Method and device to reduce emissions of nitrogen oxides and increase heat transfer in fired process heaters

A fluid mixture nozzle assembly, comprising:

• a fluid mixture nozzle assembly body disposed in fluid communication with a radiant section of a fired heater;
• wherein the fluid mixture nozzle assembly is installed in the fired heater at a location removed from a location of a burner installed in the radiant section of the fired beater;
• the assembly body comprising an open mixing channel, the open mixing channel comprising:
• an upstream converging section, a midstream mixing section, and a downstream diverging section, the open mixing channel configured to mix and entrain a primary fluid mixture with a secondary fluid mixture;
• the converging section comprising a primary fluid jet positioned therein and having a primary jet injection axis along a length of the open mixing channel, the primary fluid jet configured to inject the primary fluid mixture into the open mixing channel, the converging section having a contracting shape configured to entrain and mix the primary fluid mixture with the secondary fluid mixture;
• the mixing section having neither a contracting shape nor an expanding shape, the mixing section comprising a throat dimension configured to constrain an amount of the secondary fluid mixture entrained and mixed with the primary fluid mixture;
• the diverging section having an expansion shape configured to entrain the secondary fluid mixture with the primary fluid mixture;
• and
• the open mixing channel further comprising a curved lower, jet impingement surface positioned downstream of the primary fluid jet in the converging section, the jet impingement surface and the diverging section configured to shape the entrained and mixed primary and secondary fluid mixtures into a principally planar jet at an exit of the diverging section.