An experimental study of fragmentation of coals during fast pyrolysis at high temperature and pressure

An experimental apparatus has been developed in order to perform tests of primary fragmentation of solid fuels under severe heating conditions (up to 2200 K and 12 bar). Particles are laid on the strip and pyrolyzed under inert conditions, fragments are recovered and analyzed by a laser granulometer to assess the fragmentation propensity of the fuel. Experiments have been carried out at temperatures between 1400 K and 1900 K, heating rate of 5000 K/s, pressure in the range 1-12 bar. Four different coals have been studied: Gracem, Venezuelan, Omsky, and Kleincopje, classified respectively as anthracite, high and medium volatile bituminous coals. Results show that primary fragmentation at high heating rate and high temperature may result in the formation of relatively coarse fragments and sometimes in a multitude of fines. The probability of fragmentation and the propensity to form coarse versus small fragments varies from coal to coal. For a given coal fragmentation increases monotonously with temperature, whereas the effect of pressure is nonmonotonous. The role of different chemico-physical properties of coals on the pattern and the extent of primary fragmentation is discussed, in particular volatile matter content, ash melting point, rigidity and porosity of the carbon structure and swelling index. (C) 2011 Elsevier Ltd. All rights reserved.