EXPERIMENTAL STUDY ON SORPTION BEHAVIOR OF DESICCANTS.

Abstract

Moisture removal from air is a practice that is beneficial to many applications. One of the methods to separate water vapor from air is by using desiccants. Present work depicts water vapor sorption behavior of CaCl 2 , Silica gel, Molecular sieve, Bentonite powder and Aluminum oxide desiccants. In comparison to open air conditions, superior water vapor sorption was exhibited by all the desiccants in closed glass casings containing water, due to availability of higher humidity. After 141 hours of absorption time, CaCl 2 absorbed 36.2% of its weight in open air conditions and 43.1% due to availability of higher humidity in closed glass casings having water. In comparatively lower humidity conditions prevailing in open air conditions, Molecular sieve exhibited superior adsorption capability than Silica gel while inside closed glass casings, Silica gel overpowered Molecular sieve during the later half of adsorption process. Regeneration experiments for desiccants showed that 100% regeneration of Silica gel and CaCl 2 could be obtained when heated to around 117.5C and 134C respectively for 5 hours. LiCl and Molecular sieve indicated 70.6% and 59.7% regeneration respectively when heated to 140°C. Introduction:-Separation of moisture from air is a practice that is being used in many applications for achieving the desirable benefits. Some of the applications where practice of moisture removal from air is followed are in chemical industry to remove water produced by chemical reactions, air dehumidification air-conditioning system for comfortable and healthy environment 1, 2, humidity control and air drying for industrial and agricultural sector like textile mills, post-harvest crop storage etc. 3, extracting water from air 4, control of humidity in food packaging 5, Moisture control in pharmaceutical 6 and electronics industry 7. One of the methods to separate moisture from air is by using materials having affinity to attract water vapor and retain it in the form of water. Some of the commonly occurring materials that have the property to attract moisture from air are clay, sand, wood, sugar, caramel, honey, glycerol, table salts, polymers material such as cellulose, nylon etc. Commercially available materials having the property to attract water vapor from air are known as desiccants and the mechanism by which these materials attract and hold water vapor is adsorption or absorptions 8, 9. Some of the desiccants are Calcium Chloride, Lithium Chloride, Lithium Bromide, Triethylene Glycol, Silica Gel, Aluminum silicates (Molecular sieve or Zeolites), Aluminum oxides, etc. These desiccants have been reported in many research works for sorption of water vapor molecules from air. As energy saving alternative Lithium chloride