Dynamic Modeling of Biogas Upgrading in Hollow Fiber Membrane Contactors
2014
Yan, Yunfei | Zhang, Zhien | Zhang, Li | Chen, Yanrong | Tang, Qiang
Membrane absorption is a novel method for acid gas removal compared to conventional separation techniques. The current study presents the simulation results using a computational fluid dynamics (CFD) method for biogas purification. A comprehensive two-dimensional (2D) mass-transfer model was developed and solved in a hollow fiber membrane contactor (HFMC) under a non-wetted condition. H₂O, triethanolamine (TEA), diethanolamine (DEA), monoethamolamine (MEA), and potassium argininate (PA) were used as the absorbent liquids. The effects of gas–liquid parameters and membrane characteristics on the CO₂ removal efficiency and absorption flux and CH₄ recovery were systematically examined and evaluated. The comparisons between model predictions and experimental data with various gas–liquid parameters were in good agreement. An increase of gas velocity and CO₂ content caused an increase of CO₂ flux and a decrease of CO₂ removal efficiency and CH₄ recovery; however, an increase of absorbent velocity and concentration caused an increase in the above three values. In addition, a smaller fiber inner diameter and membrane thickness and a longer module were good for the biogas upgrading process. It should be noted that the highest CO₂ flux coincided with the original module dimensions. The simulation predictions also showed that PA provided better membrane module performance than other absorbents. The order for CO₂ absorption efficiency and CH₄ recovery was PA > MEA > DEA > TEA > H₂O. Overall, the developed model provides the guidelines for selecting the optimum module properties and fluid conditions. The membrane gas absorption technique has shown great potential in biogas upgrading.
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