A novel CFD-DEM-DPM modelling of fluid-particles-fines reacting flows

Abstract

The complex fluid-particle-fine (FPf) reacting flows have been widely practised in many energy-intensive engineering processes, yet numerical methods capable of comprehensively describing the particle-scale thermochemical behaviours related to the FPf reacting flows were still lacking. In this work, a novel CFD-DEM-DPM model is developed, for the first time, to describe the fluid, particles and fines reacting flows and their interactions. Then, to demonstrate its effectiveness, it is employed to simulate the co-combustion of coke and pulverized coal in a dynamic raceway in ironmaking blast furnaces (BFs). After model validation, the complex in-furnace phenomena related to the co-combustion of coarse coke particles and fine coal particles are comprehensively captured. Particularly, instead of the pre-set raceway treatment in the previous raceway simulations, a dynamic raceway cavity is predicted explicitly driven by the fluid-particle-fine interactions and further, inside the dynamic raceway, the combustion of coal fines including moisture evaporation, devolatilization and char reactions are presented in detail. Subsequently, the impact of operations with and without coal injections are quantitatively compared, showing that both the reducing gas and reaction heat from the coal combustion contribute to an expansion of the raceway cavity. Further, the effects of pulverized coal rate on the in-furnace phenomena are studied. The present work represents a significant breakthrough in the explicit modelling of FPf reacting flows, and provides a cost-effective tool for understanding FPf-related processes and developing new technologies including carbon–neutral ironmaking technologies.