Influence of added calcium compounds on swelling, plastic, and pyrolysis behaviour of coal devolatilized at elevated pressures

Abstract

The swelling and plastic properties of a low volatile bituminous coal pyrolysed in the presence of added Ca compounds have been investigated. The results suggest that the addition of CaO significantly reduced the swelling and plastic behaviour of coal at low pressures (< 0.1 MPa) of H 2 or He. However, at elevated pressures (≈ 2.9 MPa) of H 2 and He, the maximum swelling parameter, V s , was restored to varying degrees depending on the heating rate and the concentration of CaO utilized. The effectiveness of the Ca additives as decaking agent decreases in the order: Ca( Ac) 2 > CaO > CaCO 3. The presence of CaO resulted in increased solid yield. It is suggested that crosslinking reactions catalysed by Ca facilitate increased thermosetting char yield. At elevated pressures of H 2, it was noted that the swelling parameter increased. This is explained by suggesting that the effect of H 2 is to reduce the extent of char-forming reactions during pyrolysis by ‘capping’ some of the free radicals and thus increasing the fluid behaviour of coal.