Method for recycling neutral salt wastewater produced by metal pickling

Abstract

The invention discloses a method for recycling metal hydroxide sludge resources generated from neutral salt wastewater produced by pickling in iron and steel industry after neutralization with liquidalkali. The method comprises the following steps: firstly, the neutral salt wastewater is reduced, and liquid alkali is added; metal hydroxide sludge (with solid content being 50%) is obtained after concentration with an ultra-micro separator and filter pressing with a filter press and stirred and blended with raw materials for smelting stainless steel, a product is fed into a blast furnace (or anelectric furnace) for direct smelting of stainless steel after meeting the furnace feeding requirement, valuable metal ions in the neutral salt wastewater can be recovered, harmful and hazardous solid waste is not produced, waste is changed into wealth, economic benefits of sewage treatment are increased, and treatment cost is reduced.

Description

technical field [0001] The invention belongs to the field of disposal of hazardous sludge produced after environmental protection wastewater treatment, in particular to a method for recycling and utilizing metal hydroxide sludge resources generated after neutralization of neutral salt wastewater produced by pickling in the iron and steel industry with liquid caustic soda. Background technique [0002] With the rapid development of my country's technological economy, it has led to the rapid development of the steel industry. The original steel parts must be pickled before cold rolling, electroplating, and spraying to remove oxides on the surface and produce pickling wastewater. The main components of pickling wastewater are for SO 4 2- 、H + , Fe 2+ 、Na + 、Cr 6+ , F - 、Me n+ 、Ni 2+ etc. Pickling wastewater can generally be divided into neutral salt wastewater and mixed acid wastewater, and the main pollutants in mixed acid wastewater are: Fe 2+ , F - 、Me n+ 、Ni 2+ W...

AI Technical Summary

Problems solved by technology

[0004] Practice has proved that the combined process of "chromium reduction + lime neutralization + precipitation + filtration" in the prior art has the following disadvantages: (1) the amount of sludge is large, the sludge composition is complicated, it is difficult to recycle, it is not recyclable, and it is very harmful. The sludge is mainly composed of hydroxide precipitation, excess lime, calcium sulfate, lime powder impurities, PAC / PAM chemical water (accounting for about 50% to 65%), etc.; the content of valuable metal salts is very low, and there is basically no re-refining , recovery value, more impurities and moisture make the amount of sludge produced is very huge, and due to the presence of heavy metals (such as chromium compounds), this kind of sludge has been included in the list of hazardous solid waste

[0005] (2) The landfill disposal of hazardous sludge causes waste of metal resources and damage to the environment. The sludge containing acid and chromium wastewater contains a large amount of valuable metal substances such as iron, chromium, nickel, etc., and 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

Images