RU2214464C1 - Method of processing zinc cinders - Google Patents

Abstract

FIELD: non-ferrous metallurgy; wet classification of zinc cinders. SUBSTANCE: proposed method includes hydraulic classification of zinc cinder at drainage of overflow for neutral leaching and directing underflow to ball mill for grinding; hydraulic classification and grinding are performed in closed cycle at delivery of used electrolyte to sand fraction grinding stage at pH of pulp escaping from mill ranging from 3.5 to 4.0. EFFECT: facilitated procedure; improved quality of zinc-containing solution. 1 dwg, 1 tbl

Description

 The invention relates to the field of non-ferrous metallurgy, in particular to methods for wet classification of zinc cinders.

 A known method of processing zinc cinder by dividing the products of firing on hydrocyclones into classes (-0.2-0.3 mm) and (+0.2 mm). The upper discharge (class -0.2-0.3 mm) enters the neutral branch of the leach shop. The lower discharge - sand product (class + 0.2-0.3 mm) is fed to additional leaching under more severe conditions in special containers (see Bulletin "Non-ferrous metallurgy", 1978, 2, pp. 23-24).

 The disadvantage of this method is the high yield of sand fractions after pre-leaching, which must be further processed in order to extract zinc, for example, the Waelz process.

 A known method of processing zinc cinders, including the operations of classifying zinc cinder into large, medium and fine fractions, their fluidization, acid leaching with an oxidizing agent (see A. S. of the USSR 1116735, class C 22 V 19/22, publ. Bull. 25 from 07/07/86).

 The disadvantages of this method include the high silica content of 0.31 g / l in the zinc sulfate solution, which impairs sedimentation and filtration of the pulps.

 The closest in technical essence and the achieved result is a method of processing zinc cinders, including hydraulic classification with the direction of the upper discharge containing fine fractions of the cinder for neutral leaching and the allocation of the sand part (+0.2 mm) (lower discharge) with its supply to the ball mills. Next, the crushed product enters acid leaching at an acidity of 10-25 g / l. After leaching, the pulp enters the cone classifier. The upper drain of the cone is returned to the flushing of the cinder near the KS furnaces, and the lower drain is again leached in packs, but with a higher acidity of 25-30 g / l. The lower discharge of the cone (sands) is then sent for re-leaching or for drying and Waelz (see A.P. Snurnikov. Zinc hydrometallurgy. M: Metallurgy, 1981, pp. 93-97) (the closest analogue).

The method has the following disadvantages:
- the multi-stage process of processing the sand fraction of the cinder and a high yield of sand up to 2000 t / year, which must be directed to Waelz. Preparation of sand for Waelz requires a separate thread from zinc cakes with obligatory drying in a tumble dryer;
- a large transition of silica to a solution of up to 2-3 g / l with high acidity of leaching of sand 10-30 g / l, which affects the sedimentation, filterability and choice of solid from the hydrometallurgical cycle.

 The technical result of the invention is the exclusion of the output of the sand cinder fraction (+ 0.2-0.3 mm) and the production of zinc solutions with a minimum soluble silica content. The specified result is achieved by the fact that in the method of processing zinc cinders, including hydraulic classification of zinc cinder with the direction of the upper drain to neutral leaching, and the lower drain (sand fraction) for grinding into a ball mill, hydraulic classification and grinding is carried out in a closed cycle with the supply of spent electrolyte to the stage of grinding the sand fraction of ore at a pH of pulp leaving the mill, in the range of 3.5-4.0.

 The method is as follows (see drawing).

 Pulp after separation of large lumps (+ 3-5 mm) on the sieves is sent to the receiving tank of the classification unit. pulp pH 4.5-5.0.

 From the receiving tank, the pulp is pumped to hydrocyclones. The upper discharge of the hydrocyclone is directed to neutral leaching, and the lower discharge (sand cinder fraction), together with the spent electrolyte, is sent to grinding in a ball mill. The pH of the pulp leaving the mill is maintained within 3.5–4.0 and is regulated by the amount of supplied electrolyte. The pulp leaving the mill is sent to a receiving tank and, together with the initial pulp coming from the kiln, is fed to hydrocyclones for classification.

 The proposed method is tested in an industrial environment.

 Tests have shown that feeding the spent electrolyte into a closed cycle of classification and grinding directly into a ball mill together with the sand fraction of the cinder at a pulp pH exiting the mill in the range of 3.5–4.0 eliminates the output of the cinder sand fraction (+0.2 -0.3 mm) and obtain zinc solutions with a silica content of less than 1 g / l, which does not affect sedimentation and filtration at such concentrations.

 So, with a decrease in pH less than 3.5, the silica content in solutions increases, and with an increase above 4.0 in the classification and grinding cycle, the sand fraction of the cinder accumulates (+ 0.2-0.3 mm) and it enters with the upper discharge of the hydrocyclone neutral leaching, which creates difficulties in the subsequent filtration of zinc cakes.

 The verification of the method was carried out as follows.

 Pulp from the roasting entered the receiving tanks. The solid content in the pulp was 200 g / l, including the sand fraction of the cinder (+ 0.2-0.3 mm) 24.8 g / l. With a lower discharge of hydrocyclones, 1.8% of the volume of pulp entering the receiving tanks with a solid content of 2100 g / l, including a sand fraction of 1260 g / l, was released. The bottom discharge was mixed with the spent electrolyte of zinc electrolysis (zinc 45 g / l, sulfuric acid 170 g / l), the flow rate of which was maintained by the pH of the pulp 3.5-4.0, leaving the mill during operation.

 Tests showed that the content of the sand fraction of the cinder (+ 0.2-0.3 mm) in the upper discharge of hydrocyclones was at a constant level and amounted to 0.5 g / l, which is acceptable for the operation of the leaching of firing products. The silica content in the zinc-containing solution was 0.1 g / L. With this silica content in the solution, sedimentation and filtration of the pulps took place without complications with a minimum consumption of flocculant.

 The table shows the comparative verification data of the known and proposed method of processing zinc cinder.

 As can be seen from the data obtained, when using the proposed method, the output of sands is excluded, which must be disposed of using multistage technology, including drying of the classified unfiltered product and Waelz. The silica content in zinc-containing solutions coming out of the classification plant is reduced from 2.2 to 0.1 g / l.

Claims (1)

 A method of processing zinc cinders, including hydraulic classification of zinc cinder with the direction of the upper drain to neutral leaching, and the lower drain - sand fraction of the cinder for grinding into a ball mill, characterized in that the hydraulic classification and grinding is carried out in a closed cycle with the supply of spent electrolyte to the grinding stage sand fraction of the cinder at a pH of pulp leaving the mill, in the range of 3.5-4.0.

Images