RU2293267C2 - Device for drying poly-dispersed materials - Google Patents

Abstract

FIELD: thermal drying of dispersed materials in suspended state for removal of surface moisture; manufacture of building materials; mechanical engineering; chemical and other industries.

SUBSTANCE: proposed device includes heat generator, pneumatic tube, taper expander, drying and settling chamber provided with cover and loading and unloading branch pipes for material and heat-transfer agent (air). Taper expander has clearance in lower section relative to pneumatic tube whose size is equal to is more than two-fold value of maximum size of particles. Gas distributing screen at open area of 7-20% is additionally mounted between taper expander and cover of drying and settling chamber. Height of taper expander exceeds its minimum diameter and ratio of its maximum and minimum diameters ranges from 1.8 to 3.0.

EFFECT: enhanced reliability and efficiency of drying; low level of entrainment of finely-dispersed materials.

2 dwg

Description

The invention relates to a drying technique, and more particularly to highly efficient thermal drying of dispersed materials in suspension, mainly to remove surface moisture, and can be used in the production of building materials, in mechanical engineering, in the chemical industry and other industries.

A device for drying finely dispersed materials is known, including a heat generator, a pneumatic tube, a conical expander, a drying and settling chamber, loading and unloading nozzles of material and coolant (a.c. SU No. 1078221, 03.03.1984, “Device for drying finely dispersed materials”). The disadvantage of this device is the insufficiently high level of reliability of the device during drying of polydisperse material, the presence of several discharge pipes of the material and coolant, which leads to the need for additional equipment and significantly increases the dimensions, weight and cost of the device and the technological complex as a whole.

A device for drying fine materials, including a pneumatic tube, a conical expander with a cylinder having a gap with its upper part, a drying and settling chamber, loading and unloading pipes of material and coolant (air) (A.S. SU No. 645010, 01/30/1979, "Device for drying dispersed materials"). This device is the closest to the claimed. The disadvantage of this device is its accessory for effective drying of dispersed material with only a small range of particles in fractional composition.

When drying dispersed materials in a pneumofontaneous installation, the coolant speed is selected from the condition of the duration of stay of material particles in the pneumatic fountain section, at a level of more than 1 second. With a shorter duration of the drying process, the moisture in the material, as a rule, does not have time to evaporate, and the waste heat carrier has an elevated temperature. As a result of this, the technological requirement for the moisture content of the dried material is not provided and the efficiency of the drying process is reduced.

When drying a material with a significant particle size (for example, when drying quartz sand with a particle size of up to 10 mm), for the removal of large particles, it is necessary to significantly increase the speed of the coolant, primarily at the outlet of the conical expander, and therefore in the pneumatic tube. This leads to a decrease in the length of stay of small particles (0.1-0.3 mm) of the material in the pneumatic area to a time significantly less than 1 second. When drying a polydisperse material with a decrease in the velocity of the coolant to a level lower than the speed of large particles in the upper part of the conical expander, the latter cannot fly out of the conical expander. As a result of the indicated in the expander, the accumulation of large particles occurs, which leads to an increase in the aerodynamic resistance of the air-fountain section, a decrease in the flow of coolant and the performance of the device. When the critical mass of the material accumulated in the expander is reached, it collapses, which causes an emergency during operation of the device. To eliminate these drawbacks, it is necessary to ensure the withdrawal of large particles of material from the bottom of the conical expander.

The aim of the present invention is to ensure reliability and drying efficiency of a polydisperse material and to reduce the level of removal of finely divided material.

This goal is achieved by the fact that in the device for drying polydisperse materials, including a heat generator, a pneumatic tube, a conical expander, a drying and precipitation chamber with a roof in its upper part, loading and unloading pipes of the material and coolant (air), according to the invention, a conical expander in the lower section in relation to the pneumatic tube there is a gap with a size equal to or greater than twice the maximum particle size, the height of the conical expander exceeds its minimum diameter, the ratio of max its minimum and minimum diameters is in the range from 1.8 to 3.0, and between the conical expander and the roof of the drying and precipitation chamber an additional gas distribution sieve with a live cross section of 7-20% is installed.

Figure 1 shows the inventive device, consisting of a heat generator 1, a drying and precipitation chamber 2, a pneumatic pipe 3, a conical 4 expander coaxial with it, a gas distribution sieve 5, material loading pipes 6 and unloading 7, atmospheric air inlet 8 and outlet 9 waste heat carrier. Between the small diameter of the conical expander 4 and the pneumatic pipe 5, a gap 10 is provided for separating large particles of material from the coolant flow in the conical expander, and a nozzle with a shutter 11 is provided under the pneumatic pipe for the failure of large particles of material not picked up by the coolant flow in the pneumatic pipe. The upper part of the drying and precipitation chamber 2 ends with the roof 12. Figure 2 shows on a larger scale the junction of the pneumatic tube 3 and the conical expander 4.

A drying unit operates as follows. The hot heat carrier from the heat generator 1 enters the pneumatic pipe 3 and meets with the polydisperse material, for example quartz sand after the quarry, having large gravel particles included, coming through the pipe 6 (it is possible to feed the material through the roof 12 above the pneumatic pipe 3). Encountering an upward flow of coolant, the material is picked up and transported to a conical expander 4. Small particles of material, the whirling speed of which is less than the flow velocity in the upper part of expander 4, fly out of the latter and settle in the drying and precipitation chamber, and large particles of material that are not capable of fly out of the expander 4, unloaded through the gap 10 in its lower part.

To exclude the entrainment of 2 particles larger than a predetermined size (for example, 0.1 mm) from the drying and settling chamber (for example, 0.1 mm), its cross section is selected from the condition of the coolant velocity equal to or lower than the speed of the particles soaring at a given size. The presence of the gas distribution sieve 5 under the roof of the chamber 2 helps to equalize the flow of the coolant in speed and reduce the removal of the necessary fractional composition of the material. The waste heat carrier previously cleaned in chamber 2 is discharged into the atmosphere by a fan.

Polydisperse material, for example quartz sand from a quarry, has a particle size of mainly from 0.05 to 1.0 mm with the presence of larger gravel inclusions that cannot be separated mechanically when wet and therefore have to be loaded into a drying unit. The speed of movement of particles with a size of 1.0 mm is 6 m / s, which, as a rule, is close to the values of the velocity of the coolant at the outlet of the expansion cone 4, and particles of a larger diameter cannot fly out of it. The presence of a gap 10 between the pneumatic tube 3 and the lower part of the conical expander 4 allows you to unload larger particles through it and prevent their accumulation in the expander. According to the operation of a pneumofontaneous installation for drying quartz sand at Aragon Ltd CJSC, particles up to 15 mm in size were removed through the specified gap 10. To exclude clogging of the gap, its size should exceed twice the size of the particles and was 35 mm. If the height of the conical expander 4 is insignificant (less than its minimum diameter), and the ratio of its maximum and minimum diameters is less than 1.8, then the residence time of the material in the pneumatic fountain section will be less than 1 second, and the material may not have time to dry. If the value of the ratio of the maximum and minimum diameters of the expander is more than 3.0, a practically significant part of the material will be discharged through the gap 10, which may lead to the presence of un-dried material in it.

The boundary values of the live section of the gas distribution sieve 5 are selected in the range from 7 to 20%. With values of the living cross section of the sieve of large 20%, the aerodynamic resistance of the sieve 5 is insignificant, and this leads to a significant unevenness of the velocities of the coolant in the drying and precipitation chamber 2 and an increase in the ablation of useful material particles. If the live section is less than 7%, the uniformity of the coolant flow in the drying and settling chamber will not noticeably improve, however, the absolute value of the aerodynamic resistance of the gas distribution sieve will be significant and, as a result, the efficiency of the process will decrease without a visible increase in its efficiency.

Thus, the claimed device provides an effective and high-quality drying mode of polydisperse materials, for example quartz sand after a quarry.

Positions and symbols in figures 1 and 2.

1 - heat generator;

2 - drying and precipitation chamber;

3 - pneumotube;

4 - conical expander;

5 - gas distribution sieve;

6 - pipe loading material;

7 - pipe unloading material;

8 - pipe air inlet to the heat generator;

9 - exhaust pipe outlet;

10 - the gap between the lower part of the conical expander and the pneumatic tube;

11 - pipe with a flap to remove spills from the pneumatic pipe;

12 - the roof of the drying and precipitation chamber.

Claims (2)

1. A device for drying polydisperse materials, including a heat generator, a pneumatic tube, a conical expander, a drying and precipitation chamber with a roof in its upper part, loading and unloading pipes of the material and coolant (air), characterized in that the conical expander in the lower section has a ratio there is a gap to the pneumatic tube with a size equal to or greater than twice the maximum particle size, and a gas distribution is additionally installed between the conical expander and the roof of the drying and precipitation chamber e sieve with a live section of 7-20%. 2. The device according to claim 1, characterized in that the height of the conical expander exceeds its minimum diameter, and the ratio of its maximum and minimum diameters is in the range from 1.8 to 3.0.

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