Characterization Study of Kütahya-Tunçbilek Lignite During Oxygen Enriched Combustion
Ozlem Uguz Hanzade Haykiri Acma Serdar Yaman
AbstractLignite is the most abundant energy source to generate energy in thermal power plants in Turkey. Thus, efficient and environmental-friendly use of lignite in electricity generation is of great importance. Because of this reason, clean coal technologies have been planned to achieve less emissions and increase the efficiency of the combustion in power plants. In this regard, oxygen enriched combustion (oxy-combustion) is regarded as one of the clean coal technologies, by which coal is burnt with oxygen concentrations higher than that in air. The aim of this study is to investigate the combined effects of temperature inside the furnace and oxygen ratio of the combustion atmosphere on the efficiency of coal combustion and the changes of the amounts of the C, H, N, S, O elements, mineral matter, and the morphologies of the residues which are left after combustion process. To do this, crushed and sieved lignite from Kütahya-Tunçbilek region were characterized by elemental, proximate and heating value analyses. After that, untreated sieved samples were subjected to heating at the temperatures of 200ºC, 450ºC, 800ºC under the atmospheres with the ratios of 21%O2+79%N2, 30%O2+70%N2, 40%O2+60%N2, and 50%O2+50%N2 in the horizontal tube furnace. Residues obtained after the process were characterized by elemental, proximate, heating value analyses, followed by XRD, FTIR and SEM characterizations. According to the results, it was observed that the effect of oxygen enrichment was more pronounced at high operation temperatures. However, the ratio of oxygen is important as it causes carbonization to proceed if the oxygen concentration is low. Moreover, it was confirmed that increasing temperature and oxygen concentration in the atmosphere inside the horizontal tube furnace caused the residues to have lower contents of aliphatic, aromatic structures. However, carboxylic and etheric structures were seen to be more resistant to these parameters. SEM results indicated increasing ash formation as the treatment temperature and oxygen ratio increased.