Efficient and cost effective reburning using common wastes as fuel and additives

Potential substitutes of natural gas and lignite fly ash as NO and HCN reducing agents, respectively, for heterogeneous reburning were examined in a bench-scale apparatus equipped with a simulated reburning and a burnout furnace. Selection of NO reducing agent is based on fuel volatility and nitrogen functionality. HCN reducing agent selection is based on literature data. A wide range of waste materials and industrial by-products show overall NO reduction efficiency up to 88% at reburning stoichiometric ratio 0.90 or 0.95. Mixed fuel containing scrap tire and Fe₂O₃ is particularly effective. Though its cost is constrained by the energy-intensive operation of grinding the tire, the estimated raw-material cost is better than that of natural gas reburning and highly competitive against SCR. A first-level approximation study of the selectivities of nitrogen species to form NO in burnout zone reveals the importance of HCN and char nitrogen reaction mechanisms.