Influence of Pyrolysis Operating Conditions on Bio-Oil Components: A Microscale Study in a Pyroprobe

A fast pyrolysis process has emerged as one of the techniques to produce transportation fuels using various biomass types that are regionally important It is well understood that high heating rates, very small particles with low mass transfer limitations, and moderate operating temperatures are essential for obtaining, high yield of liquid from the fast pyrolysis process. However, how the heating rates and operating temperatures would influence individual compounds in the liquid obtained from the fast pyrolysis process has not been studied in detail. Therefore, a microscale pyrolysis study was performed by changing different parameters (biomass type, filament heating rate, and final pyrolysis temperature) to understand the influence of these operating parameters on each compound formed during the process. Two biomass types (pine wood and switchgrass) were selected for this study: (i) pine wood was selected because of its availability in the southeastern region of the United States, and (ii) switchgrass was chosen because it has been identified as one of the bioenergy crops in the United States. Pyrolysis temperatures were changed from 450 to 750 C in increments of 50 C, whereas the heating rates selected were 50, 100, 500, 1000, and 2000 degrees C/s. Twenty-eight bio-oil compounds were quantified in each experimental condition. This study found that phenols and toluene concentrations increased with the increase in pyrolysis temperature irrespective to the biomass type. On the other hand, the change in the yield of ketones, furans, and guaiacols with the change in pyrolysis temperature depended on the type of biomass. The effect of filament heating rate on bio-oil yield was not statistically significant because the biomass heating rate was almost constant irrespective of different filament heating rates.