Patent ID: 6758060
Filing Date: 2004-07-06
Classification: F25J,Y10S

Abstract:
A process for removing nitrogen from a methane-containing feed gas during the production of a liquefied natural gas product using a two column cryogenic nitrogen rejection unit having a high pressure multistage distillation tower and a low pressure multistage distillation tower, the process comprising(a) separating the feed gas in the high pressure multistage distillation tower into a first methane-rich liquid bottoms stream containing a reduced nitrogen content and a first vaporous overhead stream, (b) at least partially condensing the first vaporous overhead stream into a liquid intermediate stream, (c) separating the liquid intermediate stream in the low pressure multistage distillation tower into a second methane rich liquid bottoms stream containing a reduced nitrogen content and a second vaporous overhead stream containing a substantial portion of the nitrogen in the feed gas and a substantially reduced methane content, and (d) recovering the first methane-rich liquid bottoms stream and the second methane-rich liquid bottoms stream as the liquid natural gas product.