A new enabling multiscale model for low-carbon cement pre-calciners fueled by biomass

Although large biomass fuels offer significant potential for deep decarbonization, their use in cement pre-calciners often results in incomplete burnout. Raw meal agglomeration adds further complexity, and together these effects cause reactor instability and inefficiency, as well as downstream operational issues. For the first time, this paper presents an enabling numerical model to address these challenges. For this purpose, a Multi-Fluid Model (MFM) is initially developed to effectively capture the multiphase reactive flows and agglomeration effects in industrial pre-calciners. The model integrates a particle-scale agglomeration mechanism and incorporates the agglomerate sizes into constitutive relations—including granular energy, solid viscosity, drag force, heat and mass transfer, and reactive surface area. Validation against industrial data confirms the model's markedly improved predictive accuracy compared with previous models, and its applicability is further examined under different tertiary air conditions. Based on this, a Sub-Particle-Scale (SPS) model is incorporated to account for intraparticle temperature gradient effects within large biomass particles in industrial systems. After validation using industrial measurements, the integrated model is applied to reveal biomass size effects on incomplete burnout and pre-calciner performance. These new efforts account for fine particle agglomeration and intraparticle temperature gradients in large particles while maintaining suitable computational efficiency, thereby enabling effective industrial-scale simulations. It provides a tool for guiding the operation of biomass-fueled pre-calciners under various conditions, supporting the advancement of low-carbon cement production.