce the catalyst into the waste salt.

[0028] In some preferred embodiments, the system further includes a slurry dissolution module and an impurity removal module;

[0029] The slurry dissolution module is equipped with a carbonized salt inlet, a solvent inlet, and a salt solution outlet. The carbonized salt inlet is connected to the carbonized salt outlet of the carbonization unit, and the solvent inlet is used to introduce a solvent for slurry dissolution into the carbonized salt.

[0030] The impurity removal module is provided with a salt solution inlet and a purified salt outlet, and the salt solution inlet and the salt solution outlet are connected.

[0031] Preferably, the impurity removal module includes a salt solution fluoride concentration detection unit, a second control unit, a calcium-based defluorinating agent defluorination unit, and an aluminum-based defluorinating agent defluorination unit;

[0032] The salt solution fluoride concentration detection unit is connected to the salt solution outlet of the slurry dissolution module and is used to obtain the fluoride concentration of the salt solution.

[0033] The second control unit is connected to the fluoride concentration detection unit, the calcium-based defluorinating agent defluorination unit, and the aluminum-based defluorinating agent defluorination unit, respectively, and is used to remove fluoride ions from the salt solution with an aluminum-based defluorinating agent when the fluoride concentration of the salt solution is detected to be lower than a threshold, and to remove fluoride ions from the salt solution with a calcium-based defluorinating agent when the fluoride concentration of the salt solution is detected to be not lower than the threshold.

[0034] This invention separates waste salt and crystallization mother liquor from wastewater through evaporation and crystallization. By carbonizing the waste salt, especially by adjusting the carbonization operation conditions for waste salt with high and low soluble COD content, it is possible to effectively reduce the soluble COD content of the waste salt under lower process conditions (especially lower carbonization temperature). This produces carbonized salt with significantly reduced COD content and aqueous solution color, thus realizing the resource utilization of high-salt, high-COD wastewater.

[0035] This invention targets waste salt with high and low soluble COD content. By adjusting whether to add a catalyst, the carbonization temperature, and the rotation speed of the kiln, it specifically reduces the soluble COD content of the waste salt and the process requirements for carbonization treatment (especially reducing the carbonization temperature).

[0036] The soluble COD content of the carbonized salt of the present invention is not higher than 300 g / t, and the platinum-cobalt color of a 20 wt% carbonized salt aqueous solution is ≤200 degrees. Attached Figure Description

[0037] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0038] Figure 1 This is a process flow diagram of the saline wastewater cleaning treatment method of Embodiment 1 of this application. Detailed Implementation

[0039] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0040] In existing technologies, conventional treatment methods for high-salt, high-COD wastewater include wet oxidation, photocatalysis, oxidation, and electrochemical precipitation. However, these methods suffer from problems such as complex equipment, harsh operating conditions, high energy consumption, and secondary pollution. The "evaporation crystallization + pyrometallurgical smelting" process has been proposed. However, the secondary salt produced by pyrometallurgical smelting still has a high COD content. If it is directly recycled and treated, more waste will be generated.

[0041] In this regard, firstly, the present invention provides a method for cleaning and treating saline wastewater, the method comprising: evaporating and crystallizing the wastewater to obtain waste salt and crystallization mother liquor;

[0042] The waste salt or the waste salt and catalyst are subjected to carbonization treatment to obtain carbonized salt; the catalyst is a metal sulfate or metal oxide, and the metal sulfate or metal oxide is selected from at least one sulfate or oxide of copper, nickel, iron and zinc.

[0043] Wherein, when the soluble COD content of the waste salt is less than 6000g / t, the conditions for the carbonization treatment include: the carbonization temperature is 400℃~600℃, and the rotation speed of the kiln used for the carbonization treatment is controlled to be 1~3rpm.

[0044] When the soluble COD content of the waste salt is not less than 6000 g / t, the carbonization treatment conditions include: in the presence of a catalyst, the carbonization temperature is 500℃~600℃, and the rotation speed of the kiln used for the carbonization treatment is controlled to be 1~1.5 rpm.

[0045] This invention proposes to reduce the soluble COD content of waste salt through carbonization treatment. Furthermore, for low COD waste salt with a soluble COD content of less than 6000 g / t and high COD waste salt with a soluble COD content of not less than 6000 g / t, carbonization treatment conditions are set respectively, including whether to add a catalyst, carbonization temperature, and kiln rotation speed. Specifically, for low-COD waste salt, the specific carbonization treatment conditions include a carbonization temperature of 400℃~600℃ and a kiln rotation speed of 1~3 rpm. A catalyst may or may not be introduced. If the kiln rotation speed is below 1 rpm, uneven temperature distribution within the kiln is likely, and salt melting and ring formation may occur. If the kiln rotation speed is above 3 rpm, the material residence time within the kiln is insufficient, resulting in low COD decomposition efficiency. If the carbonization temperature is below 400℃, the reaction temperature is too low, leading to low COD decomposition efficiency. If the carbonization temperature is above 600℃, the kiln temperature is likely to be too high, causing localized melting and adhesion of salt to the kiln heating cylinder wall, forming rings and affecting the normal operation of the equipment. Carbonization treatment under the above conditions can significantly reduce the soluble COD content of the waste salt. For high-COD waste salt, specific carbonization conditions include introducing at least one catalyst from sulfates or oxides of copper, nickel, iron, and zinc into the waste salt; carbonization temperature of 500℃~600℃; and kiln rotation speed of 1~1.5rpm. Without a catalyst, COD decomposition efficiency can be guaranteed, but due to the high absolute COD content in the kiln, the residual COD in the carbonized salt is high, which is detrimental to the quality of subsequent product salt. If a catalyst is used, but the kiln rotation speed is less than 1rpm, uneven temperature within the kiln can easily occur, and even salt melting and ring formation. If a catalyst is used, but the kiln rotation speed is greater than 1.5rpm, insufficient residence time and reaction time result in low carbonization efficiency, failing to guarantee the quality of subsequent product salt. If a catalyst is used and the rotation speed is controlled at 1~1.5rpm, but the carbonization temperature is less than 500℃, the carbonization efficiency is low, failing to guarantee the quality of subsequent product salt. If the carbonization temperature is greater than 600℃, excessively high kiln temperature can easily occur, causing localized melting and adhesion of salt to the kiln heating cylinder wall, forming rings and affecting the normal operation of the equipment. By using a catalyst, the temperature requirements for carbonization are reduced, and carbonization is carried out under the aforementioned conditions, significantly reducing the soluble COD content of waste salt. Regardless of whether the waste salt has high or low COD, the soluble COD content of the carbonized salt produced by this invention is no higher than 300 g / t, and the platinum-cobalt color of a 20 wt% carbonized salt aqueous solution is ≤200 degrees.

[0046] This invention, by adjusting the carbonization operating conditions for waste salt with high soluble COD content and waste salt with low soluble COD content respectively, can produce carbonized salt with significantly reduced COD content and aqueous solution color, thus realizing the resource utilization of high-salt, high-COD wastewater.

[0047] The treatment method of the present invention can be applied to wastewater with complex composition generated in industries such as electroplating, metallurgy, chemical industry, and pharmaceutical industry. It is particularly suitable for wastewater with high salt and high COD content. The treatment method allows the wastewater to contain heavy metals, calcium and magnesium, ammonia nitrogen, fluorine, etc.

[0048] For wastewater containing heavy metals, calcium, magnesium, ammonia nitrogen, and fluoride, in order to reduce process costs and ensure the quality of the treated salt products, preferably, the wastewater is pretreated before evaporation and crystallization. This pretreatment involves adjusting the pH of the wastewater to remove heavy metals and magnesium, using carbonates such as sodium carbonate to remove calcium and magnesium, and removing ammonia nitrogen through ammonia stripping to obtain saline water, ammonia water, and impurity-free residue. The saline water is then subjected to evaporation and crystallization and carbonization treatment. More preferably, the total calcium and magnesium content in the saline water is controlled to be ≤100ppm through calcium and magnesium removal, and the ammonia nitrogen content in the saline water is controlled to be ≤30ppm through ammonia stripping. Preferably, the processing method further includes: after carbonization, subjecting the carbonized salt to slurry dissolution treatment to obtain a salt solution and optional carbonized slag; subjecting the salt solution to impurity removal treatment to obtain purified salt; more preferably, the impurity removal treatment includes removing heavy metals, magnesium, and fluorine to obtain impurity-removed slag and purified liquid; subjecting the purified liquid to secondary evaporation and crystallization treatment to obtain the purified salt and secondary crystallization mother liquor; and returning the secondary crystallization mother liquor to the secondary evaporation and crystallization unit for secondary evaporation and crystallization treatment, with or without adsorption treatment; more preferably, when the color value of the secondary crystallization mother liquor is below 100, the secondary crystallization mother liquor is directly returned to the secondary evaporation and crystallization unit for secondary evaporation and crystallization treatment; when it is not below 100, it is adsorbed using activated carbon, decolorizing resin, etc., and then returned to the secondary evaporation and crystallization unit, with the activated carbon being regenerated through inert carbonization. As the secondary evaporation and crystallization process proceeds, the COD content and color of the secondary crystallization mother liquor increase, which affects the quality of the evaporated product. Therefore, it is necessary to adsorb and decolorize it using activated carbon, decolorizing resin, etc., to reduce its color value to below 100 before returning it to the secondary evaporation and crystallization unit for further evaporation.

[0049] More preferably, the salt concentration in the salt solution is 15wt% to 25wt%. A salt concentration below 25wt% can further reduce the difficulty of the impurity removal process, while a salt concentration above 15wt% can further reduce the cost of obtaining purified salt after the impurity removal process.

[0050] Further preferably, the impurity removal treatment includes removing fluoride ions with an aluminum-based defluorinating agent when the fluoride concentration of the salt solution is below a threshold, and removing fluoride ions, heavy metals, and magnesium with a calcium-based defluorinating agent when the fluoride concentration of the salt solution is not below the threshold. More preferably, the threshold is 25-55 ppm. Optionally, the aluminum-based defluorinating agent can be aluminum sulfate, etc., and the calcium-based defluorinating agent can be calcium chloride, etc.

[0051] The treatment method of this invention is particularly suitable for wastewater in which the salt is mainly sodium chloride or sodium sulfate. When the dry basis sodium chloride content in the waste salt obtained by evaporation and crystallization is higher than the dry basis sodium sulfate content, the corresponding fluoride concentration threshold is 25-35 ppm; when the dry basis sodium sulfate content in the waste salt obtained by evaporation and crystallization is higher than the dry basis sodium chloride content, the corresponding fluoride concentration threshold is 45-55 ppm. For waste salt mainly composed of sodium chloride, when the fluoride concentration of the salt solution is not lower than 25-35 ppm, calcium-based defluorinating agents are used to remove fluoride ions, heavy metals, and magnesium; when the fluoride concentration is lower than 25-35 ppm, aluminum-based defluorinating agents are used to remove fluoride ions. For waste salt mainly composed of sodium sulfate, when the fluoride concentration of the salt solution is not lower than 45-55 ppm, calcium-based defluorinating agents are used to remove fluoride ions, heavy metals, and magnesium; when the fluoride concentration is lower than 45-55 ppm, aluminum-based defluorinating agents are used to remove fluoride ions. This method can further reduce the amount of defluorinating agent used and reduce treatment costs.

[0052] The carbonization process of the present invention is preferably carried out in a carbonization kiln. In some preferred embodiments, the kiln used for the carbonization process includes a heating section and a non-heating section.

[0053] Preferably, the length L of the heating section 加热 The ratio of the diameter D of the heating section to the diameter of the heating section is 6 to 15, which is more conducive to keeping the material in a more stable heating range during carbonization. Combined with the preferred rotation speed range, the material is heated more evenly, decomposes more stably, and has a more efficient heat utilization rate.

[0054] Preferably, the heating method for the carbonization process is external heating of the kiln body. This invention offers a wide range of options for the heating method of the carbonization kiln body, including natural gas heating, resistance wire heating, etc.

[0055] Preferably, the horizontal tilt angle of the kiln body is 3 to 5°, which is more conducive to the forward turning of materials. Combined with the preferred rotation speed range, the materials crawl in an orderly manner during the carbonization process, reducing stickiness and agglomeration.

[0056] Preferably, the kiln body is equipped with lifting lifters. By using lifting lifters, the waste salt can be heated more evenly and stably during the carbonization process, ensuring continuous and effective decomposition of organic matter, while reducing the adhesion phenomenon of the waste salt rings caused by non-high temperature conditions.

[0057] Preferably, the kiln used for the carbonization process includes a secondary combustion chamber to reduce dioxins in the carbonization process exhaust gas.

[0058] The soluble COD content of waste salt in this invention refers to the amount of reducing substances in the sample that need to be oxidized, measured by chemical methods.

[0059] In this invention, when the soluble COD content of the waste salt is less than 6000 g / t, the carbonization treatment can be carried out in the presence of a catalyst or not in the presence of a catalyst.

[0060] In some preferred embodiments, when the soluble COD content of the waste salt is less than 6000 g / t, the carbonization treatment is carried out in the presence of a catalyst. Further, the ratio of the catalyst addition to the mass of the waste salt is preferably 0.002-0.2, the carbonization time is controlled to be 0.5-2 h, and the rotation speed of the kiln used for carbonization is controlled to meet the following conditions: 1.5 rpm < 3.0 rpm, and the carbonization temperature is controlled to meet the following conditions: 400℃ ≤ carbonization temperature < 550℃. The ratio of the catalyst addition to the mass of the waste salt in this invention is higher than 0.002, which can further reduce the soluble COD content of the waste salt; the ratio is lower than 0.2, which can reduce costs while ensuring effective reduction of the soluble COD content. Controlling the carbonization time to 0.5-2 h is beneficial for further decomposing the organic matter in the waste salt by heat, thereby reducing the COD content of the waste salt. Under optimal conditions, controlling the kiln rotation speed to 1.5–3.0 rpm facilitates efficient material carbonization and increases unit output. Controlling the carbonization temperature to 400℃–550℃ further improves the COD decomposition rate, prevents localized salt melting and ring formation, and minimizes energy consumption. Under these carbonization conditions, the carbonization temperature can be minimized while the kiln rotation speed can be maximized, thereby reducing the process requirements for carbonization and lowering the soluble COD content of the waste salt.

[0061] In some preferred embodiments, when the soluble COD content of the waste salt is below 6000 g / t, the carbonization treatment is carried out in the absence of a catalyst. Further, the carbonization time is controlled to be 1-2 hours, the rotation speed of the kiln used for carbonization is controlled to be 1 rpm ≤ 1.5 rpm, and the carbonization temperature is controlled to be 550℃ ≤ 600℃. Controlling the carbonization time to 1-2 hours is beneficial for further decomposing the organic matter in the waste salt by heat, thus reducing the COD content. Controlling the kiln rotation speed to 1-1.5 rpm is beneficial for further improving COD decomposition efficiency and ensuring more complete COD decomposition. Controlling the carbonization temperature to 550℃-600℃ is beneficial for further promoting COD decomposition, providing a higher COD decomposition rate. Simultaneously, combined with a specific kiln structure and optimized rotation speed, the material is heated more uniformly, reducing localized high temperatures and preventing salt melting and ring formation. Under the above carbonization treatment conditions, the soluble COD content of the waste salt can be reduced to the maximum extent.

[0062] In some preferred embodiments, when the soluble COD content of the waste salt is not less than 6000 g / t, the ratio of the amount of catalyst added to the mass of the waste salt is 0.01-0.1, and / or the carbonization time of the carbonization treatment is controlled to be 0.5-2 h. When the ratio of the amount of catalyst added to the mass of the waste salt is higher than 0.01, it can further reduce the soluble COD content of the waste salt, lower the carbonization temperature, and increase the kiln rotation speed. When the ratio of the amount of catalyst added to the mass of the waste salt is lower than 0.1, it can reduce reagent costs and reduce the content of impurities in the carbonized salt while ensuring an effective reduction in the soluble COD content. Controlling the carbonization time to 0.5-2 h is beneficial for further decomposing the organic matter in the waste salt by heat, thus reducing the COD content of the waste salt. Under the above carbonization treatment conditions, the carbonization temperature can be minimized and the kiln rotation speed can be increased to the maximum extent, thereby reducing the process requirements of the carbonization treatment and reducing the soluble COD content of the waste salt.

[0063] In this invention, during the carbonization process, when a catalyst is added as a carbonization raw material, the carbonized salt may contain one or more of the following ions: copper, nickel, iron, and zinc. These ions are preferably removed by sulfide precipitation. When the amount of catalyst added is low, the residual metal ions in the salt solution will not be high, and can be removed to a low level through subsequent impurity removal treatment. When the amount of catalyst added is high, the metal ion content in the salt solution is relatively high, and it is preferable to use sulfide precipitation to remove the metal ions introduced by the catalyst, followed by impurity removal treatment.

[0064] In some preferred embodiments, the catalyst used in the carbonization treatment of the present invention is copper sulfate or oxide, which not only reduces the carbonization time of waste salt but also decomposes a large amount of COD in the waste salt, resulting in a low residual rate. When the catalyst is copper sulfate, when the COD content is below 6000 g / t, the ratio of catalyst addition to waste salt mass is preferably 0.002 to 0.01, the carbonization temperature is preferably 400℃ to 550℃, the rotation speed of the kiln used for carbonization treatment is preferably 2.0 to 3.0 rpm, and the carbonization time is preferably 0.5 h to 2 h. When the COD content is above 6000 g / t, the ratio of catalyst addition to waste salt mass is preferably 0.01 to 0.1, the carbonization temperature is preferably 500℃ to 600℃, the rotation speed of the kiln used for carbonization treatment is preferably 1.0 to 1.5 rpm, and the carbonization time is preferably 0.5 h to 2 h. When the catalyst is copper oxide, and the COD content is below 6000 g / t, the preferred ratio of catalyst addition to waste salt mass is 0.005–0.015, the preferred carbonization temperature is 400℃–550℃, the preferred kiln rotation speed is 1.5–3.0 rpm, and the preferred carbonization time is 0.5 h–2 h. When the COD content is above 6000 g / t, the preferred ratio of catalyst addition to waste salt mass is 0.015–0.1, the preferred carbonization temperature is 500℃–600℃, the preferred kiln rotation speed is 1.0–1.5 rpm, and the preferred carbonization time is 0.5 h–2 h.

[0065] In this invention, when metal sulfate is used as a catalyst for carbonization, the preferred method of adding the catalyst is to prepare a salt solution of the metal sulfate. In some preferred embodiments, in order to avoid the agglomeration of waste salt during the carbonization process, when waste salt or waste salt and catalyst are used as carbonization raw materials, the water content of the carbonization raw materials is ≤5wt%.

[0066] Secondly, the present invention provides a treatment system for the saline wastewater clean treatment method described in the first aspect, the system comprising: an evaporation crystallization module and a carbonization module. The evaporation crystallization module is provided with a wastewater inlet, a waste salt outlet, and a crystallization mother liquor outlet. The carbonization module includes a catalyst supply unit, a carbonization unit, a dissolved COD detection unit, and a first control unit. Further, the carbonization unit is provided with a waste salt inlet, a catalyst inlet, and a carbonized salt outlet; the waste salt inlet is connected to the waste salt outlet of the evaporation crystallization module, and the catalyst inlet is connected to the catalyst supply unit; the dissolved COD detection unit is connected to the evaporation crystallization module or the carbonization unit, and is used to detect the dissolved COD content of the waste salt; the first control unit is connected to the dissolved COD detection unit, the carbonization unit, and the catalyst supply unit respectively, and is used to perform the following actions: when the dissolved COD content of the waste salt is detected to be lower than 6000 g / t, introduce or not introduce the catalyst into the waste salt; when the dissolved COD content of the waste salt is detected to be not lower than 6000 g / t, introduce the catalyst into the waste salt.

[0067] It should be noted that the carbonization unit includes a carbonization kiln body and a drive mechanism for driving the carbonization kiln body to rotate.

[0068] In some preferred embodiments, the carbonization unit is provided with a secondary combustion chamber as a tail gas treatment unit, which can reduce the formation of dioxins for high COD waste salt.

[0069] In some preferred embodiments, the system further includes a pretreatment module, which is provided with a saline wastewater inlet, a saline water outlet, an ammonia water outlet, and a residue removal outlet, wherein the saline water outlet is connected to the wastewater inlet of the evaporation and crystallization module.

[0070] In some preferred embodiments, the system further includes a slurry dissolution module and a purification module. The slurry dissolution module has a carbonized salt inlet, a solvent inlet, and a salt solution outlet. The carbonized salt inlet is connected to the carbonized salt outlet of the carbonization unit, and the solvent inlet is used to introduce a solvent for slurry dissolution into the carbonized salt. The purification module has a salt solution inlet and a purified salt outlet, and the salt solution inlet is connected to the salt solution outlet.

[0071] In some preferred embodiments, the impurity removal module includes an impurity removal unit, a secondary evaporation and crystallization unit, and a secondary crystallization mother liquor adsorption unit. The impurity removal unit is provided with a salt solution inlet, an impurity removal residue outlet, and a purified liquid outlet. The salt solution inlet is connected to the salt solution outlet. The secondary evaporation and crystallization unit is provided with a purified liquid inlet, a purified salt outlet, and a secondary crystallization mother liquor outlet. The purified liquid inlet is connected to the purified liquid outlet.

[0072] In some preferred embodiments, the secondary evaporation crystallization unit is further provided with a circulating crystallization mother liquor inlet, which is connected to the secondary crystallization mother liquor outlet of the secondary evaporation crystallization unit. Optionally, a secondary crystallization mother liquor adsorption unit is provided between the secondary crystallization mother liquor outlet of the secondary evaporation crystallization unit and the circulating crystallization mother liquor inlet.

[0073] In some preferred embodiments, the impurity removal module includes a salt solution fluoride concentration detection unit, a second control unit, a calcium-based defluorinating agent defluorination unit, and an aluminum-based defluorinating agent defluorination unit. The salt solution fluoride concentration detection unit is connected to the salt solution outlet of the slurry dissolution module and is used to obtain the fluoride concentration of the salt solution. The second control unit is connected to the fluoride concentration detection unit, the calcium-based defluorinating agent defluorination unit, and the aluminum-based defluorinating agent defluorination unit, respectively, and is used to remove fluoride ions from the salt solution with an aluminum-based defluorinating agent when the fluoride concentration of the salt solution is detected to be below a threshold, and to remove fluoride ions from the salt solution with a calcium-based defluorinating agent when the fluoride concentration of the salt solution is detected to be not below the threshold.

[0074] In some preferred embodiments, the fluoride concentration detection unit is connected to the calcium-based defluorinating agent defluorinating unit and the aluminum-based defluorinating agent defluorinating unit respectively, and is used to obtain the fluoride concentration of the purified salt solution coming out of the calcium-based defluorinating agent defluorinating unit and the aluminum-based defluorinating agent defluorinating unit.

[0075] The present invention will be further described in detail below with reference to specific embodiments. The detection methods involved in the embodiments are as follows:

[0076] The chemical oxygen demand (COD) in wastewater is specifically detected using the potassium dichromate oxidation method.

[0077] The soluble COD of waste salt and carbonized salt is specifically detected by the potassium dichromate oxidation method.

[0078] The platinum-cobalt color of the aqueous solution of the carbonized salt and the purified mother liquor were specifically detected by the platinum-cobalt colorimetric method.

[0079] The fluoride concentration in the salt solution is specifically detected using the ion-selective electrode method.

[0080] Example 1

[0081] A method for cleaning and treating saline wastewater, wherein the wastewater contains Na + The concentration was 13.8 g / L, Cl - The concentration was 7.08 g / L, SO4 2- The concentration was 19.15 g / L, K + The concentration is 0.05 g / L, Mg 2+ The concentration was 720 mg / L, Ca2+ The concentration was 550 mg / L, and the heavy metal ions included Cu. 2+ The concentration was 110 mg / L, Ni 2+ The concentration was 32 mg / L, Mn 2+ The concentration of Zn was 13 mg / L. 2+ The concentration of fluorine was 80 mg / L, the concentration of ammonia nitrogen was 2318 mg / L, the concentration of fluorine was 105 mg / L, and the chemical oxygen demand (COD) was 7205 mg / L.

[0082] The steps are as follows:

[0083] Step 1: The saline wastewater is pretreated in the pretreatment module by adjusting the pH of the wastewater to 11.5 using lime and NaOH to remove heavy metal ions and magnesium ions. 2+ Na2CO3 is added to the wastewater to control the total calcium and magnesium content in the wastewater to no more than 100 ppm. The wastewater is then treated by ammonia stripping to control the ammonia nitrogen content in the wastewater to no more than 30 ppm, thus obtaining saline water.

[0084] Step 2: The saline water obtained in Step 1 is fed into the evaporation crystallization module through the wastewater inlet of the evaporation crystallization module for evaporation crystallization treatment. Waste salt and crystallization mother liquor are obtained at the waste salt outlet and the crystallization mother liquor outlet, respectively. The water content of the waste salt is controlled to be less than 5wt%. The soluble COD content of the waste salt is measured to be 7100g / t by the soluble COD detection unit.

[0085] Step 3: The waste salt obtained in Step 2 is fed into the carbonization unit through the waste salt inlet for carbonization treatment. The first control unit then supplies CuO to the carbonization unit through the catalyst inlet for waste salt carbonization, yielding carbonized salt. The carbonization process is carried out in a carbonization furnace, using natural gas for external heating. The kiln is divided into a heating section and a non-heating section, with the heating section having a length L. 加热 The ratio of the diameter D of the heating section to the total diameter of the kiln is 10, the horizontal inclination angle of the kiln body is 4°, the kiln body is equipped with lifting plates, the ratio of catalyst addition to waste salt mass is 0.025, the carbonization temperature is 550℃, the rotation speed of the kiln body used for carbonization is 1.2 rpm, and the carbonization time is 1.5 h. The COD content of the carbonized salt was measured to be 68 g / t, the platinum-cobalt color of the 20 wt% carbonized salt solution was 32 degrees, and the tail gas after carbonization entered the tail gas treatment unit for tail gas treatment.

[0086] Step 4: The carbonized salt obtained in Step 3 is fed into the slurry dissolution unit through the carbonized salt inlet for slurry dissolution treatment. Water is fed into the slurry dissolution unit through the solvent inlet for slurry dissolution of the carbonized salt. A salt solution with a concentration of 22 wt% is obtained at the salt solution outlet. The fluoride concentration in the salt solution is measured to be 82 mg / L by the salt solution fluoride concentration detection unit. The waste salt obtained in Step 2 contains 29.13 wt% sodium chloride, and the fluoride concentration in the salt solution is higher than 30 ppm. The second control unit then feeds the salt solution through the salt solution inlet of the impurity removal module into the calcium-based defluorinating agent defluorination unit to remove heavy metal ions and Mg. 2+ The fluoride concentration in the salt solution from the calcium-based defluorinating agent unit was measured to be 25 mg / L by the salt solution fluoride concentration detection unit. The second control unit then passed the salt solution from the calcium-based defluorinating agent unit into the aluminum-based defluorinating agent unit for further defluorination. The fluoride concentration in the salt solution from the aluminum-based defluorinating agent unit was measured to be <10 ppm by the salt solution fluoride concentration detection unit. After defluorination, the total hardness of the salt solution was measured to be 16.8 mg / L, and the Cu content was [not specified]. 2+ Ni 2+ Zn 2+ Mn 2+ The concentrations of all impurities were below 1 mg / L. After the above impurity removal process, a purified solution was obtained. The purified solution was then subjected to a second evaporation and crystallization treatment to obtain purified salt and secondary crystallization mother liquor.

[0087] Step 5: The secondary crystallization mother liquor obtained in Step 4 is subjected to secondary crystallization mother liquor adsorption treatment in the mother liquor adsorption unit to obtain circulating crystallization mother liquor. The circulating crystallization mother liquor is then returned to the secondary evaporation crystallization unit for secondary evaporation crystallization treatment.

[0088] Example 2

[0089] The procedure was carried out in accordance with Example 1, except that in step three, the catalyst supply unit of the first control unit fed CuSO4 aqueous solution into the carbonization unit through the catalyst inlet of the carbonization unit for the carbonization of waste salt. The concentration of CuSO4 in the CuSO4 aqueous solution was 75 g / L. The water content of the carbonization raw material after mixing waste salt and CuSO4 aqueous solution was less than 5%. The soluble COD content of the carbonized salt was measured to be 24 g / t, and the platinum-cobalt color of the 20 wt% carbonized salt aqueous solution was 13.5 degrees.

[0090] Example 3

[0091] The experiment was conducted in accordance with Example 1, except that the catalyst was a zinc sulfate solution, the COD content of the carbonized salt was measured to be 185 g / t, and the platinum-cobalt color of the 20 wt% carbonized salt aqueous solution was 95 degrees.

[0092] Example 4

[0093] The experiment was conducted in accordance with Example 1, except that the catalyst was a nickel sulfate solution, the COD content of the carbonized salt was measured to be 145 g / t, and the platinum-cobalt color of the 20 wt% carbonized salt aqueous solution was 75 degrees.

[0094] Example 5

[0095] The experiment was conducted in accordance with Example 1, except that the catalyst was ferric sulfate solution, the COD content of the carbonized salt was measured to be 175 g / t, and the platinum-cobalt color of the 20 wt% carbonized salt aqueous solution was 90 degrees.

[0096] Example 6

[0097] The experiment was conducted in accordance with Example 1, except that the ratio of the amount of catalyst added to the mass of waste salt was 0.005, the soluble COD content of the carbonized salt was measured to be 300 g / t, and the platinum-cobalt color of the 20 wt% carbonized salt aqueous solution was 120 degrees.

[0098] Example 7

[0099] The procedure was carried out in accordance with Example 1, except that the carbonization time was 0.4 h, the soluble COD content of the carbonized salt was measured to be 200 g / t, and the platinum-cobalt color of the 20 wt% carbonized salt aqueous solution was 102 degrees.

[0100] Example 8

[0101] The procedure is carried out in accordance with Example 1, except that the wastewater contains Na + The concentration was 15.5 g / L, Cl - The concentration was 6.8 g / L, SO4 2- The concentration was 22.7 g / L, K + The concentration was 0.03 g / L, Mg 2+ The concentration was 705 mg / L, Ca 2+ The concentration was 608 mg / L, and the heavy metal ions included Cu. 2+ The concentration was 95 mg / L, Ni 2+ The concentration was 38 mg / L, Mn 2+ The concentration of Zn is 11 mg / L. 2+The concentrations were 86 mg / L, ammonia nitrogen 2220 mg / L, fluorine 42 mg / L, and chemical oxygen demand (COD) 2200 mg / L. In step two, the soluble COD content of the waste salt was measured to be 3820 g / t using a soluble COD detection unit. In step three, the ratio of catalyst addition to waste salt mass was 0.01, the carbonization temperature was 500℃, the kiln rotation speed was 2.0 rpm, and the carbonization time was 2 hours. The soluble COD content of the carbonized salt was measured to be 33.6 g / t, and the platinum-cobalt color of the 20 wt% carbonized salt solution was 25 degrees. In step four, the fluorine concentration of the salt solution was measured using a fluorine concentration detection unit. The fluoride concentration in the salt solution was 38 mg / L. The waste salt obtained in step two contained 75.6% sodium sulfate (dry basis). The fluoride concentration in the salt solution was below 50 ppm. The second control unit then passed the salt solution through the salt solution inlet of the impurity removal module into the aluminum-based defluorinating agent defluorination unit for defluorination treatment. The fluoride concentration of the salt solution exiting the aluminum-based defluorinating agent defluorination unit was measured to be <10 ppm by the salt solution fluoride concentration detection unit. After heavy metal and fluoride removal, the total hardness of the salt solution was measured to be 17.8 mg / L, and the Cu content was [not specified]. 2+ Ni 2+ Zn 2+ Mn 2+ The concentrations of all impurities were below 1 mg / L. After the above impurity removal process, a purified solution was obtained. The purified solution was then subjected to a second evaporation and crystallization treatment to obtain purified salt and secondary crystallization mother liquor.

[0102] Example 9

[0103] The procedure was carried out in accordance with Example 8, except that no catalyst was added in step three, the carbonization temperature was 575°C, the rotation speed of the kiln used for carbonization was 1.2 rpm, the carbonization time was 2 h, the soluble COD content of the carbonized salt was measured to be 52 g / t, and the platinum-cobalt color of the 20 wt% carbonized salt aqueous solution was 31 degrees.

[0104] Comparative Example 1

[0105] The experiment was conducted in accordance with Example 1, except that no catalyst was added. The soluble COD content of the carbonized salt was measured to be 1630 g / t, and the platinum-cobalt color of the 20 wt% carbonized salt aqueous solution was 410 degrees.

[0106] Comparative Example 2

[0107] The experiment was conducted in accordance with Example 1, except that the carbonization temperature was 450°C, the soluble COD content of the carbonized salt was measured to be 980 g / t, and the platinum-cobalt color of the 20 wt% carbonized salt aqueous solution was 290 degrees.

[0108] Comparative Example 3

[0109] The process was carried out in accordance with Example 1, except that the carbonization temperature was 650°C, the carbonized salts partially melted and agglomerated in the kiln, and the carbonization operation was abnormal.

[0110] Comparative Example 4

[0111] The experiment was conducted in accordance with Example 1, except that the kiln rotation speed was 4.0 rpm, the soluble COD content of the carbonized salt was measured to be 1020 g / t, and the platinum-cobalt color of the 20 wt% carbonized salt aqueous solution was 295 degrees.

[0112] Comparative Example 5

[0113] The experiment was conducted in accordance with Example 8, except that the carbonization temperature was 300°C, the soluble COD content of the carbonized salt was measured to be 1850 g / t, and the platinum-cobalt color of the 20 wt% carbonized salt aqueous solution was 450.

[0114] Comparative Example 6

[0115] The experiment was conducted in accordance with Example 8, except that the kiln rotation speed was 4.5 rpm, the soluble COD content of the carbonized salt was measured to be 1100 g / t, and the platinum-cobalt color of the 20 wt% carbonized salt aqueous solution was 298.

[0116] Comparative Example 7

[0117] The experiment was conducted in accordance with Example 9, except that the carbonization temperature was 350°C, the soluble COD content of the carbonized salt was measured to be 1920 g / t, and the platinum-cobalt color of the 20 wt% carbonized salt aqueous solution was 456.

[0118] Comparative Example 8

[0119] The experiment was conducted in accordance with Example 9, except that the kiln rotation speed was 4.6 rpm, the soluble COD content of the carbonized salt was measured to be 1210 g / t, and the platinum-cobalt color of the 20 wt% carbonized salt aqueous solution was 299.

[0120] Examples 1-5 show that catalysts such as sulfates or oxides of copper, nickel, iron, and zinc, when used as catalysts for carbonization, can reduce carbonization temperature, increase the rotation speed of the kiln used for carbonization, and reduce the soluble COD content of the carbonized salt and the platinum-cobalt color of the carbonized salt solution. CuSO4 exhibits better catalytic performance than CuO, and copper catalysts show better catalytic performance than zinc, nickel, and iron catalysts. Examples 1, 6, and 7 show that for waste salt with a soluble COD content of not less than 6000 g / t, carbonization with catalyst assistance, controlling the ratio of catalyst addition to waste salt mass to 0.01-0.1, and a carbonization time of 0.5-2 h, yields better carbonization results.

[0121] By comparing Example 1 and Comparative Examples 1-4, it can be seen that for waste salt with a soluble COD content of not less than 6000 g / t, carbonization treatment with catalyst assistance, controlling the ratio of catalyst addition to waste salt mass to 0.01-0.1, controlling the carbonization temperature to 500-600℃, and controlling the kiln rotation speed to 1-1.5 rpm, can significantly reduce the soluble COD content of the carbonized salt and the platinum-cobalt color of the carbonized salt solution. It can also prevent the salt from partially melting and adhering to the heating cylinder wall of the kiln to form a ring, which would affect the normal operation of the equipment. Furthermore, carbonization treatment with catalyst assistance combined with a suitable kiln rotation speed can significantly reduce the temperature requirements for carbonization treatment.

[0122] By comparing Example 8 and Comparative Examples 5-6, it can be seen that for waste salt with a soluble COD content of less than 6000 g / t, carbonization treatment with catalyst assistance, and controlling the rotation speed of the kiln used for carbonization treatment to be 1.5-3 rpm and the carbonization temperature to be 400-550℃, can significantly reduce the soluble COD content of the carbonized salt and the platinum-cobalt color of the carbonized salt solution. Moreover, the use of catalyst assistance can reduce the carbonization temperature and increase the rotation speed of the kiln, thus lowering the process requirements for carbonization treatment.

[0123] By comparing Example 9 and Comparative Examples 7-8, it can be seen that for waste salt with a soluble COD content of less than 6000 g / t, controlling the rotation speed of the kiln used for carbonization treatment to 1-1.5 rpm and the carbonization temperature to 550-600℃ can significantly reduce the soluble COD content of the carbonized salt and the platinum-cobalt color of the carbonized salt solution.

[0124] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for cleaning up saline wastewater, characterized in that, The method includes: Wastewater is subjected to evaporation and crystallization treatment to obtain waste salt and crystallization mother liquor; The waste salt and catalyst are subjected to carbonization treatment to obtain carbonized salt; the catalyst is copper sulfate or copper oxide. Wherein, when the soluble COD content of the waste salt is less than 6000 g / t, the carbonization treatment conditions include: carbonization temperature satisfying: 400℃ ≤ carbonization temperature < 550℃, the rotation speed of the kiln used for carbonization treatment satisfying: 1.5 rpm < the rotation speed of the kiln used for carbonization treatment ≤ 3.0 rpm, the ratio of the amount of catalyst added to the mass of the waste salt being 0.002~0.02, and the carbonization time being 0.5~2 h; When the soluble COD content of the waste salt is not less than 6000 g / t, the carbonization treatment conditions include: carbonization temperature of 500℃~600℃, and controlling the rotation speed of the kiln used for carbonization treatment to be 1~1.5 rpm, the ratio of the amount of catalyst added to the mass of the waste salt is 0.01-0.1, and the carbonization time is 0.5~2 h; The processing method further includes: after the carbonization treatment, subjecting the carbonized salt to a slurry dissolution treatment to obtain a salt solution; and subjecting the salt solution to a purification treatment to obtain purified salt. When the fluoride concentration of the salt solution is below a threshold, the impurity removal treatment includes removing fluoride ions with an aluminum-based defluorinating agent; when the fluoride concentration of the salt solution is not below a threshold, the impurity removal treatment includes removing fluoride ions with a calcium-based defluorinating agent; the threshold is 25~55 ppm. When the dry basis sodium chloride content in the waste salt is higher than the dry basis sodium sulfate content, the threshold is 25~35ppm; when the dry basis sodium sulfate content in the waste salt is higher than the dry basis sodium chloride content, the threshold is 45~55ppm.

2. The processing method according to claim 1, characterized in that, The kiln used for the carbonization process includes a heating section and a non-heating section, the length of which is... L 加热 With respect to the diameter of the heating section D The ratio is 6 to 15, and / or the horizontal tilt angle of the kiln body is 3 to 5°.

3. The processing method according to claim 2, characterized in that, The heating method for the carbonization process is external heating of the kiln.

4. The processing method according to claim 2, characterized in that, The kiln body is equipped with lifting lifters.

5. The processing method according to claim 1, characterized in that, The carbonization raw materials for the carbonization treatment are the waste salt and the catalyst, and the water content of the carbonization raw materials is ≤5wt%.

6. The processing method according to claim 1, characterized in that, The salt concentration in the salt solution is 15wt% to 25wt%.

7. A treatment system for the saline wastewater clean treatment method according to any one of claims 1-6, characterized in that, The system includes: an evaporation crystallization module and a carbonization module; the evaporation crystallization module is equipped with a wastewater inlet, a waste salt outlet, and a crystallization mother liquor outlet; the carbonization module includes: a catalyst supply unit and a carbonization unit, the carbonization unit being equipped with a waste salt inlet, a catalyst inlet, and a carbonized salt outlet, the waste salt inlet being connected to the waste salt outlet of the evaporation crystallization module, and the catalyst inlet being connected to the catalyst supply unit; and the system further includes: A soluble COD detection unit, which is connected to the evaporation crystallization module or the carbonization unit, is used to detect the soluble COD content of waste salt. The first control unit is connected to the dissolved COD detection unit, the carbonization unit, and the catalyst supply unit, respectively, and is used to introduce the catalyst into the waste salt in proportion when the dissolved COD content of the waste salt is detected to be less than 6000 g / t, and to introduce the catalyst into the waste salt in proportion when the dissolved COD content of the waste salt is detected to be not less than 6000 g / t.

8. The processing system according to claim 7, characterized in that, The system also includes a pulping and dissolving module and a purification module; The slurry dissolution module is equipped with a carbonized salt inlet, a solvent inlet, and a salt solution outlet. The carbonized salt inlet is connected to the carbonized salt outlet of the carbonization unit, and the solvent inlet is used to introduce a solvent for slurry dissolution into the carbonized salt. The impurity removal module is provided with a salt solution inlet and a purified salt outlet, and the salt solution inlet and the salt solution outlet are connected.

9. The processing system according to claim 8, characterized in that, The impurity removal module includes a salt solution fluoride concentration detection unit, a second control unit, a calcium-based fluoride removal agent fluoride removal unit, and an aluminum-based fluoride removal agent fluoride removal unit. The salt solution fluoride concentration detection unit is connected to the salt solution outlet of the slurry dissolution module and is used to obtain the fluoride concentration of the salt solution. The second control unit is connected to the fluoride concentration detection unit, the calcium-based defluorinating agent defluorination unit, and the aluminum-based defluorinating agent defluorination unit, respectively, and is used to remove fluoride ions from the salt solution with an aluminum-based defluorinating agent when the fluoride concentration of the salt solution is detected to be lower than a threshold, and to remove fluoride ions from the salt solution with a calcium-based defluorinating agent when the fluoride concentration of the salt solution is detected to be not lower than the threshold.

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