RU2283995C2 - Device for drying capillary-porous materials - Google Patents

Abstract

FIELD: drying.

SUBSTANCE: device comprises drying chamber soundproof baffles that are mounted in the drying chamber and separate the space of the chamber into isolated sections, each of which is provided with the individual sound source, and the source of heated air mounted for permitting the heated air to flow from the source to each section of the drying chamber.

EFFECT: reduced cost of drying.

6 cl, 1 dwg

Description

The invention relates to means for drying various, mainly capillary-porous materials and can be used in agriculture for drying grain and other agricultural products, in the woodworking industry for drying wood and sawdust, in the food industry for drying food, and also for the same purposes other industries.

A large number of devices are known for drying materials in various ways. For thermal drying, dry heated air is widely used as a drying agent, which is passed through a drying chamber containing a drying material. For example, there is a known dryer for drying wood, containing a drying chamber, the bottom of which has two cavities, one of which serves hot products of combustion from a hog from burning wood waste, and the other serves a drying agent - hot air, heated in pipes placed in Borov furnace [RF Patent No. 2153640]. To prepare the drying agent, electric heaters, for example, heating elements, and other known means can be used as a heat source.

To carry out acoustic drying, the drying chamber is equipped with a sound source emitting acoustic waves of certain parameters that act on the material to be dried and remove moisture from it. For example, it is known a device for drying grain in an acoustic way, including a hopper equipped with a feeder for supplying bulk material to a contact heat and mass exchanger, an intermediate cooling shaft connected to a heat and mass exchanger, and sound emitters with air flow reflectors are installed in perforated concentrators in height [A.S. USSR No. 675266, 1979]. The disadvantages of this device include low productivity and high energy consumption due to the simultaneous use of several sound emitters, as well as unsuitability for a more promising method of drying - acoustothermal.

The acoustothermal drying method includes both thermal and acoustic effects on the material to be dried. It consists in cyclic exposure of the material to be drained by an acoustic field, and in each cycle the material must first be heated [RF Patent No. 2215953, 2003]. The effect of such an effect on the material increases if there is a pause between cycles that is sufficient for moisture from the inner layers of the material to reach its outer layers through the pores or capillaries. This drying method is characterized by lower energy consumption relative to each of the mentioned acoustic and thermal drying methods.

A device is known for conducting only acoustic drying, which contains a drying chamber and a sound emitter, the drying chamber being made in the form of a duct — a sound duct along which containers with loading and unloading gates of the drained material having mesh walls are vertically located [RF Patent No. 2095707, 1997 .]. The main disadvantage of this device is its unsuitability for carrying out the aforementioned less energy-intensive acoustothermal drying method. This device is taken as a prototype of the invention for the greatest number of features similar to the proposed device.

The invention solves the problem of creating a device for drying capillary-porous materials suitable for drying by the acoustothermal method, while being simple in design and economical.

The problem is solved by the fact that a device for drying capillary-porous materials is proposed, including a drying chamber in which soundproof partitions are installed, dividing its internal volume into insulated sections, each of which is equipped with a separate sound source, as well as a heated air source installed in this way so that heated air flows from it into each section of the drying chamber.

Depending on the type of material to be dried, the drying chamber may have a different configuration.

So, for drying wood (logs and boards), it is advisable to make the body of the drying chamber in the form of a parallelepiped with parallel side vertical walls parallel to each other horizontal lower and upper walls, with soundproof partitions installed horizontally or combined-horizontally and vertically in the longitudinal direction (along the side of the chamber, having a large length), as well as means of loading / unloading, made in the form of an opening front or rear wall of the chamber. In this case, the sections are horizontal and have a length equal to the length of the drying chamber. Sound sources are placed in each section on the rear or front wall of the camera. Heated air is supplied to each section separately.

The partitions between the sections are made soundproof, for example, they can be made of two layers of metal, between which there is soundproofing material: mineral wool, foam rubber, polystyrene foam, etc. The walls of the drying chamber can be made in the same way.

For bulk materials, the drying chamber can be of various shapes (its cavity may be a cylinder or parallelepiped), but to facilitate loading, it is advisable to arrange the sections and, accordingly, soundproof partitions vertically, and to place the material unloading means at the bottom of each section.

Also, for the bulk material, the same design as described above for wood can be used, but in this case the material should be placed in mesh containers with a mesh size smaller than the size of the bulk fraction that are installed in the section of the drying chamber.

To ensure uniformity of acoustic processing of the material being dried, the drying chamber must be equipped with a sound absorber, which is located on the side opposite to the wall on which the sound source is mounted. The sound absorber can be made in the form of a plate of sound-absorbing material, for example mineral wool, or in the form of special wedges of sound-absorbing material.

The source of heated air can be made in the form of means for heating air (for example, a tubular heat exchanger, tubular electric heater (TENA), or others) and means for forcing heated air into the drying chamber, for example, a fan.

A diagram of the drying chamber of the proposed device for drying wood with four sections is shown in the drawing, where 1, 2, 3, 4 are sections of the drying chamber, 5 is a sound emitter, 6 is a soundproof partition, 7 is a sound absorber.

The device operates as follows (for example, drying wood).

The drying chamber, as mentioned above, is divided by soundproofing partitions 6 into 4 sections, with sequential numbering: 1, 2, 3, 4. It is assumed that the optimal time for heating the material to be drained with heated air is 4 hours, and the optimal time of acoustic radiation per cycle is 1 hour.

Heated air to the required level is supplied to section 1. After 1 hour after it begins to be supplied to section 1, it also begins to be supplied to section 2. After 2 hours, heated air is supplied to sections 1, 2 and begins to be supplied to section 3. After 3 hours Heated air is supplied in sections 1, 2, 3 and begins to be supplied to section 4. The supply of heated air to all sections simultaneously continues for 1 hour. As a result, after 4 hours of operation of the device, the heated air was supplied to section 1 for 4 hours, to section 2 for 3 hours, to section 3 for 2 hours, to section 4 for 1 hour. After that, the supply of heated air to section 1 is stopped and the sound source is turned on for 1 subsequent hour, and the heated air continues to flow into the remaining sections over the next hour. After that, the heated air ceases to be supplied to section 2 and the sound source of this section is turned on for 1 hour. After another 1 hour, the supply of heated air to section 3 is stopped and the sound source of this section is also turned on for 1 hour. After another 1 hour, the supply of heated air to section 4 is stopped and the sound source of this section is turned on for 1 next hour. The process is then repeated. As a result, in each section, the material is treated with heated air for 4 hours, and sound processing for 1 hour. Further, the described sequence of operations is repeated many times until the desired value of the final moisture of the material to be dried is reached.

To ensure the same drying speed of the material throughout the entire volume of the drying chamber, it is necessary to ensure the same sound intensity in its longitudinal and transverse sections. In a longitudinal section, this problem is solved by a sound absorber mounted on the boundary of the drying chamber, providing a traveling wave mode in the said section. To ensure the same sound intensity in the cross section of the drying chamber, it is necessary and sufficient that the sound wave propagating in it is flat. This requirement imposes a restriction on the choice of frequency (wavelength) of the emitted sound at a given cross-sectional size of the drying chamber. It is known that the wave in the channel — the sound pipe will be flat if the following condition is met [S.N. Rzhevkin “The course of lectures on the theory of sound” - Moscow: Moscow State University publishing house, 1960]:

Here, λ is the wavelength of the emitted sound, f is its frequency, and c is the speed of sound in the medium where it propagates (in this case, the medium is air, therefore c = 340 m / s).

For given characteristics of the emitter, the intensity of the sound emitted by it J is related to its characteristic linear size r and the frequency of the emitted sound (if the emitter is a dipole, which is typical for the situation under consideration) by the following relation:

Here k is the wave number of the emitted sound. If in (1) we use the limiting situation Δ = c / 2f, then from (2) we get:

From (3) it follows that for given characteristics of the emitter, the intensity of the sound emitted by it in the drying chamber, and therefore the drying speed of the material, very much depends on the ratio r / Δ. For example, for a given power of an external energy source supplying a sound emitter, and a fixed value of its linear size r, dividing the drying chamber into 4 sections, as shown in the drawing, increases the sound intensity in each section, and therefore the drying speed of the material by 16 times.

It is important to note that the consumption of slightly heated (40-60 °) air for heating the drained material requires much less energy than for supplying sound emitters.

As a result of dividing the drying chamber into several soundproof sections, the volume of its single load increases several times, i.e. her performance. Due to the increase in sound intensity in each section compared to a conventional single-section camera, the drying speed increases with the same power supplied to the sound emitter, which, accordingly, reduces the drying time. As a result, the device allows to reduce energy consumption, and this means an increase in the technical and economic indicators of drying. Moreover, the design of the device is simple and technological.

Claims (7)

1. Device for drying capillary-porous materials, including a drying chamber equipped with a sound source, characterized in that soundproof walls are installed in the drying chamber, dividing its internal volume into isolated sections, each of which is equipped with a separate sound source, while it contains a source heated air, made in such a way that the heated air comes from the named source into each section of the drying chamber. 2. The device according to claim 1, characterized in that the soundproof partitions in the drying chamber are installed horizontally. 3. The device according to claim 1, characterized in that the soundproof partitions in the drying chamber are installed vertically. 4. The device according to claim 1, characterized in that the soundproof partitions in the drying chamber are installed horizontally and vertically. 5. The device according to claim 1, characterized in that the soundproof partitions are made of two layers of metal, between which is a layer of a material impervious to sound. 6. The device according to claim 1, characterized in that the drying chamber is equipped with a sound absorber. 7. The device according to claim 1, characterized in that the source of heated air contains means for heating the air and means for supplying it to the drying chamber.