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Dryer aerodynamic. Principle of action and advantages.

In the production of briquette products or granulation of any biomass, the determining factor for obtaining a high-quality final product is the moisture content of the feedstock. As a rule, any plant growing waste (husks of grain crops, straw, sunflower or corn stalks), woodworking waste (sawdust, bark, shavings, wood chips, etc.) or peat, lignin, coal dust are used as such raw materials. . In most cases, the moisture content of the feedstock significantly exceeds that required for production. Therefore, removing excess moisture or drying is an important part of the technological process. During the drying process, moisture is removed from the material by evaporation and the resulting vapors are removed. In addition, if the resulting briquettes or pellets are planned to be used as biofuels, then the preliminary drying of the raw materials will significantly increase the heat obtained during their combustion.

 

 

Currently, a lot of various equipment has been developed for drying raw materials. For drying fine materials, an aerodynamic dryer is best suited. It has a number of advantages over other types of equipment produced for similar purposes. These include:

  1. compactness, which significantly reduces the cost of buildings, foundations, transport elements, etc.;
  2. fire safety, as a result of the low temperature of the drying agent;
  3. simple installation process at the customer's site;
  4. short time required to start, wake up or stop;
  5. high degree of automation, the operator controls the drying parameters from the control panel;
  6. low maintenance;
  7. The resulting raw material has a homogeneous nature of a fine fraction, ideal for the production of fuel briquettes.

 

In an aerodynamic dryer, air preheated in a heat exchanger is used as a drying agent. The speed of the drying process depends on the degree of its heating, on its temperature. Also, the drying time is greatly affected by the relative speed of the drying agent, the specific surface area of the dried particles and the physical properties of the raw material.

Wet raw materials are fed from the feed hopper to the drying chamber. There it is picked up by the drying agent, twisting together with it and forming the so-called "fluidized bed". Twisting is facilitated by a special gas distribution grill and tangential material feed. Therefore, aerodynamic dryers are referred to as "fluidized bed" dryers.

As the drying progresses, the initial moisture content, which is the same in the entire volume of the raw material supplied, decreases. Because the moisture evaporates from the surface of the dried particles, and the internal moisture does not have time yet, due to the concentration gradient, it will move to the surface. There is a slight delay in the drying process. The temperature of the material begins to rise and approaches the temperature of the drying agent. Therefore, we have the need to control and limit the temperature of the applied drying agent, due to the possibility of ignition of fine dry particles of the processed raw material. Given the above, an aerodynamic dryer operates at an air temperature of 120 - 150 ° C, which almost completely eliminates the risk of ignition of dried particles. In addition, the drying process is significantly accelerated due to the intense friction of particles against each other in a dense layer, when moving at a high circumferential speed. In this case, the speed of the drying agent relative to the material particles in the drying chamber is 25 - 28 m/s. Thus, the drying of the material in the aerodynamic unit is ensured by intensive mass-air exchange. And bringing the moisture content of the product to the desired level is due to the control of the time spent by the raw material in the drying chamber, by creating a "fluidized bed" of a certain height.

Rational technical solutions in this equipment make it possible to use an aerodynamic dryer for drying a variety of fine-grained materials in a compact design apparatus, in small production areas. The dryer starts up within a few minutes, and the drying process itself is easily controlled and controlled by the operator. Compared to e.g. vacuum dryers, the drying time and energy consumption are significantly lower when drying in a pulsed fluidized bed.

The basic design of the aerodynamic dryer produced by our company, with an output of 400-800 kg of dry product per hour, consumes 7.5-11 kW of electricity. Moreover, this performance is calculated for the incoming moisture content of raw materials of 60%, and at the exit of 10-12%. But the productivity of the equipment may decrease in proportion to the increase in the moisture content of the feedstock. The air used as a drying agent is heated in a heat generator equipped with a spark arrestor. The heat generator works on woodworking waste, with a firewood consumption of about 60-80 kg/h.

Installations produced by our company, if the customer wishes to receive equipment with certain parameters, can be finalized and adapted according to an individual order.

 

Main characteristics of aerodynamic dryers

Type of aerodynamic dryerAC 1000
Performance 1000 kg/hour
Engine power 22 kW
Humidity of raw materials at the entrance 50-60%
Humidity of raw materials at the exit 8-12%
Raw material fraction size 1-7 mm
Air temperature 180-250 С
Length 8000 mm
Width 2500 mm
Height 4000 mm
Weight 2500 kg