The Adiabatic Fixed Bed Absorber

The operation mode of fixed bed adsorbers can be isothermal (very small adsorptive concentration in the fluid and low heats of adsorption), nonisothermal, and adiabatic. The heat loss of large industrial adsorbers is often so small in comparison to the heat production by adsorption that the bed is nearly operated adiabatically. In such a case not only the mass balances but also the ener balances have to be taken into accoimt to get information on the operating mode and the fields of concentration and temperature in a fixed bed. These balances for the adsorbent (Index S = solid) and the fluid (Index G) are 

If the Biot number Bi = a- d /(6 - Ig) 1 the differences of the local temperature in a particle with the diameter are small. Then the mean heat transfer coefficient 

5-9 Schematic illustration of the temperature and concentration break through curve for the case of a preceding temperature front 

In Fig. 9.5-9 it is assumed that the temperature front (Wjj the velocity of the temperature transfer zone ) is moving with a higher speed than the ( mass transfer Zone or the breakthrough curve. In the left figure the courses of the fluid load- 

In Fig. 9.5-10 the case is shown that both fronts are moving through the bed with the same velocity. According to Pan and Basmadjian (Pan and Basmadjian 1970) the temperature front moves faster than the breakthrough curve if 

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