Optimizing phase equilibrium predictions for the liquefaction of supercritical water gasification products: Enhancing energy storage solutions through advanced thermodynamic modeling

Supercritical water gasification products typically consist of a vapor mixture consisting of H2 and CO2 with high pressure. Liquefaction of supercritical water gasification products not only allows the vapor mixture to be reduced in volume for easy transportation, but also allows liquid CO2 to be obtained from it, and also serves as a form of energy storage. Under the existing thermodynamic model, the prediction of the liquefaction dew point under high pressure is easily diverged and the accuracy is not enough. In this paper, we obtain the value of CO2+H2 binary interaction coefficient under high pressure kij=0.146 by the fitting method and, which improves the convergence of the predicted phase equilibrium data at high pressure and obtains the results with higher accuracy. In the prediction of dew point of supercritical water gasification products, the fluctuation of H2 content has little effect on the liquefaction pressure, and more significant is the effect of the liquefaction temperature, and it is more economical to carry out the liquefaction work within the range of −30 °C to −5 °C. At the same time, in the liquefaction products lower than −10 °C, the liquid CO2 with the mole fraction of more than 0.9 can be obtained.