A simulation study of CO₂ gas adsorption with bottom ash adsorbent from palm oil mill waste using computational fluid dynamic (CFD)

Abstract

Biogas is a cost-effective, efficient, environmentally friendly, and renewable alternative energy source. While biogas contains CH4, it also contains impurities in the form of 27–45% CO2 gas. Therefore, it is necessary to purify biogas by removing CO2 gas as it can reduce the calorific value of CH4, the main component of biogas. The process of methane purification can be achieved through adsorption. Bottom ash, derived from palm oil mill waste, shows great potential for methane purification by effectively adsorbing CO2. This research simulated the methane purification process using the computational fluid dynamics (CFD) method with the student version of the ANSYS R20 software. The study utilized an adsorbent made from bottom ash obtained from palm oil mill waste. The main objective was to investigate the performance of bottom ash as an adsorbent for removing CO2 gas in a continuous gas flow within an adsorption column. The study involved varying the column bed height (4 cm, 8 cm, 12 cm) and gas flow rate (10 L/min, 15 L/min, 20 L/min). The results showed that the highest efficiency in removing CO2 gas was 84.53% with a bed height of 12 cm and a flow rate of 10 L/min, while the lowest efficiency was 47.87% with a bed height of 4 cm and a flow rate of 20 L/min. Furthermore, the highest adsorption capacity for CO2 gas was 1.64 mg/g with a bed height of 12 cm and a flow rate of 10 L/min, while the lowest capacity was 0.93 mg/g with a bed height of 4 cm and a flow rate of 20 L/min. The linearization of adsorption isotherm data indicated that the CO2 gas adsorption process using bottom ash adsorbent followed the Langmuir model.

Keywords

• adsorption
• bottom ash
• adsorption capacity
• removal efficiency