Cryogenic air separation method for producing oxygen at high pressures

A method of producing power, the method comprising:

• combusting a fuel with a stream of substantially pure high pressure oxygen gas in a combustor in the presence of a recycle CO2 working fluid stream to form a combustion product stream including CO2 at a pressure of greater than 150 bar;
• expanding the combustion product stream including CO2 across a turbine to form a turbine exhaust stream and generate power;
• removing heat from the turbine exhaust stream in a recuperator heat exchanger;
• separating CO2 from the turbine exhaust stream to form the recycle CO2 working fluid stream;
• compressing the recycle CO2 working fluid stream;
• heating at least a first portion of the recycle CO2 working fluid stream using the heat removed from the turbine exhaust stream in the recuperator heat exchanger and also heating at least a second portion of the recycle CO2 working fluid stream using added heating in a second heat exchanger, the heated, second portion of the recycle CO2 working fluid stream being passed through the recuperator heat exchanger to further heat the first portion of the recycle CO2 working fluid stream;
• passing the first portion of the recycle CO2 working fluid stream from the recuperator heat exchanger to the combustor;
• and
• forming the stream of substantially pure high pressure oxygen gas by a method wherein:
• an inlet air stream is compressed in a first compressor to form a compressed inlet air stream with a pressure of at least 3.5 bar and a temperature of greater than 150° C.;
• heat from the compressed inlet air stream is used as the added heating for heating at least the second portion of the recycle CO2 working fluid stream so that the compressed inlet air stream is cooled;
• the compressed inlet air stream is purified to form a purified inlet air stream;
• the purified inlet air stream is divided into a first portion and a second portion;
• the first portion of the purified inlet air stream is compressed to form an intermediate pressure, purified air stream having a pressure of 20 bar to 90 bar and a high pressure, purified air stream having a pressure of 70 bar to 150 bar, the high pressure, purified air stream having a pressure that is greater than the pressure of the intermediate pressure, purified air stream;
• the intermediate pressure, purified air stream and the high pressure, purified air stream are cooled in a high pressure heat exchanger;
• the second portion of the purified inlet air stream is cooled in a low pressure heat exchanger;
• a first fraction of the high pressure, purified air stream is expanded in a first power producing turbine to form a first expanded, purified air stream;
• a second fraction of the high pressure, purified air stream is expanded in a second power producing turbine to form a second, expanded, purified air stream;
• the intermediate pressure, purified air stream is expanded in a third power producing turbine to form a third expanded, purified air stream;
• the first expanded, purified air stream, the second, expanded, purified air stream, the third, expanded, purified air stream, and the second portion of the purified inlet air stream are passed through a distillation column and to form an exit stream of substantially pure liquid oxygen and a waste stream comprising nitrogen;
• the exit stream of substantially pure liquid oxygen is compressed to a pressure of greater than 150 bar;
• and
• the exit stream of substantially pure liquid oxygen is heated to a temperature of greater than −10° C. in the high pressure heat exchanger against the intermediate pressure, purified air stream and the high pressure, purified air stream to form the substantially pure high pressure oxygen gas.