A method for recycling process water in APT production process

Abstract

The present invention introduces a method for reusing process water in the APT production process, which relates to the field of hydrometallurgy technology. The method comprises: step a, reusing wastewater from the alkali extraction system; step b, recovering ammonia by evaporating the stripping solution; step c, graded utilization of ammonia by evaporating pure ammonium tungstate; step d, closed-loop utilization of ammonia by evaporating ammonium molybdate; and step e, resource recovery of ammonia gas in the crystallization stage. The method for reusing process water in the APT production process of the present invention implements a closed-loop design for the entire process, completely eliminating discharged wastewater and meeting environmental regulations. It also reduces wastewater treatment costs and fresh water usage, resulting in a 15%-30% reduction in overall costs. Key components, such as ammonia and sodium ions, are graded for reuse, reducing raw material consumption by over 20%. The method is suitable for retrofitting existing scheelite APT production lines, is simple to operate, and does not require large-scale equipment upgrades.

Description

Technical Field

[0001] The present invention relates to the technical field of hydrometallurgy, and in particular to a method for recycling process water in an APT production process. Background Art

[0002] Scheelite is extracted through alkaline extraction to produce APT using a wet smelting process. Each process generates a large amount of process wastewater containing ammonia, sodium ions and sulfates. In traditional processes, this wastewater needs to undergo complex treatment before being discharged, which not only increases treatment costs but also makes it difficult to meet increasingly stringent environmental protection requirements. In existing technologies, wastewater reuse solutions are mostly limited to a single link and lack system integration, resulting in low overall reuse efficiency. Summary of the Invention

[0003] The purpose of the present invention is to overcome the shortcomings of the existing technology and provide a method for reusing process water in the APT production process, which achieves zero wastewater discharge through multi-link closed-loop circulation of process water, thereby achieving both economic and environmental benefits.

[0004] The technical solution adopted in the present invention is:

[0005] A method for recycling process water in an APT production process, comprising:

[0006] Step a, reuse of wastewater from the alkali extraction system: The wastewater from the alkaline extraction stage of the alkali extraction system includes raffinate and washing stage wastewater. After static sedimentation, the raffinate and washing stage wastewater are transferred to a decomposition workshop and then pumped into a decomposition pulping tank. Lime is added to the pulping tank and heated to 75-85°C. Sodium carbonate is then added to adjust the pH value to 8.0-8.5, and then mineral powder is added to perform pulping operations;

[0007] Step b, stripping liquid evaporation and ammonia recovery: the stripping liquid of the alkaline extraction system enters the continuous crystallizer for evaporation, and the generated ammonia gas is condensed into recovered ammonia water A through a shell and tube heat exchanger. The recovered ammonia water A is transported to a stripping agent configuration stirring tank through a pipeline, and after adding ammonium bicarbonate and mixing, the mixture is stirred and heated to 30-40°C to obtain a stripping agent. The stripping agent is returned to the alkaline extraction stage for standby use; the evaporated solution is filtered to obtain crude ammonium tungstate crystals for use in the ammonia dissolution process, and the filtrate is used to obtain ammonium molybdate solution and sent to a concentrator;

[0008] Step c, graded utilization of ammonia water after evaporation of pure ammonium tungstate: During the evaporation and concentration process of pure ammonium tungstate, the generated ammonia vapor is condensed to obtain recovered ammonia water B, which flows into the recovered ammonia water tank by gravity. The recovered ammonia water B is transferred from the recovered ammonia water tank to the ammonia flushing tank. Liquid ammonia is added to the ammonia flushing tank to increase the concentration of the recovered ammonia water B to 5-8 mol / L. The recovered ammonia water B is then pumped into the ammonia dissolving kettle. The crude ammonium tungstate crystals obtained in step b are added to the ammonia dissolving kettle for dissolution to prepare the ammonium tungstate solution and transport it to the moving bed in the ion exchange process for use.

[0009] Step d, closed-loop utilization of ammonia water from ammonium molybdate evaporation: Ammonia vapor generated during the evaporation and concentration process of the ammonium molybdate solution in the concentrator is condensed to obtain recovered ammonia water C, which flows by gravity into an ammonia water low-level tank, is pumped into an ammonia water high-level tank, and flows by gravity into an alkaline extraction washing tank to be used as washing water in the alkaline extraction section to remove sodium ions;

[0010] Step e, ammonia resource utilization in the crystallization stage: the residual ammonia in the evaporation process of the continuous crystallizer and the APT evaporation crystallizer is respectively drawn into the sulfuric acid absorption tower by a fan for spray absorption to generate ammonium sulfate wastewater; the ammonium sulfate wastewater is discharged into the ammonium sulfate solution tank, and then pumped into the multi-effect evaporator for evaporation and concentration, and then cooled by the condenser and filtered to obtain ammonium sulfate salt.

[0011] Specifically, in the step a, the wastewater in the alkaline extraction stage is allowed to settle for 2-4 hours to facilitate oil-water separation; the amount of mineral powder added ensures that the tungsten metal content of the solution after pulping is 80-110 g / L.

[0012] Specifically, in the step b, the temperature of the continuous crystallizer is controlled at 90-105°C, and the temperature of the shell and tube heat exchanger is controlled at 20-30°C; to ensure efficient recovery of ammonia water; when preparing the stripping agent, the amount of recovered ammonia water A added in each batch is 35-45m³, and the amount of ammonium bicarbonate added is 7 tons.

[0013] Specifically, the condensation temperature in step c is controlled at 20-30°C.

[0014] Specifically, in the step d, the evaporation temperature of ammonium molybdate is controlled at 70-80°C, and the condensation temperature is controlled at 20-30°C.

[0015] Specifically, in the step e, the absorption tower is a wet packed absorption tower using annular packing, sulfuric acid is circulated in the absorption tower, the sulfuric acid concentration is 1 mol / L, and when the pH of the circulating liquid reaches 6-7, the solution is discharged into the ammonium sulfate solution tank and replaced with new sulfuric acid, and the temperature of the multi-effect evaporator is controlled at 100-110°C.

[0016] Due to the adoption of the above technical solution, the present invention has the following advantages:

[0017] The method for recycling process water in the APT production process of the present invention realizes a closed-loop design for the entire process, completely eliminates discharged wastewater, and meets the requirements of environmental protection regulations; reduces wastewater treatment costs and fresh water consumption, and reduces overall costs by 15%-30%; and reduces raw material consumption by more than 20% through graded recycling of key components such as ammonia water and sodium ions. The method is suitable for the transformation of existing APT production lines for low-grade scheelite, is simple to operate, and does not require large-scale equipment upgrades. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1It is a process flow chart of the entire APT production process of the present invention. DETAILED DESCRIPTION

[0019] The present invention will be further explained below with reference to the accompanying drawings and embodiments, which should not be used to limit the scope of protection of the present invention. The purpose of disclosing the present invention is to protect all technical improvements within the scope of the present invention. Example 1

[0020] Combined with attachment Figure 1 A method for recycling process water in an APT production process is shown, comprising:

[0021] Step a, reuse of wastewater from the alkali extraction system: The wastewater from the alkaline extraction stage of the alkali extraction system includes a raffinate with a tungsten content of 10 g / L and wastewater from the washing stage. 25 cubic meters of the raffinate and washing wastewater are allowed to stand for 2 hours to settle, and then transferred to a decomposition workshop. The decomposition pulping tank is then pumped into a decomposition pulping tank. 800 kg of lime is added to the pulping tank, and after heating to 75°C, 250 kg of sodium carbonate is added to adjust the pH value to 8.0-8.5, and then 18.6 t of mineral powder is added for pulping. After pulping, the tungsten metal content of the solution is 80-110 g / L.

[0022] Step b, stripping liquor evaporation and ammonia recovery: the stripping liquor of the alkaline extraction system is evaporated in a continuous crystallizer with a temperature controlled at 90°C. The generated ammonia gas is condensed in a shell and tube heat exchanger with a temperature of 20°C to obtain recovered ammonia water A with a concentration of 4 mol / L. 35 m³ of recovered ammonia water A is transported to a stripping agent configuration stirring tank through a pipeline, 7 tons of ammonium bicarbonate is added and mixed, stirring is started and the temperature is increased. After the temperature reaches 35°C, stirring is continued for half an hour to obtain a stripping agent. The stripping agent is returned to the alkaline extraction stage for standby use; the evaporated solution is filtered to obtain crude ammonium tungstate crystals for use in the ammonia dissolution process, and the filtrate is used to obtain ammonium molybdate solution and sent to a concentrator.

[0023] Step c, graded utilization of ammonia water after evaporation of pure ammonium tungstate: During the evaporation and concentration process of pure ammonium tungstate, the generated ammonia vapor is condensed to obtain recovered ammonia water B with a concentration of 5 mol / L. The condensation temperature is controlled at 20°C. The recovered ammonia water B flows into the recovered ammonia water tank by gravity. 5 m³ of recovered ammonia water B is transferred from the recovered ammonia water tank to the ammonia flushing tank. 0.5 m³ of liquid ammonia is added to the ammonia flushing tank. After the concentration of the recovered ammonia water B is increased to 8 mol / L, it is pumped into the ammonia dissolving kettle, and 2.5 tons of crude ammonium tungstate crystals are added for dissolution to form an ammonium tungstate solution. The ammonium tungstate solution is transported to the moving bed of the ion exchange process for use.

[0024] Step d, closed-loop utilization of ammonia water by evaporation of ammonium molybdate: ammonia vapor generated during the evaporation and concentration process of the ammonium molybdate solution in a concentrator at 70°C is condensed to obtain recovered ammonia water C with a concentration of 2 mol / L, and the condensation temperature is controlled at 20°C; the recovered ammonia water C flows by gravity into the ammonia water low-level tank, is pumped into the ammonia water high-level tank, and then flows by gravity into the alkaline extraction washing tank. The flow rate is controlled at 1 m³ by controlling the valve opening, and is used as wash water in the alkaline extraction washing section to remove sodium ions.

[0025] Step e, ammonia resource utilization in the crystallization stage: residual ammonia in the evaporation process of the continuous crystallizer and the APT evaporation crystallizer is respectively drawn into a sulfuric acid absorption tower by a fan for spray absorption to generate ammonium sulfate wastewater. The absorption tower is a wet-packed absorption tower using annular packing. Sulfuric acid is circulated in the absorption tower with a sulfuric acid concentration of 1 mol / L. When the pH of the circulating liquid reaches 6-7, the ammonium sulfate wastewater is discharged into an ammonium sulfate solution tank and replaced with new sulfuric acid. The solution is then pumped into a multi-effect evaporator for evaporation and concentration, and then cooled in a condenser and filtered to obtain ammonium sulfate salt. The temperature of the multi-effect evaporator is controlled at 100°C. Example 2

[0026] Combined with attachment Figure 1 A method for recycling process water in an APT production process is shown, comprising:

[0027] Step a, reuse of wastewater from the alkali extraction system: The wastewater from the alkaline extraction stage of the alkali extraction system includes a raffinate with a tungsten content of 10 g / L and wastewater from the washing stage. 28.3 cubic meters of the raffinate and washing wastewater are taken and allowed to stand for 4 hours to settle, then transferred to a decomposition workshop and then pumped into a decomposition pulping tank. 730 kg of lime is added to the pulping tank, and after heating to 85°C, 263 kg of sodium carbonate is added to adjust the pH value to 8.0-8.5, and then 17.9 t of mineral powder is added for pulping. After pulping, the tungsten metal content of the solution is 80-110 g / L.

[0028] Step b, stripping liquor evaporation and ammonia recovery: the stripping liquor of the alkaline extraction system is evaporated in a continuous crystallizer controlled at 105°C, and the generated ammonia gas is condensed in a shell and tube heat exchanger at a temperature of 30°C to obtain recovered ammonia water A with a concentration of 3 mol / L. 45m³ of recovered ammonia water A is transported to a stripping agent configuration stirring tank through a pipeline, 7 tons of ammonium bicarbonate is added and mixed, and stirring is started and the temperature is increased. After the temperature reaches 35°C, stirring is continued for half an hour to obtain a stripping agent, and the stripping agent is returned to the alkaline extraction stage for standby use; the evaporated solution is filtered to obtain crude ammonium tungstate crystals for use in the ammonia dissolution process, and the filtrate is used to obtain ammonium molybdate solution and sent to a concentrator.

[0029] c. Gradual utilization of ammonia water after evaporation of pure ammonium tungstate: During the evaporation and concentration process of pure ammonium tungstate, the generated ammonia vapor is condensed to obtain recovered ammonia water B with a concentration of 5 mol / L. The condensation temperature is controlled at 30°C. The recovered ammonia water B flows into the recovered ammonia water tank by gravity. 5m³ of recovered ammonia water B is transferred from the recovered ammonia water tank to the ammonia flushing tank. 0.7m³ of liquid ammonia is added to the ammonia flushing tank. After the concentration of the recovered ammonia water B is increased to 5 mol / L, it is pumped into the ammonia dissolving kettle, and 2.3 tons of crude ammonium tungstate crystals are added for dissolution to form an ammonium tungstate solution. The ammonium tungstate solution is transported to the moving bed of the ion exchange process for use.

[0030] Step d, closed-loop utilization of ammonia water by evaporation of ammonium molybdate: ammonia vapor generated during the evaporation and concentration process of the ammonium molybdate solution in a concentrator at 80°C is condensed to obtain recovered ammonia water C with a concentration of 2.5 mol / L, and the condensation temperature is controlled at 30°C; the recovered ammonia water C flows by gravity into the low-level ammonia water tank, is pumped into the high-level ammonia water tank, and then flows by gravity into the alkaline extraction washing tank. The flow rate is controlled at 1 m³ by controlling the valve opening, and is used as wash water in the alkaline extraction washing section to remove sodium ions.

[0031] Step e, ammonia resource utilization in the crystallization stage: residual ammonia in the evaporation process of the continuous crystallizer and the APT evaporation crystallizer is respectively drawn into a sulfuric acid absorption tower by a fan for spray absorption to generate ammonium sulfate wastewater. The absorption tower is a wet-packed absorption tower using annular packing. Sulfuric acid is circulated in the absorption tower with a sulfuric acid concentration of 1 mol / L. When the pH of the circulating liquid reaches 6-7, the ammonium sulfate wastewater is discharged into an ammonium sulfate solution tank and replaced with new sulfuric acid. The solution is then pumped into a multi-effect evaporator for evaporation and concentration, and then cooled in a condenser and filtered to obtain ammonium sulfate salt. The temperature of the multi-effect evaporator is controlled at 110°C.

[0032] The parts not described in detail in this invention are prior art.

[0033] The embodiments selected herein for the purpose of disclosing the invention are presently considered suitable, but it should be understood that the invention is intended to include all variations and modifications of the embodiments that fall within the scope of the concept and invention.

Claims

1. A method for recycling process water in an APT production process, characterized in that: include: Step a, reuse of wastewater from the alkali extraction system: The wastewater from the alkaline extraction stage of the alkali extraction system includes raffinate and washing stage wastewater. After static sedimentation, the raffinate and washing stage wastewater are transferred to a decomposition workshop and then pumped into a decomposition pulping tank. Lime is added to the pulping tank and heated to 75-85°C. Sodium carbonate is then added to adjust the pH value to 8.0-8.5, and then mineral powder is added to perform pulping operations; Step b, stripping liquid evaporation and ammonia recovery: the stripping liquid of the alkaline extraction system enters the continuous crystallizer for evaporation, and the generated ammonia gas is condensed into recovered ammonia water A through a shell and tube heat exchanger. The recovered ammonia water A is transported to a stripping agent configuration stirring tank through a pipeline, and after adding ammonium bicarbonate and mixing, the mixture is stirred and heated to 30-40°C to obtain a stripping agent. The stripping agent is returned to the alkaline extraction stage for standby use; the evaporated solution is filtered to obtain crude ammonium tungstate crystals for use in the ammonia dissolution process, and the filtrate is used to obtain ammonium molybdate solution and sent to a concentrator; Step c, graded utilization of ammonia water after evaporation of pure ammonium tungstate: During the evaporation and concentration process of pure ammonium tungstate, the generated ammonia vapor is condensed to obtain recovered ammonia water B, which flows into the recovered ammonia water tank by gravity. The recovered ammonia water B is transferred from the recovered ammonia water tank to the ammonia flushing tank. Liquid ammonia is added to the ammonia flushing tank to increase the concentration of the recovered ammonia water B to 5-8 mol / L. The recovered ammonia water B is then pumped into the ammonia dissolving kettle. The crude ammonium tungstate crystals obtained in step b are added to the ammonia dissolving kettle for dissolution to prepare the ammonium tungstate solution and transport it to the moving bed in the ion exchange process for use. Step d, closed-loop utilization of ammonia water from ammonium molybdate evaporation: Ammonia vapor generated during the evaporation and concentration process of the ammonium molybdate solution in the concentrator is condensed to obtain recovered ammonia water C, which flows by gravity into the ammonia water low-level tank, is pumped into the ammonia water high-level tank, and then flows by gravity into the alkaline extraction washing tank to be used as washing water in the alkaline extraction stage to remove sodium ions; Step e, ammonia resource utilization in the crystallization stage: the residual ammonia in the evaporation process of the continuous crystallizer and the APT evaporation crystallizer is respectively drawn into the sulfuric acid absorption tower by a fan for spray absorption to generate ammonium sulfate wastewater; the ammonium sulfate wastewater is discharged into the ammonium sulfate solution tank, and then pumped into the multi-effect evaporator for evaporation and concentration, and then cooled by the condenser and filtered to obtain ammonium sulfate salt.

2. The method for recycling process water in the APT production process according to claim 1, characterized in that: In the step a, the wastewater in the alkaline extraction stage is allowed to settle for 2-4 hours; the amount of mineral powder added ensures that the tungsten metal content of the solution after pulping is 80-110 g / L.

3. The method for recycling process water in the APT production process according to claim 1, characterized in that: In the step b, the temperature of the continuous crystallizer is controlled at 90-105°C, and the temperature of the shell and tube heat exchanger is controlled at 20-30°C; when preparing the stripping agent, the amount of recovered ammonia water A added in each batch is 35-45m³, and the amount of ammonium bicarbonate added is 7 tons.

4. The method for recycling process water in the APT production process according to claim 1, characterized in that: In the step c, the condensation temperature is controlled at 20-30°C.

5. The method for recycling process water in an APT production process according to claim 1, characterized in that: In the step d, the evaporation temperature of ammonium molybdate is controlled at 70-80°C, and the condensation temperature is controlled at 20-30°C.

6. The method for recycling process water in the APT production process according to claim 1, characterized in that: In the step e, the absorption tower is a wet-type packed absorption tower using annular packing, sulfuric acid is circulated in the absorption tower, the sulfuric acid concentration is 1 mol / L, and when the pH of the circulating liquid reaches 6-7, the solution is discharged into the ammonium sulfate solution tank and replaced with new sulfuric acid, and the temperature of the multi-effect evaporator is controlled at 100-110°C.

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