Characteristic of Particulate Matter from Combustion of Zhundong Lignite: A Comparison between Air and Oxy-fuel Atmospheres
2019
Ruan, Renhui | Tan, Houzhang | Wang, Xuebin | Yang, Fuxin | Hu, Zhongfa | Ren, Zijun
The transformation of sodium to particulate matter (PM) during lignite combustion has been widely investigated, while the importance of Ca, Mg, S, and Fe in low-rank coal has been recently revealed. In this study, three kinds of Zhundong lignites (ZD, YH, and HSY) rich in Na, Mg, Ca, S, and Fe were selected and the combustion was conducted in an entrained flow reactor with a furnace temperature of 1473 K. PM was sampled by a Deakti low-pressure impactor (DLPI), and the components were analyzed by scanning electron microscopy equipped with energy-dispersive X-ray spectrometry (SEM–EDS), with the PM number concentration measured by a scanning mobility particle sizer (SMPS). The characteristics of PM under air and oxy-fuel (Oxy21, Oxy30, and Oxy40) atmospheres were compared. The results show that the comparable O₂ concentration is related to coal properties and located between 30 and 40% for Zhundong lignite. It is acceptable to take the PM₁₀ mass yield as a reference to reflect the combustion intensity. An oxy-fuel atmosphere has more effect on PM₁–₁₀ than PM₁. The participation of Na in PM₁ is highest under Oxy21 combustion, which is enhanced through S and Cl. An increasing O₂ concentration will intensify the fragmentation and decomposition of Ca-, Mg-, Fe-, and Si-bearing minerals, which contribute mostly to the production of PM₁–₁₀. The contents of Si–Al-bearing minerals in raw coal significantly affect the contribution of Fe and S on PM₁–₁₀ through eutectic formation. Besides, the vaporization of inorganic elements (mostly Ca, Mg, Fe, and Si) will also be enhanced under oxy-fuel combustion at a higher O₂ concentration, increasing the PM₁ production and moving the number-based particle size distribution (NPSD) toward a larger particle size.
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