Product distribution and sulfur behavior in coal pyrolysis

Pyrolysis experiments of six differently ranked Chinese coals and one German coal were carried out systematically at ambient pressure. The effect of different pyrolysis conditions, including coal properties, temperature, drying of coal, on the product distribution and the behavior of sulfur in coal were investigated. The results indicated that, besides coal properties, temperature is the most important factor which affect the product distribution of pyrolysis. CO and CO2yields in gas product are related to the oxygen content in the coal sample. Except for the sample of Datong (DT) coal, the CO and CO2yield increases linearly with the increase in O/C atomic ratio of coal; sulfur-containing gas (H2S and COS) yield depends directly on sulfur content in the coal. With the increase in total sulfur content, pyrite sulfur content or organic sulfur content of coal, the sulfur containing gas increases substantially. Sulfur removal during coal pyrolysis at different conditions varies from 15% to 40% depending on coal sample, pyrolysis temperature and time. For most coal samples, the sulfur content in char is less than that in its original sample, but some exception was also found. X-ray photoelectron spectroscopy (XPS) analyses suggest that difference in sulfur removal may be partly attributed to the difference in sulfur contents in the bulk and on the surface for different coals.