Industrial Decarbonization by a Gas Hydrate Process: Scale-up Studies on CO₂ Capture from Flue Gas

The increased frequency and scale of impacts due to climate change are closely correlated with increased greenhouse gas emissions in the atmosphere. In fact, anthropogenic carbon dioxide gas emissions are considered to be the largest cause of such globally visible events. Carbon dioxide (CO2) capture, combined with the conversion and sequestration of captured CO2, is one of the approaches that may reduce CO2 emissions. In this work, we optimized and developed a gas hydrate-based process for the capture of CO2 from a point source. The gas hydrate studies were performed at three different scales: microliters (10–100 μL), milliliters (10–100 mL), and liters (∼10 L) mainly to understand the thermodynamics, kinetics, and scale-up challenges in such processes. Apart from the process scale-up and crystallizer modifications, the effects of other variables, such as additives, simulated flue gas compositions (85% N2 + 15% CO2, and 70% N2 + 30% CO2), temperature, pressure, and gas volumes, were also considered during optimization. To establish an effective capture of carbon dioxide by the gas hydrate-based process, the equation of state was used to estimate the moles of CO2 molecules enclathrated, temperature, and pressure profiles for the estimation of induction times. The heat of formation of gas hydrates was calculated by developing a protocol using a micro-differential scanning calorimetry (μ-DSC) instrument, and the gas compositions were determined during the experiments using gas chromatography. For a better understanding of the process efficiency, the separation efficiency and split fraction (for CO2 recovery) were also determined. In the scale-up crystallizer, significantly higher molar consumption of CO2 was observed in the simulated flue gas mixture with a high CO2 concentration (70% N2 + 30% CO2) compared to the relatively less concentrated CO2 mixture (85% N2 + 15% CO2) in the presence of tetrahydrofuran (THF). The prime objective of the CO2 gas separation in this study was fulfilled by a scale-up setup, which demonstrated separation efficiencies of 9.51 for SFG-15 and 7.03 for SFG-30 mixtures.