Combustion of cattle biomass (CB) as a supplementary fuel has been proposed for reducing emissions of NOx, Hg, SO2, and nonrenewable CO2 in large coal-fired power plants. It has benefits to power industries for lowering coal consumption and fuel costs and to animal industries for disposing burdensome agricultural wastes from large animal feeding operations. In order to develop environmentally friendly thermo-chemical energy conversion technologies that can utilize CB for NOx and Hg reductions in existing coal-fired power plants, co-firing and reburning experiments involving CB and coal were performed in a small-scale 30 kWt (100,000 Btu/h) downward fired boiler burner facility. The co-firing results are mainly presented and discussed. Preliminary reburn results are also reported. The results show that the pulverized CB can serve as a supplementary fuel for the coal-fired boilers, and combustion of the CB with coals shows reductions in NOx and Hg emissions. It is believed that 1) most of the fuel-nitrogen in the CB existed in forms of NH3 or urea which led the high NOx reductions and 2) burning the CB containing high chlorine (Cl) produced large amounts of Cl species (mainly HCl) which oxidized the elemental Hg in the flue gas, hence the Hg emissions were reduced. The equivalence ratio (φ), an inverse value of the stoichiometric ratio, was considered as a key parameter to achieve high NOx reductions. Higher NOx and Hg reductions were measured under fuel-rich conditions (φ > 1.0). It appeared that the effect of the unburned carbon (UBC) was much stronger on the Hg reductions than that of Cl.

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