Ferrous sulphate-calcium hypochlorite method
Cyanogen is one of the most harmful pollutants to nature and human beings. HCN 50 mg and KCN 150~300 mg will kill human, and when CN- concentration in water reaches 0.3~0.5mg/L, it can kill fish. During the washing process of blast furnace gas in iron and steel enterprises, cyanide in the gas is washed and absorbed by water. With the continuous recycling of the washing water, the cyanide concentration in the water keeps rising. When the concentration reaches a certain level, the recycling water's ability to dissolve cyanide becomes smaller and smaller until it no longer has the washing and absorption effect of cyanide. , causing the blast furnace gas washing system can not run normally, seriously affecting the steel production. Therefore, it is necessary to replenish a certain amount of fresh water and discharge a corresponding amount of high concentration cyanide wastewater in the blast furnace gas washing cycle system. In order to eliminate the environmental pollution caused by the discharge of high concentration cyanide containing wastewater, it is necessary to adopt appropriate methods to treat it, so that it can meet the national discharge standards or continue to recycle.
At present, there are many cyanide treatment methods, such as acidification recovery method, membrane separation technology, chemical coupling method, extraction method, natural degradation method and chemical oxidation method. In order to remove cyanide from wastewater with high concentration of cyanide, ferrous sulfate was used to form complexing precipitate. Cyanide wastewater was treated with calcium hypochlorite and cyanide ion was oxidized by hypochlorite to remove cyanide. The chemical compound method has wide sources, less consumption, low cost, less equipment investment and convenient operation, which can treat most of the complex cyanide. It has obvious advantages in the treatment of cyanide wastewater with high concentration, and has been paid more and more attention. However, the treatment degree of this method is not enough to meet the emission standard, especially when the cn-mass concentration is lower than 10 mg/L, the effect is worse. Calcium hypochlorite can effectively deal with low concentration of free cyanide ion, and is easy to use, a wide range of pharmaceutical sources. However, calcium hypochlorite treatment of cyanide wastewater can not recover cyanide, in the high concentration of cyanide wastewater dosage, very uneconomical. Therefore, using a single method to treat cyanide wastewater in iron and steel enterprises is not economical in cost or can not be treated to meet the standards.
However, ferrous sulphate-calcium hypochlorite method can be used to treat cyanide washing water from blast furnace of iron and steel enterprises economically and effectively, and make it meet the discharge standard.