TY - JOUR
T1 - Ignition and combustion characteristics of single particles of Zhundong lignite
T2 - Effect of water and acid washing
AU - Zhang, Zhezi
AU - Zhu, Mingming
AU - Zhang, Yang
AU - Setyawan, Hendrix Y.
AU - Li, Jianbo
AU - Zhang, Dongke
PY - 2017
Y1 - 2017
N2 - The ignition and combustion characteristics of Zhundong lignite (ZDL), with and without washing to remove different forms of inherent sodium, were investigated. Water washed (ZDL-WW) and acid washed (ZDL-AW) samples were prepared by soaking the raw lignite (ZDL-Raw) in ultrapure water and 0.5 M hydrochloric acid (HCl), respectively, at 60°C for 24 h. A single particle of a ZDL sample, ca 2.5 mm in diameter, was suspended on a silicon carbide fibre (142 μm) tip and burned in air at 1123 K in a furnace. The time-resolved ignition and combustion behaviours of the single particles were observed with the aid of combined use of a shortwave infrared camera, a CCD camera, which enabled the determination of the ignition mechanism, ignition time, burnout time and burning rate. A flame emission spectrometer was used to identify the presence of sodium in the flame. The ignition of all ZDL samples followed the joint hetero-homogeneous mechanism in the present work. Upon the homogeneous ignition, ZDL-Raw exhibited a soot free yellowish translucent flame while ZDL-WW and ZDL-AW showed sooty flames. The ignition time followed the order of ZDL-Raw>ZDL-WW>ZDL-AW while the burning rate followed the opposite order. These observations were attributed to the catalytic effect of sodium in the lignite whose amount was varied due to the water and acid washing. Sodium ions were detected in the flame of ZDL with and without washing and the intensity of sodium signal also followed the order of ZDL-Raw>ZDL-WW>ZDL-AW. It is believed that sodium ions released in the flame promoted catalytic cracking of large tar fragments and oxidation of soot precursors.
AB - The ignition and combustion characteristics of Zhundong lignite (ZDL), with and without washing to remove different forms of inherent sodium, were investigated. Water washed (ZDL-WW) and acid washed (ZDL-AW) samples were prepared by soaking the raw lignite (ZDL-Raw) in ultrapure water and 0.5 M hydrochloric acid (HCl), respectively, at 60°C for 24 h. A single particle of a ZDL sample, ca 2.5 mm in diameter, was suspended on a silicon carbide fibre (142 μm) tip and burned in air at 1123 K in a furnace. The time-resolved ignition and combustion behaviours of the single particles were observed with the aid of combined use of a shortwave infrared camera, a CCD camera, which enabled the determination of the ignition mechanism, ignition time, burnout time and burning rate. A flame emission spectrometer was used to identify the presence of sodium in the flame. The ignition of all ZDL samples followed the joint hetero-homogeneous mechanism in the present work. Upon the homogeneous ignition, ZDL-Raw exhibited a soot free yellowish translucent flame while ZDL-WW and ZDL-AW showed sooty flames. The ignition time followed the order of ZDL-Raw>ZDL-WW>ZDL-AW while the burning rate followed the opposite order. These observations were attributed to the catalytic effect of sodium in the lignite whose amount was varied due to the water and acid washing. Sodium ions were detected in the flame of ZDL with and without washing and the intensity of sodium signal also followed the order of ZDL-Raw>ZDL-WW>ZDL-AW. It is believed that sodium ions released in the flame promoted catalytic cracking of large tar fragments and oxidation of soot precursors.
KW - Ignition
KW - Sodium
KW - Volatile flame
KW - Washing
KW - Zhundong lignite
UR - http://www.scopus.com/inward/record.url?scp=85008627688&partnerID=8YFLogxK
U2 - 10.1016/j.proci.2016.07.072
DO - 10.1016/j.proci.2016.07.072
M3 - Article
AN - SCOPUS:85008627688
SN - 1540-7489
VL - 36
SP - 2139
EP - 2146
JO - Proceedings of the Combustion Institute
JF - Proceedings of the Combustion Institute
IS - 2
ER -