High Pressure Supercritical Carbon Dioxide Separation from its Mixture with Nitrogen at Different Temperatures

Abstract

Carbon dioxide (CO2) capturing from point sources is currently being proposed as a way to minimize CO2 emissions to the atmosphere. Carbon dioxide is considered one of the greenhouse gases that affects our environment. Legislations are being enforced in many countries to limit CO2 emissions to the atmosphere. Two methods are mostly used for CO2 capturing from flue gases and natural gases; the first method is absorption using amine-based solvents, while the second is membrane separation. The first method is effective for CO2 separation from gas mixtures with low CO2 concentration in the range of 10 to 20%, while the other can handle gas mixture with intermediate CO2 concentration but there is a limit on the CO2 purity. Hence, such methods cannot be used in pre-combustion and oxy fuel technologies where a more concentrated CO2 gas stream is produced. Throughout this work, a new method is introduced to separate carbon dioxide from its mixture with nitrogen (N2) at high concentrations, 90 mol.% CO2 and 10 mol.% N2 gas mixture. A customized high-pressure experimental set-up was built. Three temperature were tested: 15 °C, 25 °C and 38 °C at 150 bar. At such condition CO2 will be in the liquid and the supercritical phase respectively. The composition of the top and bottom streams where analyzed. The amount of CO2 in the top stream was the smallest at the supercritical condition. In addition, the purity of CO2 in the bottom stream was the highest at 38 °C and 150 bars, when CO2 is at the supercritical phase.