Process and apparatus for treating lean LNG

A process for treating lean LNG for obtaining, from lean LNG enriched in methane or enriched in methane and ethane as compared with raw material LNG, a product gas and a product LNG having a pressure P1 close to the atmospheric pressure, comprising:

• a) branching the lean LNG to obtain lean LNG for product gas and lean LNG for product LNG;
• b) cooling the lean LNG for product LNG in a cooler using a refrigerant;
• c) branching a liquid flow derived from the lean LNG for product LNG having been cooled in the step b to obtain refrigerant LNG to be used as the refrigerant, and remaining LNG corresponding to a balance;
• d) subjecting the remaining LNG to pressure reduction and gas-liquid separation to obtain a gas phase flow having the pressure P1 and a liquid phase flow having the pressure P1 as the product LNG;
• e) subjecting the refrigerant LNG to pressure reduction;
• f) using a flow from the step e as the refrigerant of the cooler;
• g) joining, before or after the step f, the gas phase flow having the pressure P1 to the flow from the step e;
• h) subjecting a flow resulting from the step f and the step g to pressure increase and cooling through heat exchange with the lean LNG for product gas to liquefy the flow resulting from the step f and the step g;
• i) subjecting the lean LNG for product gas before being used for the heat exchange of the step h to pressure increase;
• j) regasifying the lean LNG for product gas after the step h and the step i to obtain the product gas;
• and
• k) joining the flow having been liquefied in the step h to the lean LNG for product LNG obtained in the step a.