Characterization and co-firing potential of a high ash coal with Bambusa balcooa

Two pre-treatment methods, i.e. torrefaction and low-temperature carbonization, were applied to a bamboo species, Bambusa balcooa'' at a temperature between 250 degrees C and 380 degrees C. The physicochemical characteristics and thermal behavior of the coal, raw bamboo and thermally treated bamboo sourced from South Africa were investigated using thermogravimetric analysis (TGA). The aim was to enhance the fuel quality and to determine the combustion potential of B. balcooa solely, or co-fired with a low rank bituminous coal. The co-firing of the raw and thermally treated bamboo samples with coal of 27.50% ash content was conducted in the absence of oxygen, using a ratio of coal inclusion of 10%, 30%, 50% and 75%. Results obtained from the proximate and ultimate analyses show a considerable difference in the quality of the raw bamboo from the thermally-treated samples. The ash content and fixed carbon dry basis'' of the raw B. balcooa (BB) were found to be 0.49% and 6.01%, respectively, with a calorific value of 18.53 MJ/kg. After the BB was torrefied (TBB) at 280 degrees C and carbonized (CBB) at 380 degrees C, a fuel with 3.63% ash content and 38.20% fixed carbon, with calorific values of 24.02 MJ/kg and 28.20 MJ/kg respectively was produced. The nitrogen content of the raw BB was found to be 0.22% while the sulfur was untraceable. Using the TGA data, activation energy (Ea) of 64.12 kJ/mol was obtained from the coal tested, which was higher than that obtained from the raw BB (11.24-31.60) kJ/mol. Higher Ea values were obtained as the thermal treatment temperature increased. The Ea values for the carbonized samples were within the range of (67.33-71.71) kJ/mol compared to the torrefied samples (43.70-44.70) kJ/mol. The TG curves were fitted using the Coats Redfern model. In summary, the results showed that the most effective mechanisms for controlling the combustion process in all samples under stage 3 carbon combustion'' were the chemical reaction models (O1, O2 and O3). (C) 2015 Elsevier Ltd. All rights reserved.