CS197109B1 - Circuitry of apparatus for continuously drying gelatinous materials by vapours of organic substances - Google Patents

Description

The invention relates to an apparatus for the continuous drying of granular, gel and granular materials with a vapor of organic substances.

The known continuous tunnel or vertical movable bed dryers have some disadvantages: a complex and lengthy duty cycle, the need to maintain a precise regime, heating, temperature stability, cooling. In these types of dryers, during the drying process, the particles β become sintered and deformed. When drying gel materials, it is necessary to adjust the composition of the drying atmosphere, water humidification, saturation of the atmosphere by thermal decomposition products.

A large number of aerosols are generated in fluld driers and in vibro-fluid drying devices, the disposal of which is a serious problem in radiochemical plants, in the preparation of plutonium-containing nuclear fuels.

The azeotropic drying apparatus known hitherto works intermittently. The particles of the materials to be treated are vigorously stirred with bubbles of vapor of the organic liquid during drying and can be tumbled together. Dust and precipitated non-volatile fractions accumulate in the cooking flask. There is a danger of secret boiling. There is a risk of splashing and contamination of the environment in radiochemical operations.

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The dried particles are heat treated in the next step. In most known technological processes, the thermal exposure is interrupted after drying and the particles are transported to another apparatus where they are reheated to the required temperature. This, of course, complicates the process diagram, extends the duty cycle and increases handling requirements.

The aforementioned drawbacks are eliminated by employing an apparatus for the continuous drying of the granular, gel and granular materials with the organic liquid vapor according to the invention, characterized in that the drying vessel with the conveyor, the gel particles and the organic liquid vapor is connected to the steam generator and piping into the condenser. The mixture of vapors of organic liquid and volatiles is discharged to a condenser connected to the exhaust and connected to a separator with an aqueous phase outlet and connected to the vapor generator. The gel particles are entrained in the organic liquid vapor environment by the transporter to the outlet for the dried particles, wherein the particle feed rate is selected such that the entrained particles remain in the drying vessel until undesirable volatiles are removed therefrom.

The vapor of the organic substance gradually increases the temperature of the transferred particles, forming a thin layer of condensate on their surface. As soon as the temperature of the condensate layer reaches the boiling point of the azeotropic mixture, the volatile vapor mixture also leaves the surface of the particles together with the organic vapors.

Compared to continuous moving bed dryers, the drying time is considerably shorter. For gel particles of 2.5 mm diameter, about 25 minutes are sufficient. During drying, there is no mechanical damage to the particles, disproportionately less aerosols are generated.

The device is characterized by extremely good efficiency, is compact and easy to operate remotely. For these reasons, it is particularly advantageous for drying toxic and radioactive substances, and for drying spherical gel particles which are a semi-product for the production of dispersive fuels for fast or high temperature gas cooled reactors.

The accompanying drawing shows an exemplary circuit diagram of a continuous dryer of granular, gel and granular materials.

The drying vessel 1 with the conveyor 2 is supplied by the inlet 3 of the wet material and the inlet 4 of the steam of the organic liquid. Mixture of organic liquid vapors together with volatile vapors

I leaves the space of the drying vessel 1 through the first conduit 5 to the condenser 6 connected to the exhaust 7. The condensate of the vapor mixtures flows into the separator 8 where the phase separation occurs. The aqueous phase containing the unwanted volatiles is taken through the aperture 9 as waste and the organic liquid phase is returned via the second line 10 to the vapor generator 11, from where it is led in the form of steam through the third line 12 to the inlet 4. and led to regeneration, where it is devoid of non-volatile substances and returned to the plant together with the wet material through inlet 3.

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The dried material is conveyed by a conveyor 2, by which a rotating perforated partition or moving belt, can be carried through the space of the drying vessel to the dried particle outlet 14 from where it falls into the furnace 15 where the desired temperature rise zones are gradually formed along the axis. constant temperature and cooling zone. The dried and thermally treated material exits the furnace 15 through the aperture 16. This arrangement has the great advantage that residues of organic liquid and non-removed volatiles and thermal decomposition products are discharged from the furnace 15 through the air stream, inert gas or gas mixture through the aperture. drying vessels. chlorinated or fluorinated hydrocarbons can be used as non-flammable substances in the first line 5 and through the condenser 6 to the outlet 7 □ as organic liquids, thus meeting the strict safety requirements for working with highly toxic materials - plutonium and transuranic elements.

By recycling the organic liquid through the 11 vapor generator and regenerator, the consumption of this liquid is minimized.

The device is simple and can easily be placed in a glove box.

By shortening the drying time and avoiding the transport of the dried material for further heat treatment, ee will greatly speed up the processing process and reduce the risk of radiation. The operation of the device can be easily automated and remotely controlled. By solving the problem of drying medium recycling, its regeneration and connection of the whole equipment to common exhaust, its consumption is reduced and the possibility of aerosols leakage to the surroundings is prevented.

Example

The spherical particles of uranyl gel 2.5 mm, 1 mm in diameter with trichlorethylene were fed through inlet 3 to a drying vessel J with a rotating perforated baffle which carried them to fixedly positioned rakes directing the particle path into a spiral shape towards the opening 14. through the third conduit 12 through the aperture 4, the trichlorethylene vapors generated in the vapor generator 11 are supplied. The speed of rotation of the baffle was selected so that the particles remained in the space of the drying vessel for 25 minutes. During this time, 64.5 wt. % water and 2.0 wt. % of ammonia in the form of vapors, which were entrained by the trichlorethylene vapors and discharged through a first line 5 to a condenser 6 connected to a discharge 7. The condensate accumulated in a separator 8 where the aqueous and organic phases were separated. The aqueous phase was discharged as liquid waste through the opening 9 and the organic phase was returned via the second line 10 to the vapor generator 11.

The dried particles were discharged through orifice 14 and placed in a tube furnace where they were stripped of trichlorethylene residues and non-volatile volatiles at > 87 ° C and heated further in an air stream up to 450 ° C and reduced under argon / 10% hydrogen. and baked at 1450 ° C to dense uranium dioxide beads with a density of 98 98% of the theoretical value.

Claims (1)

Connection of a device for the continuous drying of gel materials with a vapor of organic liquids, characterized in that the drying vessel (1) with the conveyor (2), the gel material inlet (3) and the organic liquid vapor inlet (4) is connected (11) and the first line (5) is connected to a condenser (6) connected to the exhaust (7) and connected to a separator (8) with a water phase outlet (9) and a line (10) connected to the steam generator (11) the discharge opening (13) of which is adapted to discharge a portion of the organic liquid for regeneration, the drying vessel (1) being connected to the furnace (15) provided with the opening (17) for the supply of air, a gas or gas mixture and an orifice (16) for discharging the heat treated particles.