from the same water circuit as that used for cooling the air at the inlet of the purification unit in order to cool air output by the air supercharger 5 and or the air output by the supercharger 17 and or the mp 13 and or iii by sending an increased stream of air to the blowing turbine 19 in such a way that the ratio of the quantity of air v sent to the exchanger to the volume of air d sent to the blowing turbine is less than 10 1 these means for generating refrigeration may also be employed in the case in which no liquid is produced as final product the superchargers 5 17 and or the main compressor not illustrated may be driven by an electric motor and or by a hydraulic motor and or by a steam turbine and or by a gas turbine the turbine 19 may have a dedicated supercharger or a generator the installation may also include conventional components well known to those skilled in the art such as a claude turbine a hydraulic turbine a medium pressure or low pressure nitrogen turbine for refrigeration top up by tippling one or more argon production columns a mixing column fed with air and oxygen from the low pressure.