Thermogravimetry and differential scanning calorimetry of Kentucky bituminous coals
โ Scribed by John P. Elder; Mary Ben Harris
- Publisher
- Elsevier Science
- Year
- 1984
- Tongue
- English
- Weight
- 750 KB
- Volume
- 63
- Category
- Article
- ISSN
- 0016-2361
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โฆ Synopsis
A detailed investigation has been made of the thermal characteristics of six Kentucky bituminous coals undergoing pyrolysis in an inert atmosphere at three different heating rates. The specific heats of the coals and the enthalpy changes characterizing their thermal degradation were measured by differential scanning calorimetry. Thermogravimetry was employed to measure the attendant weight changes, which were used to normalize the heat flow data to unit sample weight, enabling a quantitative comparison of the thermal behaviour of the several coals. The specific heats of the dry coals lie in the range 1.21-l .47 J gK_', 1003OOC. The exothermic heat flow from 300 to 55OC, where the major weight loss occurs, has been associated with the primary carbonization process, the development of the plastic state, and the onset of secondary gasification, which is responsible for coke formation. In the high pyritic sulphur coals, the endothermic pyrite/pyrrhotite transformation at ti58o"C is clearly defined. A preliminary global kinetic analysis of the thermogravimetric data has been made, using a modified Kissinger equation at the maximum rate of weight loss. Activation energy and pre-exponential factor values of the order 198-220 kJ mol-' and 2-85 x 1 012 s-' have been obtained. These compare well with the limited published values for similar coals.
๐ SIMILAR VOLUMES
Results of exothermic heats involved during hydrogenation of twenty U.S. raw coals of varying rank at 5.6 MPa (gauge) and temperatures up to 570ยฐC are reported. The heat evolved during hydrogenation up to 57O'C decreases with increase in coal rank. A part of the total heat released during hydrogenat