Industrial process solvents are recovered by a variety of unit operations. Solvents in an air stream at low concentrations (10-30% LEL) are usually recovered via fixed carbon bed adsorption [I-31. In fixed bed operations, after a carbon bed has adsorbed a working charge of solvent, the solvent is removed and collected so that the carbon can be reused. Multiple adsorbers are used in parallel to facilitate the regeneration process since a regenerating carbon bed is isolated from the solvent laden air (SLA).Adsorbed solvent is usually removed from a carbon bed by using a steam purge to raise the temperature of the bed. As the temperature increases, the solvent load on the carhon decreases, and the desorbed solvent is carried out of the carbon bed by uncondensed steam. After the working 12. J ; l c o l r , t ' . ; r n d D. Tondetir, "N(~nis(1tlrer1n~11 G a s Adsorption i n Fixed R e d s , I . A. Simplistic Linearized E <~~i i l i l >~-i u n i M~, c l e l , " Clwni. Etigr-. J 22, 1x7-202 (l9Xl). Liai>is, A. I. hncl 0. K. Crosber, " C o n i p a i -i h o n c,t'Model Prediction, with N~~~l i~~) t l l~~r~~l~l l Sorptic,n Dkda ti,,-Eth~ule-C;,rl,,,,, Dioxide Mixtiires in I3ecls of 5 A Molect~lal-Sieves," Chr,ti. E n g r . S c i . :37, 958-961 [ 1982).
