Equipment and process for liquefaction of LNG boiloff gas
AssigneeAMCS Corporation
InventorRobert Anthony Mostello
Life of this patent
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Abstract
A design for equipment and process for reliquefaction of LNG boiloff gas, primarily for shipboard installation, has high thermodynamic efficiency and lower capital cost, smaller size (volume, footprint), lower weight, and less need for maintenance than systems utilizing the prior art. The main refrigerant gas compressor is reduced to a single stage turbocompressor. Optional elements include: compression of boiloff gas at ambient temperature; compression of boiloff gas in one or two stages; turboexpansion of refrigerant gas incorporating one or two turboexpanders; turboexpander energy recovery by mechanical loading, compressor drive, or electric generator; refrigerant sidestream for cooling at the lowest temperatures.
Claims7
A process for reliquefaction of boiloff gas from a liquefied natural gas storage container, comprising the steps of:
- compressing a refrigerant in only one single stage main compressor to yield a compressed refrigerant;
- passing the compressed refrigerant from the only one single stage main compressor through a first aftercooler for cooling to a first temperature;
- passing the cooled refrigerant from the first aftercooler through a first flow path of a first heat exchanger for further cooling to a second temperature lower than said first temperature;
- withdrawing a first portion of said refrigerant at said second temperature from the first flow path of said first heat exchanger;
- passing the first portion of said refrigerant through a first turboexpander for cooling to a third temperature lower than said second temperature;
- passing the refrigerant from said first turboexpander through a second flow path of the first heat exchanger in a direction countercurrent to the refrigerant flowing through the first flow path of said first heat exchanger;
- compressing a boiloff gas from a liquefied natural gas storage container through a boiloff compressor to a desired pressure;
- and
- passing the compressed boiloff gas from the boiloff compressor through a third flow path of the first heat exchanger in a direction countercurrent to the refrigerant flowing through said second flow path thereof, for cooling to a temperature sufficient to achieve liquefaction thereof.
Dependencies are inferred from the claim text.