US 2024/0288125 A1 · PROCESS AND APPARATUS FOR RELIQUEFACTION AND RECYCLING OF BOG INTO AN LNG TANK

Abstract

Method and apparatus for reliquefying and returning boil-off gas (BOG) to a liquefied natural gas (LNG) tank, the method including: Withdrawing BOG (F2) from the headspace of an LNG tank; compressing the BOG in a first compression stage to a first pressure p1 between 8 and 18 bara and tapping of a first portion of this gas; further compressing a second portion of the gas from step in a final compression stage to a second pressure p2≥120 bara; cooling at least part of the further compressed gas to a first temperature T1 between −20° C. and −100° C.; expanding the gas from step to a third pressure p3 between 8 and 20 bara; and separating the gas from step into a liquid phase and a gaseous phase to combine the gaseous phase with the tapped first portion of the gas from the first compression stage and to return the liquid phase into the LNG tank.

Claims21

Dependent claims

A method for reliquefying and returning boil-off (BOG) to a liquefied natural gas (LNG) tank, comprising the steps of:

a) withdrawing BOG from the headspace of an LNG tank;
b) compressing the BOG in a first compression stage to a first pressure p1 between 8 and 18 bara and tapping of a first portion of this gas;
c) further compressing a second portion of the gas from step b) in a final compression stage to a second pressure p2≥120 bara;
d) cooling at least part of the further compressed gas from step c) to a first temperature T1 between −20° C. and −100° C.;
e) expanding the gas from step d) to a third pressure p3 between 8 and 20 bara;
f) separating the gas from step e) into a liquid phase and a gaseous phase to
f1) combine the gaseous phase with the tapped first portion of the gas from step c);
and
f2) return the liquid phase to the LNG tank.

6 more elements

An apparatus for reliquefying and returning boil-off gas (BOG) into a liquefied natural gas (LNG) tank comprising

a first heat exchanger comprising a line for passing through cooling fluid and a line for passing through compressed gas to be cooled;
a multi-stage compressor comprising at least a first compression stage and a final compression stage, the first compression stage being configured to compress BOG from the LNG tank to a first pressure p1 between 8 and 18 bara and wherein the final compression stage is configured to compress pre-compressed BOG to a second pressure p2≥120 bara;
a branch line which is arranged downstream of the first compression stage in a fluid-conducting manner and which opens further downstream into at least one of a supply line for a low-pressure gas injection engine and a gas combustion unit;
a return line;
a first expansion unit configured to expand compressed gas from a second pressure p2 to a third pressure p3, wherein p3 is between 8 and 20 bara;
a gas-liquid separator configured to separate a liquefied gas portion for feeding back into the LNG tank at a pressure p3 and to feed a gaseous portion into a bypass line, the bypass line opening into the branch line;
wherein the multi-stage compressor is connected upstream in a fluid-carrying manner to the headspace of the LNG tank, and wherein the multi-stage compressor is connected downstream in a fluid-carrying manner via the return line to the line of the first heat exchanger for passing through compressed gas to be cooled, is connected further downstream to the first expansion unit, and is connected still further downstream to the gas-liquid separator.

4 more elements

Dependencies are inferred from the claim text.

Process and apparatus for reliquefaction and recycling of bog into an lng tank

Life of this patent

Process and apparatus for reliquefaction and recycling of bog into an lng tank

Life of this patent

Abstract

Claims21