Process for recovering a solvent vapor

Claim 1

A process for recovering a solvent vapor from a mixture of the solvent vapor and air comprising a. passing a mixed gas taken from a storing vessel for a mixed gas of a solvent vapor and air through a compressor to compress the mixed gas to a low degree and introducing the lightly compressed mixed gas to a first absorption column, bringing the lightly compressed gas into vapor-liquid contact with a first absorbent to absorb and recover a greater part of the solvent vapor in said first absorption column, and b. introducing a gas coming out of the first absorption column to a second absorption column and bringing said gas into vapor-liquid contact with a second absorbent circulating while being cooled in said second absorption column; c. after saturation of the second absorbent, by the solvent vapor, stopping the flow of said mixed gas to a compressor and returning a gas coming out from said first absorption column to a vessel storing said mixed gas, and at the same time performing d. causing said compressor to act as a vacuum pump and forwarding a gas from the second absorption column into the first absorption column to reduce the pressure inside the second absorption column, evaporating and gasifying a solvent component absorbed in substantially saturated state in the second absorbent, which is thereby cooled to regenerate the second absorbent; e. subsequently introducing an evaporated and gasified gas consisting mainly of the solvent vapor to the first absorption column, bringing said gas into vapor-liquid contact with the first absorbent to absorb and recover the solvent vapor, returning a gas containing a trace of the solvent vapor, which has not been absorbed and recovered, to said mixed gas storing vessel or supplying a part of said gas to the second absorption column to exclude the solvent component in the second absorbent.