Coal Switching-Induced Boiler Overheating Prevention through Integrated CFD Fireball Analysis and Coal Velocity Balancing

Abstract

Coal switching to 100% Low-Rank Coal (LRC) in pulverized coal-fired power plants often induces combustion instability and increases the risk of localized superheater overheating due to uneven coal–air distribution. Differences in coal pipe velocities can lead to fireball displacement and non-uniform heat release inside the furnace. This study proposes an integrated preventive approach combining Computational Fluid Dynamics (CFD)-based fireball analysis and Coal Velocity Balancing (CVB) to improve combustion stability and mitigate overheating during full LRC operation. A full-scale case study was conducted at a 300 MW Rembang CFPP operating full-load LRC firing. CFD simulations were initially performed to identify fireball displacement and temperature non-uniformity. Based on the simulation results, mechanical orifice adjustments were applied to pulverizers A, B, and D to restore coal velocity uniformity across burner pipes. The combined numerical and field measurement results show a significant reduction in coal flow maldistribution, improved flame symmetry, and lower as well as more uniform outlet flue gas temperatures. These improvements indicate reduced thermal stress on critical boiler components, particularly the superheater. In addition, a slight reduction in coal consumption was achieved without compromising boiler load, indicating improved combustion efficiency. This study confirms that the integration of CFD-based fireball diagnostics and on-site coal velocity balancing provides a practical and cost-effective preventive strategy for mitigating boiler overheating during coal switching to low-rank fuel.