NOVELTY - Modifying a process for separating more than 3C-hydrocarbon from a hydrocarbon-rich stream (1) to a process for separating more than 2C-hydrocarbon from a hydrocarbon-rich stream, comprises condensing the hydrocarbon-rich stream and separating in a liquid- (2) and a gaseous fraction (4); separating the liquid fraction into more than 3C-hydrocarbon containing product stream (3) and a low boiling component containing residual gas stream; relaxing the output gaseous fraction and separating the more than 3C-hydrocarbon; and finally obtaining a gaseous, 2C-hydrocaborn containing product stream.    USE - The invention deals with the method for modifying a process for separating more than 3C-hydrocarbon from a hydrocarbon-rich stream to a process for separating more than 2C-hydrocarbon from a hydrocarbon-rich stream.    ADVANTAGE - In the method, both separation of more than 3C- and more than 2C-hydrocabron takes place in the same plant and no additional 2C-hydrocarbon extracting unit is required, so that the method is economical and time saving.    DETAILED DESCRIPTION - Method for modifying a process for the separation of more than 3C-hydrocarbon from a hydrocarbon-rich stream to a process for the separation of more than 2C-hydrocarbon from a hydrocarbon-rich stream, cooling and partially condensing the hydrocarbon-rich stream (1) and separating into a liquid (2) and a gaseous fraction (4); separating the liquid fraction, in a rectification column, into a more than 3C-hydrocarbon containing product stream (3) and a low boiling component containing residual gas stream; relaxing the output gaseous fraction and separating the more than 3C-hydrocarbon from the relaxed fraction (5) and likewise bringing the rectification, in a washing column; and warming the less than 2C-hydrocarbon containing fraction that is separated from the washing, against cooled procedure stream; providing an additional rectification column that is interconnected with the washing column in such a way that the washing column forms the upper part and the additional rectification column forms the lower part of a demethanizer column; supplying the liquid fraction obtained in the partial condensation into the lower part of demethanizer column; supplying at least a partial stream of the gaseous fraction obtained in the partial condensation into the washing column as return path; supplying the obtained liquid, essentially more than 2C-hydrocarbon containing fraction of the rectification column into the lower part of the demethanizer column; and finally obtaining a gaseous, essentially 2C-hydrocaborn containing product stream.    DESCRIPTION OF DRAWING(S) - The figure shows the process scheme for the separation of more than 3C-hydrocarbon from a hydrocarbon-rich stream to a process for the separation of more than 2C-hydrocarbon from a hydrocarbon-rich stream:    Hydrocarbon rich stream; (1)    Liquid fraction (2)    More than 3C-hydrocarbon containing product stream; (3)    Gaseous fraction; (4)    Relaxed fraction. (5)