Temperature–blending ratio effects on ash resistivity during corn stover/lignite co-firing for bioenergy applications

Abstract

Corn stover co-firing provides a practical route for integrating agricultural residues into existing coal-fired power systems, but biomass-induced changes in ash behavior may affect particulate control and the operational reliability of bioenergy utilization. In this study, the room-temperature resistivity of lignite/corn stover co-firing ashes prepared at different temperatures and biomass blending ratios was investigated using resistivity measurements, quadratic response surface modeling, Sobol global sensitivity analysis, thermodynamic equilibrium calculations, and physicochemical characterization. The measured ash resistivity ranged from 1.47 × 10 6 to 1.06 × 10 8 Ω cm and decreased with increasing biomass blending ratio at each of the five combustion temperatures. A region-dependent response was observed, with generally smaller relative blending effects at higher combustion temperatures. The quadratic response surface model was statistically significant but exhibited significant lack of fit, limiting its use to the interpretation of broad response trends. Within this fitted model and the specified input domain, combustion temperature accounted for 91.14% of the variance in logarithmic resistivity through its first-order effect. Physicochemical characterization and equilibrium calculations linked corn stover addition to K enrichment and changes in mineral assemblage, ash fusion behavior, and particle structure. Particle coarsening and more evident bridge-like structures and sintering necks accompanied the measured resistivity reduction, supporting an interpretation involving changes in interparticle contacts. Overall, this study clarifies how agricultural-residue blending affects the composition, structure, and electrical response of co-firing ash, providing experimental evidence on ash properties relevant to electrostatic precipitation during biomass co-firing for cleaner bioenergy utilization.