Vol. 11, Special Issue 10 (2022)

Author(s):
Shradha Shetty, John Abraham, Balusami C, Sabin George and Renuka Nayar

Abstract:
Anaerobic digestion being a complex process produces biogas which varies in its composition depending on the type of the substrate and operational conditions of the digester. Apart from methane (CH₄) the other gases are considered as impurities and their separation improves the calorific value of biogas. Thus, treatment of biogas mainly involves two steps viz., biogas cleaning during which trace unwanted gases are removed; and biogas upgrading during which CH₄ is separated from carbon-dioxide (CO₂). Thus, a study was carried out to upgrade the biogas produced from single stage anaerobic digester using two different purification systems viz., Treatment-1 (T₁) and Treatment-2 (T₂). In T₁, water vapour removal was by condensation mechanism, hydrogen sulphide (H₂S) using iron scrap and CO₂ using 30% ethanolamine while in T₂, water vapour was removed using activated alumina balls, H₂S by 100 cm bed of activated charcoal and CO₂ using 0.25 M NaOH. The water vapour removal percentage by condensation mechanism and activated alumina balls was 93.99% and 99.28%, respectively. The H₂S removal efficiency was 72.9% for iron scrap and 95.55% per cent for activated charcoal. The CO₂ removal percentage was 82.02% and 85.99% using ethanolamine and 0.25M NaOH solution, respectively. Overall, the results revealed that T₂ was 2.07% more efficient than T₁.