A theoretical and industrial study of component co-adsorption on 3A zeolite: an industrial case

The 3A zeolite is an excellent adsorbent for natural gas dehydration due to low energy requirement in regeneration step and easy operation. To perform a reliable modeling, a good equilibrium adsorption isotherm is mandatory. Accordingly, water, methane, methyl mercaptan (M-mercaptan) and CO2 adsorption isotherms and also the competitive adsorption loading versus temperature are described for the system using molecular simulation and mathematical models. It is found that CO2 competes with water for adsorption on 3A and lower temperature is required for selective removal of water. The mathematical model results showed that M-mercaptan and CO2 quickly adsorb on 3A and capacity of 3A for water adsorption is reduced when impurities exist. The regeneration of saturated bed showed that higher temperatures cause lower desiccant loading. The experiments showed that co-adsorption of mercaptans leads to off-spec regeneration gas and some process modifications are then conducted to decrease its consequences. Finally, a decrease in regeneration gas temperature from 240 to 200 degrees C and adsorption time from 16 to 12 h resulted in lower gas flaring from 1.2 x 10(6) standard cubic meters per day (MMSCMD) to 0.3 MMSCMD, in industrial scale.