S. A. Marfo, Prince Opoku Appau, J. Acquah, E. M. Amarfio
The increasing exploration and production activities in the offshore Cape Three Point Blocks of Ghana have led to the discovery and development of gas condensate fields in addition to the oil fields which produce significant amount of condensate gas. These discoveries require pipelines to transport the fluids avoiding hydrates and wax formation. This paper focuses on subsea pipeline design using Pipesim software that addresses flow assurance problems associated with transporting condensate gas from the Jubilee and TEN Fields to the Atuabo Gas Processing Plant. It also considered an alternate design that eliminates the need for capacity increase of flowlines for the futuristic highest projected flow rates in 2030. The design comprises of two risers and two flowlines. Hydrate formation temperature was determined to be 72.5 ˚F at a pressure of 3 000 psig. The insulation thickness for flowlines 1 and 2 were determined to be 1.5 in. and 2 in. respectively. The pipe size for flowlines 1 and 2 were determined to be 12 in. and 14 in. respectively. The maximum designed flow rate was determined to be 150 MMSCFD. To meet the highest projected flow rate of 700 MMSCFD in the year 2030 at the processing plant, a 16 in. ID pipeline of 44 km length was placed parallel to the 12 in. ID flowline 1. This parallel pipeline increased the designed flow rate by approximately 4.7 times (705 MMSCFD). The alternate design employs 18 in. and 20 in. ID pipes for flowlines 1 and 2 respectively. Keywords: Condensate Gas; Flowline; Flow Assurance; Hydrate; Pipesim
加纳Cape Three Point海上区块的勘探和生产活动不断增加，除了产生大量凝析气的油田外，还发现和开发了凝析气田。这些发现需要管道输送流体，以避免水合物和蜡的形成。本文重点介绍了使用Pipesim软件进行海底管道设计，该软件解决了从Jubilee和TEN油田向Atuabo天然气处理厂输送凝析气的流动保证问题。该公司还考虑了另一种设计方案，该方案消除了为实现2030年最高预计流量而增加管线容量的需求。该设计包括两个立管和两个流管。在3000 psig压力下，水合物形成温度为72.5˚F。管线1和管线2的绝缘厚度确定为1.5英寸。2英寸。分别。管线1和管线2的管径为12英寸。14英寸。分别。最大设计流量为150 MMSCFD。为了在2030年达到700万立方英尺/天的最高预计流量，16英寸/天的管道将被投入到生产中。长度为44公里的内径管道与12英寸管道平行放置。ID流程1。该平行管道将设计流量提高了约4.7倍(705 MMSCFD)。另一种设计采用了18英寸。20英寸。分别为流程1和2的内径管道。关键词:凝析气;流线;流保证;水合物;Pipesim
{"title":"Flow Assurance in Subsea Pipeline Design - A Case Study of Ghana’s Jubilee and TEN Fields","authors":"S. A. Marfo, Prince Opoku Appau, J. Acquah, E. M. Amarfio","doi":"10.4314/GM.V19I1.9","DOIUrl":"https://doi.org/10.4314/GM.V19I1.9","url":null,"abstract":"The increasing exploration and production activities in the offshore Cape Three Point Blocks of Ghana have led to the discovery and development of gas condensate fields in addition to the oil fields which produce significant amount of condensate gas. These discoveries require pipelines to transport the fluids avoiding hydrates and wax formation. This paper focuses on subsea pipeline design using Pipesim software that addresses flow assurance problems associated with transporting condensate gas from the Jubilee and TEN Fields to the Atuabo Gas Processing Plant. It also considered an alternate design that eliminates the need for capacity increase of flowlines for the futuristic highest projected flow rates in 2030. The design comprises of two risers and two flowlines. Hydrate formation temperature was determined to be 72.5 ˚F at a pressure of 3 000 psig. The insulation thickness for flowlines 1 and 2 were determined to be 1.5 in. and 2 in. respectively. The pipe size for flowlines 1 and 2 were determined to be 12 in. and 14 in. respectively. The maximum designed flow rate was determined to be 150 MMSCFD. To meet the highest projected flow rate of 700 MMSCFD in the year 2030 at the processing plant, a 16 in. ID pipeline of 44 km length was placed parallel to the 12 in. ID flowline 1. This parallel pipeline increased the designed flow rate by approximately 4.7 times (705 MMSCFD). The alternate design employs 18 in. and 20 in. ID pipes for flowlines 1 and 2 respectively. Keywords: Condensate Gas; Flowline; Flow Assurance; Hydrate; Pipesim","PeriodicalId":12530,"journal":{"name":"Ghana Mining Journal","volume":"51 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-06-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77197821","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This work presents prediction and optimisation of controllable parameters of drilling and blasting currently used at the Fobinso Pit of Perseus Mining Ghana Limited (PMGL). The mine faces challenges with blast particle sizes produced after primary blasting. The presence of boulders requires secondary fragmentation to further reduce the broken materials to the acceptable sizes, thereby increasing the cost of production. The mechanical properties of the rocks were determined using Protodyakonov Rock Strength Index. The drill and blast parameters were estimated using the Konya and Walter (1990), Principle of Proportionality, and Instituto Geologo Minero de España (IGME) model developed in 1987. The Modified Kuz-Ram model was used to predict and analyse the results of blasting based on the parameters such as spacing, burden, drillhole diameter, charge density, charge per hole, charge length, and powder factor. A comparative analysis of the predicted size distributions of the various models using diameters of 65 mm and 110 mm revealed no significant differences between the size fractions. The Principle of Proportionality produced the best technical and economic indices for blasting. Keywords: Fragmentation, Drilling Parameters, Primary Blasting, Models, Secondary Blasting
这项工作提出了目前在Perseus矿业加纳有限公司(PMGL)的Fobinso坑使用的钻井和爆破可控参数的预测和优化。该矿初次爆破后产生的炸药粒度问题是该矿面临的挑战。砾石的存在需要二次破碎，以进一步减少破碎物料到可接受的尺寸，从而增加了生产成本。采用Protodyakonov岩石强度指数测定岩石的力学性能。利用Konya和Walter(1990)、比例原理和1987年开发的Instituto Geologo Minero de España (IGME)模型估算了钻井和爆破参数。采用改进的Kuz-Ram模型，对爆破效果进行了预测和分析，该模型基于爆破间距、装药量、钻孔直径、装药密度、单孔装药量、装药长度和火药因子等参数。比较分析了不同模型在直径为65 mm和110 mm时的预测粒度分布，发现粒径分数之间没有显著差异。根据比例原理，得出了爆破的最佳技术经济指标。关键词:破片，钻孔参数，初爆，模型，二次爆破
{"title":"A Comparative Analysis of Rock Fragmentation using Blast Prediction Results","authors":"G. Agyei, M. Owusu-Tweneboah","doi":"10.4314/GM.V19I1","DOIUrl":"https://doi.org/10.4314/GM.V19I1","url":null,"abstract":"This work presents prediction and optimisation of controllable parameters of drilling and blasting currently used at the Fobinso Pit of Perseus Mining Ghana Limited (PMGL). The mine faces challenges with blast particle sizes produced after primary blasting. The presence of boulders requires secondary fragmentation to further reduce the broken materials to the acceptable sizes, thereby increasing the cost of production. The mechanical properties of the rocks were determined using Protodyakonov Rock Strength Index. The drill and blast parameters were estimated using the Konya and Walter (1990), Principle of Proportionality, and Instituto Geologo Minero de España (IGME) model developed in 1987. The Modified Kuz-Ram model was used to predict and analyse the results of blasting based on the parameters such as spacing, burden, drillhole diameter, charge density, charge per hole, charge length, and powder factor. A comparative analysis of the predicted size distributions of the various models using diameters of 65 mm and 110 mm revealed no significant differences between the size fractions. The Principle of Proportionality produced the best technical and economic indices for blasting. Keywords: Fragmentation, Drilling Parameters, Primary Blasting, Models, Secondary Blasting","PeriodicalId":12530,"journal":{"name":"Ghana Mining Journal","volume":"87 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-06-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76804476","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The major source of potable water in Tarkwa is the Bonsa Treatment Plant sourced from the Bonsa River. The activities of illegal miners along the banks of the Bonsa River has resulted in pollution of the river. This has resulted in high treatment cost and irregular supply of water to the Tarkwa Township and surrounding communities that are fed by the Bonsa Treatment Plant. In view of the difficulty in getting frequent and regular potable supply of water, people have resorted to construction of boreholes and hand-dug wells. However, the success rates and borehole yields are low especially in the hydrogeologically difficult terrains in the Tarkwa area. The aim of this paper is to investigate the hydrogeological conditions of the Tarkwa area using both the Electrical Resistivity Imaging (ERI) and Electromagnetic (EM) geophysical techniques to determine the electrical resistivity and conductivity values that are related to groundwater accumulation, so that potential water-bearing zones can be identified. Results from electrical resistivity show that the general resistivity distribution in the Tarkwa area is between 32 Ωm and 100 000 Ωm. Water-bearing zones in the Huni Sandstone occur to a depth of 35 m with an average resistivity value of 400 Ωm, at a depth of 60 m and a resistivity of 600 Ωm in the Tarkwa Phyllite, at a depth of 55 m and a resistivity of 600 Ωm in the Banket Series and 50 m depth with resistivity value of 500 Ωm in the Kawere Conglomerate respectively. The electromagnetic conductivity values also show that the general conductivity distribution in the Tarkwa area is 3 – 32 S/m. The application of electrical resistivity and electromagnetic techniques separately gives success rate of 80 % and 65 % respectively. An improved success rate of 86 % is achieved combining the two techniques. Keywords: Electrical Resistivity Imaging, Electromagnetic Method, Groundwater
{"title":"Combined Electrical Resistivity Imaging and Electromagnetic Survey for Groundwater Studies in the Tarkwa Mining Area, Ghana","authors":"J. Seidu, A. Ewusi, J. Kuma","doi":"10.4314/GM.V19I1.4","DOIUrl":"https://doi.org/10.4314/GM.V19I1.4","url":null,"abstract":"The major source of potable water in Tarkwa is the Bonsa Treatment Plant sourced from the Bonsa River. The activities of illegal miners along the banks of the Bonsa River has resulted in pollution of the river. This has resulted in high treatment cost and irregular supply of water to the Tarkwa Township and surrounding communities that are fed by the Bonsa Treatment Plant. In view of the difficulty in getting frequent and regular potable supply of water, people have resorted to construction of boreholes and hand-dug wells. However, the success rates and borehole yields are low especially in the hydrogeologically difficult terrains in the Tarkwa area. The aim of this paper is to investigate the hydrogeological conditions of the Tarkwa area using both the Electrical Resistivity Imaging (ERI) and Electromagnetic (EM) geophysical techniques to determine the electrical resistivity and conductivity values that are related to groundwater accumulation, so that potential water-bearing zones can be identified. Results from electrical resistivity show that the general resistivity distribution in the Tarkwa area is between 32 Ωm and 100 000 Ωm. Water-bearing zones in the Huni Sandstone occur to a depth of 35 m with an average resistivity value of 400 Ωm, at a depth of 60 m and a resistivity of 600 Ωm in the Tarkwa Phyllite, at a depth of 55 m and a resistivity of 600 Ωm in the Banket Series and 50 m depth with resistivity value of 500 Ωm in the Kawere Conglomerate respectively. The electromagnetic conductivity values also show that the general conductivity distribution in the Tarkwa area is 3 – 32 S/m. The application of electrical resistivity and electromagnetic techniques separately gives success rate of 80 % and 65 % respectively. An improved success rate of 86 % is achieved combining the two techniques. Keywords: Electrical Resistivity Imaging, Electromagnetic Method, Groundwater","PeriodicalId":12530,"journal":{"name":"Ghana Mining Journal","volume":"203 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-06-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77721368","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Many gold processing plants are experiencing challenges as mining pits are becoming deeper, rocks are getting harder and more complex polymetallic and refractory ores are being encountered. The variations in the characteristics of ores lead to deviations from the established parameters, and these affect gold extraction efficiency. This paper presents a study where geological characteristics of the ore types from some mining pits were used to ascertain the influence of ore blends on improving the performances of comminution and leaching circuits. To achieve this, mineralogical, comminution, gravity recoverable gold and leaching investigations were conducted on fresh and weathered ore samples and their blends. Mineralogical study showed that the main rock types associated with the mine pits were dolerite, phyllites, conglomerates and sandstone. The dominant minerals were quartz, plagioclase, with traces of pyrites. The Crushability Work Indices of the rocks were between 30 and 37 KWh/t, which are generally higher than the maximum design value of 31.9 kWh/t, and this situation will pose throughput challenges in that section. The Bond Ball Mill Work Indices of the blends tested were between 16.4 kWh/t and 9.6 kWh/t and a blend ratio of 85% fresh and 15% weathered was found to have a Bond Ball Work Index almost equal to the design value of 14 kWh/t. With gold assays of 2.5 g/t for dolerite, 2.1 g/t for phyllite, 3.7 g/t for sandstone and 3.4 g/t for conglomerate, the gravity recoverable gold was in the order of sandstone 36% > phyllite (31.5%) > dolerite (29.5%) > conglomerate (18%). The overall gold recoveries were in the sequence of conglomerate (95%), sandstone (94%), phyllite (92%) and dolerite (87%). This information could be utilised in developing a proactive plant operations strategies for an operating plant in order to ultimately manage the plant and enhance achievement of set targets. Keywords: Geometallurgy; Ore Blends; Characterisation; Communition Circuit Performance; Gold Recovery
{"title":"Geometallurgical Studies on Gold Ore for Enhanced Comminution and Leaching","authors":"G. Ofori-Sarpong, T. Okwaisie, R. Amankwah","doi":"10.4314/gm.v19i1.7","DOIUrl":"https://doi.org/10.4314/gm.v19i1.7","url":null,"abstract":"Many gold processing plants are experiencing challenges as mining pits are becoming deeper, rocks are getting harder and more complex polymetallic and refractory ores are being encountered. The variations in the characteristics of ores lead to deviations from the established parameters, and these affect gold extraction efficiency. This paper presents a study where geological characteristics of the ore types from some mining pits were used to ascertain the influence of ore blends on improving the performances of comminution and leaching circuits. To achieve this, mineralogical, comminution, gravity recoverable gold and leaching investigations were conducted on fresh and weathered ore samples and their blends. Mineralogical study showed that the main rock types associated with the mine pits were dolerite, phyllites, conglomerates and sandstone. The dominant minerals were quartz, plagioclase, with traces of pyrites. The Crushability Work Indices of the rocks were between 30 and 37 KWh/t, which are generally higher than the maximum design value of 31.9 kWh/t, and this situation will pose throughput challenges in that section. The Bond Ball Mill Work Indices of the blends tested were between 16.4 kWh/t and 9.6 kWh/t and a blend ratio of 85% fresh and 15% weathered was found to have a Bond Ball Work Index almost equal to the design value of 14 kWh/t. With gold assays of 2.5 g/t for dolerite, 2.1 g/t for phyllite, 3.7 g/t for sandstone and 3.4 g/t for conglomerate, the gravity recoverable gold was in the order of sandstone 36% > phyllite (31.5%) > dolerite (29.5%) > conglomerate (18%). The overall gold recoveries were in the sequence of conglomerate (95%), sandstone (94%), phyllite (92%) and dolerite (87%). This information could be utilised in developing a proactive plant operations strategies for an operating plant in order to ultimately manage the plant and enhance achievement of set targets. Keywords: Geometallurgy; Ore Blends; Characterisation; Communition Circuit Performance; Gold Recovery","PeriodicalId":12530,"journal":{"name":"Ghana Mining Journal","volume":"1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81447769","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Damang Gold Mine (DGM) in Ghana uses open pit mining technology to mine its gold deposit. It has an estimated mineable gold reserve of about 32 Mt exploitable for 8 years. As the gold price kept falling from 2013 and operating cost kept rising, the mine down sized its operations. But the operations became challenging due to poor performance of ageing mining equipment and processing plant, and the need for a new tailings dam. As the gold price stabilises, it could be gainful to invest capital to resolve the challenges and increase production. This study aims at investigating whether DGM would be economically viable if the intended investment is made assuming the gold price falls to US$ 32.15/g. The study estimates the required capital and annual operating cost to be US$89.49 M and US$100.84 M respectively. A cash flow analysis is carried out assuming no price escalation, discount rate of 20%, and applying the following investment laws of Ghana: royalty of 5% of gross revenue; straight line depreciation of capital expenditure over five years (20% per year); investment allowance of 5% in the first year only; loss carry forward; and corporate tax of 35%. The results give Net Present Value of US$82 723 720.28 and Internal Rate of Return of 41.13%, indicating profitability. Sensitivity analysis reveals that the project will continue to be profitable until the revenue falls below 24%, assuming all other economic parameters remain constant. The project will also continue to be profitable until the operating cost increases beyond 30%, assuming all other economic parameters remain constant. Risk analysis on the project indicates the project has 70% chances of success. DGM could invest the capital to mine its gold reserves because the mine will make profit provided cost is controlled and production level maintained to generate needed revenue. Keywords: Net Present Value, Internal Rate of Return, Sensitivity Analysis, Risk Analysis
{"title":"Can Capital Injection Make Challenged Gold Projects in Ghana Economically Viable? – A Case Study","authors":"D. Mireku-Gyimah, R. Gyebuni","doi":"10.4314/gm.v19i1.5","DOIUrl":"https://doi.org/10.4314/gm.v19i1.5","url":null,"abstract":"Damang Gold Mine (DGM) in Ghana uses open pit mining technology to mine its gold deposit. It has an estimated mineable gold reserve of about 32 Mt exploitable for 8 years. As the gold price kept falling from 2013 and operating cost kept rising, the mine down sized its operations. But the operations became challenging due to poor performance of ageing mining equipment and processing plant, and the need for a new tailings dam. As the gold price stabilises, it could be gainful to invest capital to resolve the challenges and increase production. This study aims at investigating whether DGM would be economically viable if the intended investment is made assuming the gold price falls to US$ 32.15/g. The study estimates the required capital and annual operating cost to be US$89.49 M and US$100.84 M respectively. A cash flow analysis is carried out assuming no price escalation, discount rate of 20%, and applying the following investment laws of Ghana: royalty of 5% of gross revenue; straight line depreciation of capital expenditure over five years (20% per year); investment allowance of 5% in the first year only; loss carry forward; and corporate tax of 35%. The results give Net Present Value of US$82 723 720.28 and Internal Rate of Return of 41.13%, indicating profitability. Sensitivity analysis reveals that the project will continue to be profitable until the revenue falls below 24%, assuming all other economic parameters remain constant. The project will also continue to be profitable until the operating cost increases beyond 30%, assuming all other economic parameters remain constant. Risk analysis on the project indicates the project has 70% chances of success. DGM could invest the capital to mine its gold reserves because the mine will make profit provided cost is controlled and production level maintained to generate needed revenue. Keywords: Net Present Value, Internal Rate of Return, Sensitivity Analysis, Risk Analysis","PeriodicalId":12530,"journal":{"name":"Ghana Mining Journal","volume":"16 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85435189","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Gypsum exists in the Dihydrate (CaSO4 2H2O), Hemihydrate (CaSO4. ½H2O) and the Anhydrite (CaSO4) forms. The exploitation of the natural rock form deposit of gypsum is on the increase, necessitating the need to find alternative and efficient sources of gypsum so as to sustain all the industries dependent on gypsum as raw material. This work investigates the production of gypsum from clamshells and waste sulphuric acid from end-of-life car batteries. Clamshells obtained from the Volta Region of Ghana were calcined at a temperature of about 1000 ˚C with a view of producing CaO which was pulverised to particle size of 96 % passing 106 μm. Samples of the Pulverised Clam Shells (PCS) were then reacted with five different concentrations of the Waste Battery Acid (WBA). The reaction was observed to be very exothermic; a temperature of 101 ˚C was obtained for the 6.5 M concentration of WBA. The resulting mixture was filtered and an XRD analysis was performed on the oven dried residue to ascertain its composition. The findings from the work revealed that 100 g of pulverised clam shells produced an average of 58.08 g of calcined product and 134 g of gypsum. Peaks of SiO2 and CaCO3 in the XRD diffractogram of the gypsum indicated that the reaction between PCS and WBA was incomplete. Conclusively, the results from the XRD analysis showed peaks of the three forms of gypsum that was successfully produced. Keywords: Net Present Value; Internal Rate of Return; Sensitivity Analysis; Risk Analysis
石膏存在于二水合(caso42h2o)、半水合(CaSO4)。1 / 2h2o)和硬石膏(CaSO4)形成。对天然岩石石膏矿床的开采正在增加，因此需要寻找替代和有效的石膏来源，以维持所有依赖石膏作为原料的工业。这项工作研究了从蛤壳中生产石膏和从报废的汽车电池中生产废硫酸。将产自加纳Volta地区的蛤壳在1000℃左右的温度下进行煅烧，制备出粒径达96% - 106 μm的CaO。然后将粉碎的蛤蜊壳(PCS)样品与五种不同浓度的废电池酸(WBA)反应。观察到该反应是非常放热的;6.5 M WBA的温度为101℃。对所得混合物进行过滤，并对烘箱干渣进行XRD分析，确定其成分。研究结果显示，100克粉碎的蛤蜊壳平均产生58.08克的煅烧产物和134克的石膏。石膏的XRD衍射图中SiO2和CaCO3峰表明PCS与WBA反应不完全。最后，XRD分析结果显示了成功制备的三种形态石膏的峰。关键词:净现值;内部收益率;敏感性分析;风险分析
{"title":"Production of Gypsum from Clamshells and Waste Acid Recovered from End-of-Life Lead Acid Batteries","authors":"H. D. Gohoho, J. R. Dankwah","doi":"10.4314/gm.v19i1.8","DOIUrl":"https://doi.org/10.4314/gm.v19i1.8","url":null,"abstract":"Gypsum exists in the Dihydrate (CaSO4 2H2O), Hemihydrate (CaSO4. ½H2O) and the Anhydrite (CaSO4) forms. The exploitation of the natural rock form deposit of gypsum is on the increase, necessitating the need to find alternative and efficient sources of gypsum so as to sustain all the industries dependent on gypsum as raw material. This work investigates the production of gypsum from clamshells and waste sulphuric acid from end-of-life car batteries. Clamshells obtained from the Volta Region of Ghana were calcined at a temperature of about 1000 ˚C with a view of producing CaO which was pulverised to particle size of 96 % passing 106 μm. Samples of the Pulverised Clam Shells (PCS) were then reacted with five different concentrations of the Waste Battery Acid (WBA). The reaction was observed to be very exothermic; a temperature of 101 ˚C was obtained for the 6.5 M concentration of WBA. The resulting mixture was filtered and an XRD analysis was performed on the oven dried residue to ascertain its composition. The findings from the work revealed that 100 g of pulverised clam shells produced an average of 58.08 g of calcined product and 134 g of gypsum. Peaks of SiO2 and CaCO3 in the XRD diffractogram of the gypsum indicated that the reaction between PCS and WBA was incomplete. Conclusively, the results from the XRD analysis showed peaks of the three forms of gypsum that was successfully produced. Keywords: Net Present Value; Internal Rate of Return; Sensitivity Analysis; Risk Analysis","PeriodicalId":12530,"journal":{"name":"Ghana Mining Journal","volume":"17 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73703587","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Stochastic simulation was conducted to analyse the fuel consumption of a shovel-truck system. An example shovel-truck system, comprising a single shovel and four trucks was considered. At 95% confidence interval, the monthly simulated fuel consumption by the shovel-truck system was found to be about 198 127 litres against the actual fuel consumption of 203 772 litres, registering a variance of -2.70%. About 22 000 litres of fuel was consumed per month due to truck waiting. Optimising the fuel consumption and truck waiting time can result in significant fuel savings. The paper demonstrates that stochastic simulation is an effective tool for optimising the utilisation of fossil-based fuels in mining and related industries. Keywords: Stochastic, Simulation Modelling, Mining, Optimisation, Shovel-Truck Material Handling
{"title":"Assessment of Rescue Facilities and Personnel in the Ghanaian Underground Mines","authors":"Sylvester Yenzanya, N. Amegbey","doi":"10.4314/gm.v18i1.7","DOIUrl":"https://doi.org/10.4314/gm.v18i1.7","url":null,"abstract":"Stochastic simulation was conducted to analyse the fuel consumption of a shovel-truck system. An example shovel-truck system, comprising a single shovel and four trucks was considered. At 95% confidence interval, the monthly simulated fuel consumption by the shovel-truck system was found to be about 198 127 litres against the actual fuel consumption of 203 772 litres, registering a variance of -2.70%. About 22 000 litres of fuel was consumed per month due to truck waiting. Optimising the fuel consumption and truck waiting time can result in significant fuel savings. The paper demonstrates that stochastic simulation is an effective tool for optimising the utilisation of fossil-based fuels in mining and related industries. Keywords: Stochastic, Simulation Modelling, Mining, Optimisation, Shovel-Truck Material Handling","PeriodicalId":12530,"journal":{"name":"Ghana Mining Journal","volume":"116 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2018-06-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79285912","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The change in climatic conditions and its catastrophic effect on mining activities has become a source of worry for mining industries and therefore needs due attention. This study examined the effect some climate factors have on gold production in Ghana. First, a direct Multiple Linear Regression was applied on the climate factors with the aim of determining the relative effect of each factor on gold production which exhibited a time series structure. The consequence is that, the estimates of the coefficients and their standard errors will be wrongly estimated if the time series structure of the errors is ignored. In order to eliminate these deficiencies and better understand the effect of these climate factors on gold production, regression with ARIMA errors technique was employed after its appropriateness has been tested. The model was then compared in terms of prediction accuracy which resulted a MAPE of 9.78%. It was concluded that, gold production in Ghana is positively related to Temperature whilst negatively to Rainfall and Precipitate. It was recommended that mine operators in Ghana could base on this analysis to optimise their production planning and scheduling. Keywords: Gold Production, Climate, Multicollinearity, VIF, Regression Models with ARIMA Errors
{"title":"Multivariate Analysis of the Effect of Climate Conditions on Gold Production in Ghana","authors":"S. T. Appiah, A. Buabeng, N. Dumakor-Dupey","doi":"10.4314/GM.V18I1","DOIUrl":"https://doi.org/10.4314/GM.V18I1","url":null,"abstract":"The change in climatic conditions and its catastrophic effect on mining activities has become a source of worry for mining industries and therefore needs due attention. This study examined the effect some climate factors have on gold production in Ghana. First, a direct Multiple Linear Regression was applied on the climate factors with the aim of determining the relative effect of each factor on gold production which exhibited a time series structure. The consequence is that, the estimates of the coefficients and their standard errors will be wrongly estimated if the time series structure of the errors is ignored. In order to eliminate these deficiencies and better understand the effect of these climate factors on gold production, regression with ARIMA errors technique was employed after its appropriateness has been tested. The model was then compared in terms of prediction accuracy which resulted a MAPE of 9.78%. It was concluded that, gold production in Ghana is positively related to Temperature whilst negatively to Rainfall and Precipitate. It was recommended that mine operators in Ghana could base on this analysis to optimise their production planning and scheduling. Keywords: Gold Production, Climate, Multicollinearity, VIF, Regression Models with ARIMA Errors","PeriodicalId":12530,"journal":{"name":"Ghana Mining Journal","volume":"29 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2018-06-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76891518","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
R. Amankwah, G. Ofori-Sarpong, Abigail Ewoenam Adzigbli
A typical challenge encountered on most gold processing plants during leaching of refractory ores is the reduction in recovery due to the presence of carbonaceous matter which preg-robs dissolved gold. To reduce preg-robbing during cyanidation, carbonaceous matter has to undergo pretreatment to passivate the active surface. The fungus, Phanerochaete chrysosporium has been shown to biotransform carbonaceous matter, thus reducing its ability to preg-rob gold. However, the possible transfer of entrained fungal biomass into Carbon-In-Leach (CIL) circuits has been reported to decrease the activity of activated carbon, and a proposed solution to this was to wash the fungal-treated material thoroughly with water before CIL operation. This paper therefore set out to assess the effect of water-washing on aurocyanide adsorption by activated carbon in CIL following fungal pretreatment of carbonaceous ores. To realise the objective, activated carbon was contacted with cell-free extract of P. chrysosporium under varying conditions of pH and time, after which it was washed with different volumes of water, and its gold-adsorption ability assessed. The results revealed a decrease in the activity of activated carbon as a function of increasing contact time with the cell-free extract. The percentage decrease was higher after treatment in the acidic medium (13%) than the basic medium (9%). After washing the carbon (treated in acidic medium), gold adsorption was found to increase directly with the volume of water used from 64% at 0 mL to 84% at 500 mL and 91% at 1000 mL. Correspondingly, the carbon treated in basic medium recorded 69% at 0 mL to 87% at 500 mL and 93% at 1000 mL. This paper thus concludes that, sufficient water washing should be employed after fungal-biotransformation of refractory ores before CIL operation to decrease the effect of entrained biomass on the adsorption capacity of activated carbon. Keywords: Carbonaceous Gold Ore, Activated Carbon, Carbon-In-Leach, Cell-Free Extracts
{"title":"Water Washing of Fungal-treated Carbonaceous Ores: Effect on Aurocyanide Adsorption by Activated Carbon in CIL Circuit","authors":"R. Amankwah, G. Ofori-Sarpong, Abigail Ewoenam Adzigbli","doi":"10.4314/gm.v18i1.8","DOIUrl":"https://doi.org/10.4314/gm.v18i1.8","url":null,"abstract":"A typical challenge encountered on most gold processing plants during leaching of refractory ores is the reduction in recovery due to the presence of carbonaceous matter which preg-robs dissolved gold. To reduce preg-robbing during cyanidation, carbonaceous matter has to undergo pretreatment to passivate the active surface. The fungus, Phanerochaete chrysosporium has been shown to biotransform carbonaceous matter, thus reducing its ability to preg-rob gold. However, the possible transfer of entrained fungal biomass into Carbon-In-Leach (CIL) circuits has been reported to decrease the activity of activated carbon, and a proposed solution to this was to wash the fungal-treated material thoroughly with water before CIL operation. This paper therefore set out to assess the effect of water-washing on aurocyanide adsorption by activated carbon in CIL following fungal pretreatment of carbonaceous ores. To realise the objective, activated carbon was contacted with cell-free extract of P. chrysosporium under varying conditions of pH and time, after which it was washed with different volumes of water, and its gold-adsorption ability assessed. The results revealed a decrease in the activity of activated carbon as a function of increasing contact time with the cell-free extract. The percentage decrease was higher after treatment in the acidic medium (13%) than the basic medium (9%). After washing the carbon (treated in acidic medium), gold adsorption was found to increase directly with the volume of water used from 64% at 0 mL to 84% at 500 mL and 91% at 1000 mL. Correspondingly, the carbon treated in basic medium recorded 69% at 0 mL to 87% at 500 mL and 93% at 1000 mL. This paper thus concludes that, sufficient water washing should be employed after fungal-biotransformation of refractory ores before CIL operation to decrease the effect of entrained biomass on the adsorption capacity of activated carbon. Keywords: Carbonaceous Gold Ore, Activated Carbon, Carbon-In-Leach, Cell-Free Extracts","PeriodicalId":12530,"journal":{"name":"Ghana Mining Journal","volume":"35 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2018-06-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84324495","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A mine planning team is tasked among other duties with designing a feasible mine plan which in turn maps out the daily running of the mining project. A mine plan revolves around a cut-off grade which is thoughtfully and uniquely selected while considering various aspects such as grade tonnage distribution, economic and operational parameters specific to a mine. Selection of a cut-off grade can be a daunting task often involving iterative and lengthy mathematical formulas which take huge amounts of time to execute, often leaving room for error. In the occurrence of such errors, a mining project can be faced with sequential outcomes that could even lead to premature closure. The cut-off grade is therefore a strategic variable that determines the economic viability of a mine, and hence return on investment. It is critical that the cut-off grade is optimal so as to maximise the net present value. Lane’s approach is a model that utilises several steps to yield one cut-off grade value. This algorithm is flexible and can be adjusted to include other factors specific to a mine. Regrettably, many mining companies continue to operate using inaccurate cut-off grades wrongly calculated or assumed. This has continuously led to frustrations due to losses and prematurely abandoned mines. This study focused on the development and implementation of an easy to use computer application based on Lane’s approach that runs on Windows platform, and hence targeting a larger user base for choosing an optimum cut-off grade for open pit mines. Keywords: Cut-Off Optimisation, Cut-Off Optimiser, Optimum Cut-Off Grades, Whittle
{"title":"Computer-Aided Cut-off Grade Optimisation for Open Pit Mines","authors":"J. Muriuki, V. Temeng","doi":"10.4314/gm.v18i2","DOIUrl":"https://doi.org/10.4314/gm.v18i2","url":null,"abstract":"A mine planning team is tasked among other duties with designing a feasible mine plan which in turn maps out the daily running of the mining project. A mine plan revolves around a cut-off grade which is thoughtfully and uniquely selected while considering various aspects such as grade tonnage distribution, economic and operational parameters specific to a mine. Selection of a cut-off grade can be a daunting task often involving iterative and lengthy mathematical formulas which take huge amounts of time to execute, often leaving room for error. In the occurrence of such errors, a mining project can be faced with sequential outcomes that could even lead to premature closure. The cut-off grade is therefore a strategic variable that determines the economic viability of a mine, and hence return on investment. It is critical that the cut-off grade is optimal so as to maximise the net present value. Lane’s approach is a model that utilises several steps to yield one cut-off grade value. This algorithm is flexible and can be adjusted to include other factors specific to a mine. Regrettably, many mining companies continue to operate using inaccurate cut-off grades wrongly calculated or assumed. This has continuously led to frustrations due to losses and prematurely abandoned mines. This study focused on the development and implementation of an easy to use computer application based on Lane’s approach that runs on Windows platform, and hence targeting a larger user base for choosing an optimum cut-off grade for open pit mines. Keywords: Cut-Off Optimisation, Cut-Off Optimiser, Optimum Cut-Off Grades, Whittle","PeriodicalId":12530,"journal":{"name":"Ghana Mining Journal","volume":"237 1 1","pages":"1-8"},"PeriodicalIF":0.0,"publicationDate":"2018-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72944741","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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