The technology combines a secondarily-fueled boiler with a primary-fueled Rankine steam cycle combustion system in a hybrid process. Outputs from a secondarily-fueled combustion system are fed into the feedwater heater(s), deaerators, feedwater heating lines, and/or reheat lines of a primary-fueled Rankine system. The integrated steam flow eliminates or reduces one or more extractions from the steam turbine generator, thereby allowing it to generate more electrical power using the same Rankine system input energy or generate equivalent electrical power using energy inputs from multiple fuel sources. The technology can be utilized in any type and/or configuration of secondary fuel or secondarily-fueled combustion technology and/or can utilize any type of primary-fueled steam source.