RU2425311C1 - Vortex drying chamber for drying disperse material in swir flow of heat carrier with shf power supply - Google Patents

Abstract

FIELD: machine building.

SUBSTANCE: vortex drying chamber for drying disperse material in swirl flow of heat carrier with SHF-power supply consists of cylinder case with inlet branch for introduction of gas suspension and outlet branch for withdrawal of dried material equipped with SHF-emitter. The distinguished feature of the invention is fluoro-plastic coating of internal surface of the case of the vortex drying chamber to reduce attrition of dried material; also, the branch for introduction of gas suspension is converging at input to the drying chamber. Inside the vortex drying chamber on its side surface there are installed local accelerators of heat carrier flow and guiding insertions made of radio transparent material. Notably, the local accelerators of heat carrier flow are secured on side surface inside the vortex drying chamber so, as to form a stable rotating circular layer of being dried particles of material and to avoid their accumulation in a zone of maximal resistance to particles motion. The guiding insertions separating dried particles from the main rotating circular layer and guiding them into the central zone of the vortex drying chamber are arranged in a zone of particles return to an elevation point. The SHF emitter is arranged tangentially on external cylinder surface of the case of the vortex drying chamber to facilitate the highest density of flow of electromagnetic energy concentrating in a zone of a rotating circular layer of being dried particles of material.

EFFECT: upgraded quality of dried material, intensified process of heat and mass exchange due to raised activity of hydro-dynamic conditions in drying chamber resulted from increased inter-phase relative rates of heat carrier and particles of disperse material, also, facilitation of stable swirl flow of gas suspension and reduced power expenditures for drying process; increased efficiency of absorption of supplied energy with being dried material; simplified design of vortex drying chamber.

3 dwg

Description

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

Heat and mass transfer apparatuses with combined energy supply, operating in an active hydrodynamic mode and using a swirling flow of heat carrier as one of the most effective means of intensifying the drying process of dispersed materials, are widely used in industry.

Closest to the proposed technical essence and the achieved result is an apparatus for drying dispersed material in an active hydrodynamic mode with a microwave energy supply [Patent RU No. 2312280, F26B 17/00, F26B 3/347, 12/10/2007], containing a swirl chamber with an inlet a pipe for introducing gas suspension, microwave emitters with protective shields and fluoroplastic windows.

The drying chamber of this unit has several disadvantages:

- low quality of the dried material due to its abrasion on the inner surface of the chamber;

- violation of the stability of the rotating annular layer during drying of coarse materials due to the formation of "blockage" in the zone of rise of the dried particles;

- significant energy costs to maintain the necessary speed of the coolant to maintain a constant value of the centrifugal force holding the layer of dispersed material in the chamber;

- the need to install a large number of microwave emitters having special waveguides of complex configuration for uniform distribution of the microwave energy flux throughout the chamber, which complicates the design and increases the cost of its manufacture.

An object of the invention is to improve the quality of the dried material, the intensification of heat and mass transfer processes, reducing energy costs for the drying process of dispersed materials, ensuring stabilization of the active hydrodynamic regime of the vortex drying chamber and uniform distribution of the microwave energy flow throughout the chamber volume, simplifying the design of the vortex drying chamber and reducing the cost of its manufacture.

The object of the invention is achieved in that in a vortex drying chamber for drying dispersed material in a swirling flow of a heat carrier with a microwave energy supply, including a cylindrical body with an inlet pipe for introducing a gas suspension and a discharge pipe for outputting dried material, equipped with a microwave emitter, is new that the inner surface of the housing of the vortex drying chamber is equipped with a fluoroplastic coating to reduce the abrasion of the dried material, a pipe for introducing gas suspension made tapering at the entrance to the drying chamber, inside the vortex drying chamber on its lateral surface there are local accelerators of the coolant flow and guide inserts made of radiolucent material, and local accelerators of the coolant flow are fixed on the side surface inside the vortex drying chamber in such a way as to form a stable rotating an annular layer of dried material particles and exclude the possibility of their accumulation in the zone of maximum resistance to movement itz, and the guide inserts separating the dried particles from the main rotating annular layer and directing them to the central zone of the vortex drying chamber are located in the zone of return of the particles to the lift point, the microwave emitter is mounted tangentially on the outer cylindrical surface of the vortex drying chamber body so that the highest electromagnetic energy flux density was concentrated in the zone of the rotating annular layer of the dried material particles.

The technical result of the invention is to improve the quality of the dried material, to intensify the processes of heat and mass transfer by increasing the activity of the hydrodynamic situation in the drying chamber due to an increase in the interfacial relative velocities of the coolant and particles of dispersed material, in ensuring the stability of the swirling flow of gas suspension and in reducing energy consumption for the drying process , in increasing the efficiency of absorption of the supplied energy by the dried material, in simplifying the design of the vortex second drying chamber.

Figure 1 shows a General view of the vortex drying chamber for drying dispersed material; figure 2 is a frontal view of the vortex drying chamber; figure 3 - diagram of the forces acting on the particle in a swirling flow of coolant.

A vortex drying chamber for drying dispersed material in a swirling flow of a coolant with a microwave energy supply (FIGS. 1, 2) comprises a cylindrical body 1, a pipe 2 for introducing a gas suspension, made narrowing at the entrance to the drying chamber, the inner surface of the housing of the vortex drying chamber is provided with a fluoroplastic coating 3 to reduce the coefficient of friction of material particles on the inner surface of the housing of the vortex drying chamber, local accelerators of the coolant flow 4 are mounted on the side surface inside the housing and the vortex drying chamber in such a way as to form a stable rotating ring layer of the dried particles of the material and to exclude the possibility of their accumulation in the zone of maximum resistance to the movement of particles and are located in the lifting zone of the dried material, the guide inserts 5 separating the dried particles from the main rotating layer and directing them into the central zone of the vortex drying chamber, located in the zone of return of particles to the point of rise, the microwave emitter 6, mounted tangentially on the outer cylinder the surface of the casing 1 of the vortex drying chamber so that the highest electromagnetic energy flux density is concentrated in the zone of the rotating annular layer of the dried material particles, the outlet pipe 7 for the output of the dried material.

The drying of the dispersed material in a vortex drying chamber is as follows.

A gas suspension formed after the wet dispersed material is fed into the coolant is pumped into the working space of the vortex drying chamber 1 through a pipe 2 for introducing a gas suspension, tapering at the entrance to the drying chamber to increase the speed of the coolant. In this case, the material to be dried falls into the zone of maximum resistance to its movement (Fig. 3), in which there is the greatest likelihood of the accumulation of dried particles due to the increase in this section of the drying chamber of the action of the resistance forces to the movement of the material and, as a result, the stability of the rotating annular layer . This zone is determined by the change in the angle α of the slope of the tangent a - a, drawn to the surface of the chamber through the contact point of each particle of the material to be dried with this surface, to the horizontal 0 - 0 in the range 0 ° ... 90 °.

Presented in figure 3, the diagram illustrates the action on each particle of the dried material of the following forces:

1) the hydrodynamic drag force F _GD , N

,

,

where ξ is the coefficient of hydraulic resistance of the chamber;

d is the particle diameter of the dried material, m;

ρ is the density of the coolant, kg / m ³ ;

ω is the flow rate of the coolant, m / s;

υ is the absolute velocity of the particle, m / s.

2) normal pressure force (reaction of the concave chamber wall) N, N;

3) the friction force of the particle on the inner surface of the chamber F _Tr , N

F _Tr = fN,

where f is the coefficient of friction of the particle on the material of the inner surface of the chamber;

4) gravity F _t N

F _t = mg,

where t is the particle mass, kg;

g = 9.81 - acceleration of gravity, m / s ² .

5) the centrifugal force F _c, H

,

,

where R is the radius of the inner surface of the drying chamber, m

Analyzing the presented scheme (Fig. 3), we can conclude that the acting forces affect the particle acceleration of the dried material, which in inertial systems is directly proportional to the magnitude of the resultant of these forces and inversely proportional to the particle mass:

.

.

- ускорение частицы;Where

- particle acceleration;

- равнодействующая всех сил, действующих на частицу.

- the resultant of all forces acting on the particle.

When a particle passes through a zone of maximum resistance to its movement, the equations of motion of this particle in projections on the o-x and o-y axes of the selected coordinate system can be represented as:

From here:

The motion of the particle in question is determined by the equation

Then the particle acceleration in the general case will be determined by the dependence:

where α is the angle of inclination of the tangent a - a, drawn to the surface of the vortex drying chamber through the point of contact of the particle with this surface, to the horizontal 0-0, deg.

From the above dependence it follows that the friction coefficient f of the particle on the material of the inner surface of the vortex drying chamber, the angle α of the slope of the tangent a - a, drawn to the chamber surface through the contact point of each particle of the material to be dried with this surface, to the horizontal 0 -0, as well as a decrease in the flow rate of the coolant ω.

In order to reduce the effect of the coefficient of friction on the acceleration of the particles of the dried material, as well as to prevent its abrasion, the inner surface of the vortex drying chamber 1 is equipped with a fluoroplastic coating 3.

The greatest influence of the angle α of the inclination of the tangent a - a, drawn to the chamber surface through each contact point of the particles of the material to be dried with this surface, to the horizontal 0-0 on the particle acceleration is observed in the range α = 0 ° ... 90 ° (in the zone of maximum resistance to particle motion ), since at α = 0 ° ... 90 ° cosα> 0 and sinα> 0, therefore, when a particle passes through the dispersed material in this zone, its deceleration will be maximum.

In the range α = 90 ° ... 180 °, the influence of gravity and normal pressure forces reduce the friction of the particle on the inner surface of the vortex drying chamber. Analyzing dependence (1), we see that in the range α = 90 ° ... 180 ° cosα <0. This suggests the possibility of accelerating a particle of material in this section of the chamber.

However, the particle does not receive the necessary acceleration in this section of the vortex drying chamber due to a decrease in the coolant velocity. Since the flow rate of the supplied and spent coolant is the same, its speed depends on the cross-sectional area of the gas duct. The cross-sectional area of the drying chamber increases sharply immediately after the nozzle 2 for introducing a gas suspension. As a result of this, a significant dispersion of the kinetic energy of the gas stream into the working space of the vortex drying chamber and a decrease in the flow rate of the coolant occur.

The increase in the flow rate of the coolant without increasing its flow rate and, consequently, increasing the pressure loss in the discharge section (and therefore without increasing energy consumption) is achieved using local accelerators of the flow of coolant 4 located in the zone of particles of the dried material, defined by the interval α = 0 ° ... 180 °, and fixed on the side surface inside the housing 1 of the vortex drying chamber in such a way as to form a stable rotating ring layer of dried particles of material and to exclude the possibility their accumulation in the zone of maximum resistance to particle motion.

The rotation of the particles of the wet material during the main drying time occurs in the wall zone of the vortex drying chamber 1. During the drying process, the moisture content of the particles decreases, their mass decreases, as a result of which the centrifugal force F _c decreases. As a result, lighter dried particles are radially displaced toward the center and, with the help of guide inserts 5, are separated from the rotating annular layer and sent to the central zone of the vortex drying chamber 1, where they continue to rotate until they are completely dried and entrained through the outlet pipe 7.

The installation distance of the local accelerators of the coolant flow 4 and the guide inserts 5 from the center of the chamber is determined by the type and size of the particles of the dried material.

To intensify the process of heat and mass transfer and ensure the best conditions for the absorption of the input energy by the particles of the material, the microwave emitter 6 is installed on the outer cylindrical surface of the vortex drying chamber 1 in the area of the guide inserts 5, where the gas suspension is reduced and the maximum effect of electromagnetic radiation on the material particles is directed into the working space of the camera so that the electromagnetic waves emitted by it, reflected from the inner cylindrical surface swirl drying chamber 1, evenly distributed in a rotating annular layer where the highest concentration of the material being dried is observed.

Thus, the proposed vortex drying chamber for drying dispersed material in a swirling flow of a heat carrier with a microwave energy supply has the following advantages:

- the proposed vortex drying chamber is universal, that is, it can be used in all industries where drying of dispersed materials is necessary;

- the implementation of the inner surface of the vortex drying chamber with a fluoroplastic coating can reduce the abrasion of the particles, resulting in significantly improved quality of the dried material;

- ensuring the regular movement of particles of the dried material, that is, the stability of the hydrodynamic situation in the working space of the vortex drying chamber is ensured, heat and mass transfer is intensified and energy consumption for the drying process is reduced;

- the use of the proposed drying chamber can improve the quality of drying of all classes of dispersed materials by ensuring uniform absorption of the supplied energy.

- reducing the number of microwave emitters, eliminating the use of special waveguides of complex configuration for uniform distribution of the microwave energy flux over the chamber volume simplifies the design of the vortex drying chamber and reduces the cost of its manufacture.

Claims (1)

Vortex drying chamber for drying dispersed material in a swirling flow of a coolant with a microwave energy supply, containing a cylindrical body with a nozzle for introducing a gas suspension and a discharge nozzle for outputting dried material, equipped with a microwave emitter, characterized in that the inner surface of the housing of the vortex drying chamber is provided with a fluoroplastic coating to reduce the abrasion of the dried material, the pipe for introducing a gas suspension is made tapering at the entrance to the drying chamber, inside the drying chamber on e On the side surface, local coolant flow accelerators and guide inserts made of radiolucent material are installed to freely transmit electromagnetic waves and to eliminate uneven distribution of microwave energy, and local coolant flow accelerators are fixed on the side surface inside the drying chamber in such a way as to form a stable rotating ring layer dried particles of material and exclude the possibility of their accumulation in the zone of maximum resistance effects on the movement of particles, and guide inserts separating the dried particles from the main rotating annular layer and directing them to the central zone of the vortex drying chamber are located in the zone of return of the particles to the lift point, the microwave emitter is installed tangentially on the outer cylindrical surface of the vortex drying chamber body in this way so that the highest electromagnetic energy flux density is concentrated in the zone of the rotating annular layer of the dried material particles.

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