The influence of stemming practice on ground vibration and air blast
By M. Mpofu, S. Ngobese, B. Maphalala, D. Roberts, and S. Khan
Stemming practices at a South African opencast coal mine were assessed and the influence of stemming practices on ground vibration and air blast investigated, using both quantitative and qualitative methods. Some level of non-compliance of actual stemming parameters with design was found. There was no direct correlation between stemming length and excessive air blast and ground vibration. Since stemming parameters are interrelated, it is crucial that all blasting procedures are executed in accordance with best practices and recorded accurately. There is a need for digital systems for capturing on- bench blasting parameters, as current manual data recording and reporting systems are inefficient and prone to errors.
Effects of flotation operational parameters on froth stability and froth recovery
By M. Ostadrahimi, S. Farrokhpay, K. Gharibi, A. Dehghani, and M. Aghajanloo
The effect of flotation operational parameters on froth stability and froth recovery was studied. Froth stability was measured using a special column. It was found that the exponential model is more suitable than the froth height change method for determining froth recovery. The results showed that superficial air velocity and collector dosage have respectively the highest and lowest effect on the froth recovery, and that froth recovery decreases sharply with increasing froth height.
A continuous quality improvement framework for electrowinning current efficiency
By T.E. Moongo and S. Michael
Electrowinning consumes substantial electrical energy and there is a need to improve current efficiency so that energy is utilized efficiently. This research aims to design a continuous quality improvement framework for electrowinning current efficiency. The scope of work focused on applying statistical process control on an online industrial copper electrowinning process
instead of conducting experiments. It was concluded that metallurgical short-circuits (hotspots) had the most significant effect on current efficiency. Bringing hotspots under statistical control
resulted in a 5.40% improvement in current efficiency.
Exploratory development of a rotary offset crusher
By T. Nghipulile, M. Bwalya, M. Moys, and H. Simonsen
The quest for efficiency in comminution is an ongoing concern, as comminution usually constitutes a major cost component in the metal production industry. Such improvements can
be made by circuit optimization or development of more efficient equipment. The original design concept of a novel crusher known as the rotary offset crusher (ROC) was recently rekindled and
a laboratory version built and commissioned at the University of the Witwatersrand. Batch experiments have been conducted and size reduction ratios as high as 11 were recorded from experiments with quartz at a rotational speed of 830 r/min.
Identification of cost factors relating to mining incidents
By E.P. Preis and R.C.W.Webber-Youngman
This work aimed to identify the various cost factors that could arise due to any given mining incident for the purpose of estimating more accurately the total cost of mining incidents. A
total of 34 main cost factors were identified, with numerous sub-factors. General conclusions are drawn from the knowledge obtained and recommendations made on how mining companies
could use the results to assist in the calculation of mining incident costs. The paper provides suggestions for further research, with the main focus being on the most significant immeasurable
cost factors.
Investigation of stress in a pothole in the Bushveld Complex: A case study
By B.P. Watson, D. Hoffmann, and D.P. Roberts
Potholes on the Merensky and UG2 reefs in the Bushveld Complex normally constitute severe disruptions, often with significant fracturing that prevents economic extraction. Stress measurements were conducted in one pothole on the Merensky Reef to determine if the fracturing was due to high stress conditions. This paper describes the results of the measurements. Numerical modelling was done to determine the influence of depth and mining on the stress condition at the site. The results show that high stresses do exist in at least some potholes, and that current theories of pothole formation do not adequately explain the measured stresses. A better understanding of the stress conditions in potholes could lead to more appropriate support design and avoidance of potential rockbursts in these structures.
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