Production of LNG using an independent dual expander refrigeration cycle

摘要

A process for producing a liquefied natural gas stream from an inlet gas feed stream, the process comprising the steps of: cooling at least a portion of the inlet gas feed stream by heat exchange contact with a first gas-phase refrigerant in a methane refrigeration cycle operated independently of a second gas-phase refrigerant in a nitrogen refrigeration cycle; the methane refrigeration cycle comprising the steps of: expanding a first gas-phase refrigerant comprising methane to form a cold methane vapour steam; cooling at least a portion of the inlet feed gas stream by heat exchange contact with the cold refrigerant vapour stream; compressing the cold methane vapour stream to form a compressed methane vapour stream; and cooling at least a portion of the compressed methane vapour stream by heat exchange contact with the cold methane vapour stream; and the nitrogen refrigeration cycle comprising the steps of: expanding a second gas-phase refrigerant comprising nitrogen to a cold nitrogen vapour stream; cooling at least a portion of the inlet feed gas stream by heat exchange contact with the cold nitrogen vapour stream simultaneously as cooling at least a portion of the inlet feed gas stream by heat exchange contact with the cold methane vapour stream; compressing the cold nitrogen vapour stream to form a compressed nitrogen vapour stream; and cooling at least a portion of the compressed nitrogen vapour stream by heat exchange contact with the cold nitrogen vapour stream; whereby a liquefied natural gas stream is produced.