PhD, EngD and MSc by research theses (SWEE)
Permanent URI for this collection
Browse
Recent Submissions
Item Open Access Investigation of the Effect of Sand on Annular Flow Behaviour in Horizontal Pipes(Cranfield University, 2017-10) Osokogwu, Uche; Falcone, GioiaAnnular flow is encountered in petroleum production systems, where reservoir fluids are conveyed to surface via wells and transport lines and also nuclear power plants, chemical and refining processes (e.g. reactors, heat exchangers). In this type of flow regime, the gas, together with the entrained liquid droplets, flows within the core of the pipe at high velocities, while the liquid flows as a film along the pipe walls. Experimental investigations on annular flow behaviour, sand transport and its effect on annular flow in horizontal pipe are presented, with the aim of progressing the understanding of such flow and facilitate the optimum design of hydrocarbon production systems. The experiments were conducted using a closed-loop horizontal pipe with an internal diameter of 2-inch (0.0504m). The experiments could be categorized into: water/air flow, water/sand flow, water/air/sand annular flow and sand sampling. The water/air flow experiments could be subdivided into water/air flow (Plug, Slug, Stratified-smooth and stratified-wavy flows) and water/air annular flow. The results of water/air flow were plotted on flow regime map to aid the recognition of the different flow regimes. For the water/air annular flow experiments, key flow features are presented, with discussion on liquid hold up, film thickness, wave frequency and pressure gradient. The water/sand flow experiments investigated sand saltation, sand streaks, moving dunes and sand beds. Also, sand particles of 212microns and 500microns for water/air/sand annular flow were investigated. Similarly, sand sampling experiments were also carried out. The OLGA dynamic multiphase flow simulator was run against the experimental results. The OLGA simulations of the water/air annular flow shows a better liquid hold-up match at lower superficial liquid velocities. For sand transport, OLGA also identified sand flow in annular flow as no bed. The main contributions of this study are: presenting the minimum transport velocities for water/sand flow in horizontal pipe. For water/air annular flow, the contributions are: detailed annular flow behaviours in horizontal pipes with annular-wavy slug flow at low superficial liquid and gas velocities, and full symmetrical annular flow from superficial gas velocity of 12m/s at low Vsl. The study proves that superficial liquid velocity has impact and significance on wave frequency: This has refuted Setyawan et al., (2014), whose report presented superficial liquid velocity to be insignificant in wave frequency. The study also identified that the higher the Vsl, the higher the interfacial shear stress but the lower the wave velocity. Also, the higher the Vsl, the higher interfacial friction factor/shear stress, but the lower the wave frequency. For water/air/sand annular flow, this study identifies saltation and suspension as the two main sand distribution in annular flow, with small-size particles being transported at the gas core and the bigger particles at the bottom (i.e. in the liquid film) along in the horizontal pipes. Finally, sand particles’ size does not appear to have an impact on wave velocity and wall shear stress, while sand concentration affects wall shear stress, but not wave velocity. Lastly, presence of sand particles in the liquid film is associated with increase in wave amplitude in annular flow, as more energy is being dissipated from the gas phase to keep the waves in motion.Item Open Access Comparison of advanced oxidation processes for metaldehyde removal and downstream disinfection by-product formation(Cranfield University, 2017-09) Diana, Marine; Jarvis, Peter; Hassard, FrancisMetaldehyde is the pesticide that has been found to exceed the maximum regulatory concentration of 0.1 µg/L in drinking water the most in the UK in recent years. As a result of the pesticide not being removed by conventional water treatment processes, there has been an interest in alternative treatments including advanced oxidation processes (AOPs). The latter have been reported as promising technologies for the removal of recalcitrant micropollutants. A large scale pilot study was carried out to compare the performance of two different AOPs for removing metaldehyde from sources used to produce drinking water: the UV/H₂O₂ AOP and O₃/H₂O₂ followed by UV/H₂O₂ AOP. Since AOPs can increase the formation of disinfection by-products (DBP) under certain oxidation conditions, it is important to assess their impact on DBP precursors. For this purpose, the trihalomethane formation potential (THM FP) and the haloacetic acid formation potential (HAA FP) were measured upon chlorination of samples collected at different stages of the treatment. Both AOPs were shown to remove metaldehyde efficiently achieving removals of up to 98%. They were able to reduce metaldehyde concentration below the regulatory level with UV doses lower than 1 kWh/m³ for initial metaldehyde concentrations of up to 2.10 µg/L. Concentrations as high as this value can be found in sources used to produce drinking water. The O₃/H₂O₂ - UV/H₂O₂ AOP was up to 33% more efficient than the UV/H₂O₂ AOP when applied at UV doses lower than 0.60 kWh/m3. In this work, the electrical energy applied to the system was expressed in kWh/m³ to enable the comparison of both AOPs at similar operating conditions. Both AOPs either increased or decreased the THM FP and the HAA FP between -85% and +155% with respect to the inlet. However, the quality of the inlet water better explained these changes rather than the UV and oxidant doses applied.Item Open Access Metaldehyde treatability by dissolved air flotation combined with powdered activated carbon adsorption(Cranfield University, 2017-12) Sanchez Lopez, Sara; Jarvis, Peter; MacAdam, JitkaThe removal of metaldehyde to meet pesticide compliance limits in drinking water remains a challenge for water companies. A combined treatment of dissolved air flotation (DAF) and powdered activated carbon (PAC) was investigated as a treatment process for metaldehyde removal. Four different water sources were spiked with metaldehyde and treated using PAC. A PAC dose of 100 mg/L using a contact time of 20 minutes was required in order to effectively remove metaldehyde to the compliance concentrations for all of the water sources. The water quality was shown to affect the removal of metaldehyde through competition with NOM. Moreover, the PAC dosing position relative to the coagulant was studied regarding its impact on the removal of NOM and metaldehyde, the floc formation and the clarification efficiency. The simultaneous addition of coagulant and PAC resulted in the lowest removal of metaldehyde. The best removal was seen for dosing sequences of PAC/Coagulant and Coagulant/PAC. However, there were no significant differences between these two approaches. The sequence of addition of PAC/Coagulant was selected due to its better clarification results.Item Open Access Managing life extension process for safety critical elements on offshore oil and gas installations(Cranfield University, 2017-05) Animah, Isaac; Shafiee, Mahmood; Simms, Nigel J.Life extension (LE) of Safety Critical Elements (SCEs) is one of the hottest topics in the offshore Oil and Gas (O&G) industry today. Although LE is considered as the most appropriate alternative among the end of life management strategies (EOMLS), there are still several challenges confronting asset managers during LE phase of operation. Key among these challenges includes; lack of integrated technical and economic approach to assess the current health conditions of SCEs for LE, over reliance on expert knowledge and experience for selecting the most suitable LE strategy and the lack of suitable approach to integrate all LE decision making elements for effective operations of SCEs. To overcome these challenges, this research aimed at developing an integrated decision making framework to use for managing LE process for SCEs found on offshore O&G installations. In order to overcome the first challenge, a techno- economic framework which integrates technical and economic assessment procedures for condition assessment of SCEs is developed. Furthermore, approaches based on Life Cycle Cost Benefit (LCCB) concept and Multi Criteria Decision Making (MCDM) method are subsequently proposed to overcome the challenge of lack of suitable methodology for selecting the most appropriate LE strategy. Lastly, a proposed multi-stage remanufacturing architecture capable of integrating all LE decision making elements is developed. These decision making models have been developed and analysed using data from literature review, expert opinion, review of company internal documents as well as data from manufacturers of SCEs in the offshore O&G industry. The models are validated with a number of real life case studies which involves water deluge system, industrial air compressors and three phase separation systems to ascertain their efficacy. The outcome of validation processes indicates that these decision making models provide cost effective solutions to overcome the three key LE challenges outlined in this study. This research has added to the scientific understanding of this research area through creation of novel decision making models to support LE phase of operation in the offshore O&G industry.Item Open Access Removal of micropollutants from wastewater combining adsorption and electrochemical regeneration(Cranfield University, 2017-05) Pizzagalli, Giulia; Campo Moreno, Pablo; Soares, AnaIncreasingly stringent legislations, such as the Water Framework Directive (WFD) and its daughter Directive on Environmental Quality Standards (EQS), have carried important implications for European policy on pollution control for water resources. EQS have been set or proposed for substances which hitherto had not been subjected to monitoring, calling for compliance assessments and new control measures. To address this challenge, the UK Water Industry Research (UKWIR) financed a Chemicals Investigation Programme (CIP), assessing the source, occurrence and removal of emerging pollutants in the final effluents of wastewater treatment works (WwTWs). A second phase of work, CIP2, now aims to create a justifiable base for future regulatory measures needed to achieve good status (i.e. compliance limits for specific substances), together with a data set on micropollutants’ concentrations from trials conducted at pilot and full scale all over the UK. As part of CIP2, the Arvia ODC (Organic Destruction Cell), a novel technology combining adsorption and electrochemical oxidation, has been investigated at pilot scale. Its overall performance was assessed by evaluating the removal of 68 emerging pollutants and priority substances (pharmaceuticals, steroids, industrial chemicals and heavy metals), by appraising its economic and environmental costs and by weighting its reliability, easiness of maintenance and operation. Overall, the unit was able to target pharmaceuticals better than any other class of substances, with removals consistently over 50% for the majority of them, being especially effective towards macrolide antibiotics (~ 60-70%) and statins (~70-80%). The majority of determinands (72%) were found to be at concentrations below the set EQS at discharge. However, despite some evidence of promising performance, the ODC appeared to promote the accumulation of metals (i.e. zinc, nickel) in the final effluent and overall showed quite a weak performance in relation to sanitary determinands. A multi criteria analysis was performed to compare the ODC to alternative tertiary treatments. Although considerably lower than alternative treatment technologies (i.e. GAC or ozonation), energy consumption, normalised at 0.14 kWh/treated m³, represented the major contributing factor to estimated OPEX (1.1 pence/kWh), steadily increasing with population served. The ODC does not require chemical dosing, thus lessening the sludge production and potentially offering lower operational carbon usage than other advanced oxidation processes. Further testing of the technology was carried on at bench scale, in order to assess the unit’s performance in more controlled circumstances (spiked tap water). The trial allowed to single out the main parameters (mainly current density and effluent flow) responsible for the ODC performance and to evaluate to what extent their variation contributed to the removal of carbamazepine, a pharmaceutical compound whose persistence and toxicity in the aquatic environment determined its inclusion in the list of substances investigated in CIP2. The best removal performance (78%) was achieved at intermediate values for the ranges of flow and current density explored (5 L/h, 4 mA/cm²), seemingly allowing a synergic contribution of both adsorption and electrochemical oxidation. Although the technology has been proved to perform satisfactorily towards specific micropollutants in both trials, it is not applicable with the same degree of success to the removal of the wide range of chemicals investigated in CIP2. Moreover, due to its relative novelty and hitherto lack of full scale applications, the technology still requires stages of development, especially in terms of hydraulics within the unit (i.e. backwash system) and upstream solids capture.Item Open Access Effectiveness of H₂O₂/UV and O₃/H₂O₂/UV for metaldehyde removal in drinking water and full-scale costing analysis(Cranfield University, 2017-09) Fernandez Lopez-Rey; Hassard, Francis; Jefferson, BruceMetaldehyde is a widely used pesticide in the UK and has been reported to produce drinking water quality failures across the national water utilities. Advanced Oxidation Processes (AOPs) are effective in the removal of recalcitrant organic constituents but pose (i) high energy and chemical costs and (ii) by- products formation upon disinfection stage. In this context, UV/H₂O₂ and O₃/H₂O₂ + H₂O₂/UV were tested at pilot-scale concurrently at Draycote water treatment work (WTW) (UK) for metaldehyde degradation and disinfection by products formation potential (DBPFP) at different energy demands (Eᴅ), H₂O₂ and O₃ doses; and pesticide concentrations. Whole-life costing analysis (WLCA) was undertaken to assess which AOP was most economic for metaldehyde removal at a Draycote sized WTW. Sensitivity analysis considered potential costs of each AOP. Metaldehyde was removed up to 98% (UV/H2O2) and 97% (O₃/H₂O₂ + H₂O₂/UV) successfully fulfilling European Directive 98/83/EC below both 1.0 kWh m⁻³ and 2.14 µg L⁻¹ pesticide inlet water level. Net DBPFP contribution ranged -283 µg L⁻¹ to +255 µg L⁻¹ for trihalomethanes formation potential (THMFP), which are UK regulated. DBPFP was related to organic background characteristics rather than the operating conditions tested in both AOPs. Cost estimating the AOPs for a 0.72-log metaldehyde removal enabled the total expenditures to be determined indicating that energy consumption accounted for 50% (UV/H₂O₂), 49 % (O₃/H₂O₂+ H₂O₂/UV) and 31% (O₃/H₂O₂) of their operating costs. Similar £14.7 million capital costs were appraised for O₃/H₂O₂ and UV/H₂O₂. Overall, O₃/H₂O₂ sub process outperformed the rest of AOPs when considering both metaldehyde degradation (≤96%) and net DBPFP contribution (≤51 µg L⁻¹ THMFP) at the most economically operating costs for 5-month yearly treatment (£0.07 m⁻³). Sensitivity analysis showed the O₃/H₂O₂ more efficient process requiring less inputs than UV/H₂O₂ for the same metaldehyde removal. However, the O₃/H₂O₂ was cost effective at an ideal stoichiometric mass ratio of 0.7 H₂O₂:O₃. Therefore, this would require validation at full-scale. The AOPs were robust for metaldehyde degradation with reasonable costs.Item Open Access The sustainability of reusing oil and gas produced water for agricultural irrigation in drylands(Cranfield University, 2019-06) Echchelh, Alban; Hess, Tim M.; Sakrabani, RubenProduced water (PW) is the largest waste stream generated from oil and gas (O&G) extraction. Half of global PW (~8.5 km3 /year) is injected into deep disposal wells or discharged on the surface. These practices are controversial due to their environmental impacts causing increased regulation and cost. Meanwhile, water- scarce drylands host significant O&G resources. Reusing PW in irrigation provides an alternative to disposal options and could strengthen agriculture and food security in drylands. However, uncertainties exist regarding the sustainability of this practice. This research addresses these knowledge gaps by evaluating the agro-environmental sustainability and the financial cost of reusing PW in irrigation. First, the existing knowledge about PW irrigation is reviewed to identify the agro-environmental risks posed by this practice and the uncertainties regarding its sustainability. Second, irrigation with PW is simulated using a soil- water model to identify the parameters related to the environment and to the irrigation management which determine the sustainability of irrigation. Finally, a framework combining irrigation modelling and a cost analysis is applied in both regional and industrial case studies to identify agro-environmentally sustainable irrigation strategies with PW and estimate their operating costs. This research demonstrates that irrigation with PW can be agro-environmentally sustainable if natural conditions are favourable such as on gypsum-rich draining soils in the least arid climates. Furthermore, adapted management combining irrigation at a little over the crop water needs (100–110% of the crop water needs) and PW blending in a 1:1 up to 1:4 ratio with treated sewage effluent or desalinated PW can achieve agro-environmentally sustainable irrigation by preserving soil fertility, crop yield and groundwater quality. The cost of managing PW in irrigation estimated between $0.19–$1.09/m³ , is higher or within the cost range of surface PW discharge and lower or within the cost range of injecting PW into deep disposal wells. Further research is needed to test and validate the modelling results in field conditions. A case-by-case approach is recommended to assess the broader economic and social impacts of reusing PW in irrigation.Item Open Access Investigation and analysis of two-layer spoke-type ferrite interior permanent magnet machine(Cranfield University, 2019-07) Abdurahem, Hayder Abdulhasan; Luk, Patrick Chi-Kwong; Economou, JohnA Novel two-layer spoke-type ferrite IPM design is presented based on a commercial induction motor as a low-cost high-performance alternative for new installation to meet efficiency requirements “greener” for various variable speed applications. The proposed design improves PM flux by flux-focusing techniques and maximises the reluctance torque with a two-layer structure. High torque density and efficiency are achieved with comparable performance to a rare-earth equivalent. At first, two-Dimensional d-q frame analytical methods are developed based on the magnetic circuit models. Then, FEA models of the ferrite and induction motors are built and analysed. A comprehensive investigation is carried out focusing on the performances in terms of torque profiles, losses, efficiency and power factor. The influences of temperature variation and distribution on the performance of novel two-layer spoke-type interior permanent magnet machines under different operating conditions are analysed. The analysis is based on a developed thermal circuit model. For benchmarking, a standard industrial IM is used. “Comprehensive experimental tests are undertaken, and the results show the proposed ferrite IPM machine has distinctive advantages over the IM in terms of efficiency, power density and speed range. In addition, due to low cost ferrite materials, it has a comparable price advantage. Finally, A prototype machine with the proposed design is manufactured, and both the two motors are tested under various operating conditions. The experimental results confirm the FEA simulations and validate superior performance of the proposed ferrite motor over its induction counterpart.Item Open Access Improved deposition modelling for heat exchangers in pulverised fuel combustors(Cranfield University, 2019-04) Riccio, Chiara; Simms, Nigel J.; Oakley, John E.Co-firing biomass with coal is a promising and cost effective solution to reduce CO₂ emissions derived from the use of fossil fuels in existing power generation systems. However, deposition on heat exchangers (i.e. fouling and slagging) represents a major problem in power plants as it reduces boiler thermal efficiency, causes fireside corrosion and compromises the life of components until forced shutdown. The high complexity and multidisciplinary nature of this problem, which varies with boilers, fuel composition and combustion conditions, has made its prediction a major challange. In this thesis, Computational Fluid Dynamics (i.e. CFD) software, Ansys Fluent® , was used and its features were enhanced with three User Defined Functions (i.e. UDFs) which were modified to predict deposit accumulation, deposit shape and surface temperature. The Eulerian-Lagrangian model was enabled to describe the gas flow field around tubes and the solid ash particle trajectories respectively. Unsteady simulations were run and the combined effect of deposit growth and surface temperature on the deposition flux calculations was included. Experiments of co-firing Daw Mill coal-12 wt.% Miscanthus were carried out in a 100 kWth pilot-scale pulverised fuel (PF) combustor at Cranfield. The flue gas temperature and composition were recorded and fly ash samples were analysed to fit the Rosin Rammler ash particle size distribution model. Moreover, deposits were collected on cooled ceramic probes to measure the deposition flux and the chemical composition. The CFD model was applied to predict deposition on the cooled ceramic probes and the experimental results were used to set boundary conditions and to validate the model. The main challenges met in this work have been highlighted and possible solutions suggested. The model included several deposition mechanisms for ash particles and vapours and took into account the stickiness of the surface and the ash particles. Deposition has been studied for varying probe configurations and surface temperatures and the comparison between the experimental and modelling results was promising. Alkali vapour condensation enhanced the formation of deposit onto clean surfaces at lower temperatures. However, inertial impaction was the main deposition mechanism for bigger ash particles.Item Open Access Structural reliability assessment of complex offshore structures based on non-intrusive stochastic methods(Cranfield University, 2020-11) Shittu, Abdulhakim Adeoye; Mehmanparast, Ali; Kolios, AthanasiosOffshore Wind Turbines (OWTs) are deployed in harsh environments often characterised by stochastic loads and resistance properties. It becomes necessary to propose an accurate and efficient approach for the assessment of uncertainties in material properties and operating environments. Structural Reliability Assessment (SRA) as a form of uncertainty analysis is a useful tool in the design of structures because it can directly quantify how uncertainty about input parameters can affect structural performance. First, this thesis developed a novel non-intrusive SRA method for an OWT jacket structure which maps the response of the structure through a finite number of simulations to develop a response surface and then employ First Order Reliability Methods (FORM) to evaluate the reliability index. This method was validated against a commercial FEA package (DesignXplorer© from ANSYS) which employs direct simulations to predict the probability of failure. The method developed was used in performing stochastic sensitivity analysis of the variables imposed on the OWT support structure. The results from this study, reveals that the uncertainties in the design wind speed is a design driving factor and the hydrodynamic load effects are secondary to this, for the ultimate (ULS), and fatigue limit states (FLS), among others. Second, the SRA of the same structure subjected to pitting corrosion-fatigue was assessed using a damage tolerance modelling approach. The non-intrusive formulation in this study used an Artificial Neural Network (ANN) response surface modelling technique instead of the Multivariate (Quadratic) Polynomial Regression (MPR) method used previously apart from the FEA to represent the crack propagation regimes. The results reveal that for the inherent stochastic conditions, the structure becomes unsafe after the 18th year, before the attainment of the design life of 20 years, among others. The benefit of this approach is that it allows for high fidelity computational tools to be employed for the analysis, hence extending its applicability to various specialist engineering problems through the advanced modelling techniques.Item Open Access Co₂ separations and the role of surface functionality(Cranfield University, 2021) Wadi, Basil; Nabavi, Ali; Manovic, VasilijeTo curb irreversible environmental effects of climate change, urgent measures must be taken to limit anthropogenic emissions and achieve net-zero carbon goals by 2050. Carbon capture technology to meet these goals is wide ranging, with novel methods directed at biogas upgrading or direct air capture. Biogas is produced from the anaerobic digestion of biological waste and considered a valuable renewable energy source; to produce biomethane for use interchangeably with natural gas. However, widespread use of established separation processes is limited, primarily due to low CO₂ selectivity or high energy demands of cyclic operation. One method to tackle these issues is the development of novel sorbents for use in pressure swing adsorption, targeting maximum CO₂ capacity and selectivity, while minimising regeneration energy penalties. Adsorbents incorporated with amines can meet one of these criteria, selectively adsorbing CO₂, but require high regeneration energies. Herein, the adsorption performance of a diverse range of amines grafted on mesoporous silica at varying densities is studied, to understand developing adsorption mechanisms, and identify the ideal degree of functionalisation for gas separations. It was found that although high amine densities led to the highest enhancement in CO₂ capacity and selectivity, moderate levels have comparable selectivity and capacity in isothermal adsorption-desorption conditions, standing out are di- and secondary amines. Diamine loadings achieved an adsorption capacity of 1.12 mmol/g, a heat of adsorption of 35-50 kJ/mol, and an IAST selectivity of 374 at CO₂ partial pressures of 40 kPa. Secondary amines had a low capacity of 0.67 mmol/g, but a higher heat of adsorption comparatively. The optimal binder formulation for pellet preparation of amine grafted silicas was also studied, a necessary step in conducting laboratory scale fixed-bed adsorption studies. When applying amines for ambient air adsorption, very high amine loadings result in slow adsorption kinetics, rendering the advantage of their high capacity debatable. Moderate loadings of primary and triamine under humid conditions have higher adsorption rates >250 µg/g/min, making them more suited for fast cycle processes.Item Embargo Dry batch and semi-continuous digestion: optimising the science behind it(Cranfield University, 2022-04) Rocamora Miguel, Ildefonso; Bajon Fernandez, Yadira; Wagland, Stuart T.Dry anaerobic digestion (AD) is usually linked to inhibitors accumulation, however existing knowledge from wet AD cannot be directly translated to palliate this issue due to the high total solids content (TS) and the reduced mixing limiting diffusion and free water where reactions take place. This thesis investigated the main inhibitory pathways in dry AD and the effect of operational parameters on them. In batch processes the adjustment of the inoculum to substrate ratio (I:S) demonstrated an effect on reducing acidification at the beginning of the process. Furthermore, percolate recirculation showed the best impact to improve contact between microorganisms and substrate and buffer the digester, avoiding pH reduction and producing an 8-fold increase in total methane production compared to water addition at similar conditions. Optimisation of percolate recirculation was also key in maximising production of methane in the full-scale batch dry AD plant studied, with drops of production if recirculation was over the optimum range due to collapse of the biomass pile and inhibitors accumulation. Semi-continuous dry AD of organic fraction of municipal solid waste (OFMSW) resulted in high ammonia accumulation, followed by accumulation of propionic acid producing reactor failure. Different dosing strategies were tested when digesting OFMSW. Dose of trace elements (TE) was done to improve synthesis of enzymes needed in hydrogenotrophic methanogenesis, activated carbon (AC) was added to increase electron transfer between hydrogenotrophic archaea and syntrophic bacteria, while MgCl2 aimed to maintain intracellular osmotic pressure and reduce free ammonia (FA) inhibition. TE dosing increased methane production but did not avoid the accumulation of propionic acid. These results were contrary to available literature in AD at TS lower than 20 %, probably due to the reduced diffusion observed at 40 % TS. Addition of AC and an osmoprotectant like MgCl2 were also unable to reduce propionic accumulation, but methane production improved by 28 % compared to the TE additions. Additionally, short retention times where insufficient for syntrophic acetate oxidation bacteria (SAOB) due to inhibition, producing its wash followed by the reduction of strict hydrogenotrophic archaea. This allowed versatile Methanosarcina to become dominant and change methane production to acetoclastic even at high FA over 1 g/l.Item Embargo An investigation of a novel monolithic nickel-based catalyst for clean hydrogen production(Cranfield University, 2024-05) Shen, Ziqi; Clough, Peter T.; Nabavi, Seyed A.; Wagland, Stuart T.The decarbonisation of the energy sector can anticipate the future of net zero, and hydrogen is currently one of the most promising energy carriers to contribute to this goal. As for hydrogen production, steam methane reforming (SMR) occupies the predominant status and will remain in its position in the short term. The SMR process requires high-performance catalysts such as nickel-based catalysts, and carbon capture technology is of interest to decarbonise the SMR to produce clean hydrogen. The overall aim of the PhD project is to develop a novel monolithic nickel-based catalyst and evaluate its performance under SMR and sorbent-enhanced SMR (SE-SMR) conditions. The literature review looked back on the ceramic materials used in the SMR and SE-SMR processes, and also the method to prepare nickel-based catalysts. Silicon carbide was chosen as the support material due to its excellent thermal and mechanical properties. The monolithic nickel-based catalysts were designed, synthesised, characterised and tested in a fixed-bed reactor, in which the main reactor pipe and the steam generator were designed and constructed for this project. In addition, a pulse injection system was designed and installed on the reactor, and the SMR kinetics were studied using the monolithic catalysts. After the integration of the solid sorbents, a further study was conducted on the effect of structure within the SE-SMR process using the monolithic catalysts. The monolithic catalysts exhibited excellent activity at low SMR temperatures and pressures with a realistic gas space velocity. A kinetic model was established to describe the reaction rates using a novel and time-saving approach. The mass transfer limitations led to a low activation energy in kinetics and a reduction in activity when sorbents were applied. The monolithic catalysts will be a strong candidate for the decarbonisation of the energy sectors, with further improvement of its long-term stability and coordination with appropriate sorbents.Item Embargo Enhancing stationkeeping and motion reduction of floating offshore wind turbines using wave devouring propulsion technology(Cranfield University, 2024-03) Jingru, Xing; Liang, Yang; Liyun, LaoThis PhD thesis investigates the enhancement of stationkeeping and motion reduction in Floating Offshore Wind Turbine (FOWT) platforms through the application of biomimeticinspired Wave Devouring Propulsion (WDP) technology. Through a multidisciplinary approach that encompasses a comprehensive literature review, numerical simulations, and scaled-down water tank experiments, this research confirms the potential of WDP technology to significantly improve the stationkeeping capabilities of FOWT platforms. The thesis is structured around four key objectives, each addressing a critical aspect of WDP application in FOWT platforms—from theoretical underpinnings and simulation tool development for Fluid-Structure Interaction (FSI) analyses, to the investigation of sub-structure dynamics and practical feasibility studies for the integration of innovative sub-structures aimed at stationkeeping. This thesis contributes to the field by providing a comprehensive overview of WDP technology, introducing a novel numerical model for FSI simulations, insights into the hydrodynamic performance of submerged hydrofoils, and the experimental verification of WDP technology’s effectiveness in enhancing platform stationkeeping. Notably, the study proposes optimized design guidelines for foil implementation, demonstrating a significant reduction in mooring tension and thereby advancing the practical applicability of WDP in the marine industry. By advancing the understanding and application of WDP technology, this thesis lays the groundwork for significant improvements in the sustainability and efficiency of maritime operations, aligning with global efforts towards achieving net-zero emissions in the maritime sector.Item Embargo Spatial representation of faecal pollution in unsewered urban catchments(Cranfield University, 2023-12) Sultana, Mst Sufia; Tyrrel, Sean; Waine, TobyIn many secondary cities in Bangladesh and other economically developing regions in Asia, Africa and Latin America, urban sanitation is dependent on individually constructed and maintained decentralised sanitation technologies, e.g., septic tanks operating in the absence of a city-wide support system. In such urban areas, wastewater is transported through a network of storm drains which were not designed for this purpose. The release of wastewater runs the risk of imperfect containment and high risk of exposure to faecal pathogens. Effective methods to identify the sources and movement pathways of faecal matter within cities are currently lacking. Here, a Sanitation Infrastructure and Faecal Flow (SanIFFlow) approach is introduced, representing a novel methodology that utilises open-source data to map the sanitation infrastructure and the faecal matter sources and movement pathways. This approach is first demonstrated through a prototype sub-catchment model within Rajshahi city, Northwest Bangladesh. The sub-catchment model identifies and characterises the sources, pathways, and movement of faecal matter. To refine and validate the method, an uncertainty analysis was conducted, supplemented by a field study, to assess the reliability of the approach. Sensitivity analysis identified five key factors influencing the spatial pattern of faecal flow: septic tank emptying, soak pit use, sludge removal from drains, variations in faecal matter production, and the absence of toilets in some buildings. While each factor might have a negligible impact individually, in combination the factors showed almost 50% faecal matter cannot reach the outlet point. Further insights from the uncertainty analysis and fieldwork suggest that, although the sub-catchment model has potential for individual building level sanitation management, the existing ward-level management system, being the smallest administrative unit in the case study city, calls for a model at that spatial scale as a more practical approach. Building upon this, the SanIFFlow approach has been deployed to develop a city-scale model built from ward-level subunits, tailored for practical application in unsewered cities like Rajshahi. This approach holds promise for global applicability, given the widespread availability of open-source data.Item Embargo Improvements of electrochemical water splitting efficiency by using economically viable Co/CoPs/TiO₂/NiF electrocatalysts(Cranfield University, 2024-08) Kulathunga Mudiyansele, Soorya Dananjaya Bandara Kulathunga; Wijayantha, Upul; Jiang, YingThe drive for sustainable energy solutions has led to the search for efficient and cost-effective electrocatalysts for green hydrogen production via electrochemical water splitting (EWS). This study addresses the limitations of precious metal- based catalysts by investigating alternative, earth-abundant materials. This research introduces a novel Co/CoPs(240)/TiO₂/NiF electrocatalyst, synthesized using deep eutectic solvent (DES)-mediated electrodeposition of Co and cobalt phosphides (CoPs) on TiO₂-coated nickel foam (NiF) substrate. Electrophoretic deposition of TiO₂ nanoparticles was successfully applied to NiF, resulting in a smooth and even surface. On this TiO₂-coated substrate, subsequent Co/CoPs deposition produced unique hexagonal and cauliflower-like structures with a uniform distribution of Co and P. Energy dispersive X-ray spectroscopy (EDX), scanning electron microscopy (SEM), and X-ray diffraction (XRD) were used to confirm these features. Optimizing the Co/CoPs deposition times significantly reduced the hydrogen evolution reaction (HER) overpotential to 34.42 ± 4.2 mV at 10 mA cm⁻² in 1 M KOH. Remarkably, the Co/CoPs(240)/TiO2/NiF catalyst required only 27.43 mV with a Tafel slope of 48.35 mV dec⁻¹. Stability tests demonstrated minimal performance degradation after 5000 cycles and 40 hours of operation, demonstrating excellent durability. This optimized catalyst outperformed Co/CoPs(240)/NiF, commercial 10% Pt/C electrodes, and other reported catalysts. The oxygen evolution reaction (OER) performance also highlighted the catalyst's efficiency, with an overpotential of 331.70 mV at 10 mA cm⁻² in 1 M KOH and a Tafel slope of 73.96 mV dec⁻¹. Stability tests revealed minimal performance degradation after 1000 cycles. Furthermore, a full water electrolyser system using Co/CoP(240)/TiO2/NiF electrodes achieved a total voltage of 1.612 V at 10 mA cm⁻², indicating the practical viability of the optimized electrodes for water splitting applications. The remarkable performance of the Co/CoPs(240)/TiO₂/NiF electrode is primarily due to the presence of the TiO₂ layer, which enhances the surface area and acts as a catalyst promoter through synergistic effects and enhanced charge transfer kinetics. This research suggests that incorporating an intermediate TiO₂ layer can promote the catalytic activity of other catalysts as well. In conclusion, this study presents an effective and economical alternative to noble metal-based electrocatalysts for water splitting. By integrating TiO₂ with Co/CoPs on a NiF substrate, the research advances the development of high-performance, low-cost catalysts and contributes to the sustainable production of green hydrogen.Item Embargo Biocontrol of ochratoxigenic fungi by endogenous lactic acid bacteria and yeasts from ivorian robusta coffee in the context of climate change(Cranfield University, 2023-09) Lopez Rodriguez, Claudia; Medina-Vaya, Angel; Schorr-Galindo, Sabine; Verheecke-Vaessen, Carol; Fontana, Angelique; Strub, CarolineThis doctoral research delves into the innovative domain of biocontrol strategies targeting mycotoxigenic fungi in the context of climate change. Focusing on Ivorian coffee, a vital economic and agricultural commodity, the study explores the potential of indigenous lactic acid bacteria (LAB) and yeasts as biocontrol agents. Mycotoxins, toxic secondary metabolites produced by fungi, pose significant health risks and economic losses. As climate change amplifies the proliferation of mycotoxigenic fungi, the demand for sustainable and eco-friendly interventions intensifies. The research encompasses comprehensive isolation, identification, and characterization of LAB and yeasts from Ivorian coffee, evaluating their antagonistic properties against mycotoxigenic fungi. Furthermore, the study elucidates the mechanisms underlying the biocontrol activity, shedding light on how these microorganisms mitigate mycotoxin contamination. This research is pivotal in the pursuit of climate-resilient strategies for mycotoxin management, contributing to both food safety and agricultural sustainability.Item Open Access Influencing factors and mechanisms of local government green development behaviour: evidence from China(Cranfield University, 2024-01) Zhu, Xiaowen; Unal, Enes; Longhurst, PhilipGreen development has become an important strategy for local governments to achieve greater sustainability, and adopting green development behaviours has significant implications for local governments in addressing the relationship between the environment and the economy. Previous research demonstrated that the unique characteristics of green development practices have received considerable attention from scholars. Most studies have highlighted green development practices in the private sector, although the adoption of green development practices in the public sector remains understudied. Current research on green development behaviour in the public sector primarily reflects, at the individual level, the green behaviour of employees and, at the organisational level, the green purchasing behaviour of a particular government department. The discussion of local government green development behaviour is not predominant. Therefore, this thesis proposes that a detailed understanding of the processes and specific practices of local government green development behaviours may be essential for local governments to improve the effectiveness of implementing sustainable practices. Although existing studies have addressed the influencing factors that lead to the adoption of sustainable development by local governments, there needs to be a more systematic theoretical analysis of the underlying mechanisms adopted by local governments to achieve green development behaviours. Accordingly, this thesis aims to explore the factors that influence the implementation of green development behaviours by local governments and the mechanisms of influence between the factors. This study draws on mixed methods to develop two studies. The first is a qualitative study that explores local government green development behaviour and its influencing factors. It applies various data collection methods, including semi-structured interviews and document analysis. Fifty-three officials from local government departments related to green development in China’s Jiangsu province were interviewed, and the data were analysed using a grounded theory method. The second is a quantitative study. Seven hundred twenty-two valid questionnaires were collected, and the model proposed in the first study with Structural Equation Modelling (SEM). The findings illustrate how the interactions between various factors shape the green development behaviour of local governments. The main findings show that: (1) local government green development behaviour is a kind of behavioural change, which can be divided into local government green development policy formulation and implementation. (2) The three main influences on local governments’ green development behaviours include internal driving factors, external environmental pressures, and the basis of regional green development. (3) Internal driving factors and external environmental pressure can influence local governments’ green development behaviours. (4) Internal driving factors mediate the relationship between external environmental pressure and green development behaviour. The basis of regional green development has a moderating effect on the relationship between internal driving factors and green development behaviours, as well as the relationship between external environmental pressures and green development behaviours. This thesis provides a framework that supports local government behaviour's decision-making process on the managerial implications. Paper I analyses the specific processes and practices of local government green development behaviour, Paper II constructs a theoretical model of local government green development behaviour, and Paper III examines the mechanisms by which various factors influence local green development behaviour. At a broader level, this thesis enriches and expands the research content of sustainable practices in the public sector. It also provides novel insights for local governments to formulate effective green development policies, which will help them develop green development directions and implement green development behaviours to promote more remarkable sustainable development in the region.Item Open Access Advancing biosensing techniques for detection of antimicrobial resistance genes and antibiotics in water(Cranfield University, 2024-09) Li, Wenliang; Yang, Zhugen; Coulon, FredericAntimicrobial resistance (AMR) poses a significant global public health threat requiring urgent attention for surveillance of antibiotic resistance genes (ARGs) and antibiotics in the environment. In this PhD study, a real-time fluorescent detection assay of antimicrobial resistance genes (ARGs) was developed to specifically target two key ARGs, tet(M) and tet(x3) to detect tetracycline and tigecycline resistance respectively in water samples. Additionally, crassphage gene was investigated for anthropogenic activities since they also play a vital role in the AMR transmission. The advanced ARG detection assay was based on multiplexing recombinase polymerase amplification (RPA) and subsequent sequence-specific recognition by the trans-cleavage activity of Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)/Cas12a. The assay achieved limits of detection (LODs) of 1 copy µL⁻¹ for all three gene targets with an accuracy of 100% in spiked tap and surface water samples. Expanding the assay by including two additional end-point detection modalities, lateral flow assay (LFA) and voltametric detection, further demonstrate its versatility. LODs of 1 copy µL⁻¹ for tet(x3) and crassphage, and 10 copies µL⁻¹ for tet(M) (LFA) and 10 copies µL⁻¹ for all three targets (electrochemical) were reached. Validation against gold standard quantitative polymerase chain reaction (qPCR) using real water samples, including wastewater and drinking water samples, revealed a remarkable 100% accuracy rate. Antibiotics detection assay was conceptualised based on the amplification of hybridisation chain reaction (HCR) followed by CRISPR/Cas mediated cleavage within a DNA hydrogel matrix. This approach aimed to release electroactive methylene blue (MB) particles, detectable and quantifiable by square wave voltammetry (SWV). While unforeseen circumstances impeded full assay development, the preliminary data illustrated the viability of the proposed method, suggesting avenues for further research to develop rapid and onsite antibiotics detection methods.Item Open Access The epidemiology and management of cladosporium on raspberry(Cranfield University, 2024-01) Farwell, Lauren; Xu, Xiangming; Medina-Vaya, AngelCladosporium is a genus of fungi that causes dark mycelial lesions on raspberries, rendering fruit unmarketable. As Cladosporium is an opportunistic pathogen, its prevalence varies across years, and there is insufficient research on its epidemiology and management. This study aimed to investigate the epidemiology of Cladosporium on raspberries and to elucidate which management strategies could be effective. Isolates of Cladosporium were obtained from raspberries, with C. cladosporioides being the most predominant, and was therefore used in further experiments. The susceptibility of raspberry fruit development was determined, with ripening and ripe fruit found to be susceptible to skin lesions; this stage of development was subsequently targeted in management studies. The effects of ripening and fruit location (fruit location within a tunnel vs. across a farm) on the inoculum load on the surface of raspberries were investigated using metabarcoding studies. The fungal and bacterial microbiomes were also investigated to better elucidate the ecology of Cladosporium on the fruit surface. Cladosporium was more abundant on green fruit than ripening fruit; perhaps due to organisms such as Rouxiella present on the fruit’s surface. Fungal α diversity increased during ripening while bacterial diversity decreased. The Cladosporium inoculum load in the air was also investigated, with more spores trapped inside a raspberry polytunnel than an open field. The efficacy of commercial Biological Control Agents (BCAs) and resistant varieties to control Cladosporium skin lesions were tested across two years in field applications. The Trichoderma sp. was the most effective at reducing the incidence of Cladosporium on raspberry than compared to the other tested products. The variety resistance study was inconclusive, but results indicate further testing will reveal which varieties are more susceptible. This research will inform potential management strategies against Cladosporium on raspberries that will aid growers in reducing food waste sustainably