Evaluation of Thermochemical Characteristics of Solid Fuels from Sugarcane Pith and Fiber Produced by Torrefaction Process

Jarunee Khempila; Pumin Kongto

Authors

Jarunee Khempila Program of Physics, Faculty of Science and Technology, Rajabhat Mahasarakham University, Maha Sarakham, Thailand
Pumin Kongto Energy Technology Program, Faculty of Engineering, Prince of Songkla university, Songkhla, Thailand

Keywords:

Sugarcane, Pith, Fiber, Biomass fuel, Torrefaction

Abstract

This study focused on the use of sugarcane pith and fiber, which are processing by-products of the sugar industry, as a feedstock for the preparation of biochar fuels by torrefaction at temperatures ranging from 250 to 300^oC with a residence time of 30 minutes under a continuous supply of nitrogen. To determine the thermochemical characteristics of solid products and compare them with the raw biomass, fiber (cellulose hemicellulose and lignin), proximate (moisture content, fixed carbon, volatile matter and ash contents) as well as elemental (carbon, hydrogen, nitrogen, oxygen and sulfur) analyses were conducted; higher heating values (HHV) were also determined. The results revealed that torrefaction temperature exhibited larger effect on the hemicellulose degradation of the sugarcane pith when compared with the case of sugarcane fiber. Lignin was not significantly affected, however. The ash contents of raw sugarcane pith (13.9%) and fiber (1.8%) increased to 34.6% and 3.2% at 300^oC, respectively. The highest fixed carbon contents of the sugarcane pith and fiber were 20% and 25.1%, respectively, 50.4-88.7% higher than the original values. There was a reduction in the oxygen contents of the sugarcane pith and fiber, from 55.7 to 48.6% and 48.5 to 41.6%, while the carbon contents increased from 38.1 to 45.8% and 44.4 to 52.1 MJ/kg, respectively. These resulted in increased HHV of both sugarcane pith and fiber from 15.5 MJ/kg to 18.1 MJ/kg and 17.6 MJ/kg to 20.8 MJ/kg, respectively. The lowest sulfur content was noted in the torrefied sugarcane fiber, clearly illustrating that sulfur could be more effectively eliminated by the torrefaction process in the case of sugarcane fiber than in the case of sugarcane pith. Van Krevelen diagram clearly showed that torrefied sugarcane fiber had achieved coal characteristics as evidenced from the decrease in O/C and H/C molar ratios.

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