Thermal Desorption in Gas Phase

For the exhausted adsorbents from gas phase adsorption, regeneration by thermal desorption is most commonly used. For example, activated carbon used to prevent contamination of air by organic solvents of low concentrations, and silica gel, activated alumina or zeolite used for dehumidification of gases are regenerated by high temperature steam, air or inert gases. In the case of organic adsorbates 

For estimation of desorption curves from an exhausted adsorbent bed, the basic equations for mass and heat balances in an adiabatic column are as follows. 

When high temperature inert gas is introduced to the bed, the above set of equations must be solved simultaneously under a proper set of initial and boundary conditions and concentration and temperature profiles in the effluent stream can be readily obtained. 

Analogous to adsorption in a column with nonisothermal conditions, the thermal front formed by a high temperature inlet stream moves through the column and changes the equilibrium relation at and after the front. Velocity of the thermal front is described by neglecting consumption of heat due to desorption heat as 

Velocity of desorption wave, Vo, is also determined by the ratio of the amount adsorbed, q, to the concentration, C, in equilibrium with q at temperature, T. 

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