Py-MS Study of Sulfur Behavior during Pyrolysis of High-sulfur Coals under Different Atmospheres

In this study sulfur pyrolysis behavior of two Chinese high sulfur coals and their treated coal samples was investigated by Py-MS at a heating rate of 5 °C/min from room temperature to 1025 °C under hydrogen, helium and 2% O 2–He. It is found that the internal and external hydrogen do not show hydrogenation ability at temperature below 400 °C, due to no H 2S formation at this temperature region for all the coal samples. At temperature higher than 400 °C, not only the indigenous hydrogen but also indigenous oxygen can react with sulfur-containing radicals to form H 2S or SO 2. The evolution of H 2S and SO 2 displays the same profiles in pyrolysis of ZY pyrite-free coal under He, further revealing that after the breakage of C–S bond in the organic sulfur structure in coal to form sulfur-containing radicals, which can equally react with indigenous hydrogen and oxygen. The similar tendency between evolution of CO 2 and SO 2 and the same ending temperature also shows that not only C–S but also C–C bond can be broken in pyrolysis of ZY coals under 2% O 2–He atmosphere. However, unlike SO 2 evolution, CO 2 emission increases in the temperature ranging from 500 °C to 800 °C in LZ raw and deashed coals, implying the breakage of C–C bond at high temperature, which might be related to their low coal rank and high pyrite content.