Plant for the liquefaction of nitrogen using the recovery of cold energy deriving from the evaporation of liquefied natural gas

A method for the liquefaction of nitrogen using the recovery of cold energy deriving from the evaporation of liquefied natural gas comprising the steps of:

• sending a flow of nitrogen (100) to be liquefied to a precooler (101);
• a flow (102) exiting from the precooler (101) is sent to a collector (106) that delivers the flow (107) of nitrogen gas;
• sending the flow (107) of nitrogen gas exiting the precooler (101) to a first heat exchanger (108) of a first pressure recirculation compressor;
• sending the flow (114) of nitrogen exiting the first heat exchanger (108) to a first stage (115) of the first pressure recirculation compressor;
• sending a compressed flow (116) exiting the first stage (115) to the first heat exchanger (108) and sending the compressed flow exiting the first heat exchanger (108) to a second stage (117) of the first pressure recirculation compressor at the lowest temperature possible of −150° C.;
• sending the flow (120) of nitrogen exiting the first pressure recirculation compressor to a second heat exchanger (121);
• sending to the second heat exchanger (121) a flow (123) of liquified natural gas, countercurrent to the flow (120) of nitrogen exiting the first pressure recirculation compressor (115);
• sending a first portion (150) of the flow (126) of liquid nitrogen exiting the second heat exchanger (121) first to the first heat exchanger (108) countercurrent to the flow (107) of nitrogen gas and to the compressed flow (116) of nitrogen;
• and then sending a second portion of the flow (152) of the flow (126) of liquid nitrogen to the precooler (101) countercurrent to the flow of nitrogen (100) to be liquefied;
• sending the second portion of the flow (155) exiting from the precooler (101) to a turbine (104);
• sending the flow (103) exiting from the turbine (104) to the collector (106);
• sending a third portion (130) of the flow (126) of liquid nitrogen exiting the second heat exchanger (121) to an expander (131);
• and sending the flow of nitrogen exiting the expander (131) to a second pressure separator (112) that delivers an exiting flow (132) of liquified nitrogen.