Formation mechanism of viscous ash layer covering heat exchange equipment in flue gas of coal-biomass co-firing power stations

Abstract Viscous ash layers and low-temperature corrosion pose major challenges to the high-efficiency operation of heat exchange equipment in the flue gas of coal-biomass co-firing power stations. The field experiments on low-temperature fouling layers were carried out in a 135 MW coal-fired power station and a 35 MW biomass-fired power station. The micro characteristics of ash samples were tested to explore the forming mechanisms of viscous ash layers. The results show that the reactions of ash particles and ammonium salt crystallization (NH 4 HSO 4 , (NH 4 ) 2 SO 4 , NH 4 Cl), acid condensation (H 2 SO 4 , HCl and HF), deliquescence of hygroscopic salts (CaCl 2 , MgCl 2 , NH 4 Cl, etc.), and water condensation determine the viscous ash layer formation covering heating surfaces in coal-biomass co-firing power stations.