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The material presented in this thesis falls into two main sections: 1. The determination of barium, strontium and calcium in oil-well waters (i) Determination of barium It is revealed that the addition of magnesium (5 g l-1) to samples for the determination of barium by d.c. plasma atomic emission spectrometry enhances the sensitivity of the analysis and dramatically reduces interference from calcium and strontium at both atomic and ionic emission wavelengths. (ii) Determination of strontium The determination of strontium in waters, was also subject to the interference of the concomitant elements like calcium, barium and magnesium. However, the addition of 3 g l-1 sodium with or without 5 g l-1 of magnesium eliminated all the interferences in the d.c. plasma and in the dinitrogen oxide-acetylene flame. (iii) Determination of calcium The determination of calcium in oil-well waters encountered some interference arising from the presence of sulfate. However, the effects of phosphate and sodium were also investigated in both air-acetylene and dinitrogen oxide-acetylene flames and in the direct current plasma. It was shown that the interference was reduced in the cool flame when 2 g l-1 of lanthanum was added. The absorbance of calcium was depressed by the presence of 2 g l-1 of sodium. The interferences from both sulfate and phosphate were eliminated when the hot flame or the d.c. plasma were used. 2. Slurry nebulization for soil, sediment and fertilizer samples A slurry atomisation direct current plasma (DCP) emission and flame atomic absorption and emission (FAAS and FAES) for the determination of alkaline earth elements and also of other minor and major elements in soils, marine sediments and fertilizer is reported. The results obtained by slurry nebulization, with lithium added as ionisation buffer, were compared with results obtained following fusion with LiBO2 at 950o for 10 minutes and dissolution of the residues in 4&'37 HNO3.

An understanding of the processes involved in oil spills, and how they interact to alter the composition and behavior of the oil with respect to time is essential to determine an effective oil spill response. The review of past research has shown more focus on the laboratory methods and computerized modeling schemes to estimate the formation and breaking of emulsions after an oil spill. However, relatively less effort has gone into the study of emulsions corresponding to actual field conditions. This research aims to simulate an oil spill at sea by developing a new technique to make water in oil emulsions, without disturbing the marine wildlife. Further, this research also attempts to analyze the viscosities of water in oil emulsions and determine appropriate emulsion breakers for different crude oil emulsions. The overall test design for the study includes a test apparatus for spreading and evaporation, three different crude oils, a mixing chamber to form the emulsion, and emulsion breakers. Experiments in this research attempt to gain a better understanding of the processes that occur after oil spills at sea. In particular, the rate of evaporation of different crude oils and the formation of crude oil emulsions on the sea surface have been investigated. It was observed that different crude oils behave differently when subjected to the same weathering procedure. Results indicate that the behavior of the crude oil on the sea surface, subjected to spreading, evaporation, and emulsification, can be predicted by using the new technique developed in this research. This technique can also assist the development of effective recovery equipments and materials.

An understanding of the processes involved in oil spills, and how they interact to alter the composition and behavior of the oil with respect to time is essential to determine an effective oil spill response. The review of past research has shown more focus on the laboratory methods and computerized modeling schemes to estimate the formation and breaking of emulsions after an oil spill. However, relatively less effort has gone into the study of emulsions corresponding to actual field conditions. This research aims to simulate an oil spill at sea by developing a new technique to make water in oil emulsions, without disturbing the marine wildlife. Further, this research also attempts to analyze the viscosities of water in oil emulsions and determine appropriate emulsion breakers for different crude oil emulsions. The overall test design for the study includes a test apparatus for spreading and evaporation, three different crude oils, a mixing chamber to form the emulsion, and emulsion breakers. Experiments in this research attempt to gain a better understanding of the processes that occur after oil spills at sea. In particular, the rate of evaporation of different crude oils and the formation of crude oil emulsions on the sea surface have been investigated. It was observed that different crude oils behave differently when subjected to the same weathering procedure. Results indicate that the behavior of the crude oil on the sea surface, subjected to spreading, evaporation, and emulsification, can be predicted by using the new technique developed in this research. This technique can also assist the development of effective recovery equipments and materials.

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Heat-integrated crude oil distillation systems – the atmospheric and vacuum distillation towers and associated heat recovery system – are energy and capital intensive. The structures of the distillation columns are very complex and the distillation columns interact strongly with the preheat train. There are many degrees of freedom in this system, most of which are interlinked with each other and cannot be considered separately. A systematic design approach is necessary to exploit these design issues for increasing the efficiency with which energy and capital are employed in the overall system. This thesis develops an optimisation-based methodology for the simultaneous design of crude oil distillation systems. Both new design and retrofit scenarios are considered. This design approach considers some significant design issues and generates design solutions that are realisable and industrially practicable. Robust and more accurate models have been developed to represent the distillation columns and heat exchanger networks (HENs) within an optimisation framework, compared with previous work. Facilitated by the decomposition approach (Liebmann, 1996), simplified models (Suphanit, 1999; Gadalla et al., 2003a; Rastogi, 2006), based on the Fenske-Underwood-Gilliland method, were developed previously to model the atmospheric distillation unit and the vacuum unit. This work extends and modifies these simplified models to account more accurately for the effect of pump-around location on the separation performance in atmospheric units. Moreover, the simplified model has been extended to consider an atmospheric distillation column with a pump-around located above the top side-stripper. This work also proposes a new methodology to incorporate product specifications following refining conventional in the simplified models. The proposed approach enables systematic identification of key components and associated recoveries to match specified boiling temperature profiles, as these are normally used as indicators of separation performance in the refining industry. The new simplified models are validated by comparison with rigorous simulation results of atmospheric distillation columns. Multi-segmented stream data are implemented in the design and analysis of heat exchanger networks, in which the thermal properties of streams are temperature dependent and cannot be assumed constant. Two existing promising HEN design approaches, the simulated annealing optimisation-based approach (Rodriguez, 2005)and the network pinch approach (Asante and Zhu, 1996), are modified and extended to apply to the HEN design with multi-segmented stream data. In the modified network pinch approach, the bottleneck of an existing HEN configuration is better overcome by varying stream split fractions and heat exchanger loads at the same time, rather than simply redistributing heat loads. The modified network pinch approach also combines structural modifications and cost optimisation in a single step to avoid missing cost-effective design solutions. An optimisation framework, applying a stochastic optimisation method – multiple simulated annealing runs – is developed to generate grassroots and retrofit designs of the heat-integrated crude oil distillation systems. The heat integration of the system is accounted for more accurately than previously by using multi-segmented stream data. Operating conditions and pump-around locations of distillation columns are optimised, together with structural options and continuous variables of heat exchanger networks as appropriate, in a single optimisation framework. The new degrees of freedom considered in this work include key components and associated recoveries (used in simplified models of distillation columns to express the separation of products) and operating pressures of distillation columns. The optimisation of key components and recoveries allow the systematic exploitation of product distributions and product slate in order to maximise net profit. Including operating pressures in the optimisation facilitates creation of heat recovery opportunities in configuration studies. Product specification constraints are imposed in the optimisation so that product quality is not compromised during design. A novel distillation configuration, with a liquid side-draw prefractionator column upstream of an atmospheric distillation column, is proposed in this work. The case study shows a very promising performance with respect to energy efficiency. Case studies illustrate the beneficial application of the proposed approach in both grassroots and retrofit design of crude oil distillation systems, with respect to energy demand and net profit improvement. Comparisons are made between different configurations, and results are given as proof of principle.

The main objective of this thesis was to study the effects of crude oil extracts on intertidal sediment communities. The approach was to focus on community structure and investigate the impact of a specific perturbation, crude oil extracts, relating to hypothetical oil spill situations. Both the impact of different disturbances on the same benthic community (i.e. with uniform structure) and the impact of the same disturbance on differently structured benthic communities were investigated. The effects on number of species, distribution of individuals between species and diversity were analysed, as well as recovery mode (trajectory of the system in time) and species arrival. The effects of different levels of a disturbance on an intertidal community were assessed, using water soluble fractions of crude oil (WSF) and two different concentrations of formaldehyde. The WSF had very little effect on community structure and recovery of the benthic community was prompt. The effects of the different concentrations of formaldehyde on the benthic community were indistinguishable: both concentrations had dramatic immediate effects. The relation between complexity and stability in benthic communities was evaluated by first setting-up two communities of different complexity using the equilibrium theory of island biogeography. After these different communities were established they were subjected to the effects of oil and dispersant. The impact of this perturbation on the two communities with different complexity was analysed both in terms of structure (as above) and functional level, through the analysis of oxygen uptake in the different communities. Although there was an indication that the oil had a depressing effect on the structure of both community types, it was not clear which species were most affected by the treatment. Individual comparisons between the two differently-structured treated communities and their controls were undertaken.

Computational Fluid Dynamics (CFD) is used in this study to assess the influence of temperature-dependent oil viscosity and density on the flow of oil up the well, and therefore the amount of insulation required. CFD is a difficult tool to apply to flows where the grid aspect ratio is as high as it needs to be to accommodate the full length of an oil well with a realistic number of grid points. Each model was therefore intensive in terms of computational effort and time. This study shows that by allowing oil viscosity and density to vary with temperature in a 2150 m vertical well with no insulation, the production output is significantly affected. The drop in production output is approximately 3% when oil viscosity varies with temperature, but when coupled with temperature-dependent density the loss in production increases to 22%. Ten CFD models, each with a different value of insulation heat transmission coefficient lying in the range 0.35 Wm^-2K^-1 to 16900 Wm^-2K^-1, are used to establish the temperature drop between riser inlet and outlet. The results obtained allow an operator to select an appropriate insulation based on the allowable temperature drop up the well, assuming all other properties are equal. The completion fluid region is situated outside the oil flow, tubing and insulation. The fluid is stationary which suggests that natural convection currents are present. Seven CFD models with annulus heights ranging from 1 m to 64 m are used to detect these currents, and assess the effectiveness of water as an insulating completion fluid. This thesis establishes that the natural convection currents do not split into multiple cells, but remain mono-cellular when the Grashof number is approximately 1x10⁸ and the Prandtl number is 2.3. This work also shows that heat loss due to natural convection from the completion fluid is an important contributory factor to the overall heat loss from a well, dependent on the well height.

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