Yielding Conditions for Fiber Materials from Coal Ash Slag

In this study, we focused on optimizing a part of the furnace and operating conditions of the fiber yielding system from fused coal ash to expand ash utilization for building materials; promotion of ash use is desirable because slag inhibits the elution of toxic heavy metals, such as Hg, Pb and As, to undetectable levels, making the fibers safe to use. In particular, the fiber materials from coal ash slag are expected to be used as thermal insulators and acoustic materials. We designed a coal ash fusing furnace which is suitable for the fiber manufacturing and recovery process. To manufacture fiber materials which are both safe and homogeneous, the slag viscosity had to be stabilized to approximately 1 Pa·s at the slag-tapping hole of the furnace. However, the slag temperature at 1 Pa·s was too high to measure. Thus, we estimated the slag temperature at 1 Pa·s using Riboud’s and Urbain’s expressions. To control the slag viscosity and temperature, CaCO3 addition to coal ash was effective. When the basicity (CaO/SiO2(wt%/wt%)) of the coal ash sample was 0.98, the fused slag temperature at 1 Pa·s was estimated as 1563 °C. Then, we verified that to yield 1 Pa·s fusing slag from 120 kg/h coal ash, the necessary fuel quantity of the coal ash fusing furnace was 40 kg/h coal and 4 m3N/h LPG.