CHANGES IN THE PHYSICAL PROPERTIES OF ANTHRACITES UPON HEAT TREATMENT

Special Research Report SR-40 Heat treatment of three different Pennsylvania anthracites have been carried out in an inert atmosphere at temperatures up to 1000°C. The effects of such treatment on the volatile matter release, and selected physical properties of the anthracites (surface area, helium an.cl mercury densities, and crystallite heights) were investigated. For the two anthracites of lower volatile matter content, it has been found that the weight of volatile matter release was less at 900°C. than at 800°C. This is taken to indicate that hydrogen is released as methane at lower temperatures and as hydrogen at higher temperatures. Both the macro- and micro- pore areas decreased sharply on heat treatment; as indicated by the decrease in surface areas measured by the adsorption of nitrogen and carbon dioxide. Both the helium and mercury densities increase on heat treatment, again suggesting closure of pores. Crystallite heights go through a minimum with increasing heat treatment temperatures.