Cement Energy & Environment

45 Table 4 – CO 2 Capture Technologies Method Capture (%) Energy (GJ/t CO 2 ) Status Amine (CESAR1) 90 3.0 Commercial Calcium Loop 85 2.6 Pilot Oxyfuel 90 2.4 Pilot Membrane 70 1.8 Demo Electric Calciner + Biomass 80 2.1 Pilot India’s average TSR stands at 7–10% nationally, but top-performing plants exceed 60%. Proper drying, particle-size control, and blending are critical for flame stability. Global benchmarks show that with plasma-assisted ignition, hydrogen co-firing, and AI-controlled fuel mixing, TSR levels of 85–90% are achievable without compromising clinker quality. 6. CO 2 CAPTURE AND UTILIZATION Carbon capture and utilization (CCU) technologies are gaining traction in India. The aim is to capture CO 2 from kiln exhausts and reuse or store it. Figure 3 illustrates the general flow: exhaust gas passes through conditioning towers, absorbent columns, and regeneration units before being redirected for utilization. CO 2 Emisions Storage Storage Capture Cement Plant Products Clinker Quality index Thermal Substitution Rate (TSR) (%) CQI vs TSR Correlation 0 20 40 60 100 100 95 90 85 80 75 70 65 60 Figure 3 – CO 2 Capture and Utilization Pathway (Blue arrows = gas flow; red arrows = capture loop to storage or reuse.) Figure 4 – CQI vs TSR Correlation (Blue dots = data points; red line = trend line showing strength improvement.) Plant 7 in India successfully demonstrated cal- cium-looping capture with 85% efficiency. The captured CO 2 was reused for curing precast ele- ments, improving strength while permanently se- questering carbon. When integrated with WHR, the additional energy requirement for capture can be partly offset. Combining AF with CCU can reduce net CO 2 by 15–20%. 7. CLINKER QUALITY INDEX AND PROCESS CORRELATION Clinker Quality Index (CQI) provides a scientific link between process efficiency and cement quality. Defined as: CQI = (28-day Strength × C 3 S%) / (Free Lime × Specific Heat) × 10³ Higher CQI indicates more reactive clinker and optimized fuel usage. In AI-controlled kilns, CQI values improved by 15–25% compared to manual operations. As shown in Figure 4, CQI rises with TSR up to about 85%, after which excessive AF usage can reduce flame temperature and affect alite formation. Maintaining C 3 S between 65–67%, controlling cooling rate (50–60°C/min), and adjusting the raw mix (Lime Saturation Factor ≈ 97–99) are essential to preserve clinker strength. These measures create a direct link between thermal performance and material properties.