Patent ID: 7614241

Claim:
An apparatus for reliquefaction of boiloff gas from a liquefied natural gas storage container, said apparatus comprising: a boiloff gas recovery portion comprising: a first heat exchanger including a first flow path adapted for receiving boiloff gas flowing from a liquefied natural gas storage container and recovering the refrigerative value therefrom; a boiloff compressor adapted for receiving and compressing the boiloff gas from the first flow path of said first heat exchanger; a boiloff aftercooler adapted for receiving and cooling the compressed boiloff gas from the boiloff compressor; said first heat exchanger further including a second flow path adapted for receiving the cooled compressed boiloff gas from said boiloff aftercooler in a direction countercurrent to the boiloff gas flowing through the first flow path, for imparting thereto the refrigerative value recovered from the boiloff gas passing through the first flow path; and a closed-loop refrigeration portion being adapted for receiving and cooling the compressed boiloff gas from the second flow path of the first heat exchanger to a temperature sufficient to achieve liquefaction thereof; said closed-loop refrigeration portion comprises: only one single stage main compressor adapted for compressing a refrigerant; a first aftercooler adapted for receiving and cooling the compressed refrigerant from the only one single stage main compressor; a second heat exchanger having a first flow path for receiving the cooled compressed refrigerant from the first aftercooler, and a second flow path for receiving the compressed boiloff gas from the second flow path of the first heat exchanger; and a turboexpander adapted for receiving a portion of the refrigerant from the first flow path of the second heat exchanger and cooling the refrigerant.