2-07　Investigation of Ash Particle Formation and Deposition Mechanisms on Heat Transfer Surfaces under High-Ratio Coal–Biomass Co-Firing

Abstract

Co-firing coal with biomass is a promising strategy for reducing CO₂ emissions in coal-fired power plants. In this study, three types of bituminous coals (CV, TOP, and TN) were blended with woody pellets (KP) and black pellets (BP1), and the resulting ash particle morphologies were systematically investigated. Ash particles were classified into two categories: an Aggregate type, formed by solid-phase bonding, and a Melting type, formed by partial melting and solidification. The results demonstrated that both the type of biomass and the blending ratio significantly influenced the relative proportion of these particle types. In particular, co-firing with BP1 increased the fraction of Melting type particles, and at higher blending ratios their proportion approached that of Aggregate type particles. These findings indicate that the combination of coal type, biomass type, and mixing ratio plays a critical role in determining ash deposition behavior, and under certain co-firing conditions may increase the risk of adherent ash deposition on heat transfer surfaces.