Effects of Grain Size and Rotational Speed on the Bio-Oil Yield in a Fast Pyrolysis Reactor Employing a Single Tapered Screw Extruder

Abstract

The effects of process parameters of biomass grain size (ranging from 0.425 to 3.35mm), rotational speed (ranging from 20 to 60rpm) and the pyrolysis temperature (ranging from 400 to 550 oC) on the yield of bio-oil were investigated in this study by using a fast pyrolysis reactor with a single tapered screw extruder. This study gives the optimal pyrolysis temperatures and rotational speeds for different grain sizes to achieve peak bio-oil yield. The results indicate that higher feed rates are required for larger grain sizes to achieve peak bio-oil yields. For instance, a 20rpm rotational speed is for 0.425~1.18mm grain sizes (50~57% bio-oil yield), while a 40rpm rotational speed is for 1.7~3.35mm grain sizes (56~60% bio-oil yield). This implies that the productivity of bio-oil can be significantly increased in the current system. For the case of 2.5~3.35mm grain size, which corresponds to an optimal rotational speed of 40rpm, the production rate was estimated to be around 4kg/h.

Experimental Investigation of Fast Pyrolysis of Arundo Donax in a Novel Paddle Reactor

“…Next parameter which is to be controlled to obtain high bio-oil yield is the size of the feedstock. [26]…”

“…The non-condensable gases were not measured and were calculated by mass balance. Another study demonstrated a novel auger type which consisted of a single tapered screw extruder [26]. The diameter of the screw increased gradually from the start by 2° taper such that the gap is reduced.…”

“…Also, vapor residence time was few seconds (exact number not reported) and vapors were condensed in a proprietary condenser. The bio-oil yield for the feedstocks tested were in the range of 40-60% and the yields of char were in the range of 9-30%, noncondensable gases yield was not measured.In 2011 several studies contributed to the pool of knowledge in this field by using different type of feedstocks in novel auger reactors[17] [24][26]. Douglas fir wood was used by[17] to study the effect of temperature on the bio-oil yield.…”

“…The screw reactor used was a novel reactor with a decreasing flight depth from reactor inlet to outlet which presses the biomass to the reactor and hence enhancing the heat transfer. Although this concept is previously used by[26]. The feed capacity was about 1-6 kg/h but only 1-1.5 kg/h feed rate was employed.…”