Scale-Up of Decanter Centrifuges for the Particle Separation and Mechanical Dewatering in the Minerals Processing Industry by Means of a Numerical Process Model

Abstract

Decanter centrifuges are frequently used for thickening, dewatering, classification, or degritting in the mining industry and various other sectors. Their use in an industrial process chain requires a sufficiently accurate prediction of the product and the machine behaviour. For this purpose, experiments on a smaller pilot-scale are carried out for scale-up of a decanter centrifuge, which is usually a major challenge. Predicting the process behaviour of decanter centrifuges from laboratory tests is rather difficult. Basically, there are two common ways of scale-up: First, via analytical methods and the law of similarity, which often requires an enormous experimental effort. Second, using numerical models, which demands a mathematically and physically precise description of the multiple processes running simultaneously in such machines. This article provides an overview of both methods for scale-up of a decanter centrifuge. The concept of a previous developed numerical approach is introduced. Pros and cons of both scale-up methods are compared and further discussed. Experiments on lab-scale, pilot-scale, and industrial-scale decanter centrifuges with two different finely dispersed calcium carbonate water suspensions were carried out and simulations were done to investigate and prove the scale-up capability and transferability of the numerical approach.

Grey Box Modelling of Decanter Centrifuges by Coupling a Numerical Process Model with a Neural Network

“…For both pool depths, the white box model follows the general trend that the solids mass fraction decreases with increasing rotational speed and the two white box models are basically equivalent, as the white box model is not sensitive enough to this difference in the pool depth. A more detailed discussion has been provided in previous publications with validation tests [12,14]. The experimental results reveal that for the same rotational speed, the solids mass fraction is higher at the smaller pool depth.…”

“…However, correction does not mean that the simulation results are unreliable and have to be corrected in all cases. In previous works [12][13][14] it was demonstrated that the method is indeed valid. Here, an enhancement must be created to consider effects that have not been modelled or to cover cases where no physical equations are known.…”

“…However, the details about the essential principles of operation and the influence of specific process variables of a counter-current decanter centrifuge are necessary for a sufficient understanding of the present model. Furthermore, the experimental procedure is similiar to the procedure in Menesklou et al [14], where it is dicussed in detail.…”

“…A deeper pool, i.e., greater pool depth, generally leads to a better separation result. However, the changing flow characteristics become more important; they are not covered by the simulation tool used so far [12,14]. Depending on the volumetric flow rate and pool depth, the flow through the pool is through the complete pool or only partially and the formation of dead zones may occur.…”

“…This mechanistic approach considers settling behaviour, sediment consolidation and sediment transport. Additionally, the authors have validated the model with experiments using different calcium carbonate water slurries and decanter centrifuges from lab-to industrial-scale [14]. In some applications, for example at relatively deep pool depths, local turbulence and flows in some areas of the centrifuge can influence the separation result.…”