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.