(374ap) Changes In Moisture, Carbon, Nitrogen, Sulphur, Volatiles and Calorific Value of Miscanthus Samples During Torrefaction

Torrefaction tests were carried out on miscanthus samples to understand the changes in chemical composition at temperatures of 250-350°C and residence times of 30-120 min. The raw material chemical composition in terms of moisture content, moisture free carbon (C), hydrogen (H), nitrogen (H), sulphur (S), volatiles (V) and moisture and ash free calorific value (CV) were 7.97%, 47.73%, 5.85%, 0.28%, 0.02%, 83.29% and 8423 BTU/lb, respectively. Torrefaction at temperatures of 250°C and residence time of 30 min resulted in significant decrease in moisture by about 82.68%, but the other components, C, H, N, S and V changed marginally. Increasing the torrefaction temperature to 350°C and residence time to 120 min further reduced the moisture to a final value of 0.54% (a 93.2% reduction compared to original) and also resulted in a significant decrease in the other components, H, N, and V by 58.29%, 14.28% and 70.45%, respectively. The carbon content at 350°C and 120 min increased by about 4% and sulfur values were below the detection limits. The calorific values increased by about 5.59% at 250°C and 30 min whereas at 350°C and 120 min the increase was much greater, about 75.61%, and resulted in a maximum degree of carbonization of 1.60. The H/C ratio decreased with an increase in torrefaction temperature where a minimum value of 0.6 was observed at 350°C and 120 min. The regression equations developed with respect to torrefaction temperature and time has adequately described the changes in chemical composition with a lowest r2 value of 0.82 for volatile content and highest 0.96 for carbon content. The surface plots developed based on the regression equations indicated that torrefaction temperatures and time of 300-350°C and 30-120 min can help to maximize carbon, calorific value and degree of carbonization to 49.4%, >11, 990 BTU/lb and 1.4 and minimize moisture, nitrogen, volatile and H/C ratio to 0.525-0.725, 2.9-3.9, 0.225-0.235 and <1.4