Effective Communition Energy of Faya Clay, Using Determined Work Index (Modified Bond Energy Method)

Abstract

The work index of Faya clay in Faya Village, Plateau State, Nigeria was determined for effective communition design using Berry and Bruce method.  Samples of Faya clay were collected from three veins on the mine. The samples were homogenized, crushed and ground and further sampled using conning and quartering to obtain 5.0 kg representative fraction of the ore. 1.0 kg was used for composition study while 4.0 kg for experimental work. Azara barite from Nassarawa state, with work index 6.24 kwh/ton was used as the reference sample. The test and reference samples were subjected to sieve size analysis under the same condition to obtain 80% passing for both the mill feeds and products. The chemical analysis of test and reference samples shows that they both contain; SiO2, K2O, CaO, Fe2O3, TiO2  and  BaO as major oxides. This is an indication that Azara barite is a suitable reference sample for Faya clay. The mineral composition of Faya clay was determined by the use of the X-ray diffraction (XRD) analysis. The major mineral phases in the clay sample are 61.7% wt. quartz (SiO2) 28.59% wt. dickite (Al2 Si2O5 (OH)). 8.89% wt. geothite (FeO (OH)4) and 0.83% wt. muscovite (K0.92 Na0.08) (Al1.86 Fe0.07 Ti0.02) (Si3.03 Al0.97) 010(OH)2, at 2θ. The SEM/EDS revealed that the dominant elements in the clay are oxygen with average weight composition of 43.75% wt. at 60 µm and 45.78 % wt. at 6 µm and silicon with 21.24% wt. at 60 µm and 27.58% wt. at 6 µm. The result of the particle size analyses of the mill feeds and products of milling indicated that 80% passing and retained as obtained from the semi-log plots were 180 µm and 125 µm for the test sample, and 250 µm and 180 µm for the reference sample. The results were validated by calculation using the Guadin- schuhman logarithm equation (log-log plots) and were in agreement with those of the semi-log plots. The value of the work index of the test sample (Faya clay) was found to be 4.83 kwh/ton. This is in line with the SEM/EDS result, indicating that Faya clay has large grains, requiring little energy to dissociate the gangue from the mineral of interest.