6 research outputs found
Comminution Characteristics of Lithium Bearing Mica Ores From Different Devices
This paper highlights on the comminution and to the lesser extent liberation properties of two greisen-type lithium bearing-mica ores (L1, L2) subjected to different breakage devices; cone crusher (CC), roller crusher (RC), rotor beater mill (RBM) and a screen mill (SM). The particle size distributions (PSD) of the products from each device were evaluated to search for an appropriate PSD model using Gates-Gaudin-Schuhmann (GGS) and Rosin-Rammler (RR) functions. To determine an appropriate function, coefficients of determination (R2 ) were used as a criterion. Due to budget constraint, only products from rotor beater mill (RBM) were examined for mineral liberation by an automated scanning electron microscope (SEM) technique. It was found that RBM, RC and SM products were better described by the RR model than the GGS model with higher R2 values of 0.97 to 1.0. However, cone crusher products for L1 were better described by GSS model, while that for L2 were better described by RR model. In terms of the spread of size distribution as indicated by RR model parameters, RC products were more uniformly distributed compared to those from other devices, for both ores. Also the RBM products were more scattered than those from other devices. The results indicate that the composition of individual ores affected the comminution products PSDs as different PSD model parameters were obtained for samples comminuted by same devices. The modal mineralogy indicated that both ores are rich in quartz, topaz, zinnwaldite and muscovite. Furthermore, the result indicates that, for both ores, the zinnwaldite phase is more enriched in the fraction < 250 µm. Moreover, better liberation of zinnwaldite is observed for L1 compared to L2. This could be explained by differences of the two ores in three aspects; the nature of mineral association, reduction ratio of the fractions analysed and the spread of the size distribution
Investigation of old waste dump composition of lean gold-bearing ores from the Golden Pride Project (GPP) mining operation in Nzega district, Tanzania
The search for alternative sources of useful minerals is a pressing issue. One such possible source is the processing of lean gold-bearing ores, which previously did not seem feasible to exploit for subsoil users, leading to their disposal in off-balance ore dumps. Processing these resources becomes economically viable as gold prices rise and processing technologies improve over time. This paper presents the elemental and mineralogical composition of lean gold-bearing ore dumps from the Golden Pride Project (GPP) mining operation in Tanzania’s Lihendo district. This area contains an old dump of lean gold-bearing ores, weighing approximately 1.4 million tons. Extracting valuable components from lean mineral raw materials is a current priority. Sampling was conducted to study the dumps. Boreholes were drilled to a depth of 1 m, covering a total sampling area of 20 ha; 18 samples, each averaging 3 kg in weight, were collected. The results of X-ray fluorescence analysis (XRF) indicated the presence of Fe, S, Si, Ca, Ca, Mn, Cu, Al, Cr, Ti, As, and Ag in the collected samples. X-ray diffraction (XRD) analysis revealed that the main minerals in the dumps are muscovite, kaolinite, quartz, montimorillonite, and goethite. The average gold grade in the selected samples is 0.72 g/t. Studies of the grain-size distribution and gold distribution by grain-size classes after ore grinding demonstrated that the majority of gold (74%) is in the −75 μm class. In the initial mineral material of the dumps, the share of the +30-50 mm grain-size class is 81%. The paper proposes potential methods for processing lean dumps of gold-bearing ores. One such methods involves crushing the dump material, separating the −75 μm class, and subjecting it to direct leaching or leaching using “carbon-in-pulp” technique. Heap leaching appears to be the most promising method for extracting gold from such dumps in terms of technical and economic feasibility. Positive experience has been reported in applying this process to ores of similar mineralogical type
Analysis of technical efficiency in smallholder dairy production in Tanga City, Tanzania
Eastern and Southern Africa Journal of Agricultural Economics & Development Vol. 9 (2012), pp. 74-86This paper investigates the technical efficiency of smallholder dairy farmers in
Tanga City using the Stochastic Production Frontier Function (SPFF) approach.
The study estimates the levels of Technical Efficiency (TE) of smallholder dairy
farmers. This was a cross sectional research design which used simple random
sampling technique to select the subjects into the study. A total of 80 smallholder
dairy farmers were interviewed using semi–structured questionnaire. Data analysis
techniques included collating field data and decomposing it into descriptive
statistics and estimating the stochastic production frontier model for dairy keepers
in Tanga City. The overall Technical Efficiency (TE) of smallholder dairy farmers in
Tanga City was 89.7%. The study found that labour, feeds, veterinary services and
capital stock increase the ability of producing more milk which in turn boosts milk
productivity and thereby raises milk supply. However, labour cost was found to
have a negative effect on the TE while feeds veterinary services and capital stock had
positive effect. Therefore, this study recommends reduction of labour costs through
the use of improved simple mechanical technologies that reduce drudgery in pasture
cutting and hence increase labour productivity