EXPERIMENTAL AND NUMERICAL EVALUATION OF A DIRECT SOLAR DRYER FOR LEATHER TANNERY SLUDGE

This study evaluates the performance of a direct solar dryer for treating hazardous leather tannery sludge using an integrated experimental and numerical approach. Laboratory experiments analyzed convective drying at 50°C, 60°C, and 70°C, achieving a moisture content of 0.20 kg water/kg dry matter within 7 h at 70°C, although the method was energy-intense and costly, requiring stringent safety measures. In contrast, numerical simulations of solar drying reduced sludge moisture from 80% to 20% within 6-8 h in summer and 10-12 h in winter, achieving 85% efficiency during peak solar radiation. Solar drying utilized 100% renewable energy, cut greenhouse gas emissions by 60%, decreased landfill dependency by 70%, and significantly reduced environmsental pollution. Economic analysis revealed 40% energy cost savings, 50% operational cost reductions, and potential revenue from sludge valorization. The numerical model is closely aligned with experimental results, confirming its accuracy. These findings highlight solar drying as a sustainable, cost-effective solution for sludge management in sun-rich regions like Tunisia, supporting cleaner production, circular economy initiatives, and global goals to reduce energy consumption and greenhouse gas emissions.