US 12,044,468 B2Granted

Method of cooling boil-off gas and apparatus therefor

AssigneeLGE IP Management Company Limited

InventorNikola Felbab

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Abstract

A method of cooling a boil-off gas (BOG) stream from a liquefied gas tank comprising at least the step of heat exchanging the BOG stream with a first refrigerant in a heat exchanger, the heat exchanger having an entry port and a warmer exit port, and comprising at least the steps of: (a) passing the first refrigerant into the entry port of the heat exchanger and into a first zone of the heat exchanger to exchange heat with the BOG stream, to provide a first warmer refrigerant stream; (b) withdrawing the first warmer refrigerant stream from the heat exchanger at an intermediate exit port between the entry port and the warmer exit port; (c) passing the first warmer refrigerant stream through an entry port located in a second zone of the heat exchanger that is warmer than the first zone (d) passing an oil-containing refrigerant stream through an entry port located in a second zone of the heat exchanger that is warmer than the first zone; (e) mixing the first warmer refrigerant stream and the oil-containing stream in the heat-exchanger to form a combined refrigerant stream; and (f) passing the combined refrigerant stream out of the heat exchanger through the warmer exit port.

Claims14

Dependent claims

(a) passing the first refrigerant into the entry port of the heat exchanger and into a first zone of the heat exchanger to exchange heat with the BOG stream and to provide a warmer refrigerant stream;
(b) withdrawing the warmer refrigerant stream from the heat exchanger at an intermediate exit port between the entry port and the warmer exit port;
(c) passing the warmer refrigerant stream back into the heat exchanger through a second entry port located in a second zone of the heat exchanger, the second zone of the heat exchanger being warmer than the first zone;
(d) providing a single mixed refrigerant (SMR) in an SMR recirculating system, the system comprising at least the steps of:
(1) compressing the SMR using at least one oil-injected screw compressor to provide a post-compression SMR stream,
(2) separating the post-compression SMR stream to provide an oil-based stream and a first SMR vapour stream,
(3) passing the first SMR vapour stream into the heat exchanger to cool the first SMR vapour stream and provide a cooled first SMR vapour stream,
(4) withdrawing the cooled first SMR vapour stream from the heat exchanger,
(5) separating the cooled first SMR vapour stream to provide an oil-containing liquid-phase SMR stream and an oil-free SMR vapour stream, and
(6) passing the oil-free SMR vapour stream through the heat exchanger to provide a condensed SMR stream;
(e) expanding the condensed SMR stream to provide an expanded lowest temperature SMR stream serving as the first refrigerant for heat exchange against the BOG stream;
(f) passing the expanded lowest temperature SMR stream through the heat exchanger to provide the warmer SMR stream;
(g) expanding the oil-containing liquid-phase SMR stream of step (5) to provide an at least partially expanded oil-containing refrigerant stream;
(h) passing the at least partially expanded oil-containing refrigerant stream into the heat exchanger through a third entry port located in a second zone of the heat exchanger;
(i) combining the warmer SMR stream from step (c) with the at least partially expanded oil-containing refrigerant stream from step (g) in the second zone of the heat exchanger to provide a combined refrigerant stream;
and
(j) passing the combined refrigerant stream out of the heat exchanger through the warmer exit port.

14 more elements

An apparatus for cooling a boil-off gas (BOG) stream from a liquefied gas tank comprising:

a heat exchanger for receiving the BOG stream and having an entry port and a warmer exit port, the heat exchanger further comprising
a first refrigerant directed into the entry port and into a first zone within the heat exchanger to exchange heat with the BOG stream and to provide a warmer refrigerant stream;
an intermediate exit port between the entry port and the warmer exit port, the warmer refrigerant stream directed through the intermediate exit port and out of the heat exchanger;
a second entry port located in a second zone of the heat exchanger, the second zone of the heat exchanger being warmer than the first zone, and directing the warmer refrigerant stream through the second entry port and into the heat exchanger;
and
a single mixed refrigerant (SMR) recirculating system having
(1) at least one oil-injected screw compressor for compressing the SMR using to provide a post-compression SMR stream,
(2) a separator for separating the post-compression SMR stream to provide an oil-based stream and a first SMR vapour stream,
(3) directing the first SMR vapour stream into the heat exchanger to cool the first SMR vapour stream and provide a cooled first SMR vapour stream, and withdrawing the cooled first SMR vapour stream from the heat exchanger,
(4) a separator for separating the cooled first SMR vapour stream to provide an oil-containing liquid-phase SMR stream and an oil-free SMR vapour stream, and
(5) directing the oil-free SMR vapour stream through the heat exchanger to provide a condensed SMR stream;
withdrawing the condensed SMR stream from the heat exchanger;
a pressure reducing device for expanding the condensed SMR stream to provide an expanded lowest temperature SMR stream, the expanded lowest temperature SMR stream forming the first refrigerant for the heat exchanger;
a further pressure reducing device for expanding the oil-containing liquid-phase SMR stream to provide an at least partially expanded oil-containing refrigerant stream;
directing the expanded lowest temperature SMR stream through the heat exchanger for heat exchange against the BOG stream to provide the warmer SMR stream;
directing the at least partially expanded oil-containing refrigerant stream into the heat exchanger through a third entry port located in the second zone of the heat exchanger;
combining the warmer SMR stream, directed into the heat exchanger through the second entry port, with the oil-containing refrigerant stream, directed into the heat exchanger through the third entry port, within the heat exchanger to provide a combined refrigerant stream;
and
directing the combined refrigerant stream out of the heat exchanger through the warmer exit port.

16 more elements

Dependencies are inferred from the claim text.

Facts

Application: 17/635,110Filed 21 Aug 2020
Priority: GB 191212623 Aug 2019
Published: US 2022/0275998 A11 Sep 2022
Granted: 23 Jul 2024
Term ends: Not estimatedThe source records don’t support an estimate.

Classification11 codes

F25J 1/0025
Hydrocarbons, e.g. natural gas: boil-off gases "BOG" from storages
F25J 1/0055
By vaporising a liquid refrigerant stream: originating from an incorporated cascade
F25J 1/0212
Using a multi-component refrigerant [MCR] fluid in a closed vapor compression cycle: as a single flow MCR cycle
F25J 1/0216
With one SCR cycle: using a C3 pre-cooling cycle