Research On Recycling And Recycling Technology Of Chlorine-containing Wastewater During Wet Treatment Of Recycled Copper Soot

The metallurgical industry has a wide range of production processes and products.It discharges a large amount of wastewater,which is one of the main wastewater polluting the environment.The main characteristics of metallurgical wastewater are many types,large volume,complex and variable.The composition of hydrometallurgical process wastewater is complex.There are still a small amount of heavy metal elements that exceed the standard after neutralization and precipitation.The wastewater containing high concentrations of salts such as NaCl and KCl cannot be discharged.So the treatment of high salt wastewater has become a major environmental protection issue and technical problem for hydrometallurgical enterprises.In this paper,the wastewater generated from the hydrometallurgical prcesses of recycled copper smelting dust was taken as the research object.The recycling and resourceization of wastewater in the production process was studied.The wastewater was was no external discharge.The recycling process of organic phase washing wastewater generated from the metal solvent extraction process was studied.The wastewater was recovered by advanced combined membrane separation technology.67%of the total treatment volume of water containing Cl^-?200 mg/L,Zn²⁺?10 mg/L,Cu²⁺?10 mg/L was produced.It was returned directly for use as production water.The concentrated solution with?15 g/L Zn²⁺was returned to the leaching section to recover zinc,realizing the recyclable use of resources.The relationship between volume balance and element balance in the hydrometallurgical process was studied.The method and process of comprehensive recovery of products such as potassium chloride,sodium chloride and condensate from the effluent discharge for volume balance was studied.The partial raffinate after neutralizd the free acid was used for washing of partial copper smelting dust with high chlorine content.The washing solution was used to produce zinc residue which contained?20%Zn by precipitation with lime.The zinc residue was returned to the main production system for recovery zinc as a neutralizer.The solution after precipitation of zinc was used to remove the hardness by double alkali method.The Ca and Mg content of the softened liquid were less than 20 mg/L under1.05-1.10 times theoretical amount of sodium carbonate and sodium hydroxide.The calcium and magnesium residue was sent to the pyrometallurgical system for use as an ingredient.The softened liquid was adjusted p H to 8.5 by concentrated hydrochloric acid and then used as evaporation liquid.For the separation of NaCl-KCl-H₂O,a ternary system was established by using graded compression MVR technology to extract NaCl and H₂O by evaporation and crystallization,and the concentrated liquid was cooled down to crystallize and extract KCl.The results show that the discharge concentration of falling-film evaporation had a significant effect on the equipment investment and system operation energy consumption.Comprehensive consideration of the operational flexibility and stability of the system,the discharge concentration of falling-film evaporation was taken as 22%.The KCl content in the concentrate had a large impact on the feed volume and operating energy consumption.The higher the KCl content,the better it is for potassium salt production.Considering the continuous operation and cleaning cycle of the system,the KCl content in the concentrate was controlled at 19%-20%.Concentrate cooling end point had a large impact on the feed volume and operating energy consumption.Considering the stability and operability of the continuous operation of the system,the temperature at the end of the cooling point of the concentrated solution was 40?.The industrial practice proved that potassium chloride salt which met the secondary standard of GB/T 5462-2015 industrial wet salt can be produced.Potassium chloride salt that met the technical requirements of GB6549-2011 for industry and agriculture use with Class I first grade can be also produced.The condensate with a TDS concentration of?100 ppm was produced following the standard of sodium chloride.The condensate met the technical index requirements for production reuse.This process has achieved some economic benefits and high environmental benefits,and has high promotion value.