SU1178796A1 - Method of preparing chloride nickel electrolyte for nickel refining - Google Patents

Abstract

METHOD FOR PREPARING HPORIDNOGO NICKEL ELECTROLYTE FOR REFINING OF NICKEL comprising hydrolytic clean anolyte of impurities from feed oxidant and a catalyst obtained by treating portion nickel electrolyte reagent repulping cakes of a mineral acid, replenishment of nickel salts deficiency and direction obtained catholyte in the electrolysis of Whitlock ichayuschiys in that, in order to reduce the cost of the process and prevent environmental pollution, the neutralizer is obtained by treating a part of the nickel oxide solution Calcium to obtain nickel hydroxide and calcium chloride mother liquor, nickel hydroxide is fed to hydrolytic purification, cakes are repulped with sulfuric acid solution obtained after repulping cakes, nickel sulfate solution; And the solution coming to compensate for nickel deficiency in the form of sulfate salt, calcium chloride at an excess concentration of 40 to 60 g / l to produce nickel chloride, sent after filtration, and evaporation into the electrolyte. 90 SO od

Description

The invention relates to the metallurgy of heavy non-ferrous metals and can be used in the electrolytic refining of a rough; Nickel with soluble anode. five

The aim of the invention is to reduce the cost of the process and prevent pollution of the environment.

The method is carried out as follows.

The use of calcium oxide as an alkaline reagent for the preparation of nickel hydroxide and sulfuric acid for processing iron-cobalt cakes provides, during the preparation of electrolyte electrolyte to electrolysis, a low-soluble, well-filtered calcium sulfate salt and eliminates the accumulation of excess soluble electrolyte chloride salt in the electrolyte . The principal difference between the described method of preparing the chloride electrolyte and the known one is that to compensate for the deficit. Nickel does not use chloride, but 25 sulphate nickel salt without accumulating sulphate ions in electrolytes. The conversion of nickel sulphate salt into chloride salt is carried out without additional consumption of reagents with the use of calcium chloride circulating solution, obtained by precipitation of nickel hydroxide with calcium oxide (lime).

Mixing sulphate nickel races-35 with calcium chloride solution with an excess of calcium chloride 40–60 g / l reduces the solubility of calcium sulfate and ensures that during the subsequent evaporation of the solution 40-2-2.5 times the concentration of calcium chloride reaches 100-150 g / l and the input of sulfate ions is less than the solubility limit of calcium sulfate in the nickel chloride electrolyte, which 45 prevents plastering of pipelines and equipment in electrolysis workshops. Excessive calcium chloride concentration of less than 40 g / l in the subsequent evaporation of the solution in 2 - 2.5 to 50 times leads to the formation of nickel electrolyte supersaturated in calcium sulfate and crystallization of gypsum (calcium sulfate) on the walls of the equipment. dovani At an excess concentration of 55 calcium chloride over 60 g / l followed by evaporation of the solution, the concentration of calcium sulfate in the nickel electrolyte decreases above the required limit, and the quality of the electrolyte deteriorates (its viscosity increases). The depth of evaporation of the chloride solution by a factor of 2–2.5 is determined by injecting fresh water into the nickel electrolyte with the production solutions.

FIG. 1 shows a schematic diagram of the prototype preparation of nickel chloride electrolyte; in fig. 2 is a scheme for preparing the chloride electrolyte according to the proposed method.

Example. The determination of nickel hydroxide was carried out using calcium oxide from a nickel chloride electrolyte of the calculated composition g / l: NiClg 200 CaCl2 100

Compound in electrolyte is based on the balance of salts when using (not washed with calcium chloride) nickel hydroxide on hydrolytic purification of the electrolyte from the trough and cobalt. The consumption of calcium oxide on the complete precipitation of nickel hydroxide at pH 8–8.5 was 130% of stoichiometry. The resulting nickel hydroxide was filtered off, the precipitate was used as a neutralizer on iron-cobalt cleaning of the fields: spruce electrolyte, and a nickel sulfate solution (concentration 210 g / l) was added to the mother liquor containing 270 g / l of calcium chloride while stirring g / l. Calcium sulphate was filtered and washed from the nickel on the filter with water. At a flow rate of wash water of 2 liters per 1 kg of wet sludge, the nickel washing rate was 99.9%. The filtration rate of the calcium sulfate slurry was 0.8–1.0.

The effect of an excess concentration of calcium chloride on the solubility of calcium sulfate in a solution of nickel chloride (concentration of 150 g / l) is illustrated by this table.

It can be seen from the table that when an excess concentration of calcium chloride is 40–60 g / l, the solubility of calcium sulfate decreases by a factor of 4–5. Entering fresh water into the electrolyte with washing solutions requires an evaporation scheme to create a water-closed circuit. Nickel chloride solution 2 2, 5 times. Therefore, after evaporation of the solution 2.4-2.5 times, an excess calcium chloride concentration of 100-150 g / l is created and the solubility of calcium sulfate is reduced to 1.6-1.1 g / l, which ensures the concentration of sulfate during the preparation of nickel chloride electrolyte Calcium is 1.5 times lower than the solubility limit of this salt and prevents the gypsum on the equipment walls (the output of electrolyte to precipitate nickel hydroxide is 1.5 times greater than the amount of solution injected to compensate for nickel deficiency). After separation of the calcium sulfate precipitate, the nickel chloride solution was evaporated 2.5 times (containing 200 g / l of nickel chloride, 1.5 g / l of calcium sulfate) and was used to compensate for the nickel deficiency. Hydrosium nickel is used to neutralize the electrolyte during hydrolytic iron-cobalt cleaning. The deterioration of electrolyte purification and changes in the composition of iron-cobalt cake in comparison with the use of a nickel carbonate neutralizer were not detected. The cobalt cake content in both cases was 10–12%, nickel - 12–14%, and iron 23–26%. Iron-cobalt cake from cleaning chloride electrolyte was washed with water and repulped with a solution of sulfuric acid at a concentration of 150 g / l at T: W 1: 2. Nickel sulphate solution from repulpable cake containing 60 g / l of nickel was sent to the circulation to obtain chloride nickel The chloride electrolyte, after its reinforcement over nickel and hydrolytic purification from iron and cobalt, was directed to electrolytic refining of nickel with a soluble anode. The composition of the electrolyte g / l: NiCl / 200; CaClg 100; 0.8 The parameters of electrolysis: current density of 300 A / m, temperature 55 ° C; catholyte circulation 70 cm / Ah. The quality of cathode nickel corresponds to the brand. H - 1 (nickel content of 99.93%). The use of the proposed method provides, in comparison with the prototype, the following technical and economic advantages: the replacement of scarce and more expensive soda ash with calcium oxide (lime); reducing the cost of producing nickel chloride by eliminating the use of reduced nickel powder and chlorine; reducing the cost of repulping ferrous and cobalt cakes by using cheaper sulfuric acid instead of hydrochloric acid; improvement of environmental protection due to the production of solid calcium sulphate salt (gypsum) as a waste instead of sodium chloride salt solution, which requires conducting parks to solid sodium chloride salt with burial of this salt with waterproofing or additional construction of processing salt to commercial products. .

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Claims (1)

METHOD FOR PREPARING CHORID NICKEL ELECTROLYTE FOR REFINING NICKEL, including hydrolytic purification of anolyte from impurities with the supply of an oxidizing agent and a neutralizer obtained by treating part of the nickel electrolyte with a reagent, repacking cakes with a mineral acid, and replenishing the , in order to reduce the cost of the process and prevent environmental pollution, the neutralizer is obtained by treating part of the nickel solution with fecal oxide tion to obtain nickel hydroxide and mother solution of calcium chloride, nickel hydroxide is fed to the hydrolysis treatment, repulped cakes sulfuric acid solution "obtained after repulping cakes solution of nickel sulfate _solution,? coming to fill the deficiency of Nickel in the form of sulfate salt, treated with a mother liquor of calcium chloride at an excessive concentration of 40-60 g / l to obtain Nickel chloride, sent after filtration and evaporation in the electrolyte. I 1178796 2