PURIFICATION OF BIOGAS AND BOTTLING FOR ITS EFFECTIVE UTILIZATION

As a result of the dwindling petroleum resources, high cost of LPG and global warming resulting from fossil fuel, there is urgent need to explore the utilization of other potential alternative forms of ecofriendly fuels of which biogas is one. Biogas generated through anaerobic digestion showed potential to support access to renewable energy. However, variable biogas qualities present economic barriers and therefore require upgrading.  Biogas is a clean, valuable, renewable energy and also a secondary energy carrier produced from biodegradable organic materials (biomass) through anaerobic digestion. The main constituents of biogas are about 60% -70% methane (CH4) and 30% Р40% carbon dioxide (CO2) and traces of various quantities of contaminants, such as ammonia (NH3), water vapour (H2O), hydrogen sulphide (H2S), methyl siloxanes, nitrogen (N2), oxygen (O2), halogenated volatile organic compounds (VOCs), carbon monoxide (CO) and hydrocarbons. The quantities of these contaminants depend largely on the biogas source and method of production. Methane is the only useful constituent, others, especially H2S, water vapour and CO2 are contaminants and have greatly reduced the thermal efficiency and density. Biogas generation at low pressures and the absence of means for storing and transporting it has further hindered its use and therefore was removed to significantly improve the quality of biogas for optimal utilization. Biogas upgrading market is facing challenges in term of operating costs and energy consumption. In this study, the biogas production was carried out by using cow dung and a semi-continuous stirring tank reactor (CSTR) and the biogas purified. Biogas was collected and stored as it was produced through the methanization process over typical hydraulic retention times of 30 days. Proper mixing and handling of the feedstock is important for maximizing stable biogas yields. Gas chromatography and calorimetry characterized raw/purified biogas quantities and qualities before/after upgrading. The purification was achieved by passing the gas through columns of steel wool, static water scrubber and silica gel. The steel wool removed up to 98% H2S, the static water column removed 96% carbon dioxide and the silica gel removed about 97% water vapour. Thus 95% methane refinement was achieved. Compressing, bottling and making the biogas transportable was

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