Nitrogen management in an lng plant

Abstract

Electric, steam, or expansion driven compressors eliminate the ability to process feed gas with higher nitrogen content without a complex nitrogen rejection unit. An LNG slip stream from a high-stage (HS) flash drum vapor, subcooled high pressure LNG from methane economizer, or high pressure methane recycle stream is subcooled in a heat exchanger by low stage (LS) methane refrigerant. The subcooled slip stream is flashed to pressure higher than the LS flash drum pressure in a flash vessel. The vapor stream is recycled and is mixed with the vapor from LS flash drum. The high-nitrogen liquid stream from the side flash drum is sent to the LNG product. This process allows rejecting more light components including nitrogen to an LNG product eliminating the accumulation of light components in the system for the feed gas with high concentrations of light components.

Dependencies are inferred from the claim text.