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Classification of dryer
Jun 01, 2018

Modern dryer began to use intermittent fixed bed dryer. In the mid-19th century, the use of the tunnel dryer marked the development of the dryer from intermittent operation to continuous operation. The rotary cylinder drier can realize the stirring of granule material, and the drying ability and strength can be improved. Some industries have developed the continuous operation dryer to meet the requirements of the industry, such as textile, paper industry drum dryer.

In the early 20th century, the application of spray dryer in dairy production provided powerful tools for large-scale drying of liquid materials. Since the 1940s, with the development of fluidization technology, high-strength and high-productivity fluidized bed and gas-flow dryer appeared successively. The freezing sublimation, radiation and dielectric dryer provide new means to meet the special requirements. The far-infrared and microwave drier was developed in the 1960s.

There are many types of mechanical equipment used for drying operations. According to operating pressure, it can be divided into normal pressure and decompression (vacuum drier is also called vacuum drier). According to the operation method, it can be divided into intermittent type and continuous type. According to the dry medium can be divided into air, flue gas or other dry medium. According to the motion (material movement and dry medium flow) mode can be divided into parallel flow, countercurrent flow and wrong flow.

According to the operating pressure, drying machine is divided into two categories, atmospheric pressure drying machine and vacuum drying machine, operation can reduce the moisture of the space in the vacuum steam partial pressure and speed up drying process, and can reduce moisture boiling point and material drying temperature, steam is not easy to leak, so the vacuum drying machine is suitable for drying heat sensitive, easy oxidation, explosive and toxic materials, and moisture vapor recovery situation [2].

Advantage:

1. Well-designed adsorption tower

2. High performance activated alumina adsorbent

3. Effective silencer

4. Imported pneumatic controllers with unique features of power and durability

5. The recuperation valve that can accurately adjust the flow rate

According to heating method, the dryer is divided into convection type, conduction type, radiation type and dielectric type. The convection dryer, also known as the direct dryer, USES the hot dry medium to directly contact with the wet material, transfers the heat by convection and takes away the steam generated. Conduction type dryer is also called the indirect dryer, it USES the conduction way by heat transfer heat to the wet material through metal partition, the generated moisture vapor available vacuum suction and ventilation with a small amount of purge gas or in a separate set of low-temperature condensation on the condenser surface method. This kind of dryer does not use dry medium, high thermal efficiency, the product is not contaminated, but the drying ability is limited by the heat transfer area of the metal wall, the structure is more complex, often operate in a vacuum; Radiant dryer is to use a variety of radiators to emit electromagnetic waves of a certain wavelength range, which is selectively absorbed by the surface of wet materials and converted into heat for drying. Dielectric drier USES high frequency electric field to dry the wet material by heat effect.

Advantage:

1. High performance evaporator, large heat exchange area, small heat transfer temperature difference, more stable air temperature at evaporator outlet

2. High efficiency gas-water separation structure, high oil and water separation efficiency;

According to the movement mode of wet materials, the dryer can be divided into fixed bed type, agitator type, spray type and combination type. According to the structure, the dryer can be divided into the van, drying machine, drying machine, roller conveyor type dryer, vertical drying machine, the mechanical agitation type drying machine, rotary dryer, fluidized bed drying machine, pneumatic dryer, vibration dryer, spray dryer and combined-type dryer, etc.

Common knowledge of drying equipment: the common predryer in China has a common spray dryer, air dryer, fluidized bed dryer, flash dryer, fluidized bed dryer, such as spray granulation. Flash dryer spray drying spray drying is one of the most advanced equipment in drying equipment. Three traditional methods of atomization: rotary atomization, pressure atomization and airflow atomization. Rotational atomization features a large spray drying capability (spray volume up to 200 tons per hour) that will be responsible for easy control, operational flexibility, and wider application. Pressure atomizing spray drying is characterized by the creation of coarse particles for future maintenance. Because the nozzle hole is small and easily blocked, the liquid must be filtered strictly. Nozzle bore easy wear, wear - resistant material use. There is also a new structure of nozzle pressure, called pressure-flow nozzle. It is characterized by nozzle pressure, ambient air gap nozzle. Atomization is divided into two stages: the first is the formation of liquid film pressure nozzle, the film is the second air atomization, so that more small droplets. The advantages of this type of nozzle :(1) the pressure of compressed air can be adjusted, the droplet diameter can be adjusted, the operation is simple; (2) production of high viscosity liquid, which can atomize droplets of fine; If you disable compressed air, the original pressure nozzle can be used. Atomized airflow laboratory and major plants in the Middle East, its power consumption. The first two cannot atomize the nozzle liquid, use the air can atomize nozzle. High viscosity paste, paste and filter cake material, can be used for three - fluid nozzle atomization. The drier airflow drying technology is mature and can be directly designed if the data is manipulated.

Fluidized bed dryer fluidized bed dryer spray dryer. Feeding Settings are divided into a partial fluidized bed dryer agitator and a heat transfer fluidized bed dryer. As unity is easy to use fluidized bed drying, or gather the powder material feed more water will flow into the above difficult phenomenon, set up the feed mixer of the above, this time to eliminate cluster problems, in order to realize the normal flow. Which is the combination of heat conduction and convection heat transfer, when using the normal flow of hot air volume is far from enough, to meet the required thermal drying using set of heat exchanger, supply some or most of the heat, what type of operation can greatly save energy. A variety of heat exchangers are used. Fluidized bed drying is often used in combination drying medium education and high education. Implement the general vibration fluidized bed theory, vibration fluidized bed. There are two types of vibration sources for a flowing vibration: one is driven by a vibrating motor, and the other is caused by a vibration of a normal motor through a vibrating box, which makes a spring. When vibrating, the bed size, the latter is better. Fluidized bed spray granulation dryer, fluidized technology, atomized technology and drying organic combination of three. It is the seed that carries the atomized spray liquid into the fluidized bed, so the seed continues to grow and dry to reach the required size, time out of the catapult. The device has small and large production capacity and can create large particles. The equipment has been increasingly used in industry.

Changzhou city is the hometown of drying equipment in China, is now the nation's largest drying equipment industry to gather, drying equipment enterprise quantity the first, and the product also accounted for 40% of the country's market, drying, products are exported to the United States, Japan, France, South Africa and more than 30 countries and regions. In 2010, the drying industry formulated 18 "national standards", and changzhou dry enterprises participated in the whole process.

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