Method of handling a boil off gas stream and an apparatus therefor

Abstract

A boil-off gas (BOG) stream (15) from a liquefied hydrocarbon storage tank is split into a BOG heat exchanger feed stream (25) and a BOG bypass stream (35). The BOG heat exchanger feed stream (25) is heat exchanged in a BOG heat exchanger (40) against a process stream (135), thereby providing a warmed BOG stream (45) and a cooled process stream (195). The warmed BOG stream (45) is combined with the BOG bypass stream (35) to provide a temperature controlled BOG stream (55). Herein, the mass flow of the process stream (135) is controlled in response to a measured first temperature of at least one of (i) the warmed BOG stream (45) and (ii) the cooled process stream (195) to move the measured first temperature towards a first set point temperature; and the mass flow of one or both of the BOG heat exchanger feed stream (25) and the BOG bypass stream (35) are controlled in response to a measured second temperature of the temperature controlled BOG stream (55), to move the measured second temperature towards a second set point temperature.

Description

technical field [0001] The present invention provides a method and apparatus for treating boil-off gas streams from cryogenically stored liquefied hydrocarbon reserves. Background technique [0002] An economically important example of cryogenic storage of liquefied hydrocarbon reserves is liquefied natural gas (LNG). LNG can be stored at approximately -162°C at near atmospheric pressure. [0003] Natural gas is a useful source of fuel and is a source of various hydrocarbon compounds. A liquefied natural gas (LNG) facility at or near the source of the natural gas stream to liquefy the natural gas is often required for several reasons. Natural gas, for example, is easier to store and transport over long distances in its liquid state than in its gaseous state because it occupies less volume and does not require high pressure storage. [0004] Typically, natural gas, consisting primarily of methane, enters an LNG plant at high pressure and is pretreated to produce a clean fe...

AI Technical Summary

Problems solved by technology

Reduced mass flow from design operating conditions may result in reduced compressor specific power or efficiency

[0010] Thus, for example, if one wishes to compress the stream, for example to provide fuel gas, these variations in temperature may make further processing of the stream more difficult

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