Electricity generation method using an air gas separation unit and a combustion unit

A method for generating electricity by burning of carbonaceous fuels using an air separation unit, a compression purification unit, and a unit for burning carbonaceous fuels, said method comprising;

• a compression purification unit for separating a carbon dioxide stream from a combustion flue gas originating in the carbonaceous fuel burning unit,
• a first operating mode with air in which said carbonaceous fuel burning unit is supplied with air and no oxygen-enriched fluid originating from the air separation unit, and
• a second operating mode with oxygen in which said carbonaceous fuel burning unit is supplied only with an oxidant that is leaner in nitrogen and richer in oxygen than the air,
• said oxidant originating at least partially from the air separation unit and said compression purification, in which, during the operation of the air separation unit, air is sent to the air separation unit, wherein,
• if a sale price of the electricity generated exceeds a first threshold, or
• if a purchase price of electricity consumed by at least one of the units exceeds a second threshold, or
• if a price of venting the combustion flue gas is below a third threshold, or
• if a ratio between the price for venting the flue gases and the sale price of the electricity is below a fourth threshold,
• the quantity of flue gas sent to the compression purification unit is reduced and the quantity of flue gases which is vented is increased.