Abstract: A method of stabilizing a fluidized bed in a fluidized bed roasting process for metal sulphide concentrate comprises the step of controlling the particle size distribution of the particulate material in the bed so that a minimum amount of no less than about 30% of the concentrate falls in a size range of from about 100 to about 420 microns. The minimum amount preferably falls in the range of from about 35% to about 40%. In one embodiment of the invention the particle size distribution is controlled by maintaining the amount of lead in the concentrate in a range from about 3% to about 4%, preferably 3.7% to about 3.8%. In another embodiment the particle size distribution is controlled by using a pelletized feed or by the combination of the steps of using a pelletized feed and regulating the lead content of the concentrate.

Abstract: A self-cooling lance or tuyere for the conveying of gases, liquids or solids into or onto a metallurgical bath comprises a heat pipe or thermosiphon made of two tubular members adapted to be immersed in a furnace environment at one end, such tubular members defining a closed annular chamber therebetween for containing a working substance adapted to evaporate in the region of the heat pipe which is in the furnace environment and flow toward the end which is out of the hot environment where it condenses and flows back to the evaporator region. Means are provided for introducing the gases, liquids or solids to be conveyed into the bath through the inner tubular member of the lance.