PM 10 formation during the combustion of N 2 -char and CO 2 -char of Chinese coals Chang Wen a , Minghou Xu a,⇑ , Dunxi Yu a,⇑ , Changdong Sheng b , Hongwei Wu c , Ping’an Zhang a , Yu Qiao a , Hong Yao a a State Key Laboratory of Coal Combustion, Huazhong University of Science and Technology, Wuhan 430074, China b School of Energy and Environment, Southeast University, Nanjing 210096, China c Fuels and Energy Technology Institute and Department of Chemical Engineering, Curtin University of Technology, G.P.O. Box U1987, Perth, Western Australia 6845, Australia Available online 5 September 2012 Abstract The formation of PM 10 (particles less than or equal to 10 lm in aerodynamic diameter) during char combustion in both air-firing and oxy-firing was investigated. Three Chinese coals of different ranks (i.e., DT bituminous coal, CF lignite, and YQ anthracite) were devolatilized at 1300 °C in N 2 and CO 2 atmosphere, respectively, in a drop tube furnace (DTF). The resulting N 2 -chars and CO 2 -chars were burned at 1300 °C in both air-firing (O 2 /N 2 = 21/79) and oxy-firing (O 2 /CO 2 = 21/79). The effects of char properties and combustion conditions on PM 10 formation during char combustion were studied. It was found that the formation modes and particle size distribution of PM 10 from char combustion whether in air-firing or in oxy-firing were similar to those from pulverized coal combustion. The significant amounts of PM 0.5 (particles less than or equal to 0.5 lm in aerodynamic diameter) generated from combustion of various chars suggested that the mineral matter left in the chars after coal devolatilization still had great contributions to the formation of ultrafine particles even during the char combustion stage. The concen- tration of PM 10 from char combustion in oxy-firing was generally less than that in air-firing. The properties of the CO 2 -chars were different from those of the N 2 -chars, which was likely due to gasification reactions coal particles experienced during devolatilization in CO 2 atmosphere. Regardless of the combustion modes, PM 10 formation in combustion of N 2 -char and CO 2 -char from the same coal was found to be significantly dependent on char properties. The difference in the PM 10 formation behavior between the N 2 -char and CO 2 -char was coal-type dependent. Ó 2012 The Combustion Institute. Published by Elsevier Inc. All rights reserved. Keywords: Oxy-fuel combustion; Pulverized coal; Char combustion; PM 10 formation 1. Introduction China is facing serious public health risks from the pollution by fine particulate matter (PM) from various sources including coal-fired boilers, diesel vehicles, and so on. PM has become the principal air pollutant in most Chinese major cities [1,2]. 1540-7489/$ - see front matter Ó 2012 The Combustion Institute. Published by Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.proci.2012.07.080 ⇑ Corresponding authors. Fax: +86 27 87545526 (M. Xu), +86 27 87542417 (D. Yu). E-mail addresses: mhxu@mail.hust.edu.cn (M. Xu), yudunxi@hust.edu.cn (D. Yu). Available online at www.sciencedirect.com Proceedings of the Combustion Institute 34 (2013) 2383–2392 www.elsevier.com/locate/proci Proceedings of the Combustion Institute