a dual - fuel burner for use in furnaces such as in steam cracking . the burner includes a primary air chamber , a burner tube having an upstream end and a downstream end , a fuel orifice located adjacent the upstream end of the burner tube for introducing gaseous fuel into the burner tube , a burner tip having an outer diameter mounted on the downstream end of the burner tube adjacent a first opening in the furnace , so that combustion of the gaseous fuel takes place downstream of the burner tip , and at least one non - gaseous fuel gun , the at least one non - gaseous fuel gun having at least one fuel discharge orifice for combusting the non - gaseous fuel downstream of the discharge orifice , wherein the at least one non - gaseous fuel gun is radially positioned beyond the outer diameter of the burner tip so that a flame emanating from the combustion of the non - gaseous fuel is substantially aligned in parallel with a flame emanating from the combustion of the gaseous fuel .