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Investigation of the leaching of the platinum group metal concentrate in hydrochloric acid solution by chlorineAsamoah- Bekoe, Yaw January 2016 (has links)
The dissolution of platinum-group metals (PGMs) requires a high chloride ion
concentration in an acidic solution and a suitable oxidant. At Impala Platinum Refinery,
the concentrate is leached in a hydrochloric acid solution using chlorine gas as the
oxidant. The goal of this leaching step is a total dissolution of the PGMs and gold. The
silver precipitates as silver chloride. The efficiency of this stage is crucial for the
performance of the precious metals refinery.
The aim of this project is to investigate the factors that influence the efficiency of the
PGM leaching operation and to model for the results obtained. In order to investigate
and evaluate the total dissolution of the PGt;~; in HClICl2 leach system, it is necessary
to establish the effective conditions for the dissolution of chlorine gas in hydrochloric
acid solution. The results showed that the solubility of chlorine gas increases with an
increase in the acid concentration and chlorine gas concentration but decreases as the
temperature increases. The HCI solution is almost saturated with chlorine after about
50 minutes. The chlorine mass' msfer coefficient is dependent on the temperature, the
stirrer speed, the concentration of the HCI solution and that of the chlorine.
[Abbreviated abstract. Open document to view full version] / GR 2016
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Vacuum refining of copperOzberk, Engin. January 1980 (has links)
No description available.
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Biosorption by industrial microbial biomassMay, Harriet A. January 1984 (has links)
No description available.
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Biosorption by industrial microbial biomassMay, Harriet A. January 1984 (has links)
No description available.
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Breaching the platinum cost curve: cost curve selection and development, marginal production survivalSchmitz, Peter January 2019 (has links)
A research report submitted in partial fulfilment of the requirements for the degree of Masters of Science in Engineering to the Faculty of Engineering and the Built
Environment, University of the Witwatersrand, Johannesburg, 2019 / The report considers survival mechanisms used by Platinum Group Metal
(PGM) producers over the period 2008 to 2017 when mining operations
were considered marginal for an extended period. Various methods to
build cost curves for the PGM industry were tested, with co-product
costing, inclusive of sustaining capital, selected. Industry cost curves
were developed for the period, showing that a significant portion of
producers were marginal from 2014 to 2017, with Impala lease area,
Rustenburg mines and Lonmin marginal for more than two years in that
period. Survival was achieved through cross-subsidisation, utilising cash
reserves, deferring sustaining capital, re-capitalisation and working capital
management, before ultimately restructuring through sale or closure took
place. While industry cost curves were effective at indicating operational
competitiveness in a particular year, a mechanism to indicate relative
financial strength (ability to sustain this position) needs to be sought. / TL (2020)
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Vacuum refining of copperOzberk, Engin. January 1980 (has links)
No description available.
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On Aspects Relating To A Hydrochlorination Facility For The Processing Of Refinery Precious Metal Residue Materials.Fortmann, Noel Alwin. January 1990 (has links)
A project report submitted to the Faculty of Engineering,
University of the Witwatersrand, Johannesburg in partial
fulfilment of the requirements for the Degree of Master
of Science in Engineering. / A hydrochlorination facility was developed for tile
processing of refinery precious metal residue materials
on the laboratory and pilot scale. Hazard
elements were identified and evaluated using an Event
Tree Analysis. An exponential technique was applied
to estimate the cost of the proposed production hydrochlorination
facility. The estimated cost was R120 000.
The Expected Present Value Ratio was +190 which indicated
satisfactory project economics.
The reactor material for the pilot scale unit was
selected using a weighted values quantitative material
selection procedure. Stainless steel Type 316L and
Type 310 were selected. Failure of the Type 516L
reactor occurred after 40 hours service. The mode of
failure was extensive surface scaling which was attributed
to the hydrogen chloride, sulphide gases and
1 000 °c operating envirornment.
Subject to certain provisions it would be feasible to
commission a safe and profitable production hydrochlorination
facility. The consumable reactor concept was
based on its replacement after 40 hours service. This
was justifiable because of the high value of the material
and the saving in down-stream processing costs. / Andrew Chakane 2018
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Comparison of the grain-refining characteristics of zirconium and calcium on magnesiumFreeman, Elgeva Roy. January 1948 (has links)
Call number: LD2668 .T4 1948 F74 / Master of Science
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Two phase, gas liquid flow through a vertical channelPouliquen, Benoît. January 1985 (has links)
No description available.
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Electrochemical processes within the slimes layer of lead anodes during Betts electrorefiningGonzález Domínguez, José Alberto January 1991 (has links)
In the Betts process for lead electrorefining the noble impurities originally present in the bullion form a strong and adherent layer of slimes. Within this layer the established ionic concentration gradients can lead to secondary reactions. The following processes were analyzed from a thermodynamic perspective: (A) hydrolysis of the acid (B) precipitation of secondary products (C) reaction of noble compounds.
The nature of the concentration gradients within the slimes layer and related secondary processes was studied by using transient electrochemical techniques which include: (A) current interruption, (B) AC impedance, and (C) a variation of SACV (Small Amplitude Cyclic Voltammetry). These studies were complemented by: (A) physico-chemical data on electrolyte properties, (B) "insitu" and "industrially recovered" slimes electrolyte compositions, (C) SEM and X-ray diffraction analysis of the slimes layer. For comparison purposes the electrochemical behaviour of "pure" Pb electrodes was also studied.
Upon current interruption the anodic overpotential decays, first abruptly, (as the uncompensated ohmic drop disappears) and then slowly (due to the presence of a back E.M.F. created by ionic concentration gradients that decay slowly). Current interruption measurements showed that: (A) concentration gradients exist across the slimes layer, (B) inner solution potentials within the slimes layer can be larger than those measured from reference electrodes located in the bulk electrolyte, (C) secondary products can shift the inner solution potential to negative values which reverse upon re-dissolution and (D) ionic diffusion is seen upon current interruption but it is complex and difficult to model due to the presence of processes that can support the passage of internal currents.
The anodic polarization components were obtained by analyzing the potential and current dependance upon application of a small amplitude sinusoidal waveform. This dependance was found to be linear in the low overpotential region (< 250mV). Thus, upon subtraction of the uncompensated ohmic drop, the remaining polarization is due to the "apparent" ohmic drop of the slimes electrolyte and to liquid junction and concentration overpotentials. These components are directly linked to the electrolysis conditions and to the slimes layer structure. Furthermore, the ratio of these components can be used to obtain the point at which the precipitation of secondary products starts. Changes in this ratio can also be related to the anodic effects caused by the presence of addition agents.
AC impedance measurements performed in the presence of a net Faradaic current showed that the impedance increases uniformly as the slimes layer thickens up to the point at which noble impurities start to react. Three electrical analogue models were used to describe the impedance spectra.
A steady-state mathematical model that predicts concentration and potential gradients across the slimes layer was developed. Only when a position dependent eddy diffusion term was incorporated in the numerical solution, were reasonable local ionic concentrations and overpotentials obtained. / Applied Science, Faculty of / Materials Engineering, Department of / Graduate
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