<p> A neutron activation analysis procedure for the simultaneous determination of Ru, Pd, Os, Ir, Pt and Au has been developed. It consists principally of distillation, anion exchange, solvent extraction and precipitation steps and was used to determine all of these metals in meteorites as well as Pd, Ir and Au in sulphide minerals from the Sudbury Nickel Irruptive. The accuracy of the method was checked against G-1 and W-1 and a sulphide standard. A literature survey of the geology of the Sudbury Nickel Irruptive and a description of the geology of the Strathcona mine are presented. A detailed description of the inorganic chemistr! and its bearing on the geochemistry of the precious metals, with special reference to basic rocks is given. Analytical results for Pd, Ir and Au in a large number of pyrrhotite and chalcopyrite samples and a smaller number of sulphide and oxide minerals and an ultramafic xenolith are presented. Arsenic was determined in 15 of the sulphide samples and found to be highly correlated with Pd. The genesis of the Strathcona ores is discussed and the differential behaviour of the precious metals during fractionation or a sulphide-rich basic magma is described. </p> <p> Seven carbonaceous and two enstatite chondrites were analysed and the data evaluated with respect to estimation of the cosmic abundances of these metals. </p> / Thesis / Doctor of Philosophy (PhD)

<p> Steady state heat and mass balancing around an ethylene/ethane distillation unit at Polymer Corporation, Sarnia is studied using the CHESS simulation executive system.</p> <p> The unit involves a single column with reboiler heat provided by recompression of the overhead vapor stream.</p> <p> A new column model is developed, based on the approximate pseudo-binary method of Hengstebeck, and is shown to give good results with marked savings in computation time over the conventional tray to tray methods. Models for vapor compression and heat exchange are also presented.</p> <p> The system model is fitted to plant data and a routine developed to obtain satisfactory system convergence.</p> <p> A parametric study is carried out in which column pressure and distillate product enthalpy are varied to demonstrate significant improvements in plant operation.</p> <p> An evaluation of the CHESS simulation system is presented.</p> / Thesis / Master of Engineering (MEngr)

Distillation technology has been evolving for many decades for a variety of reasons, with the most important ones being energy efficiency and cost. As a part of the evolution, semicontinuous distillation was conceived, which has the advantages of both batch and continuous distillation. The economic benefits of this intensified process compared to batch and continuous distillation were expounded in many of the previous studies. Semicontinuous distillation of ternary mixtures, which is the main focus of this thesis, is carried out in a single distillation column with a tightly integrated external middle vessel and the operation is driven by a control system. The system operation does not include any start-up or shut-down phases of the column and has three periodically repeating operating modes. In the status quo design procedure, called the ‘sequential design methodology,’ an imaginary continuous distillation system design was used to design the semicontinuous distillation system. In this methodology, dynamic simulations of the process were used to find the values of the controller tuning parameters based on the design of the continuous system. Afterwards, black-box optimization was used to find better controller tuning parameter values that minimized cost. However, after analyzing the dynamics of the system for different cases, it was found that the heuristics used in this design methodology yielded suboptimal designs. Therefore, the primary goal of the thesis is to improve these heuristics by incorporating more knowledge of the system and thereby develop a better design methodology. Firstly, the setpoint trajectories generated by the ideal side draw recovery arrangement for side stream flowrate control, which was standard in most semicontinuous distillation studies, was modified. In this thesis, the performance of the status quo as compared to the modified version, based on the criteria, cycle time and cost for different case studies, was presented. Results showed that the modified-ideal side draw recovery arrangement for side stream flowrate control performed better with a 10-20% lower separating cost while maintaining product purities. Furthermore, to reap more cost benefits, dynamic optimization was used to seek the flow rate trajectory that minimized cost. However, it was found that the additional cost savings, which is in addition to the benefits gained by using the modified version, were at the most 2% from different case studies. Subsequently, the impact of changing the imaginary continuous distillation system design on the nature of the semicontinuous distillation limit cycle, specifically, its period was studied. Results revealed the necessity for a new design procedure, and thus the back-stepping design methodology was proposed. This design methodology was used to find better limit cycles of zeotropic ternary semicontinuous distillation using the aspenONE Engineering suite. The proposed methodology was applied to three different case studies using feed mixtures with different chemical components. A comparison with the sequential design methodology for the two case studies indicates that the new method outperforms the state-of-the-art by finding limit cycles that were 4% to 57% lower in terms of cost. Furthermore, the designs obtained from this procedure were guaranteed to have feasible column operation with stable periodic steady-state behaviour. Semicontinuous distillation design using the design methodology with heuristic components involves guessing, checking and then using black-box optimization to find the values of the design variables to meet some performance criteria. Furthermore, mathematical guarantees of either local or global optimality of the designs obtained from the design procedure do not exist. Therefore, to address these issues, in this thesis, the application of using the shooting method for designing the semicontinuous distillation process was demonstrated using two case studies, which involve the separation of hexane, heptane and octane. This method has the potential to be combined with gradient-based optimization algorithms for optimization of the process design in the future. / Thesis / Doctor of Philosophy (PhD)

Yes / In this work, an artificial neural network (ANN) model based on the experimental data was developed to study the performance of vacuum membrane distillation (VMD) desalination process under different operating parameters such as the feed inlet temperature, the vacuum pressure, the feed flow rate and the feed salt concentration. The proposed model was found to be capable of predicting accurately the unseen data of the VMD desalination process. The correlation coefficient of the overall agreement between the ANN predictions and experimental data was found to be more than 0.994. The calculation value of the coefficient of variation (CV) was 0.02622, and there was coincident overlap between the target and the output data from the 3D generalization diagrams. The optimal operating conditions of the VMD process can be obtained from the performance analysis of the ANN model with a maximum permeate flux and an acceptable CV value based on the experiment.

Yes / This paper presents a simulation study of vacuum membrane distillation (VMD) for desalination. A simulation model was built on Aspen Plus® platform as user defined unit operation for VMD module. A simplified mathematical model was verified and the analysis of process performance based on simulation was also carried out. Temperature and concentration polarization effects are significant in the conditions of higher feed temperature and/or vacuum pressure. The sign of difference of the vapour pressures between at the membrane interfaces, is a pointer of the vacuum pressure threshold. Increasing the vacuum pressure at lower feed temperature is an effective way to increase the permeate flux and reduce the energy consumption simultaneously.

No / In this work, energy consumption in a middle vessel batch reactive distillation (MVBRD) column is considered for the production of lactic acid via hydrolysis of methyl lactate. A dynamic optimization problem incorporating a process model is formulated to minimize the batch time which consequently minimizes the total energy consumption. The problem is subject to constraints on the amount and purity of lactic acid. The optimisation variables are reflux ratio and/or reboil ratio which are treated as piecewise constant. The earlier work of the authors on energy consumption in conventional batch reactive distillation column (CBRD) for the same reaction system is used for comparative analysis with the energy consumption in MVBRD. As an example, for a given separation task, the optimization results show that MVBRD is capable of saving over 23 % energy compared to energy consumption in CBRD column for the same task.

The vacuum distillation of heat-sensitive substances such as organic oils, dyes, and drugs requires special equipment from that available for atmospheric distillation. Study in the resulting field, high vacuum distillation, has subsequently led to the development of such equipment. Three types of high vacuum distillation and distillation equipment are recognized: conventional distillation, unobstructed-path distillation, and molecular distillation. Conventional vacuum distillation employs standard equipment under relatively high vacuum conditions. For unobstructed-path distillation, the equipment is modified so that the vapor path between the evaporating and condensing surfaces is clear. When the vapor path is unobstructed and the condenser is separated from the evaporator by a distance less than the mean free path of the evaporating molecules, the phenomenon is called molecular distillation. Molecular distillation is the limiting type of high vacuum distillation with the absolute pressure range approximately 1 to 7 microns of mercury. The use of the centrifugal molecular still permits the distillation of organic substances which might suffer thermal decomposition even under the conditions of the conventional high vacuum still. Against the advantages of prevention of thermal decomposition and shorter time requirements must be placed the poor separatory power of distillation and the necessity of numerous redistillations. The molecular still is valuable not because it gives good separation but because distillation is accomplished 50 to 250 degrees centigrade below temperatures of conventional atmospheric distillation. In ideal molecular distillation, equilibrium does not exist between the vapor and the liquid, no molecules re-enter the distilland after once being vaporized. Under these ideal conditions, Langmuir's equation predicts that the quantity of a given material distilling at a given temperature is proportional to P/√M where P is the vapor pressure and M is the molecular weight. Previous investigations at the Virginia Polytechnic Institute and other laboratories substantiate the importance of molecular weight and structure. Since most of these investigations have been only exploratory, insufficient work has been done to permit any conclusions of major importance. The purpose of this investigation was to determine the effects of various molecular structures of fatty acids on their distillation characteristics when distilled in a laboratory-size centrifugal molecular still. Saturated (C₁₅, C₁₆, C₁₇, C₁₈, C₁₉, and C₂₀) and unsaturated (C₁₈ with one, two, and three double bonds) fatty acids were used in the study. Such effects as the chain length, presence of double bonds and their position in the molecule, and cis-trans and positional isomerism were studied. / Ph. D.

The three basic requirements for unobstructed, short path distillation are: a surface over which a think layer of distilland is distributed, a cooler condensing surface in close proximity to the evaporating surface, and a suitable system for evacuating the space between the two surfaces. When the distance of transfer between the evaporating and condensing surfaces is comparable to the mean free path of the vapor molecules in the residual gas, the process is known as molecular distillation. [Continued in document] / Ph. D.

no abstract provided by author / Master of Science

The theory involved in actual distillation phenomena encountered in molecular distillation has, to the present date, been only lightly explored. Scientific research has been replaced mainly with the need for improving the practical applications ot the process. As a result, although few theoretical correlations have been evolved, the present day high-speed centrifugal molecular stills are capable of effecting separations and purifications economically impossible by any other means. Molecular distillation has found wide commercial application in the separation and purification of such normally non-distillable, high molecular weight, thermally unstable substances as vitamins A and E, industrial synthetics, plasticizers, fatty acid dimers, and the like. In investigating the theory underlying molecular distillation, only a few classes of compounds have been used; the most important of these being pilot dyes, and to a lesser extent, fatty acids. The use of the latter class of compounds has been slight, despite their ease of analysis, ready, solubility in various carrier oils, and the availability of a large number of the series for investigative purposes. It was the purpose of this investigation to molecular distill a number of these fatty acids and, from a study of the elimination curves obtained, to determine the effects of molecular weight, molecular structure, and degree of unsaturation on these maxima. The five-inch magnetically-driven centrifugal molecular still employed for the investigation was modified slightly from a previous design. Two metal diffusion pumps which were a part of the vacuum pumping system were replaced by a third megavac forepump, which was in turn connected through a manifold arrangement with the original two that were in the system. A gravity-feed system was also installed; the modification consisted of elevating the feed tank above the still head assembly, and installing a needle valve in the feed line for accurate feed rate control. Preliminary vacuum tests were roads on the modified still, and the development of a synthetic constant-yield oil for use in the investigation was undertaken. From a number of distillation tests made on individual and blended mixtures of various petroleum oils, it was found that a blend of 225 milliliters of Voltesso No 36, 175 milliliters of light mineral, and 425 milliliters of heavy mineral oil distilled in approximately constant volumetric quantities over the temperature range of 86 to 146 degrees Centigrade. The development of a constant-yield oil led to the standardization of an operating procedure which was to be used for all the tests. The operating variables that were held constant for the distillation studies included: feed rate 60 to 65 milliliters per minute; operating pressure, 12 ± 2 microns of mercury; feed-residue temperature difference, 24 ± 1/2 degrees Centigrade; rotor speed, 1000 ± 50 revolutions per minute; condenser water temperature, 45 ± 1 degrees Centigrade; and one pass of the feed mixture across the rotor per fraction. Six saturated fatty acids, pentadecylic, palmitic, margaric, stearic, nonadecylic, and arachidic; one monoethenoid, oleic; and one diethenoid, linoleic, were then individually distilled using the standardized operating procedure devised in the investigation. The elimination curves were plotted and the maxima were found to be 100, 102, 110, 112, 127, 122, 110, 108 degrees Centigrade, respectively. These maxima were then compared to determine what effect molecular weight, molecular structure, and degree of unsaturation had on the maxima. It was concluded from this investigation that the addition of two CH₂ groups in the molecule of a homologous series of long-chain even numbered carbon atom aliphatic fatty acids raises the elimination maximum 10 degrees Centigrade. It was found that no valid prediction as to the effect of the addition of one CH₂ group to a homologous series of long-chain aliphatic fatty acids can be made. The study indicated that molecular structure; that is, chain length, has a definite, but unpredictable influence on the elimination maximum. It was also found that the addition of each unconjugated double bond in a molecule of a homologous series of fatty acids lowers the elimination maximum two degrees Centigrade. / Master of Science