Reburning of Cattle Manure-Based Biomass With Coals in a Small Scale Boiler Burner Facility for NO_x and Hg Reduction

Reburning of cattle manure-based biomass (CB) with coals is performed to develop environmentally friendly thermo-chemical energy conversion technologies for NO_x reductions and Hg captures and removals from existing pulverized coal-fired power plants. A small-scale (30 kWth) down-fired boiler burner facility has been used for burning most types of pulverized solid fuels including coal and biomass. Blends of CB and coals are used as reburn fuels. It has hypothesized that a major fraction of the fuel-N in the CB is released in the form of NH3 or urea. In the reburn process, therefore, it is believed that NOx produced by coal is reduced to molecular nitrogen by NH3 released from the pyrolysis of CB under slightly fuel-rich conditions. The CB also contains larger amounts of chlorine (Cl) than most types of coals. Hence gaseous mercury (Hg) in the flue gas is oxidized by large amounts of Cl species mainly from the CB combustion. Consequently, the results indicate that the CB can serve as a very effective fuel supplementing coals on NOx reductions and Hg captures and removals in pulverized coal-fired boilers. It was also found that the auto-gasification occurred during the pyrolysis due to the oxygen available in the fuel mainly helped for burning fixed carbon.