Method for removing sulphur and iron of sodium aluminate solution

Abstract

The invention discloses a method for removing sulphur and iron of sodium aluminate solution. The method comprises the following steps: 1) adding an iron-based additive to the sodium aluminate solution containing S2- and iron in the ratio of F to S (mole ratio of Fe to S2- in the solution) of 0.1 to 2.0, and carrying out a reaction for 10 to 600 minutes at 30 to 130 DEG C; and 2) carrying out solid-liquid separation on the size after the reaction, so as to obtain the sodium aluminate solution and slag with the sulphur and iron removed. By adopting the method, the S2- and the iron in the sodium aluminate solution can be economically and efficiently removed at the same time, and the problems in Bayer process on treatment of high-sulfur bauxite that the consumption of alkali is increased, the iron content in the product is beyond the standard, and the equipment is corroded, can be solved.

Description

technical field [0001] The invention relates to a method for removing sulfur and iron from a sodium aluminate solution, belonging to the technical field of metallurgy. Background technique [0002] With the depletion of high-quality bauxite resources in my country and the further exploration of bauxite resources, the proportion of high-sulfur bauxite resources is gradually increasing. At present, my country's proven reserves of high-sulfur bauxite are about 560 million tons. The prospective reserves are as high as 2 billion tons. When high-sulfur bauxite is used in the Bayer process to produce alumina, the presence of sulfur in the ore will cause the following serious problems: 1) During the high-temperature dissolution process of the Bayer process, sulfur enters the solution after reacting with the caustic alkali in the circulating mother liquor, resulting in The alkali consumption in the alumina extraction process is greatly increased; 2) the sulfur entering the solution w...

AI Technical Summary

Problems solved by technology

When high-sulfur bauxite is used in the Bayer process to produce alumina, the presence of sulfur in the ore will cause the following serious problems: 1) During the high-temperature dissolution process of the Bayer process, sulfur enters the solution after reacting with the caustic alkali in the circulating mother liquor, resulting in The alkali consumption in the alumina extraction process is greatly increased; 2) the sulfur entering the solution will also form complex complexes with iron, which will increase the solubility of iron in the sodium aluminate solution, and in the subsequent crystallization of the sodium aluminate solution During this decomposition process, iron is precipitated from the solution, which affects product quality; 3) under suitable conditions, Na 2 SO 4 with Na 2 CO 3 Precipitated in the form of double salt, causing scarring on the heating surface of the mother liquor evaporator and stripper, reducing the heat transfer efficiency; 4) S in the solution 2- and S 2 o 3 2- After the concentration is increased, it will also corrode steel equipment

[0003] In order to eliminate the harm of sulfur to alumina production, a lot of research has been done on the elimination of sulfur impurities in the alumina production process at home and abroad, in addition to mineral processing (CN101767062A and CN101480633A), ore pre-roasting (CN101289210A and CN101456572A) and other ore pretreatment sulfur removal methods , has also done a lot of research on sulfur removal from sodium aluminate solution, mainly including: 1) removal of sulfate ions in the solution, including adding barium salt to desulfurize in the form of barium sulfate (CN 1458067), adding lime to hydrate sulfur Desulfurization in the form of calcium aluminate, and desulfurization in the form of soda alum by evaporation and crystallization of the mother liquor (CN101182026A), but this method can only remove sulfate radicals in the solution, and cannot remove S which has a great influence on the alumina production process. 2- ; 2) remove the S in the solution 2- and iron, adding a precipitant to make the S in the solution 2- Form desulfurization in the form of insoluble sulfides. After desulfurization, the sulfur-iron complexes in the solution are destroyed, resulting in a decrease in the solubility of iron in the solution and precipitation. Precipitants include zinc oxide, zinc-containing minerals, and copper-containing materials, but the cost of this method is high

In addition, there is also the addition of oxidants (such as sodium nitrate, hydrogen peroxide, manganese dioxide, oxygen / ozone, sodium hypochlorite, etc.) to make the S in the solution 2- A method of conversion to thiosulfate, sulfite, and sulfate that removes iron but not sulfur from solution

Therefore, high-sulfur bauxite has no substantial industrial utilization so far