Low-Temperature Phase Separation of CO₂ from Syngas Mixtures─Experimental Results

To mitigate the increasing anthropogenic CO2 emissions, hydrogen is pointed to as a potential low-emission alternative fuel for a range of applications. Gray hydrogen from natural gas reforming is the dominant industrial hydrogen source globally. If CO2 capture and storage can be added with minimal efficiency reductions, blue hydrogen can reduce the carbon footprint drastically. A novel technology option for blue hydrogen production, is the use of proton conducting membranes for hydrogen purification combined with low-temperature condensation and phase separation of CO2 from the retentate gas. This work presents results from 15 experiments for low-temperature phase separation and purification of CO2 from five-component mixtures representative for retentate and tail gas compositions. The experiments have been conducted with feed rates between 120 and 307 kg/h and with CO2 feed fractions between 56 and 82 mol %. The main separator pressures and temperatures range between 40 and 70 bar, and −55 and −45 °C, respectively. Final CO2 product purities up to 99.90 mol % have been measured. The purity can be controlled through the pressure level in the flash purification separator and the temperature upstream of the inlet throttling valve. Experiments and corresponding predictions based on GERG-2008 and Peng–Robinson are generally consistent.