Influence of the Slag–Crucible Interaction on Coal Ash Fusion Behavior at High Temperatures

Abstract

Traditional ash fusion behavior is described by four characterization temperatures determined by shape of variation ash cone, cylinder, or cubes. The results by thermomechanical analysis (TMA) describe the whole fusion process, which supports the better understanding of the ash fusion process. However, the interaction between slags and the crucible at high temperatures is the key factor on the accuracy of the TMA measurement. In this work, the influence of the interaction between slags and different crucible materials, including platinum (Pt), alumina (Al2O3), zirconia (ZrO2), graphite (C), and molybdenum (Mo), on TMA results and its mechanism was investigated. The slag–crucible interaction includes diffusion and reaction mechanisms, and the interaction with Al2O3 and ZrO2 crucibles is controlled by the diffusion process of slags into the crucible wall. The Al2O3 crucible is as stable as Pt and has no obvious effect on the ash fusion process as a result of its compact structure and stable crystal form. The ZrO2 crucible becomes porous during heating and cooling as a result of crystal transition, which results in the penetration of melted slags into the crucible. ZrO2 can also diffuse into slags, and the diffusion rate is enhanced by sodium in slags. Both C and Mo crucibles are reactive with iron-containing slags; the interaction with the C crucible is related to the iron content of ashes; and the interaction with the Mo crucible is accelerated by the basic oxides (e.g., Na2O, CaO, and Fe2O3) in coal ashes. To obtain an accurate result of ash fusion behavior by TMA, especially for ashes with high basic oxide contents, the Al2O3 crucible is strongly recommended to avoid the slag–crucible interaction.

Application of Liquidus Projections in SiO2–Al2O3–CaO Systems with Fe2O3 and V2O5 to Study the Dissolution of Alumina Crucibles in Gasification Slags Containing Vanadium

“…Mo crucibles can also react with coal ash slag. 9 Coal ash fusion behavior was studied in crucibles of several materials, including Al 2 O 3 and Mo (Li et al 10 ). It was concluded that Mo crucibles can react adversely with basic oxides such as Na 2 O, CaO, and Fe 2 O 3 in coal ashes.…”

The wetting process and crystallisation of Al2O3 substrate with molten slags: Addition of CaO‐Fe2O3

“…Corundum exhibits outstanding slag resistance in many types of materials. It is a relatively ideal material for the study of wettability and has potential for industrial applications 25–31 . Herein, the wettability of CaO‐ and Fe 2 O 3 ‐modulated coal ash on corundum substrates is investigated, and the morphology of the wetted slag is evaluated.…”

“…It is a relatively ideal material for the study of wettability and has potential for industrial applications. [25][26][27][28][29][30][31] Herein, the wettability of CaO-and Fe 2 O 3 -modulated coal ash on corundum substrates is investigated, and the morphology of the wetted slag is evaluated. The effects of the CaO/Fe 2 O 3 ratio on the slag's internal structure and crystal composition are clarified along with the alterations in the wettability of the crystalline compounds and wettability during slag spreading with different CaO/Fe 2 O 3 ratios.…”

Virtual Special Issue of 2019 International Symposium on Clean Energy and Advanced Carbon Materials (CEAM-2019)

“…Li et al 5 conducted systematic research on limestone attrition and product layer development during fluidized-bed sulfation. Li et al 6 studied the influence of the slag−crucible interaction on coal ash fusion behavior at high temperatures. Hui et al 7 reported their improved understanding of the formation of the plastic layer during heating of Australian coking coal blends using three-dimensional image analysis techniques.…”