A method for utilizing the in the case of the catalytic oxidation of o - xylene resulting reaction warmth

摘要

A process for utilization of the reaction heat generated by the catalytic oxidation of o-xylene with air to phthalic anhydride in a tubular reactor, which heat is partially carried away from the reactor by the reaction gas and partially by fused salt used as a cooling medium. Water is heated by heat exchange with the hot reaction gas, evaporated by heat exchange with the fused salt and the steam is superheated and expanded in a condensation turbine coupled with the feed air compressor. The hot reaction gas is used successively to heat, or evaporate, a heat carrier liquid serving for the heating of the phthalic anhydride distillation, and the pressurized water. Low pressure steam can be generated by heat exchange of pressurized water with the reaction gas and used for heating the feed air and/or o-xylene. Preferably, the evaporation and superheating of the heated pressure water is effected in two fused salt cooling stages; the compressed air is successively heated by heat exchange with low pressure steam generated by cooling of the reaction gas and with the high pressure steam generated by cooling of the fused sa and, the heating liquid and the pressurized water are heated in a two-stage heat exchanger.