This paper analyzes fast coal pyrolysis technologies from a chemical reaction engineering point of view. It shows that the volatiles generated from coal transport in a direction against that of the heat transfer

and that the principle behind the fast coal pyrolysis technologies

i.e. reducing pyrolysis time by increasing the heating source temperature

may not reduce the reactions of volatiles as expected. Rather it promotes the reactions of volatiles leading to a low tar yield and formation of coke fines. Compared with the reduction in reaction time of volatiles the reduction in pyrolysis temperature is more important for reducing the volatiles' reaction (cracking)

and therefore is favorable for a high tar yield and less coke formation in tar.