Author(s)

M.N. KAJAMA, N.C. NWOGU & E. GOBINA

Abstract

Natural gas processes accounts for about 5.3 billion tonnes per year of carbon dioxide (CO₂) emission to the atmosphere. At this rate of emission, the expectation will drastically rise if not curtailed. In order to achieve this, a cost-effective and environmental friendly technology is required. In recent times, membrane technology has been widely applied for CO₂  removal from raw natural gas components. This article examines CO₂ separation from natural gas, mainly methane (CH₄), through a mesoporous composite membrane. A laboratory scale tubular silica membrane with a permeable length of 348 mm, I.D and O.D of 7 and 10 mm, respectively, was used in this experiment. Scanning electron microscopy (SEM) was used to analyze the morphology of the membrane. Single gas permeation of helium (He), CH₄, nitrogen (N₂), argon (Ar) and CO₂  were determined at permeation temperature range between 25 and 100°C and feed gauge pressure of 0.05 to 5.0 barg. Before silica modification, He recorded the highest flow rate (0.3745 l/min) while CO₂ recorded the least flow rate (0.1351 l/min) at 0.4 barg and 25°C. After silica modification, CO₂ flow enhances significantly (3.1180 l/min at 1.0 barg) compared to CH₄  (2.1200 l/min at the same gauge pressure) due to the influence of surface flow mechanism. Temperature variation described the applicability of Knudsen diffusion for He. A combination of viscous, surface and Knudsen diffusion transport mechanisms were obtained throughout the experiment. Membrane thickness was also calculated to be 2.5 × 10⁻⁴ m.

Keywords

Carbon dioxide removal, dip-coating, gas permeation, nanoporous ceramic membranes, natural gas separation, permeation temperature, surface flow