The gasification of agro-industrial residues has been identified as a viable alternative for energy generation, acting simultaneously as a solution for the final disposal of these wastes. Knowing the kinetics of the gasification reaction is crucial to the comprehension of the mechanisms and the phenomena involved in the process, and the development and optimization of industrial gasifiers. Accordingly, this study aims to examine, based on four kinetic models, the CO₂ gasification behavior of three biomass chars prepared from apple pomace, spent coffee grounds and sawdust, and to associate the results with differences in the ash composition of the samples. The biochars were obtained from pyrolysis under N₂, in a fixed-bed tubular quartz reactor, with an average heating rate of 12 K min⁻¹ and a residence time of 60 min at the final temperature of 873 K. Biochars were isothermally gasified in a thermogravimetric analyzer with CO₂, at atmospheric pressure, at temperatures of 1033, 1083 and 1133 K, in the kinetically controlled regime. From the characterization of raw biomasses, it was found that the apple pomace had the highest amount of potassium, and its biochar was the most reactive. Also, it was observed an increase in the gasification rates in the higher conversion region for all biochars. Concerning these reactivity profiles, the inorganic components were more important to the gasification behavior than the biomass lignocellulosic matter. For all biochars, the semi-empirical modified random pore model (MRPM) was the best-fitted model, indicating its suitability to CO₂ gasification and confirming the catalytic influence of the inorganic matter in the studied samples. After demineralization, biomass chars presented higher values of activation energy and pre-exponential factor. According to the MRPM model, activation energy values within the range of 161.5–187.2 kJ mol⁻¹ and 232.1–240.2 kJ mol⁻¹, respectively, were obtained for the CO₂ gasification of regular biochars and demineralized biochars.

Graphical abstract

中文翻译：

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由巴西农业工业残留物制备的生物炭的 CO2 气化动力学模型：生物质本地矿物质含量的影响

农业工业残留物的气化已被确定为一种可行的能源生产替代方案，同时也是这些废物最终处置的解决方案。了解气化反应的动力学对于理解过程中涉及的机制和现象以及工业气化炉的开发和优化至关重要。因此，本研究旨在基于四个动力学模型检查由苹果渣、废咖啡渣和锯末制备的三种生物质炭的 CO ₂气化行为，并将结果与​​样品灰分组成的差异相关联。生物炭是在 N ₂下在固定床管式石英反应器中热解获得的，平均加热速率为 12 K min^-1和在 873 K 的最终温度下的停留时间为 60 分钟。生物炭在热重分析仪中与 CO ₂等温气化，在大气压下，在1033、1083和 1133 K 的温度下，在动力学控制状态下。从生物质的表征来看，苹果渣的钾含量最高，其生物炭的反应性最强。此外，还观察到所有生物炭在较高转化率区域的气化率增加。关于这些反应性曲线，无机组分对气化行为比生物质木质纤维素物质更重要。对于所有生物炭，半经验修正随机孔隙模型 (MRPM) 是最适合的模型，表明其适用于 CO₂气化并确认所研究样品中无机物的催化影响。脱矿后，生物质炭呈现更高的活化能和指数前因子值。根据MRPM模型，常规生物炭和脱矿生物炭的CO ₂气化分别获得了161.5-187.2 kJ mol ^-1和232.1-240.2 kJ mol ^-1范围内的活化能值。

图形概要