CFD simulation of fine particle removal in flue gas condensing heat exchanger

Abstract Considering the obvious difference between dry and wet deposition, an original simplified model suitable for the particle removal process in the condensing heat exchanger was developed. With the help of user-defined functions, the proposed model was implemented into ANSYS FLUENT. The laboratory-scale experiments were performed to verify this simplified model. The numerical results were in good agreement with the experimental measurements, and the maximum error was within 8%. Using the CFD simulations, the effects of particle size and particle wettability on the removal of particles were analyzed. The results showed that the removal efficiency, growth rate of mean diameter and the proportion of grown particles increased with the decrease of contact angle. And they first decreased then increased with the increase of particle size. But the enhancement of removal efficiency was limited when the contact angle was small enough. The condensation growth transformed the particle system from monodisperse to polydisperse. The outlet particle size distribution could become bimodal distribution, which implied the potential for integrating acoustic agglomeration and condensing heat exchanger. However, the combined system should be well designed; otherwise, the bimodal distribution would degenerate.