Condensing solvent vapours from waste air - by cold washing on progressively reducing scale at reducing temps.

摘要

Before discharge into the atmos., gases charged with solvent vapour, e.g. waste air from an empty petrol tank, are purified to meet legal requirements by condensation in a series of stages, using a counterflowing washing liq. petrol cooled in an external system. Max. cooling is applied in the first stage to condense most of the susceptible components. At each successive stage the washing liq. is colder and supplied in decreasing amts. In parallel with the washing stages, the washing liq. is being cooled to the various desired temps. in interconnected heat exchangers, themselves cooled by a separate coolant supply system. A rectification column may divide used washing liq. into light components for removal, and liq. charged with the less volatile components for re-use as wash liq. ADVANTAGE - With reduced total cooling demand, less energy is needed to separate and recover solvent to necessary extent.