Cryogenic Purification of Natural Gas under High Pressure Using Hybrid Multiple Bed Network

Natural gas processing is classified as one of the sophisticated industrial process designed to purify raw natural gas by separating various hydrocarbons and impurities from the wellhead gas to produce a ‘pipeline quality’ dry natural gas. The development of an energy efficient separation process starts to be domineering due to the presence of high CO2 contents in Malaysian raw natural gas. The present study investigates the optimal conditions for the hybrid multiple cryogenic packed beds network which separates water, carbon dioxide and heavy hydrocarbons from high pressure natural gas. A detailed simulation on 70% CO2 natural gas feed was carried out according to engineering parameters like bed temperature, bed pressure, feed composition, hydrocarbon losses and energy requirements. The separation process is carried out in a flash drum and the respective phase product stream is channeled through pipelines according to difference in desublimation point. Therefore, physical separation is seen as the main involvement in this purification process. Prior to proceeding further with depth first search iterations, the importance of optimization in separation is carried out through comparative study of the hybrid multiple packed bed network before and after optimization. Optimal temperature of each node is obtained upon completion of pressure sensitivity analysis using the single node objective function. In present study the optimal temperature and pressure conditions for natural gas processing are explored by performing optimization on each node using Golden Section Search algorithm. The iterations for each hybrid multiple packed beds are continued till the recovery of methane and reduction in hydrocarbon loss were achieved. For natural gas feed with 70% carbon dioxide, hybrid multiple cryogenic packed beds network with the combinations of optimal pressure and temperature is able to remove 99.92% of CO2 and produce methane gas with 86% purity. Comparative study on the compositions of hydrocarbon, and methane from each iteration is analyzed to deduce the effect of operating parameters on hydrocarbon losses in cryogenic separation.