RU2512726C2 - Method of purifying zirconium tetrafluoride from admixtures - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to metallurgy. Method of purification of zirconium tetrafluoride from admixtures includes sublimation of zirconium tetrafluoride in mixture with 8-30 wt % of metal zirconium and desublimation of formed vapour. Crushed waste products in form of shavings, chips, filings and skull can be used as metal zirconium.

EFFECT: efficient purification of zirconium tetrafluoride from admixtures is ensured.

2 cl, 6 dwg, 1 tbl

Description

The invention relates to chemical technology for the production of zirconium tetrafluoride, purified from impurities (aluminum, nickel, oxygen, chromium, iron, silicon), and can be used in ore processing plants and in the nuclear industry.

A known method of purification of zirconium from impurities from a nitric acid solution by extraction of zirconium with tributyl phosphate in an inert diluent in the aqueous phase [K. Bolshakov et al. Technology of rare and trace elements. M .: Higher school, 1969. t.2, p.475].

This method, as well as other versions of the extraction method, is characterized by the high cost of extractants and the fire hazard of production, the need to use many mechanical and pneumatic devices. In addition, the purification of zirconium from impurities by the extraction method is poorly combined with the processes of opening zircon and obtaining pure metal by reduction from its tetrafluoride.

As the closest analogue of the claimed method is a method of purification of zirconium tetrafluoride from impurities [Ozherelyev OA, Purification of zirconium tetrafluoride from impurities of 3-d transition metals by sublimation. Abstract of dissertation for the degree of candidate of technical sciences, Kemerovo, Kemerovo State University, 1992, 22 pp., See pp. 4-6, 9-10, 18]. The disadvantage of this method is the low coefficient of purification (separation), as a result of which several stages of purification are necessary to reduce the content of impurities in zirconium tetrafluoride, even at the optimum temperature and pressure of the process.

The objective of the invention is to increase the efficiency of purification of zirconium tetrafluoride (TFC) from impurities by cleaning in one step and improve the heat supply to the original product without upgrading existing equipment.

This object is achieved in that the method of purification of zirconium tetrafluoride from impurities involves sublimation of the initial zirconium tetrafluoride and desublimation of the vapors formed, and sublimation is subjected to zirconium tetrafluoride in the form of a mixture with 8-30 wt.% Metallic zirconium, and crushed waste is used as metallic zirconium in the form of shavings, scraps, skull, sawdust.

It is proposed to increase the efficiency of the method for cleaning TFC from impurities to add an inert material with high thermal conductivity and contributing to a more intense heat transfer to the volume of the layer in the initial TFC powder, subjected to sublimation. As such an inert material, it is advisable to use shavings or other ground waste (skull, scraps, etc.) after receiving or processing metal zirconium. Such zirconium wastes will, firstly, introduce a minimum amount of impurities into the TFZ, since their composition is close to the conditional metal, and secondly, metal zirconium intensively absorbs many gaseous products, for example, hydrogen fluoride and water vapor, which to slow down the process of corrosion of the material of the sublimator and auxiliary equipment (for example, vacuum pumps). Thirdly, metal zirconium, having a high chemical activity, reduces the volatility of some impurities, reducing the valence of impurity metals.

This assumption has been verified experimentally.

A mixture (charge) of zirconium tetrafluoride with metal zirconium shavings was placed in the casing of one apparatus under conditions (pressure and temperature) ensuring the sublimation process. Chip particles had an average size of 0.5 × 4.0 × 40 mm. The resulting TFC pairs were desublimated on the cooled surface of the condenser. Desublimate was weighed and the amount of impurities was determined. The experimental results are shown in the table.

The dependence of the degree of sublimation on the content of chips in the mixture Series No. Experience number The initial mass of TFC, g The mass of chips in the mixture, g initial chip content in the mixture,% The duration of sublimation, min The mass of desublimate, g The degree of sublimation,% one one 300 0 0 90 123.12 41.04 2 300 13.81 4.40 90 138.26 46.09 3 300 20.00 6.25 90 156.20 52.07 four 300 25.00 7.69 90 161.60 53.87 5 300 30.00 9.09 90 193.20 64.40 6 300 35.00 10.40 90 194.00 64.67 7 300 45.00 13.04 90 187.06 62.35 8 300 60.00 16.67 90 177.66 59.22 9 300 90.00 23.08 90 161.60 53.87 10 300 150.00 33.33 90 149.75 49.92 2 one 200 0 0 thirty 44.10 22.05 2 195 5 2,50 thirty 45.30 23,23 3 190 10 5.00 thirty 51.18 26.94 four 185 fifteen 7.50 thirty 67.70 36.59 5 180 twenty 7.50 thirty 68.61 38.12 6 170 thirty 15.0 thirty 59.82 35.19 7 160 40 20,0 thirty 59.00 36.88 8 140 60 30,0 thirty 55.50 39.64

From the data given in the table, it follows that a significant increase in the desublimate yield in both series occurs only up to the value of the initial chip content in the charge of 8-10%. A further increase in the amount of chips, the degree and, accordingly, the speed of sublimation does not increase or even decreases.

Next, the behavior of impurities during sublimation of TFC in the presence of zirconium chips was investigated. It is known that metallic zirconium at elevated temperatures has significant chemical activity with respect to many substances. As an example, we can give some equations of processes

7Zr + 6H ₂ O = 3ZrO ₂ + 4ZrH ₃ (at T <800 ° C);

Zr + 2H ₂ O = ZrO ₂ + 2H ₂ (at T> 800 ° C);

Zr + O ₂ = ZrO ₂ ;

Zr + 4HF = ZrF ₄ + 2H ₂ ;

Zr + N ₂ = 2ZrN;

2Zr + NO ₂ = ZrN + ZrO ₂ ;

2Zr + CO ₂ = ZrC + ZrO ₂ ;

5Zr + SiF ₄ = Zr ₄ Si + ZrF ₄ .

It follows from the equations that such impurities as oxygen, carbon, nitrogen, and silicon can transform into chemically strong compounds that are not sublimated under conditions of sublimation of TFC.

For experimental confirmation of these assumptions, averaged samples were taken from the desublimate of the second series of experiments for analysis on the content of basic impurities. The results of the analysis are shown in figures 1-6.

From the data shown in figures 1-6, it follows that with an increase in the content of chips in the initial charge, the concentration of all these impurities in desublimate decreases. A sharp decrease in the concentration of impurities (for example, oxygen, aluminum, nickel) occurs to a chip content of 8-12%, then with an increase in the content of chips in the charge to 30%, the concentration of impurities in desublimate decreases less intensively.

The experiments showed that when using a mixture of zirconium tetrafluoride with a zirconium metal shavings content up to 30%, the amount of impurities in the TFC desublimate decreases:

aluminum - 7 times,

Nickel - more than 3.5 times,

oxygen - 1.9 times,

chromium - 1.8 times,

iron - 2.5 times,

silicon - more than 2.2 times.

At the same time, zirconium chips during the sublimation of zirconium tetrafluoride practically do not lose their original properties and can be used repeatedly.

The method was successfully tested in an industrial environment on an existing apparatus with a one-time loading of a mixture of TFC with zirconium shavings up to 500 kg. At the same time, the amount of impurities in desublimate decreased in accordance with the results of the experiment, and the productivity of the apparatus increased by 24.5%.

Thus, the proposed method of purification of zirconium from impurities (aluminum, nickel, oxygen, chromium, iron, silicon) allows you to effectively carry out the cleaning process in one step. At the same time, the speed of desublimation is increased, and the process itself can be carried out in existing devices without any modernization.

Claims (2)

1. The method of purification of zirconium tetrafluoride from impurities, including sublimation of the original zirconium tetrafluoride and desublimation of the vapor formed, characterized in that the zirconium tetrafluoride is mixed in a mixture with metal zirconium in an amount of 8-30 wt.%. 2. The method according to claim 1, characterized in that crushed waste in the form of shavings, scraps, a skull, sawdust is used as metal zirconium.

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