Plant for the liquefaction of nitrogen using the recovery of the frigories derived from the evaporation of liquefied natural gas

摘要

Procedure for the liquefaction of nitrogen using the recovery of the frigories derived from the evaporation of liquefied natural gas comprising the following steps: sending a flow of nitrogen gas to a first (115) and a second (117) stage of the recirculation compressor of high pressure; sending the flow (120) of nitrogen leaving said second stage (117) of the compressor to a liquefaction heat exchanger (121); sending to said liquefaction heat exchanger (121) a flow (123) of liquefied natural gas, countercurrent with respect to the flow (120) of nitrogen exiting said compressor; sending a portion (130) of the flow (126) of liquid nitrogen leaving said liquefaction heat exchanger (121) to an expander (131); sending the flow of nitrogen exiting said expander (131) to a medium pressure separator (112) which supplies an outlet flow (132) of liquefied nitrogen; characterized in that the flow of nitrogen (100) to be liquefied is sent to a precooler (101); the flow (102) exiting said pre-cooler (101) is sent to a manifold (106) which supplies the flow (107) of nitrogen gas that is sent to the first (115) and second (117) stages of the compressor; wherein sending the flow (107) of nitrogen gas to the first (115) and second (117) stages of the compressor comprises: sending the flow (107) of nitrogen gas to a heat exchanger (108) of the recirculation compressor of high pressure; sending the flow (110) of nitrogen exiting said heat exchanger (108) of the high pressure recirculation compressor to the first stage (115) of the high pressure recirculation compressor; the compressed flow (116) leaving said first stage (115) is sent to the heat exchanger (108) of the high pressure recirculation compressor and the flow leaving this heat exchanger (108) is sent to the second stage ( 117) of the high pressure recirculation compressor (117) at -150 ° C; and in that the remaining part (150) of the liquid nitrogen stream (126) exiting said liquefaction heat exchanger (121) is first sent to said heat exchanger (108) of the high pressure recirculation compressor to countercurrent with respect to said flow (107) of nitrogen gas and said compressed flow (116) of nitrogen leaving said first stage (115) of the compressor; then (152) to said precooler (101) countercurrent with respect to said flow (100) of nitrogen to be liquefied and then to a turbine (104); sending the flow (103) leaving said turbine (104) to said collector (106) combining the flow leaving the turbine (104) and the flow (102) leaving the precooler (101) to produce said flow ( 107) of nitrogen sent to the first (115) and second (117) compressor stages.