A multistage NOx reduction process for a FCC regenerator

NOx emission from a fluid catalytic cracking (FCC) regenerator is of environmental concern. A new NOx reduction technology that comprised only a simple change in the configuration and operating condition of a commercial FCC regeneration process was proposed. NO reduction by CO in a lab scale fluidized bed reactor under simulated FCC regeneration conditions was investigated. The results indicated that a multistage regenerator would give a higher efficiency for NO reduction than a single stage regenerator. The conversion of NO was increased to 90% in a multistage regenerator as compared to 50% in a single stage regenerator under the same operation conditions. The carbon content of the regenerated catalyst was less than 0.02 wt%. In the range of 400-700 degrees C, a higher temperature gave more NO conversion to N-2. The O-2 and CO concentrations were crucial factors that affected the conversion of NO. The catalyst in the FCC process limits the use of the regeneration temperature to less than 700 degrees C and mole ratio of O-2/CO to less than 0.25% in the reduction stage of the regenerator. A phase diagram of the NO + O-2 + CO reaction was obtained that was divided into a slow reaction zone and a rapid reaction zone. The regenerator can also be used as a flue gas denitrification facility located downstream of the catalyst regenerator or a coal-burning boiler to reduce the NO concentration in the flue gas to under 20 ppm. (C) 2011 Elsevier B.V. All rights reserved.