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

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 degrees C), medium-temperature zone (MZ, 900-1400 degrees C) and low-temperature zone (LZ, <900 degrees 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 degrees C in MZ. With the addition of Al2O3, DT can increase from 12 to MZ at high K content condition because Si-Al-K compounds such as KAISi(2)O(6) and KAISi(3)O(8) 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. (C) 2018 Energy Institute. Published by Elsevier Ltd. All rights reserved.