Off-gas incinerator control

A process for operating an off-gas incinerator, the process comprising:

• introducing a flow of reactant stream into an ammoxidation reactor, wherein the reactant stream includes ammonia, an oxygen containing gas, and a hydrocarbon selected from the group consisting of propane, propylene, or mixtures thereof;
• determining amount of hydrocarbon in the reactant stream being introduced into the ammoxidation reactor and determining a feed rate of the reactant stream to the ammoxidation reactor, wherein a hydrocarbon conversion rate is about 95% to less than 100%;
• conveying a gaseous reactor effluent from the ammoxidation to a quench vessel to provide a quenched stream;
• conveying the quenched stream to an absorber wherein acrylonitrile is absorbed from the quenched stream with an aqueous solution;
• supplying an absorber off-gas from the absorber to an absorber off-gas incinerator, wherein the absorber off-gas has about 5 weight % or less water;
• supplying fuel gas and air to the absorber off-gas incinerator;
• and
• using the amount of hydrocarbon in the reactant stream being introduced into the ammoxidation reactor and the feed rate of the reactant stream to the ammoxidation reactor in a model predictive control system to adjust the fuel gas flow to the absorber off-gas incinerator and the air flow to the absorber off-gas incinerator in an amount effective for maintaining a temperature in the absorber off-gas incinerator within about 10° F. of a temperature set point of the off-gas incinerator and for providing about 5 volume % or less oxygen in the absorber off-gas incinerator,
• wherein the process maintains about 6 kg or less NOx in the absorber incinerator off-gas per ton of acrylonitrile produced.