NOVELTY - The process comprises heating expanded further cooled first stream in a heat and mass transfer unit housed in a processing assembly and then discharging as a vapor fraction and a liquid fraction; combining overhead vapor stream with vapor fraction to form a combined vapor stream; and cooling the combined vapor stream to supply a portion of the heat stream while simultaneously condensing less volatile components from the combined vapor stream to form a condensed stream and a residual vapor stream and then discharging the residual vapor stream as the volatile residue gas fraction.    USE - The process is useful for the separation of a gas stream containing methane, carbon (C2) components, carbon (C3) components and heavier hydrocarbon components into a volatile residue gas fraction and a relatively less volatile fraction containing a major portion of the C2 components, the C3 components and the heavier hydrocarbon components or the C3 components and heavier hydrocarbon components (claimed).    ADVANTAGE - The process allows efficient and reliable separation of gas stream containing methane, carbon (C2) components, carbon (C3) components and heavier hydrocarbon components into a volatile residue gas fraction and a relatively less volatile fraction at low cost in an environmentally friendly manner.    DETAILED DESCRIPTION - The process comprises treating a gas stream in heat exchange steps and division steps to produce a first stream that is cooled under pressure to condense all of it and a second stream is cooled under pressure; expanding the condensed first stream to a lower pressure so that the stream is further cooled and then supplying at a top feed position on a distillation column that produces an overhead vapor stream and a bottom liquid stream; expanding the cooled second stream to the lower pressure and then supplying to the distillation column at a mid-column feed position; fractionating the expanded further cooled first stream and the expanded second stream in the distillation column at the lower pressure so that the components of the relatively less volatile fraction are recovered in the bottom liquid stream and the volatile residue gas fraction is discharged as the overhead vapor stream; heating the expanded further cooled first stream in a heat and mass transfer unit housed in a processing assembly and then discharging as a vapor fraction and a liquid fraction; combining the overhead vapor stream with the vapor fraction to form a combined vapor stream; cooling the combined vapor stream in the heat and mass transfer unit to supply a portion of the heat stream while simultaneously condensing the less volatile components from the combined vapor stream for forming a condensed stream and a residual vapor stream and then discharging the residual vapor stream from the processing assembly as the volatile residue gas fraction; combining the condensed stream with the liquid fraction to form a combined liquid stream; supplying the combined liquid stream to the top feed position of the distillation column; and maintaining the overhead temperature of the distillation column at a temperature, using the quantity and temperature of the combined liquid stream, so that the major portions of the components in the relatively less volatile fraction are recovered in the bottom liquid stream. The combined liquid stream is supplied to the top feed position of the distillation column using a pumping unit. The pumping unit is housed in the processing assembly. The gas stream is cooled under pressure in the heat exchange steps to partially condense the stream. The partially condensed gas stream is separated to provide a vapor stream and a liquid stream. The vapor stream is divided in the division step to produce a first vapor stream and a second vapor stream. The first vapor stream is cooled under pressure in the heat exchange steps to condense all of the stream to form the condensed first stream. The second vapor stream is expanded to the lower pressure for forming the expanded second stream. A portion of the liquid stream is expanded to the lower pressure, and the expanded liquid stream is supplied to the distillation column at a lower mid-column feed position below the mid-column feed position. The expanded further cooled first stream, the expanded second stream and the expanded liquid stream are fractionated in the distillation column at the lower pressure so that the components of the relatively less volatile fraction are recovered in the bottom liquid stream. The first vapor stream is combined with a portion of the liquid stream to form a combined stream. The combined stream is cooled under pressure in the heat exchange steps to condense all of the stream and to expand to the lower pressure so that the stream is further cooled. The expanded cooled combined stream is heated in the heat and mass transfer unit and discharged as the vapor fraction and the liquid fraction. The remaining portion of the liquid stream is expanded to the lower pressure, and the expanded liquid stream is supplied to the distillation column at the lower mid-column feed position. An INDEPENDENT CLAIM is included for an apparatus for the separation of a gas stream containing methane, C2 components, C3 components and heavier hydrocarbon components into a volatile residue gas fraction and a relatively less volatile fraction containing a major portion of the C2 components, C3 components and heavier hydrocarbon components or the C3 components and heavier hydrocarbon components.    DESCRIPTION OF DRAWING(S) - The diagram shows a schematic view of a natural gas processing plant.    Heat exchanger (12)    Expansion valve (13)    Expansion machine (14)    Compressor (15)    Discharge cooler. (20)