The Study Of The Circulatory Of FeCl₃ System On Descaling And Iron Salt Resource Utilization

Most steel plates were descaled with HCl before cold rolling.The concentration of HCl is about 15%?25%.Waste HCl?acid-fog and wastewater were produced during pickling processes,may lead to resources waste and environmental contamination.In the present study,a mixture of FeCl3 and light concentration of HCl substitute high concentration HCl,which was used as rust remover for cold rolled steel plate.Of which the mixture solution had less impact on environment,since the discharge liquid of volatile HCl and the recovery of FeCl3 could be used as pickling system with the addition of HCl after being oxidized into ferric chloride.SME generally entrust qualified environmental companies to deal with waste acid.This way not only increases the production cost of thin steel,but also can not directly recycle the acid and iron resources in waste acid in the plant.To solve the problem,based on the pickling system of the cold rolled sheet steel in Guangdong Province,which yielded 100,000 tons per year,results of this study presented as follows:1.Ferric chloride was used to substitute for HCl in cold-rolled steel sheet cleaning circulation system,as the discharge liquid as FeCl2 could be reused in the rust removal system with oxidation.Compared to the concentration HCl pickling derusting circulating system,the cost of Ferric chloride derusting is 4,700 yuan lower than the hydrochloric acid pickling for consideration of economic benifits;For the environmental consideration,Ferric chloride was directly used in the derustion in the reaction,therefore,acid mist did not produced in the process of rust removing with the dilute HCl.The key technology of online circulation system of ferric chloride corrosion remover is the regeneration oxidation of ferrous chloride,in case the oxidation efficiency meet 75%,the remover online system could be recycled with the FeCl3.2.The experiment part is divided into four parts:preparatory experiment,preparatory experiment,continuous experiment and coagulation experiment.The experimental results is determined by potassium dichromate titration of iron ions,the experiment is comparing the different ways of oxidation,the oxidation efficiency and cost,choose to take in oxygen and add 1%NaNO2 catalyst and material liquid circulation quantity is 6 r3/L,can complete oxidation rust removing waste liquid in 120 min.Coagulation experiment:coagulant using FeCl2 acid solution as raw material,the preparation and catalytic oxidation with NaNO2 coagulant dosing quantity of 0.7 mg/L,pH value between 7?8,dyeing waste water can be treated effective.The resource-based technology not only cost low,applicable to small and medium enterprises,but also made it possible to online cycle,the development of SME provide valuable advice.