RU2469114C1 - Tin-containing material processing method - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: method involves melting of oxide raw material containing less than 20 wt % of tin and distillation of tin in sulphide shape from oxide molten metal at using elementary sulphur; besides, the process is performed in neutral or weakly oxidising atmosphere with supply of CaO-containing flux and at bubbling of molten slag in electric furnace of alternating or direct current or in melting furnace of reflection type, or in bubbling-type unit in the form of Vanyukov furnace, or inclined rotary TBRC converter, or the furnace of Ausmelt or Isasmelt type, or horizontal or vertical converter by supplying carrier gas containing elementary sulphur; flux is taken in quantity of 1-30% of weight of tin-containing material, as carrier gas there used is nitrogen or air, or mixture of air and hydrocarbon fuel, or argon; supply of elementary sulphur to carrier gas is performed in liquid or solid dust-like or steam-like form.

EFFECT: improving the process efficiency; reduction of power consumption at tin distillation stage and reduction of tin losses with dump slag.

5 cl, 2 ex, 2 tbl

Description

The invention relates to the field of metallurgy of non-ferrous metals, in particular to pyrometallurgical extraction of tin from oxide concentrates or secondary raw materials, and can be used for sublimation of tin in sulfide form.

A known method of extracting tin from tin concentrates using reducing smelting with coal in an electric or shaft furnace. Melting is carried out at a temperature above 1400 ° C to ensure the tin content in dump slag is below 1% of the mass. The slag acidity is maintained at the level of 1-1.25, the reducing agent consumption is up to 120% of the calculated value for the reduction of all oxidized tin of the charge to metal tin and iron oxides of the charge to iron oxide (AS USSR No. 127420).

This method is used for processing rich tin concentrates containing over 40% tin, and cannot be used for processing poor raw materials. In addition, the disadvantages of the method are the duration and energy intensity of the process, as well as the high iron content in the resulting metal alloy.

Also known is a method of chemical and metallurgical enrichment of substandard tin-polymetallic raw materials, based on the sublimation of metal oxides and sulfides from melts (fuming). For example, at the Alpen Funk mining and metallurgical enterprise in Germany, poor tin concentrates and tin-containing products from metallurgical dumps are mixed with a sulfidizing agent (pyrrhotite), granulated, dried, subjected to melting at 1200-1400 ° C and fumigation (blowing the melt with air to sublimation of volatile oxides and sulfides of non-ferrous metals). Dusty sublimates containing tin, lead, arsenic and others are captured in a capacitor system, granulated, dried, calcined to remove arsenic, and then used as tin concentrate to produce tin by known methods. When the tin content in the raw material is up to 7% of the mass. get a concentrate containing up to 60% tin when it is extracted into a concentrate of 96% (Patent SU No. 1776065, С22В 25/02).

The disadvantages of the method, in addition to low productivity, include the periodicity of the process and, consequently, a significant change in the composition of the exhaust gases over time, which negatively affects the performance and efficiency of the system for capturing sublimates and cleaning the exhaust gases.

Closest to the proposed invention in technical and technological essence is a method of processing tin-containing materials in a fuming furnace, including combined melting and purging of the melt when loading solid materials into the furnace during the first 40-90% of the processing cycle time with the ratio of the loaded solid charge to the residual weight the melt within 1: 30-1: 60 in 1 min and the supply of the fuel-air mixture depending on the sulfur content in the melt with an air flow coefficient of 0.9-1.7 (AS USSR No. 469351 )

The method adopted for the closest analogue (prototype).

The method has the following disadvantages.

The need to involve significant volumes of pyrite as a sulfidizing agent in the processing of oxidized tin-containing concentrates or intermediates characterized by a low sulfur content causes a low productivity of the process.

The creation of a reducing atmosphere in a bubbler unit (burning a significant amount of fuel under conditions that are not optimal from the point of view of heat generation), as well as the need to use a solid reducing agent (coke, coal, etc.) in an amount of up to 250 kg per ton of processed concentrate lead to a high energy intensity of the process.

The achievement of the residual tin content in the slag at the level of 0.3-0.5% of the mass. it is limited primarily by technological rather than economic reasons (when a lower residual tin content is obtained, fuel and sulfidizer consumption sharply increase, as well as the duration of the fuming (sublimation) period). The specified disadvantage of the method is the cause of high losses of tin with waste slag

The objective of the invention is to increase productivity, reduce the energy intensity of the fuming process, aimed at the processing of poor tin-containing raw materials with low sulfur content, as well as reducing losses of tin with waste slag process.

The technical result of the claimed invention is to increase the productivity of the process, reducing energy costs in the redistribution of sublimation of tin and reducing losses of tin with dump slag.

The technical result is achieved by the fact that in the method of processing tin-containing materials, including the melting of oxide concentrates or secondary raw materials containing less than 20% of the mass. tin, and the sublimation of tin in sulfide form from an oxide melt, according to the claimed method, the process is conducted in a neutral or slightly oxidizing atmosphere with the CaO-containing flux supplied and the slag melt bubbled by supplying a carrier gas containing elemental sulfur.

The amount of flux supplied is 1-30% by weight of tin-containing material.

As a gas containing elemental sulfur, it is possible to use a carrier gas, nitrogen, or air, or a mixture of air and hydrocarbon fuel, or argon.

It is possible to supply elemental sulfur to the carrier gas in liquid or solid (dusty) or vaporous form.

The process can be carried out in an AC or DC electric furnace, or in a reflective type melting furnace, or in a bubble-type unit: Vanyukov’s furnace, or TBRC inclined rotary converter, or Ausmelt or Isasmelt type furnace, or horizontal or vertical converter.

The essence of the claimed method is as follows.

The sublimation process is carried out in a melting unit providing a melt temperature above 1200 ° C (for example, in an electric furnace). With increasing melt temperature, the intensity of sublimation of tin sulfide increases.

Elemental sulfur is fed into the oxide melt (tin sulfidation) by means of a lance immersed in the melt with a graphite or water-cooled metal tip.

Sulfidation of tin oxide melt proceeds with the release of SO ₂ formed during the reduction of oxidized tin. In parallel with the processes of tin sulfidation, iron sulfidation processes with the formation of matte are possible, as well as sulfidation processes of some impurity components (copper, lead), which are found in tin concentrates. It should be noted that sulfidation of an appreciable amount of iron with the formation of matte based on the Fe-S system is observed when the tin content in the oxide melt decreases below 0.3-0.5 wt%. The tin content in the resulting sulfide melt is below 0.05-0.10% by mass.

Tin-containing sublimates are captured by known methods (electrostatic precipitators, bag filters, etc.), after which they are sent for processing using known technologies.

The SO ₂ -containing process exhaust gas after dust cleaning is directed to the production of sulfuric acid and (or) neutralization.

A slightly oxidizing or neutral atmosphere of the process, provided with a minimum consumption or refusal to supply a reducing agent, provides a minimum level of sulfidation of iron and its transition into molten matte. The CaO-containing flux additive to the melt provides fusibility and low viscosity of the melt even with a high content of higher iron oxides in it. The low viscosity of the slag melt contributes to the intensification of the process of sublimation of sulfated tin. The use of SiO ₂ -containing fluxes is undesirable, since an increase in the content of silicon dioxide promotes an increase in the viscosity of slag, as well as a decrease in the thermodynamic activity of tin in the slag melt due to the formation of tin silicates. A decrease in the thermodynamic activity of tin in slag adversely affects the intensity and depth of sublimation of sulfidized tin from slag melt.

The combination of the claimed methods and parameters of the process of sulphidation and sublimation of tin from oxide melts makes it possible to extract tin even from poor tin concentrates and intermediates containing less than 5-10% of the mass. tin at the level of 80-85% rel. The tin content in the dump slag is about 0.2-0.3% of the mass.

Justification of the parameters

The process of sublimation of tin sulfides from the melt at a temperature above 1200 ° C ensures the completeness of sulfidation of all oxide forms of tin melt, high speed of the process and, therefore, its productivity. Lowering the temperature below 1200 ° C leads to an increase in the viscosity and possible heterogenization of the oxide melt, which negatively affects the intensity and depth of sublimation of tin. With increasing temperature, the melt viscosity and the required amount of flux decrease, the intensity and depth of sublimation of tin increase.

The process is implemented in an AC or DC electric furnace, a reflective type melting furnace, or in a bubble-type unit (Vanyukov’s furnace, TBRC inclined rotary converter, Ausmelt, horizontal converter, etc.), however, the most preferred units are melting units that allow immersion from above into the melt vertical or inclined lance feeding elemental sulfur. The use of side blast is less preferable due to the high aggressiveness of the sulfur-containing gas to the caissons, as well as the inconvenience of servicing horizontal tuyeres.

The amount of elemental sulfur supplied to the melt is 1.5-2.0 kilograms per 1 kilogram of tin melt, of which:

- up to 20% of the supplied sulfur is not absorbed by the melt and leaves the bath in an elementary form;

- up to 20% of the supplied sulfur is spent on the removal of oxygen from the melt, in the form of SO ₂ associated with tin;

- up to 40% of the supplied sulfur is spent on removal of oxygen from the melt in the form of SO ₂ bound to iron;

- up to 20% of the supplied sulfur is spent on sulfidation of iron and the formation of matte;

- up to 20% of the supplied sulfur is spent on tin sulfidation;

- up to 5% of the supplied sulfur goes into the slag melt.

The flow rate of the carrier gas required to supply 1 ton of elemental sulfur to the melt does not exceed 150-200 nm ³ . It should be noted that the flow rate of the carrier gas of elemental sulfur is due to the particularities of the installation for supplying elemental sulfur to the melt and can be close to zero when vaporous sulfur is supplied to the melt, the temperature of which is higher than the boiling point of sulfur.

The method is illustrated by examples.

The proposed method for the sublimation of tin in sulfide form from oxide melts was tested under laboratory and pilot tests.

Example 1. Laboratory tests aimed at removing tin from a calcium silicate melt by supplying elemental sulfur in a gaseous form to it through a special device, were carried out with a 100 gram sample of the concentrate at a temperature of 1450 ° C. The experiments performed simulated the high-temperature sublimation of tin from slag during its sulfidation in an industrial furnace.

The initial tin-containing concentrate fed to the smelting contained (% wt.): Sn - 8.5; Fe - 36.6; Cu - 0.7; Pb - 2.5; S is 0.4; SiO ₂ - 10.1; Al ₂ O ₃ - 7; MnO - 2.6; CaO - 0.6; TiO ₂ - 1.7.

A different amount of calcium oxide was introduced into the charge from 10 to 30%, which corresponds to a CaO / SiO ₂ ratio _of from 1 to 3. Elemental sulfur was introduced uniformly during the experiment with a total amount of 5 to 20% (by weight of the concentrate). The molten sulfur was fed into the melt with a special device with a feed rate of 0.055-0.222 grams per minute. The reducing agent was not supplied, since its supply would entail the destruction of magnetite, intensive reduction and subsequent sulfidation of oxidized iron with the formation of matte.

The duration of each experiment in this series is 90 minutes.

The experimental data for this series of experiments are shown in table 1.

As can be seen from the above data, in 90 minutes it is possible to bring the residual tin content in the slag to values less than 0.3% of the mass. and get the extraction of tin in sublimates over 96.0%.

An increase in the supply of lime leads to a change in the output of slag from 101 to 123% by weight of the concentrate. However, the change in the slag yield is of a different nature than in the case of supplying pyrite as a sulfidizing agent, namely, the slag yield is somewhat reduced when more sulfur is fed into the melt. This is due to an increase in the yield of matte (with the same amount of CaO). As follows from the above results, tin recovery of more than 95% can be achieved by feeding 20-30% lime and 10-20% sulfur in a gaseous form to the charge.

The consumption of elemental sulfur was specified during pilot tests, since the assimilation of gas sulfur by the melt to a large extent depends on the design features of the melting (sublimation) unit and the mechanism for supplying sulfur to the melt.

Example 2. Pilot tests were implemented on a pilot installation, including an electric furnace with a capacity of 50 kV · A, a volume of 50 kg for slag melt and a plant for melting, sublimation and feeding into the melt in vaporous form of elemental sulfur. The temperature in the furnace during testing was controlled by an optical pyrometer and regulated by changing the electrical parameters (voltage supplied to the electrodes, current in the electrode circuit). The temperature of vaporous sulfur supplied to the melt in a stream of nitrogen was 400 ° C. The flow rate of the carrier gas of elemental sulfur (nitrogen) was 0.1-1.0 nm ³ / h. The amount of sulfur supplied to the melt was 1.2-6.0 kg / h.

The initial tin-containing concentrate fed to the smelting contained (% wt.): Sn - 8.5; Fe - 36.6; Cu - 0.7; Pb - 2.5; S is 0.4; SiO ₂ - 10.1; Al ₂ O ₃ - 7; MnO - 2.6; CaO - 0.6; TiO ₂ - 1.7.

Table 2 shows a comparison of the indicators achieved by sublimation of tin from an oxide melt by the fuming process (the method adopted for the prototype) and when using the proposed method.

As can be seen, as a result of the proposed method for the sublimation of tin from oxide melts during its sulfidation with elemental sulfur, tin recovery in sublimates of 95% was achieved with a residual tin content in the oxide melt of 0.2% by weight. and the content of tin in the sublimates at the level of 50% of the mass. The initial oxide melt subjected to sublimation according to the proposed method, was characterized by 1.3-2 times lower tin content than the oxide melt processed by the prototype method.

The proposed method provides high productivity due to the deep and intense sublimation of tin from slag melt, the process is characterized by low energy consumption and provides a low residual tin content in dump slag, which entails a reduction in capital and operating costs when implementing the proposed method compared to existing methods.

Thus, the claimed invention allows to realize the sublimation of tin in sulfide form from oxide melts, including those obtained during the melting of low-grade tin-containing concentrates, or secondary raw materials (slag, clinker, dross, etc.). The tin sublimates obtained during smelting are processed using known technologies.

Table 1 Indicators of experiments on sulfidation of calcium silicate slag by elemental sulfur No. CaO supply,% of set Sulfur supply,% of set The content of Sn in the slag during the experiment (min),% mass. matte yield,% slag yield,% tin recovery,% 0 ' thirty' 60 ' 90 ' one 10 5 7.21 4.20 2.54 1.68 0.95 101.98 78.3 2 10 10 7.28 2.83 1.33 0.79 1.80 101.76 89.9 3 10 fifteen 7.18 1.92 0.62 0.34 2,55 101.31 95.7 four 10 twenty 7.32 1.00 0.23 0.12 3.20 100.85 98.6 5 twenty 5 6.66 3.43 1.65 1.13 0.63 112.98 84.0 6 twenty 10 6.45 2.18 0.80 0.44 1.20 112.37 93.8 7 twenty fifteen 6.50 1.42 0.44 0.18 1.70 111.98 97.5 8 twenty twenty 6.71 0.73 0.13 0.06 2.13 111.56 99.1 9 thirty 5 6.15 3.00 1.32 0.72 0.32 123.10 88.9 10 thirty 10 6.14 2.15 0.69 0.21 0.60 122.46 96.8 eleven thirty fifteen 6.08 1.49 0.39 0.05 0.85 122.34 99.3 12 thirty twenty 6.22 0.68 0.11 0.02 1,07 122.13 99.7

table 2 Comparison of technological parameters of the fuming furnace and sulfidization in a pilot DC furnace Parameter Units measuring Fuming The proposed method one The content of tin in the initial oxide melt subjected to fuming % of the mass. 8-15 6.0-6.5 2 Residual tin content in slag % of the mass. 0.3-0.5 0.1-0.3 3 Extraction of tin into sublimates % 92-96 95-98 four The content of tin in sublimates % of the mass. 50-60 50-60 5 Sulfur content in dump slag % of the mass. 0.1-0.3 1.5-3.0 6 The content of SO ₂ in the exhaust gas % vol. 0.5-1.5 5-20 7 The amount of sulfur discharged with exhaust gases kg / t tin 500-600 800-1500 8 Specific slag yield at the end of the fuming process t / t 1.15-1.35 0.85-1.05 9 Matte specific yield kg / t 30-50 80-200 10 Specific lime consumption kg / t 200-250 200-250 eleven Specific pyrite consumption kg / t 150-250 - 12 Specific Coke Consumption kg / t 150-200 - 13 Specific fuel oil consumption kg / t 150-200 - fourteen Specific sulfur consumption of elemental kg / t - 200-250 fifteen Specific volume of exhaust gases m ³ / t 1500-2200 400-800 16 Specific consumption of technological electricity for melting the charge kWh / t - 850-900 17 Specific consumption of technological electricity for melting and evaporation of elemental sulfur kWh / t - 25-30 eighteen Specific nitrogen consumption for sulfur transportation m ³ / t - 100-200

Claims (5)

1. A method of processing tin-containing materials, including the melting of oxide concentrates or secondary raw materials containing less than 20 wt.% Tin, and sublimation of tin in sulfide form from an oxide melt, characterized in that the process is conducted in a neutral or slightly oxidizing atmosphere with a CaO-containing flux and while sparging the slag melt by supplying a carrier gas containing elemental sulfur. 2. The method according to claim 1, characterized in that the flux is taken in an amount of 1-30% by weight of tin-containing material. 3. The method according to claim 1 or 2, characterized in that the carrier gas used is nitrogen, or air, or a mixture of air and hydrocarbon fuel, or argon. 4. The method according to claim 3, characterized in that the supply of elemental sulfur to the carrier gas is carried out in a liquid, or solid dusty, or vaporous form. 5. The method according to claim 4, characterized in that the process is carried out in an electric furnace of alternating or direct current, or in a reflective type melting furnace, or in a bubble-type unit in the form of a Vanyukov furnace, or an inclined rotary TBRC converter, or an Ausmelt or Isasmelt furnace , or horizontal or vertical converter.