Low temperature drying using liquid desiccants

Abstract

In the past decade, due to the increased cost of energy, lowtemperature drying systems using liquid desiccants have received great attention.

The basic concept of a desiccant dehumidification system is to directly reduce the moisture and warm up the air that will be used for different drying operations. Many operations such as drying of agricultural products and forest products require low temperature drying to minimize damage to the product due to thermal stresses.

In the present work, heat and mass transfer analysis in an air-desiccant dehumidification contact system (packed tower) has been studied employing liquid desiccants, namely calcium chloride (CaClj) and lithium chloride ( L1C1 ). Plastic one-inch Rasching Rings are used as the packing material. A simulation method has been applied to determine the performance of the tower. All the parameters affecting the tower performance, such as liquid concentration and temperature, air temperature and humidity, height of packing materials, and flow rates of air and liquids, have been discussed. The best operating point of the tower was found by optimizing all the above parameters.

For this study, each desiccant demonstrated Its ability to absorb the moisture from air as it passes through the tower and comes in contact with the moist air. Also, each desiccant solution had an optimum performance point for concentration and temperature. Lithium chloride consistently yielded better results than both calcium chloride and the mixture, and was more predictable In each performance characteristic.