Natural gas liquefaction nroj tsuag (LNG) ua raws li cov kev cai ntawm kev hloov pauv ntawm cov thermodynamic theem. Thaum qhov kub thiab txias qis dua qhov tseem ceeb (methane: -82.6 degree), kev hloov pauv ntawm cov pa roj mus rau theem ua kua tuaj yeem ua tiav los ntawm kev siv zog los yog txias. Ntawm atmospheric siab, txias mus rau -162℃yog yuav tsum tau rau liquefaction, thaum lub siab ntawm 4.5 MPa, txias rau -84℃tsuas yog txaus. Cov txheej txheem no yuav tsum tau kov yeej lub zog kinetic ntawm cov roj molecules, ua tiav qhov txo qis hauv lub zog sab hauv los ntawm kev ua haujlwm compressor thiab hloov cov cua sov hauv cov khoom siv hluav taws xob.
Mixed Refrigerant Process: Cov txheej txheem no siv cov kua ua haujlwm sib xyaw ntawm nitrogen, methane, thiab ethane kom ua tiav qhov kub ntawm -160℃los ntawm ib theem compression. Cov cuab yeej siv peev raug txo los ntawm 30%, tab sis kev siv hluav taws xob nce 20%.
Cascaded Refrigeration Process: Cov txheej txheem no siv peb theem ntawm kev ua kom txias nrog propane (-40 degree), ethylene (-100 degree), thiab methane (-160 degree) rau kev txo qis qis. Nws muaj qhov tsawg tshaj plaws kev siv zog tab sis cov cuab yeej siv siab tshaj plaws.
Expansion Refrigeration Process: Cov txheej txheem no yog tsim rau me me -scale nroj tsuag. Natural gas yog nthuav los ntawm lub turbine mus rau qhov siab ntawm 0.1-1 MPa, siv nws tus kheej siab poob los ua kom txias. Kev siv hluav taws xob yog 35% siab dua li cov txheej txheem sib xyaw ua ke.
