RU2306507C1 - Pneumatic drier - Google Patents

Abstract

FIELD: drying of dispersed material; microbiological, food-processing, chemical and other industries.

SUBSTANCE: proposed pneumatic drier has moist material loading bin with screw feeder, drying chamber, calorifier, fan and used air cleaning system. Mixing chamber is mounted at calorifier inlet. Drying chamber is made in form of tube at whose outlet acoustic plant is mounted for entrapping dust. This plant is connected with cyclone and bag filter. Fan is mounted at filter outlet and unloading unit is connected with cyclone bin.

EFFECT: increased productivity.

2 cl, 1 dwg

Description

The invention relates to techniques for drying dispersed materials and can be used in microbiological, food, chemical and other industries.

The closest technical solution to the claimed object is a dryer by.with. USSR No. 553424, F26В 17 / 10.1975, containing a loading hopper of wet material with a screw feeder, a drying chamber, a heater, a fan and an exhaust air purification system (prototype).

The disadvantage of the prototype is the relatively low productivity of drying the final product.

The technical result is an increase in drying performance.

This is achieved by the fact that in a pneumatic dryer containing a hopper of wet material with a screw feeder, a drying chamber, an air heater, a fan and an exhaust air purification system, a mixing chamber is installed at the inlet of the electric air heater, and the drying chamber is made in the form of a pneumatic tube, the output of which is acoustic a dust collecting unit connected to a cyclone and a bag filter, the fan being installed at the outlet of the filter and the discharge device connected to the cyclone hopper.

The drawing shows a diagram of a pneumatic dryer.

The pneumatic dryer contains a fresh air supply system 1, an electric air heater 2, at the entrance of which a mixing chamber 9 is installed, a hopper of wet material with a screw feeder 3, a drying chamber in the form of a pneumatic tube 4, at the output of which an acoustic dust collecting unit 10 is connected to the cyclone 5 and a bag filter 7. A fan 8 is installed at the outlet of the filter 7, and the discharge device 6 is connected to the cyclone hopper 5. The optimal parameters for sound processing in an acoustic installation of media fine dust with a concentration of at least 2 g / m in air flow is the sound pressure level in the range of 140 ... 150 dB, the frequency of the oscillatory process in the range of 800 ... 1000 Hz, the sounding time in the range of 1.5 ... 2 from.

The air tube 4 can be made of variable cross-section (not shown in the drawing) so that the flow rate and residence time of the material in each section are different. The air pipe 4 can be made of two coaxially arranged pipes, in which the wet material is pre-dried when moving upward through the outer pipe, and then sent to the inner pipe with a screw insert, where residual moisture is removed in the turbulent flow. This type of pneumatic dryer makes it possible to achieve lower moisture content of the material and to intensify the heat transfer process.

Pneumatic dryer operates as follows.

Wet material from the loading hopper with a screw (or other design) feeder 3 is continuously fed into the drying chamber in the form of a pneumatic tube 4. Heated air mixed with exhaust air from the mixing chamber 9 is supplied by means of a fan 8 to an electric air heater 2, and from it to the drying chamber. Unloading of the dried product is carried out through the device for unloading 6, connected to the cyclone hopper 5. The exhaust dusty air is subjected to preliminary acoustic treatment in an acoustic installation 10 for collecting dust. The drying agent (coolant - heated air or flue gases) together with small particles of the product enters the acoustic installation, the sound vibration parameters of which are adjusted from the control unit. In an acoustic installation, dust particles are separated from the coolant, since under the influence of the sound field and the associated oscillatory processes occurring in the medium of the spent coolant, the dust particles stick together, that is, coagulate, forming large aggregates, which greatly facilitates the subsequent cleaning of the coolant in gas cleaning devices . The following main factors act on suspended particles under the influence of acoustic vibrations: joint oscillation of particles and a gas medium, dynamic forces between neighboring particles. Large particles settle down either in an acoustic installation or enter a cavity associated with an inertial dust separator.

The optimal parameters for sound processing of medium-sized dust are the sound pressure level of 140 dB or more, the oscillation frequency of 900 Hz, the dust concentration in the flow of the drying agent is at least 2 g / m, the sounding time is 1.5 ... 2 s. These parameters are due to the fact that, depending on their size, the suspended particle either participates in the oscillations of the medium (fully or partially), or does not participate, since the Stokes forces act on the particle and the medium. Moreover, when sound waves are transmitted through the volume of a gas located in a closed vessel, standing sound waves are established in the latter with the formation of nodes (the oscillation velocity is zero) and antinodes in which the amplitude of the velocity oscillations is maximum. The frequency of the oscillatory process, equal to 900 Hz, creates for the dust concentration in the coolant flow equal to at least 2 g / m ³ such an amplitude of the sound wave at which the amplitude of the velocity of the gas particle, determined by the ratio of sound intensity (sound pressure level 140 dB or more) to the speed of sound in the medium, will be in the antinode region of standing sound waves in a given closed vessel (acoustic installation), which ultimately determines the intensity of acoustic coagulation, that is, the rate of formation of large parts its. The scoring time of 1.5 ... 2 s is assigned from the condition of formation of an antinode of standing sound waves in a given closed vessel. If the scoring time is outside the range of 1.5 ... 2 s, this will lead to the formation of nodes in standing waves (the oscillation speed is zero), and, as a result, to weaken the effect of acoustic coagulation.

In the pharmaceutical industry, the proposed pneumatic dryer can be used to dehydrate the tetracycline base. Tetracycline (initial humidity 30 ... 35%) is dried in a stream of hot air having a temperature at the inlet of the pipe 130 ° C (final humidity 15 ... 17%). The productivity of the dryer for the dried product is about 20 kg / h. The use of this dryer makes it possible to abandon bulky shelf cabinets, make the drying process of the tetracycline base continuous, intensify the process, dramatically reduce the length of time the material is in the zone of elevated temperatures. In addition, it can be used for drying such preparations as norsulfazole, amidopyrine, intermediates for the production of chloramphenicol, ascorbic acid, and others. A pneumatic dryer can successfully combine the processes of filtration, drying, and transport of the product to the place of unloading.

Claims (2)

1. Pneumatic dryer containing a hopper of wet material with a screw feeder, a drying chamber in the form of a pneumatic tube connected to a cyclone, an unloading device connected to a cyclone hopper, a heater, a fan, characterized in that a mixing chamber is installed at the inlet of the air heater, at the outlet The drying chamber has an acoustic dust collection unit connected to a cyclone and a bag filter, the fan being installed at the filter outlet. 2. The pneumatic dryer according to claim 1, characterized in that the sound pressure level in the range of 140 ... 150 dB, frequency is optimal parameters for sound processing in an acoustic installation of medium-sized dust with its concentration in the air stream of at least 2 g / m ³ oscillatory process in the range of 800 ... 1000 Hz, scoring time in the range of 1.5 ... 2 s.