A numerical simulation study of ash deposition in a circulating fluidized bed during Zhundong lignite combustion

•Ash deposition during ZD CFB combustion simulated by a novel critical viscosity model.•Simulation result with a deposit thickness of 3.4 mm agreed well with experimentation.•Synergic effect of particle impaction and particle sticking systematically analysed.•The effect of flue gas temperature overweighs that of particle or probe temperature.•The role of Na in initiating deposition confirmed by considering particle chemistry.