Saudi Cultural Missions Theses & Dissertations
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Item Restricted Evaluating the Feasibility of Clean Electricity: Low-Carbon Electricity and Solar Panels(Imperial College London, 2024) Aldabal, Hadia; Wilkins, MicahelThe viability of solar energy was addressed by analysing the technological, financial, and political feasibility of solar energy. This was done to address a literature gap in clean energy through the inclusion of the landscape of fossil fuels with carbon sequestration for emission reduction. The selected mode of analysis included a comprehensive literature review that draws out the key differences between solar energy, and fossil fuels with carbon reduction technologies. The study then drew on secondary data that illustrated a comparative analysis of the cost of solar energy, and emissions to that of traditional energy sources, as well as generation capacity of solar. The technological, financial, and political/policy factors that contribute to the findings were then discussed regarding three key metrics: feasibility, barriers, and recommendations. The findings of this study suggest that the growth in solar generation, and the decline in costs are linked directly to technological advancements, appropriate low-carbon instruments, and favourable policies. This has been demonstrated through the illustration of the declining cost of solar energy in the face of traditional energy counterparts, demonstrating significant potential for widespread implementation of clean electricity. The findings proposed in this study demonstrated the possibility of solar energy as a highly plausible method for deployment and adoption at a large scale, with the potential to compete further with fossil fuels upon additional advancement of the assessed metrics.3 0Item Restricted Micro fluidised bed technology for the screening of carbon capture adsorbents (Chemical Engineering)(Saudi Digital Library, 2023-12-18) Alamri, Awad; Zivkovic, VladimirTo accomplish global Net Zero emissions goals, a diverse portfolio of technologies, regulations, frameworks, and changes in behaviour will be required. Within this landscape, carbon capture is still relevant in reducing or entirely offsetting greenhouse gas emissions, particularly emissions that cannot be avoided in the immediate or long-term. Adsorption-based processes using solid sorbents are appealing due to their high flexibility, non-volatility and low energy regeneration burden. Ultimately, the success of adsorption-based processes depends on the development of the materials (rapid kinetics, high capacities, high stabilities, high selectivities, etc.) and gas-solid contacting technology (good mixing, low-pressure drop, etc.). This thesis proposes that 3D-printed Micro Fluidised Bed Reactor (MFBR) technology can meet these requirements due to cost-effectiveness, high-throughput capability, minimal energy requirement, efficient heat/mass transfer characteristics, and enhanced safety measures. In the early phases of material development, only small volumes of samples are typically synthesised; it would be inefficient to mass-produce potentially poor-performing materials before their complete characterisation. Thus, the MFBR's primary function is to facilitate data collection of new materials under relevant operating conditions, thereby enabling informed decision-making. Accordingly, this thesis aims to develop the MFBR as a platform for low-cost and rapid screening of novel CO2 adsorbents. To demonstrate this approach, 3D-printed micro fluidised beds are used to screen the performance of a commercially available hydrotalcite product (PURAL MG70, Sasol). In its raw as-supplied state, this powdered hydrotalcite has significant cohesive characteristics that prevent fluidisation. Accordingly, detailed hydrodynamic experiments were first performed in order to find feasible MFBR designs and operating conditions for these Geldart C powders by studying the pressure drop characteristics. The hydrodynamic studies demonstrate that the fluidisation quality was significantly enhanced by employing a straightforward removal of fines through pre-sieving, specifically retaining particles larger than 53 μm (density of 2 g/cm3 ), followed by pre-fluidisation. This improved quality included removing a significant hysteresis between increasing and decreasing the gas velocity, minimising the amplitude of the pressure drop overshoot prior to fluidisation, and ensuring that the whole bed was fluidised without gas bypassing (slugging). Furthermore, addition of a secondary inert Geldart A type particle (silica, with a mean particle size of 93 ± 10 μm and density of 2.65 g/cm3 ) to the hydrotalcite powder resulted in similar improved fluidisation quality. These treatments were valid in three different 3D-printed MFBRs (bed diameters of 𝐷t = 10–15 mm) at all bed heights tested (𝐻௦/𝐷௧ = 1–3). Following this, the adsorption process was studied using CO2 breakthrough experiments, validated against independent TGA measurements. These breakthrough tests were conducted for a 10 mm bed diameter at various bed heights (𝐻௦/𝐷௧ = 2–3), CO2 concentration (8–16 vol%), superficial gas velocities (1.5–6 𝑈mf) and operating temperatures (25–60 °C). The results indicate that the measured CO2 adsorption capacity increases as the gas velocity increases in the bubbling regime before decreasing again in the slugging regime. A maximum capacity of 0.76 mmol/g was measured when operating at 4𝑈mf, 16 vol%, and 40 °C. The capacity declined at lower velocities (4 𝑈mf) because of gas bypassing due to slugging. The maximum capacities observed agreed with independent TGA measurements at all conditions. This agreement defined the operating window for studying the adsorption kinetics (corresponding to operating under kinetically limited conditions). At 16 vol% CO2 concentration, the desirable kinetically limited velocity range was 3 – 4 𝑈mf. At a lower CO2 concentration of 8 vol%, the process was mainly diffusion-limited, which reduced the width of the operating window; only 4𝑈mf achieved the kinetically limited state. This highlights the importance of including hydrodynamic screening in the workflow of materials development using the MFBR platform. Finally, the desorption kinetics were studied through the implementation of temperature swing adsorption, where adsorption was performed at 40 °C (which gave the highest capacities) and desorption was performed between 40 °C and 90 °C. At desorption temperatures of 40 °C, expectedly, a low 7% CO2 recovery was observed. At 90 °C, the CO2 recovery increased to 33% of the adsorbed CO2. Raising the desorption temperature changes the thermodynamic equilibrium, destabilising the affinity of the CO2 to the hydrotalcite by overcoming the activation energy of weak Van der Waals forces or chemical interactions with the surface. The maximum ‘desorbed capacity’ was measured to be 0.24 mmol/g at 90 °C. Based on the results obtained in this thesis, it can be concluded that 3D-printed micro fluidised beds can be used for the development of carbon capture sorbents, offering insights for decision-making and design.13 0