Increased awareness of the effects of atmospheric pollution has meant that electrostatic precipitators, which have been used since the early part of this century to separate particulate matter from process gas streams, are now required to achieve particulate collection efficiencies in excess of 99.7% for a number of processes. Increasingly stringent legislation concerning industrial particulate emissions has challenged the precipitation industry to consider how equipment can be improved to reduce, in particular, heavy metal and respirable size particulate discharges. Electrostatic precipitators charge dust particles in a gas stream by corona-producing electrodes, and remove the charged particles by electrostatic attraction under high electric fields. This thesis details the development of a prototype high frequency (20KHz), high voltage (50kV), high power (25 kW) switched mode precipitator power supply with technological advances over conventional units. A high frequency, high voltage, high power precipitator supply using high frequency inverter technology coupled to a novel ferrite cored, high voltage transformer-rectifier unit has been designed and built. It is capable of delivering in a controlled and responsive way 25kW at 50kV into a load that may suffer from sparking and flashover. The developmental stages of the prototype from initial concept through to field trials of the supply at a power station in the UK are detailed.

No description available.

Carbon Capture and Storage (CCS) is recognised as one of a suite of solutions required to reduce carbon dioxide (CO2) emissions into the atmosphere and prevent catastrophic global climate change. In CCS schemes, CO2 is captured from large scale industrial emitters and transported, predominantly by pipeline, to geological sites, such as depleted oil or gas fields or saline aquifers, where it is injected into the rock formation for storage. The requirement to develop a robust Quantitative Risk Assessment (QRA) methodology for high pressure CO2 pipelines has been recognised as critical to the implementation of CCS. Consequently, failure frequency and consequence models are required that are appropriate for high pressure CO2 pipelines. This thesis addresses key components from both the failure frequency and consequence parts of the QRA methodology development. On the failure frequency side, a predictive model to estimate the failure frequency of a high pressure CO2 pipeline due to third party external interference has been developed. The model has been validated for the design requirements of high pressure CO2 pipelines by showing that it is applicable to thick wall linepipe. Additional validation has been provided through comparison between model predictions, historical data and the existing industry standard failure frequency model, FFREQ. On the consequences side, models have been developed to describe the impact of CO2 on people sheltering inside buildings and those attempting to escape on foot, during a pipeline release event. The models have been coupled to the results of a dispersion analysis from a pipeline release under different environmental conditions to demonstrate how the consequence data required for input into the QRA can be determined. In each model both constant and changing external concentrations of CO2 have been considered and the toxic effects on people predicted. It has been shown that the models can be used to calculate safe distances in the event of a CO2 pipeline release.

No description available.

Contaminated land is a global problem. Where it presents an unacceptable risk to receptors such as human health or ecosystems, remediation actions must be taken. Current remediation technologies can be ineffective due to mass transfer limitations. A typical scenario where these limitations control remediation efficacy is a physically heterogeneous aquifer where hydraulic conductivity (K) varies spatially. Under these conditions remediation is limited by solute migration across K boundaries. This thesis couples two remediation technologies, in situ bioremediation and electrokinetics (EK), to overcome the mass transfer limitations presented by physically heterogeneous settings. Bioremediation is the transformation of contaminants into less harmful substances by microorganisms; and EK is the application of a direct current to initiate certain transport processes independent of K. Where bioremediation is limited due to the influence of physical heterogeneity, EK transport processes could be applied to initiate an additional flux of solutes across K boundaries. This thesis investigates the influence of physical heterogeneity on EK migration of an amendment designed to enhance bioremediation. The research presented in this thesis advances the current state of knowledge for EK-BIO applications both at the fundamental level and field-scale using laboratory and desk based studies respectively. Laboratory apparatus was designed and built to accommodate physical heterogeneity, electrokinetic transport of solutes and contaminant biodegradation. Broadly, two types of EK experiment were conducted. Firstly, EK amendment migration under abiotic conditions on different arrangements of physical heterogeneity. Secondly, experiments in the same laboratory setup that introduced contaminant and microbial variables. From these experiments a conceptual framework is developed that describes the influence of physical heterogeneity on the EK transport of an amendment. It relates the spatial change in material properties associated with physical heterogeneity with aspects of EK application, such as the voltage gradient, and observes the implications for amendment transport. For example a layered contrast in material type generated a non-uniform electric field when direct current was applied, this led to non-uniform EK transport of the amendment relative to homogeneous settings. When contaminant and microbial variables were introduced to the experimental setup a greater understanding of EK-BIO applications to physically heterogeneous settings was gained. These experiments highlight and discuss the technical issues applying EK to enhance bioremediation by amendment addition versus contaminant removal by EK induced pore fluid movement. Desk based studies included a review of EK-BIO literature and a sustainability assessment that considered EK-BIO at the field scale. The review summarises the practical aspects of the technology in applications to natural environments. It notes that numerous limitations exist to EK-BIO applications in these settings but that there are many different implementation methods that can mitigate these effects. The sustainability assessment compares EK-BIO with conventional remediation technologies against specific criteria for a complex site contaminated with BTEX and MTBE. EK-BIO compares well to other technologies however characteristics of the site will determine the potential sustainability benefits of applying EK.

Radioactive barium sulphate scales raise a serious concern in the oil and gas industries. They are often classified as low level radioactive waste, but there are no clear methodologies established world widely to deal with this well know issue. The present study investigates a potential use of composite cement systems based on Portland cement to encapsulate the barium sulphate scales, aiming to provide a feasible option for safe handling, storage and disposal. The investigation was conducted on three different aspects: basic formulation, wasteform development and potential use as a high density support matrix. The first part studied the basic formulation to clarify the impact of BaSO4 loading and water contents on the physical properties of the composite cementing system. Fine BaSO4 powders and excess water were found to influence the product phases whereas coarse BaSO4 particles showed larger impact on strength of the products. The second part investigated the effect of mineral admixtures to develop practical wasteform formulations. Fine BaSO4 powder, metakaolin and quartz were found to improve the workability of the pastes as well as the microstructure by eliminating highly porous interfacial transition zone, resulting in the higher compressive strength and reasonable leaching rates of elements. Addition of quartz was found to be most effective to minimise the degradation caused by the high temperature environment, by initiating the formation of stable tobermorite phase.

One of the major problems with process equipment/systems set up in Nigeria is the lack of sustained productivity, arising from the basic inappropriateness of such equipment/system to the technological level of the country. The pollutions arising from the Oil & Gas exploitation activities in the Niger Delta were highlighted. In this project, the development of a unique processing system capable of advantageously treating oil contaminated soils and sludges in the Niger Delta was undertaken. The specific constraints in that terrain are outlined. The treatment systems that are currently available worldwide which are applicable to the Niger Delta have various limitations. The system designed had to be able to overcome all those limitations. Design superiority and success in the market place being two desirable aspects of a product, the project focused on the possibility of processing the contaminated materials at a higher rate without compromising quality. The need to generate its own fuel for firing burners and diesel for firing the electricity generators was one of the main drivers for the project. The system developed was tested at pilot level for effectiveness in those key areas. A totally energy-independent process has thus been created, which generates energy for the material being treated. This will guaranty the success in the market place in treating the contaminated sites of the Niger Delta, at commercial rates that are about a third of the current rates in the region. It is also estimated that capital and operating costs will be less than half of foreign built units, which ensure faster attainment of breakeven point. The future work that could be undertaken in this area include the field trials of a mini-sized processing unit and the eventual translation of processing parameters and information into a life size, commercial system able treat materials as required.

One promising proposal to mitigate the effect of climate change as a result of high atmo- spheric CO2 concentrations is carbon capture and storage. Deep saline aquifers provide the most storage capacity for CO2 storage. However, their geological characteristics are often poorly defined, which makes it difficult to design CO2 sequestration operations. This thesis considers how CO2 sequestration can be performed effectively and efficiently under geological uncertainty by allocating injection rates among injectors to maximise economic performance criteria and simultaneously minimise the risk of CO2 leakage. To this end, we consider the following four challenges in this thesis. 1.) Optimisation of CO2 injection strategies is a time-consuming operation since it re- quires multiple evaluations of expensive black-box functions. This computational cost increases rapidly when accounting for the impact of geological uncertainty. In this thesis, we propose the use of adaptive sparse grid interpolation (ASGI) to speed up the CO2 optimisation process. Based on numerical results, the ASGI is an efficient surrogate technique and will be used throughout the thesis. 2.) Injection designs for CO2 sequestration is difficult when the geology of the storage formation is not well-defined. In the thesis, we propose a utility function to find the injection strategy that is insensitive to the impact of geological uncertainty. Numeri- cal results show potential benefits of using the utility function for the optimisation of CO2 under geological uncertainty. 3.) Optimisation of CO2 sequestration for several conflicting criteria is a challenging task. In the thesis, we use a non-dominated sorting genetic algorithm (NSGA-II) coupled with the ASGI surrogate to maximise both economic performance and sweep efficiency of CO2 flooding while simultaneously minimising the risks of CO2 leakage. Solutions obtained from the NSGA method help decision makers to manage multiple conflicting criteria for CO2 sequestration. 4.) The ASGI surrogate is an efficient surrogate-assisted optimisation technique for a small to moderate number of input variables, but for problems with 10s of control parameters, it suffers from the curse of dimensionality - the computational time increases exponentially with the number of input variables. In the thesis, we develop a high-dimensional model representation (HDMR) technique to efficiently map the input-output relationship of a function. Several numerical examples show that the HDMR approach is suitable for CO2 storage optimisation with many input variables.

Zero-valent iron nanoparticles (nano-Fe0) have proved effective at the remediation of pollution in environmental settings. However, the Royal Society has advised the UK government to prohibit the release of these particles, due to concerns over the safety of the particles in relation to their reactive timeframe, and their final state post-utilisation. The following work aimed to address these concerns, by performing experiments that studied the interaction of nano-Fe0 with common groundwater anions and contaminants. As determined by X-ray diffraction and X-ray photoelectron spectroscopy analysis, ageing of nano-FeD in both simple and more complex geochemical solutions produced the iron (hydr)oxide forms of magnetite/maghemite (Fe304/y-Fe2O3), lepidocrocite (y-FeOOH) and goethite (a-FeOOH); biogenic nanoparticulate forms of all detected iron compounds have been identified in nature. In chemically simple solutions, goethite was inferred to be the final state of the corrosion serie.s. However, after four months aqueous exposure, this was not the sole form of iron. This indicated that the transformation process take place over a matter of months or years, rather than days. Further work suggested that more crystalline nano-FeD, e.g. produced by hydrogen reduction would have a considerably extended reactive longevity in ~he environment as compared to the more reactive nanoFeD produced using borohydride reduction. Using inductively coupled plasma-mass and - optical emission spectroscopy, increasing corrosion was shown to have a negative impact on nano-FeD reactivity; metal uptake rates decreased with increased oxidation. Metal contaminants when not incorporated into the iron nanopartic1e structure, i.e. when simply reduced or complexed on the surface, are very susceptible to remobilisation. This process was ascribed principally to the loss of the particle's zero-valent core rather than surface stoichiometry or geochemical conditions; hence, these require electron transfer to remain associated with the nanoparticle surface. Anions at concentrations found in natural waters have a significant influence on the transformation of zero-valent iron nanopartic1es, with chloride, sulphate, and most significantly, bicarbonate accelerating the corrosion of nano-FeD compared to an anion free solution. Furthermore, the anions sulphate and chloride accelerated desorption of adsorbed metals from the nanoparticle surface. Conversely, nitrate was found to encapsulate any associated metals in a magnetite/maghemite shell, which could be utilised for the long-term capture of metal contaminants. The complex influence of anions on the corrosion and reactivity of nano-Fe0 was corroborated by results from a field trial with uranium-contaminated natural waters. To conclude, this PhD used numerous analysis techniques to determine the fate and reactivity of nano-FeD when exposed to an aqueous environment. This work clearly demonstrates that solution composition has a significant impact on the performance of nano-FeD, and emphasises the importance of performing pilot studies in analogous conditions before the particles are deployed on site.

Especially in proximity to metal smelters, heavy metal concentrations are high in the soil and the risk of heavy metal exposure is unneglectable. Therefore, an efficient removal of heavy metals from flue gases is essential. This thesis aim is to remove low concentrations of heavy metals from the flue gas. In order to achieve a high capture efficiency with a high flow rate of the flue gases, supported ionic liquid phases are used. For a pre-selection of suitable ionic liquids, the solubility of heavy metal oxides were screened in several ionic liquids. The best arsenic oxide solubility was observed in ionic liquids with Lewis basic anions. The solubility of arsenic(III) oxide and arsenic(V) oxide in ionic liquids with carboxylate anions decreases with increasing hydrophobicity. The arsenic(III) oxide solubility in phosphonium and ammonium chlorides increased with increasing hydrophobicity. In the solution arsenic(V) oxide, arsenic is present as arsenate anions. An equilibrium of arsenite and arsenate was found for arsenic (III) oxide in acetate containing ionic liquids and chloride - arsenic complexes are postulated in phosphonium chlorides. The highest lead(II) oxide solubility was observed in phosphonium chlorides, phosphonium bromides and imidazolium carboxylates. In the solution, lead is most likely present as anionic lead(ll) hydroxides. In the mixtures of selenium(IV) oxide and several ionic liquids, reduction of selenium(IV) to elemental selenium or H2Se occurs. In the solution, selenium might be present as selenite anions, or SeO2-ionic liquid cation or SeO2-ionic liquid anion complexes. The results of this thesis indicate, that it is possible to capture heavy metals from the gas phase more efficiency with SILP than uncoated activated carbon. [P6 6 6 14]CI coated on activated carbon was identified as the most efficient materials studied in this thesis to capture arsenic from a lead blast furnace flue gas stream (Umicore, Hoboken, Belgium).