When very low dew points are required, solid bed dehydration becomes the ogical choice. It is based on fixed-bed adsorption of water vapor by a elected desiccant. The system may consist of two-bed, three-bed or multi-bed operations. In three-bed operation, if two beds are loading at different tages, the third one would be regenerated. The feed gas in entering the bed form the top and the upper zone becomes saturated first. The second zone is mass transfer zone and is being loaded. The third zone is still not used and active. While the bed is in operation the outlet concentration has very low ater concentration and the mass transfer zone moves downward. At a certain point the outlet water content rises to the point that is equivalent to the initial wet gas content as if bed is not present. Thus, the beginning of this period is called the breakthrough period. Closing valve after the bed has been used and loaded with water, then it is regenerated by hot gas and inally, cooled by switching to cold gas. The appropriate temperature for inlet gas during heating and cooling off the bed is needed to desorb water, nd then for cooling off the bed it is essential to prepare it for the next ycle and then the outlet gas temperature is used to repeat the process in the same period.

Application
- Dehydration of natural gas
- Hexane purification unit
- NGL and LPG sweetening unit