| Steel plate need pickling before rolling. According to the production of steel rolling, there was one or more pickling line in cold rolled sheet steel enterprise. Pickling line is equipped with pickling and rinse process. Hydrochloric acid is used for pickling solution mostly. In general, water is used for washing liquid. In the process of cold rolled sheet steel pickling, the huge consumption of hydrochloric acid and water with large amounts of waste hydrochloric acid, acid mist and acidic waste water is a commonly existed problem. There is a lot of iron resources in waste hydrochloric acid and acidic waste water. Traditional way of handling will cause the waste of resources.Take a sample from a cold rolled sheet steel enterprise with annual output of 100,000 tons. By measuring the hydrochloric acid, water and other materials flow in a pickling line and analyzing the material balance, the tentative plan of cold rolled sheet steel pickling line of hydrochloric acid and water circulation system has been constructed. The requirements of circulation system can be completely met by the existing technology and equipment conditions. In this system, the waste hydrochloric acid regeneration, acid mist recycling, partial backflow of acidic waste water were set in a whole. The hydrochloric acid and water closed-circuit circulation were realized in this circulation system and the iron resource was fully recycled by the way.Waste acid regeneration technology was the core of the circulation system technical support, the regeneration efficiency and treatment effect was the key. At present, high temperature roasting method, evaporation separation method, membrane distillation method and solvent extraction are this kind of technology that meets the requirements of this set of system of waste acid regeneration technology. Among them,High temperature roasting method and evaporation separation method are the mature technology that used in large iron and steel enterprises already.This study aims to realize recycling utilization of waste hydrochloric acid at the scene of the acid pickling. Using proposed solvent extraction to separate hydrochloric acid and iron resources in waste hydrochloric acid. Exploiting typical technology and key equipment for small and medium-sized iron and steel surface treatment enterprises. The study found that annual production of 100,000 tons of the typical cold rolled sheet enterprise was expected to save hydrochloric acid 577.7 t,water 5197.4 t, iron resources 50.55 t one year with the construction of cold rolled sheet steel pickling line of hydrochloric acid and water cycle system, significant environmental and economic benefits were reflected in this system. It is difficult to oxidize ferrous iron into ferric iron in waste hydrochloric acid, after ferrous iron was oxidized by hydrogen peroxide in industrial grade, the volume ratio of Hydrogen peroxide dosage and waste acid was 2:1, the iron mass fraction of waste hydrochloric acid was 5.36%, the mass concentration was 60.5 g/L, about 10% of hydrochloric acid volatile was produced in the process of oxidation. Using N235, P204, TBP, TOA to extract ferrous iron directly and found that the extraction ability of them are less than 20% for one stage extraction in the case of O/A=1:1, the extraction ability was relatively low but it has guiding significance for exploration of multi-stage extraction. |
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