US 5,363,655 AGranted

Method for liquefying natural gas

AssigneeChiyoda Corporation

InventorsYoshitsugi Kikkawa, Osamu Yamamoto, Junichi Sakaguchi, Moritaka Nakamura

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Abstract

Provided is a method for liquefying natural gas which can be readily adapted to LNG plants of all sizes without requiring expensive and special heat exchangers. The liquefaction of feed gas of natural gas and recycle natural gas is carried out with a single-component refrigerant or a mixed refrigerant in a high temperature stage, and with a substantially isentropic expansion in a low temperature stage, and a non-liquefied part of the recycle gas after the expansion step is pressurized with a compressor and recycled along with a recycle stream of non-liquefied par of the feed natural gas, the liquefied part by the refrigerant exchanging heat with the non-liquefied part stream produced from the substantially isentropic expansion, in a plate-fin heat exchanger or the like. The compressor is driven by the power obtained by the substantially isentropic expansion.

Claims12

Dependent claims

A method for liquefying natural gas, comprising the steps of:

cooling feed natural gas with a refrigerant in a first feed gas stage to produce liquefied and non-liquefied parts of said feed natural gas;
cooling the non-liquefied part of said feed natural gas with a substantially isentropic expansion in a second feed gas stage to produce liquefied and non-liquefied parts of said feed natural gas;
pressurizing and recycling the non-liquefied part of said feed natural gas from said second feed gas stage by using a first compressor to produce a recycle natural gas;
cooling the recycle natural gas with a refrigerant in a first recycle gas stage to produce liquefied and non-liquefied parts of said recycle natural gas;
cooling the non-liquefied part of said recycle natural gas from said first recycle gas stage with a substantially isentropic expansion in a second recycle gas stage to produce liquefied and non-liquefied parts of said recycle natural gas;
and
recovering the liquefied parts of said feed natural gas and said recycle natural gas;
said first compressor being driven at least partly by power obtained by at least one of said substantially isentropic expansion steps.

5 more elements

Dependencies are inferred from the claim text.

Facts

Application: 08/028,025Filed 8 Mar 1993
Priority: JP 4-33554020 Nov 1992
Granted: 15 Nov 1994
Term ends: Not estimatedThe source records don’t support an estimate.

Classification20 codes

F25J 1/0278
Offshore use, e.g. during shipping: unit being stationary, e.g. on floating barge or fixed platform
F25J 1/0022
Characterised by the fluid to be liquefied: hydrocarbons, e.g. natural gas
F25J 1/0035
Using the feed stream itself or separated fractions from it, i.e. "internal refrigeration": by gas expansion with extraction of work
F25J 1/0037
By gas expansion with extraction of work: of a return stream