Enhanced Holland-Batt spline for describing spiral concentrator performance

• An enhanced triple spline is proposed to describe the recovery-yield relationship.
• Low density fractions are also described with triple splines.
• An automated procedure is presented for fitting triple splines to test work data.
• The proposed method can be used for effective assessment of spiral separation performance.

The Holland-Batt spline is well known when it comes to plotting spiral separation performance. The spline, which consists of a linear curve and power curve, has been successfully used to fit test work data that is presented as cumulative recovery of a valuable mineral versus the cumulative mass yield to valuable mineral concentrate. The benefit of this curve fitting process is that it produces a mathematical expression that is essential for simple mass flow modelling calculations. Although the mathematics is simple, the fitting process can be quite cumbersome. This work enhances the Holland-Batt spline with a few adjustments to improve the fit accuracy and ease the fitting process through (1) smoothing the transition zone between the linear and power law curves, (2) applying the principles to both low and high density particles, (3) use Visual Basic user-defined functions to simplify test work sheets in Excel and (4) use Excel Solver to automate the curve fitting process. These steps are applied to an example test work data set to clearly demonstrate the approach. The enhanced method is easy and simple to apply to spiral concentrator mass flow modelling.