Experimental study on ash fusion characteristics and slagging potential using simulated biomass ashes

• Published in: Journal of the Energy Institute Vol. 92; no. 6; pp. 1889 - 1896
• Main Authors: Zhu, Yiming, Tan, Houzhang, Niu, Yanqing, Wang, Xuebin
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.12.2019
• Subjects: Ash fusion; Biomass; Combustion; Long/short slag; Slagging; Long/short slag; Combustion; Biomass; Ash fusion; Slagging
• ISSN: 1743-9671
• DOI: 10.1016/j.joei.2018.11.005

Ash fusion characteristics (AFC) affect biomass slagging significantly. Due to the complexity of biomass ash composition, simulated ashes have been used for investigating AFC. Considering the practical ash components used in power plants, the mixture of SiO2, CaO, K2O and Al2O3 were used as simulated ashes. Deformation temperature (DT) changes remarkably as the ash components of biomass change, and thus is selected as an index. The results are presented by SiO2-CaO-K2O ternary diagrams with three different ratios of Al2O3. The ternary diagrams are divided as high-temperature zone (HZ, >1400 °C), medium-temperature zone (MZ, 900–1400 °C) and low-temperature zone (LZ, <900 °C). Results also show that without Al, low melting products (K4CaSi3O9) of the eutectic reactions among K2O, CaO and SiO2 led to a DT of 1290 °C in MZ. With the addition of Al2O3, DT can increase from LZ to MZ at high K content condition because Si-Al-K compounds such as KAlSi2O6 and KAlSi3O8 formed. However, DT decreased and moved from HZ to MZ with the addition of Al while Ca or Si content is high because of Si-Al-Ca compounds such as Ca2Al2SiO7 and CaAl2Si2O8. Besides, the difference (DSD) between deformation temperature and softening temperature has been used to predict the slagging potential. Long slag tends to occur in the zone of high K content, where SiO2 leads to a larger DSD than CaO does. Al2O3 can decrease DSD and form short slag, which is suitable as additive for relieving slagging. •Deformation temperature (DT) of ash is selected as an evaluation index of slagging for its remarkable change.•Eutectic reactions of SiO2-CaO-K2O in simulated ash lead to a moderate DT of 1290 °C.•Al2O3 has a two-way influence on DT with different ash composition.•Al2O3 is suitable as additive for relieving slagging during biomass combustion by forming short slag instead of long slag.