Bio-Slag High-Temperature Corrosion on an Alumina Refractory under the Reducing Environment

Abstract

The alkali and alkaline earth metals in the biomass are one of the major challenges that restrict the biomass/low-rankcoal entrained-flow gasification in the way of ash slagging and corrosion. To clarify the corrosive behavior from bio-slag on the refractory material of the gasifiers, this study investigates the blending of biomass with coal for high-temperature corrosion on an alumina refractory in a vertical furnace under the reducing environment. The ash samples from a typical wheat straw (WS) and a Shenhua bituminous coal (SH), as well as their blends in three different mass ratios at 10 wt % WS, 30 wt % WS, and 50 wt % WS, were selected for high-temperature corrosion tests at 1350 °C for 2 h holding time. The obtained slag, especially the cross section, was examined using optical microscopy, scanning electron microscopy (SEM) coupled with energy-dispersive spectroscopy (EDS), and Raman spectral analysis. Additionally, the thermodynamic calculation was conducted using Factsage. The results show that the addition of WS into SH lowers the ash fusion temperature. The WS30 blends have the lowest ash fusion temperature with a fully molten phase at 1130 °C. The addition of WS promotes the slag fluidity, while adding 30% of WS into SH results in the largest spreading area. Interestingly, the slag with a higher fluidity is more corrosive, indicated by a larger filtrated area and depth in the cross section. Elemental mapping results show that the ash-forming elements are evenly distributed in the slag for fully melted samples. However, the Mg species precipitated near the slag-refractory interface and react with alumina to form a spinel phase that prevents further penetration.

High-Temperature Ash Melting and Fluidity Behavior upon the Cocombustion of Sewage Sludge and Coal

“…At 1200 °C, Ash A spread into a circular shape, indicating a significant degree of melting and sintering. Generally, from the optical macroscopy images, all the samples provide a shiny flat surface, indicating that the ash was fully melted with the molten phase . Furthermore, the liquid phase content gradually increased to 80%.…”

“…Generally, from the optical macroscopy images, all the samples provide a shiny flat surface, indicating that the ash was fully melted with the molten phase. 45 Furthermore, the liquid phase content gradually increased to 80%. Although a high liquid phase content caused the ash to shrink, the solid:liquid ratio did not cause the ash to flow on the aluminum sheet.…”

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

“…Only specific ash compositions’ interaction with the crucible can be studied using this method. Ji et al 13 also used Factsage to study the interactions of bioslags and an alumina refractory. Isothermal CaO–Al 2 O 3 –SiO 2 phase diagrams showed that at a fixed ratio of CaO/SiO 2 , the liquid phase proportion decreases as Al 2 O 3 increases.…”