At present, the common types of dryers in my country include spray dryers, airflow dryers, fluidized bed dryers, fluidized bed spray granulation dryers, etc.
Spray Dryer Spray drying is one of the fastest growing equipment in drying equipment. There are three conventional atomization methods: rotary atomization, pressure atomization and airflow atomization.
Rotary atomization spray drying is characterized by large production capacity of a single machine (spray volume can reach 200t/h), easy control of feed volume, large operating flexibility, and wide application.
The characteristic of spray drying with pressure atomizer is that it can produce coarse particles and is easy to maintain. Since the nozzle hole is small and easy to block, the feed liquid must be strictly filtered.
The nozzle hole is easy to wear and must be made of wear-resistant materials. There is also a new structure of the pressure nozzle, which is called the pressure-air flow nozzle. It is characterized by a pressure nozzle in the center and an airflow nozzle in the surrounding environment gap.
The atomization is divided into two stages: the pressure nozzle first forms a liquid film, and the liquid film is atomized by the air flow for the second time to make the droplets finer. The advantages of this type of nozzle are: (1) Adjust the pressure of the compressed air to adjust the droplet diameter, which is easy to operate; (2) Large output and high viscosity liquid can also be atomized into fine droplets; 3 If the compressed air is deactivated, the original pressure nozzle can also be used.
The airflow atomizer is mainly used in laboratories and intermediate factories, and its power consumption is large.
The material liquid that cannot be atomized by the first two atomizers may be atomized by the air-flow atomizer. High-viscosity paste, paste and filter cake materials can be atomized with a three-fluid nozzle.
Airflow Dryer Airflow drying technology is mature, if there is operating data, it can be designed directly.
At present, there are many drying equipment manufacturers that can provide this type of equipment.
Fluidized bed dryer Fluidized bed dryer is second only to spray dryer. It is divided into a fluidized bed dryer with a stirrer at the feeding part and a fluidized bed dryer with internal heat exchange.
When using a fluidized bed to dry powder and granular materials that are prone to agglomeration or agglomeration, fluidization difficulties will occur in the feeding section with relatively large moisture. At this time, a stirrer is installed in the feeding section to eliminate the problem of agglomeration and achieve normal flow. change. The latter is a combination of conduction heat transfer and convective heat transfer. When the amount of hot air used in the normal fluidized state is far from meeting the heat required for drying, an internal heat exchanger is used to supply part or most of the heat. This mode of operation can significantly save energy. There are many types of internal heat exchangers.
Fluidized beds are also frequently used in combination drying second and third stage dryers.
Vibration is applied to an ordinary fluidized bed, which is called a vibrating fluidized bed. Vibration fluidization can be divided into two types from the source of vibration: one is driven by a vibration motor; the other is an ordinary motor that vibrates the spring through the vibration box.
The latter works better when the size of the vibrating fluidized bed is large.
Fluidized bed spray granulation dryer This process is an organic combination of fluidization technology, atomization technology and drying technology. It sprays the atomized material liquid onto the fluidized seed crystal bed, so that the seed crystal grows and dries continuously, and is discharged out of the device when it grows to a specified size.
The equipment is small in size, large in production capacity, and can produce large particles. The industrial applications of this equipment have been increasing day by day.