Modeling and simulation of an industrial adsorption process of dehydration of natural gas in 4A molecular sieves: Effect of adsorbent aging

Abstract

Adsorption in molecular sieves is the number one choice for the dehydration of natural gas in offshore platforms. Many phenomenological and mathematical approaches have been used to describe this unit operation. However, the effect of aging on the operation performance, and consequently the adequacy of these models to describe operational field conditions, has been seldom assessed. This work presents the simulation of an industrial unit of natural gas dehydration with 4A molecular sieves in different cycle numbers using a phenomenological model. First, the most adequate equilibrium isotherm to describe experimental data of pure compound adsorption (viz., the dual-site Langmuir isotherm) was determined. Second, momentum, mass, and energy transfer equations were implemented, and the modeling of literature adsorption data was used to verify the adequacy of the developed equations. Finally, an industrial dehydration unit was modeled using the same approach, and calculated breakthrough times were compared to field data. In conclusion, the premature aging of molecular sieves in industrial operation appears as a defining factor in equipment performance.

Keywords

• Natural gas dehydration
• Adsorption
• Molecular sieves
• Modeling