RU2115749C1 - Method for processing tin-containing slags - Google Patents

Abstract

FIELD: methods for recovery of tin, lead, bismuth, zinc and some other nonferrous metals from slag formed in melting of tin concentrates and other tin-containing raw materials. SUBSTANCE: method includes adding to ground tin-containing slags alongside with sulfidizing agent and coal of calcium chloride in the amount of 1.5-2.1 kg per kg of tin contained in slag. Sublimation of tin and its associated elements is effected by chlorine sublimation annealing of mixture at temperature of 800-900 C in reducing atmosphere. EFFECT: reduced consumption of energy and excluded pollution of environment.

Description

 The invention relates to non-ferrous metallurgy and, in particular, can be used to extract tin, lead, zinc, bismuth and some other metals from slags formed during the smelting of tin concentrates and other tin-containing raw materials.

 There are various methods of pyrometallurgical processing of rich tin slag (smelting on ferrous slag, smelting with the introduction of ferrosilicon). The most complete extraction of tin from slags is achieved using methods based on the distillation of volatile tin compounds (chlorides and sulfides) from molten slags.

 A known method of roasting and chlorination of finely ground slag, iron series and concentrates containing non-ferrous metals [1]. The method involves preliminary firing of sulfides, obtaining a melt of oxides, which is mixed with a chlorinating agent and an oxygen-containing gas. The result is the "evaporation of non-ferrous metals from a molten iron oxide." The method provides a high extraction of tin and other non-ferrous metals, but requires significant energy costs for the melting of the entire mixture and is associated with environmental pollution during oxidative firing of sulfides.

 Closest to the proposed method is the process of fuming slag [2]. This process is widely used at tin enterprises in our country and abroad.

So, at the Albert Funk mining and metallurgical plant in Germany, crushed tin-rich slag of metallurgical production, poor concentrates and tin-containing products from dumps are mixed with a sulfidizing agent (pyrrhotite), granulated, dried, and subjected to melting at 1200-1400 ^o C and fumigation (purging) air melt to sublimate volatile oxides and sulfides of non-ferrous metals). Sublimates containing tin, lead, and arsenic are condensed in the form of fine dust, granulated, calcined to remove arsenic, and used as tin concentrate in the preparation of tin by known methods.

 The disadvantages of the prototype include, in addition to high energy costs due to the need to melt the charge, the formation of a large amount of exhaust gas, the purification of which from toxic oxides of arsenic and sulfur is complicated by the fact that the fuming process is periodic, so the composition of the exhaust gas changes dramatically over time.

 The purpose of the present invention is to significantly reduce energy costs and eliminate environmental pollution by highly toxic sulfur oxides.

This goal is achieved by the fact that in addition to sulfide and coal, in contrast to the prototype, calcium chloride in the amount of 1.5 - 2.1 kg per 1 kg of tin contained in the slag is added to the ground tin-containing slag, and sublimation of the tin and its companions is carried out by firing charge at 800 - 900 ^o C in a reducing atmosphere, eliminating the oxidation of sulfides and, consequently, the formation of sulfur dioxide.

 The possibility of a significant decrease in the temperature of sublimation of tin is due to the high vapor pressure of tin chlorides at relatively low temperatures.

 As a result of lowering the process temperature, there is no need to melt the mixture, therefore, energy costs are significantly reduced.

At a higher content of CaCl ₂ in the charge than indicated above, along with tin, the iron contained in the slag is chlorinated, which leads to a deterioration in the composition of sublimates.

With a lower content of CaCl ₂ in the charge decreases the completeness of sublimation of tin. A decrease in temperature below 800 ^o C leads to a decrease in the extraction of tin, and an increase in the firing temperature above 900 ^o C can cause sintering of the mixture and disruption of the firing process.

 The use of the process of firing in a reducing atmosphere for the sublimation of tin and satellites (lead, bismuth, indium) provides a significant reduction in environmental pollution by toxic sulfur dioxide, since sulfide oxidation does not occur in the reducing atmosphere.

 As studies have shown, the completeness of extraction of tin and its satellites when using the proposed method for processing slag is not lower than when using the prototype. However, the method allows several times to reduce environmental pollution and significantly reduce energy costs.

 The method is as follows.

A mixture containing crushed slag, coal added in an amount sufficient to create a reducing atmosphere during roasting and to ensure the process autothermal (6-8%), and a sulfidizer, for example pyrite or pyrrhotite concentrate, or sulfide intermediates for the enrichment of sulfide-cassiterite ores, are mixed with a concentrated solution of calcium chloride in an amount of 1.5-2.1 kg of CaCl ₂ per 1 kg of tin in the slag. The resulting mixture is granulated and dried at 100-150 ^o C. The dry mixture is calcined at 800-900 ^o C in a reducing atmosphere, eliminating the formation of sulfur oxides.

Example 1. Tin-rich slag containing in%: tin - 20.2, silicon - 11.2, aluminum - 5.1, calcium - 9.2, iron - 12.3, zinc - 1.3, sulfur - 0 , 1 mixed with a pyrite concentrate containing iron - 40.9, sulfur - 45.4, in a 2: 1 ratio, add 8% coal and CaCl ₂ in the form of a concentrated solution (1.8 kg CaCl ₂ per 1 kg of tin), they are granulated, dried at 150 ^o C and calcined at 820-840 ^o C in a reducing atmosphere (in the exhaust gases CO - 1-2%, oxygen and SO ₂ less than 0.05%). Extraction of tin in sublimation - 96%, the content of tin in the cinder from firing - 0.4%.

Example 2. As a sulfide-containing additive to slag, the composition of which is shown in example 1, sulfide-quartz tails of the finishing factory of the Novosibirsk Tin-processing plant of the following composition in% are added in a ratio of 1: 4: tin - 1.48, sulfur - 11.7, iron - 17.1. Coal and CaCl ₂ are added to the mixture in the form of a concentrated solution (per 1 kg of tin, 2.1 kg of CaCl ₂ ). The resulting mixture is granulated, dried and calcined at a temperature of 820-840 ^o C in a reducing atmosphere (the content of CO in the gas phase is 1-2%, oxygen and sulfur dioxide less than 0.05%). The residual tin content in the cinder is 0.17%, extraction into sublimation is 97%.

Example 3. To a mixture of slag, sulphide-quartz tails, the composition of which is shown in example 2 and coal, CaCl _{2 is} added in the form of a concentrated solution (1.2 kg CaCl ₂ per 1 kg of tin, which is lower than that provided by the formula). The resulting mixture is granulated, dried and calcined at 820-860 ^o C in a reducing atmosphere. The residual tin content of 4.7%, the extraction of tin in sublimation - 61%.

Example 4. To a mixture of slag, coal and sulphide-quartz tails, the composition of which is shown in example 2, add CaCl ₂ (1 kg of tin 1.4 kg CaCl ₂ , which is lower than the formula). The mixture is granulated, dried, calcined at 840-860 ^o C in a reducing atmosphere. The residual tin content in the cinder is 0.73%, recovery to sublimation is 87%.

Example 5. The mixture, the composition of which is shown in example 2, is fired at 750-780 ^o C (below the formula) in a reducing atmosphere. The residual tin content in the cinder is 1.19%, recovery to sublimation is 79%.

Example 6. The mixture, the composition of which is shown in example 2, is fired at 820-840 ^o C in an oxidizing atmosphere, (the oxygen content in the exhaust gases is 2-3%, CO is absent). The residual tin content in the cinder is 0.63%, recovery to sublimation is 88%. Flue gas contains sulfur dioxide.

Claims (1)

1. A method of processing tin-containing slag, including grinding slag, preparing a mixture containing a sulfidizer and coal, sublimation of volatile tin compounds, characterized in that calcium chloride is introduced into the mixture in an amount of 1.5 - 2.1 kg per 1 kg of tin in the slag, and sublimation is carried out by firing the mixture at 800 - 900 ^o C in a reducing atmosphere.