NOVELTY - A pre-cooled gas is circulated through the liquefaction unit to produce precooled liquefaction unit. A bypass stream of dry sweet scrubbed gas is directed through light mixed refrigerant circuit of pre-cooled liquefaction unit (24) at primary mass flow rate. The pressurized bypass gas stream is cooled using propane refrigeration circuit to produce cooled pressurized bypass gas stream. The cooled pressurized bypass gas stream is circulated, and ethane-saturated pressurized bypass stream is cooled in propane refrigerant circuit, to obtain ethane.    USE - Production of ethane used for producing mixed refrigerant used in preparation of liquefied natural gas.    ADVANTAGE - The ethane is efficiently produced.    DETAILED DESCRIPTION - A pre-cooled gas is circulated through the liquefaction unit to produce a precooled liquefaction unit. A bypass stream of dry sweet scrubbed gas is directed through the light mixed refrigerant circuit of pre-cooled liquefaction unit at a primary mass flow rate to fill the pre-cooled liquefaction unit with the bypass stream. One or more compressors are runned in the mixed refrigerant circuit to compress the bypass stream of dry sweet scrubbed gas and produce a pressurized bypass gas stream. The pressurized bypass gas stream is cooled using the propane refrigeration circuit to produce a cooled pressurized bypass gas stream. The cooled pressurized bypass gas stream is circulated through the light mixed refrigerant circuit of main heat exchanger (26) such that the cooled pressurized bypass gas is cooled as it expands across an expansion valve into the shell side circuit (42) of the main heat exchanger. The cooled pressurized bypass stream is progressively cooled to form a fully condensed cooled liquid bypass stream. The cooled liquid bypass stream is evaporated in the shell side circuit of the main heat exchanger to produce a primary fraction rich in nitrogen and methane and a secondary fraction rich in ethane, propane, butane and the heavy hydrocarbons. A mass flow rate of primary fraction is flared from the cold end of main heat exchanger. A mass flow rate of the bypass stream is adjusted to compensate for the mass flow rate of the primary fraction flared. The secondary fraction is directed to flow out of the warm end of the shell side circuit into the bypass stream fed to the mixed refrigerant circuit to produce an ethane-saturated pressurized bypass stream. The ethane-saturated pressurized bypass stream is cooled in the propane refrigerant circuit to produce a condensed heavy mixed refrigerant stream containing liquid ethane for storage in a buffer storage vessel, to obtain ethane. The liquefied natural gas production plant is provided using a propane pre-cooled mixed refrigerant process for liquefaction after start-up. The liquefied natural gas production plant contains a liquefaction unit comprising a main heat exchanger, a propane refrigerant unit and a mixed refrigerant unit.    DESCRIPTION OF DRAWING(S) - The drawing shows the schematic flow chart of propane precooled mixed refrigerant liquefaction unit.    Liquefied natural gas (10)    Liquefaction unit (24)    Main heat exchanger (26)    Shell side circuit (42,46)    Warm end (56)