Relation Between Coal Pyrolysis and Corresponding Coal Char Gasification in CO₂

Six kinds of coals, from lower to higher rank, were investigated to do the experiments of the pyrolysis and gasification in the CDS2000 pyroprobe reactor. The reactor has the features of flash heating rate and short quench time, which can minimize the secondary reaction between released products and nascent coal char during pyrolysis. An inline detector FTIR combined with pyroprobe reactor was employed to detect the products released during the pyrolysis and gasification process. Two kinds of heating rate, 20°C/min and 1200°C/min, were adopted in pyrolysis to compare the different property of coal char formed in subsequent gasification. After switching ultra-high-purity N₂ gas to CO₂₂ atmosphere, char samples prepared in situ were kept inside the reactor without any delay and were gasified at the heating rate of 1200°C/min up to the set temperature around CO₂ atmosphere. Three gasified temperatures, 450°C, 750°C and 1100°C, were analyzed. Results show that when char preparation temperatures were above the range of 810-850°C, the gasification reactivity of char prepared at slow heating rate is higher than that prepared at fast heating rate; when the temperature was below this temperature range, it showed the reverse trend. Char gasification reactivity is directly proportional to the amount of the precursors of tar remaining on the surface of nascent char.