Coal Preparation » Process Control
This project was designed to build on project C6043, which developed a prototype on-line image analysis instrument to measure coal flotation frothparameters on Microcels at Peak Downs CPP.
The project had four objectives:
- To determine the most effective means of using the image analysis instrument to control a bank of mechanical cells.
- To determine how to carry out froth imaging on Jameson cells where wash water trays may obscure the surface of the froth.
- To determine the extent to which the soft-sensor needs parameter updating to maintain acceptable accuracy in prediction of % ash and % solids.
- To test the applicability of low-cost time-of-flight lasers for characterising flotation froth.
Site-based test work was conducted on the Jameson cells at Goonyella CPP, and Outokumpu mechanicals cells at Port Kembla CPP. The test work at Goonyella also involved personnel from Jenkins-Kwan Technology who carried out laser and spectroscopic work as part of meeting objective three.
Difficulties with linking the image analysis system to the plant DCS at Port Kembla limited the achievement of objective one. However work conducted elsewhere by the JKMRC has shown that banks of cells can be effectively controlled by image analysis of only those cells immediately after reagent addition points.
It was established at Goonyella that the only effective means of froth imaging Jameson cells is to make a small cut out in the wash water tray and view the froth from directly above the cells. This causes only minor changes in local froth texture.
Examination of sample data from Goonyella suggests that the soft sensor is unsatisfactory if its parameters are not updated every shift, and preferably more frequently. Limited spectroscopic examination of concentrate samples using ultra-violet (UV), visual (VIS) and near-infra-red (NIR) spectra using CCD spectrometer detectors was inconclusive. Higher reflectances corresponded to higher ash values.
A laser was tested in scanning and spot mode to measure reflectance and froth profiles on-line. It may be possible to correlate reflectance with ash content. The time-of-flight laser was used to demonstrate froth eruptions, which may be of operational use in Jameson cell monitoring.