PARTICLE SHAPE ANALYSIS IN MINERAL LIBERATION

One of the main reasons for size reduction is to liberate minerals for recovery, but simple measurements of size reduction alone are not enough to determine the fraction liberated. Additional measurements such as specific gravity and linear intercept distributions are necessary. Since linear intercept distributions have been transformed into volumetric abundances with reasonable success, it was hypothesized that mineral perimeter distributions could also be transformed into volumetric abundances. The problem is to detect the perimeter of different minerals without expensive microprobes or image analyzers. The solution is to use Fourier descriptors of particle silhouettes.; A newly developed method for particle shape analysis, called elliptic shape decomposition, was tested against the most widely used one, namely, the R-(theta), and it was found that the former is better than any thing the R-(theta) can come up with. The elliptic shape method was further tested on gold particles from different geographic locations at Moose Range Drainage, Alaska. An average classification accuracy of 96 percent was obtained.; Computer-generated Type 1 random particles were used to generate hypothetical liberated particles. The results encouraged the construction of real particles. A micron eye digital camera attached to an IBM PC was used to digitize the fractionated mineral grade particles for each of the four performed ball mill grinding tests. Statistical analysis performed on liberated particles indicated that liberated grades within each grinding period are distinct. However, the classification accuracy was not as good as expected. The reason for this was attributed to the performance of the digital camera and to impurities of the sample.; A model which predicts particle grade distribution resulting from the constructed material is presented. This model is based on shape descriptors and was derived from the general population balance model. The model is limited to one descriptor and is based on some limiting assumptions. The agreement to experimental data was marginally successful. This study should be considered a preliminary one and more research is needed.