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Co-firing ammonia in coal-fired utility boilers is a promising de-carbon technical route for power stations, yet currently, there is still no information on how co-firing ammonia would affect the release and conversion of volatiles. Here, coal pellets were burned with/without ammonia co-firing on a flat-flame burner facility in both fuel-lean and -rich conditions. Detailed information on time-resolved evolution of volatile flame, size evolution of soot particles in flame, and changes in their physiochemical structures was obtained. It was observed that co-firing ammonia promoted devolatilization of coal and release of volatiles, leading to an earlier ignition moment in both fuel-lean and -rich conditions. In the flame, massive soot particles were formed from volatiles, and co-firing ammonia affected the conversion of volatiles into soot and changed the flame radiation properties. Interestingly, both the number density of all soot and size of primary soot particles increased after co-firing ammonia in fuel-lean conditions (by 2.5 times and ∼10 nm, respectively), while they decreased in fuel-rich conditions. In fuel-lean conditions, co-firing ammonia promoted inception and surface growth of soot due to competitive consumption of O 2 and increased flame temperature, while in fuel-rich conditions, these effects were offset by partial consumption of soot precursors by forming nitrogencontaining species. Furthermore, when ammonia was co-fired, fringe length, tortuosity, and especially inter-fringe spacing of soot increased slightly, indicating that particles formed in co-firing flames might show higher oxidation reactivity than those formed without ammonia co-firing.

Systemic field measurements of PM 10 were carried out on a grate-type municipal solid waste (MSW) incinerator to investigate the formation characteristics of PM 10 and the effects of a semi-dry flue gas deacidification scrubber (lime slurry spraying and activated carbon powder injection) and a baghouse on its emission. The particle size distribution (PSD), mass concentration, chemical composition, and micromorphology of PM 10 in the flue gas at the scrubber inlet, the scrubber outlet, and the baghouse outlet were comprehensively determined. The results showed that the PSD of PM 10 formed from MSW incineration was tri-modal. The peak of PM in the central mode (0.3−3 μm) was dramatically higher than that of either the ultrafine mode or the coarse mode, most possibly due to the high contents of volatile mineral matter (e.g., Na and Cl) and nanomaterial-/micro-material-containing wastes in the MSW fuels. The mass yields of PM 1 , PM 2.5 , and PM 10 decreased by 28.24, 59.26, and 53.91%, respectively, after passing through the semi-dry scrubber; however, some new particles formed from the slurry droplet. The baghouse could effectively remove the PM with the removal efficiencies for PM 1 , PM 2.5 , and PM 10 being over 99.95%. Comparatively speaking, more PM 2.5 was generated in the combustion of MSWs than agroforestry or coal in the furnace.

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