Industrial byproduct carnallite resourceful treatment process

Abstract

The invention discloses an industrial by-product carnallite resourceful treatment process which comprises the following steps: S1, pretreating an industrial by-product to enable the industrial by-product to meet the feeding requirement of a pyrolyzing furnace; s2, in an anoxic, inert and weak reducing / oxidizing atmosphere, pyrolyzing to remove organic matters in the carnallite material; s3, mixing the carnallite treated in S2 with a solvent, fully dissolving to form carnallite mixed liquor, and performing solid-liquid separation to obtain filtrate and filter residues; adjusting the pH value of the filtrate to be neutral, evaporating and crystallizing to obtain high-purity sodium chloride, and circulating the residual water to a dissolving stage; dissolving filter residues by using water at 40-50 DEG C, and filtering to obtain a salt solution mainly containing sodium sulfate; sodium sulfate with relatively high purity is obtained after freezing crystallization. The industrial byproduct carnallite is subjected to four stages of pretreatment, pyrolysis, salt dissolving and evaporation freezing crystallization, the whole process of carnallite resourceful treatment is achieved, and the industrial byproduct carnallite resourceful treatment process with high efficiency and high purity is provided.

Description

Technical Field

[0001] This invention relates to the field of industrial waste resource utilization technology, specifically a process for the resource utilization of industrial by-product salts. Background Technology

[0002] Mixed salts, generally referring to solid waste containing various salts generated during industrial production processes, are produced in large quantities in the treatment of high-salt wastewater from industries such as pesticides, pharmaceuticals, coal and petroleum, and textile printing and dyeing. The specific composition of industrial mixed salts varies greatly and their characteristics are not fixed due to different sources. They not only contain valuable salts such as sodium chloride (NaCl) and sodium sulfate (Na2SO4), but also organic matter derived from production raw materials and by-reactions, small amounts of heavy metal ions, and other inorganic salts. The presence of these complex components makes it difficult to directly reuse mixed salts as industrial raw materials and also poses a potential pollution risk to the environment. The resource-based treatment of industrial by-product mixed salts has always been a difficult problem for many enterprises. Existing industrial by-product mixed salt treatment processes mainly have the following shortcomings: 1. Incomplete removal of organic matter: Traditional treatment methods often fail to effectively remove organic impurities from mixed salts without damaging the salt structure, resulting in low purity of the final recovered salt product and limiting its application in the chemical industry.

[0003] 2. Low purity of salt recovery: Due to the immature technology for separating different salts, especially when mixed salts contain multiple types of salts, it is difficult to accurately separate high-purity single salt products, which directly affects the economic and environmental benefits of resource recovery.

[0004] 3. Poor process closure: The existing process also generates new waste disposal problems.

[0005] Therefore, there is an urgent need for a resource-based treatment method for mixed salts that can improve the efficiency of mixed salt processing and the purity of the products. Summary of the Invention

[0006] This application provides a process for the resource recovery of industrial by-product salts by improving the removal of organic matter and the purity of salt recovery, including the following steps: S1, pre-treats industrial by-product salts to convert them into salt materials that meet the feed requirements of pyrolysis furnaces; S2, under an oxygen-deficient, inert, and weakly reducing / oxidizing atmosphere, utilizes a pyrolysis process to remove organic matter from the mixed salt material in S1, thereby achieving salt recovery; S3, a separation technology based on solubility differences, filters insoluble substances from the salt recovered in S2 through a salt-dissolving process. The salt-dissolving process includes: S31, the mixed salts treated in S2 are mixed with a solvent and fully dissolved to form a mixed salt solution. The mixed salt solution is then subjected to solid-liquid separation to obtain a filtrate and a filter residue. The filtrate and filter residue are then subjected to the following treatments respectively: S32, the pH of the filtrate is adjusted to neutral, and then evaporated and crystallized to obtain high-purity solid sodium chloride. The remaining water after evaporation and crystallization is recycled to the dissolution stage of S31. S33, using water at a temperature of 40℃~50℃, dissolve the filter residue at a solid-liquid ratio of 1:3, filter out insoluble impurities, and obtain a salt solution mainly composed of sodium sulfate. S34. The sodium sulfate-based salt solution obtained in S33 is frozen and crystallized to obtain sodium sulfate crystals with high purity.

[0007] Preferably, in step S32, the amount of water evaporated each time is controlled to be less than 70%, and the amount of water remaining after evaporation and crystallization is 30%. In S34, the conditions for freeze crystallization are: Freeze and crystallize at 0°C for 1 hour.

[0008] Preferably, the preprocessing step S1 includes: 1) The industrial by-product salts are crushed to make their particle size meet the feeding requirements of the ball mill; 2) The crushed mixed salt material is classified according to particle size, and the material with a particle size exceeding the feed requirement is screened out and returned to 1) for re-crushing until the particle size of the mixed salt material meets the feed requirement of the ball mill. 3) Ball mill the mixed salt material that meets the screening requirements to refine its particles, and screen out the material whose particle size does not meet the feed requirements of the pyrolysis furnace. Return the material whose particle size does not meet the feed requirements of the pyrolysis furnace to the ball milling operation in this step for further refinement, so as to ensure that the particle size of the final mixed salt material meets the feed requirements of the pyrolysis furnace.

[0009] Preferably, in the pyrolysis process of S2, the pyrolysis process parameters are determined based on the composition of the mixed salt material and the target product. Wherein: the pyrolysis temperature is 400℃~600℃, the pyrolysis time is 30min~120min, and the pyrolysis atmosphere is one or more of nitrogen, argon, helium or oxygen to provide an inert, weakly reducing / oxidizing environment.

[0010] Preferably, the heating method is indirect heating; Indirect heating refers to the additional heating of the indirect heating furnace.

[0011] Preferably, the solid-liquid ratio of the solvent to the treated mixed salt material is 1:2.5 to 1:1. In step S31, The dissolution time is 15 min to 20 min.

[0012] Preferably, the solvent used to dissolve the mixed salts in S31 is water; The temperature of the water is selected based on the proportion of sodium sulfate in the mixed salts after formulation. When the sodium sulfate content is greater than 15% of the total mixed salts, water at 0°C should be used as the solvent. When the sodium sulfate content is less than 15%, water at room temperature should be used as the solvent.

[0013] Preferably, in the S32 filtrate pH adjustment stage, the type and amount of pH adjuster used to adjust the filtrate pH are selected according to the pH value of the filtrate; The mother liquor after the S32 filtrate is evaporated and crystallized is returned to the S31 salt dissolution process.

[0014] Preferably, Glauber's salt (sodium sulfate crystals) is obtained by freeze crystallization in S34. The freezing temperature for crystallization was 0℃, and the freezing time was 1 hour.

[0015] Preferably, the frozen mother liquor is returned to the low-temperature dissolution system to be used as a solvent to dissolve impurities, maintaining a constant proportion of salt solution entering the evaporation system and achieving a closed-loop process.

[0016] The beneficial effects of this application are as follows: This application pre-treats industrial by-product salts, transforming them into salt materials that meet the feed requirements of pyrolysis furnaces. Under an inert, weakly reducing / oxidizing atmosphere, pyrolysis is used to remove organic matter from the pre-treated salt materials, achieving salt recovery. Based on a separation technology utilizing solubility differences, industrial-grade sodium chloride and sodium sulfate products with a purity ≥97.5% are obtained through salt dissolution and evaporation / freeze-crystallization processes. This completes the entire process of resource-based treatment of by-product salts.

[0017] This application utilizes the characteristics of pyrolysis technology in decomposing organic matter under anaerobic, inert, and weakly reducing / oxidizing atmospheres, as well as the differences in solubility of different salts in water, to effectively remove organic matter from mixed salts. This achieves effective separation of different salts and improves salt purity, meeting the standards of industrial-grade salt products. Overall, it realizes the reduction of organic matter and the resource utilization of salts, while simultaneously reducing energy consumption and environmental pollution during the treatment process.

[0018] Meanwhile, by adjusting the pyrolysis temperature, time, and atmosphere, as well as the solvent type and solid-liquid ratio in the salt dissolution process, the treatment effect can be optimized, thus solving the technical problem of processing mixed salt materials containing different types of salts and varying salt contents.

[0019] This application utilizes crushing and ball milling techniques to improve pyrolysis efficiency, reduce material accumulation in the pyrolysis furnace, and avoid localized overheating, thereby increasing the decomposition rate of organic matter and the recovery rate of salt.

[0020] The pyrolysis process utilizes high temperatures to decompose organic matter in an oxygen-deficient, inert, and weakly reducing / oxidizing atmosphere, while avoiding the melting and coking of salts, thus protecting the purity of the salts. This process improves the salt recovery rate while reducing the generation of harmful substances such as dioxins, thereby enhancing the environmental friendliness of the treatment process. Cooling crystallization takes advantage of the reduced solubility of sodium sulfate at low temperatures. By controlling the freezing conditions, efficient crystallization of sodium sulfate and removal of impurities are achieved.

[0021] The technology of recycling evaporation and freezing mother liquor improves solvent utilization efficiency and reduces the consumption of new solvent. Furthermore, since freezing only separates sodium sulfate from the mother liquor, it does not introduce new impurities. By controlling the temperature, the ratio and total amount of sodium sulfate and sodium chloride dissolved in water are fixed, allowing for system stability during the dissolution stage and thus achieving controllable solvent recycling. By detecting impurities and determining the ratio of sodium chloride to sodium sulfate, and then adjusting the formula based on the results, the proportion of solute at the front end and the temperature at the back end are kept constant, further ensuring a constant amount of sodium chloride and sodium sulfate dissolved in water at a specific temperature. This achieves closed-loop process control while improving the stability, economy, and environmental friendliness of the treatment process. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of a process for the resource utilization of industrial by-product salts according to this application. Detailed Implementation

[0023] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] A process for the resource utilization of industrial by-product salts: S1 involves pretreating industrial by-product salts to convert them into salt materials that meet the feed requirements of the pyrolysis furnace. The specific process is as follows: 1) Crushing process: Industrial by-product salts (specifically, salts directly input into the factory from the waste-producing unit) are fed into a crusher from their initial state (usually in block form, with particle sizes ranging from 1000mm to 50mm) and crushed to the particle size required by the ball mill (generally ≤25mm).

[0025] Crushing ratio: The single-stage crushing ratio is generally 3~8 (such as jaw crusher). If fine crushing is required, multi-stage crushing (such as jaw crusher + hammer crusher) can be used.

[0026] 2) Screening: The crushed mixed salt material is classified by particle size, and the material with a particle size exceeding the feed requirement is screened out and returned to 1) for re-crushing until the particle size of the mixed salt material meets the feed requirement of the ball mill, so as to ensure that the particle size of the material entering the ball mill is uniform and to avoid local overheating or incomplete reaction.

[0027] Materials whose particle size exceeds the feed requirements include large-particle mixed salts themselves, as well as uncrushed impurities. Mixed salts that meet the screening requirements after crushing are matched with the further ball mill feed requirements.

[0028] In one embodiment of this application, the mesh size of the sieve is selected according to the feeding requirements of the ball mill; Screening efficiency: ≥85%, to avoid fine powder clogging the screen and affecting the uniformity of pyrolysis.

[0029] Processing capacity: The processing capacity of the matching crushing stage is 5t / h to 50t / h.

[0030] The screening equipment uses a vibrating screen or a drum screen. The vibrating screen is preferably a linear vibrating screen with a screen surface inclination angle of 15°~25°, an amplitude of 3mm~6mm, and a motor power of 2.2kW~15kW. For damp mixed salt materials, a drum screen is selected. During the screening process, the material rolls and rubs against the screen to avoid clogging. The screening accuracy is ≤5mm, the processing capacity is 5t / h~20t / h, and the motor power is 3kW~11kW.

[0031] If the mixed salts contain sticky components, spray a small amount of water mist before sieving to prevent sticking, or use an anti-stick screen.

[0032] 3) Ball milling is performed on the mixed salt materials that meet the screening requirements to refine their particle size: In this application, the particles of the mixed salt material that meets the screening requirements are further refined by ball milling, shortening the subsequent processing time. The pyrolysis reaction time is reduced to increase the decomposition rate of organic matter and at the same time reduce the risk of local high temperature caused by material accumulation in the pyrolysis furnace.

[0033] In one embodiment of this application, the particle size of the sieved mixed salt material is typically 25mm to 50mm. After further ball milling, the particle size of the mixed salt material is 0.5mm to 1mm, thereby meeting the requirements of the pyrolysis furnace for material homogenization and increased specific surface area.

[0034] In one embodiment of this application, the ball milling equipment is a dry ball mill. The material discharged after ball milling needs to be classified by a vibrating screen or spiral classifier. Impurities with a particle size >1mm that do not meet the standards are returned to the ball mill for regrinding to form a closed-loop cycle. Since the main component of the dust generated during the ball milling process is fine salt powder, the ball mill of this application is equipped with a bag filter dust collector, and the dust generated during the ball milling process is used in the ball milling or pyrolysis process to avoid waste.

[0035] S2, under an oxygen-deficient, inert, and weakly reducing / oxidizing atmosphere, utilizes a pyrolysis process to remove organic matter from the mixed salt material in S1, achieving salt recovery. Specifically: Under an oxygen-deficient, inert, and weakly reducing / oxidizing atmosphere, the mixed salt material after S1 treatment is decomposed at a high temperature of 400℃~600℃. This temperature is used to decompose the organic matter (such as COD and volatile matter) in the mixed salt on the one hand, and to prevent the salt in the mixed salt material from melting and coking on the other hand, ultimately achieving the reduction of organic matter and the recovery of salt, wherein the decomposition rate of organic matter is ≥95%.

[0036] It should be noted that the parameters of the pyrolysis process need to be optimized based on the composition of the mixed salt (e.g., the organic content in the mixed salt material, the melting point of the salt in the mixed salt material) and the target product (e.g., the purity of crude salt, exhaust gas emissions). In one embodiment of the pyrolysis process of this application, the pyrolysis temperature is 450℃~550℃, and the residence time is 30min~120min; nitrogen is used in the pyrolysis atmosphere to suppress the formation of dioxins caused by excessive organic content in the mixed salt.

[0037] In one embodiment of this application, the heating method in the pyrolysis process adopts indirect heating furnace thermal desorption technology, which achieves cleaner heating and eliminates the mixing of combustion exhaust gas, thereby improving the purity of salt recovery.

[0038] The thermal desorption technology employs radiant heating, and the pyrolysis furnace is selected from one or more of a rotary pyrolysis furnace, a fixed-bed pyrolysis furnace, a fluidized-bed pyrolysis furnace, or a rotary kiln. The pyrolysis atmosphere is one or more of nitrogen, argon, helium, or oxygen to provide an inert, weakly reducing / oxidizing environment to prevent salts from melting and coking.

[0039] S3, a separation technology based on solubility differences, filters insoluble substances from the salt recovered in S2 through a salt-dissolving process. The salt-dissolving process includes: S31, the mixed salts treated in S2 are mixed with a solvent to dissolve the soluble components in the mixed salts, forming a mixed salt solution. The mixture is then subjected to solid-liquid separation to obtain a filtrate containing soluble salts and a filter residue containing insoluble solids. The filtrate and filter residue are then subjected to the following treatments: S32, the pH of the filtrate is adjusted, and then evaporated and crystallized to obtain sodium chloride product with high purity (purity ≥97.5%), and the remaining water after evaporation and crystallization is recycled to the salt dissolution stage of S31. S33, the filter residue is dissolved in water at a temperature of 40℃~50℃ at a solid-liquid ratio of 1:3, and insoluble impurities are filtered out to obtain a salt solution mainly composed of sodium sulfate. S34. The sodium sulfate-based salt solution obtained in S33 is frozen and crystallized to obtain sodium sulfate crystals with high purity (≥97.5%).

[0040] The above S31 and S32 mainly separate sodium chloride from miscellaneous salts. The specific process includes: First, the mixed salts are dissolved to obtain a mixed salt solution. Specifically, the solvent is selected according to the ratio of sodium chloride to sodium sulfate in the mixed salts. If the sodium sulfate content is greater than 15%, 0℃ water is used as the solvent for dissolution; if the sodium sulfate content is less than 15%, room temperature water is used as the solvent for dissolution. The solid-liquid ratio (i.e., the ratio of mixed salts to solvent) is 1:2.5 to 1:1.

[0041] Then, the mixed salt solution is filtered. The filter residue mainly contains sodium sulfate, insoluble impurities, and pyrolytic carbon; while the filtrate is a salt solution mainly composed of sodium chloride.

[0042] Next, the pH of the filtrate containing sodium chloride is adjusted using dilute hydrochloric acid or dilute sodium hydroxide to a suitable range. The pH adjuster includes both alkaline and acidic agents. In this application, HCl solution is used as the acidic agent, while NaOH solution is used as the alkaline agent. The specific choice between HCl and NaOH solution, and the amount used, is determined based on the acidity or alkalinity of the mixed salt solution itself. By adding the adjuster, the mixed salt solution is ultimately controlled to neutrality, thereby controlling the quality of the effluent and preventing excessive levels of impurity ions.

[0043] Finally, the pH-adjusted salt solution is evaporated under negative pressure (less than 70% of the water is evaporated) to obtain sodium chloride with high purity; the remaining 30% of the water is recycled to the dissolution stage.

[0044] The above steps S33 and S34 mainly achieve the separation of sodium sulfate from miscellaneous salts. The specific process includes: The filter residue obtained by filtration is dissolved in water at 40℃~50℃ at a solid-liquid ratio of 1:3, and insoluble impurities are removed by filtration to obtain a salt solution mainly composed of sodium sulfate.

[0045] Sodium sulfate solution was frozen and crystallized at 0°C for 1 hour to obtain sodium sulfate crystals with high purity.

[0046] It should be noted that: In this application, the water used as the solvent for dissolving miscellaneous salts and dissolving filter residue is either soft water or deionized water.

[0047] In this application, based on the principle that the solubility of sodium sulfate is more sensitive to temperature than that of sodium chloride, the application first uses 0°C water to dissolve sodium chloride in the mixed salts. Since sodium sulfate cannot dissolve in 0°C water and remains solid, filtration is performed at this point, filtering out the solid sodium sulfate and trace amounts of other impurities, while the sodium chloride in the mixed salts remains in solution, resulting in a high-purity sodium chloride brine. Then, 45°C water is used to dissolve the filtered solid sodium sulfate and trace amounts of other impurities. At this point, sodium sulfate dissolves in the 45°C water, while the other impurities remain in solid form, and filtration yields a high-purity sodium sulfate brine. This method separates sodium chloride and sodium sulfate from mixed salts based on water temperatures. Furthermore, by using 0°C water first, compared to existing technologies that use room temperature water to dissolve mixed salts, this application consumes less energy and reduces the dissolution time from two hours to just over ten minutes, significantly improving separation efficiency; and no other impurities are introduced during the entire separation process.

[0048] Meanwhile, the mother liquor after evaporating sodium chloride can be used as a circulating solvent for the salt in S31. This is because at 0℃, the ratio and total amount of sodium chloride and sodium sulfate dissolved in the solvent are constant. By controlling the temperature, the stability of the salt system can be maintained, thus enabling the recycling of the salt solution. By precisely controlling the evaporation rate of the sodium chloride-based brine, the supersaturation of the solution is maintained in the metastable region, ensuring the preferential and stable precipitation of the target salt while suppressing the co-crystallization of impurities, ultimately obtaining a crystal product with large particle size, high purity, and regular morphology.

[0049] This application achieves the effective separation and resource recovery of sodium chloride and sodium sulfate in mixed salts through stepwise dissolution, temperature control, and solvent recycling in the entire salt dissolution process.

[0050] In the salt dissolution process of S31, the type of solvent required for salt dissolution is determined according to the subsequent process requirements; the ratio of the solvent required for salt dissolution to the mixed salt material to be dissolved is determined according to the proportion of sodium chloride in the mixed salt material.

[0051] In one embodiment of this application, since the insoluble substances in the mixed salt material mainly include impurities, carbon, and water-insoluble calcium and magnesium salts, all of which are insoluble in water, the solvent used in this application is water at 0°C, the dissolution time is 15 min to 20 min, and the solid-liquid ratio is 1:2.5 to 1:1.

[0052] The salt in the mixed salt material is mainly sodium chloride. Therefore, if the sodium chloride content in the mixed salt is greater than 90%, a solid-liquid ratio of 1:2.5 is used to dissolve the mixed salt; if the sodium chloride content in the mixed salt is between 70% and 90%, a solid-liquid ratio of 1:2 is used to dissolve the mixed salt; if the sodium chloride content in the mixed salt is between 50% and 70%, a solid-liquid ratio of 1:1.5 is used to dissolve the mixed salt; and if the sodium chloride content in the mixed salt is less than 50%, a solid-liquid ratio of 1:1 is used to dissolve the mixed salt.

[0053] Since the filter residue mainly consists of insoluble impurities, such as organic carbon, inorganic precipitates such as carbonates and sulfates, and some undissolved sodium sulfate, the salt in the filter residue is used as a raw material for preparing sodium sulfate in this application and will be dissolved subsequently.

[0054] The filtered liquid enters the evaporation system, where evaporation and crystallization take place in a high-temperature, low-humidity environment, preferably at 60°C to 80°C and with a humidity ≤30%, to promote sodium chloride crystallization. The amount of water evaporated is less than 70% of the total filtrate volume, ensuring that the sodium sulfate in the solution remains unsaturated throughout the evaporation process. Since the main components of the mixed salts are sodium chloride and sodium sulfate, which are the main impurity ions, the crystallization conditions can be controlled initially by adjusting the amount of water evaporated based on solubility differences. This application achieves high-purity products by controlling the amount of water evaporated, ensuring that the amount of water evaporated does not exceed 70% of the total water volume each time. The precipitated mixed salts are then filtered and dried, resulting in sodium chloride with a purity of over 97.5%.

[0055] The mother liquor after evaporation is already quite concentrated with sodium sulfate. Freeze-crystallization is then performed on the mother liquor at a temperature of -5℃ to 5℃ for at least 2 hours. After filtration, Glauber's salt is obtained. Freezing the mother liquor only separates the sodium sulfate and does not introduce new impurities. Therefore, after drying, the sodium sulfate purity is above 97.5%.

[0056] The frozen mother liquor is returned to the low-temperature dissolution system for recycling, forming a closed-loop process and improving the utilization rate of materials in the entire system. The frozen mother liquor is used as a solvent to continue dissolving miscellaneous salts, and the proportion of salt solution entering the evaporation system is controlled to be constant, and then the process is circulated.

Claims

1. A process for the resource utilization of industrial by-product salts, characterized in that, Includes the following steps: S1, pre-treats industrial by-product salts to convert them into salt materials that meet the feed requirements of pyrolysis furnaces; S2, under an oxygen-deficient, inert, and weakly reducing / oxidizing atmosphere, utilizes a pyrolysis process to remove organic matter from the mixed salt material in S1, thereby achieving salt recovery; S3, a separation technology based on solubility differences, filters insoluble substances from the salt recovered in S2 through a salt-dissolving process. The salt-dissolving process includes: S31, the mixed salts treated in S2 are mixed with a solvent and fully dissolved to form a mixed salt solution. The mixed salt solution is then subjected to solid-liquid separation to obtain a filtrate and a filter residue. The filtrate and filter residue are then subjected to the following treatments respectively: S32, the pH of the filtrate is adjusted to neutral, and then evaporated and crystallized to obtain high-purity solid sodium chloride. The remaining water after evaporation and crystallization is recycled to the dissolution stage of S31. S33, using water at a temperature of 40℃~50℃, dissolve the filter residue at a solid-liquid ratio of 1:3, filter out insoluble impurities, and obtain a salt solution mainly composed of sodium sulfate. S34. The sodium sulfate-based salt solution obtained in S33 is frozen and crystallized to obtain sodium sulfate crystals with high purity.

2. The process for resource utilization of industrial by-product salts according to claim 1, characterized in that, In S32, the amount of water evaporated each time is controlled to be less than 70%, and the amount of water remaining after evaporation and crystallization is 30%. In S34, the conditions for the freeze crystallization of sodium sulfate are: Freeze and crystallize at 0°C for 1 hour.

3. The process for resource utilization of industrial by-product salts according to claim 1, characterized in that, The preprocessing of S1 includes: 1) The industrial by-product salts are crushed to make their particle size meet the feeding requirements of the ball mill; 2) The crushed mixed salt material is classified according to particle size, and the material with a particle size exceeding the feed requirement is screened out and returned to 1) for re-crushing until the particle size of the mixed salt material meets the feed requirement of the ball mill. 3) Ball mill the mixed salt material that meets the screening requirements to refine its particles, and screen out the material whose particle size does not meet the feed requirements of the pyrolysis furnace. Return the material whose particle size does not meet the feed requirements of the pyrolysis furnace to the ball milling operation in this step for further refinement, so as to ensure that the particle size of the final mixed salt material meets the feed requirements of the pyrolysis furnace.

4. The process for resource utilization of industrial by-product salts according to claim 1, characterized in that, In the S2 pyrolysis process, the pyrolysis process parameters are determined based on the composition of the mixed salt material and the target product. Wherein: the pyrolysis temperature is 400℃~600℃, the pyrolysis time is 30min~120min, and the pyrolysis atmosphere is one or more of nitrogen, argon, helium or oxygen to provide an inert, weakly reducing / oxidizing environment.

5. The process for resource utilization of industrial by-product salts according to claim 3, characterized in that, The heating method is indirect heating; Indirect heating refers to the additional heating of the indirect heating furnace.

6. The process for resource utilization of industrial by-product salts according to claim 1, characterized in that, In S31, The solid-liquid ratio of the solvent to the treated miscellaneous salts was 1:2.5 to 1:1; the dissolution time was 15 min to 20 min.

7. The process for resource utilization of industrial by-product salts according to claim 1, characterized in that, In S31, water is used as the solvent to dissolve the mixed salts; The temperature of the water is selected based on the proportion of sodium sulfate in the mixed salts after formulation. When the sodium sulfate content is greater than 15% of the total mixed salts, water at 0°C should be used as the solvent. When the sodium sulfate content is less than 15%, water at room temperature should be used as the solvent.

8. The process for resource utilization of industrial by-product salts according to claim 1, characterized in that, In S32, the type and amount of pH adjuster used to adjust the pH of the filtrate are selected based on the pH value of the filtrate.

9. The process for resource utilization of industrial by-product salts according to claim 1, characterized in that, Glauber's salt product was obtained by freeze crystallization in S34. The mother liquor after the S32 filtrate is evaporated and crystallized is returned to the S31 salt dissolution process.

10. The process for resource utilization of industrial by-product salts according to claim 8, characterized in that, The frozen mother liquor is returned to the low-temperature dissolution system and used as a solvent to dissolve impurities, maintaining a constant proportion of salt solution entering the evaporation system and achieving a closed-loop process.

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