Improved modelling of mixtures

The Phast and Safeti Multi Component (MC) extension provides improved consequence and risk results for mixtures compared with the traditional “pseudo-component” (PC) approach. 

In the “pseudo-component” approach the composition, thermodynamic behaviour and properties of a mixture are calculated using simple averaging equations, whereas in the multi component approach modelling of mixtures involves more rigorous enhancements to the physical property system. 

The Multi Component extension supports the core steady-state discharge models, dispersion modelling via the unified dispersion model (UDM), and the standalone multi component pool vapourisation modelling.

More accurate modelling of phase equilibrium

For a pure component, the bubble point and the dew point are the same temperature; there is no region in which the material is two-phase across a range of temperatures.  

The pseudo-component approach treats mixtures as pure components and does not model the two-phase region. On the other hand, the multi component approach models the phase equilibrium in a more rigorous manner, and both phases will be modelled when the conditions are in the two-phase region. 

The composition in the liquid and in the vapour phase differ when a mixture is under two-phase conditions and, as conditions change, the equilibrium and composition in each phase will change. This behaviour is modelled in the multi component approach.

Phast and Safeti Multi component extension -  phase equilibrium
An illustration of phase equilibrium

Key capabilities of the Multi Component extension

  • Integrated multi component property system with built-in chemical database and flash calculator.
  • Improved source term modelling of two-phase mixtures for models including catastrophic rupture, leak, line rupture, relief valve and disc rupture.
  • Calculate vapourization rates of multiple components for a mixture vapourising from a pool (using the standalone multi component pool vapourisation model).
  • Supports most frequently used equations of state including Redlich-Kwong, Soave-Redlich-Kwong and Peng-Robinson.
The results using the extension include mixture composition as release expands from storage to atmospheric conditions, as well as graphs of phase composition during dispersion.

Phast and Safeti Multi component extension key capabilities
Graph of pool vapourisation rates over time of multiple components for a mixture

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from 45 EUR per day

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Pricing and licensing

Individual

Plans are available for local installation on your PC or pre-installed virtual machine. Access is available from 1 day to 1 year for one single user.

This is an extension module and requires a valid version of Phast or Safeti.

 


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from 45 EUR per day

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from 610 EUR per month

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Network (Concurrent)

Recommended when there is need for multiple users at the same time.

Access for multiple simultaneous users where the product license is installed on a network server and software installation on the individual user's machine.

This is an extension module and requires a valid version of Phast or Safeti.

 


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from 610 EUR per month

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Frequently asked questions

Is there a case where the pseudo-component is more suitable than the multi-component modelling approach?

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The pseudo-component (PC) approach is good for pure components, non-polar, low volatility range mixtures at low pressures, while the multi-component (MC) approach is good for pure components, wide volatility range mixtures, mixtures at all pressures, non-polar or slightly polar mixtures.

Could you explain the different between MC single aerosol and MC multiple aerosol?

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For the single aerosol method, all the aerosol droplets are assumed to have the same composition and multi-component phase equilibrium calculations are used to model the behaviour of the aerosol. For the multiple aerosol method, a range of aerosols with different compositions are modelled, where each aerosol contains all components that have the same setting for the aerosol class number, and multi-component phase equilibrium calculations are used to model the behaviour of each aerosol.

Where can I choose between pseudo-component and multi-component model within the software?

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The choice between pseudo and multi-component model will be available within the Software if you have a valid multi-component licence. It is located in the edit dialog window after double-clicking the equipment level, in the Material tab, under the heading of “Modelling of mixtures”.

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