Petrochemical barge tank residual vapors expelled with a scavenging gas for cryogenic recovery of vapors and return of scavenging nitrogen to tank

摘要

In a process to remove residual gas from a tank after discharge of the main e.g. petrochemical load, a scavenging gas is introduced to the tank and a mixture of scavenging gas and the residual gas are drawn off. The mixture is separated into a first residual gas fraction, and a second scavenging gas fraction which is then especially. returned to the tank (1). The mixture is separated into residual and scavenging fractions by condensation of the residual gas by a cryogenic fluid e.g. gaseous or liquid nitrogen. The scouring gas employed is air or nitrogen. In an alternative embodiment the mixed gas components are separated by adsorption or absorption of part of the residual gas, or by membrane separation.