(347i) Pressure Relief of Foaming Three Phase Systems

As part of safety concept, reactors and other high pressure containments have to be protected against excessive pressure by pressure relief devices such as burst discs or safety relief valves. Most design criteria and simulation tools have been developed for one and two phase systems. Hence to design foaming and non foaming three-phase systems experimental investigations on the unsteady level swell and of their discharge flow are still necessary. In order to gain a deeper knowledge under upset conditions, systematic studies were performed using a modified Adiabatic Pressure Dewar Calorimeter (ADCII). This project will finally lead to design criteria for an emergency relief system of reactive multiphase mixtures under various boundary conditions.

In this experimental set up pressure and temperature profiles as well as the total vented solid/liquid mass were measured. Non-stirred foaming systems consisting of two different surfactants with various concentrations in water and different solids were studied. Here the filling level, solid mass fraction, initial discharge pressure and vent size were kept constant. For each experiment the level swell was observed during the pressure relief through a camera. Moreover stirred foaming three-phase systems were investigated.

The pressure relief behavior of foaming three-phase systems is influenced by both surfactant and solid. Experimental results have shown that under the investigated conditions the pressure relief of foaming three-phase systems depends on surface tension, type and concentration of surfactant, particle diameter as well as the stirrer speed. Therefore they behave differently from two-phase systems.

Both measurements and simulations with existing level swell (e.g. DIERS Bubble Flow) and mass flow (e.g. Henry and Fauske) models in SAFIRE/Vent justify the necessity for further investigations of multi-phase systems. A phenomenological characterization of the solid discharge and of the pressure profiles lead to a new model, which is based on the adhesive force and of the flotation theories.