• Membrane Selector

  Select a membrane you want to use for the calculation, from the list of available membranes.

• Mixture selector

  Select a mixture for the calculation from the list of available mixtures.

• Ideal/Non-Ideal switch

  As you may already know, Pervaporation is a tricky process, where feed mixture composition may drastically influence components’ permeance values. Here you can choose if the calculation will consider permeance independent of feed composition - Ideal option(applicable if permeances of considered components do not change a great deal over the considered concentration range ) or will be a function of feed concentration - Non-Ideal option. In both cases, the calculation will be performed with an account of the influence of process temperature. Both modelling modes require slightly different experimental data - For the Ideal mode, the Ideal experiments table should be specified - a table with permeances of both components of the mixture at different temperatures indicated for the Membrane. For the Non-Ideal mode, you should have a number of components permeances at different feed concentrations and temperatures in order for the algorithm to fit them with the equation - referred to as the Diffusion curve set.

• Modelling Parameters

  • Time Steps Number

    Indicate how many points you want to calculate for your model (the minimal value is 10).

  • Time Step, hours

    Set the time difference between each modelling step in hours

  • Precision

    The precision parameter is the difference in the permeate concentration after which the algorithm considers that the process parameters at a step were accurately calculated. The default value, which was established to be optimal for most calculations is around 5⋅10^-5. If you want your calculation to be less precise increase this number, on the other hand, if you want a more precise calculation you can lower that down to as low as 0.1⋅10^-5 (the influence of this parameter on the calculation results is discussed in detail here [1]).

  • Isothermal switch

    If the switch is turned on - the process is considered isothermal, so the feed mixture temperature will not change over the course of calculations. If the switch is off - the process will be considered adiabatic, and the algorithm will recalculate the feed mixture temperature at each modelling step based on the feed mixture evaporation heat, heat capacity and components’ fluxes.

• Initial Conditions

  • Membrane area

    The effective area of the membrane used for the pervaporation process.

  • Feed Temperature

    Initial temperature of the feed mixture - will not change over the course of the calculation if the Isothermal switch is on, and will be calculated if it is off.

  • Feed Amount

    When considering the time-dependent processes this is the initial amount of the feed mixture being separated. If you are trying to use the App to model the length-dependent process (such as ones inside the membrane module) you may indicate the mass flux of the feed mixture here, if you do so don’t forget to recalculate the modelled values to the dimensionless length of the module, and double check if such a trick is valid in your particular case (feed and retentate fluxes should not differ much).

  • 1^st Component Fraction

    Indicate the starting content of the first component of the mixture (if you are not sure which component is first - check the mixture card in the Materials library) in wt% or mol%.

• Permeate Parameters

  Here you can set either absolute pressure at the permeate side of your setup, or the temperature of the permeate condenser you use. If not set - the activity of penetrants in permeate will be considered - zero. Use the temperature setting only if the NRTL model is working fine at the chosen temperature, otherwise, you may end up with inaccurate results.

  • Pressure

    Absolute pressure that you see on the manometer at the permeate side of the membrane.

  • Temperature

    Temperature of permeate condensate (for example the coolant you use in your traps - if you are cooling with something below -20 ^oC consider leaving this field empty)

• Non-Ideal Settings

  • Diffusion Curve Set selector

    Select the diffusion curve set you want to use for the calculation. If you have sets measured at different starting feed concentrations consider choosing the one closest to the set initial feed concentration.

  • Initial Permeances

    If you use, let’s say a diffusion curve set measured for the membrane starting at 25% (1^st component) in the feed, and you know that permeances of the components will be significantly different at the same feed concentrations if you would have started from 50% (1^st component) in the feed - in these fields you may indicate the permeances of both components at 50% (1^st component, starting concentration) in the feed and the algorithm will try to take membrane swelling into account, cool, right? It actually works pretty well - consider reading a more detailed explanation of this approach in our article [1].

  • You can choose the units of the set permeances - the 3 supported units are: kg⋅m^-2⋅h^-1⋅kPa^-1, GPU and SI.

  • Permeance Function Parameters

    By default the algorithm will fit the Permeance equation in a way to fit the experimental points optimally, but if you want to override it, here you can specify n and m values for each component.

• Modelling Parameters

  • Feed Temperatures

    In the App, all the diffusion curves are considered isothermal, and here you may set the temperature of parameters calculation.

  • Initial Composition, 1^st

    Set the starting feed mixture composition by indicating the first component content in wt% or mol%(if you are not sure which component is first - check the mixture card in the Materials library).

  • Composition Steps Number

    Like the case of process modelling you can set the number of calculation steps (minimal value is 10).

  • Composition step, %

    The size of the first component composition step in wt% or mol%

• For the explanation of Ideal/Non-Ideal modes, Precision, Permeate Parameters and Non-Ideal modelling parameters block of calculation please consult the Pervaporation Process section.

We got your back if you want to fit your experimental pervaporation data with an equation. For these purposes, you may use the Permeance Fit section of the Modelling block. The algorithm will take a diffusion curve or a simple three-column (Download Sample Tables) .csv table and fit it by finding optimal n, m parameters and coefficients with the lowest Root Mean square deviation it can achieve. However, if you want to override the optimal n, m search you may indicate them in Equation Degrees. You may pick the units of the output permeance equation - the ones supported are - kg⋅m^-2⋅h^-1⋅kPa^-1, GPU and SI. If you are fitting permeance functions from a diffusion curve table you may also specify the component of interest.

Default Membranes

Default Mixtures

Default Components

The membranes in Pervaporation Modelling App are presented as a sum of their experimentally measured characteristics. There are two main types of data which can be used to describe a Membrane in the Pervaporation Modelling App - Ideal Experiments table and Diffusion Curve Sets. The Ideal Experiment table may be used to specify the permeances of individual components at different temperatures and could be used for the Ideal Modelling - a Membrane may only contain a single Ideal Experiments table. Along with the Ideal Experiments table, a Membrane may also contain a number of Diffusion Curve Sets - Diffusion Curve Set tables contain information on membrane performance when separating a real mixture at different temperatures and feed concentrations and are required to perform Non-Ideal Modelling. You can create a new membrane with one or both - an Ideal Experiments table or a number of Diffusion Curve Sets. If more than one DC set is specified for the membrane you can choose which to use when performing the calculations. You may download each table or a whole Membrane from its card accessible from the Materials library, downloaded membranes may be used with the PyVaporation package.

Mixtures in Pervaporation Modelling app are created from Components and a set of NRTL constants. For now, only NRTL model is supported for the calculation of the saturated vapour pressures of the components. You may calculate them directly from the Mixture card accessible from the Materials library if needed.

Components in Pervaporation modelling app are created using molecular mass, a set of vapour pressure constants for Antoine or Frost equation and a set of heat capacity constants for polynomial approximation of heat capacity dependence on Temperature. If you do not need the calculation of Evaporation/Condensation heat during Process Modelling you may set all the heat capacity constants to zero. You may calculate the Heat capacity, Evaporation heat and saturated vapour pressure of each component directly from the Component card accessible from the Materials library if needed.