Doctoral Degrees (Chemical Engineering)
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- ItemThe adsorption and elution of Pt-, Pd- and Au cyanide using activated carbon(Stellenbosch : Stellenbosch University, 2015-03) Snyders, Cornelius Albert; Bradshaw, S. M.; Akdogan, G.; Stellenbosch University. Faculty of Engineering. Dept. of Process Engineering.ENGLISH ABSTRACT: In order to exploit lower grade and complex platinum group metal resources, cheaper and more efficient alternatives to the conventional mill-float-smelt-refine route are being sought. Leaching of platinum and palladium with cyanide has been proposed a number of times as a promising precious group metals (PGM) process option, and although platinum extractions are problematic, progress into the understanding of cyanide leaching of PGM containing ore and concentrate has been made. The platinum and palladium leaching will typically take place at elevated temperatures, which can range from 55°C on heaps to 180°C in autoclaves, with a better degree of leaching occurring with higher temperatures. Although this process for Pt and Pd extraction is a promising process option, research regarding the feasibility of the subsequent upgrading and recovery of the pregnant PGM leach solution, however, has been lacking. Since the carrier-phase extraction of gold using activated carbon offers significant advantages over other processes in terms of simplicity, the high pre-concentration factor, rapid phase separation, and relatively low capital and operating costs, activated carbon was deemed the most suitable sorbent for a Pt and Pd adsorption and stripping process. Very little is published on the adsorption of PGM cyanides onto activated carbon and when the effect of impurities such as base metals and thiocyanate together with a suitable elution method, are considered, no information could be found in the open literature. This study was launched and in general it was found that the activated carbon process does seem to be a viable process consideration for the upgrading of PGMs in a cyanide leach stream. Adsorption rates for dilute PGM solutions (0.15mg/L Pt, 0.38 mg/L Pd, 0.1 mg/L Au) in a stirred vessel indicated a high rate of adsorption within the first 60 minutes (giving more than 98% recovery of precious metals). A comparison of the Pt isotherm (25°C) to Au isotherms from literature indicated a similar loading capacity, while that of Pd was found to be significantly lower. In common with most diffusion controlled processes, an increase in the adsorption rate of platinum, palladium and gold cyanide with an increase in temperature was observed, while experiments with consecutive contacts of the PGM cyanide solution onto the activated carbon revealed that with an increase in temperature, the amount of PGMs that were adsorbed, decreased with each loading. In the absence of free cyanide and base metals, it was found that after 4 consecutive contacts, 99% of the total amount of platinum and palladium adsorbed at 25°C, compared to 85% of the platinum and 83% of the palladium at 50°C. No difference could be seen between the adsorption of gold cyanide at 25 and 50°C after 4 contacts. It has also been established that the detrimental effect of free cyanide on the adsorption of PGMs will increase as the temperature increases. The detrimental effect of the presence of Cu and Ni was found to depend on the amount of these base metals adsorbed, which in turn will depend on the cyanide concentration and the solution temperature. Adsorption of Pt and Pd has been found to be significantly more affected by temperature, cyanide and base metals than the adsorption of gold and needs to be carefully taken into consideration with the design of a PGM adsorption circuit to ensure sufficient Pt and Pd recovery. It is therefore highly likely that an activated carbon recovery process for Pt and Pd cyanide will not be as robust as the gold CIS (carbon-in-solution) process, which is considered to be one of its main advantages. The feasibility of eluting platinum and palladium cyanide complexes from activated carbon was investigated. It was found that platinum and palladium elute from activated carbon almost to completion in 4 to 5 bed volumes (BV) at 80°C, while the elution of gold at this temperature is slow, with a significant amount of gold (≈ 55 %) still to be eluted after 16 bed volumes. An increase in Pt and Pd elution kinetics was demonstrated with an increase in temperature with 99% recovery achieved at 4 BVs with an elution temperature of 95°C. Cyanide pre-treatment has been found to have a large influence on PGM elution. The effect of the NaCN concentration shows an increase in the recovery of Pt, Pd and Au as the cyanide increases from 0 to 2 %, after which the recovery starts decreasing again as the NaCN concentration increases from 2 to 4%. The NaOH concentration was also found to affect the PGM recovery and at 0% NaCN, an increase in the recovery is seen, while at a higher cyanide concentration (2 and 3% NaCN) a decrease in the PGM recovery occurs when the NaOH concentration is increased from 0.22% to 1.65%. A general decrease in Pt, Pd and Au recovery was seen as the ionic strength of the elution water increased and is consistent with literature on Au elution. The effect of a hydrochloric acid pre-treatment, which forms part of the process to remove calcium build-up from the activated carbon, was investigated, and for all the cases the Pt and Pd recovery increased when an acid pre-treatment was performed, compared to no acid pre-treatment. In none of the cases did any of the Pt, Pd or Au elute with the acid or the following rinsing water. The acid pre-treatment performed at 70°C removed a significant 64% to 75% of the Ni present and an additional 9.1% to 10.5% in the following rinsing water step. In the presence of copper cyanide, the elution order has been found to be copper, palladium, platinum and gold, which is the opposite order of adsorption preference. The cyanide pre-treatment has also been found to have a major influence on the elution of Cu and can be explained by the difference in the absorbance strength between the different copper cyanide complexes. The presence of Cu did not have a negative effect on the elution of the PGMs at strong pre-treatment (2% NaCN and 0.55% NaOH) conditions, but at weak pre-treatment conditions (0% NaCN) the recovery of Pt and Pd was reduced by between 10 and 18% after 5 BVs when Cu was present. The presence of 100 mg/L KSCN salt added to the leach solution during the adsorption stage, reduces the elution recovery of the PGMs at 4 BVs from 90% for Pt and Pd, when not present, to approximately 70% when present. The addition of the additional K+ ions reduced the recovery by less that 4% at 4 BV, which indicates that the possible formation of a PGM bonding with thiocyanate ([Pt(SCN)4]2- and [Pd(SCN)4]2-), which adsorb onto carbon, but doesn’t adsorb with water, cannot be ruled out completely. A maximum amount of 0.15% for Pt, 0.28% Pd and 0.6% Au was found to report to the pre-treatment solution at 25°C. For higher pre-treatment temperatures, the amount of Pt and Pd reporting to the pre-treatment solution increased significantly to approximately 8% at 80°C, while the increase in gold was marginal to 0.8% at 80°C. For the higher loading on the activated carbon (7000 mg/kg Pt and Pd), which is expected to be a better representation of plant conditions, 0.07% Pt, 0.11% Pd and 0.12% Au reported to the pre-treatment solution. The PGMs reporting to the pre-treatment solution is attributed to the distribution of the PGMs on the carbon particle, and even though very small, a certain amount of these PGMs would readily desorb or wash off the carbon. It has thus been established here that the stripping of adsorbed platinum cyanide complexes from activated carbon consists of a two step batch process, which involves the pre-treatment of the metal-loaded activated carbon with a relatively strong sodium cyanide and sodium hydroxide solution, prior to the elution step with de-ionized water at 80°C. Through the development of a mathematical model to describe this process, it was found that the rate of release of the platinum ions is governed by the amount of platinum and sodium on the activated carbon and the concentrations of these ions in the bulk of the liquid. This is mathematically described by a modified Freundlich isotherm equation and the mass transfer diffusion equation. The dependency of the platinum elution rate on the sodium concentration on the activated carbon, as suggested by gold related literature (Van Der Merwe and Van Deventer, 1990, Stange, 1990), is confirmed. Furthermore it has been found that the rate of platinum elution interchangeably depends on the equilibrium of the Pt ions at the carbon-liquid interface and the mass transfer of these Pt ions from the interface to the bulk liquid. As both of these rate-limiting factors were found to depend on the sodium concentration, the dominant platinum elution rate limiting factor shifts as the sodium concentrations change as the elution progresses. Four main time periods are used to simplify and to describe this process. The benefits of fundamentally understanding this process can ultimately lead to improved elution, better process control, shorter elution times, smaller elution columns or assist in the development of a continuous elution process.
- ItemThe adsorption characteristics of precious and base metals on four different ion-exchange resins(Stellenbosch : Stellenbosch University, 2000-12) Els, Ellis Raymond; Lorenzen, L.; Aldrich, C.; Stellenbosch University. Faculty of Engineering. Dept. of Process Engineering.ENGLISH ABSTRACT: Adsorption tests were conducted with four different ion-exchange resins to determine the equilibrium adsorption of a range of precious and base metals. The adsorption characteristics were determined for synthetic single metal, as well as for multicomponent and base metal solutions. The effect of the el- concentration on the equilibrium adsorption was established for three different Hel concentrations in the above solutions. From the ion-exchange characteristics determined, a selective adsorption sequence is proposed for the separation of precious and base metals. Pure platinum, palladium and gold were dissolved in aqua regia and diluted to 2000 ppm (as metal) in 4M Hel. Ruthenium, rhodium and iridium were dissolved from pure salts in Hel. A 2000 ppm base metal solution was prepared by dissolving all the required components, including precious metals, to match an in-plant industrial basemetals solution composition. For each precious metal the equilibrium adsorption was determined for a couple of solution concentrations. Data points for adsorption curves were established by varying the amount of resin added to the test solution of a specific concentration. The equilibrium solution concentrations were determined by Iep analysis after 24 hours of exposure, using the bottle-roll technique. The experimental results obtained indicate a possible process route for the separation of precious metals with ion-exchange resin. The XAD7 resin is highly selective for gold from mixed solutions containing precious and base metals. It is also evident that, with the gold removed from the solution, the A22 resin adsorbs only palladium. IR200 resin adsorbs only the base metals from the solution. With all other precious metals removed from the solution (platinum and ruthenium must be extracted by other means), iridium can be adsorbed from the solution by IRA900 resin which is highly selective for iridium over rhodium. For all of the anion resins, XAD7, IRA900, and A22, the chloride concentration of the solution did not have a big effect on the adsorption capacity. However, the adsorption of base metals on IR200 is sensitive to chloride concentration, with a rapid reduction in adsorption at higher chloride concentrations. Statistical models were developed for the adsorption of each of the precious metals, as well as for the base metal solution. All adsorption data, obtained for a resin (typically 250 equilibrium data points), was used in the development of the model. The SPSS statistical software package was used to develop linear regression models. The interaction between all the input parameters, e.g. the interaction of gold and chloride ions, was modelled by specifying the product of the gold and the chloride concentrations as an input variable. The variables that determine the adsorption quantities were identified. High solution concentrations of the target adsorption component increase the adsorption quantity. It has been established that a higher platinum concentration increases the adsorption quantity of gold on XAD7 resin. However, the adsorption quantity is reduced at higher ruthenium concentrations. The adsorption quantity of iridium on IRA900 is reduced with increased rhodium concentration. The adsorption quantity of palladium on A22 is increased by the presence of rhodium and decreased by larger concentrations of iridium and platinum. The adsorption of base metals on IR200 is decreased at higher acid concentrations. Higher concentrations of gold in the base metal solution also decrease the adsorption quantity of base metals. The model predicted adsorption of each component compares well with the actual measured values. In batch adsorption tests the counter ion is not removed from the resin. The resin capacity for a specific ion concentration could therefore not be determined. As such, the adsorption models are only valid for the initial part of the ion-exchange process. The effect of kinetics on the adsorption was not determined.
- ItemAdsorptive separations in the production of neutral wine alcohol(Stellenbosch : Stellenbosch University, 2002-03) Goliath, Elroy Mario; Cloete, F. L. D.; Stellenbosch University. Faculty of Engineering. Dept. of Process Engineering.ENGLISH ABSTRACT: This study describes the design, construction, complete industrialisation and operation of a dual bed vacuum swing adsorption (VSA) demonstration plant, which operates at atmospheric and sub-atmospheric conditions. All design objectives as set out initially were met. The plant removes contaminants such as methanol and water from neutral wine spirit. Neutral wine spirit is a key component of various local and international spirituous products which include liqueurs, gin, vodka, fortified wines and brandy. Neutral wine spirit can chemically be described as the azeotropic mixture of ethanol and water, which occurs at an ethanol content of 96.4 vol. %. Methanol is naturally present in all products from the vine. Fermentation and distillation concentrate methanol even more, and due to physical and chemical characteristics, its separation consumes as much as 45 % of total production costs. Neutral wine spirit is produced by the proven technology of continuous atmospheric distillation. Continuous improvement of the distillation process is limited due to the physical constraints of an old facility, but also due to previous design philosophies and approaches. The VSA plant consists of two adsorbers, packed to a total height of 1.71 m and a diameter of 0.4 m. Adsorption took place at 100 °C and regeneration at the same bed temperature with purified nitrogen gas at 170 °C and a vacuum of 17 kPa (abs). Experiments were divided into Group I and Group II experiments. Group I investigated the ability to separate methanol and water from the azeotrope and to which efficiency it occurred. It consisted of 120 adsorption cycles of 5 minutes each and 60 samples were drawn for analyses. Breakthrough was not allowed to occur. The azeotropic feed was consistently dehydrated to a water content < 0.05 wt %, while methanol was reduced to < 4 mg/100mLAA. The type of 3A molecular sieve (MS 564 CS) was specifically selected to ensure analytic as well as organoleptic compliance with the product specification. Molecular sieve 4A was removed due to organoleptic problems with the product. Group" experiments were performed in the format of a sensitivity analysis. The effects of various process parameters on the methanol breakthrough curves were individually assessed. Eighteen experiments were performed over a period of 8 days, with 86 samples drawn. The duration of an adsorption cycle was 30 minutes, allowing methanol breakthrough to occur. Water was preferentially adsorbed. Negative methanol bed loadings during high water loadings confirmed that water was able to displace methanol molecules. In the presence of water, molecular sieve 3A was capable of adsorbing 0.6 mg methanol/100mLAA, while in the absence of water with synthetically dosed methanol, molecular sieve 3A achieved a maximum loading of 12.3 mg methanol/100mLAA. The latter corresponded with a maximum methanol feed content of 1118 mg/100mLAA. In general, quicker breakthrough occurred at higher flow rates and feed concentrations. Continuous breakthrough caused bed contamination and a 24-hour thermal regeneration was performed following experiment 12. The feed flow rate was increased from the theoretical 50 f/hr to 70 f/hr without any additional capital layout. Selected process conditions were found to be effective in continuously separating methanol from ethanol. Depending on the strategy of integration, profitability studies shows a Return on Investment of between 110.1% - 220.8% for the adsorption project. Adsorption is superior to distillation in the separation of methanol. Due to the level of innovation involved, it is recommended that the contents of this study remain confidential and patent protection is to be extended. This dissertation speaks to both the wine making as well as the chemical engineering fraternity. It seeks to provide credibility to both parties, by clarifying the unknown issues fundamental to the respective disciplines.
- ItemAdvancing Lignocellulosic Biorefineries through Co-Production of Hemicellulosic Biopolymers and Bioenergy(Stellenbosch : Stellenbosch University, 2022-04) Mihiretu, Gezahegn Teklu; Görgens, Johann Ferdinand; Chimphango, Annie Fabian Abel; Stellenbosch University. Faculty of Engineering. Dept. of Process Engineering.ENGLISH SUMMARY: This research project was conceived in the context of advancing a lignocellulosic biorefinery for co-production of xylan biopolymers, bioethanol and electricity from two agro-industrial materials, namely sugarcane residues (SCT) and aspen wood (AW). The research was primarily designed to include two full-fledged experimental studies and one techno-economic case study. Accordingly, two biomass pretreatment approaches, namely: microwave-assisted pressurised hot water (MWA-PHW) and alkalinised steam explosion pretreatment (ASEPT) methods were experimentally investigated for their effect on the extraction of xylan from SCT and AW. Extraction experiments (via MWAPHW and ASEPT) were conducted by varying temperatures between 165 – 205 ℃ and retention times 3 - 22 min at test points identified using Central Composite Design (CCD) as response surface methodology (RSM). Pretreatment conditions were intended for a dual purpose: maximizing xylan extraction yield while simultaneously enhancing cellulose digestibility. Experimental results on xylan yield and cellulose digestibility were analysed using ANOVA method to establish optimal conditions for significantly enhanced values. Accordingly, under the MWA-PHW method, maximum xylan yields of 66 and 50%, and highest cellulose digestibility of 78 and 74%, were respectively attained for AW at (195℃, 20 min) and SCT at (195 ℃, 15 min). Whereas maximum xylan yields of 51 and 24%, and highest cellulose digestibility of 92 and 81%, were attained for SCT and AW respectively, following their pretreatment under ASEPT at (204 ℃, 10 min). Under both methods, the xylan extracts were predominantly non-monomeric with insignificant formation of degradation products. This strongly suggested both MWA-PHW and ASEPT were viable approaches for xylan extraction purposes. ANOVA results also revealed that temperature was the dominant factor influencing the xylan yield and cellulose digestibility. The techno-economic case study was aimed at evaluating the economic viability of the biorefinery for co-production of xylan biopolymers, bioethanol and electricity (i.e. main-case scenario, MCS) against two benchmark processes, i.e. Base-case (BCS) and Intermediate-case (ICS) scenarios, where only bioethanol and electricity are produced from sugarcane residues (Basis: daily capacity of 1000 tons of dry biomass subjected to ASEPT condition of 204 ℃ and 10 min). The study results showed that co-production of xylan biopolymers substantially improved the economic performance of the main biorefinery case (i.e. MCS) by lowering the selling price of ethanol against higher values under the benchmark processes. A minimum hemicellulose selling price (MHSP) of 809 USD/ton of xylan co-product was determined by fixing ethanol selling price at 0.70 USD/L (market price of ethanol in 2019); higher MHSP values certainly lead to further lower prices. Minimum ethanol selling prices (MESP) under the MCS, BCS and ICS were respectively estimated at 0.61, 0.95 and 0.81 USD/L, where the xylan price was assumed at 1000 USD/ton (=> MCS). Even though the economic viability of the main biorefinery case was significantly enhanced with co-production of xylan than without, this multiproduct biorefinery complex was rendered rather energy-intensive as a result of such coproduction scheme where the recovery of xylan biopolymers necessitated substantial thermal and electrical energy demands. From environmental point of view, the coproduction of xylan biopolymers along with bioethanol and electricity was shown to have a positive contribution towards mitigating GHG emissions from fossil sources. The GHG emissions savings under the MCS, BCS and ICS were estimated around 69, 64 and 65% against gasoline as fossil baseline of 90 gCO2eq/MJ (RSB-Global), but there was only marginal difference between the savings under the main biorefinery case and that under the benchmark processes.
- ItemApplication of data analytics and knowledge-based systems in mineral processing(Stellenbosch : Stellenbosch University, 2015-12) Aldrich, Christiaan; Burger, A. J.; Stellenbosch University. Faculty of Engineering. Dept. of Process Engineering.ENGLISH ABSTRACT: This dissertation covers research carried out over the past 20 years in the area of knowledge engineering in mineral processing, specifically with regard to process data as a form of knowledge. This focus on data-driven plant automation includes the acquisition, interpretation and application of data in the development of decision support systems in mineral processing, as well as the development of data analytical methodologies required to accomplish this. The following subthemes have been covered: o Inferential sensors - predominantly the development of computer vision systems for froth flotation and the analysis of particulate systems, but also acoustic sensors and the interpretation of electrochemical noise. My research into inferential sensors has centred on the development of methodologies and algorithms to interpret image data and not the development of hardware, such as camera systems or other types of sensing devices. A major part of this pioneering research has focused on the interpretation of froth flotation images. Instead of attempting to identify individual objects (bubbles) in these images, we have treated the froth images as statistical patterns. These patterns could be interpreted by suitable feature extraction algorithms and models that could relate these features to meaningful process indicators. The novelty and impact of my research in this area can be inferred not only from the corpus of highly cited papers that associated with the technology, but also from the commercialization of the technology. o Exploratory data analysis - Focusing on unsupervised learning, such as applied in data visualization, cluster analysis and feature extraction. In exploratory data analysis, the main issue is attempting to make sense of many measurements of large sets of variables. Standard multivariate statistical methods have their limitations when dealing with complex data, and a significant part of my research has concentrated on the extension of linear methods to their nonlinear variants by use of neural networks or other machine learning approaches. Work in this area has formed the basis of a sizeable number of industrial workshops and has significantly influenced the development of commercial process systems software. o Data-based process modelling - Machine learning approaches to predictive and diagnostic modelling. The construction of process models plays a key role in process systems engineering. This is the case in advanced control systems, where the ability to predict future process states is critical. Models also play an important role in the interpretation of process data and hence the acquisition of insight into process behaviour and mechanisms. Such models can be developed from first principles, but this is costly and with the abundance of process data, often not necessary. The primary impact of this research has been in the development and application of methods to predict process states or key performance indicators for mineral processing systems. o Process monitoring and fault diagnosis - Multivariate statistical process control from a machine learning perspective. Process monitoring and fault diagnosis has evolved into a key element of process control over the last couple of decades, and is currently experiencing strong growth, with commercial application still lagging significantly behind the advances in academia. My research in this area has centred on the application of neural networks, kernel-based systems, random forests and other machine learning methods to extend current approaches. It has led to the foundation of the Anglo American Platinum Centre for Process Monitoring at Stellenbosch University and the development of algorithms that were adopted by industry on a proprietary basis. o Intelligent decision support and advanced control - Fuzzy decision support systems and neurocontrol based on the use of reinforcement learning. Apart from data that are generated by instruments, tacit knowledge in the form of plant operator experience and theoretical knowledge is also a valuable resource that can be used in the automation of plant operations. This is the domain of knowledge-based or expert systems and research was undertaken in the development and application of these systems in mineral processing. The novelty of this research has mainly been in the proof-of-concept studies published in academic journals and conference proceedings. It goes without saying that in my research, I have been assisted by many colleagues, industrial collaborators, students and assistants. The contributions of these co-workers were often critical to the investigations indicated in this thesis and are indicated as such, hopefully without omission, where appropriate.
- ItemThe bio-disposal of lignocellulose substances with activated sludge(Stellenbosch : Stellenbosch University, 2001-03) Qi, Bing Cui; Lorenzen, L.; Aldrich, C.; Stellenbosch University. Faculty of Engineering. Dept. of Process Engineering.ENGLISH ABSTRACT: Lignocellulose is the principal form of biomass in the biosphere and therefore the predominant renewable source in the environment. However, owing to the chemical and structural complexity of lignocellulose substrates, the effective and sustainable utilization of lignocellulose wastes is limited. Many environments where lignocellulose residues are ordinarily stored can be highly acidic (e.g. landfills), and under these circumstances biodegradation of the lignocellulose is slow and unhygienic. Owing to the metabolic activities of the micro-organisms, the initially acidified habitats rapidly undergoes self-neutralization. A number of pathogenic bacteria (coliforms and Salmonella sp.) are present during this slow degradation process and it is therefore imperative to improve the efficiency and hygienic effects of the biodegradation of the lignocellulose. Although the fundamentals of biodegradation of lignocellulose have been widely investigated, many issues still need to be resolved in order to develop commercially viable technology for the exploitation of these waste products. For example, owing to the complex, heterogeneous structure of lignocellulose, the degree of solubilization, modification and conversion of the different components are not clear. Likewise, the overall anaerobic degradation of lignocellulose is not understood well as yet. In this study, the emphasis was on the promotion of solid anaerobic digestion of lignocellulose wastes for environmental beneficiation and waste reutilization. The degradation of lignocellulose in landfill environments was first simulated experimentally. Once the microbial populations and the degradation products of the system were characterized, the promotion of anaerobic digestion by use of activated sludge was studied. This included acidogenic fermentation, as well as recovery of the methanogenic phase. Moreover, special attention was given to the further disposal of humic acids or humic acid bearing leachates formed in the digestive system, since these acids pose a major problem in the digestion of the lingocellulose. With ultrasonication, approximately 50% of the lower molecular weight fraction of humic acids could be decomposed into volatile forms, but the higher molecular weight fraction tended to aggregate into a colloidal form, which could only be removed from the system by making use of ultrasonically assisted adsorption on preformed aluminium hydroxide floes. This was followed by an investigation of the microbial degradation of humic acids and the toxicity of these acids to anaerobic consortia. Further experimental work was conducted to optimize the biological and abiological treatment of lignocellulose in an upflow anaerobic sludge blanket (DASB) reactor fed with glucose substrate. The humic acids could be partially hydrolysed and decomposed by the acid fermentative consortia of the granules in the DASB reactor. Finally, solid mesothermophilic lignocellulose anaerobic digestive sludge can be viewed as a humus-rich hygienic product that can improve the fertility and water-holding capacity of agricultural soil, nourish plants and immobilize heavy metals in the environment as a bioabsorbent.
- ItemCatalytic pyrolysis conversion of lignin from different sources to phenols(Stellenbosch : Stellenbosch University, 2019-04) Naron, David Rangnaan; Gorgens, Johann F.; Tyhoda, Luvuyo; Collard, Francois-XavierENGLISH ABSTRACT: Lignin is a by-product of the paper and pulp industry and the emerging cellulosic ethanol production technologies. Both industries only considered lignin a source of energy to complement the energy needs of their processes. However, the phenolic nature of lignin makes it a valuable renewable resource for sustainable production of chemical products. In the current study, prior to lignin conversion to phenolic chemical products, physico-chemical characterisation of several lignins were conducted using conventional methods namely, wet chemical, gel permeation chromatography (GPC), and Fourier transform infra-red spectroscopy (FTIR). In addition to these methods, a novel analytical pyrolysis method was developed combining thermogravimetric analysis (TGA), thermal desorption (TD), and gas chromatography coupled to mass spectrometry (GC-MS), named as TGA-TD-GC-MS. It was used to analyse and estimate the monomeric phenolic products namely, syringol (S), guaiacol (G) and phenol (H) from lignins. The phenolic monomeric proportions (S/G/H), obtained using the TGA-TD-GC-MS was compared with the ones obtained by thioacidolysis (wet chemical method). The lignin monomeric products obtained by pyrolysis, based on internal calibration, was in the range of 5.5-12.9 wt.%. The ability of the TGA-TD-GC-MS to break several types of bonds gave it the advantage over thioacidolysis, resulting in the production of monomeric phenolic compositions that were more representative of the lignin. A comparison of phenols production from catalytic pyrolysis of lignins of different biomass origin, namely eucalyptus (hardwood) lignin, pine (softwood) lignin, and sugarcane bagasse (herbaceous) lignin was studied using the TGA-TD-GC-MS. The lignins were impregnated with two hydroxides (NaOH and KOH) and two metal oxides (ZnO, and Al2O3), with amounts equivalent to 1 wt.% of the lignin mass, and pyrolysed at the temperature of 600 °C using a heating rate of 10 °C/min. KOH produced the most catalytic effect on the yield of total phenols from sugarcane bagasse (S-S) lignin, leading to the highest increase of +26%, and likewise NaOH for eucalyptus (E-K) lignin (+40%). Syringol yield being the major syringol-type (S-type) phenols reached a record high of 1.8 wt.%, equivalent to 90% increase from E-K lignin, catalysed by NaOH. Additionally, NaOH increased the yield of 4-vinylguaicol-the guaiacol-type (G-type) phenol from E-K lignin up to 2.8 wt.%, equivalent to 39% increase, as compared to the non-catalytic yield. A catalyst screening study was conducted in which twelve catalysts, namely Al2O3, Fe2O3, MoO3, TiO2, Ni/Al2O3-SiO2, CaO, ZnO, MgO, NaOH, CuO, KOH and NiO were each impregnated on three different types of sugarcane bagasse lignins with amounts equivalent to 1 wt.% of the lignin mass. KOH, CaO, and Fe2O3 recorded the highest effects on the total yield of phenols from soda (SD), soda-anthraquinone (SAQ), and steam explosion combined with enzymatic hydrolysis lignins respectively. The increases were 11.2 wt.%, 8.2 wt.%, and 8.6 wt.%, equivalent to + 26%, + 60% and + 43% respectively. Syringol, guaiacol, and 4-vinylguaiacol were the most improved with yield increases ranging from 0.6 to 2.8 wt.%, equivalent to 32-121% from the lignins. Optimisation of phenols was investigated. Pyrolysis was first conducted at analytical scale and then applied in the second stage at bench scale. The results at analytical scale showed that the amounts of KOH required to maximise the yield of phenols (15.3-16.0 wt.%) were in the range of 5-7 wt.%. Analysis of the bio-oil showed that the yields of syringol and guaiacol had their maximum values at 450 °C and 4.5 wt.% KOH content with yield increases of 0.70 wt.% and 0.6 wt.%, which represent 106% and 83% respectively, compared with that of pyrolysis without catalyst. Phenol (the P-type phenol) achieved a maximum at 450 °C and 8.5 wt.% KOH content, with a yield of 0.96 wt.%, corresponding to 141% increase.
- ItemCFD analysis of solid-liquid-gas interactions in flotation vessels(Stellenbosch : Stellenbosch University, 2014-04) Karimi, Mohsen; Akdogan, G.; Bradshaw, S. M.; Stellenbosch University. Faculty of Engineering. Dept. of Process Engineering.ENGLISH ABSTRACT: A Computational Fluid Dynamics (CFD) model was developed for the prediction of flotation rate constants in a stirred flotation tank and validated against experimental data. The model incorporated local, time-varying values of the turbulent flow field into an existing kinetic flotation model based on the Generalised Sutherland Equation to predict the overall flotation rate constant. Simulations were performed for the flotation of various minerals at different operational conditions and the predictions were compared with experimental data. It was found that the CFD-based model yielded improvements in the prediction of flotation rate constant for a range of hydrophobicities, agitation speeds and gas flow rates compared with existing methodologies, which use volume-averaged empirical expressions for flow variables. Moreover, comparing to the available CFD alternatives for the flotation modelling this approach eliminates the need for solving an extra partial differential equation resulting in a more computationally economic model. The model was developed in three stages. In the first, a single-phase model was used to establish the requirements for successful modelling of the velocity components and turbulent properties of water inside flotation tanks. Also, a novel use of the Grid Convergence Index for this application was carried out, which allowed determination of the maximum achievable reduction in numerical uncertainties through systematic grid refinement and adaptation. All subsequent simulations were performed at the optimal discretization level determined in this manner. It was found that the Moving Reference Frames (MRF) method was adequate for representation of the impeller movement when the rotational zone was located close to the impeller, using a time step advance of between 10◦ and 15◦ of impeller rotation. Comparison of the different turbulence models for the single-phase modelling revealed that the standard k-e and Large Eddy Simulation turbulence models both performed equally well and that the computational requirement was lower for the standard k-e model, making it the method of choice. Validation of the methodology was done by comparison with experimental data for two different stirred tanks including an unbaffled mixer and a fully baffled standard Rushton turbine tank. The validation against experimental data showed that the model was capable of predicting the flow pattern, turbulent properties and the generation of trailing vortices. The second stage of modelling used an Eulerian-Eulerian formulation for gasliquid modelling of gas-sparged fully baffled vessels (2.25 l, 10 l and 50 l) using a Rushton turbine. It was determined that the minimum model uncertainty resulting from simulation of the sparger was achieved using a disk sparger with a diameter equal to 40% of the impeller diameter. The only significant interfacial force was found to be the drag force, and this was included in the multiphase methodology. A parametric study on the available formulations for the drag coefficient was performed which showed that the effect of turbulence on the air bubbles can accurately be represented using the proposed model of Lane (Lane, 2006). Validation of the methodology was conducted by comparison of the available experimental gas holdup measurements with the numerical predictions for three different scales of Rushton turbine tanks. The results verified that the application of the designed sparger in conjunction with Lane drag coefficient can yield accurate predictions of the gas-liquid flow inside the flotation tank with the error percentage less than 6%, 13%, and 23% for laboratory, pilot and industrial scale Rushton turbine tanks, respectively. The last stage of this study broadened the Eulerian-Eulerian framework to predict the flotation rate constant. The spatially and temporally varying flow variables were incorporated into an established fundamental flotation model due to Pyke (Pyke, 2004) based on the Generalized Sutherland equation for the flotation rate constant. The computation of the efficiency of the flotation sub-processes also incorporated the turbulent fluctuating flow characteristics. Values of the flotation rate constants were computed and volume-weight averaged for validation against available experimental data. The numerical predictions of the flotation rate constants for quartz particles for a range of particle diameters showed improvements in the predictions when compared with values determined from existing methodologies which use spatially uniform values for the important hydrodynamic variables as obtained from empirical correlations. Further validations of the developed CFD-kinetic model were carried out for the prediction of the flotation rate constants of quartz and galena floating under different hydrophobicities, agitation speeds and gas flow rates. The good agreement between the numerical predictions and experimental data (less than 12% error) confirmed that the new model can be used for the flotation modelling, design and optimization. Considering the limited number of CFD studies for flotation modelling, the main contribution of this work is that it provides a validated and optimised numerical methodology that predicts the flotation macro response (i.e., flotation rate constant) by integrating the significance of the hydrodynamic flow features into the flotation micro-processes. This approach also provides a more economical model when it is compared to the available CFD models for the flotation process. Such an approach opens the possibility of extracting maximum advantage from the computed parameters of the flow field in developing more effective flotation devices.
- ItemCharacterisation and dynamic modelling of the behaviour of platinum group metals in high pressure sulphuric acid/oxygen leaching systems(2012-12) Dorfling, Christie; Bradshaw, S. M.; Akdogan, G.; Stellenbosch University. Faculty of Engineering. Dept. of Process Engineering.ENGLISH ABSTRACT: Sulphuric acid/oxygen pressure leaching is typically employed on Base Metal Refineries (BMRs) to selectively dissolve base metals from platinum group metal (PGM) bearing nickelcopper matte. Optimal operation of this processing step requires an understanding of the system chemistry and the effects of process variables on base metal and PGM leaching behaviour. This project aimed to aid in the development of an improved understanding of the high pressure leaching system. The effects of temperature, pressure, acid concentration, and solid to liquid ratio on the leaching behaviour were determined experimentally using a two litre autoclave. For conditions comparable to that typically used at the Western Platinum Ltd. BMR, changes in the acid concentration had the largest effect on the copper leaching behaviour. Increasing the initial acid concentration from 140 g H2SO4/ℓ to 165 g H2SO4/ℓ resulted in the copper dissolution decreasing from 88.7% to 75.3% on average for the experiments performed at different temperatures (116°C, 130°C) and pressures (7 bar, 9 bar), and with different solids contents (80 g/ℓ, 130 g/ℓ). In the case of the other precious metals (OPMs), temperature was determined to be the process variable with the largest effect on the leaching kinetics. The average percentage rhodium dissolution achieved after seven hours of leaching at different conditions (pressure, acid concentration, and solids content were varied) increased from 58.3% at 116°C to 83.6% at 130°C. Similar effects were observed for ruthenium (96.2% dissolution at 130°C; 79.4% dissolution at 116°C) and iridium (81.8% dissolution at 130°C; 46.9% dissolution at 116°C). The rate of copper leaching was found to be limited by the rate of oxygen transfer from the gaseous phase to the liquid phase, while the remainder of the reactions were chemical reaction limited. The extent of OPM leaching was found to be dependent on the rate and extent of copper leaching. A set of 21 chemical reactions was proposed to describe the leaching behaviour, and the shape factors and reaction rate constants were determined by the method of least squares to minimise the error between the predicted concentrations and the experimental data. Apart from direct base metal leaching reactions, six cationic exchange reactions contribute to the leaching of copper sulphides and nickel sulphides by precipitation of OPM oxides. Three leaching reactions for each of the OPMs (one for sulphide phases, one for metallic phases, and one for oxide phases) resulted in satisfactory modelling of the system behaviour. Activation energies of -26.2 kJ/mol and -5.9 kJ/mol were calculated for the digenite acid leaching reaction and the covellite direct oxidation reaction, respectively, which confirmed that the rates of these reactions were mass transfer limited. The activation energies for the remainder of the base metal leaching reactions exceeded 30 kJ/mol. The activation energies of the reactions accounting for rhodium sulphide leaching, rhodium leaching, and rhodium oxide leaching, were calculated to be 64.2 kJ/mol, 138.5 kJ/mol, and 116.2 kJ/mol, respectively. Similar activation energies were calculated for the respective Ru and Ir leaching reactions. The rate of OPM sulphide leaching was typically an order of magnitude and three orders of magnitude larger than the rate of OPM leaching reactions and OPM oxide leaching reactions, respectively. The autoclave at the Western Platinum Ltd. BMR was modelled assuming a monosized distribution of the feed and approximating the autoclave as four ideal continuously stirred tank reactors. The steady state solution employed the sequential modular approach in MATLAB, while the dynamic simulation involved solving a set of 217 differential equations derived from mass and energy balances simultaneously in MATLAB. The model was used successfully to evaluate the effects that changes in the leaching temperature, leaching pressure, acid feed rate, and solids feed rate have on the extent of base metal and OPM leaching in the autoclave. The optimum operating conditions depend on the flow rates and compositions of the feed streams. A feed stream containing 10.3 wt% solids (825 kg solids/h) and an acid addition rate of 28.6 kg/h were considered as typical operating conditions for model-based analysis. More than 95% copper dissolution and no OPM dissolution were predicted when performing the pressure leaching at a pressure of 8 bar and a temperature of approximately 123°C. Decreasing the pressure resulted in lower copper dissolution when OPM leaching started to occur. Increasing the temperature resulted in reduced copper leaching, while decreasing the temperature resulted in a longer OPM leaching period and hence higher OPM dissolution. Model-based analysis furthermore showed that the relative amounts and relative leaching rates of digenite and covellite significantly influence the percentage copper dissolution achieved when noticeable OPM leaching start to occur.
- ItemCharacterisation of liquid distribution and behaviour within randomly packed columns using electric impedance tomography(Stellenbosch : Stellenbosch University, 2022-04) Lamprecht, Johannes Hendrik; Burger, Andries Jacobus; Stellenbosch University. Faculty of Engineering. Dept. of Process Engineering.ENGLISH SUMMARY: The optimum design of column internals plays a prominent role in the economic viability of distillation setups, due to such internals’ notable contribution to both operating and capital costs. Progression in both our understanding and characterisation of column internals is therefore paramount. Both hydrodynamic and kinetic characterisation methodologies consider the influence of the vapour-liquid interface, whether directly (effective interfacial area) or indirectly (pressure drop and liquid hold-up). Most of the random packing literature, however, focuses on the evaluation of macro parameters (e.g. pressure drop, holdup, flow rates, packing dimensions and fluid physical properties), with notably less attention to the fluid behaviour at a micro level (e.g. droplet formation, distribution and rivulet formation). This limits the fundamental basis of the available models, introducing numerous regressed empirical constants. In other words, while modern random packing designs are strongly influenced by the optimisation of inter-packing droplet and rivulet formation, the available mathematical models lack predictive capabilities of such micro-behaviour. Against this background, and in pursuit of a better understanding of fluid behaviour and distribution in random packing, an Electrical Impedance Tomography (EIT) measurement system was designed and constructed to visualize and quantify liquid distribution behaviour inside randomly packed columns. The EIT system was preferred to conventional X-Ray tomography, due to a) safety, b) cost-effectiveness, and c) simplicity, while it can be utilised for both conducting and non-conducting liquids. The sensor of the EIT system consisted of a stainless-steel wire matrix, installed at a horizontal plane directly below 3m random packing in a 400mm diameter column. It provided 1369 measuring points, with measuring frequencies of 207 Hz and 21 Hz for conductive and non-conductive liquids, respectively. The data were processed using 2-D and 3-D image processing algorithms to enable quantification of individual liquid elements. The individual elements were evaluated based on their reconstructed volume, surface area and sphericity. The experimental characterisations were used to evaluate the liquid distributions inside two types of industrial random packing, FlexiRing® and Intalox® Ultra, at sizes ranges between 1.5” to 2.5”. The evaluations considered various liquid- and vapour loadings using both water and ethylene glycol to vary the liquid physical properties; water being electrically conductive and ethylene glycol being predominantly non-conductive. The presented results show increased element uniformity in favour of the Intalox® Ultra throughout and illustrated the presence of a force-balance transition in the mechanism of liquid hold-up creation. This indicated the transition from conglomerating inter-packing liquid (IPL) streams, towards droplet-creation. The onset of this transition was found distinctly related to the relative velocity profiles and vapour - liquid shear forces of the respective packings. The contribution of droplets in the inter-packing space to the total vapour-liquid interfacial area was also evaluated. The Intalox® Ultra presented ca 17% and 9.4% increase in total reconstructed surface area for the respective 2” and 1.5” equivalent comparisons with FlexiRing® (for the air-water system). This confirmed the applicability of the EIT characterisation system for both hydrodynamic and kinetic prototyping. Several novel contributions were developed in this work. These are: [1] The development of a characterisation methodology based on EIT for better understanding of inter-packing liquid distributions. [2] Novel experimental inter-packing distribution data for IPL element-volumes and -areas and their relation to: i. packing type, ii. liquid and vapour loadings, and iii. liquid physical properties. [3] Presenting the existence of a packing-specific transitional point, based on liquid and vapour loadings, where the mechanism of liquid hold-up changes. This point marks the cross-over between the conglomeration of inter-packing liquid elements into streams, and their break-up/ redistribution into smaller elements. This alludes to a possible increase in interfacial turbulence (decreasing liquid phase resistance to mass transfer) while adding to the understanding of the pressure drop mechanisms in packed columns. [4] Presenting the total IPL element-surface area as a comparative kinetic characterisation parameter for use in prototyping. This is posed to assist in the design of future packings, in finding the optimum packing area and structure to minimize entrainment and maximize efficiency.
- ItemCharacterising the effect of microwave treatment on bio-leaching of coarse, massive sulphide ore particles(Stellenbosch : Stellenbosch University, 2015-12) Charikinya, Edson; Bradshaw, S. M.; Stellenbosch University. Faculty of Engineering. Dept. of Process Engineering.ENGLISH ABSTRACT: The aim of this work was to determine if microwave treatment of a typical massive sulphide ore, prior to bio-leaching would induce micro-cracks and enhance value mineral exposure resulting in improved bio-leaching metal extraction and kinetics. Using X-ray Computed tomography (XCT) and Quantitative Evaluation of Minerals by Scanning Electron Microscopy (QEMSCAN) image analysis techniques, the degree of microwave induced damage, and the effect of this damage on mineral exposure, was quantified directly for the first time, in this study. Ore sample preparation was carried out using a primary jaw crusher followed by secondary crushing by either high pressure grinding rolls (HPGR) or a cone crusher. Particles investigated consisted of small (-5+4.75) mm, medium (-16+9.5) mm, and large (-25+19) mm HPGR and cone crushed particles. XCT and QEMSCAN results showed the presence of microwave induced cracks within the cone and HPGR crushed particles, treated at a microwave power density of 1× 109 W/m3 abs and exposure time 1.00 s. A qualitative analysis of the cracks, showed that the cracks consisted of both interphase trans-granular and grain boundary cracks. Both XCT and QEMSCAN analysis results showed that microwave treatment resulted in a significant increase of over 500% in crack volume for both modes of prior comminution at all particle sizes. Measurements of specific interfacial areas of particles before and after microwave treatment using XCT showed average losses in interfacial area of 31%, 23% and 16% for small (-5+4.75) mm, medium (-16+9.5) mm, and large (-25+19) mm particles. This demonstrated quantitatively for the first time, that microwave treatment of sulphide ores results in both grain boundary and trans-granular fracture. Value mineral grain exposure analysis was carried out on the XCT 3D data of particles before and after microwave treatment. The results showed an increase in the degree of sulphide grain exposure of 28%, 26% and 15% for small medium and large particles respectively. This is the first time that microwave particle damage and enhanced mineral exposure has been successfully quantified experimentally using XCT and image analysis techniques. Column leaching experiments to simulate heap bio-leaching environment, were carried out over 350 days to assess the downstream benefits of microwave treatment of heap leaching feed. The results showed that microwave pre-treatment of crushed ore for bio-leaching, will lead to improved leaching recovery. Improvements in overall Zn metal recoveries of 26%, 24% and 23% were observed for small (-5+4.75) mm, medium (-16+9.5) mm, and large (-25+19) mm microwave treated particles. The enhanced metal recovery seen for microwave treated material correlates well with the crack volume measurements and mineral exposure results. The column leaching results showed that medium (-16+9.5) mm sized microwave treated particles had a 10.1% higher metal recovery compared to small (-5+4.75) mm untreated particles. A comparison of overall metal recoveries of microwave treated cone and HPGR crushed ore particles showed that the mode of prior comminution gave no significant difference in recoveries at all sizes. This suggests that microwave treatment reduces the influence of mode of comminution on bio-leaching recovery. An investigation of the dissolution of sulphide grains in selected particles, using XCT 3D image analysis techniques over the course of 350 days of leaching, showed greater sub-surface conversion of minerals in microwave treated particles compared to untreated. Analysis of the cracks over the period of leaching using XCT data, showed a growth in microwave induced crack networks over 350 days of leaching. This suggest that microwave induced cracks accelerate reagent diffusion into the particles resulting in sub-surface conversion of minerals, during bio-leaching. A bonded particle model (BPM) was developed to simulate a multiphase massive sulphide ore approximating the ore used in the physical experimental investigations. The developed ore model consisted of pyrite, sphalerite and quartz phases which were identified as the major phases in the ore used in the experiment. The resulting microwave induced crack patterns for different model resolution were compared against those obtained from physical experiments. The results showed that model resolution has a significant effect on observed microwave induced crack damage and patterns. It was observed that cracks in models with different resolution propagate in a different pattern despite having the same macro-mechanical properties. Crack patterns obtained for higher models were observed to compare well with crack patterns observed from physical microwave treatment experiments. It can be concluded that model calibration using the usual simulated UCS and Brazilian tests alone is not adequate to fix the model resolution, for simulations of thermal induced cracks. These results show that model specimen resolution has a significant effect on observed micro crack damage and that the minimum base material “particle” size is not a free parameter. The effect of absorbent phase content on microwave induced damage was investigated for the first time using a high resolution model. Damage maps which show the percentage of micro-cracks as a function of power density and exposure time for different ternary ores and absorbent phase content were constructed. It has been shown that for the same power density and energy input, the fraction of micro-fractures induced by microwave treatment considerably depends on absorbent phase grain content.
- ItemCharacterization and optimization of an extractor-type catalytic membrane reactor for meta-xylene isomerization over Pt-HZSM-5 catalyst(Stellenbosch : University of Stellenbosch, 2010-12) Daramola, Michael Olawale; Burger, A. J.; Lorenzen, L.; Giroir-Fendler, A.; University of Stellenbosch. Faculty of Engineering. Dept. of Civil Engineering.ENGLISH ABSTRACT: Future chemical production is faced with a challenge of limited material and energy resources. However, process intensification might play a significant role to alleviating this problem. Vision of process intensification through multifunctional reactors has stimulated research on membrane-based reactive separation processes, in which membrane separation and catalytic reaction occur simultaneously in one unit. These processes are rather attractive applications because they are potentially compact, less capital intensive, and have lower processing costs than traditional processes. Moreover, they often enhance the selectivity and yield of the target product. For about three decades, there has been a great evolution in p-Xylene production technology, with many equipment improvements being instituted in the industry. Typically, these improvements bring economic as well as processing advantages to the producers. Such developments are vital, as the capital costs for process equipment to produce and separate p-Xylene from xylene isomers, especially into high purity p-Xylene, still remain very high. However, with numerous advantages of membrane-based reactive separation processes compared to the conventional processes, the research focus has been channelled toward application of MFI-type zeolite membranes for in situ separation and isomerization of xylene in extractor-type catalytic membrane reactors. To contribute to this research line, this study has focused on characterization and optimization of an extractor-type catalytic membrane reactor (e-CMR) equipped with a nanocomposite MFI-alumina membrane as separation unit for m-Xylene isomerization over Pt-HZSM-5 catalyst. Nanocomposite MFI-alumina zeolite membranes (tubes and hollow fibres) used in this study were prepared via a so-called “hydrothermal pore-plugging synthesis technique” developed by Dalmon and his group more than a decade ago. In this concept, MFI material is grown by 'pore-plugging' direct hydrothermal synthesis in a porous matrix rather than forming thin films on top of the support. The advantages of this type of architecture over conventional film-like zeolite membranes include: (i) minimization of the effect of thermal expansion mismatch between the support and the zeolite, (ii) easy to scale-up, and (iii) easy module assembly, because the separative layer (zeolite crystals) are embedded within the pores of the ceramic support, reducing the effects of abrasion and thermal shocks. After membrane synthesis, the membrane quality and separation performance of these membranes were evaluated through single gas permeation (H2), binary gas separation (n-butane/H2) and ternary vapour mixture of xylene isomers using the vapour permeation (VP) method with p-Xylene as the target product. After evaluating the xylene isomer separation performance of the membranes, the membranes were used in extractor-type catalytic membrane reactors to carry out m-Xylene isomerization over Pt-HZSM-5 catalyst with p-Xylene as the target product. This dissertation has shown that nanocomposite MFI-alumina membrane tubes and hollow fibre membranes were selective to p-Xylene from xylene isomers. The dissertation also reports for the first time in open literature the excellent xylene separation performance of nanocomposite MFI-alumina membrane tubes at higher xylene loading (or vapour pressure). Unlike their film-like counterparts, the membranes still maintain increased selectivity to p- Xylene at higher xylene vapour pressures without showing a drastic decrease in selectivity. This outstanding property makes it a promising choice for pervaporation applications where concentration profile is usually a major problem at higher loading of xylene. With the use of nanocomposite MFI-alumina hollow fibre membranes, this research has demonstrated that membrane configuration and effective membrane wall thickness play a prominent role in enhancing cross membrane flux. Results presented in the study show, for the first time in open literature, that nanocomposite MFI-alumina hollow fibre membrane could enhance p-Xylene fluxes during the separation of ternary vapour mixture of xylene due to the smaller effective wall thickness of the membrane (membrane thickness <1 μm) when compared to conventional randomly oriented MFI zeolite films (membrane thickness >3 μm). During xylene isomers separation with nanocomposite hollow fibre membrane, about 30% increase in p-Xylene flux was obtained compared to the membrane tubes, operated under the same conditions. Additionally, hollow fibres offer the added advantage of membrane surfaceto- volume ratios as high as 3000 m2/m3 compared to conventional membrane tubes. Using this type of system could be instrumental in reducing both the size and cost of permeating modules for future xylene separation processes. However, obtaining high quality nanocomposite MFI-alumina membrane fibres is subject to the availability of high quality fibre supports. Regarding the application of nanocomposite MFI-alumina membrane tubes as extractor-type catalytic membrane reactors (referred to as extractor-type zeolite catalytic membrane reactor (e-ZCMR) in this study) for m-Xylene isomerization over Pt-HZSM-5, the results presented in this study further substantiate and confirm the potentials of e-ZCMRs over conventional fixed-bed reactors (FBRs). In the combined mode (products in the permeate plus products in the retentate), the e-ZCMR displayed 16-18% increase in p-Xylene yield compared to an equivalent fixed-bed reactor operated at the same operating conditions. On the basis of the high p-Xylene-to-o-Xylene (p/o) and p-Xylene-to-m-Xylene (p/m) separation factors offered by the membranes, p-Xylene compositions in the permeate-only mode (products in the permeate stream) in the range 95%-100% were obtained in the e-ZCMR. When a defect-free nanocomposite MFI-alumina membrane tube with p-Xylene-too- Xylene (p/o) separation factor >400 was used, ultra pure p-Xylene with p-Xylene purity approaching 100% in the permeate-only mode was obtained. Moreover, the e-ZCMR displayed 100% para-selectivity in the permeate-only mode throughout the temperatures tested. This is not possible with conventional film-like MFI-type zeolite membranes. Therefore, the application of nanocomposite MFI-alumina membranes in extractor-type catalytic membrane reactors could catalyse the development of energy-efficient membrane-based process for the production of high purity p-Xylene. Furthermore, in this dissertation, a report on modelling and sensitivity analysis of an e-ZCMR equipped with a nanocomposite MFI-alumina membrane tube as separation unit for m-Xylene isomerization over Pt-HZSM-5 catalyst is presented. The model output is in fair agreement with the experimental results with percentage errors (absolute) of 17%, 29%, 0.05% and 19.5% for p-Xylene yield in combined mode, p-Xylene selectivity in combined mode, p-Xylene selectivity in permeate-only mode and m-Xylene conversion, respectively. Therefore, the model is adequate to explain the behaviour of e-ZCMR during m-Xylene isomerization over Pt-HZSM-5 catalyst. The model is also adaptable to e-ZCMRs of different configurations such as hollow fibre MFI-alumina membrane-based e-ZCMRs. To gain more insight into the behaviour of the model to small changes in certain design parameters, sensitivity analysis was performed on the model. As expected, the sensitivity analysis revealed that intrinsic property of membrane (porosity, tortuosity), membrane effective thickness and reactor size (indicated with reactor internal diameter) play a significant role on the performance of e-ZCMR during p-Xylene production from the mixed xylenes. MFI-alumina zeolite membranes with optimized parameters such as membrane porosity, membrane tortuosity, and membrane effective wall thickness might enhance transport of p-Xylene through the membrane and thus resulting in higher p-Xylene flux through the membrane. This eventually would translate into an increase in p-Xylene yield in permeate-only mode. As far as it could be ascertained, this is the first report in open literature on modelling study with sensitivity analysis of e-ZCMR equipped with nanocomposite MFI-alumina membrane tubes as separation unit for m-Xylene isomerization over Pt-HZSM- 5 catalyst. In addition, the results of this study have confirmed previous research efforts reported on the application of extractor-type catalytic membrane reactors, having MFI-type membranes as separation units, for p-Xylene production via m-Xylene isomerization over a suitable catalyst. Also, new ideas were developed, tested and proposed that now provide a solid basis for further scale-up and techno-economical studies. Such studies are necessary to evaluate the competitiveness of the technology with the traditional processes for the production of high purity p-Xylene from mixed xylene. In summary, the encouraging results, as documented in this dissertation and also communicated to researchers in the area of membrane-based reactive separation (in the form of four peer-reviewed international scientific publications and four conference proceedings), could provide a platform for developing a scaled-up membrane-based energy-efficient industrial process for producing high purity p-Xylene through isomerization.
- ItemCogasification of coal and biomass : impact on condensate and syngas production(Stellenbosch : Stellenbosch University, 2012-03) Aboyade, Akinwale Olufemi; Gorgens, Johann F.; Meyer, Edson; Stellenbosch University. Faculty of Engineering. Dept. of Process Engineering.ENGLISH ABSTRACT: Gasification provides a proven alternative to the dependence on petroleum for the production of high value products such as liquid fuels and chemicals. Syngas, the main product from gasification can be converted to fuels and chemicals via a number of possible synthesis processes. Coal and natural gas are currently the main feedstock used for syngas production. In South Africa (SA), Sasol operates the largest commercial coal-to-liquids conversion process in the world, based on updraft fixed bed gasification of low grade coal to syngas. Co-utilizing alternative and more sustainable feedstock (such as biomass and wastes) with coal in existing coal-based plants offers a realistic approach to reducing the costs and risks associated with setting up dedicated biomass conversion plants. An experimental and modelling investigation was performed to assess the impacts of co-gasifying two of the most commonly available agricultural wastes in SA (sugarcane bagasse and corn residue) with typical low grade SA coals, on the main products of updraft fixed bed gasification, i.e. liquid condensates and syngas. Condensates are produced in the pyrolysis section of the updraft gasifier, whereas syngas is a result of residual char conversion. An experimental set-up that simulates the pyrolysis section of the gasifier was employed to investigate the yield and composition of devolatilized products at industrially relevant conditions of 26 bars and 400-600°C. The results show that about 15 wt% of coal and 70 wt% of biomass are devolatilized during the pyrolysis process. The biomass derived condensates were determined to comprise of significantly higher quantities of oxygenates such as organic acids, phenols, ketones, and alcohols, whereas coal derived hydrocarbon condensates were dominated by polycyclic aromatic hydrocarbons, creosotes and phenols. Results of investigation into the influence of coal-biomass feedstock mix ratio on yields of products from pyrolysis show limited evidence of non-additive or synergistic behaviour on the overall distribution of solid, liquid and gas yields. On the other hand, in terms of the distribution of specific liquid phase hydrocarbons, there was significant evidence in favour of non-additive pyrolysis behaviour, as indicated by the non-additive yield distribution of specific chemicals. Synergistic trends could also be observed in the thermogravimetric (TGA) study of pyrolysis under kinetically controlled non-isothermal conditions. Model free and model fitting kinetic analysis of the TGA data revealed activation energies ranging between 94-212 kJ mol-1 for the biomass fuels and 147-377 kJ mol-1 for coal. Synergistic interactions may be linked to the increased presence of hydrogen in biomass fuels which partially saturates free radicals formed during earlier stages of devolatilization, thereby preventing secondary recombination reactions that would have produced chars, allowing for the increased formation of volatile species instead. Analysis of char obtained from the co-pyrolysis experiments revealed that the fixed carbon and volatile content of the blended chars is is proportional to the percentage of biomass and coal in the mixture. CO2 reactivity experiments on the chars showed that the addition of biomass to coal did not impose any kinetic limitation on the gasification of blended chars. The blended chars decomposed at approximately the same rate as when coal was gasified alone, even at higher biomass concentrations in the original feedstock blend. Based on these observations, a semi-empirical equilibrium based simulation of syngas production for co-gasification of coalbiomass blends at various mix ratios was developed using ASPEN Plus. The model showed that H2/CO ratio was relatively unaffected by biomass addition to the coal fuel mix, whereas syngas heating value and thermal efficiency were negatively affected. Subsequent evaluation of the production cost of syngas at biomass inputs ranging between 0-20 wt% of coal reflected the significant additional cost of pretreating biomass (3.3% of total capital investment). This resulted in co-gasification derived syngas production costs of ZAR146/tonne (ZAR12.6/GJ) at 80:20 coalbiomass feedstock ratio, compared to a baseline (coal only) cost of ZAR130/tonne (ZAR10.7/GJ). Sensitivity analysis that varied biomass costs from ZAR0 ZAR470 revealed that syngas production costs from co-gasification remained significantly higher than baseline costs, even at low to zero prices of the biomass feedstock. This remained the case even after taking account of a carbon tax of up to ZAR117/tCO2. However, for range of carbon tax values suggested by the SA treasury (ZAR70 tCO2 to ZAR200 tCO2), the avoided carbon tax due to co-feeding biomass can offset between 40-96% of the specific retrofitting cost at 80:20 coal-biomass feedstock mass ratio. In summary, this dissertation has showed that in addition to the widely recognized problems of ash fouling and sintering, co-feeding of biomass in existing coal based updraft gasification plants poses some challenges in terms of impacts on condensates and syngas quality, and production costs. Further research is required to investigate the potential in ameliorating some of these impacts by developing new high value product streams (such as acetic acid) from the significant fraction of condensates derived from biomass.
- ItemCombinatorial evolution of feedforward neural network models for chemical processes(Stellenbosch : Stellenbosch University, 1999-11) Schmitz, Gregor Peter Josef; Aldrich, A.; Stellenbosch University. Faculty of Engineering. Dept. of Process Engineering.ENGLISH ABSTRACT: Neural networks, in particular feedforward neural networks architectures such as multilayer perceptrons and radial basis function networks, have been used successfully in many chemical engineering applications. A number of techniques exist with which such neural networks can be trained. These include backpropagation, k-means clustering and evolutionary algorithms. The latter method is particularly useful, as it is able to avoid local optima in the search space and can optimise parameters for which there exists no gradient information. Unfortunately only moderately-sized networks can be trained by this method, owing to the fact that evolutionary optimisation is extremely computationally intensive. In this paper, a novel algorithm called combinatorial evolution of regression nodes (CERN) is proposed for training non-linear regression models, such as neural networks. This evolutionary algorithm uses a branch-and-bound combinatorial search in the selection scheme to optimise groups of neural nodes. The use of a combinatorial search, for a set of basis nodes, in the optimisation of neural networks is a concept introduced for the first time in this thesis. Thereby it automatically solves the problem of permutational redundancy associated with the training of the hidden layer of a neural network. CERN was· further enhanced by using clustering, which actively supports niches in the population. This also enabled the optimisation of the node types to be used in the hidden layers, which need not necessarily be the same for each of the nodes. (i.e. a mixed layer of different node types can be found.) A restriction that does apply is that in order to make the combinatorial search efficient enough, the output layer of the neural network needs to be linear. CERN was found to be significantly more efficient than a conventional evolutionary algorithm not using a combinatorial search. It also trained faster than backpropagation with momentum and an adaptive learning rate. Although the Levenberg-Marquardt algorithm is nevertheless significantly faster than CERN, it struggled to train in the presence of many non-local minima. Furthermore, the Levenberg-Marquardt learning rule tends to overtrain, (see below) and requires a gradient information. CERN was analysed on seven real world and six synthetic data sets. Oriented ellipsoidal basis nodes optimised with CERN achieved significantly better accuracy with fewer nodes than spherical basis nodes optimised by means of k-means clustering. On the test data multilayer perceptrons optimised by CERN were found to be more accurate than those trained by the gradient descent techniques, backpropagation with momentum and the Levenberg-Marquardt update rule. The networks of CERN were also compared to the splines of MARS and were found to generalise significantly better or as well as MARS. However, for some data sets, MARS was used to select the input variables to use for the neural network models. Networks of ellipsoidal basis functions built by CERN were more compact and more accurate than radial basis function networks trained using k-means clustering. Moreover, the ellipsoidal nodes can be translated into fuzzy systems. The generalisation and complexity of the resulting fuzzy rules were comparable to fuzzy systems optimised by ANFIS, but did not result in an exponential increase of the number of rules. This was caused by the grid-partitioning employed by ANFIS and for data sets with a relatively high dimensionality, in comparison with the data points, the resulting generalisation was consequently much poorer than that of the CERN models. In summary, the proposed combinatorial selection scheme was able to make an existing evolutionary algorithm significantly faster for neural network optimisation. This made it computationally competitive with traditional gradient descent based techniques. Being an evolutionary algorithm, the proposed technique does not require a gradient and can therefore optimise a larger set of parameters in comparison to traditional techniques.
- ItemA comparative investigation of the technoeconomic feasibility and sustainability of mango waste biorefineries in South Africa: a process modeling approach(Stellenbosch : Stellenbosch University,, 2023-03) Manhongo, Tariro Tecla; Chimphango, Annie Fabian Abel; Thornley, Patricia; Stellenbosch University. Faculty of Engineering. Dept. of Chemical Engineering.ENGLISH ABSTRACT: Fruit processing waste (FPW) is a suitable biorefinery feedstock for conversion into bioenergy, biofuels, and chemicals. However, information on which processing routes and product combinations are economically viable and sustainable is limited. Using South Africa as a base developing economy, the availability of FPW as biorefinery feedstocks, economic viability, and sustainability of FPW-based biorefinery systems were evaluated in this study using mango processing waste as a base feedstock. Six biorefinery scenarios were evaluated; (I) combined heat and power (CHP) generation, (II) co-production of pectin and CHP, (III) co-production of pectin, polyphenols and CHP, (IV) co-production of pectin, bioethanol, and CHP, (V) co-production of pectin, polyphenols, bioethanol, and CHP, and (VI) co-production of bioethanol and CHP. In scenarios II to VI, residues from pectin and/or polyphenols recovery and wastewater are anaerobically digested for biogas production and the biogas in all scenarios is co-combusted with mango seed for steam generation (for use within the biorefinery and export to the host dried mango chips facility) and power (for consumption within the biorefinery and export if excess is generated). Aspen Plus process simulation models were developed at a plant capacity of 1500 tonnes per day (1200 tonnes process wastewater + 133.33 tonnes peel + 166.67 tonnes seed), operating for 24 h/day, and 120 days/annum. A discounted cash flow analysis was employed in assessing the economic viability of the six biorefinery models using the mass and energy flows from the models and incorporated in SimaPro-based attributional life cycle analysis models to evaluate the environmental impacts of the biorefineries. Using systems thinking, results from the technoeconomic analysis were employed in estimating the socio-economic benefits of the biorefineries using input-output Jobs and Economic Development Impact assessment models adopted from the National Energy Renewable Laboratory. Indicators for economic, environmental, and socio-economic performances of the biorefineries were normalized, weighted, and aggregated in a multi-criterion decision analysis approach to compare sustainability performances of the biorefineries. Scenarios I and VI are economically unattractive with net present values (NPVs) of -$94.4 and -$120.9 million, respectively. NPVs of the biorefineries increase with the recovery of more products in the order Scenario IV
- ItemComparing the environmental impact of different hydrometallurgical processes for the recycling of lithium-ion batteries using a life cycle assessment approach(Stellenbosch : Stellenbosch University, 2024-03) Maritz, Roelof Frederick; Dorfling, Christie; Akdogan, Guven; Stellenbosch University. Faculty of Engineering. Dept. of Chemical Engineering. Process Engineering.ENGLISH ABSTRACT: Lithium-ion batteries (LIBs) have become commonplace for everyday use in consumer electronics. These batteries have also gained a lot of popularity recently for usage in larger scale application such as electric vehicles (EV). The LIB market is projected to grow from 700 GWh in 2022 to 4.7 TWh in 2030 (Fleischmann et al., 2023). The consequence of this rapidly increasing demand for LIBs is the formation of a fast-growing end-of-life (EOL) LIB waste stream. This waste stream includes valuable metals such as lithium, cobalt, nickel, and manganese to potentially be recycled, thus providing benefits in terms of waste management and income from the sale of these recovered metals. There is thus a clear need for EOL LIB recycling and a necessity to find out what is the best process technology available to recycle EOL LIBs. Traditionally LIBs have been recycled using pyrometallurgy, but the recent industry focus has shifted towards alternative process technologies such as hydrometallurgy. There is, however, no clear consensus on how these hydrometallurgical flowsheets should be arranged. As such, the purpose of this study was to compare the environmental impacts of implementing different hydrometallurgical process flowsheets designed for the recovery of metals from EOL LIBs. This comparative environmental study was performed using the life cycle assessment (LCA) framework and considered the use of three lixiviants (hydrochloric-, sulphuric-, and citric acid) alongside the use of three flowsheet options (sequential metal precipitation, mixed metal precipitation, and hybrid sequential precipitation - solvent extraction systems). Lastly, the process was modelled based on a mixed feed of LiCoO2, LiFePO4, and NMC111 batteries. The potential environmental impacts of mineral acid-based processes were found to generally be lower than that of organic acid-based processes by 18 to 61 percentage points. Furthermore, mixed metal precipitation provided the greatest environmental benefit of the flowsheet options considered by 46 to 117 percentage points when compared to the closest competitor. The LCA system was subsequently subjected to multivariate uncertainty analysis and a discernability analysis regarding process feed sensitivity which served to confirm the trends already observed. The LCA system was also subjected to a weak point analysis, where the consumption of NaOH and electricity were listed as the main concerns for process improvement. The process solutions recommended to address both weak points involve the integration of membrane technology and antisolvent crystallisation. Furthermore, the LCA system was compared for a South African and a European context, where it was determined that South Africa’s overreliance on hard coal for energy generation is the main difference between the two regions. Finally, the hydrometallurgical EOL LIB recycling processes were subjected to an additional LCA study regarding the use of recycled metals for resynthesizing NMC cathode materials. This additional study showed that integrating the sequential precipitation recycling process with solid-state synthesis of NMC622 cathode could save up to 70% on energy consumption during cathode synthesis. Meanwhile, integrating the mixed NMC precipitation recycling process with the solid-state synthesis of NMC622 cathode could reduce the environmental impact of NMC cathode production by up to 67%.
- ItemComputerized design of solvents for extractive processes(Stellenbosch : Stellenbosch University, 2001-12) Van Dyk, Braam; Nieuwoudt, I.; Stellenbosch University. Faculty of Engineering. Dept. of Process Engineering.ENGLISH ABSTRACT: Separation processes are an integral part of chemical engineering. The purity of a chemical product is among the principal factors influencing its value. Therefore, any method that can increase the purity of a product or decrease the cost of purification will have a direct effect on the profitability of the entire plant. An important class of separation processes is the solvent-based separations. This includes processes like extractive distillation, liquid-liquid extraction and chromatographic separation. Heterogeneous azeotropic distillation is closely related to these processes. The most important variable in the design of a solvent-based separation process is the choice of solvent. A genetic algorithm for the computer-aided molecular design of solvents for extractive distillation had been previously developed by the author. This algorithm was improved and expanded to include liquid-liquid extraction, heterogeneous azeotropic distillation, gas-liquid chromatography and liquid-liquid (partition) chromatography. At the same time the efficiency of the algorithm was improved, resulting in a speed increase of up to 500% in certain cases. An automatic parameter tuning algorithm was also implemented to ensure maximum efficiency of the underlying genetic algorithm. In order to find suitable entrainers for heterogeneous azeotropic distillation a method is required to locate any ternary heterogeneous azeotropes present in a system. A number of methods proposed in the literature were evaluated and found to be computationally inefficient. Two new methods were therefore developed for ternary systems. A methodology for applying these methods to quaternary and higher systems was also proposed. Two algorithms to design blended solvents were also developed. Blended solvents allow the use of simpler and thus cheaper solvents by spreading the active functional groups over several molecular backbones. It was observed in a number of cases that the blended solvents performed better than their individual components. This was attributed to synergistic interactions between these components. Experimental evidence for this effect was also found. The algorithm was applied to a number of industrially important separation problems, including the extremely difficult final purification process of alpha olefins. In each case solvents were found that are predicted to perform substantially better than those that are currently used in industry. A number of these predictions were tested by experiment and found to hold true.
- ItemContributions to an improved understanding of the flotation process(Stellenbosch : University of Stellenbosch, 2005-12) O'Connor, Cyril Thomas; Lorenzen, L.; University of Stellenbosch. Faculty of Engineering. Dept. of Process Engineering.This dissertation covers research carried out over the past 25 years in the area of flotation. Flotation is one of the most widely used processes in the beneficiation of minerals. The process is characterized by a number of important sub-processes each with their own set of critical variables. These include: • The pulp phase which is influenced by variables such as pH, Eh, the nature of the chemical reagents used, the chemical state of the surface of the ore particles, etc. • The reactor in which the process occurs, viz. the flotation cell, which is influenced by factors such as aspect ratio, degree of agitation, mechanical design criteria, energy input, aeration processes, etc. • The froth phase which is arguably the heart of the process and probably the least well understood but which is influenced by factors such as size and shape of the solid particles in the froth, the nature of the surfactant used, the aeration rate, the water recovery rate, the froth depth, etc.
- ItemContributions to the mechanisms and simulation of mineral processing operations(Stellenbosch : Stellenbosch University, 1999-08) Van Deventer, Jan Stephanus Jakob; Lorenzen, L.; Stellenbosch University. Faculty of Engineering. Dept. of Process Engineering.ENGLISH ABSTRACT: This collection of 101 published papers is based on 19 years of research, mainly in South Africa and recently also in Australia. The main thrust of this work was the simulation of mineral processing operations where conventional modelling was inadequate owing to their ill-defIned nature. These papers presented some of the first applications of knowledge based systems and neural networks to mineral processing problems. A new methodology was proposed for modelling ill-defmed kinetic processes by relating rates to process conditions via non-parametric methods. The kinetic and equilibrium parameters could be related to adjustment factors if reference conditions changed. These methods were applied to batch and continuous flotation, leaching and adsorption systems as well as pyrometallurgical processes. In the case of continuous process data intrinsic reaction rates could be back -calculated and then related to process conditions via a neural net. It was explained how the configuration of mineral processing circuits could be optimised by a two-stage linear programming method where the constraints were determined interactively by a knowledge based system or neural network. In the case of non-linear system constraints neural nets were shown to detect and locate gross errors efficiently in material balancing problems. Several novel hybrid neural net architectures were proposed which allowed the integration of parametric fundamental knowledge with non-parametric heuristic knowledge. Furthermore, it was shown how neural nets could be used to extract knowledge from historical process data records. Pioneering work was conducted on the application of textural image analysis to flotation froth surfaces and ore particles on a conveyor belt. It was possible to relate image features to metallurgical performance via neural net architectures. Different types of topological maps were used to classify froth types, to track the profile of changes in process and flotation conditions, and to relate froth class to concentrate grade and recovery. Perturbations in the comminution circuit were reflected in perturbations in the froth image features and metallurgical performance. It was also shown that the spray angle of a hydrocyc1one as determined by image analysis could be used as input to a soft sensor for predicting size distribution. A model was developed to combine transport phenomena in the froth phase with fluid flow behaviour in order to optimise mechanical cells and flotation columns. Rate constants for the various sub-processes were determined by fitting models to concentration profiles measured at industrial plants. It was shown that the behaviour of the froth phase during the flotation of sulphides, gold and uranium was affected by galvanic interaction between metallic iron and the individual mineral species. A conceptual model was developed for the flotation behaviour of free gold in the presence of refractory sulphides for different oxidative conditions and different sequences of reagent addition. The use of diagnostic leaching to evaluate the efficiency of mineral processing operations was explained in detail. A first attempt was made to relate diagnostic leaching data to mineral liberation via semi-empirical equations and neural nets. It was explained how the liberation patterns of different types of gold ore could be distinguished by using topological maps. The mechanisms of selected sundry processes such as electrokinetic solid-liquid separation, flow splitting, induced aeration and jet reactors were also investigated.
- ItemContributions to theoretical developments and practical exploitation of mass transfer principles in separation technologies(Stellenbosch : Stellenbosch University, 2023-12) Nieuwoudt, Izak; Burger, Andries Jacobus; Stellenbosch University. Faculty of Engineering. Dept. of Chemical Engineering. Process Engineering.ENGLISH ABSTRACT: Our standard of living and quality of life rely on producing consumer products from chemicals. These chemicals typically have to be purified, and distillation, extraction and absorption are the primary technologies for affecting these separations. Such technologies are energy intensive, and further development and optimization can reduce their impact on greenhouse gas emissions. Furthermore, reduction in the capital consumed by these processes can significantly improve value creation. My contributions to these fields over the past 36 years are covered in detail in this dissertation under the sections highlighted below. It is conservatively estimated that these contributions generated more than two billion dollars of value for the companies who commercialized and use these technologies. In the process of making contributions to this field, I have been blessed to collaborate with brilliant people and their contributions to my endeavors are gratefully acknowledged. Improved separation processes My research into separation processes with reduced energy and capital consumption was focused on solvent-driven separations. Computer Aided Molecular Design (CAMD) methodologies for solventdriven separation processes were developed and, from this, improved extractive distillation, azeotropic distillation and liquid extraction processes were conceived. The energy and capital consumption of these processes were significantly lower than that of competing technologies, which also translates into lower greenhouse gas emissions. These processes were commercialized and create significant value for the chemical producers and the companies who produce consumer products. Improved separation tower internals My research into separation tower internals was focused on creating novel equipment that had higher separation efficiency and higher hydraulic capacity than the best equipment available at the time. The novel INTALOX® ULTRATM random packing exhibited higher efficiency and capacity than other random packing. This allowed chemical companies and refiners to debottleneck towers for capacity and/or separation efficiency. This reduced energy consumption and corresponding greenhouse gas emissions. The size of new towers could also be reduced. The PROFLUX® severe service packing allowed refiners to increase capacity, increase run lengths and increase the product yield in vacuum towers. I developed several tray configurations that improved the capacity and/or efficiency of separation towers. Other developments included improved liquid distributors and droplet separators. These new, improved separation tower products generated significant value for both the companies that commercialized it and the end-users who installed it in their separation towers. Separation technology education Although the separation processes and separation tower internals discussed in this dissertation generated significant revenue for the companies who commercialized and used these technologies, the lasting value lies in the underlying methodologies and knowledge that were developed. It is important that this knowledge be passed on to the next generation of engineers. To this end, I have developed university courses, the Koch-Glitsch Mass Transfer School and the FRI Distillation Academy. Under my guidance 14 Masters and 7 PhD students graduated in the field of separation technology. Almost 1000 students attended these courses and many commented that they have received unique knowledge that equipped them for the future. The details of my non-confidential contributions to the field of separation technology have been summarized in 410 patents (46 patent families), 48 papers and 80 conference contributions. At the 2022 Spring Meeting the Separations Division of the American Institute of Chemical Engineers (AIChE) gave special recognition to my “many outstanding achievements in distillation, extraction, 5 absorption, and troubleshooting” by dedicating an honors session to celebrate my “lifetime of contributions as an engineer, educator, inventor, and R&D leader in separations technology and engineering”.