Toward Stable Operation of Coal Combustion Plants: The Use of Alumina Nanoparticles to Prevent Adhesion of Fly Ash

In pulverized coal combustion plants, low-grade sub-bituminous coal is known to cause adhesion of fly ash and its growth on the surface of the super heater, heat exchanger, and furnace walls, even when cocombusted with high-grade bituminous coal. In this study, six different fly ash samples collected from commercial pulverized coal combustion plants were investigated to find if the porosity and the liquid phase would have a significant impact on the tensile strength of the ash powder beds. Herein, we demonstrate that the use of alumina (Al2O3) nanoparticles as an additive is highly effective in preventing such troublesome events, which would be a great aid to facilitate stable and long-term operation of coal combustion plants. The function of Al2O3 nanoparticles is found to be 2-fold: retaining the porosity and perturbing the chemical composition of the ash samples. This is rationally supported by experimental and theoretical results. The key to our study is a split-type tensile strength tester that can directly measure the tensile strength of a powder bed being studied at various temperatures.