Kinetic modeling of NOx reduction with by-product gases reburning

The surplus by-product fuels from steel plants, coke oven gas (COG), blast furnace gas (BFG), and Linz-Donawitz Converter Gas(LDG), can be used as the reburn fuel to lower NOx emission. Kinetic simulations were carried out to investigate the NOx reduction characteristic by these gases and their mixtures. BFG and LDG are primarily non-hydrocarbon fuels, which have a NOx reduction potential of 21-36% at the highest reburning temperature. Their NOx reduction potential monotonously increase with temperature and reburn fuel fraction. At similar conditions, COG can remove 87% of the nitric oxide and there is an optimum value for temperature and reburn fuel fraction to achieve the maximum NOx reduction. Conversion of NO to N₂ in the reburn zone of a high HC gas proceeds primarily through the following sequence: CH_i+NO→HCN+...→NH_i+...→N₂. A parameter study of the reduction ability of the COG/BFG mixture gas indicates that the optimum air/fuel ratio depends on the proportion of mixture.