| 摘要 |
Natural gas is liquefied at a production site by compression 10, cooling in an after-cooler 12, after first mixing with it a refrigerant. The condensed refrigerant is separated from the compressed gas in a separator 14, flashed through an expansion valve 16 and used to cool the natural gas further. To liquefy the now compressed natural gas, it is passed through heat exchangers 18, 22, where it is cooled by the refrigerant, such as liquid nitrogen, or a cooled refrigerant gas of a reverse Brayton cycle refrigeration circuit. At a market site (Fig 2), the liquid natural gas can be used to produce liquid nitrogen which is returned to the production site using the same insulated containers as used for transporting the liquid natural gas from the production site to the market site. The liquid nitrogen is produced at the market site by using natural gas to fuel an engine (60 Fig 2) that powers a compressor (68, 70, Fig 2)acting to compress the exhaust gases of the engine before they are cooled by the liquid natural gas. Water and carbon dioxide condense at different stages of the cooling process and are removed. |
