Air and Fuel Staged Co-combustion of Coal with Biomass in Power Station Boilers

The overall objective of this investigation is to develop a technology to employ biomass as substitute fuel for coal to help reduce NOx.. It was achieved by governing NOx formation kinetics through in-furnace air and fuel staged co-combustion technology. An extensive series of experimentation was carried out in a 20 kW down fired combustor to evaluate the effect of co-firing of Shea meal, Cotton stalk and Wood chips on NOx emissions and combustion efficiency. Shea meal, Cotton stalk and Wood chips were cofired under unstaged, airstaged and fuelstaged (Reburning) configurations. For air staging, optimum value of primary zone stoichiometry SR1=0.9 was kept fix and, biomass blending ratio (BBR) was varied 5%, 10% 15% on thermal basis. A BBR of 10% was found optimum yielding a NO reduction (%) of 51%, 60% and 53% for Shea meal, Cotton Stalk and Wood chips respectively. The lengths of the reburn zone and burnout zone were kept fix during fuel staging experiments. Shea meal, Cotton stalk and Wood chips were evaluated as reductive fuel using different reburn fuel fractions (Rff) and reburn zone stoichiometry (SR2) values. A reburn fuel fraction of 15% (thermal) was found to be optimum for Shea meal Cotton stalk and Wood chips displaying a NO reduction of 83%, 84% and 75% at an optimum reburn zone stoichiometry (SR2) of 0.83,0.82 and 0.8 respectively.