Study on Thermal Characteristics and Ash Deposition of a Novel Dual-Flue Gas Rotary Air Preheater

Abstract The dual-flue gas rotary air preheater demonstrates significantly better heat transfer performance and operational efficiency than the conventional three-compartment rotary air preheater. This study conducts numerical simulations of both configurations under various operating conditions to compare their thermal behavior and ash deposition. Results show that the flue gas outlet temperature of the dual-flue gas preheater is 1.98% lower than that of the three-compartment configuration, with the most notable 7.33 °C reduction under 50% turbine heat acceptance (THA) conditions. Meanwhile, the secondary air outlet temperature increases by 2.13%, and overall heat recovery efficiency improves by approximately 2%. Temperature distribution analysis reveals that the average rotor temperature of the dual-flue gas preheater is about 20 °C higher, indicating more uniform heat transfer and mitigation of cold-end overcooling. Furthermore, the high ammonium bisulfate (ABS) deposition zone reduces from about 1100 mm to 800 mm in height, and the ash deposition area decreases by roughly 20%, significantly lowering fouling risk. By maintaining cold-end metal temperature above the acid dew point, the dual-flue gas preheater effectively alleviates low-temperature corrosion. In summary, it offers a more efficient and reliable solution for industrial applications by enhancing heat transfer, optimizing temperature distribution, and reducing ABS deposition and corrosion risks.