This thesis describes the development and extensive testing of a numerical CFD model and a semi-analytical homogenous flow model for simulating the transient outflow following the failure of pressurised pipelines transporting hydrocarbon mixtures. This is important because these pipelines mainly convey highly flammable pressurised and hazardous inventories and their failure can be catastrophic. Therefore an accurate modelling of the discharge rate is of paramount importance to pipeline operators for safety and consequence analysis. The CFD model involves the development of a Pressure-Entropy (P-S) interpolation scheme followed by its coupling with the fluid flow conservation equations using Pressure (P), Entropy (S), Velocity (U) as the primitive variables, herewith termed as the PSUC. The Method of Characteristics along with the Peng Robinson Equation of State are in turn employed for the numerical solution of the conservation equations. The performance of the PSUC is tested against available experimental data as well as hypothetical test cases involving the failure of realistic pipelines containing gas, two-phase and flashing hydrocarbons. In all cases the PSUC predictions are found to produce reasonably good agreement with the published experimental data, remaining in excellent accord with the previously developed but computationally demanding PHU based CFD model predictions employing Pressure (P), Enthalpy (H) and Velocity (U) as the primitive variables. For all the cases presented, PSUC consistently produces significant saving in CPU run-time with average reduction of ca. 84% as compared to the previously developed PHU based CFD model. The development and extensive testing of a semi-analytical Vessel Blowdown Model (VBM) aimed at reducing the computational run-time to negligible levels is presented next. This model, based on approximation of the pipeline as a vessel discharging through an orifice, handles both isolated flows as well as un-isolated flows where the flow in the pipeline is terminated upon puncture failure or at any time thereafter. The range of applicability of the VBM is investigated based on the comparison of its predictions against those obtained using the established but computationally demanding PHU based numerical simulation. The parameters studied to perform testing the applicability of the VBM include the ratio of the puncture to pipe diameter (0.1 – 0.4), initial line pressure (21 bara, 50 bara and 100 bara) and pipeline length (100 m, 1 km and 5 km). The simulation results reveal that the accuracy of the VBM improves with increasing pipeline length and decreasing line pressure and puncture to pipe diameter ratio. Surprisingly the VBM produces closer agreement with the PHU based CFD predictions for two-phase mixtures as compared to permanent gases. This is shown to be a consequence of the depressurisation induced cooling of the bulk fluid which is not accounted for in the VBM. Finally, development and testing of the Un-isolated Vessel Blowdown Model (UVBM), as an extension of the VBM accounting for the impact of initial feed flow and fluid/wall heat transfer during puncture is presented. The performance of the UVBM is tested using a 10 km pipeline following a puncture along its length considering three failure scenarios. These include no initial feed flow, cessation of feed flow upon failure and its termination at any set time thereafter. For the ranges tested, the VBM and UVBM are shown to present considerable promise given their significantly shorter computational run-time compared to the PHU based numerical technique whilst maintaining the same level of accuracy.

Solar water splitting using an inorganic semiconductor photocatalyst is viewed as one of the most exciting and environmentally friendly ways of producing clean renewable fuels such as hydrogen from abundant resources. Currently, there are many diverse semiconductors that have been developed, the majority for half reactions in the presence of sacrificial reagents. However, for industrial facilitation, there exists an essential, non-debatable trifecta of being robust, cheap and efficient for overall water splitting. To date, no system has combined all three, with most examples missing at least one of the necessary trio. Therefore one of the current challenges of the field is to develop low cost, highly efficient and stable photocatalysts for industrial scale-up use. In order to achieve that aim, researchers must focus on novel semiconductors to improve efficiencies and also understand the fundamental mechanisms. The primary focus of this thesis then, is to investigate some of the newest photocatalysts for water photooxidation, reduction, and overall water splitting. In doing so, the thesis aids to shed light on the mechanisms behind what makes certain photocatalysts either efficient or inefficient. Firstly, test station was set up to analyse gaseous products such as hydrogen and oxygen produced from photocatalytic water splitting, by using a custom made high purity borosilicate reactor in conjunction with a gas chromatography unit. Gaseous products could be measured with very small sampling error (<1%), which improved the throughput of experiments. The photooxidation of water using a novel faceted form of Ag3PO4 was investigated. A novel synthetic method was created that made it possible to control the exposing facets of silver phosphate in the absence of surfactants to yield tetrahedral crystals composed entirely of {111} facets. It was found that due to high surface energy of {111}, and low hole (h+) mass in the 111 direction, Ag3PO4 tetrahedral crystals could outperform all other low index facets for the oxidation of water under visible light. The quantum yield was found to be nearly unity at 400 nm, and over 80% at 500 nm. With the exception of Ag3PO4 tetrahedral crystals, no photocatalyst has exhibited quantum efficiencies reaching 100% under visible irradiation. Therefore, the strategy of morphology control of a photocatalyst, led by DFT calculations of surface energy and charge carrier mobility, in order to boost photooxidation yield has been demonstrated to be very successful, and could be applied to improve other semiconductors in future research. Hydrogen production from water was further studied using the only known robust organic photocatalyst, graphitic carbon nitride (g-C3N4). It was discovered that using a novel preparation method, urea derived g-C3N4 can achieve a quantum yield of 26% at 400 nm for hydrogen production from water; an order of magnitude greater than previously reported in the literature (3.75%). The stark difference in activity is due to the polymerisation status, and consequently the surface protonation status as evidenced by XPS. As the surface protonation decreases, and polymerisation increases, the performance of graphitic carbon nitride for hydrogen production increases. The rate of hydrogen production with respect to BET specific surface area was also found to be non-correlating; a juxtaposition of conventional photocatalysts whose activity is enhanced with larger surface areas - believed to be because of an increase in surface active sites. Finally, overall water splitting was probed using Z-scheme systems comprising of a redox mediator, hydrogen evolution photocatalyst, and oxygen evolution photocatalyst. Ag3PO4 was found not be not suitable for current Z-scheme systems, as it is unstable in the pH ranges required, and also reacts with both of the best known electron mediators used in Z-schemes, as evidenced by XRD, TEM, and EDX studies. However, it has been demonstrated that urea derived g-C3N4 can participate in a Z-scheme system, when combined with either WO3 or BiVO4 – the first example of its kind, resulting in a stable system for an overall water splitting operated under both visible light irradiation and full arc irradiation. Further studies shows water splitting rates are influenced by a combination of pH, concentration of redox mediator, and mass ratio between photocatalysts. The solar-to-hydrogen conversion of the most efficient system was experimentally verified to be ca. 0.1%. It is postulated that the surface properties of urea derived graphitic carbon nitride are related to the adsorption of redox ions, however, further work is required to confirm these assumptions.

The development and testing of a fluid-structure interaction model for simulating the transition of an initial through-wall defect in pressurised CO2 transmission pipelines employed as part of the carbon capture and storage chain into running brittle fractures is presented. The model accounts for all the important processes governing the fracture propagation process including the fluid/wall heat transfer, the resulting localised pressure stresses in the pipe wall as well as the initial defect geometry. Real fluid behaviour is considered using the modified Peng Robinson equation of state. Hypothetical but nevertheless realistic failure scenarios involving the transportation of gas and dense phase CO2 using existing natural gas steel pipelines are simulated using the model. The impacts of the pipe wall thickness, Ductile-Brittle-Transition Temperature (DBTT), initial defect geometry, feed temperature, stream impurities, surrounding backfill as well as flow isolation on brittle fracture propagation behaviour are investigated. In all circumstances, the initial defect geometry in the pipeline is shown to have a major impact on the pipeline’s propensity to brittle fracture propagation. For example, in the case of an initial through-wall defect in the form of a circular puncture where there is no stress concentration, fracture propagation is highly unlikely. The opposite applies to an elliptical through-wall defect embodying a hairline crack extending from its side. Furthermore, gas-phase CO2 pipelines are more prone to brittle fracture failures as compared to dense-phase CO2 pipelines despite the higher starting pressure. This is due to the higher degree of expansion-induced cooling for gaseous CO2. The emergency isolation of the initial flow in the pipeline following the formation of the initial defect promotes brittle fracture. For the ranges tested, typical CO2 stream impurities are shown to have negligible impact on brittle fracture behaviour. Puncture in a buried pipeline where there is no blowout of the surrounding soil is more likely to lead to brittle facture propagation as compared to that for an exposed pipeline. This is due to the secondary cooling of the pipe wall by the surrounding soil cooled by the escaping gas.

Advances in the field of microreaction technology offer the opportunity to combine the benefits of continuous processing with the flexibility and versatility desired in the pharmaceutical and fine chemicals industry. Microreactor devices, also offer their own unique advantages over traditional continuous processing, such as improved heat and mass transfer, safer handling of exothermic reactions and easy containment of explosive and toxic materials. A reaction system can be quickly scaled-up to production levels by increasing the number of units operating in parallel, allowing significant savings in time and R&D costs. Most studies of microreactor systems to date focus on the development and performance of individual microdevices. However, a top down approach is preferred, with the focus on the requirements of the process and a suitable device design derived to meet those requirements. This work aims to demonstrate the suitability of the poly-L-leucine catalysed asymmetric epoxidation of chalcone reaction for continuous processing as well as the process and choices of designing and scaling a microchemical system. A suitable continuous reaction protocol was established for this reaction system, achieving a conversion of 88.4 % and enantioselectivity of 88.8 %. Mixing was found to be critical due to the low diffusivity ( 10"u) of the polymeric catalyst. Design criteria were established and a microstructured reactor with a footprint of 110 mm x 85 mm and production rate of - 0.5 g/day was designed for the system. An external scale-out structure was selected. The staggered herringbone mixer was selected for enhancing the mixing in the microstructured reactor. A method for characterizing the mixing performance in the staggered herringbone mixer based on stretching computations using particle tracking methods was developed, which allowed the required mixer length to be derived directly. Mixer lengths of 40 mm were provided for both deprotonation and epoxidation mixers. The effects of varying operating temperature, residence time and reactant concentrations on reaction performance in the fabricated microstructured reactor were investigated. The base case condition (13.47 g/1 PLL, 0.132 mol/1 H202, 0.0802 mol/1 chalcone, 0.22 mol/1 DBU) was found to be optimal, achieving a conversion of 86.7 % and enantioselectivity of 87.6 %. Several unexpected phenomena such as bubble clogging and increased viscosity due to the polymeric catalyst were encountered. A scaled-out system was designed and experiments carried out. Flow maldistribution, attributed to fabrication errors and bubble clogging, resulted in poor reaction performance (conversion -31.4 % and enantioselectivity 82.7 %) due to unequal residence times and imperfect mixing ratios of reactants. The commercial potential of the research was evaluated. Micro and macro level analysis of the market and industry were favourable and a suitable commercialisation route was suggested.

Multivariate statistical modelling and monitoring is an active area of research and development in both academia and industry. This is due to the economic and safety benefits that can be attained from the implementation of process modelling and monitoring schemes. Most industrial processes in the chemistry-using sector exhibit complex characteristics including process dynamics, non-linearity and changes in operational behaviour which are compounded by the occurrence of non-conforming data points. To date, modelling and monitoring methodologies have focussed on processes exhibiting one of the aforementioned characteristics. This Thesis considers the development and application of multivariate statistical methods for the modelling and monitoring of the whole process as well as individual unit operations with a particular focus on the complex dynamic nonlinear behaviour of continuous processes. Following a review of Partial Least Squares (PLS), which is applicable for the analysis of problems that exhibit high dimensionality and correlated/collinear variables, it was observed that it is inappropriate for the analysis of data from complex dynamic processes. To address this issue, a multivariate statistical method Robust Adaptive PLS (RAPLS) was proposed, which has the ability to distinguish between non-conforming data, i.e. statistical outliers and a process fault. Through the analysis of data from a mathematical simulation of a time varying and non-stationary process, it is observed that RAPLS shows superior monitoring performance compared to conventional PLS. The model has the ability to adapt to changes in process operating conditions without losing its ability to detect process faults and statistical outliers. A dynamic extension, RADPLS, using an autoregressive with exogenous inputs (ARX) representation was developed to model and monitor the complex dynamic and nonlinear behaviour of an Ammonia Synthesis Fixed-bed Reactor. The resultant model, which is resistant to outliers, shows significant improvement over other dynamic PLS based representations. The proposed method shows some limitations in terms of the detection of the fault for its full duration but it significantly reduces the false alarm rate. The RAPLS algorithm is further extended to a dynamic multi-block algorithm, RAMBDPLS, through the conjunction of a finite impulse response (FIR) representation and multiblock PLS. It was applied to the benchmark Tennessee Eastman Process to illustrate its applicability for the monitoring of the whole process and individual unit operations and to demonstrate the concept of fault propagation in a dynamic and nonlinear continuous system. The resulting model detects the faults and reduces the false alarm rate compared to conventional PLS.

Aerosol are ubiquitous in many areas of scientific interest. They are employed in industrial techniques such as spray drying and fuel injection, in medicine to deliver drugs to the lungs, and play an important role in the atmosphere due to their interaction with radiation and their influence on clouds. A characterisation of the properties and processes common to aerosol in all these fields is facilitated by measurements on single droplets, free of the complicating particle-particle interactions of an aerosol ensemble. This thesis describes a laboratory-based approach to explore the thermodynamic properties and kinetic processes which influence the rate of evaporation and condensation mass transport of volatile and semi-volatile species in aerosol. A new implementation of an electrodynamic balance CEDB), consisting of cylindrical electrodes, was used to tightly confine single aerosol droplets in an electric field . Coupled with elastic light scattering methods, the time-dependence of the radius of droplets undergoing evaporation and condensation was determined. A method for conducting comparative measurements of the evaporation of droplets with different compositions in the EDB was developed, allowing evaporation kinetics to be interpreted with unprecedented accuracy Evaporation measurements were used to determine thermodynamic equilibrium properties of droplets, such as the saturation vapour pressure and hygroscopicity The influence of kinetic limitations in the bulk-condensed phase were investigated, showing that significant slowing of evaporation and condensation occurs under conditions where highly viscous condensed states develop. The influence of interfacial transport kinetics were explored for pure water surfaces and surfactant coated surfaces, demonstrating conclusively that significant limitations to evaporation are only encountered when condensed films form at the surface.

The research associated with this work centres on the development and synthesis of selective ionophores that are capable of detecting potassium phosphate ions in aqueous solutions. This specific detection of K+ ions that are bound to a phosphate ion is crucial because both ions play a leading role in water pollution. This work describes a K+ ion-sensing system using a potentiometric method based on macro cyclic compounds. This thesis consists of six chapters. Chapter one includes a short history and introduction of the electrochemical sensors with a description of macrocyclic compounds as ionophores which are related to this thesis work. The second chapter describes the experimental techniques which have been used to synthesize the target compounds including single-crystal X-ray structural analysis. Synthesis a novel ionophore ((((3,4,5-trinitro-l,2-phenylene)bis(oxy))bis(ethane-2,1- diyl))bis(oxy))bis(ethane-2,1-diyl) dinitrate based on open ring macrocyclic compound structure and the synthesis and performance of ten ionophores for the electrode potentiometric applications within a PVC membrane is conveyed in chapter three. The characterisations of the those ionophores are reported including FT -IR data, lH NMR,13C NMR, HSQC NMR, 2D NMR including COSY NMR, Mass spectrometry, and single-crystal X-ray structural analysis for confirming the closing ring structures. Those ionophores are 4-nitro benzo-15-crown-5 (1), 4-amino benzo-l5- crown-5 (3), dinitro benzo-15-crown-S (2), diamino benzo-l5-crown-5 (4), 4- nitro benzo-18-crown-6 (5), 4-amino benzo-18-crown-6 (8), dinitro benzo-18-crown- 6 (6), diamino benzo-18-crown-6 (9), dinitro dibenzo-18-crown-6 (7), diamino dibenzo-18-crown-6 (10). In addition to that another five ionophores have been applied within a PVC membrane which there were l-aza-18-crown-6, benzo-l5crown- S, benzo-18-crown-6, dibenzo-18-crown-6, and dicyc1ohexyl-18-crown-6 is reported in this chapter. The ability to synthesis these ionophores are important to enable a review of the effects of both the ring size and the associated functional groups. Chapter four describes the data of the effect of a range of plasticisers for incorporating the ionophores into the membrane for optimum sensor design. Those plasticisers are dibutyl phthalate, 2- nitrophenyl phenyl ether, dioctyl phenyl phosphonate, dioctyl phthalate, and bis (2-ethylhexyl) adipate. The thermal properties of all blends are studied by TG/DSC. The assessment of the designed electrode is applied in chapter five which includes the modified electrodes with the ionophores dibenzo-18-crown-6 proving to be the most effective with a shelf life of 40 days; this ensemble also showed negligible drift. It responded in a near Nernstian fashion, and showed a low detection limit of 3.2 xlO-6 mol L-1 , and a fast response time of 30 seconds over a concentration range of 5 x 10-5 mol L-1 to 1 x 10-1 mol L-1 . The morphologies of the sensor after using it is studied by imaging of the sensor in scanning electron. While the energy-dispersive X-ray spectroscopy is used' to gather data about the elemental composition of the samples' surface. X-rays, which are characteristic for different elements and a composition spectrum is produced. Finally, chapter six includes conclusions of the thesis work which involves that the resulting electrode signifies a significant advancement in the construction of a potentiometric device for the determination of potassium phosphate concentrations in solution and suggestions for future work.

No description available.

Organic light emitting diodes are polymer-based devices which promise higher efficiency and lower cost than other lighting devices, and will enable new applications which were not previously possible. An important component of OLEDs is the transparent conducting electrode (TCE), which is commonly indium tin oxide (ITO). It has a low sheet resistance (15 OD) and a high transmission (87 % on average in the visible wavelength range). However, it is also brittle, expensive and has issues from indium and oxygen migration into the polymer layers of the OLED. There are many alternatives that have been proposed to ITO, one of which is a nanometre thin metal grid. It has been shown to be flexible and if a cheap metal is used, then it can be a low cost solution. The sheet resistance can reach very low levels (e.g. 1 OD), and the transmission can be above 90 %. In this thesis, a thorough study is undertaken to investigate how the grid TCE affects the OLED. The grid TCE was optimised using a computer simulation. Then OLEDs were fabricated on them and characterised to investigate how their performance varies as the grid thickness increases. Surprisingly, it was concluded that the best TeE does not make the best OLED. Several possible reasons for this were considered. Grids with different line spacings were also tested and it was found that if the line spacing was too large, the light emission would not be uniform. To overcome this problem, small spacing grids or hybrid grid TCEs consisting of the metal grid and poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS) PHIOOO, or regioregular poly(3-hexythiophene) (P3HT) wrapped single-wall carbon nanotubes, were used. The OLEDs fabricated on the hybrid grid OLEDs had a luminance as high as the ITO OLED. These results demonstrated the feasibility of thin metal grids as an alternative for ITO, and will lead to better grid TCE design and optimisation for use in OLEDs.

In this project, the concept of employing liquefied gas compounds as draw agent has been investigated among 137 gaseous compounds by determining their high solubility in water, the resulting osmotic pressure and their re-generation through thermal-depression methods. The screening process resulted in an organic liquefied gas draw solution suitable for Forward Osmosis desalination process. This is a polar, non-ideal with partially miscibility under 4 bars external pressure generates an osmotic pressure at maximum solubility (34% weight percentage) of 220 bars which is seven times more than seawater osmotic pressure. In addition, there is a significant reduction in solubility of the liqefied gas in water when the external pressure on draw solution is reduced from 4 bars to atmospheric pressure. This suggests that the liquefied gas draw agent could be separated from the solution by depression – thermal processes such as gas striping or atmospheric-vacuume flash methods. The performance of FO process using the novel liquefied gas draw solution was simulated using Excel software to achieve optimum operating conditions including operating temperature, cross flow rate and draw solution concentration. The results showed that the draw solution side should be kept under a pressure of maximum 10 bars. This depends on the operating temperature to dissolved the liquefied gas in water as much as possible. However, the operating pressure of the feed side could vary to cover a range 1 bar to 10 bar. Furthermore, the feasibility of the integrated Forward Osmosis process and depression - compression methods for seawater desalination was investigated in terms of estimating the specific energy consumption (SEC) using HYSYS 7.2 simulation software. The specific energy consumption (SEC) was predicted at optimum operating conditions resulting from FO process simulation based on the production of 1m3/h of potable water from seawater at a recovery rate of 50%. The electrical energy requirement of the process was calculated and the result of simulation was compared to the energy requirement of current desalination technologies. Energy saving of the novel FO desalination process is projected to range from 30% to 60%. The estimated SEC of the present FO desalination process was 2.7kWh/m3 and could be decreased to 0.5kWh/m3 when a heat recovery process is used. The results presented in this project demonstrate that the proposed novel forward osmosis desalination process with thermal-depression regeneration using the liquefied gas draw solution is a feasible and cost-effective desalination method. The novel draw agent produces high osmotic pressure and can be easily separated from the product clean water by using low-pressure steam with temperature input less than 150°C. While the feed water recovery in the FO process is higher than other desalination methods, the specific energy consumption of this novel FO desalination process is significantly low. The future works should focus on experimental tests to measure the osmotic pressure, permeated water flux, reverse draw agent flux and energy consumption in a bench scale or a pilot unit studies. A patent application, based on the present process, has recently been filled at the UK patent Office and the application number is GB1321711.2 (Adel Sharif and Maryam Aryafar, A novel Forward Osmosis Desalination process, GB1321711.2, 2013).