Mass Balancing (n-Product Formula): Difference between revisions

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== Model theory ==
== Model theory ==


{{Restricted content}}
<hide>
The ''method of mass flow errors'' is applied to estimate the solids split and recovery of multiple assayed components to an arbitrary number of product streams.{{Greet (2010)}}
The ''method of mass flow errors'' is applied to estimate the solids split and recovery of multiple assayed components to an arbitrary number of product streams.{{Greet (2010)}}


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:<math>R_{ij} = \dfrac{\beta_j p_{ij}}{\hat{f}_i}</math>
:<math>R_{ij} = \dfrac{\beta_j p_{ij}}{\hat{f}_i}</math>
The assays of a single component which are larger than other components (even by choice of units) will tend to dominate the unweighted estimates, for obvious reasons.


=== Weighted estimates ===
=== Weighted estimates ===
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where:
where:
* <math>\sigma_{{\rm f}i}</math> is the standard deviation of the assay of component <math>i</math> in the feed stream
* <math>\sigma_{{\rm f}i}</math> is the absolute standard deviation of the assay of component <math>i</math> in the feed stream
* <math>\sigma_{ij}</math> is the standard deviation of the assay of component <math>i</math> in product stream <math>j</math>
* <math>\sigma_{ij}</math> is the absolute standard deviation of the assay of component <math>i</math> in product stream <math>j</math>


The weighted solids splits is therefore found from:
The weighted solids splits is therefore found from:
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# As number of randomised draws increases, the mean values and variances of the mass splits and recoveries will approach their true values.
# As number of randomised draws increases, the mean values and variances of the mass splits and recoveries will approach their true values.
-->
-->
=== Additional notes ===
==== Absolute and relative standard deviations ====
The assay standard deviations required for the weighted estimates, (<math>\sigma_{\rm f},\sigma_{ij}</math>), are ''absolute'' standard deviations, and posses the same units as the assay measurement.
However, many other literature sources quote ''relative'' standard deviations, usually as percentages, which must be converted to absolute values. For example:
:<math>\sigma_{\rm fi} = \mathrm{RSD}_{\rm fi} . f_i </math>
for the feed stream assays, where <math>\mathrm{RSD}</math> is the Relative Standard Deviation (frac).
Care must be taken to differentiate between absolute and relative values when applying error models, e.g. the Whiten approach for particle size distributions.{{Greet (2010)}}{{Napier-Munn et al. (1996)}}
==== Component assay magnitude ====
Component assays with larger values will tend to dominate the results of the method of mass flow errors. For example, component assays with values of thousands of parts per million will affect the solids mass split more than components with value of a fraction of a weight percent.
This can be addressed as follows:
* For the unweighted estimates case, the measured assay values can be scaled to more appropriate units, e.g. 100g/t rather than g/t.
* For the weighted estimates case, the absolute standard deviations can be scaled to produce the same effect.
The scaling factors applied in either case are arbitrary, and should be selected to reflect the relative "importance" or "confidence" of the component measurement.
</hide>


== Excel ==
== Excel ==
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The n-product formula may be invoked from the Excel formula bar with the following function call:
The n-product formula may be invoked from the Excel formula bar with the following function call:


<syntaxhighlight lang="vb">=mdMassBal_nProductFormula(Assays as Range, Optional AbsSD as Range)</syntaxhighlight>
<syntaxhighlight lang="vb">=mdMassBal_nProductFormula(Assays as Range, Optional AbsSD as Range, Optional Transposed as Boolean = False)</syntaxhighlight>


{{Excel (Text, Help, No Arguments)}}
{{Excel (Text, Help, No Arguments)}}


The input parameters and calculation results are defined below in matrix notation, along with an example image showing the selection of the same cells and arrays in the Excel interface:
The input parameters and calculation results are defined below in matrix notation, along with example images showing the selection of the same cells and arrays in the Excel interface.
 
=== Default ===
 
The following default arrangement of inputs and results ranges apply when the formula argument ''Transposed'' is '''false''' or omitted:


{|  
{|  
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|  
|  
::[[File:NProductFormula3.png|frame|Figure 1. Example showing the selection of the '''Assay''' (blue frame), '''AbsSD''' (red frame), and '''Results''' (light blue frame) arrays in Excel.]]
::[[File:NProductFormula3.png|frame|Figure 1. Example showing the selection of the '''Assay''' (blue frame), '''AbsSD''' (red frame), and '''Results''' (light blue frame) arrays in Excel.]]
|}
=== Transposed ===
The following arrangement of inputs and results ranges apply when the formula argument ''Transposed'' is '''true''':
{|
|- style="vertical-align:top;"
|
{|
  |- style="vertical-align:top;"
  |
:<math>
  \begin{align}
  \mathit{Assay} & =
\begin{bmatrix}
f_1 & p_{11} & \cdots & p_{1n}\\
\vdots & \vdots & \ddots\\
f_m & p_{1m} & \cdots & p_{mn}\\
\end{bmatrix}\\
\\
  \mathit{AbsSD} & =
\begin{bmatrix}
\sigma_{{\rm f} 1} & \sigma_{11} & \cdots & \sigma_{1n}\\
\vdots & \vdots & \ddots\\
\sigma_{{\rm f} m} & \sigma_{1m} & \cdots & \sigma_{mn}\\
\end{bmatrix}\\
  \end{align}</math>
  |
::<math>
\begin{align}
  \mathit{mdMassBal\_nProductFormula}  & = 
\begin{bmatrix}
\beta_{\rm f}\text{ (frac)} & \beta_1\text{ (frac)} & \cdots & \beta_n\text{ (frac)}\\
\hat{f}_1\text{ (frac)} & R_{11}\text{ (frac)} & \cdots & R_{1n}\text{ (frac)}\\
\vdots & \vdots & \ddots & \vdots\\
\hat{f}_m\text{ (frac)} & R_{m1}\text{ (frac)} & \cdots & R_{mn}\text{ (frac)}\\
\end{bmatrix}
\end{align}
</math>
  |-  style="vertical-align:top;"
  |colspan="2"|
  |}
|
::[[File:NProductFormula4.png|frame|Figure 2. Example showing the selection of the '''Assay''' (blue frame), '''AbsSD''' (red frame), and '''Results''' (light blue frame) arrays in Excel when <math>\mathit{Transposed} = \mathrm{True}</math>.]]
|}
|}



Latest revision as of 11:39, 4 December 2024

Description

This article describes a methodology for estimating the solids mass split and recovery of multiple assayed components from a process step with any number of product streams.

Model theory

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Excel

The n-product formula may be invoked from the Excel formula bar with the following function call:

=mdMassBal_nProductFormula(Assays as Range, Optional AbsSD as Range, Optional Transposed as Boolean = False)

Invoking the function with no arguments will print Help text associated with the model, including a link to this page.

The input parameters and calculation results are defined below in matrix notation, along with example images showing the selection of the same cells and arrays in the Excel interface.

Default

The following default arrangement of inputs and results ranges apply when the formula argument Transposed is false or omitted:

where:

  • is total mass fraction of solids in the feed (frac), i.e.
  • the unweighted sum of squares approach is used if is omitted.
Figure 1. Example showing the selection of the Assay (blue frame), AbsSD (red frame), and Results (light blue frame) arrays in Excel.

Transposed

The following arrangement of inputs and results ranges apply when the formula argument Transposed is true:

Figure 2. Example showing the selection of the Assay (blue frame), AbsSD (red frame), and Results (light blue frame) arrays in Excel when .

See also

References