Patent ID: 8790601

Claim:
A system for producing a polycarboxylic acid by contacting a slurry with a gas-phase oxidant, said system comprising: a primary oxidation reactor comprising a first slurry outlet; and a secondary oxidation reactor comprising a slurry inlet, a second slurry outlet, a normally lower oxidant inlet, and a normally upper oxidant inlet, wherein said slurry inlet is in downstream fluid-flow communication with said first slurry outlet, said secondary oxidation reactor defines therein a secondary reaction zone having a maximum length L s , said normally lower oxidant inlet is spaced from the bottom of said secondary reaction zone by less than 0.5L s , said normally upper oxidant inlet is spaced from the bottom of said secondary reaction zone by at least 0.5L s , said normally upper oxidant inlet and said normally lower oxidant inlet define between them a total open area for introducing said gas-phase oxidant into said secondary reaction zone, wherein said normally upper oxidant inlet defines in the range of from about 5 to about 49 percent of said total open area.