Five industrial dryers were introduced in previous post. Here are five other industrial dryers including cabinet vacuum dryer, fluidized-bed dryer, spray dryer, freeze dryer, and ultrasonic dryer. Some dryers can use mixed technics to improve the performance e.g. ultrasonic drying technic in vacuum conditions or different dryer energy sources to increase performance.
Cabinet vacuum dryer
The pressure inside the cabinet vacuum container reduces by a vacuum pump. The vacuum pump moves air from inside the cabinet to the compressor, and the separated moisture from the products in the condenser is cooled and removed from the food. In addition, the process is performed at a lower temperature than conventional cabinet dryers that operate at atmospheric pressure. Lower temperature equals to higher quality of the product.
Fluidized-bed dryer
Fluidized-bed dryer is used for granules. The hot air is blown from the bottom of the bed. The granule is dried after moisture evaporation and exit from another side of bed and the hot air exist from the top of bed.
Spray dryer
The spray dryer is proper to produce the powder foodstuffs. For example, it is used to change liquid milk to milk powder. In this way, the spraying liquid foodstuff enters the nozzle from the top of the container. Simultaneously the hot air enters from the side valve. The circulation of the hot air and contact with the liquid removes the moisture of the food. The separated moisture drops to the bottom of the container and the powders are collected. Furthermore, the hot output air, cooled by contacting the cold liquid, exits from the exiting valve at the bottom of the dryer. This dryer has a continuous process.
Freeze dryer
The freeze dryer has a container at low pressure and surfaces that transfer the heat inside it. The frozen foodstuffs previously are put on these surfaces. The existed moisture in the food directly changes from solid to vapor, instead of liquefaction (sublimation). The high-quality is preserved because the temperature is low. The freeze-drying process is bath and semi-batch.
Ultrasonic dryer
Using hot air in the common tunnel dryers usually damages the foodstuffs tissues and can reduce vitamins, minerals, color, and quality of them. However, this probability is low in ultrasonic technic because the low temperature is used. Ultrasonic waves are used in this dryer to separate the existed moistures in the tissues by ultrasonic wave producer resource and its transfer to the foods as well as the vacuum ultrasonic dryer which also uses the vacuum gages and condenser to separate the moisture and remain the dried foods inside the dryer. Moreover, the microbial load can be also reduced by this technic.
