Biogas upgrading with membrane

Biogas is a clean environment friendly fuel that is produced by bacterial conversion of organic matter under anaerobic (oxygen-free) conditions. Raw biogas contains about 55–65% methane (CH4), 30–45% carbon dioxide (CO2), traces of hydrogen sulfide (H2S) and fractions of water vapour. Pure methane has a calorific value of 9100 kcal/m3 at 15.5 ◦C and 1 atm; the calorific value of biogas varies from 4800 to 6900 kcal/m3. To achieve the standard composition of the biogas and calorific value of 5500 kcal/m3 the treatment techniques like absorption or membrane separation should be applied. Recent research on chemical and physical structure of the membrane, its separation properties, as well as optimization of membrane manufacturing process led to the development of new membranes with the specific separation properties, suitable for the gas mixtures separation. A study of new type membranes for biogas enrichment and purification is presented in the paper. Membrane processes have been identified as one of the most effective means for upgrading biogas and this topic has already received considerable attention the production of methane through the microbial degradation of organic wastes. This strategy does indeed offer the possibility of using a large variety of renewable feed stocks (food and agricultural wastes, manure, crop residues, municipal and industrial wastewater, landfill, etc.) for an alternative production of gaseous fuel. Several analyses have also shown that biomethane production through energy crops can lead to larger yields in Joule per hectare as compared to for instance ethanol or biodiesel. The new membrane material was resistant to the small concentrations of sour gases and assured the reduction of H2S and water vapour concentrations, as well. The required enrichment was achieved in the single module, however to prevent CH4 losses the multistage or hybrid systems should be used to improve process efficiency. In the paper the results of the tests of the CH4 enrichment was showed that using the capillary module with glassy polymers, such as polyimide membranes, it was possible to achieve the enrichment of CH4 from the concentrations of 55–85% up to 91–94.4%.

Biogas upgrading with membrane Keywords:

Biogas , Methane (enrichment) , Membrane process , Biogas upgrading , CO2-selective membrane