Natural gas liquefaction with controlled b.t.u. content

Abstract

Abstract 1,141,219. Cold separation of gas mixtures. CONCH INTERNATIONAL METHANE Ltd. 8 Aug., 1967 [17 Aug., 1966], No. 36252/67. Heading F4P. Natural hydrocarbon gas is supplied to a distribution system at a controlled B.T.U. value by liquefying a feed stream 2 at a pressure higher than the distribution pressure in indirect heat exchangers 5, 6, 7 cooled by an external refrigerant, diverting through a line 23 a minor portion of the high pressure L.N.G. leaving exchanger 7, expanding it at a valve 24 into a vessel 27 to produce flash gas and liquid heavy hydrocarbons, expanding at valves 42, 46, 51 the remainder of the L.N.G. into a storage vessel 52 maintained at about atmospheric pressure expanding at a valve 31 the hydrocarbon liquid withdrawn from vessel 27 and adding it to boil-off gas withdrawn by a pump 53 from vessel 52 at a rate controlled by a calorimeter 34a and passing the mixture so formed through a line 47a and a compressor 48 to an outlet line 33 leading to the distribution system. L.N.G. leaving expansion valve 42 is joined by flash gas from chamber 27 and is further cooled in an exchanger 21 traversed by a reverse flow of said boil-off gas and heavy hydrocarbon liquid and also by a reverse flow of a minor portion of L.N.G. withdrawn from the outlet line of exchanger 21 and expanded at a valve 43. The main body of L.N.G. is still further cooled in an exchanger 10 traversed by a reverse flow of a minor portion of L.N.G. leaving expansion valve 46. The two reverse flows of expanded L.N.G. are warmed in exchangers 5, 6, 7 and are fed to the outlet line 33. The external refrigerant for cooling exchanger 5, 6, 7 is circulated in a closed cycle comprising a surge tank 9, expansion valves 11, 21, 22 in series and a three stage compressor to which refrigerant vapour leaving exchangers 5, 6, 7 is fed and which delivers to the tank 9. A portion of liquid refrigerant is withdrawn from exchanger 6 and is used to heat a coil 36 in flash vessel 27; the so-cooled refrigerant being returned to exchanger 7.

Inventors

• 👤 Charles O Huntress
• 👤 Jr Russell C Proctor

Bibliographic Details