RU2158778C1 - Method of processing of molybdenum intermediate product - Google Patents

Abstract

FIELD: processing of molybdenum intermediate product. SUBSTANCE: method includes granulation of intermediate product with addition of binding agent in form of sodium silicate and additional introduction of quartz sand with weight ratio of SiO₂:Mo=(0.9-2.5):1. Subsequent oxidizing roasting is carried out at temperature of 600-650 C with simultaneous driving off of volatile metal oxides and further cooling of products of roasting to temperature of 450-550 C. Method allows reduction of total sulfur in cinder down to 0.2%, higher degree of sublimation of rhenium up to its complete recovery (98.3 %0, excluded dust carrying away, obtaining cinder with easily soluble molybdenum, simplified method technology and apparatuses. EFFECT: higher efficiency. 1 tbl, 3 ex

Description

 The invention relates to non-ferrous metallurgy, in particular to the processing of molybdenum by-products, and can be used in the chemical industry to obtain molybdenum trioxide, calcium molybdate and other compounds and in the metallurgical industry for smelting ferromolybdenum and extracting rhenium.

A known 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. [cm. A.N. Zelikman "Molybdenum", publishing house "Metallurgy", M., 1970, pp. 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).

 There is also known a method of firing molybdenum-containing material in a rotary tube furnace with external heating. [cm. "Fundamentals of Metallurgy", v.4, "Rare Metals", ed. N.S. Grever et al., Publishing House "Metallurgy", M., 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 by-product, including granulation with the addition of a binder and oxidative roasting with simultaneous distillation of volatile metal oxides (rhenium-containing gases). Moreover, bentonite is used as a binder, and oxidative firing is carried out in a fluidized bed furnace at a temperature of 575-580 ^o C.

 [cm. A. N. Zelikman "Molybdenum", publishing house "Metallurgy", M., 1970, p. 43 - 45].

The disadvantages of the method of the prototype:
- high content of total sulfur in the cinder (more than 2%),
- incomplete degree of sublimation of rhenium (92-94%),
- large pyleunos (up to 40%).

The objective of the present invention is to increase the efficiency of the method by increasing the degree of sublimation of volatile metal oxides, in particular rhenium oxide Re ₂ O ₇ , and reducing the sulfur content in the cinder.

The problem is solved in that in the method of processing molybdenum by-product, including granulation with the addition of a binder and oxidative calcination with simultaneous distillation of volatile metal oxides, according to the invention during granulation, sodium silicate is used as a binder and quartz sand is additionally introduced in the ratio, wt.%:
SiO ₂ : Mo = (0.9 - 2.5): 1,
and oxidative firing is carried out at a temperature of 600 - 650 ^o C followed by cooling of the products of firing to a temperature of 450 - 550 ^o C.

The additional introduction of quartz sand into the molybdenum intermediate using a binder - sodium silicate during granulation provides the formation of porous granules, the structure of which allows oxygen to quickly penetrate during firing, promoting the oxidation of molybdenum, rhenium and other metal sulfides without side reactions with the formation of lower oxides (such as MoO ₂ , ReO ₂ , ReO ₃ , etc.), worsening the quality of the cinder. In this case, sulfur oxide diffuses freely through the pores and is distilled off together with volatile metal oxides.

 The claimed amount of quartz sand is necessary and sufficient to obtain porous granules that are easily oxidizable and not subject to destruction during the firing process.

The introduction of refractory and inert material (quartz sand) into the molybdenum intermediate product allows oxidative firing at a temperature of 600 - 650 ^o C, at which the oxidation of sulfides with the formation of higher oxides is accelerated and Re ₂ O _{7 is} distilled off as much as possible.

To exclude losses of molybdenum (in the form of a sublimation of MoO ₃ ), the firing products are cooled to a temperature of 450 - 550 ^o C, providing the possibility of condensation of the vapor of molybdenum oxide on the granules of the cinder.

 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 industrial product in the claimed conditions using available materials at domestic metallurgical enterprises indicates the compliance of the invention with the criterion of "industrial applicability".

 The inventive method of processing molybdenum industrial product has been tested in laboratory and pilot conditions of enterprises of the Ural region (in particular, the Institute of Metallurgy of the UV RAS).

 Example 1. The implementation of the processing of molybdenum intermediate.

A preliminary mixing of molybdenum by-product in an amount of 40 g, quartz sand in an amount of 20 g (which was the ratio, wt.%: SiO ₂ : Mo = 0.9: 1) and sodium silicate - liquid glass with silicon module 2 in an amount of 1, was carried out. 8 g (3 wt.% Of the weight of the mixture).

 The resulting mixture was placed in a drum granulator and granulation was carried out in a known manner.

The finished granules were dried at a temperature of 150 ^o C to constant weight.

 As a result, granules with a size of 3-5 mm were obtained.

The granular industrial product was continuously fed into the high-temperature zone of an external heated laboratory rotary tube furnace, where oxidative firing was carried out at a temperature of 600 ^° C. for 1.5 hours. In this case, the cinder and gases containing volatile metal oxides (including Re ₂ O ₇ ) were transferred to the low-temperature zone of the furnace, where they were cooled to a temperature of 450 ^o C.

 The resulting gases were distilled off for subsequent capture, and the resulting sulfur oxides were neutralized in milk of lime. The cinder was discharged from the furnace and analyzed for rhenium and sulfur by conventional methods.

Under conditions similar to example 1, the decomposition of the molybdenum intermediate was carried out in examples 2-3 with varying ratios of SiO ₂ : Mo, oxidative calcination temperature and cooling temperature within the claimed limits.

 To obtain comparative data was also carried out the processing of molybdenum intermediate in the conditions of the prototype method.

 [cm. A. N. Zelikman "Molybdenum", publishing house "Metallurgy", M., 1970, p. 43 - 45].

 The conditions for the implementation of the claimed and known methods and the results of the analysis of the cinders are shown in the table.

As can be seen from the above examples and table data, the use of the proposed method for the processing of molybdenum intermediate provides in comparison with the method taken as a prototype [see A.N. Zelikman "Molybdenum", publishing house "Metallurgy", M., 1970, p. 43 - 45], the following technical and socially useful advantages:
- reduction of total sulfur content in the cinder (up to 0.20%);
- increase the degree of sublimation of rhenium to its almost complete extraction (98.3%);
- the exception of pyleunosa;
- obtaining cinder containing molybdenum in readily soluble form, convenient for hydrometallurgical or pyrometallurgical processing;
- simplification of technology by eliminating the need for dust collection and processing;
- simplification of the hardware design of the method.

Claims (1)

A method of processing molybdenum by-product, including granulation with the addition of a binder and oxidative roasting with simultaneous distillation of volatile metal oxides, characterized in that during granulation, sodium silicate is used as a binder and quartz sand is additionally introduced at a ratio, wt.%: SiO ₂ : Mo = ( 0.9 - 2.5): 1, and oxidative calcination is carried out at 600 - 650 ^o C, followed by cooling of the products of calcination to 450 - 550 ^o C.

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