Thermal behaviour studies on coal-biomass blends during pyrolysis and combustion via thermogravimetric analysis / Zubri Zakaria

Thermal behaviour of raw and demineralized Mukah Balingian coals, biomass and coal-biomass blends at different weight ratios (i.e. 90:10, 80:20, 70:30 and 50:50) during pyrolysis and combustion conditions was studied by using thermogravimetric analysis at different heating rates in the range of 5-60°C/min. The results thus far showed that the thermal events of the raw and demineralized biomass materials during pyrolysis and combustion were mainly contributed by the decomposition of hemicellulose and cellulose that evolved at lower temperature in the range of 295333°C and 346-376°C, respectively. The raw and demineralized coal decompositions, however, revealed almost identical thermal events with the appearance of a single evolution peak that occurred at higher temperature regime in the range of 415-465°C. Apparently, no interaction was seen between the raw and demineralized coal-biomass blends during pyrolysis and combustion. However, by blending of 50 wt% coal and bio-coal, the DTG curves showed a single evolution peak indicating the comparable reactivity between the two fuels during combustion. Further, the reactivity of the demineralized coal and demineralized biomass materials increased with increasing in heating rates and were more reactive in comparison to the raw samples and these were proven by observing the profiles of char remaining after pyrolysis. The kinetic study of coal, biomass and their blends during pyrolysis was also been carried out to determine the activation energy and pre-exponential factors. The 50:50 blends of coal-rice husk and coal-rice straw with respect to the coal volatile matter released revealed the lowest activation energy of 201 and 217 kJ/mol, and pre-exponential factors of 7.46 x 1011 min"1 and 9.70 x 1012 min"1, respectively. In addition, for the coal-sugarcane bagasse, the lowest activation energy was 211 kJ/mol with pre-exponential factors of 3.60 x 1012 min"1 for the blend ratio of 80:20. Likewise, the 80:20, 70:30 and 50:50 blends for the demineralized coal-rice husk, coal-rice straw and coal-sugarcane bagasse showed the lowest activation energies of 170, 173 and 163 kJ/mol and pre-exponential factors of 2.37 x 109 min"1, 5.82 x 109, and 1.77 x 109min"1, respectively.