Evaluation of Wheat/Corn Stubble and Stalk Burning Characteristics Based on Ash Deposition Tendency and Kinetic Analysis

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The rhizosphere is the core area where soil-borne diseases occur, so removing stubble is one of the important measures to prevent soil-borne diseases. This study systematically evaluates the fuel potential and ash-related issues of wheat and corn residues (stubbles and stalks) through comprehensive physicochemical characterization, including proximate, elemental, biochemical analysis, FTIR, SEM, and XRF analysis. Thermogravimetric experiments at four heating rates, combined with Flynn-Wall-Ozawa (FWO) and Kissinger-Akahira-Sunose (KAS) kinetic models, were employed to elucidate combustion behavior and predict ash deposition trends based on sintering indicators. Results demonstrate that root stubbles exhibit superior comprehensive combustion indices and lower activation energies (wheat: 147.68–158.51 kJ/mol, corn: 176.65–181.01 kJ/mol) compared to stalks. Their ash primarily consists of refractory SiO₂ and Al₂O₃ components, minimizing slagging through mullite crystallization (Fu = 1.19–4.70). In contrast, stalk ashes exhibit a high alkali content, accelerating ash deposition (Fu = 19.43–52.40) and forming viscous low-melting-point agglomerates. Thermodynamic analysis reveals wheat stubbles have higher free Gibb’s energy (∆G) compared to corn counterparts, indicating enhanced bioenergy potential. The study provides an in-depth understanding of stubble combustion to mitigate soil-borne diseases and improve agricultural sustainability.