Separation of Nitrogen from Natural Gas using Inorganic Membrane

The presence of nitrogen as an inert in natural gas created a main issue of low heating value (calorific value) of the natural gas itself. The current technology applied for the nitrogen removal which is the cryogenic distillation requires high capital and operating cost due to feed pretreatment and high energy usage for that extremely low temperature cryogenic process. Membrane technology is offering a better alternative with low operating cost and most importantly meets the product specification of 4 mole% nitrogen maximum in natural gas. The objectives of the project are to study the separation process of nitrogen from natural gas (in this case methane) using inorganic membrane, to perform experiment of gas membrane separation based on nitrogen and methane gas permeability and selectivity, and to investigate factors influencing the separation of nitrogen from methane. The experiments were conducted on individual gases (nitrogen and methane) and their binary mixture using inorganic membrane coupled with online analysis. The gas permeability and selectivity were determined to evaluate the separation efficiency. The effect of pressure and feed concentration were also investigated. The experimental results show that the separation process is possible as the membrane is able to remove about 5 mole% of nitrogen from the feed with the highest selectivity of 1.39. However, this selectivity is considered low and further research and experiment need to be made to enhance the separation efficiency and to get desired minimum selectivity of 3 to 5. The experiment also has proven that efficient separation occurs at low nitrogen feed concentration and the membrane separates gases less efficiently at higher pressure.