Abstract: The treatment unit comprises N adsorption units, N being greater than or equal to 1, operating on a parametrized cycle split uniformly into at most N phase times. Further more, use is made of a control unit for controlling the treatment unit, designed to modify at least one parameter of the cycle. Each time there is a predicted change in the composition of the feed gas, the control unit is sent a pre-established signal representing this change. The processing unit then processes the signal to determine the parameters of an exceptional operating cycle of the treatment unit which cycle is suited to the predicted change.