Abstract—This study focused on upgrading waste straw by developing the technology of microwave-imduced torrefaction and investigating the key operating parameters to improve the energy density and hydrophobicity of biomass for better feedstock for the production of renewable energy. The experiments were conducted under inert environment and atmospheric pressure in a fixed-bed batch reactor putting in a self-designed microwave facility. Factors including microwave power (250 to 450 W), reaction time (10 to 30 min) and moisture content (8 to 50%) were evaluated and the torrefaction temperature was monitored and controlled in the range of 200 to 300 ℃. It was found that the shape and fullness of the reactor as well as the position and direction of the thermocouple in the microwave facility significantly affected the efficacy of microwave-induced torrefaction, while the influences of nitrogen flow-rate and moisture content of the biomass were negligible. With the increase of microwave power from 250 to 450 W, the content of fixed carbon and ash, higher heating value (HHV) and energy density increased in the torrefied straw. TGA and DTG confirmed the evaporation of moisture as well as the decomposition of hemicellulose and cellulose in biomass structures, and microwave power was the key factor affecting the torrefaction temperature so as to the energy yield and density of torrefied biomass. Straw torrefied under 450 W for 30 min showed characteristics similar to those of blended coal with HHV approaching to that of bituminous coal. With further optimization of microwave torrefaction parameters (power and reaction time), torrefied straw has potential for the substitution of coal used in pulverized coal-fired furnace.
Index Terms—Microwave-induced torrefaction, rice straw, energy density, thermogravimetric analysis.
Y. L. Lin is with the National Kaohsiung First University of Science and Technology, Kaohsiung 824, Taiwan (e-mail: yililin@nkfust.edu.tw).
[PDF]
Cite: Yi-Li Lin, "Effects of Microwave － Induced Torrefaction on Waste Straw Upgrading," International Journal of Chemical Engineering and Applications vol. 6, no. 6, pp. 401-404, 2015.
