A COMPARISON OF THE PYROLYSIS OF COAL IN WIRE-MESH AND ENTRAINED-FLOWREACTORS

The properties of chars derived from coals of a wide range of rank pro duced in wire-mesh (WMR) and entrained-flow (EFR) reactors were compar ed. The WMR was operated at atmospheric pressure of helium or nitrogen with heating rates of 2-5000 K s(-1), temperatures up to 1773 K and r esidence time of 2-30 s. The EFR was operated at 1273 K with a residen ce time of 1 s in nitrogen at atmospheric pressure. The yield of volat ile matter from the EFR was consistently lower than that from the WMR; accordingly, the EFR chars were of significantly higher residual vola tile matter than the corresponding WMR chars. Differences in yields an d char reactivities were observed between pyrolysis in helium and nitr ogen. The extent of secondary reactions and experimental flow arrangem ents accounted for the remaining difference. The results show that in general there is reasonable agreement between the reactivities of the chars prepared under similar conditions by the two techniques. The dif ferences between the results for the two techniques are discussed in t erms of variations in the experimental conditions and their effect on char properties. Novel data for pyrolysis in hydrogen on a wire mesh a re included to demonstrate the effect of pressure over the range 0.25- 7 MPa.