TH39089A - The process of liquefying a stream containing a large amount of methane. - Google Patents

Abstract

DC60 The liquefaction of a methane-rich gas stream involves a) feeding a stream of natural gas (1) into the wash tower (5), separating heavy hydrocarbons from the natural gas stream (1) in the wash tower (5) to obtain an overhead stream (8) drawn out from the top of the wash tower (5), partially condensing the overhead stream and separating it from the condensate stream (91), which is returned to the top of the wash tower (5) as a reflux; b) liquefying the methane-rich gas stream in tubes (15) arranged in the main heat exchanger (17) by indirect heat exchange with the evaporated multicomponent refrigerant at low refrigerant pressure; and c) compressing the multicomponent refrigerant drawn out from the shell side (19) of the main heat exchanger (15) and partially condensing it at high refrigerant pressure in tubes (38) arranged in the auxiliary heat exchanger (35) by indirect heat exchange with the refrigerant. The liquefaction of the methane-rich multicomponent refrigerant is achieved by: a) feeding the natural gas stream (1) into the wash tower (5); separating the heavy hydrocarbons from the natural gas stream (1) in the wash tower (5) to obtain the top outlet stream (8) which is then partially condensed in tubes (83) arranged in the auxiliary heat exchanger (35); b) liquefying the methane-rich multicomponent refrigerant in tubes (15) arranged in the main heat exchanger (17) by indirect heat exchange with the liquefied multicomponent refrigerant used in step b) compressing the refrigerant. The multicomponent refrigerant is drawn out from the shell side (19) of the primary heat exchanger (15) and partially condensed at high refrigerant pressure in tubes (38) arranged in the auxiliary heat exchanger (35) by indirect heat exchange with the auxiliary multicomponent refrigerant which evaporates at low auxiliary refrigerant pressure to obtain the multicomponent refrigerant for use in step b), which causes the gas stream exiting from the top to be partially condensed in tubes (83) arranged in the auxiliary heat exchanger (35).

Claims (4)

1. The method for liquefying a methane-rich stream consists of the following steps: a) Feeding a high-pressure natural gas stream into a sub-column. Heavy hydrocarbons are separated from the natural gas stream in the sub-column, which is then drawn out from the bottom of the sub-column to obtain a top-exit stream. This top-exit stream is partially condensed, and the condensed stream is separated from it and returned to the upper part of the sub-column in a reflux manner to obtain a high-pressure methane-rich stream. b) Liquefying the high-pressure methane-rich stream in tubes arranged in the main heat exchanger through indirect heat exchange with a multicomponent refrigerant that evaporates at low refrigerant pressure on the shell side of the main heat exchanger. c) Compressing the multicomponent refrigerant drawn out from the shell side of the main heat exchanger and partially condensing it at high refrigerant pressure in tubes arranged in the auxiliary heat exchanger through indirect heat exchange with an auxiliary multicomponent refrigerant that evaporates at low auxiliary refrigerant pressure on the shell side of the auxiliary heat exchanger. An auxiliary heat exchanger is used to obtain a multi-component refrigerant for use in step b), which is specifically designed to partially condense the gas stream exiting from the top in tubes arranged within the auxiliary heat exchanger. 2. The method under Claim 1 involves the partial condensation of a multicomponent refrigerant by cooling it to a high refrigerant pressure in tubes provided in the first auxiliary heat exchanger by indirect heat exchange with the auxiliary multicomponent refrigerant that evaporates at a medium auxiliary refrigerant pressure on the shell side of the first auxiliary heat exchanger, and then indirectly cooling it to tubes provided in the second auxiliary heat exchanger by indirect heat exchange with the auxiliary multicomponent refrigerant that evaporates at a low auxiliary refrigerant pressure on the shell side of the second auxiliary heat exchanger, and then partially condensing the top outlet gas by cooling the top outlet gas in tubes provided in the first auxiliary heat exchanger and in the second auxiliary heat exchanger. 3. The method under claim 2 involves partially condensing the gas flow exiting from the top in tubes arranged in the second auxiliary heat exchanger unit. 4. Any one of the methods under claims 1-3 that pre-cools the natural gas stream by indirectly exchanging heat with the refrigerant discharge stream in multiple phases, supplemented by