Natural gas is burned with pure oxygen, not air, resulting in a combustion byproduct of predominantly CO2 and water. Separating oxygen from air in an Air Separation Unit requires energy, but the high efficiency of the Allam cycle more than compensates for this requirement.
NET Power utilizes a single, more compact turbine that will produce all of the plant’s electrical output. Using a single turbine and eliminating all the other steam cycle components typical of combined cycle power plants enables the Allam cycle to reduce costs.
The CO2 exhaust exiting the NET Power turbine also contains valuable heat energy. A heat exchanger is used to transfer this heat to a recycle stream that keeps the energy in the system (called recuperation). This process also cools the turbine exhaust for removal of the small amount of water in the exhaust stream.
The now pure CO2 working fluid is pumped up to pressure and is passed through the other side of the heat exchanger. It uses the original turbine exhaust stream to reheat itself as it makes its way back to the combustor. Some of the CO2 is removed and sent into a pipeline, where it can be used for enhanced oil recovery.
The heat in the turbine exhaust is recycled back to the combustor to keep the heat in the system, rather than lose it up cooling towers. This allows the Allam cycle to control the combustion temperature and to achieve extremely high efficiencies in a much simpler process.