Numerical Investigation of Suspension Heating for Solid Particles

Abstract

With the global energy transition and large-scale renewable integration, thermal power units are shifting from base-load to peak-shaving roles, but deep peak shaving may cause combustion instability and increased emissions. High-temperature solid-particle thermal storage offers a low-cost and wide-temperature-range solution for enhancing unit flexibility. This study proposes a flue-gas-driven solid-particle thermal storage system in which high-temperature flue gas extracted from the furnace directly heats solid particles through a multi-stage suspension preheating process. An industrial-scale suspension preheater was modeled using the Computational Particle Fluid Dynamics (CPFD) method to investigate gas–solid flow and heat transfer for quartz sand with different particle sizes and cement raw meal. The effects of particle size and thermophysical properties on particle motion, temperature evolution, gas–solid heat transfer coefficient, and flow-field characteristics were systematically analyzed. The results show that the outlet flue-gas temperature was approximately 705–725 K under the investigated conditions. For quartz sand, the particle outlet temperature decreased from approximately 715 K to 660 K as the particle size increased from 0.45–0.55 mm to 1.45–1.55 mm. The gas–solid heat transfer coefficient of quartz sand remained relatively stable, mainly ranging from approximately 450 to 900 W/(m2·K), whereas that of fine raw meal was approximately 1750–2600 W/(m2·K). Larger quartz sand particles also exhibited more pronounced wall attachment because of their higher inertia. These results demonstrate the potential applicability of suspension-preheater-based direct flue-gas heating for high-temperature solid-particle thermal energy storage and provide quantitative information for the design and operation of such systems.