Method for stainless steel annealing and pickling wastewater neutralization and sludge recycling

Abstract

The invention discloses a method for stainless steel annealing and pickling wastewater neutralization and sludge recycling. The method comprises following steps: setting intermediate preset values asfollows: pH1=X and pH2=Y; adding lime milk to pickling wastewater to enable pH value of the pickling wastewater to reach the intermediate preset value pH1, adding a flocculating agent, and performingstirring and standing; adding the lime milk to primary wastewater obtained in the previous step continuously, stopping addition of the lime milk when the pH value of the pickling wastewater reaches the intermediate preset value pH2, replacing the lime milk with a sodium hydroxide aqueous solution until terminal pH is neutralized to be 10.5, adding the flocculating agent, and performing stirring and standing. The method has beneficial effects that fractional precipitation of sludge is realized with a fractional neutralization method by controlling the pH value, excessive input of CaO is avoided, cost of denitrification treatment is reduced, the effluent discharge index is guaranteed, differentiated recycling is realized according to composition characteristics of fractional neutralization products, and the economic maximization effect is realized on the premise of safety and environmental protection.

Description

technical field [0001] The invention belongs to the field of recycling solid and liquid waste resources in stainless steel production, and in particular relates to a method for neutralizing stainless steel annealing and pickling wastewater and a method for utilizing sludge obtained after neutralization. Background technique [0002] Stainless steel is widely used because of its excellent corrosion resistance and good appearance. In the production process of stainless steel, it is inevitable to go through annealing, normalizing, quenching, welding and other processing processes, and black oxide scales often appear on the surface. Oxide scale not only affects the appearance quality of stainless steel, but also has an adverse effect on the subsequent processing of the product, so it must be removed by surface treatment methods such as pickling and polishing before subsequent processing. The pickling process of stainless steel generally starts with sulfuric acid pre-pickling to...

AI Technical Summary

Problems solved by technology

[0003] In order to overcome the deficiencies in the prior art, the object of the present invention is to provide a method for neutralizing stainless steel annealing and pickling wastewater and sludge utilization, to solve the problem of excessive input of neutralizing agent calcium oxide (CaO) in annealing and pickling wastewater; The high concentration of calcium ions in the effluent affects the nitrogen removal efficiency; solves the problem of recycling precious metals in sludge; solves the problem of flexible use of fluorine-containing sludge