Development of a novel bio char for CO2 capture and biogas upgrade: Static and dynamic testing

Abstract

The optimization of the pyrolysis of the spruce sawdust was conducted based on the yield, textural properties, and static capture capacity of the chars to generate a new micro porous char for biogas upgrade. The nature of the precursor (C: 45.68 %, H: 6.08 %, N: 0.15 %, and 0.34 % ash content) helped to tune the porosity of the char for capturing CO₂ from gas streams and biogas. The optimization of the pyrolysis at 700 °C, a heating rate of 10 °C / min and holding time of 1 hour, produced a microporous char with high yield, CO₂ capture capacity and CO₂/CH₄ selectivity. The presence of the oxygen and nitrogen-containing functional groups in the optimum char help in the selective capture of CO₂. The static CO₂ capture capacity of the optimum char was 1.98 mmol/g at atmospheric pressure and 25 °C (90 % CO₂ stream). The CSD (700−10−60) have capture capacity of 1.50 mmol/g (at a feed gas stream of 50 % CO₂ and adsorption temperature of 25 °C and 120 kPa) which is equivalent to Norit C and Calgon BPL. Hence, spruce sawdust can be used to produce efficient biochar for biogas upgrade (CO₂ capture) owing to high capture capacity and CO₂/CH₄ selectivity (around 3) and easy regeneration of the biochar for 10 consecutive cycles.