An FCC catalyst regeneration technique in which the catalyst is regenerated in a dense bed regenerator. Regenerator effluent gases are collected from different parts of the regenerator vessel in a common collection zone and passed through the catalyst separation cyclones from the common collection zone. Removal of nitrogen oxides from the regeneration effluent gases is enhanced by passing spent cracking catalyst through the effluent gases from a secondary spent catalyst inlet in the upper part of the regeneration vessel. Coke on the spent catalyst effects a reduction of nitrogen oxide (NOx) species in the effluent gases to nitrogen.