PhD Project: SAM-FLASH

SAfe relief of Multi-Component FLASHing Two-Phase-Flow

Investigations in the field of multi-component flashing flow have started at the CSE Center of Safety Excellence. The investigations deal with the phenomena arising during the critical flow of multi-component multi-phase mixtures through industrial fittings.

The applications are many: vessels, fittings and equipment of many production processes in the chemical and petrochemical industry as well as in the oil and gas industry are based on mixtures of components and multi-phase streams. The critical flow rate of multi-component multi-phase flow can be encountered during the discharge through safety relief valves and rupture discs of pressurized equipment, at leaks and ruptures of pipelines and reactors as well as during the flow through control valves and orifices.

The core aim of the project is to investigate the recurring thermodynamic and mechanical non-equilibrium phenomena i.e boiling delay and phase-slip, in flashing multicomponent mixtures through nozzles under critical flow conditions, which have direct relevance for industry throttling devices applications. Besides, for multi-component mixtures, the chemical non-equilibrium plays an important role and its contribution to the critical mass flow rate needs to be determined.

These phenomena in multi-component systems has not yet been investigated. Due to the lack of knowledge in these applications, safety devices are currently being oversized. The bigger, the better is not the solution in safety. Oversized safety device-vent line systems involve not only economic disadvantages but the optimal protection of the system is also exposed to even larger risks due to malfunctioning of downstream retention systems.

The basis of the SAM-Flash project has been presented and discussed in the DECHEMA Working Party “Safe Design of Chemical Plants” at the end of 2017. The first publication “Modelling of critical mass flow rates through safety valves in case of non-equilibrium multi-component flashing mixtures” will be presented at the international Conference on Modelling Fluid Flow (CMFF’18) in Budapest this year.

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