The Xiaolongtan coal with different blend ratios (ash/coal) of ash was pyrolyzed in a fixed bed reactor to study sulfur transformation during the pyrolysis of the mixture of coal and coal ash. The addition of coal ash inhibited H2S evolution at low temperatures, and this was because H2S was captured by Fe2O3 of the coal ash. However, the coal ash promoted H2S evolution at high temperatures, which should be due to the reaction 4H(2) + CaSO4 -> CaO + 3H(2)O + H2S. More COS was evolved with the addition of coal ash at 700800 degrees C, and the possible reason was that COS could be produced through the reactions 4CO + CaSO4 -> CaO + 3CO(2) + COS and 2C + CaSO4 -> CaO + CO2 + COS. The addition of coal ash reduced tar sulfur. The effects of the conditions (temperature of ash preparation and atmosphere) on the sulfur containing gas were also discussed. The evolution of H2S and COS were less affected by the ash prepared under 1000 degrees C than that under 800 degrees C and 900 degrees C. The possible reason was that the reactions among the volatile matters and coal ash were unfavorable due to the sintering of the ash under 1000 degrees C. The effect of coal ash on H2S and COS under simulated pyrolyzed gas atmosphere was similar to that under N-2 atmosphere, but higher H2S and COS yields were obtained under simulated pyrolyzed gas atmosphere. (C) 2016 Elsevier Ltd. All rights reserved.