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Show As indicated in the equations, these reactions are reversible and controlled by chemical kinetics. If NO is present at concentrations greater than equilibrium values, it will be decomposed into N2 and O2 due to the high reverse reaction rates. Consequently, the net NOx production rate from combustion is reduced. Therefore, the thennodynamic-kinetic conditions could playa very important role in the NOx recycle approach. In addition, free radicals, such as CH+, CH2 +, NH+, and NH2 +, generated in the flame, especially in the fuel rich zone, might also serve to reduce NOx by their reactions with NO or N02. The NOx recycle concept is a key attribute of the NOXSO Process. The NOXSO Process is a dry, post-combustion flue gas treatment technology which can simultaneously remove 90% NOxlS02 by using a dry and regenerable sorbent. The sorbent, developed and patented by NOXSO Corporation, is a g-alumina sphere impregnated with sodium carbonate, Na2C03 on the surface of the sphere. It is stable, inert, non-toxic and noncombustible. In the NOXSO process, NOx and S02 are adsorbed in a fluidized bed of sorbent in an adsorber at a temperature of 120°C. The NOx is then desorbed by heating the sorbent in a heater and recycled back to the boiler to be reduced. S02 is regenerated at 620°C using a reducing gas and converted to a sulfur by-product in a Claus plant. After sulfur regeneration, the sorbent is cooled and transported to the adsorber for reuse. The NOXSO Process has completed the pilot-scale tests and is currently at the stage of commercialization [8]. EXPERIMENTAL RESULTS AND DISCUSSIONS In order to evaluate the feasibility of the NOx recycle concept, an experimental study utilizing simulated NOx recycle experiments have been performed on a 6 MMBtu/hr cyclone furnace at the Babcock & Wilcox (B&W) Research Center, funded by DOE and NOXSO Corporation. The schematic of the cyclone burner . is shown in Figure 3. In this study, the NOx recycle stream was simulated by a gas stream prepared from 6 |
