Effect of a mixture of carbon dioxide and steam on ejector performance: An experimental parametric investigation

The results are presented for an experimental investigation characterizing the performance of a steam ejector when the secondary fluid is a mixture of steam and a non-condensable gas. In the context of post-combustion carbon capture, carbon dioxide was chosen as the non-condensable for this work. In order to study the pure steam ejector over a wide operating range, performance curves were prepared for primary pressures of 350, 450 and 550 kPa, with secondary pressures of 50, 70 and 90 kPa. Effects of the primary nozzle position, the primary pressure, the secondary pressure, and the nozzle diameter were evaluated. For a reference primary pressure of 450 kPa and secondary pressure of 70 kPa, performance curves were prepared for four levels of entrained CO2 in the secondary fluid mixture, up to 45% by mass, and for four nozzle throat diameters ranging from 4.03 to 5.09 mm. It was observed for the first time that in contrast with the pure steam ejector performance curves, increasing amounts of entrained CO2 improved the critical entrainment ratio, but the critical pressure remained unchanged. This behaviour was in sharp contrast with that of a pure steam ejector. A linear relationship was observed between the increase in the entrainment ratio of a steam ejector and the mass fraction of CO2 contained in the ejector secondary fluid.