Ofori-Sarpong G.,Pennsylvania State University |
Amankwah R.K.,University of Mines and Technology
Minerals Engineering | Year: 2011
In many laboratories and processing plants, different comminution equipment are used in preparing gold ores for gravity concentration. For malleable metals such as gold, particle shape changes in response to the forces applied during comminution, and these shapes can influence gravity concentration. In this study, the morphology of gold particles milled in different equipment was investigated. The disc and hammer mills generated cigar-shaped and globular particles respectively. The vibratory pulveriser created flaky particles while the ball mill formed a mix of flaky, folded and irregularly shaped particles. Gravity concentration produced enrichment ratios of 28.3, 24.0, 23.6 and 21.7 for the hammer mill, disc mill, ball mill and vibratory pulveriser respectively. The results show that the comminution equipment utilized should be taken into consideration in decisions regarding gravity gold recovery. © 2010 Elsevier Ltd. All rights reserved.
Amankwah R.K.,University of Mines and Technology |
Ofori-Sarpong G.,Pennsylvania State University
Minerals Engineering | Year: 2011
In leaching processes, the mass transport of lixiviants from the bulk of the solution to the site of the mineral of interest is usually the slowest step. Diffusion becomes slower when the particles to be leached are occluded in host minerals. Access to the mineral of interest is enhanced by micro-crack formation within the host minerals as it enhances percolation and migration of lixiviants. Micro-crack formation also augments grinding and allows size reduction and liberation at a lower stress level. In this research, microwave pretreatment was used to augment the grinding of a free-milling gold ore containing quartz, silicates and iron oxides. Under microwave irradiation, selective heating of the different mineral components resulted in thermal stress cracking. Microwave processing enhanced the grindability of the ore, and crushing strength was reduced by 31.2%. The presence of micro-cracks improved leaching rate, and over 95% extraction was achieved within 12 h as against 22 h for the non-microwaved sample. Such a strategy can be used to maximize recovery and man-hours on processing plants. © 2010 Elsevier Ltd. All rights reserved.
Sarpong S.,University of Mines and Technology
European Business Review | Year: 2014
Purpose: The purpose of this paper is to examine the recent horsemeat scandal in European markets. The paper is primarily interested in how this scandal has festered and what perhaps ought to be done to ensure consumers get what they feel they should be getting. It also attempts to identify the lapses that have created the basis for this to happen. Design/methodology/approach: The paper mainly draws on reports in the media and discussions generated following the scandal to assess the issues under consideration. It also looks at the issues surrounding the global supply chain environment and provides solutions on how to strengthen the weak links in the meat supply chain. Findings: The paper finds that the scandal has damaged consumer confidence in the industry's ability to regulate itself. It notes that pinpointing risk has become a difficult struggle as retailers are often inundated with data, and suppliers, for lack of time, have become reluctant to "waste time" completing check-lists and audits. The paper maintains that there is the urgent need for adequate inspection and a means to incentivise the food industry to police itself much better. It recognises that lack of visibility and a lack of direct influence over suppliers further down the supply chain have led to distinct problems within the food industry. Originality/value: The paper contributes to an ongoing discussion that has been of considerable concern to many consumers. Its importance lies in the fact that it suggests important measures, which, if implemented, could help in ensuring the elimination of fraud in the food chain. © Emerald Group Publishing Limited.
Pu Y.,University of Mines and Technology
Electronic Journal of Geotechnical Engineering | Year: 2014
Three zones (caving zone, fissure zone, bending zone) will be formed in overlying strata after mining. It is important to understand the distribution of "three zones" in order to conduct gas extraction, strata behaviors and mining under water. Numerical calculation, field measurement, similar material simulation will be used for detecting the distribution of 'three zones' in #1202 longwall face of Yuwu mine in Shanxi province of China to provide gists for gas extraction. Researches show that, on the vertical dimension, the demarcation point between caving zone and fissure zone locates between 29.5m~33.4m. The height of fractured zone is between 60m~64m. © 2014 ejge.
Mohammed S.,University of Mines and Technology
38th Nigeria Annual International Conference and Exhibition, NAICE 2014 - Africa's Energy Corridor: Opportunities for Oil and Gas Value Maximization Through Integration and Global Approach | Year: 2014
A simple approach is presented that utilizes production data to determine original gas-in-place (OGIP). In particular, we propose a "modified" Agarwal-Gardner rate/cumulative decline type curves that yield an anchor point of unity, instead of 1/2π. The advantage of this unit anchor point is that, the normalized pseudopressure drop ratio, which is a plotting function on the abscissa, need not be modified; hence, providing a simpler approach than the traditional methods. The computation of pseudopressure drop ratio (or pseudocumulative function) requires a prior knowledge of average reservoir pressure history, or indirectly, OGIP. Consequently, various methods have been proposed in the literature to solve OGIP. This paper utilizes an approximate gas flowing material balance equation, which was previously presented by this author, to make an initial estimate or provide a "true window" for OGIP. This approximate plot yields two negative slopes during boundary-dominated flow regime - early-time pseudosteady state and late-time pseudosteady state lines. The early-time pseudosteady state line is shown to yield a reasonable initial estimate of OGIP while the late-time pseudosteady state line yields an optimistic result. The proposed approach is applicable to general variable pressure and/or variable rate case for singleand multi-well systems during boundary-dominated flow regime. The method is validated with two simulated data; and then, applied to two field data - one from a single-well system and the other from a multi-well system. Copyright 2014, Society of Petroleum Engineers.