NATURAL GAS TREATMENT METHOD FOR MINIMIZING ETHANE LOSS

The invention relates to a method for treating a gas stream (1) containing at least one acid gas, ethane and one light gas selected from among methane, carbon monoxide, hydrogen, and nitrogen. Said method includes the following steps: step a): supplying said gas stream (1) to a cryogenic separation unit (A) including at least one distillation column (14) for treating said gas stream (1), the treatment including partial elimination of the acid gas from said gas stream and production of a gas stream depleted of acid gas, and said at least one distillation column (14) including a main means (33) for supplying a liquid flow; step b): sampling, from the cryogenic separation unit (A), at least one portion (23) of the treated gas stream depleted of acid gas; step c): supplying at least one portion of the treated gas stream (23) depleted of acid gas to a physical separation unit (29) that separates the acid gas from the ethane, in which said stream is separated so as to form a residue, enriched with light gas and ethane (31), and a permeate stream (30) enriched with acid gas; and step d) returning the stream (30) enriched with acid gas into the cryogenic separation unit (A) by adding it separately from the supply, defined in step a), from the cryogenic separation unit (A) and below the main supply means (33) of the column (14) so as to extract the ethane from one of the at least one distillation column(s) (14). (Figure 2)