Classification of dryers

Modern dryers began to use intermittent operation of fixed bed dryers. In the mid-19th century, the use of tunnel dryers marked the development of dryers from intermittent operation to continuous operation. Rotary cylinder dryer can better realize the agitation of granular materials, and the drying capacity and strength can be improved. Some industries have developed continuous operation dryers that meet the requirements of the industry, such as drum dryers in the textile and paper industry.
In the early 20th century, spray dryers began to be used in dairy production, providing a powerful tool for large-scale drying of liquid materials. Since the 1940s, with the development of fluidizing technology, high-strength and high-productivity boiling beds and gas-flow dryers have appeared one after another. Cryosublimation, radiation and dielectric dryers provide new means to meet special requirements. In the 1960s, far-infrared and microwave dryers were developed.
There are many types of mechanical equipment used for drying operations, which can be divided into atmospheric pressure and vacuum pressure according to the operating pressure (vacuum dryer is also known as vacuum dryer). According to the operation method can be divided into intermittent and continuous. According to the drying medium can be divided into air, flue gas or other drying medium. According to the movement (material movement and drying medium flow) can be divided into parallel flow, counter-flow and cross-flow.
According to the operating pressure, the dryer is divided into two categories: atmospheric dryer and vacuum dryer. The operation under vacuum can reduce the pressure of the wet steam in the space and accelerate the drying process, and can reduce the wet boiling point and the drying temperature of the material. The steam is not easy to leak out. Vacuum dryers are suitable for drying heat-sensitive, easily oxidized, explosive and toxic materials as well as wet steam recovery occasions.