Abstract: A system for recovering the waste heat normally exhausted in the atmosphere by blast furnace stoves or other variable temperature process heaters. The system comprises a heat exchange apparatus located in the exhaust stack, heat transfer means for carrying the waste heat absorbed from the exhaust gases to a location remote therefrom, and a second heat exchange apparatus for releasing the transferred waste heat for beneficial use at the remote location. This invention also includes a reservoir for storing the heat transfer fluid used in the system and also the reservoir acts as a heat sink to moderate the temperature variation of the heat transfer fluid. The system also includes means for controlling temperature of the first heat exchanger and means for controlling the temperature of the variable temperature process heater. The preferred heat transfer fluid is maintained as a liquid during its use in the system.