Dual mode Liquefied Natural Gas (LNG) liquefier

A dual mode natural gas liquefier configured to operate in a first mode and a second mode, the dual mode natural gas liquefier comprising:

• a heat exchanger having a plurality of cooling passages and a plurality of warming passages;
• a natural gas inlet disposed on the heat exchanger and configured to receive a gaseous natural gas feed and distribute the natural gas through a plurality of cooling passages;
• a natural gas outlet disposed on the heat exchanger and configured to discharge the liquefied natural gas from the heat exchanger;
• a liquid nitrogen inlet disposed on the heat exchanger and configured to receive a liquid nitrogen feed and distribute the liquid nitrogen through a plurality of warming passages;
• a gaseous nitrogen outlet disposed on the heat exchanger and configured to discharge the vaporized nitrogen from the heat exchanger;
• wherein the heat exchanger is configured to liquefy the gaseous natural gas traversing the cooling passages via indirect heat exchange with nitrogen traversing the warming passages;
• an intermediate outlet disposed on the heat exchanger and coupled to one or more of the plurality of warming passages and configured to divert a gaseous nitrogen stream passing through the one or more of the plurality of warming passages;
• a first intermediate inlet disposed on the heat exchanger and configured to receive the diverted gaseous nitrogen stream when operating in the first mode and;
• a turbine configured to expand the diverted gaseous nitrogen stream when the dual mode natural gas liquefier is operating in the second mode and produce a turbine exhaust stream that is at a temperature that is less than the temperature of the diverted gaseous nitrogen stream;
• a second intermediate inlet disposed on the heat exchanger and configured to receive the turbine exhaust when the dual mode natural gas liquefier is operating in the second mode and configured to be blocked by one or more blind flanges when the dual mode natural gas liquefier is operating in the second mode;
• wherein when the dual mode natural gas liquefier is configured to operate in the first mode, the intermediate outlet is in fluid communication with the first intermediate inlet and the diverted gaseous nitrogen stream is reintroduced to warming passages within the heat exchanger via the first intermediate inlet with the reintroduced nitrogen stream at a temperature that is equal to or greater than the temperature of the diverted gaseous nitrogen stream;
• and
• wherein when the dual mode natural gas liquefier is configured to operate in the second mode, the turbine exhaust stream is reintroduced to warming passages within the heat exchanger.