Investigation of Simplifying Assumptions in Mathematical Modeling of Natural Gas Dehydration Using Adsorption Process and Introduction of a New Accurate LDF Model

In this study, a comprehensive mathematical model was developed to investigate the simplifying assumptions in modeling of natural gas dehydration by the adsorption process. In the developed model the variations of pressure, velocity, and temperature along the bed and the temperature changes inside the particles were considered. Convective heat and mass transfer were considered Outside the particles and a diffusion mechanism was taken into account for the heat and mass transfer inside the particles. A dual site Langmuir model was selected to predict adsorption equilibrium and the Peng-Robinson equation of state was used to calculate the gas compressibility factor. The experimental data of Mohamadinejad et al. [Mohamadinejad, H.; et al. Sep. Sci. Technol. 2000, 35, 1] was used to verify the model. Good agreement was observed between the predictions of the comprehensive model and the experimental data. The results showed that applying the assumptions of uniform temperature distribution inside the pellet (lump method), thermal equilibrium between gas and particles, and isothermal and isobaric conditions had no significant effects oil the predictions. It was also concluded that external mass transfer resistance was negligible at the industrial operating conditions of gas dehydration processes and common linear driving force models (LDFs) were not able to predict the performance of the dehydration bed well. Also, a new accurate correlation was introduced for an LDF proportionality coefficient applicable in gas dehydration systems. The predictions based oil the proposed correlation were in good agreement with the results of the comprehensive model. Using this new accurate LDF model instead of diffusion model saves a large amount of CPU time without a loss of accuracy.