Multi-parameter framework for performance-based selection of Indian limestones in fluidized bed combustion systems

A multi-parameter framework for limestone sorbent selection in fluidized bed combustion (FBC) systems was developed through evaluation of eight Indian limestones (CaCO3: 70–95 wt%) from Western and Southern India. Characterization included chemical composition, mineralogy, mechanical strength, thermal behavior, attrition resistance, thermally induced fracturing (TIF), porosity evolution, sulfation efficiency, and fouling potential during co-firing. Post-calcination porosity (44–58%) and BET surface area (4.69–6.92 m2 g−1) correlated more strongly with sulfation efficiency than CaCO3 content. High-temperature microscopy revealed that TIF-generated hierarchical pore networks enhanced SO2 transport, enabling 30% coarser particle utilization. Sorbent D exhibited superior attrition resistance, retaining 9.6% coarse particles (>500 µm) post-calcination versus 1.4% for E2. Sulfation rankings varied with particle size (coarse: D > B > A > E > C; fine: C > D > E > B > A), demonstrating TIF’s dominance over chemical purity for coarse particles. Co-firing with lignite and petroleum coke produced anhydrite (30–50 wt%) and calcium silicates, indicating fouling risks. The framework enables 15–25% limestone reduction through: (1) chemical screening (CaCO3 >80 wt%, impurities <10–15 wt%), (2) physical characterization (BET >5.5 m2 g−1, TIF evaluation), and (3) performance validation. This approach supports sustainable SO2 emission control in coal-fired power generation, with applicability to India’s 210+ GW thermal power sector. A semi-empirical Sorbent Performance Index (SPI) is proposed, combining CaCO3 content, BET surface area, microstrength retention, TIF score, and impurity penalty, validated against measured limestone requirements addressing a sector facing heterogeneous limestone supply, high-sulfur coals, and tightening emission regulations.