Mechanistic Determination of the Role of Aluminum in Particle Adhesiveness at High Temperatures Induced by Sodium and Potassium Using a Synthetic Ash Strategy
Genki Horiguchi, Yuta Beppu, Kentaro Yoshinaga, Hidehiro Kamiya, Yohei Okada
Abstract
Energy recovery from various fuels with high efficiency is an important objective to realize sustainable energy conversion systems. During the combustion process, ash particles are produced that can form aggregates inside of combustion plants, which inhibit stable and effective plant operation. This is a serious problem for plant operation, and the control of ash particle aggregation under high-temperature conditions is an important objective. In this research, a method to effectively suppress the adhesiveness of particles at high temperatures is proposed based on a synthetic ash strategy. Synthetic ashes were prepared from a base material with sodium (Na) or potassium (K) as target elements to induce adhesiveness. The base material included both silicon (Si) and aluminum (Al). The tensile strengths of powder beds of the prepared synthetic ash with various alkali concentrations were measured at high temperatures, by which it was confirmed that Na could induce higher adhesiveness than K at low alkali concentrations. This difference was ascribed to the presence of Al. The role of Al in particle adhesiveness was clarified by control of the Al concentration through the addition of aluminum oxide (Al2O3) nanoparticles, and the ratio of alkali to Al (Na/Al or K/Al) had an effect on particle adhesiveness at high temperatures, that is, the particle adhesiveness could be suppressed by a decrease of these ratios.