A fuel combustion power generation system is provided operating as a closed loop Rankine cycle and with zero atmospheric emissions. The fuel is combusted with oxygen in a combustor to generate high temperature products of combustion. The products of combustion are routed to a first side of a heat exchanger. A second side of the heat exchanger has a working fluid of the closed loop Rankine cycle passed therethrough to boil the working fluid into a gas. The working fluid is then expanded, condensed back to a liquid and pumped back to high pressure for return to the heat exchanger the products of combustion enter a condenser, where gases are collected and liquids recirculated or released. The products of combustion can be expanded upstream of the heat exchanger. The fuel can be a gaseous fuel or a solid or liquid fuel, such as coal or biomass, with gasification before combustion.