Investigation on the transient enthalpy of coal combustion

摘要

The transient enthalpy (Ah) of coal/char combustion of the three different coals (including anthracite,bituminous,and lignite) during the process of combustion is determined as a function of burn-off degree by using thermo-gravimetric-differential scanning calorimeter (TG-DSC) simultaneous thermal analyzer,and The error of determining calorific values of coals/chars is less 5% compared the results of TG-DSC with that of an automatic isoperibol calorimeter.It is found that In the initial stage,all the Ah of coals are greater than that of the char pyrolysized from parent coal for many of volatiles contained more a great deal of heat per unit mass oxidized at low temperautre,it also imply that coal is more easily ignited than char corresponded;And in the middle stage,all the Ah of coals is lower than that of the char pyrolysized,so the pyrolysized char oxidation can supply much more of thermo-energy per unit mass.Ah are almost a constant when the burn-off degree is equal to between 0.35/0.15 and 0.95/0.85 for ZCY bituminous coal/char and JWY anthracite/char,between 0.35/0.35 and 0.75/0.9 for SLH lignite/char;In the later stage, the Ah of the coal/char decreased with the burn-off degree,it imply that the activity of the coal/char decreases. Therefore,coal pyrolysis changes not only the structure of char,but also the property of release heat;the transient enthalpy of coal/char combustion has been in change with the burn-out degree.