RU2301386C1 - Device for drying polydispersional materials - Google Patents

Abstract

FIELD: drying materials.

SUBSTANCE: device comprises vortex chamber provided with inlet branch pipe for supplying gas suspension, detachable lid, central pipe, and deflecting ring provided with shield made of a projection shaped into an oval. The inner side of the vortex chamber is provided with blades made so that their concave side faces toward the flow of gas suspension. The inlet branch pipe is made of the device for producing gas suspension that is composed of charging hopper for initial damp polydispersional material, branch pipe for supplying hot heat-transfer agent ,and acceleration section. The vortex chamber is provided with the settling cyclone. The central pipe is provided with the deflector and is used as an exhaust pipe for discharging exhaust heat-transfer agent.

EFFECT: improved quality of the dried product and enhanced efficiency of drying.

3 dwg

Description

The invention relates to a drying technique, in particular to devices for carrying out heat and mass transfer processes, namely, convective drying of polydisperse materials, and can be used in food, chemical, pharmaceutical and related industries.

Currently, the industry is widely using the technique of a suspended layer with swirling coolant flows as one of the most effective means of intensifying the drying process of dispersed materials.

However, the drying process of polydisperse materials can be complicated by clumping of particles, sticking of particles of the processed material on the walls of the dryer. Highly moist polydisperse materials are especially susceptible to this phenomenon. Aggregation of particles leads to uneven processing and, as a consequence, to a deterioration in the quality of the finished product. The lumps formed during the drying process can be disaggregated both by mechanical action (various agitators, oscillating devices, etc.) and by the creation of various active hydrodynamic regimes in drying devices.

The second method of disaggregation is more preferable, as it allows you to:

- simplify the design of drying devices;

- due to the special aerodynamic structure of cyclone and vortex flows, create favorable conditions for the processes of heat and mass transfer between the gas phase and the processed material;

- use a type of drying in which each particle of the polydisperse material would receive the necessary amount of energy for the phase transformation of the moisture contained in it without the formation of large compounds of particles.

Closest to the proposed technical essence and the achieved result is a vortex dryer containing a vortex chamber with an inlet for inputting the initial gas suspension, a removable cover, a pipe serving to close the dead zone of the vortex, a baffle ring having an oval screen protrusion made interchangeable for regulation holding power of the camera. A hole in the bottom of the chamber connects it to the cochlea and the outlet pipe. [Mushtaev V.I., Ulyanov V.M. Drying of dispersed materials. - M .: Chemistry, 1988, p. 301-302 and Fig. 7-30.]

The disadvantages of the known design are:

- insufficiently high quality of the dried material, since the drying does not take into account the disaggregation of clumping polydisperse materials;

- the occurrence of stagnant zones due to adhesion of wet material to the walls of the vortex chamber;

- low intensity of the drying process;

- the need for additional equipment to obtain the initial gas suspension;

- the need for further dust separation (separation) equipment.

An object of the invention is to improve the quality of the dried product, the intensification of heat and mass transfer processes, preventing clumping and eliminating stagnant zones of polydisperse material.

The problem is achieved in that in a device for drying polydisperse materials, containing a vortex chamber with an inlet port for introducing a gas suspension, a removable cover, a central pipe, a baffle ring having an oval screen protrusion made interchangeable to regulate the holding capacity of the chamber, the new is that on the inner surface of the vortex chamber placed blades, made in such a way that their concave surface is directed to meet the movement of the gas suspension, as an input pipe used zuyut device for producing a gas suspension, consisting of a hopper initial wet polydispersed material branch pipe for the hot coolant entering and upper portion, in addition, the vortex chamber is provided with the collecting cyclone, the central tube is provided with a reflector and serves as an exhaust pipe for withdrawal of spent coolant.

The technical result consists in improving the quality of the dried product, the intensification of heat and mass transfer processes, preventing clumping of the material, eliminating stagnant zones of the material by creating a highly active hydrodynamic mode of interaction of the coolant with particles of polydisperse material, at which the maximum speed is achieved and the maximum active contact surface of the phases is ensured.

The invention is illustrated by drawings, where figure 1 shows a General view of a device for drying polydisperse materials; figure 2 is a top view; figure 3 is a section aa.

A device for drying polydisperse materials consists of a vortex chamber 1, on the inner surface of which there are blades 2, made in such a way that their concave surface is directed towards the movement of the heat carrier, equipped with a device 3 for receiving a gas suspension, consisting of a feed hopper 4 of the initial wet polydisperse material, a pipe 5 for introducing a hot coolant and an accelerating section 6, a removable cover 7, a baffle ring 8 having an oval-shaped screen protrusion made interchangeable for adjustments the retention capacity of the chamber, precipitation cyclone 9, the central pipe 10 with a reflector 11.

The device operates as follows.

The initial wet polydisperse material through the feed hopper 4 enters the zone of the booster section 6. At the same time, hot coolant (air) is fed into it through the pipe 5. In the booster section 6, the distribution of particles of wet polydisperse material occurs in the flow of hot coolant with the formation of a gas suspension and pre-drying is carried out. In this zone, particles are also accelerated to a speed that ensures circulation of the material in the apparatus.

The maximum pressure is created in the vortex chamber, therefore, for the supply of material, it is necessary that the pressure in the vortex chamber is equal to the pressure in the lower part of the loading hopper in communication with the chamber. This is ensured by the tight connection of the hopper with the loading slit and the presence in the hopper during operation of a sufficient amount of material that will prevent the penetration of the gas stream from the chamber into the hopper.

From the device 3, the gas suspension is tangentially fed into the vortex chamber, where the drying process occurs intensively. The coolant flow together with the particles of the material performs a complex circulation movement along the circumference of the apparatus, while increasing its speed.

The tangential velocity of the particles causes the appearance of a centrifugal force, which rejects particles from the center of the vortex chamber to its walls, forming a suspension-twisted layer - a rotating ring. In this case, the drying process proceeds in an unsteady mode at high relative velocities of the particles of the material and the coolant, which means that it is characterized by high intensity, that is, the centrifugal force acting on the particles increases, and therefore, the friction force between the particles and the walls of the drying chamber 1 , which leads to the abrasion of large particles with continuous updating of their surface.

If for monodisperse systems the probability of individual particles staying in the chamber is the same, then for systems consisting of particles of different sizes and densities, light and small particles are more likely to leave the chamber than large and heavy ones. The average residence time in the chamber of particles of small sizes is less than large. This circumstance has a definite advantage, since the heating and drying of small particles occurs much faster than large ones.

Naturally, in some cases, the unevenness of the particles in the apparatus, caused by the difference in their size, can have negative consequences, when the actual residence time of the individual fractions does not correspond to the required processing time, the result may be insufficient drying of the individual particles. With the accumulation of insufficiently dried large particles and newly arrived wet particles, a supersaturation occurs, clumping occurs, as well as particles stick to the walls of the chamber and the so-called “blocking” of the rotating layer occurs, which leads to the entrainment of insufficiently dried particles.

Thanks to the closed blades located on the inner surface of the vortex chamber 1, both the gas suspension and large lumps of wet polydisperse material are twisted and hit the bent blades, the concave surface of which is directed to meet the movement of the gas suspension, and a rupture of the rotating layer occurs, local vortices are formed that intensify the drying process with the simultaneous disaggregation of large lumps of material due to local mixing and mutual impact of the discarded lumps on the protrusions of curved blades.

As the dried particles of the dried product due to the newly introduced material are constantly captured by the air stream and carried out through the central hole in the lower part of the vortex chamber 1 into the precipitation cyclone 9, where there is an intensive separation of the dried solid and exhaust gas phases of the stream. The dry product is discharged through an opening in the conical part of the precipitation cyclone 9, and the spent drying agent passes through a reflector 11, which separates suspended particles and is discharged into the atmosphere through the central pipe 10, which acts as an exhaust pipe and serves simultaneously to close the dead zone of the vortex in the chamber.

Thus, the proposed device for drying polydisperse materials has the following advantages:

- execution of the vortex chamber in such a way that the blades are placed on the inner surface, and their concave surface is directed towards the movement of the coolant, provides high-quality disaggregation of the lumps of polydisperse material and eliminates the formation of stagnant zones;

- the presence of a feeder, a nozzle for entering the coolant and the booster section allows you to get a gas suspension immediately before entering the vortex chamber, without requiring additional complex devices;

- since the dryer allows you to separate the gas suspension into dried solid and exhaust gas phases, it is a dry type dryer;

- the use of the proposed device can improve the quality of drying to ensure uniform drying of all classes of clumping polydisperse material;

- the proposed device for drying polydisperse materials is universal, that is, it can be used in all industries where drying of polydisperse materials is necessary.

Claims (1)

A device for drying polydisperse materials containing a vortex chamber with an inlet port for introducing a gas suspension, a removable cover, a central tube, a baffle ring having an oval screen protrusion made interchangeable to regulate the holding capacity of the chamber, characterized in that the blades are located on the inner surface of the vortex chamber made in such a way that their concave surface is directed towards the movement of the gas suspension, a device for producing a gas suspension is used as an inlet pipe, consisting of a feed hopper of the initial wet polydisperse material, a nozzle for introducing a hot coolant and an accelerating section, in addition, it is equipped with a precipitation cyclone, and the central pipe is equipped with a reflector and acts as an exhaust pipe for outputting the spent coolant.

Images