Development and classification of dryers

        Modern dryers began to use fixed bed dryers with intermittent operation. In the mid-19th century, the use of tunnel type dryers marked the development of dryers from intermittent operation to continuous operation. The rotary drum dryer effectively realizes the stirring of granular materials, and improves the drying capacity and strength. Some industries have developed continuous operation dryers that meet the requirements of their respective industries, such as drum dryers in the textile and paper industries.

        In the early 20th century, spray dryers were used in dairy production, providing a powerful tool for large-scale drying of liquid materials. Since the 1940s, with the development of fluidization technology, high-strength and high productivity fluidized beds and airflow dryers have emerged one after another. However, freezing sublimation, radiation, and dielectric dryers provide new means to meet special requirements. Since the 1960s, far infrared and microwave dryers have been developed.

        There are many types of mechanical equipment used for drying operations, which can be divided into normal pressure and reduced pressure (vacuum dryer, also known as vacuum dryer) based on the operating pressure. According to the operation method, it can be divided into intermittent and continuous types. According to the drying medium, it can be divided into air, flue gas, or other drying media. According to the mode of movement (material movement and drying medium flow), it can be divided into parallel flow, counter flow, and cross flow.www.jiashengsz.com

        According to the operating pressure, dryers are divided into two types: atmospheric dryers and vacuum dryers. Operating under vacuum can reduce the partial pressure of wet vapor in the space and accelerate the drying process. It can also reduce the boiling point of wet vapor and the drying temperature of materials, making steam less likely to leak out. Therefore, vacuum dryers are suitable for drying heat-sensitive, oxidizable, explosive, and toxic materials, as well as situations where wet vapor needs to be recycled.
        Advantages: 1. Well designed adsorption tower body
                             2. High performance Activated alumina adsorbent
                             3. A good muffler
                             4. Imported pneumatic controller with unique characteristics of high power and durability
                             5. Regenerative gas regulating valve with precise flow regulation

        According to the heating method, dryers are divided into convection type, conduction type, radiation type, dielectric type, and other types. Convection dryer, also known as direct dryer, uses hot drying media to directly contact wet materials, transfer heat through convection, and take away the generated steam; Conductive dryer, also known as indirect dryer, uses a conduction method to transfer heat from a heat source to a wet material through a metal partition wall. The generated wet vapor can be removed by methods such as vacuum suction, introducing a small amount of purge gas, or condensing on the surface of a separately set low-temperature condenser. This type of dryer does not use drying media, has high thermal efficiency, and the product is not contaminated. However, the drying capacity is limited by the heat transfer area of the metal wall, and the structure is also complex, often operating under vacuum; Radiation dryer uses various radiators to emit electromagnetic waves with a certain wavelength range, which are selectively absorbed by the surface of wet materials and converted into heat for drying; A dielectric dryer uses a high-frequency electric field to cause thermal effects inside wet materials for drying.
        Advantages: 1. Adopting high-performance evaporator with large heat exchange area, small heat transfer temperature difference, and more stable outlet air temperature of the evaporator
                             2. Adopting an efficient gas water separation structure, the oil water separation efficiency is high;

        According to the motion mode of wet materials, dryers can be divided into fixed bed type, stirred type, spray type and combined type; According to the structure, dryers can be divided into box dryers, conveyor dryers, drum dryers, vertical dryers, mechanical mixing dryers, rotary dryers, fluidized bed dryers, air flow dryers, vibration dryers, spray dryers and combination dryers.

        General knowledge of drying equipment: common pre dryers in China are spray dryers, air dryers, fluidized bed dryers, flash dryers, fluidized bed dryers, such as spray granulation. Flash dryer spray drying spray drying is one of the most advanced drying equipment. There are three traditional methods of atomization: rotary atomization, pressure atomization, and airflow atomization. Rotary atomization features a large drying capacity of spray (spray volume can reach 200 tons/hour), which will be responsible for easy control, flexible operation, and wider application. The feature of pressure atomization spray drying is that coarse particles can be created for future maintenance. Due to the small size of the nozzle hole, it is easy to block, and the liquid must be strictly filtered. The nozzle hole is prone to wear and tear, and the use of wear-resistant materials. There is also a new structure for nozzle pressure, called a pressure flow nozzle. Its characteristic is nozzle pressure and the surrounding air gap nozzle. Atomization is divided into two stages: the first is to form a liquid film pressure nozzle, and the second is to atomize the air, thereby giving the advantage of more small water droplets.

        This type of nozzle: (1) Adjusting the pressure of compressed air can adjust the diameter of droplets, making the operation simple;
                                        (2) Production, high viscosity liquid, it can atomize droplets fine; If you disable compressed air, the original pressure type nozzle can be used. The laboratory of atomized airflow and the main plants in the Middle East consume electricity. For the first two liquids that cannot be atomized by nozzles, use an air atomizable nozzle. High viscosity adhesive, adhesive, and filter cake materials can be used for three fluid nozzle atomization. The relatively dry air flow drying technology is mature, and if the operational data can be directly designed. www.jiashengsz.com
        Currently, there are a large number of drying equipment manufacturers capable of providing this type of equipment.

        Fluidized bed dryer Fluidized bed dryer spray dryer. The feeding setup is divided into a partial fluidized bed dryer mixer and a heat transfer fluidized bed dryer. When the unity is easy to use in fluidized bed drying, or when more water from the aggregated powder material feed will flow into the difficult phenomenon mentioned above, the feed mixer is established to eliminate the clustering problem and achieve normal flow. The latter is a combination of heat conduction and convective heat transfer, and the normal flow of hot air during use is far from enough for countries to meet the required heat drying needs.Heat exchangers are set up to supply some or most of the heat, and those types of operations can greatly save energy. Various forms of heat exchangers are used, and fluidized bed drying is often used in combination drying.

        Implement the theory of ordinary vibrating fluidized bed, vibrating fluidized bed. There is a flowing vibration source that can be divided into two types: one is driven by a vibration motor, and the other is generated by a regular motor through an excitation box to make the spring vibrate. When vibrating, the size of the bed is better than the latter. In the process of fluidized bed spray granulation dryer, fluidization technology, atomization technology and drying are organically combined. It is a catapult that sprays atomized liquid into the fluidized bed of the seeds, so the seeds continue to grow and dry to reach the required scale outside of time. The small and large production capacity of this device can create large particles. The industrial application of this equipment has been increasing day by day.