This study reports solar-thermal pyrolysis of mallee wood powders driven by direct concentrated solar radiations at different temperatures (1540, 1740, and 1930 °C), heating rates (320, 800, and 3200 °C/min), and holding times (0 and 5 min). Under such severe pyrolysis conditions, solar-thermal pyrolysis of mallee wood produces predominantly volatiles (≥90 wt %), with very low char yields (≤10 wt %), as reported on a dry basis. Majorities of inherent alkali and alkaline earth metallic (AAEM) species are also released into the gaseous phase. The severe pyrolysis conditions also lead to the low reactivity of char products as a result of not only the char carbon structure becoming ordered and graphitized (as evidenced by the Raman data) but also significant losses of catalytic AAEM species in the char. For example, during the solar-thermal pyrolysis of mallee wood at 1930 °C, 800 °C min^–1, and 5 min holding time, the char yield is only ∼5 wt %, the retentions of Na and Mg are ∼1%, the retentions of K and Ca are only 13 and 35%, respectively, and the char is less reactive. Therefore, despite the low char yield, char conversion is still a critical consideration in the design and operations of solar-thermal reactors under these conditions because the char is very inert.

中文翻译：

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马利木在高温下的太阳热解

这项研究报告了在不同温度（1540、1740和1930°C），升温速率（320、800和3200°C / min）和保持时间（ 0和5分钟）。在如此严重的热解条件下，木炭的太阳热解产生的主要挥发物（≥90wt％），焦炭收率极低（≤10wt％），以干基计。大多数固有的碱金属和碱土金属（AAEM）物质也释放到气相中。严酷的热解条件还导致炭产物的反应性低，这不仅是由于炭的碳结构变得有序和石墨化（如拉曼数据所证明），而且炭中催化的AAEM物种的大量损失。例如，保持时间为^–1分钟和5分钟，炭的收率仅为〜5 wt％，Na和Mg的保留率分别为〜1％，K和Ca的保留率分别仅为13和35％，且炭含量较少反应性的。因此，尽管焦炭收率低，但是在这些条件下，焦炭转化仍然是太阳能热反应器设计和运行中的关键考虑因素，因为焦炭是非常惰性的。