Numerical simulation of ash deposition on the surface of tubes bundle

Abstract

Ash deposition is one of the significant challenges for coal-fired boilers. It is a serious problem that causes fouling and slagging on the tube bundle that Poses some potential safety and hazard problems for utility boilers. There. Therefore, the paper presented a numerical study using ANSYS FLUENT. A discrete phase model (DPM) is used to simulate ash particles for unsteady flow. The influence factors important to heat transfer performance and ash deposition are studied, consisting of the changes of the inlet velocity of flue gas, and the temperature differences between the flue gas and the surface of ash deposit. A thermophoresis deposition mechanism (fine particles< 1µm) is a playing impact in an important role in this study. The proposed method is an effective instrument for forecasting the ash deposition formation and growth. The result indicates thermophoresis causes more ash to be deposited than without thermophoresis. Also, they notice the effects of temperature gradient on the deposition height at constant inlet velocity. The deposition height is decreased when the temperature differences increase as a ratio of 0.125%. through 30 min. While the effects change inlet flue gas velocity on the deposition height. The deposition height is decreased when the increased velocity at constant temperature differences about 0.75%.