Abstract: An immersion heater for a fluidized bed decarbonation reactor includes an elongate cylindrical graphite heating element within a sealed chamber into which an inert gas, such as argon, is introduced for protecting the heating element from oxidation and from which the gas may be removed. The chamber is defined by a refractory metal sheath with longitudinal corrugations and externally covered by a protective layer formed by chromaluminization. An insulating refractory metal ring centers and holds the heating element within the sheath to prevent short circuits between the heating elements and the sheath. A composite metal plate holds the heating element and includes input and output electrical supply bars for providing power to the heater.