Abstract: A method of converting a charge of non-ferrous metal matte in a Pierce-Smith or similar converter. The fluid charge is blown with a total flow of oxidizing gas effective to maintain autogenous converting temperatures through a plurality of spaced-apart tuyeres limited in number and individual cross-sectional area effective to maintain the gas underexpanded at a pressure within the range from about 50 to about 150 psig so that it penetrates the bath in the form of discrete steady jets to positions remote from the tuyere tips thereby reducing degradation of the refractories and build up of accretions. The gas is injected through from three to six tuyeres.

Abstract: Molybdenite or MoS.sub.2 materials, particularly finely divided flotation concentrates, are oxidized (roasted) to form molybdenum trioxide in a continuous composite fluidized bed containing non-elutriated refractory solids. A relatively high recycle ratio of oxidized calcine to feed is maintained for best results. The temperature of the circulated oxidized solids is maintained high to avoid sticking and deposition problems. High throughputs and high conversions have been achieved, with the product having a low sulfur content.

Abstract: A method of converting a charge of non-ferrous metal matte in a Pierce-Smith or similar converter. The fluid charge is blown with a total flow of oxidizing gas .Iadd.containing up to about 40% oxygen .Iaddend.effective to maintain autogenous converting temperatures through a plurality of spaced-apart tuyeres limited in number and individual cross-sectional area effective to maintain the gas underexpanded at a pressure within the range from about 50 to about 150 psig so that it penetrates the bath in the form of discrete steady .Iadd.unshielded .Iaddend.jets to positions remote from the tuyere tips thereby reducing degradation of the refractories and build up of accretions. The gas is injected through from three to six tuyeres.