Centers for Ethio Mines Development

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Flowsheet Development Studies for Lega Dembi Gold Process Plant
(Addis Ababa University, 2023-09) Adinew Abebe; Abubeker Yimam (PhD)
This flowsheet advancement of Legadambi processes for gold plant contain different unit operation and unit process. Legadambi gold process plant use different beneficiation mechanism to extract and recover the valuable metal or element of interst from associated mineral or gangue. The process consists seven consecutive and interdependent but segregated unit operating process and unit process. Process those implmented in Legadembi were comminution (crushing and grinding), Thickening and reagent leaching (Extraction), both adsorption and Desorption (stripping), Electrowinninng and gold Smelting,Tailing dam and Detoxification plant. The flowsheet consists two crushing circuits each consists a primary, secondary and tertiary stage crusher that produces a crushed ore product, which is then conveyed to feed the grinding unit. Grinding unit is configured in two single stage mills with cyclone classification to confine the particle size reduction within requirement range. Grinding unit consist circuit discharges ore slurry through desanding screen to thickening unit; screen removes trash material from overflow slurry. Flowsheet of thickener and reagent unit utilizes flocculent chemicals to increase/enhances settling rate of solid in grounded ore slurry for gold and silver leaching process. Leaching circuit uses sodium cyanide to extract gold. In the pulp procedure, activated carbon and gold from the ore are utilized to adsorb the recovered gold from solution in carbon. The carbon is gathered and processed in the elution circuit, which separates the carbon and gold, after the CIP circuit. While the gold is extracted from solution during the electrowinning process, the carbon is renewed and utilized again in the CIP circuit. To create gold Dore bars, the stripped and electrowonted gold is melted in a gold chamber. For the purposes of final deposition, recovering decant water, and the detoxifying process, process tailg ravitate to a tailing storage facility. Process tails solution detoxified in cyanide destruction plant before being discharged to the environment. Finally, Production process of each unit described with block and process flowsheet.
Grindability and Comminution Energy Consumption in Case of Midroc (Lega Dembi and Sakaro) Gold Ore
(Addis Ababa University, 2023-09) Yonas Hordofa; Bogale Tadasse (PhD)
The purpose of this study was to investigate the impact of mill speed and grinding time on the grindability and comminution of gold ores from the Lega Dembi and Sakaro deposits. A batch mill internal diameter of 200 mm and volume (5 dm3) was used for the experiment. The study employed a two-factor approach, considering different grinding times (10 and 15 minutes) and three fractions of mill critical speed (40%, 50%, and 60%).The experiment involved dividing the feed into five equal portions across eleven size class fractions ranging from 4mm to -75μm, with a √2-series interval. A total of ten kilograms of material, divided into one-kilogram portions, were used for the experiment. The objective of maintaining a critical speed below or equal to 50% was to minimize energy consumption during the milling process. The study aimed to assess both the grindability and energy consumption of the two deposits. The results of the study indicated that the rate of breakage increased with grinding time rather than mill speed. For the Lega Dembi deposit, at 40%, 50%, 60% speed and 15 minutes grinding time, the amounts of desired particle size classes produced were 251.7 grams, 264 grams, and 263 grams for the different mill speeds. Similarly, for the Sakaro deposit, the amounts produced were 251.7 grams, 232.6 grams, and 256 grams for the respective mill speeds. Based on the obtained results, the study concluded that mill speed had no significant effect on the grindability of the gold ores from both mining sites, as grinding times.
Grindibility and breakage characteristics of Sekota iron ore deposit in Wag-Himra Zone, Northern Ethiopia
(Addis Ababa University, 2023-06) Yohanes Belachew; Bogale Tadesse (PhD); Birtukan Yenealem (Co-Advisor)
In this study, the influence of mill rotation speed and grinding time were investigated on Sekota iron ore grinding process in a batch mill with length 150 mm and inner diameter 150 mm. The particle size distribution of the feed was carried out by an electric sieve and the bulk feed was classified into three samples to perform the grinding test. Three distinct iron ore feed size fractions between -335mm to +0.71mm, -0.71mm to +0.15mm and -3.35 to -0.075mm separated by a series of √2 gaps were prepared. The fractions were milled at different grinding times (5, 15, 25, 35, 45 and 60 min) at 450 rpm and at different mill rotational speeds (250, 300, 350, 450 and 550 rpm) at 25 min. The mill rotation speed and grinding time affect the energy consumption, the desired grind size and the P80 of the feed size fraction. When grinding time increased from 5 to 60 min, the percentage of cumulative mass of target size increased from 8.5 to 31.1%, from 7.1 to 22.8% and from 10.6 to 26% for coarse, fine and mixed iron ore size fractions, respectively. Likewise, a significant amount of the desired grind size is produced as the grinding speed increases until the maximum critical speed is reached. For all feed size fractions, the required grind size amount (-0.075 mm) is not achieved at grinding times from 5 min to 60 min and at maximum mill rotation speed (450 rpm). The product size distribution of the three iron ore feed size fractions were also affected as the grinding time and the mill rotation speed increased from 5 to 60 min and 250 rpm to the maximum speed (450 rpm). The P80 values of all feed size fraction generally decreased both milling time and mill speed are increased from 5 to 60min and 250 to 450 rpm respectively. Unlike the P80, the energy consumption of the ball mill increases significantly as the mill speed and grinding time increase from 250 to 450 rpm and from 5 to 60 minutes respectively.
Evaluation of the Nature of Porosity in Carbonate Rock Of Hamanlei Formation, Ogaden Basin, Ethiopia: Implications For Prediction of Reservoir Quality
(Addis Ababa University, 2023-06) Yimam Ali; Solomon Kassa (PhD)
The Ogaden basin is the largest sedimentary basin in Ethiopia having 350,000 km2 areal coverage. It is also the most studied sedimentary basin in Ethiopia. Nonetheless, the amount of data gathered from this baisn is not enough to better comprehend the petroleum system of the basin. The Hamanlei carbonate rock in the basin makes good reservoir rock. The nature of this reservoir rock is complex owing to various factors. Despite detail studies were conducted to understand the reservoir property, particularly core and wireline log study, further studies are needed for better characterization of this reservoir rock. To further characterize the reservoir property, i.e. porosity, of this rock and prediction for reservoir quality, petrographic and image analysis were performed. The outcome of this study provides valuable insights into the mineralogy and texture of the studied rocks. Furthermore, it highlights the importance of understanding the different pore types that enables to better interpret the reservoir quality and potential flow characteristics of the studied rocks. Generally, the porosity value of the reservoir rock is too small which is caused by the dominant proportion of matrix and cement
Process Mineralogy of Laga Dambi Gold Ore, Oromiya, Southern Ethiopia
(2023-09) Walkite Alemayehu; Bogale Tadesse (PhD)
To understand gold ore processing, the important mineralogical properties of Laga Dambi gold ore was described qualitatively and quantitatively. This is required to determine the parameters of gold ore grade, ore composition (elemental and mineralogical), and concentration of any valuable minerals, nature and concentration of minerals detrimental to the processing. One 75mm x50mm size polished thin section was supplied from each sample and was examined by conventional transmitted and reflected light polarizing microscope to determine the distribution of gold in the samples. Sub samples (500g) of each ore type were ground to 1mm and the heavy minerals concentrated using gold pan. The concentrates were submitted for mineralogical analysis to determine the distribution and particle size of gold in the samples. XRD, XRF and Geochemical analysis was carried out for gold mineralogical characterization and its concentration determination. From the data obtained it can be concluded that, gold is the most valuable element in the ore. The samples are all well graded and show excellent liberation. Sulphide mineralization is coarse within all the samples The pyrrhotite is the most abundant sulphide in all the samples, with the exception of Mse T5 where it is second in abundance to pyrite.Samples OP T1 and MSe T5 containing the highest concentrations of sulphide minerals. The gangue in the samples is dominated by crystalline quartz and mica (muscovite, biotite and phlogopite). Gold was identified in all but the Op T1 head sample. Pyrroyite, pyrite, and chalcopyrite are the most frequent interfering minerals that either consume cyanide or oxygen, or both, and adversely affect the rate or extent of gold leaching. From mineralogical point of view liberation size of gold can be determined to be120μm. from XRD and XRF techniques quartz was predominant gangue minerals in all types. Ankerite, dolomite and plagioclase feldspar were also present in minor constituent. All samples contained low levels of base metals, with the possible exception of OP T3, which are not likely to hinder processing mechanism.
Application of Lapidary Technology for Sustainable Gemstone Resource Development In Ethiopia
(2023-09) Tsion Shumalem; Abubeker Yimam (PhD); Aselefech Mitiku (Ms.)(Co-Advisor)
Ethiopia is renowned for its mineral abundance and more than 40 varieties of gemstone resources. With the artisanal and small scale miners controlling the production, the phase of the gemstone path abruptly came to a halt, with just a few rough dealers and a few gem cutters remaining, resulting in a very low economic benefit from the sector. The purpose of this study is to look into the function of lapidary technology for sustainable gemstone resource development in Ethiopia. The paper focuses on identifying the country‘s gemstone resource development challenges, the stages of the lapidary process and colored gemstone value chains, lapidary technology and the economic and social importance of lapidary technology in creating various jewelry and decorations using the new technology. In this study, interviews, literature reviews, lapidary work on a selected sample (gemstone from Wegel Tena, Amhara Regional State, Ethiopia), and an economic analysis of rough and value-added gems are conducted to analyze the role of lapidary technology on the industry. Furthermore, it is designed to comprehend the stages of the supply process and gem value chain, as well as to investigate the economic and social ramifications of modern lapidary technology on the development of sustainable gemstone resources. The impact of lapidary on increasing the value of rough gemstones is enormous. An economic analysis made of agate, crystal quartz, obsidian, jasper, and opal found that there is an increase between 400 and 70,000 folds due to the effect of lapidary technology and value added on the rough gemstone. The study’s findings revealed that the fragmented character of the gemstone business attributed to its lag behind other mining industries. Moreover, the study indicated that the gemstone industry in Ethiopia lacks technology, finance, lapidary expertise and a controlled market system. Enabling legislation should be put in place to ensure that the necessary economic return from gemstone resources is attained in order to protect the business and support a successful gemstone cutting and polishing industry.
Effect of Particle Size on Coal Cleaning by Froth Flotation Method in Didaye Woreda, Wolaita Zone
(2023-06) Tiruye Kassaw; Bogale Tadesse (PhD); Guta Legesse (PhD) (Co-Advisor)
The aim of this study is to investigate the effect of particle size on the efficiency of coal cleaning process by froth flotation. Coal cleaning is an important process, which involves removing ash, and other impurities from coal to improve its quality for energy and industrial use. Froth flotation is a widely used method for coal cleaning, which relies on the difference in surface properties between the coal particles and the mineral matter. However, the efficiency of froth flotation is greatly affected by the size of coal particles. In this study, four different sizes range of coal particles (-500μm+350πm, -350μm+225μm, -225μm+180μm and-180mμ+100μm) were tested for their ability to float in the froth flotation process. Results showed that the efficiency of coal cleaning was highest for particles ranging from at this particle size -350μm+225μm, while particles above +350μm showed the poorest performance. The results suggest that particle size is a critical factor in the success of coal cleaning by froth flotation, and -350μm+225μm coal particles are more amenable to this process. The findings of this study will help in optimizing the coal cleaning process to improve its efficiency index, combustible recovery and ash rejection.
Reverse Flotation as a Method for Beneficiation of Sekota Iron Ore
(Addis Ababa University, 2023-06) Temesgen Demissie; Abubeker Yimam (PhD)
Upgrading low grade Sekota iron ore to reduce the unwanted minerals and improve the quality is necessary to address these issues, in order to produce an acceptable feed for a steel production facility. The primary aim was to use reverse flotation as a beneficiation method for Sekota iron ore, in order to get a last flotation that meets the desired specifications. This process was divided into three stages: crushing, grinding, and flotation. For each of these stages, such as grinding, dosage of collectors, flotation duration, and procedures were determined. In the laboratory, where the samples were obtained, the ore was ground in a size of -0.074mm, using 250 grams of ore, with varying amounts of anionic oleic acid as the collector, 5mg/ton of activator and 5mg/ton of depressant, and floated with 2.0 g/ton of ethanol frother. The slurry was maintained at 10.5 using NaOH throughout the process. Before conducting any optimization tests on the iron ore flotation process, a laboratory procedure was developed to carry out the reverse flotation of the iron ore. The results showed that following these parameters, the flotation process achieved a final concentrate with a grade of 39.16% iron and an iron recovery of 41.29%. In this study, with varying duration of flotation, the iron grade ranged from 40-45% with an iron recovery of approximately 42%.
Flotation Response of the Kindo Didaye Coal Deposit, Wolaita Zone
(Addis Ababa University, 2023-06) Temesgen Ayisa; Mulugeta Sisay (PhD)
The main objective of the project was to investigate the optimum flotation behavior of the coal.Flotation is an important process, which involves removing ash, and other impurities from coal to improve its quality for energy and industrial use. Froth flotation is a widely used method for coal cleaning, which relies on the difference in surface properties between the coal particles and the mineral matter.However, the efficiency of froth flotation is greatly affected by the size of coal particles. The bulk sample from jaw crusher was milled by cross-bitter miller and coal sample was ready for separation in arranged sieve shakers based on their size. Then,fine powder coal samples were prepared by using different size of sieve shaker arranged as and measured the mass of the feeds of each particle size before the starting of flotation processes.In this study, four different sizes range of coal particles (-500 to +250 μm, -250 to +150 μm,-150 to +125 μm,-125μm to +75μm and -75 μm) were tested for their ability to float in the froth flotation process. Because of natural hydrophobicity of coal, there are a range of chemicals used to further enhance the floatability of coal particles.Results showed that the optimum flotation was highest for particle size und.75μm, while particles above +250μm showed the poorest performance and the same result was seen by the increase of kerosene amount at the same particle size. The results suggest that particle size and the over use of reagents are critical factors in the success of flotation response. The findings of this study will help in optimizing the coal cleaning by flotation increasing the heat value of the coal by avoiding the impurities. So in this flotation experiment the calorific value increases.
Reverse Anionic Flotation for Potential Beneficiation of Sekota Iron Ore, Northern Ethiopia
(Addis Ababa University, 2023-09) Tarekegn Dure; Abubeker Yimam (PhD)
In this project study, hematite ore sample obtained from Sekota area, Northern Ethiopia was used. Main objective of the study is to obtain iron concentrate at possible maximum grade and recovery by using reverse anionic flotation beneficiation method. The effect of oleic acid collector dosage and sieve size fractions were studied and optimized. The chemical and mineralogical characterization of the ore was also determined. Results of chemical analysis using atomic absorption spectroscopy (AAS) showed that the iron ore contains 65.12% Fe2O3 (45.57% Fe). Major gangue minerals were SiO2 (20.62%) and Al2O3 (8.86%) while all other minerals were reported at <1%. Mineralogical descriptions using the X-ray diffraction (XRD) and QEMSCAN BMA showed predominantly hematite and goethite with quartz, kaolinite and clay as gangue minerals while others P and S are in lower amounts. The concentrate 62.96% Fe2O3 with highest grade of 44.07% Fe was obtained with 43.4% Fe recovery in the feed size fraction (−63 μm) adding 3g/t of oleic acid collector. Based on the results obtained from the flotation tests conducted, Sekota iron ore at a sieve size of -75μm and -63μm were able to enhancing both grade and recovery.
Identification of Reservoir Rocks, Properties and Structural Mapping of the Abay Basin in Viewing of Petroleum Exploration
(Addis Ababa University, 2023-06) Seid Endrie; Ketsela Tadesse (PhD); Bisrat Kebede (PhD) (Co-Advisor)
The basins has unique geological characteristics and holds different types of sedimentary rocks, such as sandstones, shales, carbonates, and volcanic rocks. The Abay (Blue Nile) Basin is located in the northwestern part of the country and covers an area of over 63,000 square kilometers. The Abay Basins covers a sizable area of the country. It includes Were Ilu, Mechale, and Legehida, which have notable oil seep exhibits. The contribution of the Upper Sandstone reservoir rock data is gathered from prior researchers and written materials in order to develop a relevant relationship between the types of reservoir rocks and structural mapping of the study area. In order to undertake the experimental tests for this study, samples are gathered from the field and sent to laboratory centers. In the laboratory, the chemical composition, porosity and permeability values of the reservoir rocks are determined using a representative sample that was collected from the study area. Based on the results of the experiments, the reservoir rock for the Abay (Blue Nile) Basin formation is an Upper Sandstone reservoir rock with relatively good porosity and excellent permeability. The Upper Sandstone rocks in the Abay basin have porosity values that range from 32.31 to 34.35% and permeability values that range from 1766 to 2350 mD, which suggests that the reservoir quality is generally very good (porosity)and excellent (permeability). During field work, it was discovered that the following fault systems were dominate in the study area. These includes; east-west (E-W) trending faults, northeast-southwest (NE-SW) trending faults, and northwest-southeast (NW-SE) trending faults. The oil and natural gas can be gathered and stored in reservoirs, the geological features called hydrocarbon traps. The presence of a petroleum system in the Abay Basin is strongly supported by the oil seepage at Were Ilu. The study area is characterized by rough structures, so airborne geophysical surveys are advised rather than ground geophysical surveys; seismic lines are needed for the study of the Abay Basin in order to delineate structural traps, stratigraphic traps, and indicate active faulting in the areas where it is possible for seismic line surveys; the basin requires further study regarding the main hydrocarbon fluids reservoir rocks, the total organic carbon contents of the source rocks and the carbonate reservoir rocks.
Reverse Flotation Potential of Bikilal Iron Ore Deposit: A Project Work on Wollega Area Western Ethiopia
(Addis Ababa University, 2023-06) Samuel Getaneh; Mulugeta Sisay (PhD); Guta Legesse (PhD) (Co-Advisor)
Iron is one of the most abundant rock forming elements, constituting about 5% of the earth’s crust. It is the fourth most abundant element next to oxygen, silicon and aluminum and after aluminum, the most abundant and widely distributed metal. Iron is extracted primarily from iron ores. The iron ores mainly include oxides and hydroxides such as magnetite (Fe3O4), hematite [Fe2O3], goethite [FeO(OH)], and limonite [FeO(OH)_nH2O].The primary gangue mineral in iron ores is quartz. The main problem regarding to beneficiate the Bikilal iron ore deposit are the presence of some deleterious gangue minerals such as Phosphorous, Alumina and silica and lack of advanced separation equipment. The aim of this project work is to indicate that the Bikilal iron ore deposit has naturally low grade iron content which is 41.2%Fe and it can be improved by anionic reverse flotation. The method used to upgrade this ore is first the qualitative and quantitative mineralogical analysis has been determined by atomic absorption spectroscopy (AAS) to know the initial amount of iron in the ore. Based on this information reverse anionic flotation has conducted in a batch flotation cell in two size classes at 75μm and 63μm. Oleic acid has been used as a collector whereas Ethanol used as a Frother. Modifiers such as activators, depressants and pH regulators have also used to promote the efficiency of flotation process. The concentrate of flotation has been analyzed again by (AAS) to evaluate the performance of the selected method. The amount from the concentrate has significantly increased from 41.2%Fe average grade to 62%Fe grade. The recovery of iron have been calculated as 65% for under 63μm and 74.4% for under 75μm.The amount of the concentrate for 63μm was 215g and that of 75μm was 250g. Therefore the recovery of iron from 215g under 63 μm is 65.5%Fe which is better than the recovery from 250g under 75μm that is 74.4%Fe. This project work mainly conducted based on (AAS) analysis results but it is not suffifeint to judge the general mineralogical composition and beneficiation process that should be applied in the Bikilal iron ore deposit. Therefore additional investigations and laboratory analysis such as (XRD), (SEM) and (XRF) are recommended to come up with a more tangible and realistic data. This paper have also discusses in detail about the factors that can affect the flotation performance of the ore and the alternative chemical reagents that can go through the mineralogy of Bikilal iron ore deposit.
Applicability of Gravity Separation Method on The Ashashire Gold Ore Deposit from Benishangul Gumuz Region, Ethiopia
(Addis Ababa University, 2023-06) Misganu Kabeta; Mulugeta Sisay (PhD); Abaynesh Mitiku (Mr.) (Co-Advisor)
The current Project of applicability of gravity separation method for gold ore deposit was conducted in Ashashire locality of Benishangul gumuz region, North western Ethiopia. The purpose of this project is beneficiating the Ashashire gold ore deposit by applying the gravity separation. The Ashashire composites were produced to provide sufficient mass for this study and experiment includes sample preparation, head assay analysis of gold and multi-element, gravity concentration and mineralogical analysis. The study conducted to determine the applicability of gravity separation method by using KC on the Ashashire gold ore deposit. The samples were moderately ground to the standard grind size of P80 - passing 106, 75, 53 μm and this nominal size was selected for the preliminary assessment for Concentration optimization. During the study, a grind optimization was conducted on the composites sample with varying grind size to evaluate the effect of grind size on gold recovery. The gravity testing comprised three-stage concentration by centrifugal knelson concentrator to produce gravity concentrate. High recovery of gold from the gravity concentrates was achieved from the second gravity concentration. Based on the results from laboratory experiments, a grind size of P80 75 μm is selected as optimal size for the ashashire deposit using KC gravity methods. Increasing the grind size from P80 of 75 μm to106 μm decrease recovery rate from 75 % to 54 % or decreasing the grind size from P80 of 75 to 53 μm decrease gold recovery rate to 37%. It was observed that repeat gold head assays varied, indicating the presence of coarse gold particles and uneven gold particle distribution. The native gold grain in the ores is mostly associated with quartz and Fine gold is closely associated with pyrite, forming inclusions and dispersed within pyrite. According to the fire assay, chemical, and mineralogical analyzes data, only gold and telluride is commercially valuable component in the ores. Presence of 2.13 ppm Te was detected in the composite sample during head assay analysis. The differences between assayed head grades and calculated head grades would indicate that the gold is not evenly distributed within the ore and occurs as localised spots. Gold was identified to occur predominantly in the native form and as Au-Te. The sample subjected to gravity separation assayed about 2.6 g/t Au.
Multistage Hydraulic Fracturing Design for Horizontal Wells in Hilala Gas Field, In the Ogaden Basin, Ethiopia
(Addis Ababa University, 2023-06) Mengistu HaileMariam; Ketsela Tadesse (PhD); Shiferaw Regassa (PhD); Bisrat Kebede (PhD)
The economically viable production of oil and gas is a direct function of the geological properties of reservoir rocks. Among these formation properties, permeability is critical for an effective hydrocarbon flow. The flow of fluids from the reservoir to the wellbore can be restricted due to low permeability or damage around the wellbore. Hydraulic fracturing is applied to stimulate the low permeability formation and bypass damaged formation areas, connecting the reservoir to the wellbore. Recently, the most popular layouts for increased production from low permeability reservoirs have been horizontal wells with numerous transverse fractures. Under various studies conducted, it has been proven that there is a significant commercially recoverable gas reserve in the Ogaden basin of Ethiopia that has been identified for development. Hilala Field is located within this basin, and it is considered for gas development and production through domestic and international gas market arrangements outlined in the recent field development plan. This fracture design study is undertaken for the Adigrat sandstone reservoir in Hilala Gas Field, buried at a depth of 3087-3200m and characterized as a low porosity and low permeability reservoir that requires hydraulic fracturing for its economic gas recovery. The aim of the study is to develop an optimum multiple hydraulic fracturing design for the horizontal wells considering the geology, rock mechanics, fracturing fluid, and proppant. This hydraulic fracture design work is based on the Unified Fracture Design (UFD) and selected extension works. Excel sheet is the main tool for the analytical study. OptiFrac and OptiFracMS software are employed to design and analyze results. This study examined well log data from seven wells, well test and production test results from four wells, and the field development plan for the Hilala Gas Field in the Ogaden basin in South Eastern Ethiopia. Understanding reservoir rock‘s physical, geo-mechanical properties is crucial to the stimulation of hydraulic fracturing. The brittleness Index can be determined from well log and core data. Based on the analysis of the Adigrat reservoir rock‘s geo-mechanical properties, the Adigrat sandstone formation in Hilala gas field has a high Young‘s modulus (51.26 MPa) and a low Poisson‘s ratio (0.21), correlating it to a brittle rock suited for fracture propagation. The calculated average closure stress is 50.45 MPa, and the suitable proppant material is intermediate-strength bauxite proppants. An optimum fracture half-length of 310.6m and a fracture width of 2.25 mm are attainable for a given proppant number of 0.87 for a single fracture. An optimum number of twelve (12) transverse fractures can economically attain a dimensionless productivity index of 6.18 for an available proppant number (Np) of 8.92 for the 0.2 mD permeability reservoir and drainage width of 1000m.
Study on the efficiency of gravity beneficiation method on gold bearing ores from Lega Dambi and Sakkoro deposits by using Laboratory Scale Shaking Table
(Addis Ababa University, 2023-09) Megersa Teku; Alberto Velazquez (Prof.)
This study focuses on the investigation of the efficiency of a gravity separation as pre - concentration for a gold samples taken from Laga dambi openpit, and Sakkorro underground gold mine by using Shaking table concentrator. The bench-scale test work was performed on samples taken from Midroc Lega Dembi gold mine, Ethiopia to provide information on the gravity recoverable gold (GRG) content and the optimum size range for gravity concentration, and gold distribution by using a shaking table concentrator, to determine the efficiency of gravity method as a pre-concentrate by using shaking table. The GRG test was perfom1ed at entire sample passing (P100) through 2000 µm, 710 µm, and 500 µm sieve aperture at first, second and third sages respectively. Fire assay analysis was undertaken to determine the content of gold element in the shaking table products.The results of GRG test have indicated that 17.11% , 19.73% , and 27.44 % of the GRG from the ground ore were recovered into a concentrate at first, second, and third stages respectively. Totally about 64.29 % GRG was recovered into concentrate from three-stage tests for the gold ore samples taken from Lega Dembi and Sakono gold mine. The International standards (I.S) sieves having the following narrowing sieve sizes: 2000µm, 140 µm,1000 µm,710 µm, 500 µm, 355 µm, 250 µm, 150 µm, 75 µm, and pan were selected to conduct size analysis. The cumulative gold distribution obtained from the three stage concentrates size analysis was indicated that an approximately 85%, 69%, and 53% of the available gold was contained at the average size of 112 µm, 200 µm, and 302 µm respectively. However the cumulative GRG distribution shown that only 47.38%, 24.23 %, and 12.96 % of the GRG was recovered into concentrates of shaking table at the mean size of 112 µm, 200 µm, and 302 µm respectively. These indicated that the gravity separation was not effective to pre-concentrate the Lega Dembi, and Sakorro gold ore at relative coarse paiticle sizes by using shaking table concentrator.
Effect of Clay Slimes on Flotation in Case of Dado Coal Deposit, Jimma, South Western Ethiopia
(Addis Ababa University, 2023-09) Abraham Feyisa; Melesse Alemayehu (PhD); Ijara Tesfaye (Mr.) (Co-Advisor)
In Ethiopia, coal mining is a significant economic activity. The existence of clay slimes, which have an impact on the quality and amount of coal, is just one of many difficulties that coal mining activities must overcome. These problems regarding the impact of clay slime on coal flotation were the focus of this study project. Using flotation mixtures containing slime particles and coal particles in the 0.5-0.25 mm, 0.25-0.125 mm, and 0.125-0.063 mm size ranges, batch flotation and flotation rate tests were conducted with the primary goal of examining the impact of slimes on the recovery of coal particles by flotation. The findings of this study suggest that the content of slime particles and coal particle size had a bearing on the influence of sludge particles on the coal flotation recovery. Recovery of coal ash by flotation in all size fractions in the mixed flotation was larger than that of coal granules in each flotation cell when the mass proportion of the slime particles was below 20%. However, when the particle mass ratio of the slime exceeded 20%, the former was lower than the latter. Additionally, as the percentage of slime particles increased, coal particle recovery using flotation across all size fractions dropped. Additionally, it was easier to see how slime particles affected the Recovery via flotation of coarse coal particles.
Value Addition of Ethiopian Gemstones
(2023-06) Mehatebe Gebrewold; Abubeker Yimam (PhD); Aselefech Mitiku (Ms.) (Co-Advisor)
Ethiopia is well recognized for producing gemstones. Numerous high quality gemstone varieties, such as opals, emeralds, sapphires, amazonite, amber, rubies, tourmalines, aquamarines, chrysoprase, peridot, chalcedony, obsidian, agate (scapolite agate), jasper, petrified wood, and various types of quartz, including precious quartz, are the main gemstones mined in the nation. However, the industry continued to generate little appreciable economic advantage because the country mostly exported rough gemstones with no added value. This project study intends to demonstrate the technology needed for adding value to various Ethiopian gemstones and the associated financial advantage. The following measures were taken in order to add value: Sorting the chosen gemstone by specie, selecting clean, color-full, large (excellent size to cut) pieces from the rough collection, cutting, polishing, and ultimately faceting of the chosen gemstone. The value added gemstones are then each given a physical description based on their Color, Clarity, and Cut. Finally, a price estimate has been generated for the gemstones with enhanced value. The project's findings showed that enhancing the value of the rough gemstone might produce earnings of up to 1,610,590 ETB/Kg of Opal, 293,560 ETB/Kg of Crystal Quartz, 213,040 ETB/Kg of Green Obsidian, 48,565 ETB/Kg of Jasper, 43,730 ETB/Kg of Agate and 43,675 ETB/Kg of Black Obsidian. As a result, small-scale gemstone business owners can profit from the high prices of their products and the country can increase the foreign currency revenues from selling the value-added gemstones by adding value to the rough gemstones through the use of relevant technology.
Provenance Controls on Porosity Evolution, Adigrat Sandstone, Ogaden Basin, South East Ethiopia
(Addis Ababa University, 2023-06) Mahamed Hassen; Solomon Kassa (PhD)
The Ogaden basin is the largest sedimentary basin in Ethiopia, with 350,000 km2 of areal coverage. Although it is the most studied region, so far 72 wells have been planned to be drilled in the area, i.e., the number of wells per area covered is 4861 km2. This thesis investigates provenance based on petrography, facies analysis of Adigrat Sandstone in Calub-wells and Hilala-wells in the Ogaden Basin, Ethiopia. A Detailed laboratory petrographic analysis was done on 25 sandstone samples (15 sample from the Calub field wells and 10 sample from the Hilala field wells). Changes in the mineral composition and lithofacies of these sediments over time relate to the tectonic development of the region. When the different grain mineralogies are associated with different source rock types, the signals of at least two distinct sediment source regions emerge. The relative amounts of sand-sized material from the study areas indicate a shift in provenance over time; with the advance of the Calub-wells, a mixed provenance of sedimentary and metamorphic source terrains gave way to a depositional record characterized by sedimentary source rocks. Petrographic and modal composition of the sandstone classification displayed mostly quartz arenite with few subarkosic and sublithic arenite. The modal composition of sandstone revealed that the provenances are craton interior, recycled orogeny, and continental block provenance. From the Qt-F-L tectonic setting plot, all samples fall outside of the tectonic setting field as a result of intense weathering. According to the analyzed data, the porosity of the Adigrat sandstone of the two gas fields is medium therefore the reservoir is good.
Mineralogical Assessment of Ashashire Gold Ore to Investigate Its Beneficiation Potential by Flotation Method, In Benshangul Gumuz Western Ethiopia
(Addis Ababa University, 2023-06) Kiross Haile; Bogale Tadesse (PhD); Kaleb Gebreyes (Mr.) (Co-advisor)
Primary and placer gold deposits are found in the Ashashire area, which is an orogenic gold prospect area. These resources are a source of income for both companies and artisanal gold miners. It is located in the Western Greenstone belt of the Precambrian volcano-sedimentary belt, at Kurmuk Woreda, in the western Ethiopian region of Benshangul Gumuz. The region is near to the Sudanese border and is referred to as Ashashire informally. Gold is the most valuable commodity in the world. Due to the significant study that experts from all around the world have done on the history of gold, namely its birth. Ethiopia is a developing country, but it has not yet reached its full potential. Some claims and exploratory activities claim that Ethiopia is rich in precious metals, including gold, which are processed using incredibly archaic methods in many different regions of the country. As a result, the main objective of this research project is to investigate the mineral makeup of Ashashire gold ore in order to assess its potential for flotation-based beneficiation. The geochemistry was validated by both inductively coupled plasma mass spectrometry and fire assay. The petrographic analysis includes a description of the host rock and ore deposit. The host rock mostly consists of chlorite, carbonate, sericite, and quartz, with minor amounts of greenschist to amphibolite facies metamorphic minerals. Pyrite, pyrrhotite, magnetite, sphalerite, chalcopyrite, galena, and gold are found in the ore after petrographic investigation. According to ore microscopic and geochemical study, gold mineralization has strong spatial connections with alteration traits as carbonitization, silicification, sulfidation, and sercitization. The concentration of gold increases with host rocks that have been sericitized, carbonitized, silicified, and sulfurized. According to the ore geochemical data, the gold deposit contains up to 10.3ppm and is contained in chlorite-sericite-carbonate schist in carbonate-quartz veins. This gold deposit's target region is the Ashashire region. It is possible that gold is precipitated from hydrothermal solutions due to the intense wall rock alteration and the strong relationship between carbonate-quartz veins and gold. Every experimental mineralogical examination conducted by organizations and individuals in Ashashire ore mineralogy produces comparable results. It is not economically feasible to concentrate Ashashire gold for the reported gangue minerals using the flotation method. Due to the possibility of large recovery losses and increased chemical reagent consumption from such gangues. Then, prospective approaches for recovering gold from the Ashashire gold deposit include combining processing technologies like gravity separation, flotation processes, and leaching.
Study on Flotation Response of Coal from Gamo Zone Southern Ethiopia
(Addis Ababa University, 2023-06) Kibru Woldemariam; Abubeker YImam (PhD)
Based on the log results of pits, geophysical results and areal coverage of coal deposits in Gamo zone, Kuccha woreda, it is roughly estimated to have 744,174.96 tons of coal. The flotation response of a coal is a critical factor in determining the efficiency of coal beneficiation processes. The study investigated the effects of collector dosage, frother dosage, and particle size on the flotation response of Gamo area coal in a 3-liter batch flotation experiment. Kerosene was used as the collector and n-octanol as the frother. Full factorial Design was applied to investigate the effect of collector dosage (10ml, 20ml), frother dosage (2ml, 6ml) and particle size (-250 μm +125μm -125 μm) on the process of flotation using Design expert® 6 software, which shows the significant influence on the value of yield and recovery. The result showed that the optimum condition for the process was 18.3ml, 4.7ml and -125 μm which resulted in 81.7% yield,90% combustible matter recovery and 37.5% flotation efficiency index. The findings suggest that careful optimization of reagent dosages and particle size can significantly improve the flotation response of Gamo area coals, with potential applications in coal beneficiation processes.

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