| This thesis analyzes the source,characterization,management and treatment status of hazardous waste in Zhejiang Province,and evaluates the existing management measures and treatment technology,and puts forward the solution of hazardous waste.Zhejiang Province is an important stainless steel production base in China.The environmental pollution problems of stainless steel pickling industry were investigated,and the process scheme and recommended measures were proposed on the basis of the study of the source,composition and treatment of hazardous waste.Two-stage absorption and reduction process was used to meet the discharge of NOx standards,and the pickling wastewater was recycled to the workshop after the treatment by the combination process of "secondary physical and chemical + primary oxidation + sand filter".Herein,water resources recycling was achieved and the discharge requirements can be meet.The vacuum distillation of waste acid for acid recycling was used,and the subsequent consumption of neutralizing agents and the amount of generated waste can be significantly reduced.The instantaneous concentration of NOx and NO can be decreased by 85%and 84%respectively,and the stable concentrations were decreased to 40mg/Nm3 and 18mg/Nm3,while the concentrations in the plant decreased to 3 mg/Nm3 and lmg/Nm3,respectively,by 90%and 94%respectively,after the antifogging chemicals was added into the pickling tank.The surface of the pickling solution can be covered by the dense foam layer,and the evaporation of acid mist and the heat loss can be reduced.Therefore,the amount of steam can be greatly reduced and the pickling rate was improved.The novel pickling technology based on Fenton oxidation process by using hydrogen peroxide was developed,and therefore the environmental problems including NOx and total nitrogen and sludge were thoroughly solved.The recovery of waste acid in the preparation of ferrous sulfate by-products,meanwhile waste acid was recycled.Field test showed that the pickling time of several kinds of stainless steel was 30～60min.After pickling,the steel surface was clean and bright,and the product could meet the related quality requirements,and the average yield was 97.9%.The main components in the crystals is FeSO4·7H2O and the crystallization rate is about 61.2%.Th nickel content is 4.99%and it will be significantly improved in the removal of water content.At this point,the acid solution with the metal content of 17%and sulfuric acid content of 28%can be directly returned to the pickling tank,and it can further utilized for pickling by adjusting the HF concentration. |
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