This document contains a flow sheet for the production of phthalic anhydride from the oxidation of o-xylene. It includes a key for the codes used to identify 29 pieces of equipment in the process. The equipment includes storage tanks, conveyor belts, packing equipment, bins, screw conveyors, spray towers, pumps, accumulators, condensers, reboilers, distillation towers, reactors, heat exchangers, blowers, air filters and vaporizers.