Analysis of the Oxidation Behaviors of the Coal Samples kept Under Different Storing Conditions from the Aspect of Thermogravimetry and Oxygen Deficiency

ABSTRACT

Coal samples crushed and ground under 74 µm and 500 µm were exposed to oxidation in a deep freezer (−25°C), nitrogen tank (18°C) and oven (30°C) for a period of 16 weeks. For the first 8 weeks, the samples were in zipped plastic bags while they were kept open in trays for the rest of the duration. Thermogravimetric analysis of 10 mg samples was realized by burning them out up to 900°C with a constant heating rate of 10°C/min. and a dry air flow rate of 5 ml/min. Additionally, oxygen consumption rates of the samples were also determined during the experimental work together with a trial to put forward the involvement between the values of the combustion profiles (activation energy, ignition and peak temperatures) of the samples and the rates of oxygen consumption. According to the results obtained, it was ascertained that the coal samples stored in the deep freezer have advantages comparatively over the samples kept under other storing conditions (nitrogen tank & oven). According to the results of the experiment; it has also been determined that the consumption of oxygen increases after the temperature of the coal reaches 90°C. In the activation energies calculated for 4 different reaction degrees, the highest correlation coefficient was found at the degree of 0.5 for all samples. The activation energies were determined to be between 28.0413 and 39.5839 kJ/mol. In addition, it was also indicated that the activation energy of the samples was decreased while the rates of oxygen consumption were increased with the decrease in the particle size.

KEYWORDS:

• Activation energy
• coal
• oxidation
• oxygen consumption rate
• thermogravimetry

Acknowledgments

Authors present deeply their gratitude to the Management of Western Lignite Corporation as well as the Commission of Scientific Research Projects for Dumlupinar University (Project Number 2009-06) for the great support in the realization of this work.