Volume 44 (2011) Issue 6 Pages 420-430
Combustion possibility of upgrade ECO coal as a blended fuel of commercially thermal power plant was investigated by thermogravimetric analysis (TGA), drop tube furnace (DTF) and ignition temperature (IT) tester. TGA results showed that combustion patterns of coal samples has the simultaneous devolatilization and oxidation reactions, and the fixed carbon contained with minor content in high moisture ECO coal (HM ECO) was slowly burned to high temperature than it of dry ECO coal (Upgrade ECO) due to heat loss of moisture evaporation. The linear regression for the Arrhenius plot to the experimental data is very good, and activation energies for overall combustion of bituminous C & A (Design C & A) and Upgrade ECO are 66.83 and 29.64 kJ/mol, respectively. It was derived that activation energies of 30%, and 50% Blends produced through mixing of Upgrade ECO of 30%, and 50% to Design C & A are 31.44 and 29.98 kJ/mol in reciprocal proportion to blending ratio. Test results show that the volatile content contained in coal samples area significantly improved the combustion reactivity. The conversion behavior of the coals observed in DTF was similar to that reflected in TGA. DTF studies showed that the combustion of all blends was also completed at residence time of around 1 second, set temperature range of 1,200°C similar to commercial coal fired plant. Although the Upgrade ECO has the highest conversion than the blends, it was not appropriate as the single pulverized fuel of coal fired plant because its initial deformation (IDT) and ignition temperatures of about 1,090 and 215°C, respectively, were too low to cause the slagging in boiler, and the firing at pulverizer. The IDT of the blends ashes of Upgrade ECO of less than 30% was about 1,250°C, and, was not expected to be associated with slagging and fouling in pulverized coal fired systems. The liability of spontaneous combustion of coal samples was increased with increasing the moisture and volatile contents whereas it of Upgrade ECO was the highest due to the high volatile content and thermal diffusivity. It was therefore proposed that the combustion of blends of Upgrade ECO with less than 30% was the most appropriate for the prevention of slagging and spontaneous combustion at the pulverized coal fired boilers, and, has the excellent combustion efficiency.