Solvent recovery adsorption process - having clean gas or air purge after steaming out bed

摘要

Regeneration of active carbon charged with organic solvent uses steam in counterflow to the previous loading flow. Following this, air or purified gas is fed through the bed in such quantity that during the subsequent loading or drying phase practically no breakthrough of solvent occurs. The gas-vapour mixt. produced by this additional purging with air or gas is fed back into the solvent laden gas stream. Quantities to be used per tonne of activated carbon are 20-500 m3 (pref. 50 to 200 m3) of air or gas. The gas-vapour mixt. to be added to the solvent laden gas is first cooled, this can be done in the desorbate condenser. The mixt. can be injected before the solvent laden gas fan. System is useful for solvent recovery systems. The problem with these is that when a bed is returned to load after desorption there is always some residual organic material present. This can be discharged to atmosphere by the incoming gas or air stream. Where this is undesirable, it can be reduced by prolonged steaming which is expensive and requires extra cooling. The system claimed avoids this problem and ensures that any such material is retained on the other bed.