False deformation temperatures for ash fusibility associated with the conditions for ash preparation
Article
Wall, TF, Gupta, SK, Gupta, RP et al. (1999). False deformation temperatures for ash fusibility associated with the conditions for ash preparation
. 78(9), 1057-1063. 10.1016/S0016-2361(99)00017-4
Wall, TF, Gupta, SK, Gupta, RP et al. (1999). False deformation temperatures for ash fusibility associated with the conditions for ash preparation
. 78(9), 1057-1063. 10.1016/S0016-2361(99)00017-4
A study was made to investigate the fusibility behaviour of coal ashes of high ash fusion temperatures. Coals and ashes formed in the boiler were sampled in several Australian power stations, with laboratory ashes being prepared from the coals. The laboratory ashes gave lower values for the deformation temperature (DT) than the combustion ashes when the ash had low levels of basic oxide components. Thermo-mechanical analysis quantitative X-ray diffraction and scanning electron microscopy were used to establish the mechanisms responsible for the difference. Laboratory ash is finer than combustion ash and it includes unreacted minerals (such as quartz, kaolinite and illite) and anhydrite (CaSO4). Fusion events which appear to be characteristic of reacting illite, at temperatures from 900 to 1200 °C, were observed for the laboratory ashes, these being associated with the formation of melt phase and substantial shrinkage. The combustion ashes did not contain this mineral and their fusion events were observed at temperatures exceeding 1300 °C. The low DTs of coal ashes with low levels of basic oxides are therefore a characteristic of laboratory ash rather than that found in practical combustion systems. These low temperatures are not expected to be associated with slagging in pulverized coal fired systems.
