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

The properties of chars derived from coals of a wide range of rank produced in wire-mesh (WMR) and entrained-flow (EFR) reactors were compared. 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 residence time of 2-30 s. The EFR was operated at 1273 K with a residence time of 1 s in nitrogen at atmospheric pressure. The yield of volatile matter from the EFR was consistently lower than that from the WMR; accordingly, the EFR chars were of significantly higher residual volatile matter than the corresponding WMR chars. Differences in yields and char reactivities were observed between pyrolysis in helium and nitrogen. The extent of secondary reactions and experimental flow arrangements 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 differences between the results for the two techniques are discussed in terms of variations in the experimental conditions and their effect on char properties. Novel data for pyrolysis in hydrogen on a wire mesh are included to demonstrate the effect of pressure over the range 0.25-7 MPa.