Investigation into microscopic characteristics of bituminous surface under different fast pyrolysis conditions

In a drop tube furnace with the combustion conditions similar to those of actual pulverized coal furnace,ShenMu bituminous coal char of fast pyrolysis conditions are prepared under different reaction atmospheres of N2,φ(N2)=83.4%∶φ(CO2)=16.6%,φ(N2)=81.6%∶φ(CO2)=16.6%∶φ(O2)=1.8%.By means of scanning electron microscopy and flue gas analyzer,the achieved experimental results are quite different from slow pyrolysis of packing pulverized coal.Under fast pyrolysis conditions,more small particles of coal crushing are found.With increasing residence time,the small holes on the surface of char gradually increase.Compared with N2 atmosphere,the surface of the char under φ(N2)=83.4%∶φ(CO2)=16.6% atmosphere becomes more densely.Finally,with increasing residence time,under φ(N2)=81.6%∶φ(CO2)=16.6%∶φ(O2)=1.8% atmosphere,some weak fire is found on the surface of the coal char.