Effect of Tire-Char Ash on the Extent of Synergy during CO₂Cogasification with Hydrochar from Potassium-Rich Coconut Fiber

The influence of inherent tire-char ash during cogasification with coconut hydrochar prepared at different intensities was investigated by thermogravimetric analysis to ascertain the extent to which synergistic interaction, reactivity, and activation energy reduction were altered. High-ash tire tread (TT) and low-ash sidewall (SW) both exhibited enhanced synergy, reactivity, and activation reduction upon cogasification with hydrochars; however, the extent of promotion was more pronounced in SW-hydrochar blends. This difference was caused by the inhibiting nature of TT inherent ash, particularly the role of Si-containing compounds. Inhibition in TT-hydrochar blends was mainly due to the promotion of alkaline and alkaline earth metal transformation into inactive silicates and, to a lesser extent, the mass transfer effect caused by accumulated ash, especially at conversions higher than 70%. The extent of enhancement correlated well with the concentration of available alkaline and alkaline earth metals. The findings may be useful in justifying the exclusion of high-ash tire char as gasification feedstock to mitigate ash-related problems.