| 摘要 |
1471404 Liquefying boil-off gas PETROCARBON DEVELOPMENTS Ltd 20 June 1974 [17 April 1973 27 July 1973] 18484/73 and 35796/73 Heading F4P Reliquefaction of boil-off gas 30 from tank 2 is effected by first combining the boil-off gas 30 with refrigerant 32 and then heating the combined refrigerant at 20, 18 before compression at 8, 10 and cooling at 8, the refrigerant being then divided into a first refrigerant loop wherein refrigerant 40 is expanded at turbine 12 before recycling via lines 42, 34, 36 for recompression, and a second refrigerant loop wherein refrigerant 44 is cooled and condensed at 20 by the cold produced by the work-expansion of the first refrigerant at 12 and is thereafter sub-cooled at 22 before expansion through valve 14 to separator 16 from which vapour 52 is recycled for recompression at 8, 10, the cold for sub-cooling the second refrigerant at 22 and thus providing the cold for producing reliquefied gas 48 for return to tank 2 being caused by evaporation in exchanger 22 of liquefied gas tapped off from line 48 via line 50. In a further embodiment (Fig. 2, not shown), a part of the refrigerant compressed at 8 is directed to turbine 6 to drive compressor 8, and exchangers 18, 20 are replaced by a single exchanger with the division into first and second loops occurring at an intermediate point in this exchanger. Instead of boil-off gas being combined into the refrigerant, it can be reliquefied by heat exchange with a closed refrigerant circuit comprising the two loops, the refrigerant being, for example, N 2 (Figs. 3, 4, not shown). |
