CaS-CaSO4是否共熔的DTA和TG实验研究

CaS和CaSO₄熔点均在1400℃以上,研究发现CaS和CaSO₄混合物在827℃可能存在熔融现象。CaS与CaSO₄是否存在共熔对以CaSO₄为载氧体的反应器的操作条件优化具有重要影响。从物理化学变化及其热效应角度,利用综合热分析仪对氮气气氛下不同摩尔比例均匀混合的CaS、CaSO₄样品进行差热分析(DTA)和热重分析(TG)研究,并对实验残留物进行SEM分析。结果表明,在700~1300℃的常压惰性气氛条件下,没有发现CaS和CaSO₄组成的任意二元混合物存在共熔现象。对由不同比例组成的CaO、CaS、CaSO₄三元混合物进行类似的实验,结果表明,在700~1500℃的常压惰性气氛下,没有明显的证据证明存在三相共熔现象。

DTA & TG measurement and analysis of CaS-CaSO4 system

In the process of direct hydrogen production from coal with CaSO₄ as oxygen carrier,CaS and CaSO₄ are used together at a high temperature.There is a dispute in literature whether an eutectic phenomenon occurs between them,although the melting points of them are above 1400℃.TG and DTA measurements of CaS,CaSO₄ mixtures with different molar ratios were performed using a atmospheric thermal analyzer under nitrogen atmosphere.The results showed that within 700℃ to 1300℃,the DTA curves of endothermic peaks within 850-1100℃ were due to the endothermic solid-solid reaction between CaS and CaSO₄.The temperatures when the first endothermic peak appeared and the temperatures when the fastest change of DTG curves happened were compared between different samples.No eutectic point was found,which meant eutectic phenomenon did not exist within 700-1300℃.Similar analyses were performed on CaO,CaS and CaSO₄ mixture samples,and no eutectic evidence was found within 700-1500℃.The conclusions above were also confirmed by the SEM analyses performed on the residue samples.