Editing Boiler (section)

==Heat sources==
In a [[fossil fuel power plant]] using a steam cycle for power generation, the primary heat source will be combustion of [[Pulverized coal-fired boiler|coal]], oil, or natural gas. In some cases byproduct fuel such as the carbon monoxide rich offgasses of a coke battery can be burned to heat a boiler; biofuels such as [[bagasse]], where economically available, can also be used. In a nuclear power plant, boilers called [[Steam generator (nuclear power)|steam generators]] are heated by the heat produced by nuclear fission. Where a large volume of hot gas is available from some process, a [[heat recovery steam generator]]  or [[recovery boiler]] can use the heat to produce steam, with little or no extra fuel consumed; such a configuration is common in a [[combined cycle]] power plant where a gas turbine and a steam boiler are used. In all cases the combustion product waste gases are separate from the working fluid of the steam cycle, making these systems examples of [[external combustion engine]]s.