NO reduction studies in the FCC process. Evaluation of NO reduction additives for FCCU in bench- and pilot plant-scale reactors

During FCC catalyst regeneration, part of the nitrogen in coke forms NOx, which makes up a significant part of the total NO refinery emissions. The addition of a small percentage (less than or equal to 1 wt %) of catalytic additive(s) in the FCC inventory can reduce the NOx emissions from the flue gases of the FCC regenerator. In this paper, experimental techniques are considered for evaluating, in laboratory reactors, the performance of two commercially available NOx removal additives. It has been shown that in an FCC regenerator the gas residence time and the concentration of CO in the flue gases are key parameters in controlling NOx emissions. For example, pilot plant experiments showed that the addition of a CO oxidation promoter (CP-3) in the catalytic inventory decreases the CO emissions significantly and increases the NOx emissions about 4 times. Replacement of the active CO oxidation promoter (CP-3) with an additive (XNOx) with moderate CO oxidation activity reduced the NOx emissions by 78%. Comparison of regeneration results performed in bench-scale reactors with those measured in our FCC pilot plant unit showed that it is possible to evaluate NOx reduction additives in bench-scale experiments. The proposed protocol for this evaluation is to mix spent FCC catalyst with the NOx reduction additive and to load this mixture in a fluidized bed reactor. The above mixture is then regenerated at 700 degreesC by 2% O-2 dilated in. N-2.