Spelling suggestions: "subject:"[een] MINERAL SAND"" "subject:"[enn] MINERAL SAND""
1 |
[en] AEROSOL CHARACTERIZATION IN A REGION WITH HIGH CONCENTRATION OF MINERAL SANDS. / [pt] CARACTERIZAÇÃO DE AEROSSÓIS EM UMA REGIÃO RICA EM AREIAS MONAZÍTICAS.ZOYNE PEDRERO ZAYAS 17 June 2003 (has links)
[pt] No litoral brasileiro, do Rio Grande do Norte até Rio de
Janeiro, se encontram os mais importantes depósitos de
areias monazíticas No litoral do Município de São Francisco
de Itabapoana, no estado de Rio de Janeiro, encontram-se
importantes jazidas de areias monazíticas, e na vila de
Buena, situada neste município, se encontra uma usina de
beneficiamento de areias monazíticas. Nela são obtidos
concentrados de ilmenita, zirconita, rutilo e monazita
utilizando separadores letrostáticos, eletromagnéticos e
gravimétricos (espirais, planos inclinados e mesas
vivratorias). Com o objetivo de caracterizar a exposição
dos habitantes desta vila a partículas de poeira na fração
respirável foram coletadas amostras de aerossóis usando
impactadores em cascata, amostradores portáteis com ciclone
e amostras de bioindicadores. As amostras foram analisadas
pelo método PIXE (Particle Induced X ray Emission) para
determinação da concentração dos metais e do MMAD (Mass
Median Aerodinamic Diameter), por PDMS (Plasma Desorption
Mass Spectrometry) para identificação dos compostos
presentes. As amostras de aerossóis coletadas com
amostradores portáteis e de bioindicadores foram analisadas
para determinação da concentração dos isótopos das séries
naturais do tório e urânio. Os resultados indicam que os
habitantes estão expostos a partículas contendo metais na
fração respirável do aerossol geradas por fontes tanto
antropogênicas , quanto naturais. As amostras de
bioindicadores indicam os habitantes da vila tem estado
expostos a radionuclídeos das séries naturais do tório e
urânio nos últimos 15 anos. / [en] The main deposit of mineral sands in Brasil occur from the
Rio Grande do Norte State to Rio de Janeiro State. The main
commercial deposit is located in Buena, a village at São
Francisco de Itabapoana, Rio de Janeiro State. In buena
there is a plant that process minerals sands to obtain
ilmenite, zirconite, rutile and monazite concentrates. This
plant belongs to the Industrias Nucleares Brasileiras
(INB). Close to this plant there is a small village.
Aerosols samples were collected using cascade impactors and
cyclones in order to characterize human exposure to
airborne particles in the respirable fraction. Lichens
samples were also collected.
The samples were analyzed by PIXE (Particle Induced X ray
Emission) for determination of elemental mass concentration
and MMAD (Mass Median Aerodynamic Diameter). PDMS (Plasma
Desorption Mass Spectrometry) allows the identification of
the chemicals compounds present in the samples. The
concentrations of radionuclides from the thorium and
uranium natural series were also determined. The results
show that the inhabitants were espoused to airborne
particles in the respirable fraction of aerosols from
natural and anthropogenic sources. The lichens samples
indicate that the inhabitants have been exposed to
radionuclides from the thorium and uranium natural series
since last 15 years.
|
2 |
Risk and reliability of exploration methods used to define a heavy mineral sand deposit in Kwa-Zulu Natal, South AfricaBoekhoud, Karina 26 June 2012 (has links)
The objective of the treatise is to review the sample methodology and the exploration methods at a heavy mineral sands deposit. The level of confidence and the risk associated with the resource calculations will be established based on the sample methodology. Two drilling methods used at Hillendale are compared statistically and visually. It is clear from the comparison that the Wallis Aircore (WAC) method is significantly better than the Reverse Circulation (RCN) method. This is evident also when comparing results of the two methods with the recovery from the mined out areas. The WAC drilling method reduces the risk of downhole contamination due to the change in the drilling method allowing air to be forced back in an inner tube after the sample is collected compared to the air blowout of the RCN method. The WAC method reduces the variability introduced in the sample collection as compared to the RCN method. The average calculated value (for total heavy minerals (THM) and Ilmenite) of the global population for the two methods is similar. The reduced variability in the sample population of the WAC method results in a lower population being required for the confidence interval about the mean at a 95% confidence level. The lower number of required samples results in a lowering of project cost. Blockmodels created from the two drilling methods are compared statistically (mode, median, standard deviation). The global mean of the input data compares well with the global mean of the estimated blockmodel. In reconciling the resource blockmodels with actual production data, the variability as introduced by the RCN drilling method is clear. The WAC drilling information produces a blockmodel with an acceptable level of variance (deviation of the geological model from the actual values obtained during mining) as defined by Hillendale mine management of less than 10%. This is determined by reconciling the estimated geological blockmodel for a specific mined out area against the actual tonnages and plant recovery values achieved in the same area. Ultimately, because the drill spacing is standard in the mining operation under study, the required confidence in the mean might not be achieved by either of the two drilling methods in certain portions of the mine, but the results from the WAC method will be closer to the reality than the RCN method with the same number of drillholes. Three main risks are identified in the sample methodology; they have a high probability to occur or have a high cost impact. The risk inherent in sampling and analysis is the most important of the risks identified in this study. The risk can be effectively reduced by implementing a quality assurance and quality control programme (QAQC). The other high risks are introduced by the drilling method and drillhole spacing. The risk can be reduced by continuous improvement and keeping up to date with new developments in the industry such as improved drilling techniques and by improved knowledge of the ore-body. The knowledge will help in understanding the risk - It may become clear in the text how this can reduce the risk. In conclusion, the improvement and implementation of systems such as improved drilling technique and quality assurance and quality control programmes enables one to establish an acceptable confidence level in the resource calculation as well as reducing the inherent risk to an acceptable level for future decisions. Copyright / Dissertation (MSc)--University of Pretoria, 2012. / Geology / unrestricted
|
Page generated in 0.0389 seconds