Effect of some natural minerals on transformation behavior of sulfur during pyrolysis of coal and biomass

Highlight•Adding tourmalines, Na-bentonite and medical stone can make the total sulfur retention increase during coal pyrolysis.•Adding tourmalines, Na-bentonite and medical stone also can make organic sulfur retention higher.•These natural minerals are beneficial for sulfate sulfur to remove during coal pyrolysis.•Na-bentonite, tourmaline 2 and medical stone are all good for pyritic sulfur to decompose and remove.•Tourmaline 2 and medical stone are beneficial for sulfur to convert into H2S and then escape, and medical stone is also good for sulfur to turn into COS during coal pyrolysis.

The effect of tourmalines, Na-bentonite and medical stone on the retention of total sulfur, pyritic sulfur, sulfate sulfur and organic sulfur were investigated in a fixed bed reactor. The result shows that during Longma coal pyrolysis, adding tourmalines, Na-bentonite and medical stone all make the total sulfur retention and organic sulfur retention increase obviously. Interestingly, the results also indicate that adding tourmaline 1 (T1), tourmaline 2 (T2), Na-bentonite and medical stone all could make sulfate sulfur retention decrease obviously. Furthermore, when temperature is below 650 °C during coal pyrolysis, adding tourmaline1 (T1) makes pyritic sulfur retention higher; while adding Na-bentonite, tourmaline 2 (T2) or medical stone makes pyritic sulfur retention lower. Besides that, the results also show that adding tourmaline 2 (T2) is beneficial for sulfur to convert into H2S and then escape, while adding medical stone is not only good for sulfur to turn into H2S, but also is good to turn into COS during LM coal pyrolysis. For co-pyrolysis of LM coal and biomass, the results show that during co-pyrolysis of LM coal and wheat straw or sawdust, adding tourmaline 1 (T1) influences the total sulfur retention differently with temperature increases. Furthermore, adding tourmaline 1 (T1) also could influence the emission of H2S and COS to a certain degree during co-pyrolysis of coal and biomass.