Reduction kiln
Disclosed is a process for reducing metallic oxide or sulfide materials in a rotary kiln and a rotary kiln for reducing such materials. The materials are heated in a reducing atmosphere as they travel along the axial length of the rotary kiln. The materials are discharged from the kiln at a discharge point in the kiln away from its lower material outlet end, wherein the temperature within the kiln at said discharge point is greater than the temperature at the lower material outlet end.
1. A process for reducing metallic oxide or sulfide materials in a rotary kiln comprising a cylindrical shell having a material inlet end and a material outlet end, said process comprising
a) inserting the materials into the inlet end of a kiln and moving such materials from the inlet end through the kiln toward the outlet end;
b) introducing a reducing medium into the kiln, said reducing medium coming into contact with the materials as they move through the interior of the kiln;
c) heating the materials in said reducing medium as they travel through the kiln at a temperature sufficient to reduce at least some of the materials to free metal product, said materials moving through said reducing medium in a direction countercurrent to the direction of the flow of the reducing medium through the kiln; and
d) discharging materials from the kiln through an opening in the kiln shell at a first discharge point in the kiln which is, with reference to the direction of movement of the materials through the kiln from the inlet end toward the outlet end, located within the kiln at any point from where the temperature within the kiln begins to be greater than the temperature at the outlet end up to and including the point at which the temperature within the kiln is at its maximum, said discharge point being axially removed from the material outlet end.
2. The process of claim 1 wherein the temperature within the kiln at the first discharge point is the maximum temperature within the kiln.
3. The process of claim 1 where the materials to be reduced are nickel oxides.
4. The process of claim 1 further comprising separating material above a predetermined size from the materials discharged from the kiln at the discharge point, with said separated large material exiting the kiln at the material outlet end.
5. The process of claim 1 further comprising also discharging material through the kiln shell at a second discharge point located intermediate the first discharge point and the outlet end.
6. The process of claim 1 wherein the reducing material is a natural gas substantially free of any oxidizing gases.