In this study, experiments and analyses have been carried out to investigate the influences of denitrification and flue gas Waste Heat Recovery Systems (WHRS) on ash particles adhesion force. With use of a denitrification system, it is found that the ash particles adhesion force is strongly influenced by the mass ratio, R, of (NH4)HSO4 to ash. Three influencing zones are identified, i.e., little effect zone (R < 1: 150), intermediate effect zone (1: 150 < R < 1: 60), and huge effect zone (R > 1: 60). It is necessary to operate in the little effect zone in order to avoid ash deposition in the air preheater. With use of a WHRS, it is found that the ash adhesion force is strongly affected by the flue gas temperature in comparison with the Engineering Acid Dew Temperature (EADT). With decreasing temperature below the EADT, both the collected ash amount and ash adhesion force rise, and the detected particles size increases, indicating particle accumulation that improves ash collection efficiency. (C) 2017 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.