Abstract: A method and assembly for supplying heat in the desired pattern while suppressing the production of nitrogen oxides and carbon dioxide. The assembly includes a fluid mixture nozzle assembly in fluid communication with an external conduit and a radiant section of a fired process heater. The fluid mixture nozzle assembly includes an open mixing channel having an upstream converging section, a midstream mixing section, and a downstream diverging section for entraining a fluid mixture with vitiated flue gas combustion products. The fluid mixture nozzle assembly is installed in the wall, floor, or ceiling of the fired heater.