RU2484020C1 - Method of producing uranium tetrafluoride - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to methods of producing uranium tetrafluoride and specifically to methods of producing uranium tetrafluoride during hydrofluorination of uranium dioxide, and can be used in production of uranium hexafluoride or uranium metal. The method of producing uranium tetrafluoride involves countercurrent reaction of a solid phase in form of uranium dioxide with hydrogen fluoride which is in gas phase when the solid phase moves through a low-temperature and a high-temperature region when anhydrous hydrogen fluoride is fed into the high-temperature region into the uranium tetrafluoride output zone. Hydrofluoric acid, having hydrogen fluoride concentration of not less than 35 wt %, which is converted to gaseous state, is fed into the low-temperature region together with the gas phase coming out of the high-temperature region. Overall flow rate of hydrofluoric acid in terms of anhydrous hydrogen fluoride fed into the low-temperature region and anhydrous hydrogen fluoride fed into the high-temperature region is maintained equal to the stoichiometric flow rate of hydrogen fluoride in the hydrofluorination reaction of uranium dioxide to uranium tetrafluoride.

EFFECT: invention provides a cheap process of producing uranium tetrafluoride.

3 cl, 2 tbl

Description

The invention relates to methods for producing uranium tetrafluoride, and in particular to methods for producing uranium tetrafluoride in the process of hydrofluorination of uranium dioxide, and can be used in the production of uranium hexafluoride or metallic uranium.

It is known (C. Harrington, A. Ruele. Uranium production technology. Gosatomizdat, M. 1961, p. 224) obtaining uranium tetrafluoride by the interaction of uranium dioxide with gaseous hydrogen fluoride by the reaction:

The source of information (VB Shevchenko, BN Sudarikov. Uranium technology. Gosatomizdat. M., 1961, pp. 264-266) describes a method for hydrofluorination of uranium dioxide in auger apparatuses - a prototype. The temperature of the reaction space at the solid inlet is maintained at a level of 290-340 ° C, at the outlet 540-590 ° C. Anhydrous hydrogen fluoride is supplied to fluorination in the discharge zone of uranium tetrafluoride and moves countercurrent to the solid phase; as the gas phase moves to the loading zone of uranium dioxide, it is enriched with water vapor. Waste gases containing water vapor are sent for condensation. The excess of anhydrous hydrogen fluoride in the process exceeds 200%. The content of uranium tetrafluoride in the obtained product (in terms of uranium), i.e. the yield of uranium tetrafluoride is 95-96%. The disadvantage of this method is a large excess of expensive anhydrous hydrogen fluoride.

The objective of the invention is to expand the arsenal of methods for producing uranium tetrafluoride, reducing the consumption of anhydrous hydrogen fluoride.

An additional task is to obtain uranium tetrafluoride with a yield of at least 96%, because tetrafluoride of precisely this quality is usually used to produce uranium hexafluoride by fluorination of tetrafluoride with elemental fluorine.

The problem is solved by the fact that in the method for producing uranium tetrafluoride by hydrofluorination of uranium dioxide, which includes countercurrent interaction of the solid phase with hydrogen fluoride in the gas phase, the solid phase moves through the low-temperature and high-temperature regions when anhydrous fluoride uranium tetrafluoride is fed to the high-temperature region in the discharge zone hydrogen, in the low-temperature region, together with the gas phase exiting the high-temperature region, is fed converted to gaseous oyanie (gasified) hydrofluoric acid having a concentration of hydrogen fluoride of at least 35 wt.% while maintaining the total consumption of HF in high and low temperature areas, is equal to the stoichiometric flow rate in HF hydrofluorination reactions uranium dioxide to uranium tetrafluoride.

Within the total stoichiometric HF consumption, the mass ratio of gasified hydrofluoric acid supplied to the low-temperature region, calculated as HF and anhydrous hydrogen fluoride supplied to the high-temperature region, is maintained equal to (0.2-1.1): 1.

The temperature of interaction is increased along the movement of the solid phase in the low-temperature region from 150 to 350 ° C, and in the high-temperature region - from 350 to 415 ° C.

The method is as follows.

Hydrofluorination of uranium dioxide was carried out in two series-connected screw reactors. The reactors are electrically heated. A solid phase in the form of uranium dioxide enters the first reactor (low temperature region) and a gaseous phase containing a gasified hydrofluoric acid combined with the gases leaving the second reactor (high temperature region); the second phase receives the solid phase from the first reactor containing uranium oxides, oxyfluorides and tetrafluoride, and anhydrous hydrogen fluoride countercurrent to it is supplied to the product discharge zone - uranium tetrafluoride.

Gasified hydrofluoric acid is obtained by heating to the boiling point and complete evaporation of HF and H ₂ O.

In experiments 1-6, hydrofluoric acid containing 40% HF was used, and in experiment 7, 35% HF was used. The stoichiometric flow rate of 100% HF is 0.296 kg per 1 kg of UO ₂ . Within the framework of an almost stoichiometric (0.29 kg) flow rate of HF, the ratio of HF supplied for the process in the form of anhydrous hydrogen fluoride and in the form of hydrofluoric acid was changed.

The conditions of the experiments are shown in table 1, and the results of the experiments are in table 2.

Table 1 No. op. Consumption, kg, per 1 kg UO ₂ , in terms of HF The ratio of the costs of anhydrous hydrogen fluoride and hydrofluoric acid in terms of HF, kg / kg Temperature in reactors, ° С anhydrous hydrogen fluoride hydrofluoric acid the amount first reactor second reactor entrance exit entrance exit one 0.24 0.05 0.29 1: 0.2 173 352 353 407 2 0.21 0.08 0.29 1: 0.4 163 348 349 410 3 0.16 0.13 0.29 1: 0.8 158 351 353 408 four 0.14 0.15 0.29 1: 1,1 153 350 353 409 5 0.12 0.17 0.29 1: 1.4 151 353 355 411 6 0.10 0.19 0.29 1: 2.0 142 349 352 417 7 0.17 0.12 0.29 1: 0.7 157 354 356 412

table 2 No. op. The composition of the target product,% in terms of U Losses of HF, wt.% Uf ₄ UO ₂ F ₂ UO ₂ one 98.00 1.10 0.90 0.30 2 97.40 1.30 1.30 0.41 3 96.50 2.10 1.40 0.89 four 96.05 2.40 1.55 1.20 5 95.30 2.90 1.80 1.40 6 93.80 3.90 2,30 2.40 7 96.20 2,30 1,50 0.92

From the data of tables 1 and 2 it can be seen that during the hydrofluorination process, part of the gaseous anhydrous hydrogen fluoride can be replaced by gasified hydrofluoric acid, subject to the total stoichiometric flow rate of HF. The yield of uranium tetrafluoride at least 96% is achieved in experiments 1-4 and 7, with the ratio (within the stoichiometry according to HF) of anhydrous hydrogen fluoride and hydrofluoric acid in terms of HF 1: (0.2-1.1), at HF concentrations in hydrofluoric acid 35 and 40 wt.%. As it turned out, additional water (water contained in hydrofluoric acid, additional to the water that is formed by the hydrofluorination reaction) with the claimed ratios of hydrofluoric acid and anhydrous hydrogen fluoride does not prevent the product from being obtained in a yield of at least 96% (table 2). At the same time, replacing expensive anhydrous hydrogen fluoride with cheaper hydrofluoric acid helps to reduce the cost of the process. When replacing a larger amount of anhydrous hydrogen fluoride with hydrofluoric acid (tests 5 and 6), the yield of the obtained uranium tetrafluoride becomes less than 96% (the content of UO ₂ F ₂ and UO ₂ in the product increases).

Thus, substituting up to 52% by weight of anhydrous hydrogen fluoride with hydrofluoric acid (i.e. when using up to 52% by weight of HF as hydrofluoric acid), conditional uranium tetrafluoride is obtained during the hydrofluorination of uranium dioxide.

Claims (3)

1. A method of producing uranium tetrafluoride by hydrofluorination of uranium dioxide, comprising countercurrent interaction of the solid phase with hydrogen fluoride in the gas phase, when the solid phase moves through the low-temperature and high-temperature regions when anhydrous hydrogen fluoride is supplied to the high-temperature region to the discharge zone of uranium tetrafluoride, characterized in that in the low-temperature region, together with the gas phase exiting the high-temperature region, fed into the gaseous state of the fins acid with a hydrogen fluoride concentration of at least 35 wt.%, while maintaining the total flow rate of hydrofluoric acid in terms of anhydrous hydrogen fluoride supplied to the low temperature region and anhydrous hydrogen fluoride fed to the high temperature region, equal to the stoichiometric flow rate of hydrogen fluoride in the reaction hydrofluorination of uranium dioxide to uranium tetrafluoride. 2. The method according to claim 1, characterized in that in the framework of the total flow equal to the stoichiometric, the mass ratio of the gaseous hydrofluoric acid supplied to the low-temperature region, in terms of HF, and anhydrous hydrogen fluoride supplied to the high-temperature region, is maintained equal to (0.2-1.1): 1. 3. The method according to claim 1, characterized in that the interaction temperature is increased along the movement of the solid phase in the low temperature region from 150 to 350 ° C, and in the high temperature region from 350 to 415 ° C.