This study proposed the use of the kinetic triplet analysis and thermodynamic parameter determination to investigate the hydrothermal carbonization (HTC) of cocoa shell (CS) for energy production. The variations in the Eα were determined by model-free isoconversional methods, the A values were determined using the ASTM E698-18 kinetics approach, and for f(α), the master plot methods were used. A progressive variation of Eα values was found, revealing competitive or consecutive reactions during HTC process, as well as multiphasic biomass conversion. From the master plot method, the experimental curve of CS does not perfectly match a single theoretical curve, indicating different reaction mechanisms during the HTC process. However, over the entire conversion range, the n-order reaction model (n = 1.25) adequately describes the experimental behavior (R² > 0.995). Furthermore, this value of n = 1.25 may imply a relatively low collision probability and can be related to the high extractives and lignin content in CS. Furthermore, for specific values of α, the difference between Eα and ΔH was lower than 3.98 kJ/mol indicating the facility to convert CS to hydrochar. In addition, the ΔS values showed that the process reaches thermodynamic stability during the conversion of CS. Finally, hydrochar characterization showed an energy densification of 40.30% in the case of hydrochar produced at 250 °C, thus demonstrating the feasibility of using this type of biomass for energy purposes.

Graphical abstract

中文翻译：

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可可壳的水热碳化：水炭表征、动力学三元组和过程的热力学方面

本研究提出使用动力学三重态分析和热力学参数测定来研究可可壳 (CS) 的水热碳化 (HTC) 用于能源生产。Eα的变化通过无模型等转化方法确定，A值使用 ASTM E698-18 动力学方法确定，对于f ( α )，使用主图方法。Eα的渐进变化发现值，揭示了 HTC 过程中的竞争或连续反应，以及多相生物质转化。从主图方法来看，CS 的实验曲线与单一的理论曲线并不完全匹配，表明 HTC 过程中的反应机制不同。然而，在整个转化范围内，n级反应模型 ( n  = 1.25) 充分描述了实验行为 ( R ²  > 0.995)。此外，n  = 1.25 的值可能意味着碰撞概率相对较低，并且可能与 CS 中的高提取物和木质素含量有关。此外，对于 α 的特定值，Eα和Δ之间的差异H低于 3.98 kJ/mol，表明有将 CS 转化为水炭的设施。此外，ΔS值表明该过程在CS转化过程中达到了热力学稳定性。最后，水炭表征表明，在 250 °C 下生产的水炭的能量密度为 40.30%，从而证明了将此类生物质用于能源目的的可行性。

图形概要