Method for sludge reduction for cold rolling pickling wastewater in steel industry

Abstract

The invention belongs to the technical field of sludge reduction for cold rolling pickling wastewater in the steel industry, and discloses a method for sludge reduction for the cold rolling pickling wastewater in the steel industry. In the method disclosed by the invention, neutral salt wastewater and wastewater mixed with acid are completely and separately treated to obtain sludge containing hazardous wastes and general sludge respectively, and the sludge output of each unit is reduced by accurately adding chemical agents at each unit; in the technology for treating the neutral salt wastewater, caustic soda liquid is respectively added in a first stage neutralizing tank and a second stage neutralizing tank; in the technology for treating the wastewater mixed with acid, the treatment is performed by using a lime and austic soda liquid combination method; and in the treatment of a neutralizing tank, the pH value is controlled between 1.5 and 3.0, and the pH value during neutralization reaction is controlled between 8.2 and 8.7; and a flocculation process is adopted after the neutralization reaction, polyaluminum chloride, polyacrylamide and other flocculants are added for reacting and are mixed so as to enlarge pollutant particles. By use of the method, the output water can stably reach the standard, and the water treatment cost per ton is reduced.

Description

technical field [0001] The invention belongs to the technical field of sludge reduction treatment of cold-rolling pickling wastewater in the iron and steel industry, and in particular relates to a method for reducing the sludge volume of cold-rolling pickling wastewater in the iron and steel industry. Background technique [0002] The cold-rolling pickling wastewater sludge reduction treatment process in the iron and steel industry is an important energy-saving and emission-reduction technology. The original treatment process was initially introduced into China by foreign engineering companies along with the pickling production line, and was widely used in the treatment of cold rolling pickling wastewater in major iron and steel enterprises. The process flow can be referred to in the appendix image 3 . [0003] Some application examples of the original technology in domestic rolling mills can be seen: [0004] Jiuquan Iron and Steel Plant, "Stainless Steel Cold Rolling Was...

AI Technical Summary

Problems solved by technology

[0029] 1. The generated sludge is all chromium-containing sludge (the first class of pollutants is HW17 hazardous waste in the national hazardous waste catalog of China), so all the sludge needs to be disposed of as hazardous waste, which cannot be separated, so it needs to be treated a large amount of hazardous waste

[0030] The reason for this problem is that the original process reduced the neutral salt wastewater and combined it with the mixed acid wastewater for neutralization treatment, and the sludge of the two streams of wastewater co-precipitated and could not be separated.

Although this treatment method can save a set of sludge treatment equipment in the early stage of project investment, the cost of sludge treatment with hazardous waste in the subsequent treatment process is high, and the environmental benefits are not good

[0031] 2. The total amount of sludge generated is large, resulting in high sludge disposal costs and ton water disposal costs

[0032] The fundamental reason for the large amount of sludge produced is that the excess lime dosing method was used in the treatment process. In order to ensure that the fluorine ion in the effluent can reach the standard, the pH of the reaction was adjusted to 10-11. In this reaction pH range, lime The dissolution rate is low, causing a large amount of lime to settle with other sludge without reaction, which not only causes waste of chemicals, but also increases the total amount of sludge

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