Reduction of gas phase reduced nitrogen species in partial burn FCC processes

摘要

Reduced emissions of gas phase reduced nitrogen species in the off gas of an FCC regenerator operated in a partial or incomplete mode of combustion is achieved by contacting the off gas with an oxidative catalyst/additive composition having the ability to reduce gas phase nitrogen species to molecular nitrogen and to oxidize CO under catalytic cracking conditions. The oxidative catalyst/additive composition is used in an amount less than the amount necessary to prevent afterburn. Fluidizable particles of the oxidative catalyst/additives are circulated throughout the partial or incomplete burn FCC unit along with the FCC catalyst inventory. The flue gas having a reduced content of gas phase reduced nitrogen species and NOx is passed to a downstream CO boiler, preferably a low NOx CO boiler. In the CO boiler, as CO is oxidized to CO2, a reduced amount of gas phase reduced nitrogen species is oxidized to NOx, thereby providing an increase in the overall reduction of NOx emitted into the environment.