Establishment and validation of tar fouling mechanism in wood pellet boiler using kinetic models

Tar is formed and fouled in the combustion chamber of the wood pellet boiler. Because of the low thermal conductivity of fouled tar, the total heat transfer rates between the combustion gas and heating fluid decreases, leading to additional heating cost for cleaning the boiler to maintain its performance. In this study, the amount of tar fouled on the heating surface was predicted by the phenomena and mechanism of formation and fouling, and the kinetic model was validated with the experimental data. The Computational Fluid Dynamics (CFD) simulation of the thermal behavior of combustion gas in the combustion chamber of the wood pellet boiler was performed. In the experiment, most of the tar fouled on the opposite surface of the burner inlet side, and fouling rates (kg/m2) increased linearly with the passage of time. The measured values were in good agreement with the calculated data. The results could be useful for further study on tar reduction and removal techniques and increasing the thermal efficiency of the wood pellet boiler.