This research was undertaken to study the suitable physico-chemical conditions for the selective recovery of gold and silver from simulated thiosulfate leach liquors containing copper, gold or silver, ammonia and thiosulfate using three anion exchange resins. In particular, the effect of chemical variables such as thiosulfate, cupric ion and ammonia concentrations and the solution potential of the system on the batch loading of silver and gold onto the resins have been investigated in detail. Pourbaix diagrams have been constructed to understand the stability of this complex system under various Eh and pH conditions. The experimental results indicate that IRA-400 resin has the highest capacity for both silver and gold compared to IRA-68 and IRA-94. All the three resins investigated are not selective to silver and gold over copper. The elution studies using ammonium thiosulfate solutions have revealed that selective elution of silver from copper is not possible, while some selectivity can be achieved between gold and copper. (Abstract shortened with permission of author.)

The world's proven reserves of crude oil will be depleted in 42 years at the current rate of consumption. Oil refiners are under considerable economic and environmental pressure to improve the efficiency of refining and the quality and definition of products. Statistical and fundamental models are extensively used to more accurately model the important refinery processes such as Fluidised Catalytic Cracking (FCC). A major problem with the fundamental approach is that FCC feedstocks are by definition heavy petroleum fractions, and as such constitute highly complex mixtures of aromatic and aliphatic hydrocarbons. Gas chromatography (GC) analysis of heavy petroleum fractions reveals a broad 'hump' of unresolved compounds termed an Unresolved Complex Mixture (UCM) of hydrocarbons. Conventional instrumental techniques alone are unable to elucidate the composition of UCMs, they are simply too complex. Oxidative degradation of UCMs has already been used with some success to selectively oxidise aliphatic and aromatic UCMs to reveal some of the structures incorporated in UCMs from various natural and anthropogenic sources. Ruthenium tetroxide (RUO4) attacks aromatic rings at the ipso-carbon of aromatic moieties. Unsubstituted aromatic carbon is oxidised to CO2 whereas substituents are preserved as carboxylic acids. "Retro-structural analysis" involves reconstruction of the products of oxidation to reveal the original molecule or 'average' molecule. However, previous studies have highlighted problems with the recovery of products from die oxidation of hydroaromatic compounds. Hydroaromatic compounds contain an alicyclic ring attached to an aromatic ring e.g. tetralin. This study presents evidence that (theoretically) data from RUO4 oxidation FCC feedstocks can make a significant improvement to the accuracy of FCC modelling at BP Amoco. RUO4 oxidation and work-up procedures were developed further in an attempt to overcome problems with 'losses' of oxidation products from hydroaromatic compounds, including an improved carbon dioxide trap. Several novel hydroaromatic compounds and a diaromatic compound proposed in a previous study as being 'average' UCM components were synthesised and fully characterised by GC, GCMS, FTIR and NMR spectroscopy. The compounds synthesised were 6-cyclohexyltetralin, l-(3'- methylbutyl)7-cyclohexyltetralin, 1-n-nonyl-7-cyclohexyltetralin and 1-/n-nonyl-7- cyclohexylnaphthalene. RUO4 oxidation of the synthetic compounds and commercial tetralin revealed that while losses of between 70 and 50% of the expected water soluble dicarboxylic acids are observed, these losses can be at least partially accounted for by the 'over oxidation' of carboxylic acids to produce smaller carboxylic acids. For example, the RUO4 oxidation of tetralin produces 1,6-hexanedioic acid as a major product but significant amounts of 1,5-pentanedioic acid is observed along with trace amounts of 1,4- butanedioic acid. Smaller acids are likely to be undetected or lost as butyl esters during the work-up. Where 2-n-nonyl-1,6-hexanedioic acid was produced, decanoic and nonanoic acid as well as 1,5- pentanedioic acid and 1,4-butanedioic acid were observed corresponding to oxidation of the 2- position on the dicarboxylic acid. The three major products from RUO4 oxidation of ln-nonyl-7-cyclohexylnaphthalene were partially oxidised compounds including 2-(l-oxo-n-decane)-4-cyclohexylbenzoic acid, showing that the oxidation of diaromatic compounds in UCMs gives more complex oxidation products. This is consistent with previous studies where diaromatic UCMs were oxidised to give a more complex 'oxidised UCM' rather than simple carboxylic acids. The observation of monocarboxylic acids in oxidation products from the alicyclic portion of a hydroaromatic compound has not previously been reported. This represents a new source of monocarboxylic acids in the RUO4 oxidation products of UCMs and should be taken into account when oxidising UCMs likely to contain a significant proportion of hydroaromatic structures, such as hydrotreated FCC feedstocks. The synthesis and oxidation of di-substituted teiralins has increased the understanding of RuG4 oxidation products from UCMs and consequently furthered the use of RUO4 as a potentially useftjl tool in the elucidation of FCC feedstock compositions and other aromatic UCMs.

Every business faces risks and the first step in managing risk is making an inventory of the risks that a business faces and getting measure of the exposure to each risk. There are several risks that can affect an oil refinery. Generally recognized risks related to refineries are as follows: crude oil price, crack spread, marketing margin, sales volume, exchange rate, costs, credit and counterparty risk, and hazard risk. In this thesis, among these risk factors, major market price variables, such as crude oil price and crack spread, are regarded as risks or simulation variables; some of the other risks, such as marketing margin, utilization rate, and energy cost, are treated as uncertainties; the others are excluded or fixed. This thesis develops a hypothetical refinery financial model that reasonably approximates real models encountered in practice. To measure the impacts of risk factors on the refinery, three criteria are adopted; present value of net income for ten years, present value of net cash flow, and return on capital employed (ROCE). For sensitivity analysis, five variables are selected: crude oil price, crack spread, marketing margin, utilization rate, and energy cost. In order to measure the risk exposure of an oil refinery, this thesis makes Monte Carlo simulation 10,000 times, by using @RISK software. / Energy and Earth Resources / text

No description available.

No description available.

The first order ternary interaction parameters of bismuth in molten copper containing either iron, arsenic or antimony have been evaluated using a pseudo equilibrium process at temperatures between 1398 K and 1473 K. The isopiestic distribution technique developed in this investigation yielded the following results: εFeBi=[(1.11x10⁶)/T]- 754 εAsBi=[(4.4x10⁴)/T]-24 εSbBi=-11 These results, coupled with other activity data, have been used to calculate the isoactivity curves for each constituent in the copper rich corner of each ternary system. The basis for the ternary interactions associated with εFeBi, εAsBi and εSbBi are also discussed.

The equilibrium distribution measurements of As, Sb and Bi between molten copper and white metal and molten copper and matte were conducted to evaluate the activity coefficients of these impurity elements in copper smelting matte. The experimental results were analyzed through comparison and reconciliation with data in the literature. The following equations, based on a liquid standard state, were obtained for ᵞAs, ᵞSb and ᵞBi in white metal coexisting with copper phase at 1,150-1,200°C. Ln ᵞAs = -2.49 + 0.186 NAs; Ln ᵞSb = -1.23 + 23.5 NSb; Ln ᵞBi = 3.01 + 14.0 NBi where Ni represents the mole fraction of the element Bi in white metal. Analysis of the data demonstrated that a major factor in removing As, Sb and Bi in matte during smelting involves careful control of the sulfur pressure, ie. matte's sulfur content, the optimum matte composition's being those that approach the Cu₂S-FeS pseudo binary.

No description available.

No description available.

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