A fluidized fuel gas combustor system for a catalytic dehydrogenation process comprising a vessel having a lower portion and an upper portion; a plurality of air injection diffusers located in the lower portion of the vessel; a plurality of fuel gas injection diffusers located on fuel gas distributors disposed in the vessel and spaced apart from and above a plurality of air injection diffusers, wherein the fuel gas diffusers are placed in a manner to maximize even mass distribution of a fuel gas injected through the fuel gas diffusers in the vessel, wherein each fuel distributor comprises a tube having a plurality of fuel gas injection diffusers; and one or more grid assemblies disposed in the vessel spaced above the fuel gas distributors is provided.