GB1078341A - Mobile gas liquefaction platform - Google Patents

Abstract

1,078,341. Gas liquefaction plant. HYDROCARBON RESEARCH Inc. Nov. 23, 1964, No. 47593/64. Heading F4P. A mobile methane liquefaction plant comprises a plurality of heat exchangers 44, 54, 55, 56, 66, 68 in series cooled by a multiple stage cascade refrigeration system including compressors 122, 112, 106 and a cooler 128. In operation feed gas from a fixed supply, e.g. a well in the sea bed, having been cleaned in a caustic washer 42, cooled in exchanger 44 traversed by liquid propane, freed of moisture in a separator 46 and in a drier 48 is cooled at 52 in heat exchange with cold overhead gaseous nitrogen and methane from a stripper column 74 at 54, 55, in heat exchange with high pressure liquid propane, at 56 with liquid ethane after which high boiling components are separated at 60 and the remaining gas is liqufied in ethane and methane-cooled exchangers 66, 68 and expanded at 70 into the stripper column 74 from which product liquid methane is withdrawn at 76 and is sub-cooled in liquid methane and liquid nitrogen-cooled exchangers 80, 82. Liquid propane for cooling exchanger 44 is forced from an accumulator 100 through an expansion valve 102 and the propane vapour leaving exchanger 44 together with a portion of liquid propane leaving accumulator 100 is flashed into a first drum 103. Vapour therefrom passes along a line 104 to the inlet of a third stage compressor 106 which delivers through a sea water-cooled exchanger 128 to the accumulator 100. Liquid propane from the base of drum 103 is expanded at 109 into exchanger 54 and the resulting propane vapour together with a portion of liquid propane from drum 103 is flashed into a second drum 110. Propane gas from the latter passes along a line 114 to the inlet of a second stage compressor 112 whilst liquid propane from drum 110 traverses heat exchanger 55 and the resulting vapour passes along a line 119 and through a surge drum 120 to the inlet of a first stage compressor 122. The ethane and methane circuits for cooling exchangers 56, 66 and 68, 70 respectively are similar to the propane circuit. The plant is assembled on a raft which is towed to the site and has telescopic legs by which it rests on the sea bed.