http://theses.ncl.ac.uk/jspui/handle/10443/4094 2026-02-04T19:49:41Z http://theses.ncl.ac.uk/jspui/handle/10443/6663 Title: Mini-TORBED Technology for Carbon Capture Adsorbent Screening Authors: Jamei, Rouzbeh Abstract: Carbon capture (CC) via fluidized bed reactors presents a promising avenue for mitigating CO2 emissions across the energy, industrial, and transportation sectors. This research focuses on developing and evaluating a small-scale and efficient CO2 capture screening platform employing a 3D-printed toroidal fluidized bed (TORBED) reactor. A commercial sorbent, based on branched polyethyleneimine (BPEI), was screened for capturing CO2 from artificial flue gas streams under a range of conditions. The adsorption screening experiments involved the introduction of various N2/ CO2 ratios into the TORBED reactor, and breakthrough curves were collected under different operating conditions, including CO2 volume fractions, BPEI bed loads, gas flow rates, and temperatures. In the hydrodynamic study, three potential industrial materials (RTI, Sasol, and Casale materials) were screened for compatibility with the TORBED reactor. The 'desirable flow regime' was quantified through methods such as visual observations, pressure drop analysis, and standard deviation analysis of pressure drop measurements, which provided insights into particle formations, flow stability, and uniform fluidization. Key results indicated that the RTI material exhibited optimal flow regimes with minimal pressure drop and high stability, making it the most suitable candidate for further adsorption and desorption studies. This comprehensive approach ensured the selection of an effective sorbent and optimal operating conditions for the TORBED reactor, contributing to advancements in carbon capture technology. In adsorption screening experiments, artificial flue gas streams comprising various N2/CO2 ratios were introduced into the TORBED reactor. Breakthrough curves were collected under different operating conditions, including CO2 volume fractions (ranging from 2 to 20 vol%), BPEI bed loads (1–2.5 g), gas flow rates (20–35 L/min), and temperatures (40–70 °C). The breakthrough curves provided insights into the sorption behaviour of BPEI under different conditions, facilitating the characterization of its adsorption capacity and kinetics. A maximum sorbent capacity of 2.64 ± 0.06 mmol/g was measured within experiment durations lasting no longer than 10 seconds. This rapid data collection rate highlights the potential for high throughput screening. Moreover, precise temperature control within the TORBED effectively minimized the influence of heat of adsorption on kinetics. Desorption, a critical aspect of CC, was then studied given its importance in the overall process and lack of relative attention compared to adsorption in the wider literature. The desorption characteristics of the commercial BPEI adsorbent were also investigated using breakthrough experiments, with a focus on studying the influence of heat transfer effects. Experimental results revealed that higher desorption temperature (110 °C), shorter preheating time (achieved with a gas flow rate of 25 L/min), and elevated CO2 concentrations during adsorption (20 vol%) improved the desorption efficiency significantly (defined as CO2 desorbed compared to the adsorbed amount). Kinetic modelling plays a crucial role in understanding and optimizing adsorption and desorption processes. Upon analysis of the cumulative uptake curves extracted from the breakthrough data, it was found that the fractional order kinetic model best matches the behaviour of the BPEI adsorbent compared to the pseudo-1st order and pseudo-2nd order models. This implies that both physisorption and chemisorption processes are responsible for the binding of the CO2 with the BPEI surface. This work reinforced by two published papers in the Chemical Engineering Journal—provides fundamental insights and practical solutions that directly contribute to more efficient, flexible, and economically viable CCS processes. 1. Jamei et al. (2023, Chem. Eng. J. 451:138405) demonstrated rapid and intensified screening of a branched polyethyleneimine (BPEI) adsorbent, achieving breakthrough measurements in a matter of seconds. This unprecedented speed of data collection allows for the rapid assessment of multiple sorbents and conditions, ultimately reducing the time and resources required for sorbent selection and optimization. 2. Jamei et al. (2024, Chem. Eng. J., 1385894724070591) addressed challenges related to small-scale Temperature Swing Adsorption (TSA) in CCS. The study showed that by tuning temperature profiles and flow regimes within the TORBED reactor, it is possible to enhance sorbent regeneration efficiency. In summary, this research highlights the potential use of small-scale TORBED technology for screening CC materials to advance carbon capture more generally. By investigating adsorption and desorption characteristics and employing kinetic modelling, this study offers valuable insights for example optimising desirable flow regime to uniform fluidisation of sorbents in entire bed area for enhancing the efficiency of CO2 capture and mitigating industrial emissions. Keywords: TORBED, Adsorption, swirling, carbon capture, Fluidisation, BPEI Description: PhD Thesis 2025-01-01T00:00:00Z http://theses.ncl.ac.uk/jspui/handle/10443/6644 Title: Research on the topology of switched capacitor multilevel inverter Authors: Shan, Ze Abstract: With the gradual depletion of fossil energy and the deterioration of the global climate caused by greenhouse gas emissions, renewable energy power generation has become a hot research topic today. Multi-level inverter is an important equipment in renewable energy power generation system. The switched capacitor inverter, which evolved on the basis of the multi-level inverter, has attracted widespread attention in recent years due to its advantages of self-boosting, self-balancing of capacitor voltage, and suitability for medium and high power. This thesis conducts a comprehensive analysis and research on various multilevel inverters, and then proposes a 13-level switched capacitor inverter topology and a 17- level switched capacitor inverter topology. For the 13-level switched capacitor inverter, there are one DC source input and 3 times voltage gain of the output voltage. The number of the switch is 13 and the number of the diode is 2. The utilization of the t- type structure makes the output voltage step reduced to 1/2Vdc and the utilization of the crossing structure gives the topology the capability of inherent output voltage polarity shift. Redesigned series/parallel switched capacitor unit makes the inverter has the capability of flexible extension to output variable number of output voltage level and output voltage gain. Compared with diode-clamped multilevel inverter, when output the 13-voltage levels, the number of the switches utilize in the circuit is 24 and the number of diodes is 66. So the 13-level switched capacitor inverter proposed in this thesis, the number of the switch is approximately 1.85 times lower than that of the diode clamped multilevel inverter. The number of the diode is 33 times fewer than that of the diode clamped multilevel inverter. The flying capacitor inverter requires relatively more components for the same number of output voltage levels. Compared to the proposed 13-level switched capacitor inverter in this thesis, the flying capacitor inverter has 1.85 times the number of switches and 3 times the number of capacitors. Additionally, the flying capacitor multilevel inverter suffers from capacitor voltage imbalance, whereas the inverter proposed in this thesis has the capability of self- balancing capacitor voltages. The 17-level switched capacitor inverter proposed in this thesis is an optimization of the 13-level switched capacitor inverter. By repositioning the DC power sources and adding two necessary switches and one essential diode, the design achieves a higher number of output voltage levels and a 4 times output voltage gain. Based on the switched capacitor inverters with the same number of output levels designed by other scholars in recent years, the typical number of switches used is 20-24, the number of capacitors used is 5-8, and the achieved voltage gain is 2-3 times. Therefore, the 17- level switched capacitor inverter proposed in this thesis reduces the number of switches by 25%, the number of capacitors by 33.3%, and improves the voltage gain by 33.3%. Both of these two proposed topologies are controlled by the phase disposition pulse width modulation (PDPWM) strategy and MATLAB/Simulink is utilized to conduct simulation studies on the two proposed topologies, with a detailed comparative analysis. The results indicate that the device cost of the proposed 17-level switched capacitor inverter is reduced by 34% compared to that of the 13-level switched capacitor inverter, implying a lower component count for the 17-level inverter. Additionally, the Peak Voltage Stress of the 17-level switched capacitor inverter is reduced by 25% compared to the 13-level inverter. In subsequent hardware experiments, the control logic for the 17-level switched capacitor inverter is implemented using FPGA, and detailed experiments are carried out to evaluate its output performance under various load conditions. The results demonstrate the good performance of the proposed 17-level switched capacitor inverter. Description: Ph. D. Thesis. 2025-01-01T00:00:00Z http://theses.ncl.ac.uk/jspui/handle/10443/6643 Title: Novel DNA-templated nanotechnology devices Authors: Stokoe, David James Abstract: This thesis describes the preparation and characterisation of DNA-templated nanowires followed by their incorporation into field effect transistors. DNA has been used as a template in order to grow nanowires consisting of vanadium dioxide (VO2), cadmium sulphide (CdS) and a cadmium sulphide - carbon nanotube mix- ture (CNT-CdS) via a precipitation reaction. The growth of these nanowires is a two stage process in which the materials first coordinate with DNA before nucleating and then grow- ing to form long and smooth wire like structures. The novel VO2 nanowires formed have been characterised using a mixture of Fourier Transform Infrared Spectroscopy (FTIR), UV-Visible Spectroscopy (UV-Vis), Powder X-ray Diffraction (pXRD) and X-ray Photoelectron Spectroscopy (XPS) in which it was found that the vanadium interacted with the DNA and formed a product with a structure simi- lar to VO2 nanorods. Further investigations were carried out by using Atomic Force and Scanned Conductance Microscopy (AFM and SCM respectively) which showed long wire- like structures with heights upwards of 8 nm that showed weakly conducting nature when probed with SCM. AFM studies also showed that without DNA being present, no wire like structures were formed. Basic current-voltage (IV) curves were recorded over a range of temperatures using platinum interdigitated electrodes (IDEs) which confirmed the weakly conducting nature of the nanowires and that they showed Arrhenius behaviour. The con- ductance of the prepared nanowires was noticeably higher than any other DNA-templated nanowires prepared in past studies. Finally the samples were incorporated into field effect transistors (FET) and the source-drain current was measured as the gate voltage was al- tered. The FETs showed basic transistor functionality in which at larger gate voltages the current between the source and drain also increased. The effect of temperature was also examined for the VO2-DNA nanowires where it was discovered that heating the samples to 150 ◦C caused an irreversible rise in conductance. 2 The CdS nanowires have been characterised in the past however and AFM was used to confirm the formation of nanowires, which showed a diameter of around 6 - 8 nm. IV curves were again recorded over a range of temperatures using IDEs and the samples showed thermally-activated conductivity. The CdS-DNA nanowires were then incorporated into FETs but showed no reliable transistor like behaviour. This is thought to be due to the low conductance of the material as well as the high contact resistance. The final material investigated was CdS-CNT-DNA in which the DNA was wrapped around multi-walled carbon nanotubes (MWCNTs) before CdS was added. FTIR of this ma- terial showed distinct differences in wavenumbers for bare DNA and the templated DNA, showing signs that an interaction is occurring. This was confirmed by using AFM in which wire like structures with heights of 4 nm. In the absence of DNA no wire like structures form, only small particles with heights of 8 - 12 nm. IV curves showed good conductance and by measuring over a temperature range, the materials semiconducting properties were confirmed. The samples were then incorporated into FETs and they showed basic transistor behaviour with a low transconductance. Description: Ph. D. Thesis 2025-01-01T00:00:00Z http://theses.ncl.ac.uk/jspui/handle/10443/6610 Title: Structural optimisation of ship hull using finite element method Authors: Abedin, Joynal Abstract: The design of ship structures is a multilayered process governed by numerous regulations and standards, demanding meticulous consideration of structural responses and production costs. This research presents a multi-objective structural optimisation methodology tailored for a multipurpose cargo ship. It addresses compliance with classification society regulations, cost effectiveness, assessment of structural responses under diverse loads and conducts a comprehensive buckling analysis. The initial phase involves transforming a 2D CAD design into a 2D model, facilitated by BV Mars 2000 software, followed by a comprehensive evaluation of the ship's scantling compliance with Bureau Veritas rules. Subsequently, the meticulous construction of a 3D cargo hold model featuring three cargo compartments sets the stage for a comprehensive analysis employing Femap-integrated NX Nastran finite element software. This analysis scrutinises the structural response of the ship's hull under the combined influence of bending and torsional loads, including a detailed buckling analysis. The study explores the ramifications of torsion for both open-deck and closed-deck ship configurations. Furthermore, the research rigorously validates the precision of the 3D finite element model by means of exhaustive assessments involving beam theory and direct calculations. A notable finding connected with this study is the prominence of hull girder normal stresses at midship, arising from still water and vertical wave bending moments, contributing to nearly 70% of the total stress when the ship is inclined. Horizontal wave bending moments account for approximately 10% of the stresses, whereas warping stresses contribute roughly 20% in open-deck ship designs. Additionally, the research demonstrates that torsion has minimal impact on closed-deck ship configurations. The investigation extends to the analysis of hull girder deflection, systematically examined using numerical techniques and Euler-Bernoulli beam theory, focusing on the significance of longitudinal deflection over transverse deflection. A novel approach is presented using Minitab software's Fractional Factorial Design technique as part of the Design of Experiments (DOE) framework. The strategy aims to identify the critical parameters affecting hull girder Von Mises stress, torsional stress, as well as production costs. iv Ship design optimisation is then carried out by incorporating regression equations for Von Mises stress and production costs from Minitab software into the Non-dominated Sorting Genetic Algorithm II (NSGA-II), managed using Python software. The optimally designed midship section underwent rigorous validation to ensure conformity with industry standards and classification society regulations. Essential modifications to inner bottom plates and double bottom side girders are made to meet these stringent requirements. This optimisation process results in a substantial 10% reduction in ship weight and production costs compared to the initial design. It achieves a peak design stress of 296.2 MPa below the limit through prudent adjustments in plate thickness, web frame positioning and stiffener arrangement. This research delivers a comprehensive framework for the structural optimisation of ship hulls, potentially enhancing safety, sustainability and competitiveness within the maritime engineering industry. Description: PhD Thesis 2025-01-01T00:00:00Z