The problems in processing the acid ferrous-containing rinsing water and spent pickling solutions are considered. The first-ever in metallurgy zero liquid discharge (ZLD) industrial wastewater treatment systems of a transformer cold rolling plant at the Verkh-Isetsky steelworks in Sverdlovsk (now — LLC VIZ Steel is a part of Novolipetsk Steel Group of Companies) is described. The experience of the VIZ Steel, particularly in relation to industrial wastewater treatment and sludge processing, is useful for designing ZLD industrial wastewater treatment systems of metallurgical, machine-building and metalworking enterprises. The recommendations for organizing the ZLD industrial wastewater treatment systems in the pickling plants with the repeated use of the treated rinsing water and processing the spent pickling solutions and the sludges are presented. For practical calculations of clarifiers the empirical formulas are offered. Process flow diagram of acid ferrous-containing rinsing water treatment is suggested. Acid ferrous-containing rinsing water treatment includes the following processes: rinsing water neutralization to pH 9-10,5 by 5 % calcium hydroxide and partial ferrous oxidation by air; addition of anionic flocculant and active gypsum priming to the neutralized rinsing water; settling of rinsing water conditioned by reagents in clarifiers; treatment of clarified water on deep bed sand filters; reclaimed water treatment.
To neutralize the waste pickling solutions and rinsing water, resulting from cleaning metal products s surface of rust by acids solutions, lime is used. Being cheap, this method of sewage neutralization has considerable drawbacks. Forming in the technological pipes strong gypsum depositions and low specific productivity of the equipment for sediment dewatering are most significant of them. Characteristic of aggressive industrial sewage, formed at pickling of ferrous metals presented. Methods of elimination of drawbacks of industrial sewage neutralization by lime considered, including stabilization of neutralized industrial sewage and control of properties of the sediment formed. It was noted, that stability of the circulating water can be provided by accelerating of crystallization of the forming gypsum sediments by introducing in it fine priming powder and heating the neutralized water up to 65-70 °С followed by thermal softening of a part of circulating water, removed out of the circulating system. It was shown, that the heating of the water and the ongoing changes of the composition and properties of the sediment result in decrease of filtration resistance 2-3 folds, increase of deposition speed 3-4 folds and decrease the sediment volume 1.5-2 folds comparing with lime neutralization in cold water. Calculated dozes of lime at the heating were taken the same as at the regular lime neutralization. Elimination of the circulating water oversaturation by bi-water gypsum can be reached also by addition into the water of powder-like gypsum pulp - priming powder for microcrystals of the gypsum, followed by aeration during 30-40 min. This method was tested under industrial conditions. Technological properties of the forming sediment can be improved by sediment treatment by flocculants and preliminary heating of the neutralized water up to 65-70 °С. Control of technological properties of the sediment is done by addition of flocculants and heating of the neutralized water. Recommendations for improving operation of the neutralization facilities presented with indicating particular technological parameters of the equipment operation for sewage and sediment treatment.
Many steel-works discharge the sediments from BOF gas cleaning systems sludge pans into the waste accumulators without dewatering, therefore implementation of facilities of their treatment is an extraordinarily actual task. Besides the BOF gas cleaning systems sewage sediments are attributed to a substance rich or relatively rich by iron, which can be utilized in metallurgical production after dewatering. Application of synthetic organic flocculants for sediments conditioning is one of most effective methods of dewatering equipment operation intensification. Results of experiment tests on the treatment of real BOF gas cleaning systems sewage sediment by a high-molecular organic flocculants namely Servey FL9, Nalco 71661 and Nalco 8172 PULV. It was shown, that Nalco 8172 PULV is most effective reagent for the sediment conditioning. The effective doze of high-molecular anion flocculant for treatment of BOF gas cleaning systems sewage sediment before the gravitational thickening and further mechanical dewatering is 0.15 g of active substance per1 kg of dry sediment substance. Technological parameters of dewatering equipment determined when using high-molecular anion flocculant for intensification of the treatment process of BOF gas cleaning systems sewage sediment: the specific load for thickeners by dry sediment substance is 300–400 kg/(h·m2), the specific load for disc vacuum-filter by dry sediment substance is 60–70 kg/(h·m2). Content of suspended particles in bright water from thickeners and filtrate from vacuum-filter is less than 100 mg/dm3.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.