A system for controlling a tuyere, the tuyere comprising: an inner tube including a lower section having a first diameter, an upper section having a second diameter that is smaller than the first diameter, and a converging transition section having a converging angle Θ from 30° to 60° connecting the inner tube lower section to the inner tube upper section, the inner tube terminating in an inner nozzle at a downstream end of the inner tube upper section; and an outer tube surrounding the inner tube so as to create an annulus therebetween, the outer tube including a lower section having a third diameter that is larger than the first diameter, an upper section having a fourth diameter that is smaller than the third diameter but larger than the second diameter, and a converging transition section having connecting the outer tube lower section to the outer tube upper section, the outer tube terminating in an outer nozzle at a downstream end of the outer tube upper section; the system comprising said tuyere, wherein the system further comprises: a first inert gas valve configured to supply an inert gas to the inner tube and a fuel valve configured to supply a fuel to the inner tube; a second inert gas valve configured to supply an inert gas to the outer tube and an oxidant valve configured to supply an oxidant to the outer tube; and a controller programmed to operate the tuyere in a stirring mode or a burner mode, wherein in the stirring mode the first inert gas valve and the second inert gas valve are open while the fuel valve and the oxidant valve are closed, and wherein in the burner mode the fuel valve and the oxidant valve are open while the first inert gas valve and the second inert gas valve are closed; so that the tuyere is operable in two modes, a stirring mode in which a jet formed by the tuyere is in the jetting mode with an expansion Mach number from greater than 1.25 to 2 and a burner mode in which a stable non-premixed flame is formed to enable clearing of any blockage of the inner nozzle or the outer nozzle. an inner tube including a lower section having a first diameter, an upper section having a second diameter that is smaller than the first diameter, and a converging transition section having a converging angle Θ from 30° to 60° connecting the inner tube lower section to the inner tube upper section, the inner tube terminating in an inner nozzle at a downstream end of the inner tube upper section; and an outer tube surrounding the inner tube so as to create an annulus therebetween, the outer tube including a lower section having a third diameter that is larger than the first diameter, an upper section having a fourth diameter that is smaller than the third diameter but larger than the second diameter, and a converging transition section having connecting the outer tube lower section to the outer tube upper section, the outer tube terminating in an outer nozzle at a downstream end of the outer tube upper section; the system comprising said tuyere, wherein the system further comprises: a first inert gas valve configured to supply an inert gas to the inner tube and a fuel valve configured to supply a fuel to the inner tube; a second inert gas valve configured to supply an inert gas to the outer tube and an oxidant valve configured to supply an oxidant to the outer tube; and a controller programmed to operate the tuyere in a stirring mode or a burner mode, wherein in the stirring mode the first inert gas valve and the second inert gas valve are open while the fuel valve and the oxidant valve are closed, and wherein in the burner mode the fuel valve and the oxidant valve are open while the first inert gas valve and the second inert gas valve are closed; so that the tuyere is operable in two modes, a stirring mode in which a jet formed by the tuyere is in the jetting mode with an expansion Mach number from greater than 1.25 to 2 and a burner mode in which a stable non-premixed flame is formed to enable clearing of any blockage of the inner nozzle or the outer nozzle. a first inert gas valve configured to supply an inert gas to the inner tube and a fuel valve configured to supply a fuel to the inner tube; a second inert gas valve configured to supply an inert gas to the outer tube and an oxidant valve configured to supply an oxidant to the outer tube; and a controller programmed to operate the tuyere in a stirring mode or a burner mode, wherein in the stirring mode the first inert gas valve and the second inert gas valve are open while the fuel valve and the oxidant valve are closed, and wherein in the burner mode the fuel valve and the oxidant valve are open while the first inert gas valve and the second inert gas valve are closed; so that the tuyere is operable in two modes, a stirring mode in which a jet formed by the tuyere is in the jetting mode with an expansion Mach number from greater than 1.25 to 2 and a burner mode in which a stable non-premixed flame is formed to enable clearing of any blockage of the inner nozzle or the outer nozzle.