EFFECT OF CO2 ON COAL PYROLYSIS AT HIGH AND LOW HEATING RATES ON CHAR REACTIVITY

In oxy-fuel combustion, coal particles undergo pyrolysis in CO2 rich atmospheres. The composition of the gaseous atmosphere under which pyrolysis takes place may have important effects also on the formation of pyrolysis products. In the present work, pyrolysis experiments have been carried out with a medium rank high volatile bituminous coal substituting N2 with CO2. Experiments have been carried out in a laminar drop tube reactor as well as in a fixed bed reactor. CO2 chars prepared in the drop tube reactor turned out to be less reactive towards combustion than the corresponding N2 chars. Differently chars prepared at low heating rates and temperature have similar combustion reactivity regardless of the N2 vs CO2 pyrolysis atmosphere.