Method for treating pickling wastewater in iron and steel industry

Abstract

The invention discloses a method for treating pickling wastewater in iron and steel industry. The method comprises the following steps: a) introducing pickling wastewater into a regulating tank, a chromium reduction tank and a heavy metal catcher; b) separating heavy metal precipitate produced in reaction from clear liquor through an ultramicro separating machine, carrying out primary fluoride removal on the clear liquor in a fluoride removal filter; c) feeding the mixed solution subjected to primary fluoride removal into a primary precipitating tank for separating non-ferrous precipitate from water, then carrying out secondary fluoride removal on the clear liquor in a fluoride reaction tank; and d) feeding the mixed solution subjected to secondary fluoride removal into a secondary precipitating tank for separating non-ferrous precipitate from water, and emitting the separated clear liquor into a clear water tank for storage. The method has high metal particle separation efficiency, the ultramicro separation machine has concentration effect, so no concentration tank is required for separating the precipitate from the clear liquor to save space and the labor force, the indexes of iron, chromium, nickel, fluoride and the like in the clear liquor emitted from the secondary precipitating tank can all meet the national-level standard requirement.

Description

technical field [0001] The invention belongs to the field of environmental protection wastewater treatment, in particular to a treatment method for pickling wastewater in the iron and steel industry. Background technique [0002] With the rapid development of my country's industrial economy, it has led to the rapid development of the steel industry. Steel components must be pickled before cold rolling, electroplating, and spraying to remove surface oxides and produce pickling wastewater. The pickling wastewater is mainly Composition is SO 4 2- 、H + , Fe 2+ 、Na + 、Cr 6+ , F - 、Me n+ , Ni, etc., where Cr 6+ , F - , Fe 2+ 、Me n+ as the main pollutant. [0003] The existing method of treating pickling wastewater adopts "chromium reduction + lime neutralization + precipitation + sand filtration". Add reducing agent and fully mix and react with wastewater to reduce hexavalent chromium to trivalent chromium, send the effluent to the pH adjustment tank, then put ...

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Problems solved by technology

[0005] (1) The amount of sludge produced is large, the composition of sludge is complex, it is difficult to recycle, it cannot be reused, and it is very harmful. The sludge is mainly composed of hydroxide precipitation, excess lime, calcium fluoride, lime powder impurities, and PAC / PAM agents , water (accounting for about 50%∽65%), etc., the content of valuable metal salts is very low, there is basically no value for re-smelting and recycling, and more impurities and water make the amount of sludge generated very large, and due to heavy metals presence (e.g. chromium compounds), such sludge has been included in the list of hazardous solid waste;

[0006] (2) Landfill disposal of sludge causes waste of metal resources and damage to the environment. Sludge produced by wastewater containing acid and chromium contains a large amount of valuable metal substances such as iron, chromium, nickel, etc., so it is disposed of in landfill. Not only does it cost a lot of hazardous solid waste disposal, but it also needs to occupy a large amount of land resources for landfill, which will affect the lives of surrounding residents and the quality of groundwater

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