The proposed project will understand the fundamentals governing the flow and thermo-physical phenomena within a supersonic separator for CO2 removal from natural gas, culminating in a mathematical model capable of predicting the condensation and separation flows. This newly developed CFD technique will play a key role in achieving this objective. Incorporation of nucleation process, droplet growth and heat transfer into such a model will allow the prediction of the thermal history of gas/liquid in a supersonic separator. Developments in this direction will produce a mathematical model to establish a comprehensive understanding of the phenomena involved at a molecular scale. The resulting information, in terms of constitutive equations or other suitable forms (e.g. gas properties description with real gas model), can be incorporated into a continuum-based computer model for process engineering application.
We have developed a computational fluid dynamics (CFD) model to predict the CO2 condensing flow in a supersonic nozzle. Adding two transport equations to describe the liquid fraction and droplet number, the detailed numerical model can describe the heat and mass transfer characteristics during the CO2 phase change process under the supersonic expansion conditions. A comparative study is performed to evaluate the effect of CO2 condensation using the condensation model and dry gas assumption. The results show that the developed CFD model predicts accurately the distribution of the static temperature contrary to the dry gas assumption. Furthermore, the condensing flow model predicts a CO2 liquid fraction up to 18.6% of the total mass, which leads to the release of the latent heat to the vapour phase. The investigation performed in this study suggests that the CO2 condensation in supersonic flows provides an efficient and eco-friendly way to mitigate the CO2 emissions to the environment.
