PI: Prof. Jayesh Bellare, Department of Chemical Engineering

Co-PI: Prof. A. K. Suresh, Dept. of Chemical Engineering

Tata Fellow: Haridarshan Patel (2019-21)

Biogas technology is being widely utilized in India and across the globe. The gas generated is usually targeted to be used for thermal applications such as cooking, heating and power generation. The heating value of biogas (16 to 20 MJ/Nm3) is much lower than that of Liquefied Petroleum Gas (LPG) (46.1 MJ/kg) and considered to be a major impediment for its potential application. The improvement of the heating value of biogas is one of the aims of conditioning. Higher percentage of carbon dioxide (CO2) (ranging from 30-50 per cent) adversely affects the gas transmission grid, appliances or end‐users. Therefore, increasing the calorific value by removing CO2 from raw mixture is necessary for extracting the maximum energy from biogas. Several technologies are used for the conditioning of biogas. However, most of the technologies are not scalable and require huge space. In contrast, the major advantages of membrane based systems are high energy efficiency, low capital costs, robustness of the process, ease of operation and maintenance and a small footprint due to high packing densities of membranes in compact modules. Therefore, in the present work, a hybrid process based on membrane separation and water absorption is selected for biogas conditioning.

Recently, a few studies on water swollen membranes were published using commercially available reverse osmosis membranes, where in vapor present in raw biogas mixture was condensed inside membrane matrix, to enhance CO2 separation and CO2/CH4 selectivity (Kárászová et al., 2012), (Dolejš et al., 2014) & (Saeed et al., 2017). This process combines the advantages of solubility of polar gases in water with high surface area provided by the dense separation layer of membranes, for enhanced solution diffusion. In the current project, novel hydrophilic membranes will be developed to enhance the CO2 separation performance of water swollen membranes. This will be achieved by making composite membranes containing hydrophilic nanoparticles. The hydrophilic membrane morphology is expected to trap the condensed vapours inside the membrane matrix, which will ultimately enhance CO2 separation from biogas. The current research is expected to result in reduction in use of petroleum based fossil fuels such as petrol, diesel, and LPG, leading to monetary and environmental benefits.