Method and device for treating iron-containing waste sulfuric acid

Abstract

The invention discloses a method for treating iron-containing waste sulfuric acid. The method comprises the following steps: adding concentrated sulfuric acid into the iron-containing waste sulfuric acid until the sulfuric acid concentration in the mixed solution is higher than 45wt%; at room temperature, separating out dissolved iron in the mixed solution basically in the form of ferrous sulfate crystal; separating solid and liquid mixtures; discharging solid ferrous sulfate; diluting a part of the liquid or the entire liquid by using water to obtain regenerated diluted sulfuric acid; freezing the other part; subsequently performing solid and liquid separation; discharging water from the solid; taking the liquid as regenerated concentrated sulfuric acid; or directly freezing the solid and liquid mixtures and then performing solid and liquid separation; discharging the water of the solid and the ferrous sulfate crystal; diluting a part of the liquid by water to obtain regenerated diluted sulfuric acid, and taking the other part as regenerated concentrated sulfuric acid. The invention also discloses a device for treating the iron-containing waste sulfuric acid. The sulfuric acid treated by the method and the device disclosed by the invention is basically free of iron component, can be effectively reutilized, is high in concentration and can be used as mixed concentration sulfuric acid or reused for acid washing after being diluted, so that economical and high-efficiency treatment of the waste sulfuric acid is realized.

Description

technical field [0001] The invention relates to the technical field of environmental protection, in particular to a method and device for treating waste sulfuric acid containing iron. Background technique [0002] Steel wire factory, steel factory and hardware electroplating factory have a pickling process, which widely uses sulfuric acid, the purpose is to remove impurities such as iron oxide scale attached to the surface of the steel, so as to facilitate the next process to process into qualified products. In my country, the iron and steel industry produces about 60kg of pickling waste liquid per ton of steel produced, and the annual discharge of pickling waste liquid is nearly 1 million m 3 . During pickling, immerse the steel in dilute sulfuric acid with a concentration of about 15wt%, and wash it repeatedly, so that the oxide scale and the surface of the steel react with sulfuric acid to dissolve. After repeated use of sulfuric acid so many times, the acidity decrease...

AI Technical Summary

Problems solved by technology

The disadvantage is that it is difficult to directly remove more than 80wt% of iron in waste sulfuric acid by cooling and crystallization for the situation that the acidity of waste sulfuric acid for pickling in general factories is less than 5wt%.

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