CHANGES IN MOISTURE, CARBON, NITROGEN, SULPHUR, VOLATILES, AND CALORIFIC VALUE OF MISCANTHUS DURING TORREFACTION

摘要

Torrefaction tests were carried out on miscanthus samples in order to understand the changes inchemical composition at temperatures of 250–350oc and residence times of 30–120 minutes. The rawmaterial chemical composition was moisture content 7.97%, moisture-free carbon ? 47.73%,hydrogen (H) 5.85%, nitrogen (N) 0.28%, sulphur (S) 0.02%, volatiles (V) 83.29% for volatiles, andmoisture and ash-free (MAF) calorific value (CV) 8423 BTU/lb (19.59 MJ/kg). Torrefaction attemperatures of 250oc and residence time of 30 minutes resulted in a significant decrease in moistureby about 82.68%, but the other components, C, H, N, S, and V changed only marginally. Increasing thetorrefaction temperature to 350oc and residence time to 120 minutes further reduced the moisture to afinal value of 0.54% (a 93.2% reduction compared to original) and also resulted in a significantdecrease in the other components, H, N, and V by 58.29%, 14.28%, and 70.45%, respectively. Thecarbon content at 350oc and 120 minutes increased by about 4% and sulfur values were belowdetection limits. The calorific values increased by about 5.59% at 250oc and 30 minutes, whereas at350oc and 120 minutes, the increase was much greater (about 75.61%) and resulted in a maximumdegree 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 350oc and 120 minutes. The regression equationsdeveloped with respect to torrefaction temperature and times have adequately described the changes inchemical composition. The surface plots developed based on the regression equations indicate thattorrefaction temperatures of 300–350oc and residence times of 30–120 minutes residence time canhelp to increase carbon content, calorific value, and degree of carbonization to > 49.4%, >11,990BTU/lb (27 MJ/kg), and 1.4, and reduce moisture, nitrogen, volatile, and the H/C ratio to 0.525–0.725%, 0.225–0.235%, <50 %, and <1.0.