95/01235 Coke quality control method from moisture-adjusted coal

Abstract

The artificial coals (AC) or coal models were prepared from sawdust, lignite and cork by the method of hydrothermal carbonification. The specific techniques used to study their pyrolytic behaviour were thermogravimetry, Gieseler plastometry and differential thermal analysis (DTA). The principal conclusions drawn are: 1.(1) The initial stage of pyrolysis of AC can be considered to be governed by an overall reaction of first order, as in the case of natural coals.2.(2) All caking types of AC showed quite low softening points (75–210 °C), the values for sawdust AC being lower than those for the cork AC. The latter showed fairly sharp peak values of the temperature of maximum fluidity, but the sawdust AC showed only a range of temperatures of maximum fluidity, the upper limit being less than the maximum fluidity temperature of the cork AC. However the temperatures of resolidification were consistently high, namely 425 °C and above, thus bringing in a significant point of similarity with natural caking coals.3.(3) The value of maximum fluidity was very high for one AC sample, exceeding 27000 dial div./min. Such a high value is rare for natural caking coals. With the latter, no correlation could be observed between the caking properties and maximum fluidity. Hence the role played by the stability of the plastic mass may be the more dominant factor in the caking process.4.(4) From the comparison of the softening temperatures and the temperatures of active decomposition of the AC, it is inferred that the process of initial softening of coal may be physical in nature.5.(5) The AC indicated an overwhelming exothermicity in their primary pyrolysis, thus behaving like the natural coals studied under similar experimental conditions.