Abstract The thermal decomposition of pyrite is considered to be a crucial process in coal pyrolysis and the pretreatment of gold-bearing sulfide concentrates. This study focuses on the different effects of conventional and microwave heating under nitrogen on the decomposition of pyrite in terms of sulfur transformation, phase transformation, and microscopic morphology. The results show that microwave energy can be applied to the thermal breakdown of pyrite with a decreased heat-up time. The higher sulfur conversion rate and lower S/Fe molar ratio indicates that microwave-assisted pyrolysis promotes the sulfur transformation process during the thermal breakdown of pyrite. The phase transition temperature range is 600–700 °C by conventional heating, whereas it decreases by approximately 100 °C under microwave heating conditions. This means that microwave heating reduces the temperature required for thermal pyrite decomposition. Moreover, kinetic analysis showed that the activation energy for the breakdown of pyrite under microwave conditions is 172.62 kJ mol−1, which is slightly lower than that for conventional heating (199.76 kJ mol−1). It is revealed that the different effects of conventional and microwave heating on the thermal decomposition of pyrite are due to different heat-transfer processes. Although the grain surface morphologies and microstructures of pyrite following treatment at 700 °C are loose and porous regardless of which heating system is adopted, microwave heating results in the generation of more pore structures at lower temperatures and shorter heating times than those required for conventional decomposition.

中文翻译：

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不同加热温度下黄铁矿热分解微波与常规加热方法的比较

摘要 黄铁矿的热分解被认为是煤热解和含金硫化物精矿预处理的关键过程。本研究侧重于常规和微波加热在氮气下对黄铁矿分解的硫转化、相变和微观形貌的不同影响。结果表明，微波能可用于黄铁矿的热分解，同时缩短加热时间。较高的硫转化率和较低的 S/Fe 摩尔比表明微波辅助热解促进了黄铁矿热分解过程中的硫转化过程。常规加热的相变温度范围为 600–700 °C，而在微波加热条件下，相变温度降低约 100 °C。这意味着微波加热降低了热黄铁矿分解所需的温度。此外，动力学分析表明，微波条件下黄铁矿分解的活化能为172.62 kJ mol-1，略低于常规加热（199.76 kJ mol-1）。结果表明，常规加热和微波加热对黄铁矿热分解的不同影响是由于不同的传热过程。尽管无论采用哪种加热系统，在 700 °C 处理后黄铁矿的晶粒表面形貌和微观结构都是疏松多孔的，但微波加热导致在较低温度下产生更多的孔隙结构和比常规分解所需的加热时间更短.