RU2191840C1 - Method of processing molybdenite concentrates and middlings - Google Patents

Abstract

FIELD: metallurgy industry, particularly, processing of molybdenite concentrates and middlings. SUBSTANCE: method includes oxidizing roasting at temperature of 550-600 C carried out in two stages: the first stage is performed with oxygen deficiency up to 85-95% desulfurization degree of cinder; the second stage is carried out up to full oxidation of sulfur and formation of metal oxides with oxygen value exceeding stoichiometric value by a factor of 1.5-2.0. Simultaneously volatile oxides of rare metals are driven off and absorbed. Method allows to increase recovery of rhenium and other rare metals into gas phase up to 93-95%; to increase withdrawal of rhenium and other rare metals up to 2.4-3.3 g/l into absorption solutions; to reduce sulfur content in cinder down to 0.5%. EFFECT: simplification in realization, higher e ecological efficiency of progress due to reduced concentration of sulfuric acid in solutions. 1 tbl, 1 ex

Description

 The invention relates to the field of non-ferrous metallurgy, in particular to the processing of molybdenum concentrates and intermediate products, and can be used in the metallurgical industry for the smelting of ferromolybdenum and the extraction of rhenium and other related metals.

A known method of processing molybdenite intermediate product, including oxidative calcination with simultaneous distillation of volatile oxides of rare metals and their subsequent capture by absorption, and oxidative calcination is carried out in a cyclone at a temperature of 1350-1600 ^o With a coefficient of excess oxygen of 1.2-1.5 relative to stoichiometry [see n. Germany 3843172, publ. July 5, 1990 MKI C 01 G 39/02].

 The disadvantages of this method are that in the specified temperature range, 50-90% of molybdenum trioxide passes into the gas phase, although the oxidation of sulfur dioxide to trioxide does not occur. In addition, this method is impractical for the processing of raw materials containing rhenium and other rare metals, due to dilution of small quantities of captured oxides of these metals with molybdenum trioxide, leading to their loss.

There is also known a method of processing molybdenum by-product, including oxidative firing with simultaneous distillation of rhenium-containing gases at a temperature of 550-590 ^o C. Firing is carried out in multi-hearth furnaces [see A.N. Zelikman "Molybdenum", Moscow: Metallurgy, 1970, p. 37-39].

The disadvantages of this method are
- limited extraction of rhenium (sublimation of rhenium during oxidative firing in multi-hearth furnaces no more than 70%);
- dust formation (up to 18%);
- technological difficulties (it is difficult to maintain the optimal firing temperature on each hearth).

 In addition, a known method of firing molybdenum-containing material in a rotary tube furnace with external heating [see "Fundamentals of Metallurgy", vol. 4 "Rare Metals", ed. N.S. Grever et al., Moscow: Metallurgy, 1967, p. 26].

 However, the known method does not provide a high degree of sublimation of rhenium (not more than 50%), while the content of total sulfur in the cinder is about 1%.

The closest in technical essence and the achieved result to the claimed invention is a method of processing molybdenum concentrates and intermediate products, including oxidative calcination at a temperature of 550-600 ^o With the simultaneous distillation of rare metal oxides and their subsequent capture by absorption. Firing is carried out with a coefficient of excess oxygen of 1.8-2.2 with respect to stoichiometry in a fluidized bed furnace. The concentration of sulfuric acid in absorption solutions 100 g / l, rhenium - 0.1-0.5 g / l [A.N. Zelikman, B. G. Korshunov "Metallurgy of rare metals", M.: Metallurgy, 1991, S. 46-47].

The disadvantages of the prototype method:
- high sulfur content in the cinder (sulfate sulfur up to 2%, sulfide - up to 0.5%), preventing its further use in the production of ferromolybdenum;
- significant pyleunos (up to 40%);
- loss of rhenium and other rare metals (more than 50%) due to inefficient interaction with absorption solutions of gas bubbles of rare metal oxides contaminated with gaseous SO ₂ , SO ₃ and solid dust;
- technological difficulties and the complexity of the hardware design process.

The objective of the present invention is to increase the efficiency of the method due to the technical result - increasing the degree of sublimation and absorption in absorption solutions of volatile oxides of rare metals, in particular rhenium oxide Re ₂ O ₇ , and reducing the sulfur content in the cinder.

The technical result is achieved by the fact that in the method of processing molybdenum concentrates and intermediate products, including oxidative calcination at a temperature of 550-600 ^o With simultaneous distillation of volatile oxides of rare metals and their subsequent capture by absorption, according to the invention, oxidative calcination is carried out in two stages, and the first stage carried out with a lack of oxygen to a degree of desulfurization of the cinder 85-95%, and the second lead to complete oxidation of sulfur and the formation of metal oxides with an excess of oxygen 1.5-2.0 times sheniyu to stoichiometry.

The inventive conditions for the implementation of the method are necessary and sufficient to increase its effectiveness due to the fact that:
- the lack of oxygen in the first stage of oxidative firing provides a high degree of desulfurization (85-95%) of the concentrate without the formation of volatile oxides of molybdenum (MoO ₃ ) and rare metals (Re ₂ O ₇ and others);
- the main amount of sulfur dioxide formed in the first stage is removed from the firing zone and subsequently excluded from the mass transfer process in the gas-liquid system upon the transition of gaseous rare metal oxides to absorption solutions, reducing the production of sulfuric acid in them;
- excess oxygen in the second stage of oxidative calcination contributes to the complete completion of the oxidation processes of the residual sulfur and the formation of volatile molybdenum trioxide (MoO ₃ ) and rare metal oxides (rhenium, osmium, etc.).

 Analysis of the known technical solutions allows us to conclude that the claimed invention is not known from the level of the studied technology, which indicates its compliance with the criterion of "novelty."

 The essence of the claimed invention for a specialist does not follow explicitly from the prior art, which allows us to conclude that it meets the criterion of "inventive step".

 The possibility of processing molybdenum concentrates and intermediate products in the claimed conditions at domestic metallurgical enterprises indicates that the invention meets the criterion of "industrial applicability".

 The inventive method of processing molybdenum concentrates and intermediate products has been tested in pilot industrial conditions of metallurgical enterprises of the Ural region and Uzbekistan (in particular, the Institute of Metallurgy of the UV RAS and the Almalyk mining and metallurgical plant).

 Example 1. The processing of molybdenum concentrates.

 For processing used granular (2-4 mm) molybdenum concentrate with a moisture content of about 5% with a content,%: Mo 32,000; S 26,000; Re 0.076.

Processing was carried out in a tubular rotary kiln with external electric heating with a capacity of 15 kg / h. Oxidative firing was carried out in two stages. In the first stage, the molybdenite concentrate was fired at a temperature of 550 ^o With a lack of oxygen to a degree of desulfurization of the cinder 85%. Gases were discharged. In the second stage, oxidative firing was carried out at a temperature of 550 ^o C and an excess of oxygen with respect to stoichiometry by 1.5 times. At the same time, at the second stage of firing, the volatile oxides of rare metals were distilled off, which were then captured by absorption in solutions circulating before the level of sulfuric acid reached 320 g / L in them. The concentration of rhenium in the absorption solutions was 2.4 g / L. The total sulfur content in the cinder is 0.5%.

 In the conditions of example 1 was carried out the processing of molybdenum concentrates in examples 2-3 with varying ratios within the claimed limits. In the processing of other molybdenum-containing materials, in particular intermediate products, results similar to those given in the present examples are obtained. In addition, the processing of molybdenum concentrates in the conditions of the prototype method [A.N. Zelikman, B.G. Korshunov "Metallurgy of rare metals", M.: Metallurgy, 1991, S. 46-47] - see example 4.

 The conditions of the method and the results of the analysis of the obtained products are shown in the table.

As can be seen from the above examples and table data, the use of the proposed method for processing molybdenum concentrates and intermediate products in comparison with the known method, taken as a prototype [A.N. Zelikman, B.G. Korshunov "Metallurgy of rare metals", M .: Metallurgy, 1991, p. 46-47], provides the following technical and socially useful advantages:
- increase the extraction of rhenium and other rare metals in the gas phase up to 93-95%;
- increase the extraction of rhenium and other rare metals up to 2.4 - 3.3 g / l in absorption solutions;
- reduction of sulfur content in the cinder up to 0.5%;
- ease of implementation of the method;
- environmental friendliness of the process by reducing the concentration of sulfuric acid in solutions.

Claims (1)

A method of processing molybdenum concentrates and intermediate products, including oxidative calcination at a temperature of 550-600 ^o With simultaneous distillation of volatile oxides of rare metals and their subsequent capture by absorption, characterized in that the oxidative calcination is carried out in two stages, and the first stage is carried out with a lack of oxygen to the degree of desulfurization of the cinder is 85-95%, and the second stage is carried out until the sulfur is completely oxidized and metal oxides are formed with an oxygen excess of 1.5-2.0 times with respect to stoichiometry.

Images