RU2384799C1 - Vacuum drier for thermo- and xerolabile loose and caking materials - Google Patents

Abstract

FIELD: heating, drying.

SUBSTANCE: invention refers to drying equipment of thermo- and xerolabile loose and caking materials and can be used in chemical, pharmaceutical, microbiological and other industries. Essence of invention consists in the fact that vacuum drier for thermo- and xerolabile loose and caking materials includes cone-shaped chamber with gas-distributing grid located in its lower part, crushing elements installed along the axis above gas-distributing grid, and pressure release and vacuum valves. In the lower part of the chamber of gas-distributing grid there attached is the outlet part of a converging-diverging nozzle. At pulse vacuum release in the drying chamber there provided is uniform supply (without separation from walls) of drying agent as to chamber cross-section, increase of flow rate and impingement force of pre-loosened material with crushing elements, heat-mass-exchange surface and drying process intensity.

EFFECT: improving the dried material quality and intensifying the drying process.

1 dwg

Description

The invention relates to a technique for drying thermo- and xerolabile bulk and clumping materials and can be used in chemical, microbiological and other industries.

A device for drying dispersed materials is known according to the copyright certificate No. 1211550, priority date is July 13, 1984, including a drying chamber with profile knives, a vacuum receiver and high-speed valves.

The disadvantage of this device is the inability to obtain a material of a uniform fine fraction throughout the volume of the material layer.

Known vacuum dryer for bulk and clumping materials, containing a drying chamber with a jacket and a gas distribution grid, coaxially mounted grinding elements made in the form of wire mesh with decreasing mesh size, receiver with a vacuum system, copyright certificate No. 1460562, priority date June 30, 1987 of the year.

The disadvantage of this device is the uneven flow of the gaseous drying agent. A separation of the boundary layer from the chamber walls is possible. This affects the quality of the dried material.

The invention is aimed at improving the quality of the dried material and the intensification of the drying process.

The result is achieved in that in a vacuum dryer for bulk and clumping materials containing a heated conical chamber with a gas distribution grill located in its lower part, grinding elements mounted axially above the gas distribution grill and pressure and vacuum relief valves according to the invention in order to increase the speed tossing a layer of material and increasing the intensification of the drying process in the lower part of the chamber, a Laval nozzle is connected to the gas distribution grid by the outlet part.

The drawing shows a dryer, a General view.

The vacuum dryer contains a conical-shaped drying chamber 1 with a jacket 2 for heating, a gas distribution grid 3. Grinding elements 4 are arranged coaxially along the axis of the drying chamber 1, made in the form of wire mesh (type A) with a mesh size decreasing from the bottom to the top and fixed on the axis 5. The drying chamber 1 through the filter 6 located in its upper part and the system of valves and nozzles 7-10 are connected respectively to the atmosphere, the vacuum receiver 11 and the vacuum system, and to the gas distribution to the lower part of the drying chamber 1 eshetke output portion 3 connected soplo12 Laval. The vacuum dryer is equipped with a gas supply system of a preheated drying agent (CA) in a heater (not shown), a quick-acting valve 14, an air supply valve 13 for abrupt depressurization of the drying chamber 1. The raw wet material is loaded through the pipe 15, and the dry material is discharged through the lid with a gas distribution grid 3 connected to the outlet of the Laval nozzle 12.

A vacuum dryer for thermo- and xerolabile bulk and clumping materials works as follows.

The coolant is supplied to the jacket 2 of the drying chamber 1, and the source wet material is charged through the pipe 15. After that, the nozzle 15 is sealed and through the valve 14 (with the valves 8, 9, 13 closed) and the gas distribution grid 3 into the drying chamber 1, a preheated drying agent is fed through the Laval nozzle, which brings the material to be dried into suspension. The supply of CA through the Laval nozzle 12 allows you to evenly distribute the CA stream when it approaches the gas distribution grid and thereby prevent this stream from separating from the walls of chamber 1. The spent agent, passing through the layer of the dried material, filter 6 and valve 7, is released into the atmosphere. At the same time, through the valve 10, the vacuum receiver 11 is evacuated to a predetermined residual pressure, after which the valve 10 is closed. After the convective heating of the dried material to a predetermined temperature, the valves 14 and 7 close and open the valve 8 and produce a pulse pressure relief in the drying chamber 1 through the vacuum receiver 11. As a result of the combined expansion of air and moisture vapor contained inside the agglomerated particles of the dried material, the agglomerates are loosened, increasing its porosity and size. Then, valves 8 and 10 are closed, valve 9 is opened, and drying takes place in drying chamber 1 by decreasing the pressure to a certain vacuum, and moisture is intensively evaporated due to the heat accumulated by the material to be dried, while it is cooled due to pressure reduction, despite the additional supply of heat from heated jacket drying chamber 1.

Thus, the periods of heating of the dried material alternate with cooling during the periods of evacuation, i.e. a vacuum-oscillating drying regime is realized. At the end of the evacuation step, valve 9 is closed and the high-speed valve 13 is opened. The air stream entering through the Laval nozzle 12 piston-shaped throws up the loosened dried material, which, passing through a series of sequentially installed grids 4, is crushed to a size smaller than the smallest grating. Then, the high-speed valve 13 is closed, the valves 7, 10 and 14 are opened again, and the cycle is repeated in the described sequence.

Periodically, as the hydraulic resistance of the filter 6 increases, the filter cloth is cleaned by the reverse vacuum method, for which, after the evacuation stage, the drying chamber is depressurized through valve 7.

To effectively destroy the lumps of material, the depressurization of the drying chamber 1 should be carried out by high-speed valves 13, 14, the opening time of which does not exceed 0.5 s.

At the end of the drying process, the dried material is discharged through a cover with a gas distribution grill 3.

It was experimentally established that to ensure effective grinding of lumps of dried material, the cell size ratio in each subsequent grate, in the direction of gas movement (from bottom to top), should be a multiple of 1.5-2 relative to the previous one, and the number of gratings and its cell sizes should be determined from the necessary condition obtaining the required dispersed composition of the dried material.

Claims (1)

A vacuum dryer for thermo- and xerolabile bulk and clumping materials, containing a heated conical chamber with a gas distribution grill located in its lower part, grinding elements mounted axially above the gas distribution grill, and pressure and vacuum relief valves, characterized in that in the lower part of the chamber to the gas distribution grill the outlet part is connected to a Laval nozzle.