NO reduction via reburning of MSW pyrolysis volatiles in cement precalciners

Cement co-processing of municipal solid waste (MSW) has been widely recognized as a promising waste management strategy. Given the substantial NO_x emissions from cement industries and the well-established NO_x reduction potential of hydrocarbon reburning, this study proposed a novel approach using MSW pyrolysis volatiles as a reburning fuel in cement precalciners, enabling both waste valorization and emission reduction. To confirm the applicability of this approach, the effects of pyrolysis parameters, reaction temperature, gas compositions, and cement raw meal were experimentally investigated in a simulated cement precalciner atmosphere. Results indicated that reaction temperatures and O₂ mole fractions jointly influenced NO reduction capacity, with lower O₂ levels preferred at higher reaction temperatures. Volatile products from lower pyrolysis temperatures (800 ℃) enabled higher NO reduction capacity at reaction temperatures below 1100 ℃ and O₂ mole fractions below 1%. However, this trend reversed as O₂ levels or reaction temperatures increased. MSW volatile products in a CO₂ atmosphere exhibited a reduced NO reduction capacity than in an Ar atmosphere, attributed to lower hydrocarbon yields, particularly at elevated pyrolysis temperatures. Furthermore, raw meal addition facilitated catalytic NO reduction by CO, CH_4, and NO precursors on the CaO surface under conditions of low or no O₂ and CO₂. The findings demonstrated the potential of MSW pyrolysis volatiles as an effective reburning fuel for synergistic waste management and NO_x emission control.