Coal Preparation » Gravity Separation
A Computational fluid dynamics (CFD) model of the spiral has been under development by the Centre for Advanced Numerical Computation in Engineering and Science (CANCES), at the University of New South Wales, since 1992. The objective of this part of the ACARP project was to generate the detailed measurement needed to validate the modelling of a specific coal spiral, the Mineral Technologies LD9. Despite being a superseded model, this spiral was chosen as a large body of experimental data was already in existence, and an LD9 was available at the JKMRC for the experimental work.
This volume describes the experimental work carried out which has succeeded in providing detailed primary and secondary velocity data on the LD9 spiral at feed rates of 4, 6 and 8 m3 h-1. The velocity data covers the full depth of the flow, as well as the free surface, and is the most comprehensive yet available anywhere. Video-based Particle Image Velocimetry (PIV) was used to measure fluid velocities within the flow, and non-wettable lycopodium powder and high speed photography to measure the free surface velocity.
The data are compared with the most recent CFD model developed at CANCES using the commercial software package Fluent (v4). Unlike all other spiral models to date, only trough geometry and feed flow rates are required as model inputs. The comparison show an excellent measure of agreement between the experimental and computed results in terms of fluid primary velocity, secondary velocity and depth profile.
The purpose of this volume is to provide coal preparation plant designers and operators with a concise source of practical information about coal spirals drawn from this and other recent research projects and associate site investigations. It is organised into 5 sections:
Section 1 provides a brief history of the introduction of the spiral for coal preparation applications.
Section 2 summarises the operational aspects of spirals based on JKMRC experience, and the experience of many spiral plant users.
Section 3 describes briefly how the performance of a coal spiral can be determined.
Section 4 summarises briefly the current state of the art in spiral modelling.
Section 5 presents a series of appendices;
- Appendix 5.1 describes the construction of spiral loading curves.
- Appendix 5.2 covers the fitting of smooth partition curves to raw data using Solver in EXCEL.
- Appendix 5.3 describes how simple modelling using partition curves can be used to investigate minor changes in operating conditions.
- Appendix 5.4 tabulates the coal spirals currently offered by Australian manufacturers and distributors.
- Appendix 5.5 provides a comprehensive bibliography of papers, theses and books that deal with spirals in all areas of mineral and coal processing.