Patent ID: 8061888

Claim:
A method for processing a feed stream, comprising: (a) introducing the feed stream into a stirred tank reactor, the feed stream being a slurry of solid metal-containing particles, the stirred tank reactor comprising a plurality of compartments, a plurality of agitators positioned in the plurality of compartments, and a plurality of dividers separating the plurality of compartments, each of the dividers including at least one underflow opening; (b) introducing a molecular oxygen-containing gas into the stirred tank reactor; and (c) passing at least most of the feed stream between sets of adjacent compartments through the at least one underflow opening in the respective divider separating the adjacent compartments, wherein a cumulative cross-sectional area of the at least one underflow opening in each of the dividers is different from a cumulative cross-sectional area of the at least one underflow opening in each of the other dividers to maintain a difference in liquid levels between sets of adjacent compartments in the range of from about 5 to about 150 mm.