Raimondi L., 2016, Simulation of Pipeline Depressurization in the Transportation of Oil&Gas with High CO2 and H2S Content, Chemical Engineering Transactions, 53, 337-342.
The problem of a reliable simulation of relief condition of a fluid (flow rate, pressure and temperature) is a preliminary and fundamental step to the calculation of dispersion effects. The evaluation of the mass discharged from pipelines in cases of leaks or abnormal operating conditions is largely based on the use of commercial simulators for safety analysis like PHAST or more specialized codes developed for oil&gas transportation such as OLGA and Ledaflow. However all these codes use a simplified thermodynamic approach since physical and transport properties are calculated on the basis of fixed fluid compositions and stored in tables. To avoid these limitations vapour-liquid equilibrium and fluid dynamics equations should be coupled and solved at the same time. This paper presents the implementation of two-fluid model fluid dynamics equations in a process simulator (XPSIM) providing an integrated tool which allows the simulation of vapour-liquid flows taking into account also the changes in the chemical composition. Since in this field experimental data are almost not available the validation of simulations is very difficult and different results are to be expected with different codes. The first case considered is the fast discharge of a rich CO2 mixture obtained in a small experimental flow-loop: the simulated results are described and compared with experimental values. The second case presents the results of the depressurization of a pipeline used to transport a hydrocarbon fluid with high hydrogen sulfide content in the case of an emergency through a control valve.
