Study on Multi-Product System of Supercritical Water Gasification of Paper Mill Black Liquor

Abstract

To address the issues of high pollution and low resource utilization efficiency in papermaking black liquor treatment, this study developed a novel polygeneration system based on Aspen Plus software. The system achieves coordinated production of hydrogen, thermal energy, and electricity at a treatment capacity of 1 ton/hour through supercritical water gasification (SCWG), Allam cycle, combustion furnace, and cold energy utilization. Gasification characteristics and product composition were evaluated, with simulation models validated against published experimental data. Key operational parameters including SCWG temperature, pressure, and black liquor concentration were systematically investigated for their impacts on gas generation properties and system performance. Results demonstrate that increasing SCWG temperature significantly enhances hydrogen yield and molar fraction but markedly reduces methane production. SCWG pressure within the 23-28 MPa range shows negligible effect on gas product distribution. Elevated black liquor concentration suppresses hydrogen generation while promoting methane and carbon monoxide production. The proposed SCWG-Allam cycle coupling system efficiently converts papermaking black liquor into clean energy with high efficiency and near-zero carbon emissions. This study provides feasible technical solutions and theoretical foundations for black liquor resource utilization and optimized design of low-carbon polygeneration systems.