Method for recycling process water in APT (ammonium paratungstate) production process

Abstract

The invention discloses a method for recycling process water in an APT (ammonium paratungstate) production process, and relates to the field of water recovery in an APT production process, and the method comprises the following steps: S1, recycling wastewater of an alkali extraction system; s2, evaporating strip liquor and recovering ammonia water; s3, chemical treatment of pure ammonium tungstate evaporation ammonia water; s4, ammonium molybdate evaporation ammonia water closed-loop utilization; and S5, recycling ammonia gas in a crystallization section. According to the method, the recovery rate of tungsten and molybdenum in the tail liquid is remarkably increased by optimizing the processes of wastewater reuse of the alkali extraction system, strip liquor evaporation, ammonia water recovery and the like; one part of the tail liquid is recycled in the pulping process, the other part of the tail liquid is subjected to evaporation treatment, zero emission of wastewater is achieved, evaporated condensate water can be recycled to be used for preparing a stripping agent, the utilization rate of water resources is further increased, the production cost is reduced, and meanwhile the environment-friendly requirement is met.

Description

Technical Field

[0001] This invention relates to the field of water recycling in APT production processes, and particularly to a method for reusing process water during APT production. Background Technology

[0002] Ammonium paratungstate (APT) is an important intermediate product in the tungsten industry, widely used in the manufacture of tungsten powder, tungsten wire, and tungsten alloys. Traditional APT production methods mainly include chemical methods, ion exchange methods, and solvent extraction methods. Among these, solvent extraction is widely used due to its advantages such as high efficiency and environmental friendliness. However, existing solvent extraction methods still have some problems in the production process, which limit their further development and application.

[0003] Traditional APT production processes generate large volumes of wastewater, primarily consisting of high-concentration sodium tungstate solution and raffinate. Direct discharge of this wastewater without treatment would cause severe environmental pollution. Therefore, it is essential to propose a method for reusing process water during APT production to address these issues. Summary of the Invention

[0004] The purpose of this invention is to provide a method for reusing process water in the APT production process, in order to solve the problem that the traditional APT production process has a large amount of wastewater discharge, mainly containing high-concentration sodium tungstate solution and raffinate. If this wastewater is discharged directly without treatment, it will cause serious environmental pollution.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a method for reusing process water during APT production, comprising:

[0006] S1: Wastewater reuse from the alkali extraction system;

[0007] S101: Wastewater is collected and pretreated. Wastewater from the alkaline extraction stage of the alkaline extraction system is collected in a wastewater tank and pretreated with an appropriate amount of flocculant to remove suspended solids and large particulate impurities from the wastewater.

[0008] S102: The pretreated wastewater is left to stand in the wastewater tank for 2-4 hours to separate oil and water. The supernatant after sedimentation is transferred to the next step of treatment.

[0009] S103: Transfer the supernatant after precipitation to the equalization tank, add an appropriate amount of sodium hydroxide solution, and adjust the pH value to 9.0-9.5;

[0010] S104: Transfer the adjusted wastewater to the decomposition workshop, pump it into the decomposition pulping tank, add lime to the pulping tank, and heat it to 75-85℃.

[0011] S105: Add sodium carbonate to further adjust the pH value to 8.0-8.5, then add mineral powder for pulping.

[0012] S2: Ammonia recovery from back-extraction liquid evaporation;

[0013] S201: Input the back-extraction liquid from the alkaline extraction system into the continuous crystallizer and control the crystallizer temperature at 90-105℃ for evaporation;

[0014] S202: The ammonia gas generated during the evaporation process is condensed through a tube heat exchanger to obtain recovered ammonia water A;

[0015] S203: The recovered ammonia water A is fed into a stirring tank for preparing the stripping agent. Ammonium bicarbonate is added and mixed. The mixture is stirred and heated to 30-40℃ to obtain the stripping agent. The amount of recovered ammonia water A added in each batch is 35-45 mg / L. 3 The amount of ammonium bicarbonate added was 7 tons;

[0016] S204: The obtained back-extraction agent is returned to the alkaline extraction stage for later use. The evaporated solution is filtered to obtain crude ammonium tungstate crystals for use in the ammonia dissolution process. The filtrate is used to obtain ammonium molybdate solution, which is then sent to the concentrator.

[0017] S205: Further process the recovered ammonia water A by adding an appropriate amount of sulfuric acid for neutralization reaction, controlling the pH value at 6.0-6.5, and generating ammonium sulfate solution;

[0018] S3: Chemical treatment of ammonia water evaporated from pure ammonium tungstate;

[0019] S301: During the evaporation and concentration of pure ammonium tungstate, the generated ammonia vapor is condensed to obtain recovered ammonia water B, and the condensation temperature is controlled at 20-30℃.

[0020] S302: The recovered ammonia water B is transported to the chemical treatment tank, an appropriate amount of sulfuric acid is added, the pH value is controlled at 6.0-6.5, and a neutralization reaction is carried out. After the reaction is completed, an appropriate amount of sodium chloride is added and stirred evenly so that the ammonia in the solution precipitates out in the form of ammonium chloride.

[0021] S303: Ammonium chloride precipitate is separated by filtration, and the filtrate obtained is the specific liquid E after treatment;

[0022] S4: Ammonium molybdate evaporates ammonia water for closed-loop utilization;

[0023] S401: The ammonium molybdate solution is evaporated and concentrated in a concentrator. The resulting ammonia vapor is condensed to obtain recovered ammonia water C. The condensation temperature is controlled at 20-30℃.

[0024] S402: The recovered ammonia water C is transported to the chemical treatment tank, an appropriate amount of sulfuric acid is added, and the pH value is controlled at 6.0-6.5 to carry out the neutralization reaction. After the reaction is completed, an appropriate amount of sodium chloride is added and stirred evenly to precipitate the ammonia in the solution as ammonium chloride.

[0025] S403: Ammonium chloride precipitate is separated by filtration, and the filtrate obtained is the specific liquid R after treatment;

[0026] S404: The treated specific liquid is pumped into the ammonia water high-level tank, and then flows into the alkaline extraction washing tank by gravity, where it is used as washing water in the alkaline extraction section to remove sodium ions.

[0027] S5: Ammonia resource utilization in the crystallization section;

[0028] S501: The residual ammonia gas in the continuous crystallizer and APT evaporator crystallizer evaporation process is drawn into the sulfuric acid absorption tower by the blower for spray absorption, generating ammonium sulfate wastewater. The absorption tower is a wet packed absorption tower with ring packing. The sulfuric acid is recycled in the absorption tower.

[0029] S502: When the pH value of the circulating liquid drops to 6-7, the ammonium sulfate wastewater is discharged into the ammonium sulfate solution tank to replace the sulfuric acid. The solution is then pumped into a multi-effect evaporator for evaporation and concentration. After cooling by a condenser, it is filtered to obtain ammonium sulfate salt. The temperature of the multi-effect evaporator is controlled at 100-110℃ to complete the reuse of process water in the APT production process.

[0030] Preferably, the amount of mineral powder added in S105 ensures that the tungsten metal content in the solution after pulping is 80-110 g / L.

[0031] Preferably, in step S202, the heat exchanger temperature is controlled at 20-30°C.

[0032] Preferably, in step S301, the evaporation temperature is controlled at 70-80°C.

[0033] Preferably, in step S401, the evaporation temperature is controlled at 70-80°C.

[0034] Preferably, the sulfuric acid concentration in S501 is 1 mol / L.

[0035] The technical effects and advantages of this invention are as follows:

[0036] 1. By optimizing processes such as wastewater reuse in the alkaline extraction system and ammonia recovery from back-extraction liquid evaporation, the recovery rate of tungsten and molybdenum in the tail liquid is significantly improved;

[0037] 2. By recycling a portion of the tail liquid into the pulping process and treating the other portion through evaporation, zero wastewater discharge is achieved. The condensate after evaporation can be recycled for the preparation of back-extraction agents, further improving the utilization rate of water resources, reducing production costs, and meeting environmental protection requirements.

[0038] 3. By achieving zero wastewater discharge and efficient resource recycling, wastewater discharge and environmental pollution are significantly reduced. At the same time, by optimizing the process, energy consumption and resource consumption are reduced, and resource utilization efficiency is improved, resulting in significant environmental benefits. Attached Figure Description

[0039] Figure 1 This diagram illustrates the method for reusing process water during the APT production process according to the present invention. Detailed Implementation

[0040] This invention provides, for example Figure 1 The method for reusing process water in the APT production process, as shown, includes the following steps:

[0041] The first step is to reuse the wastewater from the alkali extraction system;

[0042] First, the wastewater is collected and pretreated: the wastewater from the alkaline extraction stage of the alkaline extraction system is collected into a wastewater tank, and an appropriate amount of flocculant is added for pretreatment to remove suspended solids and large particulate impurities in the wastewater and improve the efficiency of subsequent treatment.

[0043] The pretreated wastewater is then left to stand in the wastewater tank for 2-4 hours to separate oil and water. The supernatant after sedimentation is transferred to the next step of treatment.

[0044] The supernatant after precipitation is transferred to an equalization tank, and an appropriate amount of sodium hydroxide solution is added to adjust the pH value to 9.0-9.5 to neutralize the acidic components in the wastewater and promote the precipitation of metal ions.

[0045] The adjusted wastewater is transferred to the decomposition workshop, pumped into the decomposition pulping tank, lime is added to the pulping tank, and the temperature is raised to 75-85℃.

[0046] Sodium carbonate is added to further adjust the pH value to 8.0-8.5, and then mineral powder is added for pulping. The amount of mineral powder added should ensure that the tungsten metal content of the solution after pulping is 80-110 g / L.

[0047] The second step is to recover ammonia by evaporating the back-extraction solution.

[0048] The back-extraction liquid from the alkali extraction system is fed into a continuous crystallizer, and the crystallizer temperature is controlled at 90-105℃ for evaporation.

[0049] The ammonia gas generated during the evaporation process is condensed through a tube heat exchanger. The temperature of the heat exchanger is controlled at 20-30℃ to obtain recovered ammonia water A.

[0050] The recovered ammonia water A is fed into a stirring tank for preparing the stripping agent. Ammonium bicarbonate is added and mixed, and the mixture is stirred and heated to 30-40℃ to obtain the stripping agent. The amount of recovered ammonia water A added in each batch is 35-45 mg / L. 3 The amount of ammonium bicarbonate added was 7 tons.

[0051] The obtained back-extraction agent is returned to the alkaline extraction stage for later use. The evaporated solution is filtered to obtain crude ammonium tungstate crystals for use in the ammonia dissolution process. The filtrate is used to prepare ammonium molybdate solution, which is then sent to a concentrator.

[0052] The recovered ammonia water A is further processed by adding an appropriate amount of sulfuric acid for neutralization, controlling the pH value at 6.0-6.5, to generate an ammonium sulfate solution, which can be directly used in subsequent ion exchange processes.

[0053] The third step is the chemical treatment process of evaporating ammonia water from pure ammonium tungstate.

[0054] During the evaporation and concentration of pure ammonium tungstate, the evaporation temperature is controlled at 70-80℃, and the generated ammonia vapor is condensed to obtain recovered ammonia water B, with the condensation temperature controlled at 20-30℃.

[0055] The recovered ammonia water B is transported to a chemical treatment tank, where an appropriate amount of sulfuric acid is added and the pH value is controlled at 6.0-6.5 for neutralization. After the reaction is completed, an appropriate amount of sodium chloride is added and stirred evenly to precipitate the ammonia in the solution as ammonium chloride.

[0056] Ammonium chloride precipitate is separated by filtration, and the resulting filtrate is a specific treated liquid E, whose main components include ammonium sulfate and a small amount of sodium chloride, which can be directly used in subsequent ion exchange processes.

[0057] The fourth step involves evaporating ammonium molybdate to utilize the ammonia water in a closed-loop process.

[0058] The ammonium molybdate solution is evaporated and concentrated in a concentrator, with the evaporation temperature controlled at 70-80℃. The resulting ammonia vapor is condensed to obtain recovered ammonia water C, with the condensation temperature controlled at 20-30℃.

[0059] The recovered ammonia water C is transported to a chemical treatment tank, where an appropriate amount of sulfuric acid is added and the pH value is controlled at 6.0-6.5 for neutralization. After the reaction is completed, an appropriate amount of sodium chloride is added and stirred evenly to precipitate the ammonia in the solution as ammonium chloride.

[0060] Ammonium chloride precipitate is separated by filtration, and the resulting filtrate is a specific treated liquid R, whose main components include ammonium sulfate and a small amount of sodium chloride, which can be directly used in subsequent ion exchange processes.

[0061] The treated specific liquid is pumped into an ammonia water high-level tank, and then flows by gravity into an alkaline extraction washing tank, where it is used as washing water in the alkaline extraction section to remove sodium ions.

[0062] The fifth step is the ammonia resource utilization step in the crystallization section;

[0063] The residual ammonia gas generated during the evaporation process in the continuous crystallizer and the APT evaporator crystallizer is drawn into the sulfuric acid absorption tower by a blower for spray absorption, generating ammonium sulfate wastewater. The absorption tower is a wet packed absorption tower with ring packing. The sulfuric acid is recycled in the absorption tower, and the sulfuric acid concentration is 1 mol / L.

[0064] When the pH of the circulating liquid drops to 6-7, the ammonium sulfate wastewater is discharged into the ammonium sulfate solution tank to replace the sulfuric acid. The solution is then pumped into a multi-effect evaporator for evaporation and concentration. After cooling by a condenser, the solution is filtered to obtain ammonium sulfate salt. The temperature of the multi-effect evaporator is controlled at 100-110℃.

[0065] Through the above improvements, the method for reusing process water in the APT production process of this invention not only achieves a closed-loop design throughout the entire process, completely eliminating the discharge of wastewater and meeting environmental regulations, but also reduces wastewater treatment costs and fresh water consumption, resulting in a 15%-30% reduction in overall costs. Furthermore, by chemically treating "pure ammonium tungstate evaporated ammonia water" directly into a usable liquid, resource utilization efficiency is further improved and raw material consumption is reduced.

Claims

1. A method for reusing process water in the APT production process, characterized in that, include: S1: Wastewater reuse from the alkali extraction system; S101: Wastewater is collected and pretreated. Wastewater from the alkaline extraction stage of the alkaline extraction system is collected in a wastewater tank and pretreated with an appropriate amount of flocculant to remove suspended solids and large particulate impurities from the wastewater. S102: The pretreated wastewater is left to stand in the wastewater tank for 2-4 hours to separate oil and water. The supernatant after sedimentation is transferred to the next step of treatment. S103: Transfer the supernatant after precipitation to the equalization tank, add an appropriate amount of sodium hydroxide solution, and adjust the pH value to 9.0-9.5; S104: Transfer the adjusted wastewater to the decomposition workshop, pump it into the decomposition pulping tank, add lime to the pulping tank, and heat it to 75-85℃. S105: Add sodium carbonate to further adjust the pH value to 8.0-8.5, then add mineral powder for pulping. S2: Ammonia recovery from back-extraction liquid evaporation; S201: Input the back-extraction liquid from the alkaline extraction system into the continuous crystallizer and control the crystallizer temperature at 90-105℃ for evaporation; S202: The ammonia gas generated during the evaporation process is condensed through a tube heat exchanger to obtain recovered ammonia water A; S203: The recovered ammonia water A is fed into a stirring tank for preparing the stripping agent. Ammonium bicarbonate is added and mixed. The mixture is stirred and heated to 30-40℃ to obtain the stripping agent. The amount of recovered ammonia water A added in each batch is 35-45 mg / L. 3 The amount of ammonium bicarbonate added was 7 tons; S204: The obtained back-extraction agent is returned to the alkaline extraction stage for later use. The evaporated solution is filtered to obtain crude ammonium tungstate crystals for use in the ammonia dissolution process. The filtrate is used to obtain ammonium molybdate solution, which is then sent to the concentrator. S205: Further process the recovered ammonia water A by adding an appropriate amount of sulfuric acid for neutralization reaction, controlling the pH value at 6.0-6.5, and generating ammonium sulfate solution; S3: Chemical treatment of ammonia water evaporated from pure ammonium tungstate; S301: During the evaporation and concentration of pure ammonium tungstate, the generated ammonia vapor is condensed to obtain recovered ammonia water B, and the condensation temperature is controlled at 20-30℃. S302: The recovered ammonia water B is transported to the chemical treatment tank, an appropriate amount of sulfuric acid is added, the pH value is controlled at 6.0-6.5, and a neutralization reaction is carried out. After the reaction is completed, an appropriate amount of sodium chloride is added and stirred evenly so that the ammonia in the solution precipitates out in the form of ammonium chloride. S303: Ammonium chloride precipitate is separated by filtration, and the filtrate obtained is the specific liquid E after treatment; S4: Ammonium molybdate evaporates ammonia water for closed-loop utilization; S401: The ammonium molybdate solution is evaporated and concentrated in a concentrator. The resulting ammonia vapor is condensed to obtain recovered ammonia water C. The condensation temperature is controlled at 20-30℃. S402: The recovered ammonia water C is transported to the chemical treatment tank, an appropriate amount of sulfuric acid is added, and the pH value is controlled at 6.0-6.5 to carry out the neutralization reaction. After the reaction is completed, an appropriate amount of sodium chloride is added and stirred evenly to precipitate the ammonia in the solution as ammonium chloride. S403: Ammonium chloride precipitate is separated by filtration, and the filtrate obtained is the specific liquid R after treatment; S404: The treated specific liquid is pumped into the ammonia water high-level tank, and then flows into the alkaline extraction washing tank by gravity, where it is used as washing water in the alkaline extraction section to remove sodium ions. S5: Ammonia resource utilization in the crystallization section; S501: The residual ammonia gas in the continuous crystallizer and APT evaporator crystallizer evaporation process is drawn into the sulfuric acid absorption tower by the blower for spray absorption, generating ammonium sulfate wastewater. The absorption tower is a wet packed absorption tower with ring packing. The sulfuric acid is recycled in the absorption tower. S502: When the pH value of the circulating liquid drops to 6-7, the ammonium sulfate wastewater is discharged into the ammonium sulfate solution tank to replace the sulfuric acid. The solution is then pumped into a multi-effect evaporator for evaporation and concentration. After cooling by a condenser, it is filtered to obtain ammonium sulfate salt. The temperature of the multi-effect evaporator is controlled at 100-110℃ to complete the reuse of process water in the APT production process.

2. The method for reusing process water in the APT production process according to claim 1, characterized in that: The amount of mineral powder added in S105 ensures that the tungsten metal content in the solution after pulping is 80-110 g / L.

3. The method for reusing process water in the APT production process according to claim 1, characterized in that: In S202, the heat exchanger temperature is controlled at 20-30℃.

4. The method for reusing process water in the APT production process according to claim 1, characterized in that: In S301, the evaporation temperature is controlled at 70-80℃.

5. A method for reusing process water in the APT production process according to claim 1, characterized in that: In S401, the evaporation temperature is controlled at 70-80℃.

6. A method for reusing process water in APT production according to claim 1, characterized in that: The sulfuric acid concentration in S501 is 1 mol / L.

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