Investigation of the coals stocked under different storing conditions from the point of spontaneous combustion behaviours through thermogravimetry and surface adsorption mechanisms – tuncbilek lignite case

In the present work, oxidation behaviours of coal stocked under different storing conditions in the laboratory environment have been examined by the aid of measurements carried out for thermogravimetry, oxygen consumption and spontaneous combustion liability. The coal samples with average particle sizes of 35 and 200 meshes taken from Y4 lignite panel of Beke-Yörgüç in Tunçbilek region have been stored in nitrogen tank (18 °C), deep freeze (-25 °C) and oven (30 °C) at three different temperature conditions for 16 weeks. For the first 8 weeks, the samples have been kept in sealed plastic bags while they have been taken out of the bags for the remaining 8 weeks. In order to realize the thermogravimetric analysis of the 10 mg samples, they have been heated up to 900 °C under 10 °C/m constant heating rate together with a dried airflow rate of 5 ml/m. While kinetic analyses of the samples have been made by employing Coats-Redfern method, the ignition and peak temperatures and activation energy have also been defined for each sample. Additionally, the oxygen formation rates and the measurements of spontaneous combustion susceptibility of the samples have been achieved by the experimental mechanism set up in the laboratory. The crossing point temperature technique have been utilized for the definition of the spontaneous combustion liability of the samples while an oxygen analyzer has been used for the determination of their oxygen consumptions. With a data set obtained from experimental works; it can be concluded that the samples kept in the deep freezer have significant advantages in comparison to other storing conditions. It can also be stated that the particle size has an important effect on activation energy, ignition and peak temperatures together with oxygen consumption and spontaneous combustion tendency. Finally, it has also been observed that the variations taking place in the chemical compositions of the coal samples throughout the experimental studies have a key role on the coal oxidation.