Low temperature method for removing condensable components from hydrocarbon gas

Claim 1

In a method of removing ethane and heavier components from an inlet hydrocarbon gas comprised principally of methane, the combination of steps comprising: turbine expanding said gas to produce a gas-condensate mixture having a temperature below about -50* F.; fractionally distilling said cooled gas condensate mixture to remove ethane and heavier components therefrom by passing said mixture through a low temperature fractionating column having vertically spaced trays; withdrawing condensed ethane and heavier components from a lower portion of said column; flowing the withdrawn condensed ethane and heavier components to liquid storage; withdrawing fractionally distilled non-condensed gas from a top portion of said column; flowing the fractionally distilled non-condensed gas through a heat exchanger to thereby cool said fractionally distilled gas; flowing additional condensed components from said cooled fractionally distilled gas and flowing said additional condensed components back to said column as reflux; turbine expanding said cooled fractionally distilled non-condensed gas a second time, the turbine expanders of said first and second expanding steps being mechanically connected; flowing twice turbine expanded fractionally distilled non-condensed gas through said heat exchanger as the cooling medium therefor; flowing said twice turbine expanded fractionally distilled non-condensed gas through a second and third heat exchanger as the cooling medium therefor to cool the inlet gas to produce a first gas-condensate mixture and to further cool the non-condensed gas separated from the first gas-condensate mixture to produce a second gas-condensate mixture, the non-condensed gas of which is fed to the first turbine and the separated condensates are fed separately to the column as reflux; and recompressing said twice turbine expanded fractionally distilled non-condensed gas after passage through said heat exchangers.