PulpMin

Mineral Characterisation of Particles in Processing Pulp

Scenery

Responsible person : S. Leroy

Supervisors : Pr. E. Pirard, G Dislaire

Sponsor : ULg

Context

Mineral processing relies heavily on the differential behavior of particles in pulps. In order to monitor hydrocyclones and flotation cells in, it is important to develop at line particle characterization providing information on particle size distribution and mineralogy.

Objectives

The capability of multi-spectral imaging to discriminate between minerals has been known for long. The development of low cost and extremely fast video
camera emphases the interest for this type of technology in the field of on-line control and monitoring. The objective of the project is to develop a vision device able to timely analyses mineral slurries for their particles size distribution and bulk mineralogy. The mineral identification will rely on the analysis of the spectral reflectance of individual particles dispersed within a flow cell. The device should be able to work at-line in harsh environment.

Equipment

A sampling device has been elaborated based on a flow cell linked to a high pressure pump. The setup allows for dispersion of the diluted mineral slurry into the cell. A simple multispectral imaging module has been designed to acquire images at different wavelengths. The design is based on a series of dichroic filters thereby avoiding moving parts and enabling a very fast acquisition of multispectral images. Multispectral classification is used to outline particles appearing in the field of view and to qualify their main mineral component.

Results

Primary tests consisted in the analysis of two reference materials with respectively pyrite and chalcopyrite as major constituent. Reflectance images are acquired at 6 different wavelengths, a registered transmitted image is also taken (backlighted image) to discriminate between opaque and translucent minerals. Images are processed to isolate particles.

The reflectance spectra are measured in the most reflective area of each particles. These values can further be used to calculate reflectance spectral ratio for each particles and determine the main mineral constituent for each particle.