Refuse-derived fuel and integrated calcium hydroxide sorbent for coal combustion desulfurization

Pelletized refuse-derived fuel (RDF; 65 wt % nonrecyclable fibers/plastics) and integrated calcium hydroxide sorbent (35 wt %), referred to as a ReEngineered Feedstock (ReEF), were evaluated as a renewable fuel and an in situ sulfur sorbent within pulverized coal combustion. Characterization of ReEF with scanning electron microscopy-energy-dispersive X-ray spectroscopy indicated random distribution of calcium hydroxide sorbents on fiber/plastic particles. The sulfation kinetics of ReEF combustion were evaluated in a drop-tube reactor at variable conditions (800-1000 °C, 1400 ppm of SO₂, and 5-30% O₂ in N₂) with continuous effluent characterization via online IR spectroscopy. Sulfation of calcium hydroxide in ReEF was delayed because of RDF combustion when compared with pure calcium hydroxide sorbent. A low-O₂ condition was shown to produce high conversion of calcium hydroxide to calcium sulfate X(_Ca(OH)2) > 0.4), while calcination and combustion of ReEF in a high-O₂ environment (O₂ > 20%) resulted in increased sorbent sintering and reduced total sulfur uptake.