Pyrolysis of Switchgrass (Panicum virgatum L.) at Low Temperatures within N2and CO2Environments: Product Yield Study

High Resolution Image Download MS PowerPoint Slide Bioproducts and biofuels production from pyrolysis might benefit from recycling CO 2 within the process instead of using conventional inert gases such as N 2 . In this study switchgrass ( Panicum virgatum L.) was pyrolyzed within CO 2 and N 2 environments at 300, 400, and 500 °C for 2.5 min in a labscale fixed-bed reactor of 25 g/batch capacity. Chars, liquids, and noncondensable gases were monitored and characterized and yields were compared. A significantly lower liquid yield was observed at 300 °C–CO 2 in comparison to a 300 °C–N 2 environment, which was reflected with the char volatile content being higher under 300 °C–CO 2 and within the elemental composition of the solid and liquid products. Carbon dioxide also showed an effect at 500 °C, where liquid and gas yields significantly reduced and increased, respectively. At 400 °C–CO 2, CO concentrations were lower and CO 2 was higher compared to the levels at 400 °C–N 2, while at 500 °C–CO 2, CO concentrations were higher, CO 2 was lower, and CH 4 was lower compared to levels at 500 °C–N 2 . At 500 °C, a significant ash content reduction with respect to original biomass was observed only in the CO 2 environment, suggesting that CO 2 may effect inorganic content and subsequently the feedstock conversions since some feedstock inorganic elements are known to play a catalyst role along these reactions. Additional tests were conducted by following regular 500 °C tests with a char air quench. This resulted in a char specific surface increase of about 20 times; CO 2 and N 2 initial environments confounded.