Optimization Study on Operating Parameters of Rotary Gas-Gas Heat Exchanger in Low- and Medium-Temperature Denitrification System for Cement Kiln Flue Gas

Rotary gas-gas heat exchangers (GGHs) are pivotal for waste heat recovery in low- and medium-temperature denitrification systems of cement kilns. This study examines the performance of GGHs within such systems by coupling computational fluid dynamics (CFD) with the response surface method (RSM), introducing overall system performance (OSP) as the principal optimization criterion. The investigation systematically elucidates the effects of treated flue gas inlet temperature, inlet velocity, and rotor speed on GGH efficiency. Findings reveal that OSP increases with rotor speed but reaches a plateau beyond 1 rpm; it decreases with higher inlet velocity and increases with higher inlet temperature. Response surface analysis identifies treated flue gas inlet temperature as the most influential parameter, highlighting a synergistic effect between rotor speed and inlet temperature, alongside an antagonistic interaction between inlet temperature and inlet velocity. To ensure safe system operation, engineering constraints were incorporated into the optimization framework using a Box-Behnken design. The optimal operational parameters were determined as a treated flue gas inlet temperature of 250°C, inlet velocity of 8 m/s, and rotor speed of 1 rpm, yielding a maximum OSP of 107.74. The integrated CFD-RSM methodology and constraint-aware optimization strategy presented in this study offer a practical reference for enhancing the operational efficiency of industrial waste heat recovery systems, particularly in cement kiln SCR applications.