Patent attributes
Power is produced by operating first and second nested cycles utilising CO2 as working fluid without mixing of working fluid between the nested cycles. The first cycle comprises a semi-open loop operating under low pressure conditions in which CO2 is sub-critical. The second cycle comprises a closed loop operating under higher pressure conditions in which CO2 is supercritical. The first cycle operates in a Brayton cycle including oxycombustion of hydrocarbons, preferably LNG, in a combustion chamber under low pressure conditions, expansion for power production to provide a first power source, cooling in a recuperator, compression, reheating by counter-current passage via the recuperator, and return of working fluid heated by the recuperator back to the combustion chamber. Water and excess CO2 resulting from the oxycombustion step are separated from the first cycle. The first cycle serves as a source of heat for the second cycle by gas/gas heat exchange in a gas/gas heat exchanger which results in cooling of the products of combustion and circulating working fluid in the first cycle and heating of working fluid in the second cycle. The second cycle is operated in a Brayton cycle including heating of working fluid in the second cycle by the gas/gas heat exchanger, expansion for power generation to provide a second power source, cooling in two-stages by first and second recuperator steps, compression, reheating by counter-current passage via the first recuperator step, and return of working fluid heated by the first recuperator step back to the gas/gas heat exchanger. Working fluid in the first cycle following the compression step is heated by working fluid in the second cycle by counter-current passage via the second recuperator step.
