TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Components: The stream rich in C2+ hydrocarbons is formed from the bottom stream of column. The expanded fraction obtained from the second dynamic expansion turbine forms the effluent obtained from the dynamic expansion turbine. The part of the effluent obtained from the dynamic expansion turbine is cooled and partially liquefied in a heat exchanger to form the cooled reflux stream. The process further comprises sampling a stream for reboiling in the first column of distillation at a sampling level, linking the heat exchange of reboiling stream with the part of the effluent obtained from a dynamic expansion turbine in the heat exchanger for cooling and partially liquefying the part of the effluent obtained from the turbine for dynamic expansion, and re-introducing the reboiling stream in the first distillation column to a level below the level of sampling, introducing the expanded fraction obtained from the second turbine for dynamic expansion in downstream separator tank to form a third gaseous overhead stream and a third bottom stream liquid, cooling the third gaseous overhead stream in the heat exchanger to form the cooled reflux stream, cooling and partially condensing the second fraction of the feeding stream, introducing the second fraction of the cooled feed stream in an upstream ball separator to form a second gas fraction and a second liquid fraction, introducing the second gas fraction in the second dynamic expansion turbine, introducing the second liquid fraction after expansion in a lower part of the first distillation column, passing an overhead stream rich in methane column in the first heat exchanger, sampling an auxiliary expansion stream in the overhead stream of column rich in methane after passing in the first heat exchanger, dynamically expanding the auxiliary expansion stream in an auxiliary turbine of dynamic expansion, and introducing the expanded stream obtained from the auxiliary turbine of dynamic expansion in the overhead stream of column rich in methane before its passage in the first heat exchanger. After cooling in an auxiliary distillation column, the cooled reflux stream is formed from the bottom stream of the auxiliary distillation column. A fraction of the overhead stream of column and the part of the effluent of the dynamic expansion turbine contact with heat exchange in downstream heat exchanger different from the second heat exchanger.