Effect of Coal Ash Composition on Ash Fusion Temperatures^†

Abstract

The ash fusion temperatures (AFTs) of coal mineral matter at high temperature are important parameters for all gasifiers. Experiments have been conducted in which mixtures of selected coal ashes and SiO 2 , Al 2 O 3 , CaO, Fe 2 O 3 , and MgO were subjected to the standard test for ash fusibility. The computer software package FactSage has been used to calculate the liquidus temperatures of coal ash samples and the proportions of the various phases present as a function of temperature. The results show that the AFTs of coal ash samples first decrease with increasing CaO, Fe 2 O 3 , and MgO contents, then reach a minimum value, before increasing once more. However, for the effect of S/A ratio, its AFTs are always increased with increasing S/A ratios. The measured AFTs all show variations with mixture composition that correlated closely with liquidus temperatures for the appropriate pseudoternary phase diagrams. The liquidus and AFTs generally showed parallel compositional trends but are displaced from each other because of the influence of additional basic components in the coal ash. The liquidus temperatures of coal ash samples are always higher than its AFTs.

Measurement and simulation of flow properties of coal ash slag in coal gasification

“…Liquid temperature of the slag was determined for the mineral matter that it contained. 46 On the basis of the oxide composition of the slag, the proportion of liquid phase generated and the compositions of remaining liquid phase were evaluated at different temperatures. FactSage is a thermodynamic equilibrium model.…”

Effects of SiO2/Al2O3 Ratios on Sintering Characteristics of Synthetic Coal Ash

“…Earlier studies have explored the influence of components on ash fusibility or viscosity [20][21][22], but not much data is available on sintering characteristics. It has been concluded that high SiO 2 /Al 2 O 3 ratios (S/As) and low concentrations of basic oxides account for the high ash fusion temperatures of most Australian bituminous coal ashes [23].…”

Slag Behavior in Gasifiers. Part I: Influence of Coal Properties and Gasification Conditions

“…Under oxidizing conditions, the ratio of SiO 2 and CaO is most strongly correlated with temperature. Song et al [60] investigated CaO, Fe 2 O 3 , and MgO on fusion temperatures under argon using the thermodynamic computer package FactSage. The fusion temperatures of coal ash decrease with increasing CaO, Fe 2 O 3 , and MgO contents then increase after reaching a minimum; for example, when CaO is higher than 35% the fusion temperature increases rapidly [50].…”