Modeling and simulation of a pressure-temperature swing adsorption process for dehydration of natural gas

Water vapor in a natural gas stream can result in line plugging due to hydrate formation, reduction of line capacity due to collection of free water in the line, and increased risk of damage to the pipeline due to the corrosive effects of water. Therefore, water vapor must be removed from natural gas to prevent hydrate formation and corrosion from condensed water. Molecular sieves are considered as one of the most important materials that are used as desiccant materials in industrial natural gas dehydration. This paper focuses on modeling of pressure-temperature swing adsorption (PTSA) process in a commercial two-layer adsorption system during sequential steps of cyclic operation to remove water from natural gas. The dynamic model equations were constructed from 4 mol balances; model molecule of water vapor in natural gas, a total mass balance, a pressure drop equation and two energy balances of solid and gas phases in the adiabatic column. Results reveal that about 1 m of the bed was overdesigned by vendor and it doesn't work in optimum condition. The influential parameters of the process were investigated through a parametric analysis of the process efficiency. For the sake of energy saving some suggestions were proposed for upgrading the design conditions with no significant effect on the purification performance. Results show that optimum conditions will be obtained using adsorption time 22 h and regeneration time 9 h with maximum temperature of 240 A degrees C.