The nature and quantity of wastewater from cold rolling mills are closely related to product varieties and process conditions. It mainly includes three types of wastewater: oily and emulsion wastewater, acid-base wastewater, and chromium-containing wastewater. There are many types of pollutants in cold rolling wastewater, complex components, and large changes in water volume and composition, which bring great inconvenience to wastewater treatment. The effect of using 18 million molecular weight anionic polyacrylamide for wastewater treatment in iron and steel plants is very significant .
The characteristics of wastewater from steel mills: 1) There are many types of wastewater, including waste acid, acid-base wastewater, oily and emulsion wastewater. Depending on the composition of the unit, there are sometimes chromium-containing wastewater and cyanate-containing wastewater; 2) There are not only many types of cold-rolling wastewater, but each type of wastewater has the largest amount compared with similar wastewater produced by other parts of the steel plant ; 3) The composition of wastewater is complex. In addition to acid, alkali, oil, emulsion and a small amount of mechanical impurities, it also contains a large amount of metal salts, mainly iron salts. In addition, there are a small amount of heavy metal ions and organic components; 4) The wastewater changes greatly. Due to the differences in the output, production capacity and operating rate of each unit of the cold rolling mill, the volume and composition of the cold rolling waste water to be treated centrally fluctuate greatly; 5) The temperature of the cold rolling waste water mainly comes from the heating of the production process rather than direct cooling. When treating oily and emulsified wastewater, separate heating is often required
The main pollutants of steel plant wastewater. Due to the high temperature of steel plant wastewater, as the water evaporates, inorganic ions and organic matter are concentrated and enriched, and various salts (such as chloride, sulfate, carbonate, total dissolved solids, Iron and manganese etc.) content gradually increased. The traditional steel mill wastewater treatment process basically has no effect on salt removal, resulting in higher total alkalinity and total hardness in the circulating water, enriched salt content, accelerating the scaling and corrosion of pipelines and equipment, and reducing thermal conductivity and equipment The service life will ultimately affect the product quality. Therefore, how to reduce the salt content of the reused water is very important. The composition of the wastewater from the iron and steel industry is complex and needs to be recycled through flocculation, precipitation, cooling, and a circulating pool. The polyacrylamide flocculant is used in the flocculation precipitation process to remove the circulating water and impurities in the production process. Anionic polyacrylamide is required and the molecular weight is required to be more than 10 million.
The production process of the iron and steel industry includes material selection, sintering, ironmaking, steelmaking (continuous casting), steel rolling and other production processes. The iron and steel industry wastewater mainly comes from the production process water, equipment and product cooling water, flue gas washing and site washing, etc. , But 70% of waste water still comes from cooling water. Indirect cooling water is only polluted by heat during use, and can be reused after cooling; direct cooling water contains pollutants due to direct contact with product materials, and needs to be treated. It can be reused or used in cascade. Mine wastewater treatment is characterized by large changes in water volume and water quality, and the wastewater is acidic. The scale of mine wastewater treatment must be reasonably determined, and the water quality of the treated water should not fluctuate too much. Set up a regulating pool and a regulating reservoir, and collect the water first, and then treat it. Mine wastewater is sulfuric acid type wastewater, with a general pH of 1.6. Such a low sulfuric acid content obviously has no recovery value, so neutralization is often used. Method. The treatment of mine acid wastewater generally adopts the lime neutralization method.
Iron and steel plant wastewater treatment uses anionic polyacrylamide as a flocculant to treat wastewater produced in steel plants. Anionic polyacrylamide only needs to be used in industrial wastewater treatment. For suspended particles, particles with a high concentration of positively charged particles, neutral or alkaline sewage, iron and steel plant wastewater, electroplating plant wastewater, metallurgical wastewater, coal washing wastewater, etc. The effect of sewage treatment is the best.
The iron and steel industry not only brings a lot of economic benefits, but also causes inevitable waste water pollution. The main source of waste water is water used in the production process, equipment cooling and cleaning water, and product coolant site cleaning water. . Anionic polyacrylamide can effectively adsorb the metal ions in the sewage to form a flocculent group, and finally achieve the effect of cleaning the sewage.