Specific Surface Area (SSA)

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Contents 1 General Description 2 Configuring SSA Data 3 SSA Calculations 4 Hints and Comments

General Description

The Specific Surface Area (SSA) is used in the Precipitation Model, a continuous stirred tank reactor with Gibbsite crystallisation precipitation that is used in the Alumina industry. The SSA data is described as follows:

The SAL - (Seed Surface Area Volume (m²/L) is a required variable in the Precipitation Model using the Yield Calculation method. It can be derived from SAM - (Seed Surface Area Mass (m²/g) or D - (seed particle size (mm), which is normally derived value. However, the user may set the initial value of SAM or D entering the first precipitator to obtain the correct SAL, thus a correct yield in the precipitator.

Configuring SSA Data

In SysCAD 9.0 and later the SSA fields are only available if the user carries out the following steps:

1. Edit the configuration file, and switch on the SizeDst1.dll -- SpecificSurfaceArea option.
   
   
2. Reload the project with the edited configuration file.
3. Ensure that the relevant FEEDER or PIPE is using a Bayer Species Model, (See Generic Bayer Species Model or Alumina 3 Bayer Species Model).
4. On the Feeder|Content OR Pipe|Qi/Qo tab pages, select SzSSAAct and choose create to turn on the Specific surface area option. SSA data will then be displayed on the SSA or Qm tab pages as shown.
   
   
5. Under the section "SSA" located on the Content or Qi tab page the user can enter the appropriate values for either SAM or D (Use the 'SetDiam' tickbox to toggle between these two options).

In SysCAD 8.2 the user will find the following fields in either Feeder|Content or Pipe|Qi/Qo tab pages:

SSA Calculations

The equations used in calculating SAL are:

1. SAL = #/L * Pi * D * D
2. #/L = 6.0 * 0.001 * Solids_Mass_Flow / (Pi * Solids_Density * D * D * D * Liquid_Volumetric_Flow)
3. D = 3.0 / (500.0 * Solids_Density * SAM))
4. #/s = 6.0 * Solids_Mass_Flow / (Pi * Solids_Density * D* D* D)
5. SAM = 3 / (500 * Solids_Density * CalcD)
6. CalcD = Pow(6 * Solids_Mass_Flow / (pi * Solids_Density * #/s), 1/3)

If the user ticked the SetData box and input value for SAM, SysCAD will use it to calculate the remaining variables; likewise, if the user input value for PartDiam (D), SysCAD will derive SAM using equation 3 and then calculate the remaining variables.

Hints and Comments

1. The setting of SAM is only for initialisation purposes; therefore it is usually set at the stream entering the first Precipitation Model, whether it is a fresh feed or a recycle stream.
2. Once the SetSAM method is used, the particle size information will be shown in all downstream pipes.
3. It is IMPORTANT to note that solid selected MUST be present in the stream (thus has a value) for the above to work properly.