OCR Text |
Show reduction step, the amount of oxidation air and recycle quench required for each respective step will be less. The introduction of oxidation air into the quench section and the need for less quench recycle and oxidation air results in a 100% increase in residence time. Additionally, the average temperature in the oxidation zone will increase from 1700 ° F up to 2400 ° F. The combination of higher temperature and residence time will result in a significant increase in the destruction of H C N and C O with an insignificant increase in NO,. The catalytic reduction step was recommended to provide maximum NO, reduction with minimum excess fuel. A commercial demonstration test on IC engines at the University of San Diego cogeneration facility demonstrated N O , reductions in excess of 99.9% using this approach (7). The catalytic oxidation step was added because of the fixed residence time available in the oxidation zone of the existing equipment and for improved performance during non-steady-state operations. Allied-Signal, the catalyst supplier, estimates that the oxidation catalyst will provide an additional 8 0 % reduction in H C N , a 9 9 % reduction in CO, and a minimum overall destruction efficiency of 9 8 % for V O C s . A comparison of the original two-stage thermal system and the Hybrid Low N O , modification is presented in Table II. Table II Comparison of Two-Stage, Thermal System with Hybrid Low N O , Modification Fuel, Btu/hr Recycle, S C F M Oxidation AirA S C F M Emissions, ppm NQ, CO HCN VOC Two-Stage Thermal 10.22 4410 800 250-450' 1300-1700' 50-100' 75-150' Hvbrid Low NO, 7.49 3290 320 25-502 15-252 5-102 5-102 1 Measured emissions of two-stage thermal system 2 Expected emissions based on bench- and pilot-scale testing 7 111-16 |