Preecha Kasikamphaiboon, Juntima Chungsiriporn, Charun Bunyakan, and Wisitsree Wiyaratn

pp. 683 - 691

Abstract

Biogas production and utilization is an emerging alternative energy technology that has gained importance since the
price of oil and gas has increased steadily over the last two decades. Biogas primarily consists of methane (CH₄
) and carbon
dioxide (CO₂
) with smaller amounts of hydrogen sulfide (H₂
S) and ammonia (NH₃
). For many applications the quality of biogas
has to be improved. The main parameters that may require removal in upgrading systems are CO₂
 and H₂S. This work presents
the study of simultaneous absorption of CO₂
 and H₂S by Monoethanolamine (MEA) solution in a packed column. Simulated
biogas containing 40% CO₂
 and 60% N₂
 and biogas generated from an anaerobic digestion plant were used as feed gas streams.
The effects of gas flow rate, L/G ratio and absorbent concentration were investigated. The performance of the system was
found to vary with process parameters. Increasing L/G ratio and MEA concentration causes the system efficiency to increase
whereas increasing gas flow rate results in lower efficiency. An operating condition of L/G ratio of 83.3 ml/L, gas flow rate of
3 L/min and MEA concentration of 3 mol/L was found to remove more than 99.5% of CO₂
 and H₂S from biogas. The volumetric
overall mass-transfer coefficient (K_Ga_v) for CO₂
 removal initially increases with increasing gas flow rate up to a certain value
beyond which the coefficient becomes essentially constant. The K_Ga_v
 also increases with increasing L/G ratio throughout
the range tested in this study.