Thesis (MTech (Chemical Engineering))--Cape Technikon, Cape Town, 2002 / The activation of green '"'Smartie"" coke (a mixture of medium temperature pitch and waxy oil coke) was investigated in a laboratory scale fluidised bed (FB) and a rotary kiln as function of (1) heat treatment temperature (HIT) and (2) heat treatment time (HTt). Activation in the FB was more effective (in terms of surface area development) and the product obtained from this type of reactor had a larger percentage of mesopores than the products from the rotary kiln. It was possible to produce a product with an iodine number equal to 745 mg iodine per gram carbon. The study revealed that it is possible to tune the pore structure of "Smartie" coke derived activated carbons by changing the activation device and systematically changing the activation conditions. It was possible to obtain products ranging from a predominantly microporous structure to products with a predominantly mesoporous structure. Unfortunately, in comparison to commercially available activated carbons, the total surface areas were still too low and it will be necessary to perform further investigations focused on increasing the total surface areas. The gold adsorption tests performed on the activated carbon compared well to those of activated carbon currently in use in the gold industry.

Thesis (Masters Degree (Chemical Engineering)) - Cape Technikon, Cape Town, 1996 / With the increasing awareness ofpreserving the environment, the need for other lixiviants in leaching processes has escalated. The investigation for lixiviants, especially for gold, has entailed mostly the halogen group. From halogens, iodine forms the most stable gold complex. The aim ofthis study was to investigate the adsorption characteristics of gold-iodide onto a coconut shell based activated carbon. In the first part of this study, the factors influencing the adsorption kinetics and equilibrium were investigated. Mixing experiments and interruption tests indicated clearly that the principal adsorption mechanism is by first order film diffusion. When the initial gold concentration was changed, the adsorption kinetics and equilibrium decrease viith an increase in gold concentration. This is due to the shielding effect by the adsorbed gold as it is partly reduced on the carbon surface. The concentration of iodide increased the adsorption kinetics and equilibrium. The increase in concentration of iodine leads to an increase in concentration ofthe principal oxidising agent, tri-iodide, thereby decreasing the adsorption parameters as the gold gets redissolved from the carbon surface. Furthermore, iodine and trio-iodide adsorbs competitively, thereby decreasing the rate ofadsorption ofthe gold complex. This is further iterated by experiments where the carbon was pre-treated v.ith a iodine/iodide solution. In acidic solutions, none, or a minimal amount ofthe gold is red11ced on the carbon surface, adsorption is only in the complex form, while in a alkaline solution, the gold is partly adsorbed and partly reduced. In the second section, the adsorption is approached from a basic electrochemical perspective. Here, depending on the pH ofthe solution, it is shown that the potential ofthe solution dictates the species of iodine and gold-iodide complex in solution, it affects the adsorption characteristics ofthe activated carbon.

Thesis (MTech (Chemical Engineering)--Cape Technikon, Cape Town,1996 / Acetylene Black IACB) IS a pure form of carbon which is used in the battery, plastics, printing and rubber industries. It is extensively used in the battery industry to absorb electrolyte and to lower the electrical resistance of dry cell batteries. It is the attempt of this thesis, to investigate the surface characteristics '---------._-- -,- ...• -...•--- .. ------.. _.. --- "'- and structure of ACB by using it as an adsorbent for cyanide complexes, in particular gold cyanide. The thesis is predominantly aimed at identifying the mechanism of metal cyanide adsorption onto ACB, viz. ion exchange and/or physical adsorption. In order to quantify the mechanism of adsorption, comparative studies with other adsorbents currently used in the mining industry, such as activated carbon, were conducted. These studies revealed various similarities in the metal adsorption process between ACB and activated carbon, thus indicating physical adsorption rather than ion exchange to be the dominant mechanism for metal adsorption from solution. The rate of metal adsorption onto acetylene black was relatively fast compared to activated carbon. Furthermore, adsorption profiles revealed that intraparticle diffusion was negligible when a metal was adsorbed onto ACB from solution. This indicates that acetylene black has a predominantly amorphous structure, although X-ray diffractrometry indicates a certain degree of graphitisation associated with ACB. The small surface area of ACB, together with the lack of intraparticle diffusion, resulted in the rapid attainment of the equilibrium metal loading on ACB. Moreover, this equilibrium metal loading was far less than that of activated carbon and ionexchange resin. While pH, temperature and strong oxidizing agents had a marked effect on the adsorption profile of metal cyanides onto ACB, the effect of oxygen enrichment and organic solvents was negligible. Furthermore, the adsorption of gold onto ACB is best explained by a Freundlich-type isotherm. As is the case with activated carbon and ion exchange resin, gold is eluted from ACB by a NaOH solution. It was also found that the elution efficiency is influenced by a change in temperature. Changes in operating variables in the production of ACB had an effect on the absorption stiffness of the product. Both an increase in acetylene feed rate and operating temperature reduced the absorption stiffness of the product.

Thesis (Masters Degree(Chemical Engineering))--Cape Peninsula University of Technology, 2008 / ABSTRACT Carbon-in-pulp (CIP) technology is firmly entrenched in the mining sector due to numerous advances in the last few decades. CIP technology recovers complexed gold in solution from slurry streams by contacting the pulp with carbon and separating the two by screening. The carbon-in-leach (CIL) process, where the pulp contains free cyanide, is closely related to CIP. Both these processes, especially CIL, are complex and are governed by a number of interacting unit processes. The overall process efficiency is dependant on a large number of variables, making the process difficult to optimize. This study uses simple adsorption and leaching rate equations in order to predict dynamic CIL/CIP plant performance under varying operating conditions. This will assist plant metallurgists to achieve optimum efficiency, highlight plant sensitivity to certain variables and will ultimately result in proactive process control. Various assumptions were made in order to keep the modeling considerations as simple and realistic as possible. The process was assumed to have linear kinetic and equilibrium operation. The process was simulated using Simulink in Matlab. Variables are solved on a time step basis by Matlab’s built in optimization algorithms. Simulation results illustrated that the use of simple leaching and adsorption rate expressions are effective for investigating dynamic plant behavior under changing operating conditions.

Made available in DSpace on 2014-06-11T19:30:10Z (GMT). No. of bitstreams: 0 Previous issue date: 2008-12-08Bitstream added on 2014-06-13T18:40:02Z : No. of bitstreams: 1 arceferrufino_gla_me_guara.pdf: 1056072 bytes, checksum: 1cac7a1cd9ce6c0468bceb4898770311 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / O dióxido de carbono (CO2) é um importante gás de efeito estufa. No entanto, um aumento gradual ameaça substancialmente o clima. Um dos principais desafios do planejamento ambiental é identificar um modelo que vincule todos os fatores do ciclo de carbono, ou seja, oceano – ecossistema terrestre – emissão antropogênica – atmosfera. Princípios básicos de Termodinâmica podem ser aplicados em uma modelagem estatística com bases em séries históricas para obter concentrações de CO2 na atmosfera, possibilitando a construção de cenários para uma melhor tomada de decisões. Por este motivo, foi desenvolvido no trabalho um modelo que interliga todos os fatores do ciclo de carbono, focalizando em quatro zonas térmicas ou climáticas (Boreal, Temperada, Tropical, Polar), para cálculos de armazenamento de CO2 atmosférico. Os resultados mostram que no ano 2100 se atingirá uma concentração de CO2 quatro vezes maior do que antes do período pré-industrial. A zona temperada emite quase a metade de dióxido de carbono à atmosfera na atualidade; para o ano 2100, essa emissão aumentará a quinze vezes mais que a zona tropical. A China será responsável em uma proporção de vinte quatro a onze com relação aos Estados Unidos. A estabilização das concentrações de CO2 na atmosfera será obtida quando as emissões de dióxido de carbono antropogênico tiverem uma diminuição de mais do que trinta e quatro por cento para o ano 2100 na zona temperada. / Carbon dioxide (CO2) is the most important greenhouse gas. A gradual increase on its atmospheric concentration threatens significantly the climate. One of the main challenges of environment planning is to identify a model that connects all factors that determine the carbon cycle, that is, ocean – terrestrial ecosystem – anthropogenic emissions – atmosphere. Basic thermodynamic principles can be applied in a statistical modeling with historic time series to obtain atmospheric CO2 concentration, creating the possibility of construction of scenarios that will help decision making. A model that links all carbon cycle factors was developed in this dissertation work, focusing in four thermal of climatic zones (Boreal, Temperate, Tropical, and Polar) for calculations of atmospheric CO2 storage. Results show that in 2100, the atmospheric CO2 concentration will reach a value four times higher than that of the pre-industrial period. The temperate zone already emits almost half of the carbon dioxide to the atmosphere; by 2100, this emission will increase 15 times more than that corresponding to the tropical zone. China will be responsible for emissions in a proportion of 24 to 11 in comparison to that of the United States. Stabilization of CO2 concentrations in the atmosphere will be obtained when the anthropogenic carbon dioxide emissions attain a decrease of at least 34% in 2100 in the temperate zone.

No description available.

No description available.

No description available.

No description available.

Made available in DSpace on 2018-08-01T21:58:47Z (GMT). No. of bitstreams: 1 tese_10597_Dissertação Tamires FINAL 08042017.pdf: 3045708 bytes, checksum: 346790de110160baf3a5382b4013c028 (MD5) Previous issue date: 2017-02-20 / O petróleo ainda continua sendo a maior fonte de energia não renovável do planeta. No seu estado bruto tem pouca utilidade. No entanto, seus derivados apresentam alto valor econômico. Nas etapas de processamento primário do petróleo alguns compostos de ocorrência natural são indesejáveis, como os ácidos naftênicos, resinas, asfaltenos, compostos sulfurados e metálicos. O poder corrosivo dos ácidos naftênicos preocupa as indústrias petrolíferas devido ao prejuízo causado nas tubulações e refinarias. Estudos recentes indicam que uma parcela desses ácidos quando submetidos a elevadas temperaturas (>280°C) pode sofrer reações de descarboxilação e degradação térmica, originando dióxido de carbono (CO2) e ácidos de cadeias menores como produtos de degradação. Os ácidos de cadeias menores juntamente com os ácidos naftênicos que se mantiveram preservados são corrosivos e o CO2 ao entrar em contato com água forma o ácido carbônico (H2CO3), podendo contribuir nas taxas de corrosão nos equipamentos do refino. Assim, o presente trabalho consistiu no desenvolvimento de uma metodologia para quantificação online do CO2 liberado no processo de destilação de petróleo. A metodologia desenvolvida foi baseada na técnica de microcromatografia gasosa. Os dados quantitativos de concentração de CO2 gerados pela microcromatografia foram relacionados com os valores de temperaturas de destilação, obtendo-se assim uma variação na concentração de CO2 de acordo com a temperatura de destilação do óleo. Com os resultados obtidos observou-se que para todos os petróleos destilados houve uma tendência na formação do gás CO2 partir de temperaturas superiores a 200°C. Na tentativa de elucidar a possível origem deste gás, supôs um mecanismo de descarboxilação para tais ácidos