In order to address safety issues and flow assurance in CO2 rich processes, modelling and prediction of the formation of solid CO2 is important. With support from Total, Equinor, Gassco and CLIMIT, Petrell is developing a simulation tool capable of predicting solid CO2 in pure CO2 fluids as well as in mixtures. The development includes a new thermodynamic module, and treatment of solids as an integral part of the heat transfer and flow modelling. Preliminary showcases demonstrate depressurization and blowout scenarios where the two and three phase behavior with solid CO2 is essential.