RU2465208C2 - Apparatus for hydrolysis of uranium hexafluoride - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to apparatus for carrying out low-temperature batchwise hydrolysis of solid uranium hexafluoride in aqueous hydrogen fluoride solution and can be used in processing depleted (waste) uranium hexafluoride to powdered uranium dioxodifluoride and anhydrous hydrogen fluoride. The apparatus has a housing with a cone-shaped bottom and an discharge pipe, as well as a jacket, a cover with pipes for feeding starting reagents and outlet of reaction products and an anchor mixer. The anchor mixer is fitted with additional blades directed upwards, and the end of the shaft of the mixer is fitted with a scrapper which lies in the discharge pipe, fitted with a shut-off and discharge device. The shut-off and discharge device has a housing with a cooling jacket and a plunger with a hole whose size is comparable to that of the hole in the discharge pipe.

EFFECT: invention provides efficient mixing of the reaction mass, easy discharge of the product and enables to obtain uranium dioxodifluoride powder with very high specific surface area.

4 cl, 2 dwg

Description

The invention relates to devices for low-temperature portion hydrolysis of solid uranium hexafluoride in an aqueous solution of hydrogen fluoride and can be used in the processing of depleted (dump) uranium hexafluoride to powdered uranium dioxodifluoride and anhydrous hydrogen fluoride.

To carry out the low-temperature hydrolysis of UF _{6, a} vessel with a mixing device is used (UK patent No. 1075233, IPC C01G 43/06, published July 12, 1967 "Improvement Relating to the Production of Uranium and Fluoride").

In the above patent, gaseous UF _{6 is used} , the thermal energy is spent on its evaporation, and the separation of the HF solution from salt and the drying of UO ₂ F _{2 are} carried out in several reactors, which is associated with the transfer of the chemically aggressive reaction mass from the apparatus to other reactors and separation of the pulp by known methods on the precipitate and solution.

Known reactor of the rotating type for the low-temperature hydrolysis of solid uranium hexafluoride in an aqueous solution of hydrogen fluoride to obtain a powder of UO ₂ F ₂ and almost anhydrous hydrogen fluoride (RF patent No. 2311346, publ. 27.11.2007). Stirring of the reaction mass is provided by metal rods. Then, evaporation of liquid hydrogen fluoride and drying of the obtained salt UO ₂ F ₂ · nH ₂ O are carried out in the same reactor.

The use of a rotating reactor in which the chemistry of the stages of hydrolysis of solid UF ₆ was studied is technically difficult in large tonnage because of the need to repeatedly move the reactor, which has a large mass, from vertical to horizontal and rotate it on movable rolls.

The closest in technical essence to the implementation of UF ₆ hydrolysis can be selected mass-transfer apparatus with a mixing device, containing a body with a conical bottom and discharge pipe, as well as a shirt, a cover with pipes for supplying the starting reagents and the delivery of reaction products and an anchor mixer (Processes and chemical apparatuses technologies: transport phenomena, macrokinetics, similarity, modeling, design: 5 vol. T. 2. Mechanical and hydromechanical processes / D.A. Baranov, A.N. Blinichev, A.V. Vyazmin, etc. Edited by AMKutepov . - M .: Logos, 2002, 458-467 p., - prototype).

The use of a known apparatus for carrying out hydrolysis of UF _{6 is} complicated by the insufficient mixing efficiency and the difficulty of unloading the obtained uranium dioxodifluoride.

The technical problem solved by the invention is to eliminate the above disadvantages.

The solution to this problem is achieved by the fact that in the apparatus for the hydrolysis of uranium hexafluoride containing a body with a conical bottom and discharge pipe, as well as a shirt, a cover with pipes for supplying the starting reagents and the delivery of reaction products and an anchor mixer, the anchor mixer is equipped with at least one a pair of upward-facing additional blades, and the end face of the mixer shaft is equipped with a scraper placed in the discharge pipe, equipped with a locking and unloading device containing a housing with a cooling jacket and a plunger with a hole Commensurate with the discharge pipe hole.

The apparatus is additionally equipped with a cultivator made in the form of a U-shaped plate mounted movably on the annular protrusion of the mixer shaft in response to the gaps between the upward-facing blades of the anchor mixer. The scraper is made in the form of a plate with side slots directed at an angle upward, shifted vertically relative to each other.

In addition, the pipe for supplying uranium hexafluoride is equipped with a siphon with a coaxially located expander.

Figure 1 schematically shows a longitudinal section of the apparatus. In Fig.2 is a cross section aa of the locking and unloading device in Fig.1.

The apparatus for hydrolysis of uranium hexafluoride contains a housing 1 with a conical bottom 2 and a discharge pipe 3 and a shirt 4. On the cover 5 of the device, a pipe 6 for supplying liquid HF and a pipe 7 for supplying solid UF _{6 are} provided. The pipe 7 for supplying solid UF ₆ is equipped with a siphon 8 with a coaxially arranged expander 9. On the cover 5 of the apparatus, a pipe 10 is also provided for discharging gaseous HF. An anchor mixer 11 is installed in the apparatus body 1, having two pairs of additional blades 12 and a shaft 15. The ripper 13 is made in the form of a U-shaped plate mounted movably on the annular protrusion 14 of the shaft 15 in response to the gaps between the blades of the anchor mixer. The end face of the shaft 15 is equipped with a scraper 16 located in the discharge pipe 3. The scraper 16 is made in the form of a plate with side slots directed at an angle upward, shifted vertically relative to each other. A locking and unloading device 17 is installed on the discharge pipe 3. The locking and unloading device 17 comprises a housing 18 with a cooling jacket 19 and a plunger 20 with an opening that is comparable with the opening of the discharge pipe 3. The plunger 20 of the locking and unloading device 17 is moved using a two-position pusher 21. The sealing of the gaps between the plunger 20 and the cylindrical part of the housing 18 of the locking and unloading device 17 in the closed position is carried out by means of a thin lubricating layer of fluorinated liquid, for example Emer RLE applied to the plunger, which by passing coolant through the cooling jacket 19, locking the handling device thickens at minus 6 ÷ 8 ° C until substantially solid state, providing complete sealing.

The device operates as follows.

Before starting the operation of the apparatus, the discharge pipe is sealed, for which the plunger 20 of the shut-off and discharge device 17 is lubricated with a thin layer of UPI fluorinated liquid and moved with the pusher 21 to the “closed” position, in which the cylindrical surface of the plunger overlaps the opening of the discharge pipe 3, then through the cavity of the cooling jacket 19 of the shut-off and discharge device 17 pass liquid nitrogen vapors, maintaining the solid lubricant.

After that, a working solution of hydrogen fluoride is poured into the reactor. Through the pipe 7 with the mixer 11 turned on, the calculated amount of solid UF ₆ is fed into the apparatus. Prevention of sticking UF ₆ and provide using a siphon 8 with an expander 9, partially immersed in a solution of hydrogen fluoride to prevent the entrainment of vapor UF ₆ when it is loaded.

Effective mixing intensifies the process of hydrolysis of solid UF ₆ , which proceeds at room temperature without consuming thermal energy while simultaneously evaporating practically anhydrous HF, which is removed through condensation pipe 10.

The pressure in the apparatus is maintained at 5.0 ÷ 15.0 mm water column. below atmospheric. Pressure control is carried out by a differential pressure gauge (not shown).

Due to the very low solubility of UO ₂ F ₂ in a solution of anhydrous hydrogen fluoride and evaporation of the liquid phase, almost all uranium remains in the apparatus in the form of a precipitate, which is dried, for this purpose, a coolant, such as a BM-vacuum oil, is pumped through a cavity of the cooling jacket 4 (not shown) 4, gradually increasing its temperature to 150 ° C. A smooth increase in temperature in the jacket 4 and continuous mixing prevent the formation of agglomerates, while the product located in the discharge pipe 3 not only loosens due to the scraper 16, but also exchanges with the bulk of the product located in the apparatus.

Unloading of the dry product from the apparatus is carried out using the shut-off and discharge device 17. For this, the flow of refrigerant to the cooling jacket 19 is stopped, providing a phase transition of the lubricant to the liquid state, then the plunger 20 is moved with the pusher 21 to the open position. Then, with the stirrer operating, dry UO ₂ F ₂ powder is dispensed into a receiving container (not shown).

Analysis of the obtained powder UO ₂ F ₂ showed a U content of 77.5%, an F content of 12%.

According to the results of the analysis, the condensed HF contained 100 ± 1.0% HF with a U content of 6 mg / dm ³ .

Using the proposed apparatus allows to obtain a powder of uranium dioxide with a very high specific surface area equal to 8.6 m ² / g, which is essential for its further processing.

Claims (4)

1. Apparatus for hydrolysis of uranium hexafluoride, comprising a body with a conical bottom and discharge pipe, as well as a shirt, a cover with pipes for supplying the starting reagents and dispensing reaction products, and an anchor mixer, characterized in that the anchor mixer is equipped with at least one pair of directional upward of the additional blades, and the end face of the mixer shaft is equipped with a scraper placed in the discharge pipe, equipped with a locking and unloading device containing a body with a cooling jacket and a plunger with a hole commensurate with the hole discharge tube. 2. The apparatus according to claim 1, characterized in that it is additionally equipped with a cultivator made in the form of a U-shaped plate mounted movably on the annular protrusion of the mixer shaft in response to the gaps between the upward-facing blades of the anchor mixer. 3. The apparatus according to claim 1, characterized in that the scraper is made in the form of a plate with side slots directed at an angle upward, shifted vertically relative to each other. 4. The apparatus according to claim 1, characterized in that the pipe for supplying uranium hexafluoride is equipped with a siphon with a coaxially located expander.

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