Valorization of biogas through simultaneous co2 and h2s removal by renewable aqueous ammonia solution in membrane contactor

Upgrading biogas into biomethane not only improves the biogas utilization as vehicle fuel or natural gas substitute, but also reduces the greenhouse gases emissions. Considering the principle of engineering green energy process, the renewable aqueous ammonia (RAA) solution obtained from biogas slurry was used to remove H2S and CO2 simultaneously in the hollow fiber membrane contactor. RAA was mimicked in this study using the ammonia aqueous solution mixed with some typical impurities including ethanol, acetic acid, propionic acid, butyric acid and NH4HCO3. Compared with the typical physical absorption (i.e., pure water) removing 48% of H2S from biogas, RAA with 0.1 mol center dot L-1 NH3 could remove 97% of H2S. Increasing the NH3 concentration from 0.1 to 0.5 mol center dot L-1 could elevate the CO2 absorption flux from 0.97 to 1.72 mol center dot m-2 center dot h-1 by 77.3%. Among the impurities contained in RAA, ethanol has a less impact on CO2 absorption, while other impurities like CO2 and acetic acid have significant negative impacts on CO2 absorption. Fortunately, the impurities have a less influence on H2S removal efficiency, with more than 98% of H2S could be removed by RAA. Also, the influences of operating parameters on acid gases removal were investigated to provide some engineering suggestions.