Torrefaction of Timothy Hay: Optimization using response surface methodology (RSM)

Abstract. Improving fuel quality of agricultural residues for efficient combustion can be a good alternative to partially replace the use of coal by renewable energy source and then to reduce carbon dioxide emissions. Timothy hay (TH) is one of the abundantly available agricultural residues in New Brunswick, Canada. The use of Timothy hay has limited by its low heating value, low bulk density, and storage issues. These limitations can be minimized by torrefaction process and no such work has been reported in the literature. This study thus performs a parametric study on torrefaction of Timothy hay by varying torrefaction temperature, heating rate, and residence time. Higher heating value, proximate analysis, and ultimate analysis were performed to characterize the solid product. Results suggested that temperature has significant impact on the quality of torrefied biomass. Carbon content of TH increases to 59.31% at 300ºC, 45min, and 30ºC/min, which improves the higher heating value by 26% compared that to raw TH. Response Surface Methodology (RSM) was used to develop models for mass yield, and energy yield. The optimized operating conditions were found to be at 278.7ºC, residence time of 15 min, and heating rate of 10ºC/min. This work would help to increase the use of Timothy hay for heat generation and for pellet production and to achieve renewable energy target set by federal and provincial governments of Canada.