Resourceful treatment process for hazardous waste salt

Abstract

The invention relates to the technical field of industrial waste salt treatment, in particular to a hazardous waste salt resourceful treatment process which comprises the following steps: crushing and screening, and selectively performing high-temperature pyrolysis to remove organic matters; dissolving and filtering to obtain filtrate; selectively adding an alkaline substance and a metal chelating agent into the filtrate to neutralize to form a metal compound precipitate to obtain filtrate; cOD in the filtrate is removed through resin adsorption, and heavy metal impurities and organic matter in the filtrate are removed through activated carbon adsorption; selectively cooling and crystallizing the filtrate adsorbed by the activated carbon, and filtering to obtain a first wet product and filtrate; selectively adding a matched reaction solution into the filtrate to produce a precipitate, filtering and removing impurities to obtain filtrate, and then carrying out an evaporative crystallization process; evaporating and crystallizing to obtain a second wet product; the first wet product and the second wet product are subjected to flash evaporation drying, and the problem that in an existing salt separation crystallization technology, due to the existence of organic matter and complex heavy metal, the resource utilization difficulty is large is solved.

Description

Technical Field

[0001] This application relates to the field of industrial waste salt treatment technology, and in particular to a process for the resource recovery of hazardous waste salt. Background Technology

[0002] Industrial waste salt treatment technologies are mainly divided into two categories: harmless disposal technologies and resource utilization technologies. Harmless disposal technologies primarily include landfill, incineration, and solidification / stabilization methods. In practical engineering applications, safe landfill is the primary method due to potential environmental and safety risks. In particular, regulations such as the "Standard for Pollution Control of Hazardous Waste Landfill" (GB18598-2019) clearly stipulate that the total water-soluble salt content should be less than 10% when using flexible landfill methods for industrial waste salt disposal, while rigid landfill methods are too costly. Therefore, resource utilization technologies are preferable for treating industrial waste salt.

[0003] Currently, the most mature technology for the resource utilization of industrial waste salt is fractional crystallization technology, which involves separating high-purity single salt products through a stepwise crystallization process, thus realizing the resource utilization of industrial waste salt. However, industrial waste salt often contains residual organic impurities, most of which are recalcitrant organic compounds. Some of these organic impurities even complex with heavy metals, significantly inhibiting the crystallization behavior of the salt components in the industrial waste salt and increasing the difficulty of its resource utilization. Summary of the Invention

[0004] To address the aforementioned issues, this application provides a process for the resource recovery of hazardous waste salt.

[0005] The hazardous waste salt resource utilization treatment process provided in this application adopts the following technical solution: A hazardous waste salt resource utilization process includes the following steps: Crushing and screening: The hazardous waste salt is crushed and dusted, and pulverized to below the preset particle size; High-temperature pyrolysis: Determine whether to perform high-temperature pyrolysis based on the type of hazardous waste salt in order to remove organic matter; Dissolution and filtration: Add fresh water and MVR evaporation condensate to the hazardous waste salt to dissolve it, and filter to remove impurities to obtain the filtrate; Neutralization and weight removal: Depending on the type of hazardous waste salt, determine whether to add alkaline substances and metal chelating agents to the filtrate to neutralize and form metal compound precipitates, then filter to remove impurities and obtain the filtrate; Resin adsorption: The filtrate is introduced into the adsorption resin to adsorb COD in the filtrate; Activated carbon adsorption: The filtrate after resin adsorption is subjected to activated carbon adsorption to remove heavy metal impurities and organic matter from the filtrate; Cooling crystallization: Depending on the type of hazardous waste salt, it is determined whether to cool and crystallize the filtrate after activated carbon adsorption, and the first wet product and filtrate are obtained by filtration. Precipitation and impurity removal: Depending on the type of hazardous waste salt, determine whether to heat a suitable reaction solution into the filtrate to produce precipitate, filter to remove impurities to obtain the filtrate, and then carry out the evaporation and crystallization process; Evaporation and crystallization: The filtrate is heated and evaporated to crystallize, yielding a second wet product; Flash drying: The first wet product obtained by cooling crystallization and the second wet product obtained by evaporation crystallization are flash dried.

[0006] Optionally, in the resin adsorption process, the adsorption resin used is brownish-brown opaque spherical particles with a particle size of 0.315 mm to 1.25 mm, a moisture content of 50% to 60%, a wet apparent density of 0.65 to 0.70 g / mL, a wet true density of 1.05 to 1.10 g / mL, and a specific surface area ≥ 1200 m². 2 / g.

[0007] Optionally, the resin adsorption process may further include cleaning and regenerating the adsorption resin using a 0.8% sodium hydroxide solution.

[0008] Optionally, in the high-temperature pyrolysis process, the heating temperature is 500-700℃, so that more than 90% of the organic matter in the hazardous waste salt is removed in the form of organic waste gas. Oxygen is introduced for heating, and the heating temperature is 1100-1200℃, so as to remove more than 99.8% of the organic matter.

[0009] Optionally, when the hazardous waste salt is dyeing and printing salt or sodium sulfate product hazardous waste salt, a high-temperature pyrolysis process is carried out after crushing and screening, a neutralization and degravimetric process is carried out after dissolution and filtration, and a cooling and crystallization process is carried out after activated carbon adsorption. No precipitation and impurity removal process is carried out. The first wet product obtained by cooling crystallization is sodium sulfate wet product, and the second wet product obtained by evaporation crystallization is dye salt wet product.

[0010] Optionally, when the hazardous waste salt is sodium chloride product type hazardous waste salt, a high-temperature pyrolysis process is carried out after crushing and screening, a neutralization and degravimetric process is carried out after dissolution and filtration, and no cooling crystallization and precipitation impurity removal process is carried out after activated carbon adsorption. The second wet product, sodium chloride wet product, is obtained only by evaporation and crystallization.

[0011] Optionally, when the hazardous waste salt is potassium chloride, potassium fluoride, or barium fluoride product type hazardous waste salt, the high-temperature pyrolysis process is not carried out after crushing and screening, the neutralization and degravation process is carried out after dissolution and filtration, and the cooling crystallization, precipitation and impurity removal process is carried out after activated carbon adsorption. In the precipitation and impurity removal process, barium chloride solution is added to the filtrate to produce barium fluoride precipitate. After filtration to remove impurities, the filtrate is then subjected to an evaporation and crystallization process. The first wet product obtained by cooling crystallization is potassium fluoride wet product, and the second wet product obtained by evaporation crystallization is potassium chloride wet product.

[0012] Optionally, when the hazardous waste salt is potassium sulfate or ammonium sulfate product type hazardous waste salt, a high-temperature pyrolysis process is not carried out after crushing and screening, a neutralization and degravimetric process is carried out after dissolution and filtration, a cooling and crystallization process is carried out after activated carbon adsorption, and a precipitation and impurity removal process is not carried out. The first wet product obtained by cooling crystallization is potassium sulfate wet product, and the second wet product obtained by evaporation crystallization is ammonium sulfate wet product.

[0013] Optionally, when the hazardous waste salt is ammonium chloride product type hazardous waste salt, the high-temperature pyrolysis process is not carried out after crushing and screening, the neutralization and degravimetric process is carried out after dissolution and filtration, and the cooling and crystallization process is not carried out after activated carbon adsorption, but the precipitation and impurity removal process is carried out. In the precipitation and impurity removal process, calcium chloride solution is added to the filtrate to generate barium sulfate precipitate. After filtration to remove impurities, the filtrate is then subjected to an evaporation and crystallization process. The second wet product obtained by evaporation and crystallization is ammonium chloride wet product.

[0014] Optionally, when the hazardous waste salt is ammonium bicarbonate product-type hazardous waste salt, no high-temperature pyrolysis process is performed after crushing and screening, no neutralization and degravimetric process is performed after dissolution and filtration, and no cooling crystallization, precipitation, and impurity removal process is performed after activated carbon adsorption; wherein, the second wet product obtained by evaporation and crystallization is ammonium bicarbonate wet product; or, When the hazardous waste salt is sodium phosphate product, a high-temperature pyrolysis process is carried out after crushing and screening. After dissolution and filtration, no neutralization and degravimetric process is carried out. After activated carbon adsorption, no cooling crystallization and precipitation impurity removal process is carried out. The second wet product obtained by evaporation and crystallization is sodium phosphate wet product.

[0015] In summary, this application includes at least one of the following beneficial technical effects: This application utilizes high-temperature pyrolysis to effectively remove organic impurities, including recalcitrant organic matter, from hazardous waste salts. Combined with the use of alkaline substances and metal chelating agents in the neutralization and de-heavy metal removal steps, it breaks the complexation state between organic matter and heavy metals, removing the heavy metals. Further adsorption via resin and activated carbon further reduces COD, heavy metals, and residual organic matter in the filtrate, eliminating the inhibitory effect of these impurities on the crystallization behavior of the salt components. This solves the problem of high resource utilization difficulty caused by the presence of organic matter and complexed heavy metals in existing salt separation and crystallization technologies. Simultaneously, steps such as cooling crystallization and evaporation crystallization achieve the separation and purification of individual salts, avoiding the potential environmental and safety risks and high costs associated with harmless disposal technologies, thus realizing the efficient resource utilization of hazardous waste salts. Attached Figure Description

[0016] Figure 1 This is the process flow and material balance diagram of hazardous waste salts such as dyeing salt and sodium sulfate products in Example 1; Figure 2This is the process flow and material balance diagram for the sodium chloride product hazardous waste salt in Example 2; Figure 3 This is the process flow and material balance diagram of the hazardous waste salt products, namely potassium chloride, potassium fluoride, and barium fluoride, in Example 3; Figure 4 This is the process flow and material balance diagram for the potassium sulfate and ammonium sulfate products, which are hazardous waste salts, in Example 4. Figure 5 This is the process flow and material balance diagram of the ammonium chloride product hazardous waste salt in Example 5; Figure 6 This is the process flow and material balance diagram for the ammonium bicarbonate product hazardous waste salt in Example 6; Figure 7 This is the process flow and material balance diagram for the sodium phosphate product hazardous waste salt in Example 7. Detailed Implementation

[0017] The following will be combined with the appendix Figure 1-7 The technical solutions in the embodiments of this application are clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0018] This application discloses a process for the resource recovery of hazardous waste salt. The process includes crushing and screening, high-temperature pyrolysis, dissolution and filtration, neutralization and deweighting, resin adsorption, activated carbon adsorption, cooling crystallization, precipitation and impurity removal, evaporation crystallization, and flash drying. The necessity of high-temperature pyrolysis, neutralization and deweighting, cooling crystallization, and precipitation and impurity removal depends on the type of hazardous waste salt.

[0019] Crushing and Screening: The hazardous waste salt is crushed and dusted to a preset particle size. Hazardous waste salt is prone to caking during transportation. It is fed into a crusher to be crushed to a particle size of less than 15mm. The material on the sieve is returned to the crusher for further crushing. Both the crusher and the sieve are equipped with dust collectors that can collect dust.

[0020] High-temperature pyrolysis: Whether high-temperature pyrolysis is necessary depends on the type of hazardous waste salt. If the hazardous waste salt decomposes at high temperatures (e.g., ammonium salts), then a high-temperature pyrolysis process is unnecessary. If the hazardous waste salt does not decompose at high temperatures, then a high-temperature pyrolysis process can be performed. Specifically, the undersize material after screening enters a low-temperature dryer. After drying, the hazardous waste salt is fed into a Manhattan furnace via an existing auger feeder. The hazardous waste salt is then placed in the high-temperature pyrolysis chamber of the Manhattan furnace, where it is heated to 500–700°C using natural gas and held for 3 hours. 90% of the organic matter in the hazardous waste salt is removed. The removed organic waste gas is introduced into the secondary combustion chamber, where oxygen is simultaneously introduced. The temperature is then raised to 1100–1200°C using natural gas, with a residence time of 3 seconds to ensure sufficient turbulence within the furnace, removing 99.8% of the organic matter. The organic waste gas then passes through a heat exchanger and enters the waste gas treatment system. After high-temperature pyrolysis, the hazardous waste salt is pushed out of the desorption chamber by rake teeth, enters the cooling pusher for cooling after passing through the discharge port, and is then sent to the elevator by scraper conveyor belt. After being screened by drum screen, it enters the next process.

[0021] For recalcitrant organic matter and organic matter complexed with heavy metals, high-temperature pyrolysis can effectively break their complexation state and completely remove them, significantly reducing the amount of residual organic impurities in subsequent processes such as dissolution, filtration, neutralization, and degrafting. This weakens the inhibitory effect of organic matter on the crystallization behavior of salt components from the source, reduces the difficulty of industrial waste salt resource utilization, and lays the foundation for obtaining high-purity single salt products in subsequent processes such as salt separation and crystallization. In turn, it promotes the transformation of hazardous waste salt from relying on high-cost or environmentally risky harmless disposal to efficient resource utilization.

[0022] Dissolution and filtration: The hazardous waste salt after high-temperature pyrolysis is put into a dissolution vessel, and fresh water and MVR evaporation condensate are added to dissolve it. The solution is then pumped into a buffer tank and filtered through filter cotton to obtain filtrate and filter residue. The filter residue is disposed of as hazardous waste.

[0023] Neutralization and Heavy Metal Removal: The necessity of a neutralization and heavy metal removal process is determined based on the type of hazardous waste salt. If the aqueous solution of the hazardous waste salt is alkaline and can form metal compound precipitates, then a neutralization and heavy metal removal process is not required. If the aqueous solution of the hazardous waste salt is not alkaline and cannot form metal compound precipitates on its own, then a neutralization and heavy metal removal process is necessary. Specifically, the neutralization and heavy metal removal process involves adding alkaline substances and metal chelating agents to the filtrate to neutralize and form metal compound precipitates, actively promoting the precipitation of metal ions to remove heavy metal impurities from the solution. The filtrate is then filtered through a filter press to remove impurities, yielding filtrate and filter residue. The filter residue is disposed of as hazardous waste, providing a purer filtrate for subsequent processes (such as resin adsorption and crystallization).

[0024] Resin Adsorption: The filtrate is introduced into the adsorption resin to adsorb COD from the filtrate. Specifically, the filtrate is introduced into a resin adsorption tank, primarily composed of anion exchange resin. The resin used is a macroporous adsorption resin, consisting of brownish-brown opaque spherical particles with a particle size of 0.315 mm to 1.25 mm. This ensures sufficient contact with the filtrate while reducing flow resistance and preventing clogging. The moisture content is 50% to 60%, maintaining good resin swelling and facilitating adsorbate diffusion. The wet apparent density is 0.65 to 0.70 g / mL, and the wet true density is 1.05 to 1.10 g / mL, ensuring uniform resin packing in the adsorption column and improving adsorption efficiency. The specific surface area is ≥1200 m². 2 / g provides ample adsorption sites, enabling efficient adsorption of COD and residual organic matter in the filtrate. In particular, it can further reduce the inhibitory effect of recalcitrant organic matter on the crystallization behavior of subsequent salt components, and work with other processes to solve the technical problems caused by the presence of organic matter in the resource utilization of industrial waste salt.

[0025] The adsorption resin is used in multiple batches and is cleaned and regenerated using a 0.8% sodium hydroxide solution. This effectively desorbs COD and recalcitrant organic matter adsorbed by the resin, restoring its adsorption performance, increasing its reusability, and reducing operating costs. Simultaneously, it ensures the resin continuously and efficiently removes organic impurities from the filtrate, preventing residual organic matter from affecting subsequent salt crystallization due to decreased resin adsorption capacity. Combined with the inherent characteristics of the adsorption resin, this further enhances the removal effect on recalcitrant organic matter and complexed impurities, ensuring the stability and efficiency of the entire hazardous waste salt resource recovery process. The cleaning solution is recycled multiple times as makeup water for the spray tower and periodically treated as wastewater in the plant's wastewater treatment plant. A small amount of waste resin is disposed of as hazardous waste.

[0026] Activated carbon adsorption: The filtrate after resin adsorption is introduced into an activated carbon adsorption tank, which is filled with activated carbon. Utilizing the well-developed pore structure and large specific surface area of ​​activated carbon, heavy metal impurities and organic matter in the solution are further removed. The solution is then periodically treated as hazardous waste, and the adsorbed solution proceeds to the next process.

[0027] Cooling crystallization: The decision to perform cooling crystallization on the filtrate after activated carbon adsorption depends on the type of hazardous waste salt. The first wet product and filtrate are obtained through filtration. When the salt components in the hazardous waste salt exhibit a significant difference in solubility with temperature, a cooling crystallization process is necessary. This process utilizes the difference in solubility of different salts in solution with temperature: as the solution cools, salts whose solubility decreases significantly with decreasing temperature will preferentially crystallize out, while salts whose solubility changes less with temperature will remain in the solution, thus achieving the separation of different salt components.

[0028] Precipitation and impurity removal: Depending on the type of hazardous waste salt, it is determined whether to add a suitable reaction solution to the filtrate to produce a precipitate. The filtrate is then filtered to remove impurities, followed by evaporation and crystallization. Precipitation and impurity removal involves adding a reaction solution compatible with the target impurities to the filtrate to cause a chemical reaction between the specific impurities (such as certain ions) in the filtrate and the components in the reaction solution, forming a poorly soluble precipitate. The precipitate (filter residue) is then separated from the solution (filtrate) by filtration, thus removing the impurities. The decision to use this method depends on the type of hazardous waste salt and the characteristics of the impurities in the filtrate during treatment. Specifically, if the filtrate still contains impurities (such as specific ions) that can be chemically converted into precipitates after previous processes (such as dissolution and filtration, neutralization and degraviation, resin adsorption, activated carbon adsorption, and cooling crystallization), and these impurities cannot be effectively removed by existing previous processes, then a precipitation and impurity removal process is required.

[0029] Evaporation and crystallization: The filtrate is heated and evaporated to crystallize. The filtrate is then introduced into an existing MVR evaporation system and concentrated and crystallized at a temperature above 80°C to obtain a second wet product. The MVR evaporation kettle residue is obtained through continuous concentration and disposed of as hazardous waste. The evaporation condensate is condensed and reused in production.

[0030] Flash drying: The first wet product obtained from cooling crystallization and the second wet product obtained from evaporation crystallization are added to a flash dryer for flash drying to obtain the final product, which is then packaged and stored. Using flash drying equipment, no organic waste gas is generated during the drying process.

[0031] Example 1: The hazardous waste salt is dyeing and printing salt and sodium sulfate product hazardous waste salt, with the following composition: Serial Number Substance Name content(%) 1 NaCl 15.72 2 <![CDATA[Na2SO4]]> 52.56 3 <![CDATA[FeCl3]]> 1.24 4 Free water 9.63 5 CaO 0.21 6 MgO 0.13 7 organic matter 10.39 8 Water-insoluble matter 10.07 9 <![CDATA[CdCl2]]> 0.01 10 <![CDATA[PbCl2]]> 0.005 11 <![CDATA[MnCl2]]> 0.015 12 <![CDATA[NiSO4]]> 0.002 13 <![CDATA[ZnSO4]]> 0.008 14 <![CDATA[CrCl3]]> 0.01 15 <![CDATA[HgCl2]]> 0 16 <![CDATA[AsCl3]]> 0 17 total 100 Weightlessness due to burning 9.69 Reference Figure 1 The treatment process for hazardous waste salts such as dyeing and printing salts and sodium sulfate products includes crushing and screening, high-temperature pyrolysis, dissolution and filtration, neutralization and degravation, resin adsorption, activated carbon adsorption, cooling crystallization, evaporation crystallization and flash drying.

[0032] In the neutralization and degravimetric process, NaOH, Na₂CO₃, and a metal chelating agent are added to the filtrate to form a metal compound precipitate. In the cooling crystallization process, the filtrate after activated carbon adsorption is transferred to a crystallization kettle and cooled to 10°C. Sodium sulfate's solubility varies greatly with temperature, while sodium chloride's solubility remains relatively stable. During cooling, a large amount of sodium sulfate precipitates, mixed with a small amount of sodium chloride. Filtration yields the first wet product, sodium sulfate. The evaporation crystallization process yields the second wet product, a wet product of dye salts.

[0033] The following are the pollution-generating points in the treatment of hazardous waste salts from dyeing and printing salts and sodium sulfate products: Figure 1This is a material balance diagram for hazardous waste salts used in printing and dyeing, specifically sodium sulfate products, in t / a. Using 20,000 t / a of waste salt as raw material, the dust collected by the dust collector (315.41 t / a) is completely introduced into the high-temperature pyrolysis process through crushing and screening to avoid material loss. After high-temperature pyrolysis, 90% of the organic matter is removed and further treated in the secondary combustion chamber (removing 99.8%). Simultaneously, the dissolution and filtration process integrates fresh water (6891.55 t / a) and MVR evaporation condensate (17855.84 t / a) to achieve water resource recycling. In the neutralization and heavy metal removal process, the precise addition of NaOH, Na2CO3, and metal chelating agents converts heavy metals such as Fe, Cd, and Pb into hydroxide precipitates (filter residue S1-2 is only 301.25 t / a), significantly reducing impurities entering subsequent systems. A stepped purification process is employed, combining resin adsorption (0.8% NaOH regenerated liquid is circulated as spray makeup water) and activated carbon adsorption. The difference in solubility between sodium sulfate and sodium chloride allows for fractional separation through cooling crystallization (sodium sulfate precipitates at 10℃) and MVR evaporation (sodium chloride is concentrated at above 80℃). Without introducing external chemical separating agents, the final product yields 8475.82 t / a of sodium sulfate and 5289.86 t / a of dye salt, with a resource recovery rate exceeding 68%. Furthermore, multiple stages of material recycling, such as MVR evaporation condensate and resin regeneration cleaning solution, significantly reduce fresh water consumption and hazardous waste generation (total hazardous waste is approximately 3821.83 t / a). The entire process achieves zero discharge of 20,000 t / a of waste salt, recycling of 17,856 t / a of evaporation condensate, and reduction of hazardous solid waste to 3527 t / a, all of which is safely landfilled. This truly realizes a breakthrough in the resource utilization of hazardous waste salt through "high-value, reduced-volume, and harmless" treatment. This application constructs a closed-loop system of "crushing-pyrolysis-dissolution-gravity removal-adsorption-crystallization-evaporation", which breaks through the bottleneck of low resource recovery rate and serious secondary pollution of traditional processes, and forms an integrated technical system of "targeted removal of impurities-graded recovery of resources-recycling of materials".

[0034] Example 2: The hazardous waste salt is a sodium chloride product-type hazardous waste salt, with the following composition: Reference Figure 2 The treatment process for hazardous waste salts such as sodium chloride products includes crushing and screening, high-temperature pyrolysis, dissolution and filtration, neutralization and degravation, resin adsorption, activated carbon adsorption, evaporation and crystallization, and flash drying.

[0035] In the neutralization and degravimetric process, NaOH, 30% hydrochloric acid, and a metal chelating agent are added to the filtrate to form a metal compound precipitate. After resin adsorption and activated carbon adsorption processes, the second wet product, sodium chloride wet product, is obtained solely through evaporation and crystallization.

[0036] The following are the pollution-generating points in the treatment of hazardous waste salts from dyeing and printing salts and sodium sulfate products: Figure 2 This is a material balance diagram for hazardous waste salt of sodium chloride products, in t / a. In this embodiment, through precise material balance control, all dust collected during the crushing and screening stage (containing 259.78 t / a of NaCl, etc.) is returned to the high-temperature pyrolysis process. This allows 58.83% of the NaCl in the raw salt to be recovered as 18108.71 t / a of product through high-temperature pyrolysis (500-700℃) and MVR evaporation (above 80℃), achieving a recovery rate of 92.3%. Simultaneously, a multi-stage purification process (resin adsorption + activated carbon adsorption) deeply removes heavy metals (over 99.8% of elements such as cadmium, manganese, zinc, and chromium enter the neutralization filter residue S2-2), and the MVR evaporation condensate (27040.09 m³) is also recovered. 3 a) All of it is recycled to the dissolving process, with a fresh water consumption of only 7566.02m³. 3 / a, with a water recycling rate of 78.1%, the system ultimately achieves precise separation of organic matter (removal rate of 99.8%), heavy metals, and salt resources in hazardous waste salt. Compared with traditional processes, the system improves the resource recovery rate by more than 15% while reducing the amount of hazardous waste generated to 6990.77t / a, significantly breaking through the technical bottleneck of "low recovery efficiency and heavy secondary pollution" in the process of resource utilization of highly complex hazardous waste salt.

[0037] Example 3: The hazardous waste salt is a product-type hazardous waste salt containing potassium chloride, potassium fluoride, and barium fluoride, with the following composition: Reference Figure 3 The treatment processes for hazardous waste salts such as potassium chloride, potassium fluoride, and barium fluoride include crushing and screening, dissolution and filtration, neutralization and degravation, resin adsorption, activated carbon adsorption, cooling and crystallization, precipitation and impurity removal, evaporation and crystallization, and flash drying.

[0038] In the cooling crystallization process, the filtrate after activated carbon adsorption is transferred to a crystallization kettle and cooled to 10°C. Potassium fluoride's solubility varies greatly with temperature, while potassium chloride's solubility remains relatively stable. During cooling, a large amount of potassium fluoride precipitates, mixed with a small amount of potassium chloride. Filtration yields the first wet product, which is potassium fluoride wet product. In the precipitation and impurity removal process, 30% BaCl2 solution is added to the filtrate to generate barium fluoride precipitate. Filtration removes impurities, yielding filtrate and filter residue. The filter residue is washed with water and dried to obtain barium fluoride byproduct. The filtrate and washing liquid enter a triple-effect evaporation system. The first wet product obtained from cooling crystallization is potassium fluoride wet product, and the second wet product obtained from evaporation crystallization is potassium chloride wet product.

[0039] The pollution-generating points in the treatment of hazardous waste salts such as potassium chloride, potassium fluoride, and barium fluoride are as follows: Figure 3 This is a material balance diagram for hazardous waste salts containing potassium chloride, potassium fluoride, and barium fluoride, in t / a. This embodiment utilizes a precise "stepwise crystallization-precipitation" process design (leveraging the low-temperature precipitation characteristics of potassium fluoride and the directional precipitation of barium fluoride from barium chloride) to convert hazardous waste salts containing 71.41% KCl and 12.36% KF into three qualified products (annual production of 3030.33 tons of KCl, 345.95 tons of KF, and 223.72 tons of BaF2). The overall potassium recovery rate exceeds 99%, while simultaneously achieving nearly 100% resource recovery of fluorine (161.96 tons / year) (KF and BaF2 products) and a closed-loop cycle of chlorine (1459.29 tons / year) (product KCl and safely disposed residue). Integrating multi-stage purification of "neutralization and heavy metal removal - resin / activated carbon adsorption", it concentrates 99.98% of 8 types of heavy metals such as cadmium and lead (annual input of 0.7052 tons) in the neutralization filter residue (S3-2) for safe disposal, with exhaust gas emissions of only 0.0001 tons; furthermore, by reusing evaporative condensate (4635.04 tons / year) and circulating resin regeneration liquid (as spray tower makeup water), it forms a highly efficient reuse of water-alkali media within the system, reducing fresh water consumption by 47%, reducing wastewater discharge from the source, and breaking through the industry bottleneck of incomplete impurity separation and high secondary pollution in hazardous waste salt treatment.

[0040] Example 4: The hazardous waste salt is a product of potassium sulfate and ammonium sulfate, with the following composition: Reference Figure 4 The treatment process for hazardous waste salts such as potassium sulfate and ammonium sulfate includes crushing and screening, dissolution and filtration, neutralization and degravation, resin adsorption, activated carbon adsorption, cooling crystallization, evaporation crystallization and flash drying.

[0041] In the neutralization and degravimetric process, KOH and a metal chelating agent are added to the filtrate to form a metal compound precipitate. In the cooling crystallization process, the filtrate after activated carbon adsorption is transferred to a crystallization kettle and cooled to 10°C. Potassium sulfate's solubility varies greatly with temperature, while ammonium sulfate's solubility remains relatively stable. During cooling, a large amount of potassium sulfate precipitates, mixed with a small amount of ammonium sulfate. Filtration yields the first wet product, which is potassium sulfate. The evaporation crystallization process yields the second wet product, which is ammonium sulfate.

[0042] The following are the pollution-generating points in the treatment of hazardous waste salts from potassium sulfate and ammonium sulfate products: Figure 4 This is a material balance diagram for hazardous waste salts such as potassium sulfate and ammonium sulfate products, in t / a. This example demonstrates the process of using MVR evaporation condensate (recycled water volume 48117.84 m³). 3 / a) Co-reuse with fresh water, combined with multiple batches of 0.8% NaOH resin regenerated liquid as makeup water for the spray tower, significantly improves water resource utilization and reduces wastewater discharge (only 1556.01m). 3 / a Resin regeneration wastewater enters the treatment station), forming a closed-loop water cycle; for the 29.35% K2SO4 and 43.57% (NH4)2SO4 in the hazardous waste salt, the difference in their solubility with temperature is utilized to preferentially separate potassium sulfate through cooling crystallization and recover ammonium sulfate through MVR evaporation crystallization, achieving efficient conversion of the core components; at the same time, solid wastes such as dissolved filter residue (S4-1) and neutralized filter residue (S4-2) are strictly classified as HW49 hazardous waste for standardized disposal, with heavy metals mainly entering the neutralized filter residue (such as cadmium and its compounds, 99.99% of which enter S4-2), and very little exhaust gas emission, achieving synergistic optimization of hazardous waste reduction, resource recovery and pollution control.

[0043] Example 5: The hazardous waste salt is an ammonium chloride product-type hazardous waste salt, with the following composition: Reference Figure 5 The treatment process for hazardous waste salts from ammonium chloride products includes crushing and screening, dissolution and filtration, neutralization and degravation, resin adsorption, activated carbon adsorption, precipitation and impurity removal, evaporation and crystallization, and flash drying.

[0044] In the neutralization and degravimetric process, KOH and a metal chelating agent are added to the filtrate to form a metal compound precipitate. In the precipitation and impurity removal process, 30% CaCl2 solution is added to the filtrate to generate barium sulfate precipitate. After filtration, it is washed with water and dried to obtain barium sulfate byproduct. After filtration and impurity removal, the filtrate and washing liquid enter the evaporation system for further evaporation and crystallization. The second wet product obtained by evaporation and crystallization is ammonium chloride wet product.

[0045] The following are the pollution-generating points in the treatment of hazardous waste salts from ammonium chloride products: Figure 5 This is a material balance diagram for hazardous waste salt containing ammonium chloride, in t / a. This embodiment addresses the easily decomposable nature of 69.61% NH4Cl and ammonium salts in the hazardous waste salt by employing MVR evaporation crystallization (above 80℃) to achieve efficient recovery of ammonium chloride. Simultaneously, the evaporation condensate (6946.50 m³ / h) is recycled. 3 / a) Co-reuse with fresh water, combined with multiple batches of 0.8% NaOH resin regenerated liquid as makeup water for the spray tower, forms a closed-loop water circulation system, significantly reducing water consumption; 30% CaCl2 is added during the precipitation and impurity removal process to generate barium sulfate byproduct, realizing the resource utilization of impurities; and two-stage alkali absorption treatment is used for NH3 waste gas generated during the neutralization process, effectively controlling waste gas emissions; at the same time, solid wastes such as dissolved filter residue (S5-1) and neutralized filter residue (S5-2) are disposed of in accordance with the HW49 hazardous waste standard, with heavy metals mainly entering the neutralized filter residue (such as cadmium and its compounds, 99.98% of which enter S5-2), achieving synergistic optimization of hazardous waste reduction, resource recovery and pollution control.

[0046] Example 6: The hazardous waste salt is an ammonium bicarbonate product-type hazardous waste salt, with the following composition: Reference Figure 6 The treatment process for hazardous waste salts such as ammonium bicarbonate includes crushing and screening, dissolution and filtration, resin adsorption, activated carbon adsorption, evaporation and crystallization, and flash drying. The second wet product obtained from evaporation and crystallization is wet ammonium bicarbonate.

[0047] The following are the pollution-generating points in the treatment of ammonium bicarbonate product-type hazardous waste salts: Figure 6 This is a material balance diagram for hazardous waste salts from ammonium bicarbonate products, in t / a. This example demonstrates the process of using MVR evaporation to collect condensate (recycled water volume 1252.04 m³). 3 / a) Co-reuse with fresh water, combined with multiple batches of 0.8% NaOH resin regenerated liquid as makeup water for the spray tower, significantly improves water resource utilization rate, only 281.46m 3 The resin regeneration wastewater enters the treatment station, forming a closed-loop water circulation system. For the 62.54% NH4HCO3 in the hazardous waste salt, MVR evaporation, concentration, and crystallization are used at temperatures above 80℃. This efficiently recovers ammonium bicarbonate while reducing ammonium salt decomposition losses through precise temperature control. Meanwhile, solid wastes such as dissolved filter residue (S6-1) and waste resin (S6-2) are disposed of in accordance with the HW49 hazardous waste standard. The waste gas from crushing, screening, and flash drying is treated by a bag filter and then discharged in compliance with standards. This achieves synergistic optimization of hazardous waste reduction, resource recovery, and pollution control.

[0048] Example 7: The hazardous waste salt is a sodium phosphate product-type hazardous waste salt, with the following composition: Serial Number Substance Name content(%) 1 <![CDATA[Na3PO4]]> 61.56 2 <![CDATA[Na2HPO4]]> 4 3 <![CDATA[NaH2PO4]]> 2.53 4 Free water 10.02 5 <![CDATA[Ca3(PO4)2]]> 0.85 6 <![CDATA[Mg3(PO4)2]]> 2.38 7 organic matter 12.21 8 Water-insoluble matter 6.449 9 <![CDATA[CdCl2]]> 0 10 <![CDATA[PbCl2]]> 0 11 <![CDATA[MnCl2]]> 0 12 <![CDATA[NiSO4]]> 0 13 <![CDATA[ZnSO4]]> 0.001 14 <![CDATA[CrCl3]]> 0 15 <![CDATA[HgCl2]]> 0 16 <![CDATA[AsCl3]]> 0 17 total 100 Reference Figure 7The treatment process for hazardous waste salts such as sodium phosphate includes crushing and screening, high-temperature pyrolysis, dissolution and filtration, resin adsorption, activated carbon adsorption, evaporation and crystallization, and flash drying. The second wet product obtained from evaporation and crystallization is wet sodium phosphate.

[0049] The following are the pollution-generating points in the treatment of hazardous waste salts from sodium phosphate products: Figure 7 This is a material balance diagram for hazardous waste salts containing sodium phosphate products, in t / a. This embodiment addresses the high organic matter content (12.21%) in the hazardous waste salts by innovatively employing a combined process of high-temperature pyrolysis (500℃~700℃ to remove 90% of organic matter) and a secondary combustion chamber (1100~1200℃, residence time 3s, removing 99.8% of organic matter). This significantly reduces the load on subsequent treatment. The desorbed waste gas undergoes multi-stage treatment (bag filter + two-stage alkaline scrubbing, etc.) to meet emission standards. Condensate is evaporated via MVR (1741.90 m³ of recycled water). 3 / a) Co-reuse with fresh water, combined with 0.8% NaOH resin regenerated liquid as makeup water for the spray tower, only 47.98m 3 / a Resin regeneration wastewater enters the treatment station, forming an efficient water cycle; at the same time, solid wastes such as dissolved filter residue (S7-1) and waste resin (S7-2) are disposed of in accordance with the HW49 hazardous waste standard, and flash drying exhaust gas is treated by cyclone + bag dust collection, realizing a deep synergy of reduction, resource utilization and pollution control of high organic hazardous waste.

[0050] This application does not use volatile solvents in the production process. The organic matter is mainly generated during high-temperature pyrolysis and enters the secondary combustion chamber for treatment. Under the conditions of 1100℃ and residence time ≥2S, secondary combustion can remove 99.8% of the organic matter. At the same time, the generation of dioxins is controlled from both the source and the production process. The combustion exhaust gas is treated by SNCR denitrification + quench tower + activated carbon jet adsorption + bag filter + two-stage alkaline spraying to ensure that the emission of organic waste gas meets the standards.

[0051] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A process for the resource utilization of hazardous waste salt, characterized in that, Includes the following steps, Crushing and screening: The hazardous waste salt is crushed and dusted, and pulverized to below the preset particle size; High-temperature pyrolysis: Determine whether to perform high-temperature pyrolysis based on the type of hazardous waste salt in order to remove organic matter; Dissolution and filtration: Add fresh water and MVR evaporation condensate to the hazardous waste salt to dissolve it, and filter to remove impurities to obtain the filtrate; Neutralization and weight removal: Depending on the type of hazardous waste salt, determine whether to add alkaline substances and metal chelating agents to the filtrate to neutralize and form metal compound precipitates, then filter to remove impurities and obtain the filtrate; Resin adsorption: The filtrate is introduced into the adsorption resin to adsorb COD in the filtrate; Activated carbon adsorption: The filtrate after resin adsorption is subjected to activated carbon adsorption to remove heavy metal impurities and organic matter from the filtrate; Cooling crystallization: Determine whether to cool and crystallize the filtrate after activated carbon adsorption based on the type of hazardous waste salt. The first wet product and filtrate are obtained by filtration. Precipitation and impurity removal: Depending on the type of hazardous waste salt, determine whether to heat a suitable reaction solution into the filtrate to produce precipitate, filter to remove impurities to obtain the filtrate, and then carry out the evaporation and crystallization process; Evaporation and crystallization: The filtrate is heated and evaporated to crystallize, yielding a second wet product; Flash drying: The first wet product obtained by cooling crystallization and the second wet product obtained by evaporation crystallization are flash dried.

2. The hazardous waste salt resource utilization treatment process according to claim 1, characterized in that, In the resin adsorption process, the adsorption resin used is brownish-brown opaque spherical particles with a particle size of 0.315 mm to 1.25 mm, a moisture content of 50% to 60%, a wet apparent density of 0.65 to 0.70 g / mL, a wet true density of 1.05 to 1.10 g / mL, and a specific surface area ≥ 1200 m². 2 / g.

3. The hazardous waste salt resource utilization treatment process according to claim 2, characterized in that, The resin adsorption process also includes cleaning and regenerating the adsorption resin using a 0.8% sodium hydroxide solution.

4. The hazardous waste salt resource utilization treatment process according to claim 1, characterized in that, In the high-temperature pyrolysis process, the heating temperature is 500~700℃, so that more than 90% of the organic matter in the hazardous waste salt is released in the form of organic waste gas. Oxygen is introduced for heating, and the heating temperature is 1100~1200℃ to remove more than 99.8% of the organic matter.

5. The hazardous waste salt resource utilization treatment process according to claim 1, characterized in that, When the hazardous waste salt is dyeing and printing salt or sodium sulfate product hazardous waste salt, a high-temperature pyrolysis process is carried out after crushing and screening, a neutralization and degravimetric process is carried out after dissolution and filtration, and a cooling and crystallization process is carried out after activated carbon adsorption. No precipitation and impurity removal process is carried out. The first wet product obtained by cooling crystallization is sodium sulfate wet product, and the second wet product obtained by evaporation crystallization is dye salt wet product.

6. The hazardous waste salt resource utilization treatment process according to claim 1, characterized in that, When the hazardous waste salt is sodium chloride product, a high-temperature pyrolysis process is carried out after crushing and screening, a neutralization and degravimetric process is carried out after dissolution and filtration, and no cooling crystallization and precipitation impurity removal process is carried out after activated carbon adsorption. The second wet product, sodium chloride wet product, is obtained only through evaporation and crystallization.

7. The hazardous waste salt resource utilization treatment process according to claim 1, characterized in that, When the hazardous waste salt is potassium chloride, potassium fluoride, or barium fluoride, no high-temperature pyrolysis process is carried out after crushing and screening. After dissolution and filtration, a neutralization and degravimetric process is carried out. After activated carbon adsorption, a cooling crystallization, precipitation, and impurity removal process is carried out. In the precipitation and impurity removal process, barium chloride solution is added to the filtrate to produce barium fluoride precipitate. After filtration to remove impurities, the filtrate is then subjected to an evaporation and crystallization process. The first wet product obtained by cooling crystallization is potassium fluoride wet product, and the second wet product obtained by evaporation crystallization is potassium chloride wet product.

8. The hazardous waste salt resource utilization treatment process according to claim 1, characterized in that, When the hazardous waste salt is potassium sulfate or ammonium sulfate product hazardous waste salt, after crushing and screening, a high-temperature pyrolysis process is not carried out; after dissolution and filtration, a neutralization and degravimetric process is carried out; after activated carbon adsorption, a cooling and crystallization process is carried out; and no precipitation and impurity removal process is carried out. The first wet product obtained by cooling crystallization is potassium sulfate wet product, and the second wet product obtained by evaporation crystallization is ammonium sulfate wet product.

9. The hazardous waste salt resource utilization treatment process according to claim 1, characterized in that, When the hazardous waste salt is ammonium chloride product type hazardous waste salt, after crushing and screening, a high-temperature pyrolysis process is not carried out; after dissolution and filtration, a neutralization and degravimetric process is carried out; after activated carbon adsorption, a cooling and crystallization process is not carried out; instead, a precipitation and impurity removal process is carried out. In the precipitation and impurity removal process, calcium chloride solution is added to the filtrate to generate barium sulfate precipitate. After filtration to remove impurities, the filtrate is then subjected to an evaporation and crystallization process. The second wet product obtained by evaporation and crystallization is ammonium chloride wet product.

10. The hazardous waste salt resource utilization treatment process according to claim 1, characterized in that, When the hazardous waste salt is ammonium bicarbonate product-type hazardous waste salt, no high-temperature pyrolysis process is performed after crushing and screening; no neutralization and degravimetric process is performed after dissolution and filtration; and no cooling crystallization, precipitation, or impurity removal process is performed after activated carbon adsorption. The second wet product obtained from evaporation and crystallization is wet ammonium bicarbonate. Alternatively, When the hazardous waste salt is sodium phosphate product, a high-temperature pyrolysis process is carried out after crushing and screening. After dissolution and filtration, no neutralization and degravimetric process is carried out. After activated carbon adsorption, no cooling crystallization and precipitation impurity removal process is carried out. The second wet product obtained by evaporation and crystallization is sodium phosphate wet product.

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