Entrained flow gasification of sewage sludge digestate: Experimental and simulation study

This work explores the entrained flow gasification of sewage sludge digestate (SSD) and its mixtures with wood powder (WP) through experimental and modeling approaches. Key parameters including reactor temperature, pressure, steam-to-biomass ratio (S/B), and air excess ratio (λ) were investigated to assess their impact on gasification performance. Results showed that blending SSD with WP significantly improved gasification efficiency, leading to higher hydrogen (H₂) and carbon monoxide (CO) yields. Complete carbon conversion was achieved at temperatures above 1100 °C with a 50/50 SSD/WP mixture, highlighting the effectiveness of WP addition. Cold gas efficiency (CGE) exceeded 100 % for mixed feedstocks at optimal conditions, demonstrating improved syngas quality. SEM-EDS analysis indicated better properties and nutrient retention potential of residues derived from gasification of blended feedstocks. Computational Particle Fluid Dynamics (CPFD) simulations, validated against experimental data, provided deeper insights into gasification, confirming enhanced syngas production and reactor performance with SSD/WP mixtures. These findings underline the potential of SSD and WP co-gasification for sustainable waste management and energy recovery.