Modeling and Approximate Solution for Separation of Nitrogen and Methane in a Spiral Wound Membrane Module

In the present study, modeling of nitrogen and methane separation in a spiral wound membrane module has been performed. For this purpose, some simplifications have been made which although simplified the model and eliminated unnecessary complexities, does not reduced the accuracy and made it as a very useful applicable model. For this purpose, an approximate modeling technique for spiral wound membranes in separating binary gas mixture is used for investigation of effects of increase membrane area and feed specifications (such as flow rate, concentration and pressure) on N2/CH4 separation. The results showed that based on the membrane selectivity, any changes in flow rate, concentration and pressure of feed and membrane surface can cause improvement or decrement in methane recovery and methane concentration in the product flow.On the other hand, it was also found that increase in the membrane surface area, improves methane recovery in the methane selective membranesand decreases in the nitrogen selective membranes. Moreover, by increasing the membrane surface area, methane concentration in product stream decreases while it increases for nitrogen selective membranes. Then, it is necessary to establish a balance between the amount of methane recovery and methane concentration in the product.