Process and apparatus for the separation of air by cryogenic distillation

An apparatus for the separation of air by cryogenic distillation comprising:

• a column system comprising at least one column, a heat exchanger, a turbine;
• means for sending compressed and purified air at a first pressure to be cooled at the first pressure in the heat exchanger;
• means for sending the cooled air in gaseous form from the heat exchanger to the column system;
• means for sending a gaseous nitrogen stream from the column system to be warmed in the heat exchanger;
• means for sending a liquid stream enriched in oxygen or nitrogen from the column system to be vaporized and warmed in the heat exchanger;
• means for sending a first gaseous stream having a nitrogen content at least that of air and at a higher pressure than the first pressure to be cooled and liquefied or pseudo liquefied in the heat exchanger to form a liquefied stream;
• means for sending at least part of the liquefied stream to be warmed and vaporized in the heat exchanger to a first intermediate temperature of the heat exchanger to form a vaporized stream;
• means for removing the vaporized stream from an intermediate section of the heat exchanger;
• a conduit for sending the vaporized stream to be expanded, at least in part, in the turbine to form an expanded stream;
• a conduit for sending at least part of the expanded stream to the column system, a conduit for sending a second gaseous stream having the same nitrogen content as the first stream to be cooled in the heat exchanger;
• conduit means for removing at least part of the second gaseous stream from an intermediate section of the heat exchanger at a second intermediate temperature and sending the at least part of the second gaseous stream to the turbine to be expanded with the vaporized stream;
• conduit means for sending a further stream having a nitrogen content at least that of air to be liquefied or pseudo-liquefied in the heat exchanger;
• expansion means;
• and
• means for sending the further stream to the expansion means and conduit means for sending the expanded further stream to the column system.