Patent ID: 7833317
Filing Date: 2010-11-16
Classification: F17C

Abstract:
1. A system for control of emission of volatile gases from a holding tank for crude oil during unloading, loading and transport/holding of the oil, wherein a blanket gas is used to regulate a pressure and amount of combustible gas and to prevent ingress of oxygen in the holding tank for crude oil, the system comprising: a recovery device configured to wash/clean, compress and condense hydrocarbon gas from the holding tank for crude oil, thereby producing recovered liquid hydrocarbons, a storage tank configured to receive the recovered liquid hydrocarbons from the recovery device and to store the recovered liquid hydrocarbons under pressure, wherein the storage tank is arranged to also function as a separator, wherein liquid and gas are separated and any excess gas is vented out of the tank, and an evaporation device configured to receive the recovered liquid hydrocarbons from the storage tank and to convert the recovered liquid hydrocarbons to gas form, whereby the hydrocarbon gas is used as the blanket gas in the holding tank for crude oil, wherein the excess gas from the storage tanks is led to a membrane separator where heaviest components in the excess gas are concentrated in a product flow which is re-circulated to an inlet side of the compressor, and wherein remaining excess gas is vented out through a regulating valve, and wherein the regulating valve is arranged to function as a pressure control valve which determines a storage pressure, condensation pressure, membrane pressure and outlet pressure of the compressor.