Effect of Process Parameters on Slow Pyrolysis of Rice Straw: Product Yield and Energy Analysis

Abstract

Slow pyrolysis of rice straw was carried out in a bench-scale fixed bed pyrolysis reactor. The effect of pyrolysis temperatures (300, 400, 500, and 600 °C) and residence time (1, 2, and 3 h) on product yield distribution and energy yield was studied. The biochar yield decreased from 57.87-31.25 wt.% with a rise in pyrolysis temperature and residence time. The percentage of carbon increased from 65.92-86.01%, while the percentage of hydrogen and oxygen decreased from 5.14-1.62% and 25.16-9.77%, respectively, with an increase in temperature and residence time. A similar trend observed in bio-oil characterization. The biochar yield initially increased from 300-500 °C and then reduced. The gas yield gradually increased from 11.91-28.16 %, with a rise in pyrolysis temperature and residence time. The concentration of CO and CO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> decreased gradually from 41.81-29.66% and 54.02-38.46%, while H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> and CH <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> increased from 1.9-19.22% and 2.3-10.54%, respectively. The energy yield of biochar decreased from 63.76-39.94%, while bio-oil and gas yield increased from 25.02-40.73 % and 4.96-19.23%, respectively, with an increase in pyrolysis temperature and residence time.