Hydrogen fluoride production solid waste comprehensive treatment method

Abstract

The present application relates to the field of hazardous solid waste treatment, in particular to a comprehensive treatment method for hydrogen fluoride production solid waste, which comprises four main steps: mixed solid waste grading pretreatment, fluorogypsum, fluorine-containing waste residue and waste catalyst are crushed to a particle size of less than or equal to 10 mm, and impurities are removed through double-layer vibration screening and magnetic separation, fluorine-containing waste residue and fluorogypsum mixture are separated from waste catalyst, and defluorination treatment is carried out in cooperation, fluorine ions are removed by using a two-step method of primary acid leaching and secondary alkali regulation, ammonium fluoride solution is generated, HF tail gas is absorbed by ammonia water, resources are recovered in a graded manner, filter residue A is washed and dried to obtain refined calcium sulfate, fluorine-containing waste residue is ground and then reacted with hydrochloric acid to prepare fluorite powder, filter liquor A is adjusted in pH and then evaporated, concentrated and crystallized to obtain ammonium fluoride crystals, waste catalyst is solidified in a harmless manner, Al(OH)3 precipitate is mixed with cement and phosphate to form a stable solidified body, and after curing, it is safely landfilled, which is suitable for hydrogen fluoride production enterprises to realize clean production and resource recovery.

Description

Technical Field

[0001] This invention relates to the field of hazardous solid waste treatment technology, specifically a comprehensive treatment method for solid waste from hydrogen fluoride production. Background Technology

[0002] The production of hydrogen fluoride generates a large amount of solid waste, mainly including fluorogypsum, fluorine-containing waste residue, and spent catalysts. This solid waste not only occupies significant land resources but also contains high levels of fluorine and other harmful components; improper handling will cause serious environmental pollution. Traditional solid waste treatment methods mainly include landfilling, simple stockpiling, or partial recycling, but these methods have many shortcomings.

[0003] Direct landfilling or dumping not only wastes land resources but also causes fluoride ions to seep into the soil and groundwater, resulting in environmental pollution. Furthermore, heavy metals that may be present in spent catalysts can be washed into the environment by rainwater, increasing ecological risks.

[0004] Although some companies have attempted to recycle fluorogypsum and fluorine-containing waste through simple physical or chemical methods, such as for use in building materials or for the preparation of low-grade products, the lack of effective pretreatment and grading measures often makes it difficult to obtain high-purity useful components, thus limiting their application scope and economic value.

[0005] The HF tail gas in the hydrogen fluoride production process is usually treated by alkaline absorption. However, the HF absorption efficiency in the traditional process is not high, which can easily cause secondary pollution and does not fully recover HF resources, thus reducing the overall economic benefits.

[0006] Existing technologies have failed to effectively separate and recover valuable elements such as calcium and fluorine from solid waste, resulting in the waste of a large amount of valuable resources. Summary of the Invention

[0007] (a) Technical problems to be solved

[0008] To address the shortcomings of existing technologies, this invention provides a comprehensive treatment method for solid waste from hydrogen fluoride production.

[0009] (II) Technical Solution

[0010] To achieve the above objectives, the present invention provides the following technical solution: A comprehensive treatment method for solid waste from hydrogen fluoride production according to the present invention includes the following steps:

[0011] Step 1: Pre-treatment of mixed solid waste classification. The mixed solid waste of fluorogypsum, fluorine-containing waste residue and waste catalyst generated from hydrogen fluoride production is crushed to a particle size of ≤10mm and classified by a double-layer vibrating screen. The upper layer is fluorine-containing waste residue and the lower layer is a mixture of fluorogypsum and waste catalyst. The lower layer mixture is magnetically separated to remove impurities.

[0012] The mass ratio of the mixed solid waste is 70%-80% fluorogypsum, 15%-20% fluorine-containing waste residue, and 5%-10% waste catalyst.

[0013] Step 2: Co-processing defluorination. In the first-stage acid leaching section, the lower layer mixture is fed into an acid-resistant reactor, and 5%-8% dilute sulfuric acid is added at a liquid-to-solid ratio of 3:1. The reaction proceeds for 60-90 minutes. After the first-stage acid leaching defluorination, the HF tail gas is absorbed by 10% ammonia water to generate ammonium fluoride. In the second-stage alkali control section, 5%-8% (by weight of solid waste) of calcium hydroxide is added to the reaction solution to adjust the pH to 6.0-7.0. The reaction proceeds for 40-60 minutes. After the second-stage alkali control defluorination, solid and liquid separation yields filter residue A and filtrate A.

[0014] Step 3: Resource separation and recovery. Filter residue A is washed and dried to obtain refined calcium sulfate; the upper fluorine-containing waste residue is ground to ≤0.1mm, reacted with 10%-12% hydrochloric acid for 30-40min, filtered, washed and dried to obtain fluorite powder; filtrate A is adjusted to pH 8.0-9.0 with ammonia water to generate Al(OH)3 precipitate; the combined liquid is evaporated and concentrated under the following conditions: temperature 80-85℃, vacuum degree -0.08MPa, cooling crystallization temperature 20-25℃, centrifugation speed 3000r / min; after filtration, the filtrate is combined with the ammonium fluoride absorption liquid, evaporated, concentrated and crystallized to obtain ammonium fluoride crystals;

[0015] Step 4: Harmless solidification of waste catalyst. The Al(OH)3 precipitate obtained from filtration in Step 3 is mixed with cement, water, and 0.5%-1% phosphate, cured at room temperature for 7 days to form a solidified body, and then landfilled after passing the test.

[0016] The washing wastewater and filtration mother liquor from steps 2-3 are combined and reused in the primary acid leaching section.

[0017] More preferably, in step 2, the concentration of dilute sulfuric acid in the primary acid leaching is adjusted according to the fluorine content of the mixed solid waste: the concentration is 7%-8% when the fluorine content is >5%, and the concentration is 5%-6% when the fluorine content is ≤5%; the purity of calcium hydroxide controlled by the secondary alkali is ≥95%, and the reaction temperature is adjusted in real time according to the pH, with a temperature increase of 5-10℃ when the pH is <6.0.

[0018] Preferably, in step 2, the HF tail gas absorption tower is a packed tower with an absorption temperature of 25-30℃, and the ammonia water flow rate is automatically adjusted according to the HF concentration of the tail gas to ensure that the ammonium fluoride solution concentration is 20%-25%.

[0019] Preferably, in step 3, filter residue A is washed three times with deionized water at a liquid-to-solid ratio of 2:1, and the fluoride content of the filter residue after washing is ≤0.1%; drying is carried out using a rotary dryer at a temperature of 120-150℃, and the moisture content is controlled at ≤5%.

[0020] More preferably, in step 3, the fluorine-containing waste residue is ground using a ball mill for 30-40 minutes; the filter residue after hydrochloric acid reaction is washed with deionized water to pH 6.5-7.5 and dried at 100-120℃.

[0021] Preferably, in step 4, the phosphate is diammonium dihydrogen phosphate or diammonium hydrogen phosphate, and the cement is P.O42.5 ordinary silicate cement; the curing environment of the solidified body is a temperature of 20-25℃ and a relative humidity of ≥90%, and the heavy metal leaching concentration after curing is: Pb≤0.05mg / L, As≤0.03mg / L.

[0022] (III) Beneficial Effects

[0023] Compared with the prior art, the present invention provides a comprehensive treatment method for solid waste from hydrogen fluoride production, which has the following beneficial effects:

[0024] This technical solution employs a graded pretreatment process for mixed solid waste, crushing and grading fluorogypsum, fluorine-containing waste residue, and spent catalyst to effectively separate different components, laying the foundation for subsequent treatment. Magnetic separation further enhances material purity and reduces the impact of impurities on subsequent processes.

[0025] In the synergistic defluorination process, a two-stage chemical treatment method is employed. The first stage uses dilute sulfuric acid for defluorination, and the HF tail gas is absorbed by ammonia water to generate ammonium fluoride, achieving effective waste gas recovery and utilization. In the second stage, calcium hydroxide is added to adjust the pH value, further removing fluoride ions and ensuring that the fluoride content in the final filter residue A is reduced to a safe level. Furthermore, the acid concentration and reaction temperature are adjusted according to the fluoride content to optimize the defluorination effect and improve resource utilization.

[0026] In the resource recycling process, the preparation of refined calcium sulfate, fluorite powder, and ammonium fluoride crystals not only achieves efficient conversion of solid waste but also generates high-value-added products. For example, the upper layer of fluorine-containing waste residue is ground and treated with hydrochloric acid to obtain pure fluorite powder; filtrate A is adjusted to pH with ammonia water, then evaporated, concentrated, and crystallized to obtain ammonium fluoride crystals. The entire process fully embodies the concept of resource recycling.

[0027] The harmless solidification of waste catalyst is a major highlight of this technical solution. After Al(OH)3 precipitate is mixed with cement and phosphate, it forms a stable solid body. After curing, the concentration of heavy metal leaching is far below the environmental protection standard, making it suitable for safe landfill and avoiding the risk of secondary pollution.

[0028] Furthermore, the design of reusing washing wastewater and filtration mother liquor in the primary acid leaching section significantly reduces water consumption and wastewater discharge, thereby lowering overall operating costs. This technical solution integrates multiple processes, including staged pretreatment, chemical defluorination, resource recovery, and harmless disposal, forming a complete solid waste treatment system suitable for hydrogen fluoride production enterprises to achieve clean production and a circular economy. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the overall process architecture of the present invention;

[0030] Figure 2 This is a schematic diagram of the mixed solid waste graded pretreatment architecture of the present invention;

[0031] Figure 3 This is a schematic diagram of the first-stage acid leaching section of the present invention;

[0032] Figure 4 This is a schematic diagram of the secondary alkali regulation section and solid-liquid separation architecture of the present invention;

[0033] Figure 5 This is a schematic diagram of the fluorite powder recovery architecture of the present invention;

[0034] Figure 6 This is a schematic diagram of the ammonium fluoride crystal recovery architecture of the present invention;

[0035] Figure 7 This is a schematic diagram of the waste catalyst harmless solidification structure of the present invention;

[0036] Figure 8 This is a schematic diagram of the wastewater recycling architecture of the present invention; Detailed Implementation

[0037] 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.

[0038] Please see Figure 1-8 The present invention provides a comprehensive treatment method for solid waste from hydrogen fluoride production, comprising the following steps:

[0039] Step 1: Pre-treatment of mixed solid waste classification. The mixed solid waste of fluorogypsum, fluorine-containing waste residue and waste catalyst generated from hydrogen fluoride production is crushed to a particle size of ≤10mm and classified by a double-layer vibrating screen. The upper layer is fluorine-containing waste residue and the lower layer is a mixture of fluorogypsum and waste catalyst. The lower layer mixture is magnetically separated to remove impurities.

[0040] Step 2: Co-processing defluorination. In the first-stage acid leaching section, the lower layer mixture is fed into an acid-resistant reactor, and 5%-8% dilute sulfuric acid is added at a liquid-to-solid ratio of 3:1. The reaction proceeds for 60-90 minutes. After the first-stage acid leaching defluorination, the HF tail gas is absorbed by 10% ammonia water to generate ammonium fluoride. In the second-stage alkali control section, 5%-8% (by weight of solid waste) of calcium hydroxide is added to the reaction solution to adjust the pH to 6.0-7.0. The reaction proceeds for 40-60 minutes. After the second-stage alkali control defluorination, solid and liquid separation yields filter residue A and filtrate A.

[0041] Step 3: Resource separation and recovery. Filter residue A is washed and dried to obtain refined calcium sulfate; the upper fluorine-containing waste residue is ground to ≤0.1mm, reacted with 10%-12% hydrochloric acid for 30-40min, filtered, washed and dried to obtain fluorite powder; filtrate A is adjusted to pH 8.0-9.0 with ammonia water, filtered and combined with ammonium fluoride absorption liquid, evaporated, concentrated and crystallized to obtain ammonium fluoride crystals;

[0042] Step 4: Harmless solidification of waste catalyst. The Al(OH)3 precipitate obtained from filtration in Step 3 is mixed with cement, water, and 0.5%-1% phosphate, cured at room temperature for 7 days to form a solidified body, and then landfilled after passing the test.

[0043] This technical solution separates solid wastes of different particle sizes and compositions through graded pretreatment. For example, coarse particles of fluorine-containing waste residue are recovered separately as fluorite, while fine particles of fluorogypsum and spent catalyst are synergistically defluorinated to avoid component interference. Based on the existing forms of fluorine, such as free fluorine, lattice-bound fluorine, and compound-bound fluorine, a step-by-step reaction is adopted, involving first-stage acid leaching to remove free fluorine and second-stage alkali regulation to remove lattice-bound fluorine, to directionally destroy the fluorine binding structure and achieve a defluorination rate of ≥99%. Utilizing the differences in physicochemical properties of calcium sulfate, fluorite, and ammonium fluoride, they are recovered separately through washing, drying, and crystallization, achieving a resource recovery rate of ≥95%. Finally, heavy metals in the spent catalyst are physically encapsulated and chemically fixed through cement and phosphate systems to ensure that the leaching concentration of the solidified body meets the standards, achieving full-process environmental protection and resource recycling.

[0044] Particle size classification and component separation

[0045] Mixed solid waste, such as 70%-80% fluorogypsum, 15%-20% fluorine-containing waste residue, and 5%-10% spent catalyst, is crushed to ≤10mm and then classified using a double-layer vibrating screen based on differences in particle size and density: the fluorine-containing waste residue, with larger particles (>screen mesh size), remains in the upper layer, while the fluorogypsum and spent catalyst, with smaller particles (≤screen mesh size), fall to the lower layer. This design is based on the differences in the physical characteristics of the three types of solid waste: fluorine-containing waste residue is mostly lumpy impurities, fluorogypsum is fine powder, and spent catalyst is granular. This initial component separation lays the foundation for subsequent targeted treatment.

[0046] Magnetic separation principle

[0047] The mixture of lower-layer fluorogypsum and spent catalyst is passed through a magnetic separator. The magnetic properties of any ferromagnetic impurities, such as metal fragments, that may be present in the spent catalyst are adsorbed and separated under the influence of a magnetic field. This prevents impurities from affecting the efficiency of subsequent acid leaching reactions and the purity of the products, thus ensuring the stability of the subsequent treatment system.

[0048] Primary acid leaching for defluorination

[0049] Chemical Mechanism: Adding 5%-8% dilute sulfuric acid to an acid-resistant reactor (e.g., a liquid-to-solid ratio of 3:1) allows the sulfuric acid to react with fluorides in fluorogypsum, such as CaF2: CaF2 + H2SO4 → CaSO4 + 2HF↑. Simultaneously, soluble fluorides in the spent catalyst also react with the sulfuric acid, releasing HF gas. By controlling the sulfuric acid concentration—7%-8% when the fluorine content is >5%, and 5%-6% when ≤5%—efficient conversion of fluorides and removal of HF are achieved. A reaction time of 60-90 minutes ensures complete reaction.

[0050] Tail gas absorption principle: HF tail gas is introduced into a packed tower and absorbed with 10% ammonia water, resulting in the reaction: HF + NH3·H2O → NH4F + H2O. The packing material inside the tower, such as polypropylene corrugated packing, increases the gas-liquid contact area, controls the absorption temperature at 25-30℃ to prevent excessive ammonia evaporation, and automatically adjusts the ammonia water flow rate according to the HF concentration in the tail gas to ensure the ammonium fluoride solution concentration remains stable at 20%-25%, thus achieving the resource recovery of HF.

[0051] Secondary alkali regulation for defluorination

[0052] pH adjustment and fluorine fixation: Add calcium hydroxide with a purity of ≥95% to the primary acid leaching reaction solution. On the one hand, adjust the pH to 6.0-7.0 to neutralize excess sulfuric acid; on the other hand, Ca²⁺ combines with residual F⁻ in the solution to form insoluble CaF₂ precipitate, further reducing the fluorine content.

[0053] Temperature-coordinated regulation: When pH < 6.0, increase the temperature by 5-10℃, such as from room temperature to 30-35℃, to accelerate the dissolution of calcium hydroxide and the formation of CaF2 precipitate, ensuring that the pH remains stable within the target range and improving defluorination efficiency.

[0054] Solid-liquid separation: Filtering, such as using a plate and frame filter press, yields filter residue A, which mainly consists of CaSO4 and filtrate A, containing Al³⁺, a small amount of F⁻, etc., thus achieving the component separation of the solid-liquid system.

[0055] Resource classification and recycling principle

[0056] Refined calcium sulfate recovery, filter residue A treatment

[0057] Washing and defluorination: Filter residue A is washed three times with deionized water at a liquid-to-solid ratio of 2:1. The dissolving effect of water is used to remove soluble fluorides adhering to the surface of CaSO4, ensuring that the fluoride content of the filter residue after washing is ≤0.1%, thus avoiding fluoride residue from affecting product quality.

[0058] Drying and shaping: A rotary dryer is used to dry the filter residue at a temperature of 120-150℃. The moisture content is removed by heat conduction and hot air convection, and the moisture content is controlled to be ≤5%, so as to obtain refined calcium sulfate with high purity and good stability, which can be used in building gypsum, putty powder and other fields.

[0059] Fluorite powder recovery and treatment of upper fluorine-containing waste residue

[0060] Grinding and refining: The upper layer of fluorine-containing waste residue is ground in a ball mill for 30-40 minutes until the particle size is ≤0.1mm, increasing the specific surface area and providing sufficient contact sites for the subsequent hydrochloric acid reaction.

[0061] Acid dissolution and purification: Add 10%-12% hydrochloric acid and react for 30-40 minutes. The hydrochloric acid reacts with impurities such as Fe2O3 and Al2O3 in the waste residue to form soluble salts such as FeCl3 and AlCl3, while the main component CaF2 does not react with hydrochloric acid. After filtration, wash the filter residue with deionized water until the pH reaches 6.5-7.5 to remove residual hydrochloric acid and soluble salts. After drying at 100-120℃, high-purity fluorite powder with a CaF2 content ≥95% is obtained, which can be reused as a raw material for hydrogen fluoride production.

[0062] Ammonium fluoride recovery and filtrate treatment

[0063] Al(OH)3 precipitation separation: Add ammonia to filtrate A to adjust the pH to 8.0-9.0. Al³⁺ and OH⁻ in the solution combine to form Al(OH)3 precipitate. Filter to separate Al(OH)3 precipitate and filtrate containing NH⁺ and F⁻.

[0064] Evaporation, concentration, and crystallization: The above filtrate is combined with the ammonium fluoride solution obtained from HF tail gas absorption, and evaporated and concentrated at 80-85℃ and a vacuum of -0.08MPa. The vacuum environment lowers the boiling point of the solution, prevents the decomposition of ammonium fluoride, and removes excess water. Subsequently, it is cooled and crystallized at 20-25℃, taking advantage of the characteristic that the solubility of ammonium fluoride decreases with decreasing temperature to precipitate crystals. Finally, ammonium fluoride crystals are obtained by centrifugation at 3000 r / min, which can be used in agricultural fertilizers, industrial etching agents, etc.

[0065] The principle of harmless solidification of waste catalysts

[0066] Cementation and solidification mechanism: Al(OH)3 precipitate is mixed with P.O42.5 ordinary silicate cement, water and 0.5%-1% phosphate. The cement hydrates to form calcium silicate hydrate (CSH) gel, and Al(OH)3 reacts with phosphate to form aluminum phosphate salt, such as AlPO4. The two together form a dense solidified structure, which encapsulates and fixes heavy metals such as Pb and As in the waste catalyst, preventing them from leaching.

[0067] Curing and stability control: Curing for 7 days at a temperature of 20-25℃ and a relative humidity of ≥90% ensures that the cement is fully hydrated and reacts completely with the aluminum phosphate salt to form a solidified body with high strength and good stability. The test results show that the leaching concentration of heavy metals in the solidified body is: Pb≤0.05mg / L and As≤0.03mg / L, which meets the requirements of the "Standard for Pollution Control of Hazardous Waste Landfill" (GB18598-2019) and can be safely landfilled.

[0068] Wastewater recycling principle

[0069] The washing wastewater in steps 2-3, such as the washing water of filter residue A and the washing water of fluorite powder, is combined with the mother liquor of filtration, such as the mother liquor of crystallization centrifugation. Since it contains unreacted sulfuric acid, hydrochloric acid and soluble fluoride, it is reused in the primary acid leaching section as a supplement to the reaction liquid. On the one hand, it reduces the amount of fresh water used, and on the other hand, it increases the utilization rate of acid and fluoride, reduces the amount of wastewater discharged, and realizes a circular economy model of treating waste with waste.

[0070] Detailed Workflow

[0071] Phase 1: Pre-treatment of mixed solid waste

[0072] Crushing process: Mixed solid waste generated from hydrogen fluoride production, such as 70%-80% fluorogypsum, 15%-20% fluorine-containing waste residue, and 5%-10% waste catalyst, is fed into a jaw crusher, such as the PEX150×750 model, to crush it to a particle size ≤10mm to ensure the efficiency of subsequent classification.

[0073] Double-layer vibrating screen: The crushed solid waste is fed into a double-layer vibrating screen, such as the ZS1000×2000 type. The upper screen has a mesh size of 10mm and the lower screen has a mesh size of 5mm. The upper layer retains fluorine-containing waste residue with a particle size >10mm, and the lower layer collects a mixture of fluorogypsum and waste catalyst with a particle size ≤10mm.

[0074] Magnetic separation for impurity removal: The lower layer mixture is fed into a permanent magnet drum separator, such as the CTB1018 model, with a magnetic field strength of 12000Gs, to remove ferromagnetic impurities and obtain a purified mixture of fluorogypsum and waste catalyst for later use.

[0075] Phase 2: Co-treatment with defluorination

[0076] First-stage acid leaching reaction: The purified mixture is put into an acid-resistant reactor, such as a 5000L enamel reactor, model F. Dilute sulfuric acid is added at a liquid-to-solid ratio of 3:1. The concentration is adjusted according to the fluorine content: when the fluorine content is >5%, the dilute sulfuric acid is 7%-8%; when the fluorine content is ≤5%, the dilute sulfuric acid is 5%-6%. The stirring speed is 300r / min, and the reaction is carried out for 60-90min. The generated HF tail gas is introduced into the packed tower through a pipeline.

[0077] HF tail gas absorption: Packed tower, such as DN800 polypropylene packed tower, filled with 50mm polypropylene corrugated packing, 10% ammonia water is introduced into the middle, the absorption temperature is controlled at 25-30℃, the tail gas concentration is monitored in real time by an online HF concentration detector, such as GHF-3000, and the ammonia water flow rate is automatically adjusted. If controlled by an electromagnetic flow meter, the outlet HF concentration is ensured to be ≤10mg / m³. The absorption liquid is a 20%-25% ammonium fluoride solution, which is collected for later use.

[0078] Secondary alkali regulation reaction: Add calcium hydroxide with a purity of ≥95% to the acid leaching reaction solution, turn on the pH online monitoring instrument, such as the PHS-3C type, and when the pH <6.0, raise the temperature by 5-10℃ through the heating mantle and stir the reaction for 40-60 minutes until the pH stabilizes at 6.0-7.0.

[0079] Solid-liquid separation: The reaction solution is sent to a plate and frame filter press, such as the XMYZ100 / 1000-30U type, and filtered to obtain filter residue A, which is mainly CaSO4, and filtrate A, which contains Al³⁺, F⁻, etc. Filtrate A is collected in a storage tank.

[0080] Phase 3: Resource Differentiation and Recycling

[0081] Preparation of refined calcium sulfate:

[0082] Filter residue A was sent to a washing tank and washed three times with deionized water at a liquid-to-solid ratio of 2:1, with stirring for 30 minutes each time. After washing, the fluoride content of the filter residue was tested and found to be ≤0.1%.

[0083] The washed filter residue is sent to a rotary dryer, such as a Φ1.2×12m type, with a hot air temperature of 120-150℃, and dried until the moisture content is ≤5%, to obtain refined calcium sulfate product, which is then packaged and stored.

[0084] Preparation of fluorite powder:

[0085] The upper layer of fluorine-containing waste residue is fed into a ball mill, such as the MQG2100×4500 type, with a steel ball filling rate of 40%, and ground for 30-40 minutes until the particle size is ≤0.1mm;

[0086] The ground waste residue is put into the reaction tank, and 10%-12% hydrochloric acid is added at a liquid-solid ratio of 4:1. The mixture is stirred and reacted for 30-40 minutes, and then filtered to obtain the filter residue.

[0087] The filter residue is washed with deionized water until the pH reaches 6.5-7.5, and then sent to a chamber dryer, such as the CT-C type, to dry at a temperature of 100-120℃ to obtain fluorite powder product for later use.

[0088] Preparation of ammonium fluoride:

[0089] Add ammonia water dropwise to the filtrate A storage tank to adjust the pH to 8.0-9.0, stir for 30 min to generate Al(OH)3 precipitate, and filter to separate Al(OH)3 precipitate and filtrate;

[0090] The filtrate is combined with the ammonium fluoride solution obtained from HF tail gas absorption and sent to a double-effect evaporator, such as the MVR2000 model, at a temperature of 80-85℃ and a vacuum of -0.08MPa, to concentrate to a solid content of 30%-35%.

[0091] The concentrate is fed into a cooling crystallizer, such as the OSLO type, at a temperature of 20-25℃. After crystallization for 4 hours, it is fed into a horizontal screw discharge centrifuge, such as the LW450×1800 type, at a speed of 3000 r / min for separation to obtain ammonium fluoride crystals. After drying in a fluidized bed dryer, such as the FG120 type, the crystals are packaged.

[0092] Phase 4: Harmless solidification of spent catalysts

[0093] Preparation of curing mixture: Al(OH)3 precipitate, P.O42.5 ordinary silicate cement, and deionized water are mixed in a mass ratio of 1:3:1. Add 0.5%-1% of ammonium dihydrogen phosphate or diammonium hydrogen phosphate and stir in a forced mixer, such as a JS500 model, for 15 minutes to form a uniform curing slurry.

[0094] Molding and curing: Pour the solidified slurry into a mold, such as a mold with a size of 50mm×50mm×50mm, vibrate it to make it dense, and then place it in a curing room at a temperature of 20-25℃ and a relative humidity of ≥90% for 7 days.

[0095] Testing and Landfilling: After curing, samples are taken and the leaching concentration of heavy metals is tested according to the "Solid Waste Leaching Toxicity Leaching Method - Sulfuric Acid and Nitric Acid Method" (HJ / T299-2007). If Pb≤0.05mg / L and As≤0.03mg / L, the sample is deemed qualified and sent to a hazardous waste landfill for safe landfilling.

[0096] Phase 5: Wastewater Recycling

[0097] The washing wastewater of filter residue A in step 2, the washing wastewater of fluorite powder in step 3, and the centrifugal mother liquor of ammonium fluoride crystallization are collected in the wastewater equalization tank. After filtering and removing suspended solids through a quartz sand filter, such as a Φ800 type, the wastewater is pumped to the dilute sulfuric acid preparation tank of the primary acid leaching section as a supplement to the reaction solution, thus realizing the recycling of wastewater.

[0098] Although embodiments of the invention have been shown, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for comprehensive treatment of solid waste from hydrogen fluoride production, characterized in that, Includes the following steps: Step 1: Pre-treatment of mixed solid waste classification. The mixed solid waste of fluorogypsum, fluorine-containing waste residue and waste catalyst generated from hydrogen fluoride production is crushed to a particle size of ≤10mm and classified by a double-layer vibrating screen. The upper layer is fluorine-containing waste residue and the lower layer is a mixture of fluorogypsum and waste catalyst. The lower layer mixture is magnetically separated to remove impurities. The mass ratio of the mixed solid waste is 70%-80% fluorogypsum, 15%-20% fluorine-containing waste residue, and 5%-10% waste catalyst. Step 2: Co-processing defluorination. In the first-stage acid leaching section, the lower layer mixture is fed into an acid-resistant reactor, and 5%-8% dilute sulfuric acid is added at a liquid-to-solid ratio of 3:

1. The reaction proceeds for 60-90 minutes. After the first-stage acid leaching defluorination, the HF tail gas is absorbed by 10% ammonia water to generate ammonium fluoride. In the second-stage alkali control section, 5%-8% (by weight of solid waste) of calcium hydroxide is added to the reaction solution to adjust the pH to 6.0-7.

0. The reaction proceeds for 40-60 minutes. After the second-stage alkali control defluorination, solid and liquid separation yields filter residue A and filtrate A. Step 3: Resource separation and recovery. Filter residue A is washed and dried to obtain refined calcium sulfate; the upper fluorine-containing waste residue is ground to ≤0.1mm, reacted with 10%-12% hydrochloric acid for 30-40min, filtered, washed and dried to obtain fluorite powder; filtrate A is adjusted to pH 8.0-9.0 with ammonia water to generate Al(OH)3 precipitate; the combined liquid is evaporated and concentrated under the following conditions: temperature 80-85℃, vacuum degree -0.08MPa, cooling crystallization temperature 20-25℃, centrifugation speed 3000r / min; after filtration, the filtrate is combined with the ammonium fluoride absorption liquid, evaporated, concentrated and crystallized to obtain ammonium fluoride crystals; Step 4: Harmless solidification of waste catalyst. The Al(OH)3 precipitate obtained from filtration in Step 3 is mixed with cement, water, and 0.5%-1% phosphate, cured at room temperature for 7 days to form a solidified body, and then landfilled after passing the test. The washing wastewater and filtration mother liquor from steps 2-3 are combined and reused in the primary acid leaching section.

2. The method for comprehensive treatment of solid waste from hydrogen fluoride production according to claim 1, characterized in that, In step 2, the concentration of dilute sulfuric acid in the primary acid leaching is adjusted according to the fluorine content of the mixed solid waste: the concentration is 7%-8% when the fluorine content is >5% and 5%-6% when the fluorine content is ≤5%; the purity of calcium hydroxide controlled by the secondary alkali is ≥95%, and the reaction temperature is adjusted in real time according to the pH, with a temperature increase of 5-10℃ when the pH is <6.

0.

3. The method for comprehensive treatment of solid waste from hydrogen fluoride production according to claim 1, characterized in that, In step 2, the HF tail gas absorption tower is a packed tower with an absorption temperature of 25-30℃. The ammonia water flow rate is automatically adjusted according to the HF concentration in the tail gas to ensure that the ammonium fluoride solution concentration is 20%-25%.

4. The method for comprehensive treatment of solid waste from hydrogen fluoride production according to claim 1, characterized in that, In step 3, filter residue A is washed three times with deionized water at a liquid-to-solid ratio of 2:

1. After washing, the fluoride content of the filter residue is ≤0.1%. Drying is carried out using a rotary dryer at a temperature of 120-150℃, with the moisture content controlled at ≤5%.

5. The method for comprehensive treatment of solid waste from hydrogen fluoride production according to claim 1, characterized in that, In step 3, the fluorine-containing waste residue is ground using a ball mill for 30-40 minutes; the filter residue after hydrochloric acid reaction is washed with deionized water to pH 6.5-7.5 and dried at 100-120℃.

6. The method for comprehensive treatment of solid waste from hydrogen fluoride production according to claim 1, characterized in that, In step 4, the phosphate is diammonium hydrogen phosphate or diammonium hydrogen phosphate, and the cement is P.O42.5 ordinary silicate cement; the curing environment of the solidified body is a temperature of 20-25℃ and a relative humidity of ≥90%, and the heavy metal leaching concentration after curing is: Pb≤0.05mg / L, As≤0.03mg / L.

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