Ramesh Babu Nallamothu, Abyot Teferra, B.V. Appa Rao
In the present scenario of dwindling petroleum resources and global warming, exploring other avenues for ecofriendly fuels became essential. Biogas which is a clean and environmental friendly fuel emerged as one of the potential alternative fuels. Raw biogas contains about 60-70% methane (CH4), 30-40% carbon dioxide (CO2), traces of hydrogen sulfide (H2S) and fractions of water vapours. But its wide spread use is hampered by the associated problems like low energy density due to the presence of impurities, generation at low pressures and the absence of means for storing and transporting. In this context this work intends to design and establish a facility at the site of biogas production in the campus for purifying, compressing, bottling and making it transportable. This can be done by compressing the gas in cylinders which was possible only after removing its CO2, H2S and water vapour components. To increase the energy density of the gas, different experiments were conducted in removing incombustible and corrosive gas. To remove this impurities steel wool, water and silica gel was used. The steel wool is to react with the hydrogen sulphide, the water is to reduce the percentage of carbon dioxide and the silica gel is to reduce the presence of water vapour in the purified biogas. Experiment showed that, the methane concentration available in the raw and purified biogas was 68 ± 2.52 % and 90 ± 1.53 % respectively. Compression of purified biogas was carried out by using a hermetic reciprocating type refrigerant compressor and bottled into normal LPG cylinder. Compression of biogas was carried out up to an absolute pressure of 5 bars in total of 12-14 minutes. In order to evaluate the impact of biogas purification on heating value, purified and raw biogas was used to heat 500 ml of water and took 4.54 ± 0.03 and 5.62 ± 0.02 minutes respectively.