Non-catalytic reduction and oxidation process for the removal of NOx

A process for reducing NOx concentrations in the regenerator off-gas stream of a fluid catalytic cracking unit, which stream contains both NOx and SOx species, which process comprises:

• a) forming a mixture of a reducing agent selected from ammonia, urea and mixtures thereof, and a first readily-oxidizable gas in effective amounts that will result in the reduction of the NOx concentration of the regenerator off-gas by a predetermined amount;
• b) injecting said mixture into said regenerator off-gas at a first injection point wherein the regenerator off-gas is at a temperature between about 1200° F. and 1600° F.;
• c) injecting an additional amount of a second readily-oxidizable gas at a second injection point downstream of the first injection point in an amount effective to further reduce the amount of NOx concentration of the regenerator off-gas and to reduce the concentration of the reducing agent in the regenerator off-gas forming a reduced regenerator off-gas stream;
• d) removing at least a fraction of the SOx species from said reduced regenerator off-gas stream in a first reaction zone thereby producing a SOx depleted off-gas stream;
• e) contacting said SOx depleted off-gas stream in a second reaction zone with an effective amount of a treating solution comprised of sodium hypochlorite and an oxidant selected from sodium chlorite and chlorine dioxide at conditions that will oxide at least a fraction of the sulfites in said SOx depleted off-gas stream to sulfate and oxidize at least a fraction of the oxidizable NOx species in said SOx depleted off-gas stream to higher nitrogen oxides to produce a NO depleted off-gas stream;
• and
• f) contacting said NO depleted off-gas stream in a third reaction zone with an effective amount of an absorption solution comprised of the waste gas scrubber slurry solution from the bottom collection zone of a wet gas scrubber at conditions that will absorb at least a portion of the NO2 in said NO depleted off-gas stream to produce a treated regenerator off-gas stream.