Development and evaluation of a dense media cyclone for the Southern African mineral and coal industries
Date
2014-02-25
Authors
Singleton, J. D.
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
Dense media separation (DMS) plays an integral part in coal processing as well as in the upgrade
of low grade ore bodies prior to further processing like flotation and leaching. Various
separating vessels are used in DMS; of which the dense media (DM) cyclone is the most
common. However, the limited materials of construction available for DM cyclones leave the
industry with little choice. In addition, the DM cyclones available moved away from the basic
principles of classification hydrocyclones which is to reduce the turbulence in the feed chamber
in order to achieve improved efficiency. The ceramic tiled DM cyclones available in the market
have ceramic tiles installed perpendicular to each other in the feed chamber, which increase the
turbulence in the feed chamber at the expense of longer equipment life. For that reason, a
research project was initiated to establish the current installed base of DM cyclones in Southern
Africa and to develop and evaluate a DM cyclone with a laminar spiral feed chamber design to
reduce the turbulence when feeding the cyclone, whilst achieving the same or superior wear
properties.
Because Cavex is well proven in hard rock mining and coal classification, it was used as basis for the development of a DM cyclone. Individual moulds were developed and produced in order
to fabricate a Cavex DM cyclone with the exact laminar spiral feed chamber that exists when
moulded out of rubber. Afterwards, the Cavex ceramic tiled (CVXT) cyclone was manufactured,
installed and commissioned. Using the basic operating principles of hydrocyclones, the
predicted results were achieved. The 650CVXT results confirmed that a DM cyclone and a
classification cyclone are inherently the same piece of equipment; it is the selection criteria and
material of construction that differ. There is a definite benefit in focussing on metallurgical
efficiency in conjunction with wear properties, rather than equipment life (wear life) as the only
parameter during equipment fabrication. A simple way to achieve improved performance is to reduce the turbulence in the feed chamber. Further work must include the evaluation of the Cavex CVXT DM cyclone in near gravity coal
circuits and to investigate whether the same lower operating pressures (6D compared to
conventional 9D) will result in improved coal yield, as was illustrated successfully in the
separation of fluorspar by DMS, whilst achieving the desired ash contents. The work must
include detailed studies on the effect of feed pressure vs. yield/recovery, when the turbulence the feed chamber is reduced. Overall energy savings should be quantified by reducing the cyclone feed pressure.