Process for purifying liquid natural gas

A process for increasing the methane content of liquid natural gas to provide a substantially pure liquid methane product comprising:

• (a) introducing a liquid natural gas stream into a first heat exchanger in indirect heat exchange with a purified methane vapor stream so as to liquefy said purified methane vapor stream to provide a substantially pure liquid methane product and to partially vaporize said liquid natureal gas stream to provide a mixture of a major amount of substantially pure methane vapor and a minor amount of liquid containing methane and higher molecular weight hydrocarbons;
• (b) transferring said mixture of vapor and liquid from said first heat exchanger to a low pressure separator to provide a liquid bottom fraction and a substantially pure methane top vapor fraction;
• (c) introducing at least a portion of said liquid bottom fraction and all of said vapor fraction into a second heat exchanger in indirect heat exchange with said vapor fraction after said vapor fraction has been processed in accordance with step (d);
• (d) transferring said vapor fraction exiting from said second heat exchanger through a compressor and an aftercooler to provide the said processed top vapor fraction for use as a heat exchange medium in said second heat exchanger;
• and
• (e) introducing said processed top vapor fraction exiting from said second heat exchanger into said first heat exchanger to provide a heat exchange medium for said partial vaporization of said liquid natural gas and to provide said substantially pure liquid methane stream.