Co-gasification of Jordanian olive mill solid waste and RTC coal for thermochemical treatment: characterization and equilibrium modelling

Olive mill solid waste (OMSW) is a significant agricultural byproduct from olive cultivation and related productions. Recognized as a valuable energy resource in countries such as Jordan, Syria, and Tunisia, this study focuses on the comprehensive characterization of Jordanian OMSW (J-OMSW) and RTC coal. Utilizing analytical tools such as thermogravimetric analysis (TGA), bomb calorimetry, FLASH organic elemental analyzer, x-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM), the research also includes a comparative analysis with river trading company (RTC) coal to assess the co-gasification feasibility of the two feedstocks. Equilibrium-based analysis explores optimal co-gasification conditions for RTC coal and J-OMSW, assessing reaction, energy, and elemental balances. J-OMSW is characterized by higher volatiles (73.26%) and lower fixed carbon (20.59%) than RTC coal, which has 39.09% volatiles and 54.31% fixed carbon, enhancing co-gasification compatibility. Ultimate analysis indicates J-OMSW has significant carbon (47.53%) and oxygen (40.14%), contrasting with RTC coal’s higher carbon (76.39%) and lower oxygen (8.15%), supporting synergistic co-gasification processes. RTC coal’s higher heating value (HHV) at 30.44 ± 0.2 MJ/kg complements J-OMSW’s HHV (23.75 ± 0.2 MJ/kg), enhancing the blend’s energy potential. Both materials share similar functional groups of C-H, C = O, C-O-C, and C-OH, minimal mineral matter, and predominantly amorphous structures, underscoring their co-gasification suitability. J-OMSW displays a more porous microstructure compared to RTC coal, further enhancing gasification potential. The equilibrium model identifies optimal gasifier temperatures of 1,150 °C, 1,200 °C, 1,200 °C, 1,200 °C, and 1,250 °C for 100%, 90%, 75%, 50%, and 25% RTC coal blends, respectively, achieving peak CGEs ranging from 66.90 to 82.83%. Higher pressures (above 30 bars) and temperatures negatively affect CGE, particularly in blends. The model favors a 50% blend for its efficiency and environmental benefits, demonstrating technical viability. The lowest actual oxidizer moles result in CGE deviations between 0.01% and 1.27%, suggesting an optimal equivalence ratio (ER) of 0.5–0.65. Comprehensive characterization of J-OMSW and RTC coal, alongside equilibrium analysis, confirms the feasibility of co-gasification, providing insights into efficient energy recovery from J-OMSW.