RU2372571C2 - Device for product drying - Google Patents

Abstract

FIELD: heating.

SUBSTANCE: invention can be applied for one-step drying after wet grinding in production of nuclear fuel for nuclear power stations and other similar products. Installation for product drying, which has heating chamber with passing through it conveyor with perforated belt, is connected with system of extraction ventilation, contains additionally vacuum-pump and tunnel chamber, installed before heating chamber, in tunnel chamber there is slot attachment which is located under upper branch of conveyor with perforated belt and connected with suction branch pipe of vacuum-pump.

EFFECT: quick drying of porous products which have low strength with very low residual content of moisture after drying.

1 dwg

Description

The invention relates to equipment for drying small porous products in bulk, having low strength, with a very low residual moisture content after drying, and can be used, for example, for single-stage drying after wet grinding in the manufacture of nuclear fuel for nuclear power plants and other similar products.

There is a method of removing moisture from the surface of metal products by treating with an aqueous solution of a surfactant followed by spraying the surface with water (copyright certificate SU 1506245 A1; F26B 5/16, B01D 12/00, 1989). As a surfactant, water-soluble ionic substances with a water-displacing ability are used. During the processing of products, the molecules of the surfactant located in the immediate vicinity of the metal surface chemically interact with it, forming insoluble metal salts. In a subsequent water jet, the molecules of a surfactant that are not chemically bonded to the metal surface are carried away by the water jet. A monomolecular layer of a substance remains on the metal surface, which hydrophobizes it.

Known drying installation for small products in bulk (copyright certificate SU 1513354 A1; F26B 15/10, 1989), consisting of a drying chamber with heaters and a recirculation ventilation system. A two-tier conveyor passes through the drying chamber. Trays are pivotally attached to the upper and lower conveyors. Products intended for drying are poured onto a baking sheet of the upper conveyor, which moves them into the drying chamber. Having passed the upper conveyor, the products are reloaded onto a baking sheet of the lower conveyor, then, having passed the lower conveyor, they are unloaded into the container. In the drying chamber, the set temperature is maintained using the control system. Moisture vapor from the drying chamber is removed by ventilation.

The disadvantage of this installation is the impossibility of quick drying of porous products having low strength, since when overloading fragile products from the upper conveyor to the lower, some of them will be damaged.

The installation for heat treatment of products (copyright certificate SU 1478007 A1; F26B 9/06, 3/30, 1989), consisting of a conveyor passing through a multi-zone camera with infrared emitters, an electric automation unit, loading and unloading mechanisms, was selected as a prototype. The conveyor belt is made of several rows of steel cables connected by prefabricated terminal clamps. Under the working branch of the conveyor there is a gas distributor with a perforated surface, and longitudinal pipelines with ejectors are installed above it.

From the electric automation unit, the heating of the chamber is switched on, and after the set temperature has been set in it, the conveyor drive starts. The loading mechanism feeds the products intended for drying to the conveyor belt. Cooled gaseous nitrogen is supplied through the perforation of the gas distributor, passes through a conveyor with heated products and, when heated, is removed by ejectors.

The disadvantages of the prototype are its great complexity and the high cost of the reagents - chilled nitrogen, and to achieve a low residual moisture content after drying, prolonged drying is required.

The objective of the invention is the implementation of rapid drying of porous products having low strength with a very low residual moisture content after drying.

The essence of the invention lies in the fact that, in contrast to the known device, including a heating chamber with a conveyor passing through it with a perforated tape, the installation of drying products is connected to an exhaust ventilation system. The product drying installation additionally contains a vacuum pump and a tunnel chamber installed in front of the heating chamber, and in the tunnel chamber there is a slit nozzle located under the upper branch of the conveyor with a perforated tape and connected to the suction pipe of the vacuum pump.

This task is achieved by the fact that immediately after washing, when the moisture has not yet had time to penetrate deep inside the pores, the products enter the tunnel chamber, in which the crevice nozzle connected to the suction port of the vacuum pump creates a vacuum around the products. The vacuum, in turn, creates a high-speed flow of air, which removes moisture drops (most) from the surface. In addition, the vacuum created outside the product prevents the penetration of moisture through the pores inward (an excessive pressure is created inside, which displaces the moisture out). The part of the moisture remaining on the outer surface of the products (a small part) is heated, turning into steam, and removed by the exhaust ventilation system.

The drying installation consists of a heating chamber 1 (see drawing) with heaters 2, a conveyor with a perforated belt 3, a washing device 4, a tunnel chamber 5 and a control cabinet 8. In the tunnel chamber there is a slot nozzle 6, which is located under the upper branch of the conveyor with a perforated tape and connected to the suction pipe of the vacuum pump 7. Conveyor belt with perforated tape provides free air passage. The upper part of the heating chamber is connected to an exhaust ventilation system 9.

The drying process is as follows. Products after wet grinding fall on the conveyor with a perforated tape, on which they move during the entire process. Then they fall into the washing device, where contaminants resulting from grinding are removed from the surface with water jets under pressure. Used water is collected in the drain pan. Drops of water remaining on the product, under the influence of gravity, are mainly collected in its lower part. Further, the products fall into the tunnel chamber. The crevice nozzle connected to the suction port of the vacuum pump forms a high-speed air flow in the tunnel chamber, which from the bottom through the upper branch of the conveyor with a perforated tape sucks the water droplets collected in the lower part of the product. Due to rarefaction, moisture does not penetrate through the pores. Further, the products fall into the heating chamber, to which the exhaust ventilation system is connected, forming a small vacuum. Hot air, rising up, passes through the upper branch of the conveyor with a perforated tape on which the products are located, heats them and removes the evaporated moisture through the exhaust ventilation system. Leaving the heating chamber, the products are unloaded into a technological container (not shown). The installation of drying products is controlled automatically using the control cabinet.

The use of the claimed installation of drying products allows you to:

- to carry out in the stream quick drying of porous products having low strength, with a very low residual moisture content after drying,

- increase the yield of finished products due to the fact that products of low strength during the drying process are not subjected to collisions and remain intact,

- to increase the drying efficiency, eliminating the costs associated with the drying of products,

- improve environmental conditions in the workplace through the use of some vacuum.

Claims (1)

An apparatus for drying products having a heating chamber with a conveyor passing through it with a perforated belt, characterized in that it is connected to an exhaust ventilation system, further comprises a vacuum pump and a tunnel chamber installed in front of the heating chamber, and in the tunnel chamber there is a slot nozzle located underneath the upper branch of the conveyor with a perforated tape and connected to the suction pipe of the vacuum pump.

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