NO_x emissions and precursors formation in pulverized biomass co-firing: Bench scale experiments

In The Netherlands, the Dutch government aims to enhance the energy production by cocombustion from 0.1 PJ in 1995 to 39 PJ in 2010. The aim of this work is to investigate in which way biomass cofiring and the adoption of air staging affects the in-flame NO_x formation. Bench scale pulverized fuel reactor experiments were carried at a furnace wall temperature of 1300°C. High volatile bituminous coal blend was fired as reference case. Chicken manure and olive cake were cofired with a target share of 20% _th. The NO_x emissions are considerable reduced when the stoichiometry in the primary zone equals to λ₁ = 0.7 - 0.9 for all cases. Chicken manure cofiring presents minimum NO_x levels comparable to those of the reference coal, in spite of higher nitrogen content. As to NO_x precursors evolution, HCN release shows similar patterns to the coal case, i.e. higher concentrations are achieved with lower stoichiometries. Different patterns are reported for ammonia, with higher yields recorded with intermediate stoichiometries of λ₁ = 0.89 and λ₁ = 0.79.