This work concerns the functionalisation of a variety of carbon materials for the selective adsorption of carbon dioxide. A key challenge in post-combustion capture from gas fired power plants is related to the low CO2 concentration in the flue gas (4- 8%). Therefore highly selective adsorbents have the potential to improve the efficiency of the separation of carbon dioxide from gas mixtures. The study was performed in conjunction with the EPSRC funded project ‘Adsorption Materials and Processes for Carbon Capture from Gas-Fired Power Plants – AMPGas’. The carbon materials investigated included multi-walled carbon nanotubes, a microporous activated carbon, two types of mesoporous activated carbon and multi-walled carbon nanotube/polyvinyl alcohol composite aerogels. The uptake of carbon dioxide by these materials was enhanced through the addition of basic amine groups to the materials. The adsorption properties of the samples were tested by the zero-length column technique, thermal gravimetric analysis and breakthrough experiments. The materials were generally tested at conditions representative of those found in the flue gas of a fossil fuel power plant: 0.1 bar partial pressure of CO2. Two approaches were adopted for the chemical functionalization of the solid carbon supports. First, amine groups were covalently grafted directly to the surface and secondly amine molecules were physically adsorbed within the porous structure of the material by wet impregnation. It was seen that wet impregnation enabled the incorporation of a greater number of amine groups and the CO2 capacity of the materials was investigated with respect to the carbon support structure, the type of amine and the amount of amine loading. Larger pore volume mesoporous carbon materials were seen to provide a more efficient support for the amine to interact with the CO2. A greater than 12-fold increase in the CO2 capacity was observed when the amine impregnated carbon material was compared to the raw starting material. The extended zero-length column was introduced and fully characterized as a novel breakthrough experiment. It requires a small sample mass (~50 mg) and it allows binary selectivities to be calculated. It was shown, through multiple experiments and simulations that the breakthrough experiments were conducted under close to isothermal conditions which greatly simplifies the analysis of the breakthrough curves. In addition, a new zero-length column model was proposed to account for the reaction between the amine and the CO2 in the adsorbed phase and fitted to experimental data. An interesting double curvature was observed in the concentration profile during the desorption step which was attributed to the kinetics of the amine-CO2 reaction. A brief investigation was carried out into the binary separation of biogas (45% CO2: 55% CH4) by zeolite 13X, activated carbon and an amine impregnated activated carbon. Finally, initial investigations into the properties of low density carbon nanotube aerogels which have a large accessible pore volume, were carried out. Their potential as highly efficient supports for amine impregnation was investigated. It was found that amine functionalized carbons strongly interact with carbon dioxide and have the potential to be integrated as an adsorbent in a rapid temperature swing process that separates carbon dioxide from dilute gas streams.

This thesis seeks to improve the economic viability of carbon capture process by reducing the energy requirement of amine scrubbing technology. High steam requirement for solvent regeneration in this technology can be reduced by improvements in the regeneration process. Solvent models based on experimental results have been created by previous researchers and are available for simulation and process modeling in Aspen Plus®. Standard process modeling specifications are developed and multiple regeneration processes are compared for piperazine (a cyclic diamine) in Chapter 2. The configurations were optimized to identify optimal operating conditions for energy performance. These processes utilize methods of better heat recovery and effective separation and show 2 to 8% improvement in energy requirement as compared to conventional absorber-stripper configuration. The best configuration is the interheated stripper which requires equivalent work of 29.9 kJ/mol CO₂ compared to 32.6 kJ/mol CO₂ for the simple stripper. The Fawkes and Independence solvent models were used for modeling and simulation. A new regeneration configuration called the advanced flash stripper (patent pending) was developed and simulated using the Independence model. Multiple complex levels of the process were simulated and results show more than 10% improvement in energy performance. Multiple cases of operating conditions and process specifications were simulated and the best case requires equivalent work of 29 kJ/mol CO₂. This work also includes modeling and simulation of pilot plant campaigns carried out for demonstration of a piperazine with a 2-stage flash on at 1 tpd CO₂. Reconciliation of data was done in Aspen Plus for solvent model validation. The solvent model predicted results consistent with the measured values. A systematic error of approximately +5% was found in the rich CO₂, that can be attributed to laboratory measurement errors, instrument measurement errors, and standard deviation in solvent model data. Stripper Modeling for CO₂ capture from natural gas combustion was done under a project by TOTAL through the Process Science and Technology Center. Two configurations were simulated for each of three flue gas conditions (corresponding to 3%, 6% and 9% CO₂). Best cases for the three conditions of flue gas require 34.9, 33.1 and 31.6 kJ/mol CO₂. / text

Life cycle analysis is carried out for 11 predicted configurations of pyrolysis biochar systems to determine greenhouse gas balance, using an original spreadsheet model. System parameters reflect deployment in Scotland, and results demonstrate that all major crop and forestry feedstocks offer greater GHG abatement than other bioenergy technologies, regardless of system configuration. Sensitivity analysis determines the relative importance of uncertain variables in the model and optimistic to pessimistic scenarios are used for system operation. Slow pyrolysis is compared to fast pyrolysis and biomass co-firing for GHG abatement and electricity production, using various scenarios for availability of indigenous Scottish feedstocks.

In an effort to reduce atmospheric carbon dioxide (CO2) emissions and mitigate climate change, it has been proposed to sequester supercritical CO2 in underground saline aquifers. Geological storage of CO2 involves different trapping mechanisms which are not yet fully understood. In order to improve the understanding of the effect of chemical reaction on the flow and transport of CO2, these storage mechanisms are modelled experimentally and numerically in this work. In particular, the destabilising interaction between the fluid hydrodynamics and a density-increasing second-order chemical reaction is considered. It is shown that after nondimensional scaling, the flow in a given physicochemical system is governed by two dimensionless groups, Da/Ra2, which measures the timescale for convection compared to those for reaction and diffusion, and CBo', which reflects the excess of the environmental reactant species relative to the diffusing solute. The destabilising reactive scenario is modelled experimentally under standard laboratory conditions using an immiscible two-layer system with acetic acid acting as the solute. A novel colorimetric technique is developed to infer the concentrations of chemical species from the pH of the solution making it possible to measure the flux of solute into the aqueous domain. The validity of this experimental system as a suitable analogue for the dissolution of CO2 is tested against previous work and the destabilising effect of reaction is investigated by adding ammonia to the lower aqueous layer. The system is also modelled numerically and it is shown that the aqueous phase reaction between acetic acid and ammonia can be considered to be instantaneous, meaning that Da/Ra2 tends to infinity and the flow is therefore governed only by the initial dimensionless concentration of reactant in the aqueous phase. The results from the experiments and numerical simulations are in good agreement, showing that an increase in the initial concentration of reactant increases the destabilising effect of reaction, accelerates the onset of convection and enhances the rate of dissolution of solute. The numerical model is then applied to a real world aquifer in the Sleipner gas field and it is demonstrated how the storage capacity of a potential CO2 reservoir could be enhanced by chemical reaction.

Implementing effective and environmentally responsible carbon capture technologies is one of the principle challenges of this century. Successful implementation requires a host of engineering advancements, but also a fundamental understanding of the underlying physics, chemistry, and materials science at play in these highly complex systems. A large body of scholarship examines both current technologies as well as future strategies, but to date little exploration of the surface behavior of these systems has been examined. As these carbon capture systems involve uptake of gaseous CO2 to either aqueous or solid substrates, understanding the chemistry and physics governing the boundary between the two reactant phases is critical. Yet probing the unique chemistry and physics of these interfacial systems is very difficult. This dissertation addresses this knowledge gap by examining the surface chemistry of monoethanolamine and CO2. Monoethanolamine is a simple organic amine currently used in small scale CO2 scrubbing, and acts as an industrial benchmark for CO2 capture efficiency. The studies presented throughout this dissertation employ surface selective techniques, including vibrational sum frequency spectroscopy, surface tensiometry, and computation methodologies, in order to determine the behavior governing aqueous amine interfaces. The adsorption behavior and surface orientation of aqueous monoethanolamine is examined first. The results show monoethanolamine is present at the surface, highly ordered, and solvated. Perturbations to this amine surface from gaseous CO2 and SO2, as well as from liquid HCl, are examined in the remainder of the dissertation. Reactions between the amine and acids are shown to cause immediate changes to the interface, but the interface then remains largely unaffected as further reaction evolves. The studies presented herein provide a needed exploration of the interfacial picture of these highly reactive systems, with implications for future carbon capture materials and design.

The rapid electrification through natural gas in Mexico; the interest of the country to mitigate the effects of climate change; and the opportunity for rolling out Enhanced Oil Recovery at national level requires an important R&D effort to develop nationally relevant CCS technology in natural gas combined cycle power plants. Post-combustion carbon dioxide capture at gas-fired power plants is identified and proposed as an effective way to reduce CO2 emissions generated by the electricity sector in Mexico. In particular, gas-fired power plants with carbon dioxide capture and the sequential combustion of supplementary natural gas in the heat recovery steam generator can favourably increase the production of carbon dioxide, compared to a conventional configuration. This could be attractive in places with favourable conditions for enhanced oil recovery and where affordable natural gas prices will continue to exist, such as Mexico and North America. Sequential combustion makes use of the excess oxygen in gas turbine exhaust gas to generate additional CO2, but, unlike in conventional supplementary firing, allows keeping gas temperatures in the heat recovery steam generator below 820°C, avoiding a step change in capital costs. It marginally decreases relative energy requirements for solvent regeneration and amine degradation. Power plant models integrated with capture and compression process models of Sequential Supplementary Firing Combined Cycle (SSFCC) gas-fired units show that the efficiency penalty is 8.2% points LHV compared to a conventional natural gas combined cycle power plant with capture. The marginal thermal efficiency of natural gas firing in the heat recovery steam generator can increase with supercritical steam generation to reduce the efficiency penalty to 5.7% points LHV. Although the efficiency is lower than the conventional configuration, the increment in the power output of the combined steam cycle leads a reduction of the number of gas turbines, at a similar power output to that of a conventional natural gas combined cycle. This has a positive impact on the number of absorbers and the capital costs of the post-combustion capture plant by reducing the total volume of flue gas by half on a normalised basis. The relative reduction of overall capital costs is, respectively, 9.1% and 15.3% for the supercritical and the subcritical combined cycle configurations with capture compared to a conventional configuration. The total revenue requirement, a metric combining levelised cost of electricity and revenue from EOR, shows that, at gas prices of 2$/MMBTU and for CO2 selling price from 0 to 50 $/tonneCO2, subcritical and supercritical sequential supplementary firing presents favourably at 47.3-26 $/MWh and 44.6-25 $/MWh, respectively, compared with a conventional NGCC at 49.5-31.7 $/MWh. When operated at part-load, these configurations show greater operational flexibility by utilising the additional degree of freedom associated with the combustion of natural gas in the HRSG to change power output according to electricity demand and to ensure continuity of CO2 supply when exposed to variation in electricity prices. The optimisation of steady state part-load performance shows that reducing output by adjusting supplementary fuel keeps the gas turbine operating at full load and maximum efficiency when the net power plant output is reduced from 100% to 50%. For both subcritical and supercritical combined cycles, the thermal efficiency at part-load is optimised, in terms of efficiency, with sliding pressure operation of the heat recovery steam generator. Fixed pressure operation is proposed as an alternative for supercritical combined cycles to minimise capital costs and provide fast response rates with acceptable performance levels.

Geological carbon dioxide (CO2) storage in the United Kingdom (UK) will likely be entirely offshore, which may lead to the production and disposal into the sea of reservoir waters to increase storage capacity, or through CO2-Enhanced Oil Recovery (CO2-EOR). These produced waters have the potential to contain significant concentrations of trace metals that could be of harm to the environment. Batch experiments with CO2, warm brines, and reservoir sandstones were undertaken for this thesis to determine concentrations of 8 trace metals (arsenic, cadmium, chromium, copper, mercury, nickel, lead, zinc) which could be leached during CO2 storage in 4 UK North Sea hydrocarbon reservoirs. A sequential extraction procedure (SEP) was also used to determine the potential mobility of these metals under CO2 storage from mineral phases making up the reservoir samples. The results broadly showed that mobilised trace metal concentrations were low (parts per billion, ppb) in the batch experiments, with the exceptions of nickel and zinc. These metals were associated with carbonate and some feldspar dissolution, with other metals apparently desorbed from mineral surfaces, probably clays. The results of the SEP, however, were a poor predictor of actual mobility with respect to the batch experiments, although useful in determining the distribution of trace metals within the defined mineral phases (water soluble, ion exchangeable, carbonate, oxide, sulphide, silicate). In addition, fieldwork was carried out at Green River, Utah, to collect 10 CO2-driven spring water samples and 5 local aquifer rock samples. This area was used as a natural analogue for CO2-mobilised trace metals from sandstone aquifers. Trace metal concentrations in spring waters were very low (ppb) and batch experiments using Utah rock samples, spring water collected from Crystal Geyser, and CO2 confirmed very low mobility of these metals. The SEP was repeated for the Utah reservoir rocks, but again was not a reliable predictor for actual mobility, other than to confirm that overall bulk concentrations of trace metals was low. Comparison of trace metal concentrations from the batch experiments with data from UK North Sea oil and gas produced waters shows that overall, concentrations mobilised in batch experiments are within the range of concentrations across all North Sea fields reporting their data. However, on a field-by-field basis, some CO2 mobilised concentrations exceeded those currently produced by oil and gas activities. Furthermore, average batch experiment trace metal loads are higher than average oil and gas produced waters, and in some cases exceed international guidelines. Therefore, while the majority of trace metals have low mobility and therefore low environmental impact, this should be assessed on a case-by-case basis. Regular monitoring of dissolved constituents in produced waters carried should also be carried out, particularly in the initial stages of CO2 storage operations, with remedial action taken as required to reduce the environmental impact of offshore carbon capture and storage.

No description available.

Carbon dioxide levels have been steadily increasing over the past decades; as of 2019 (411 ppm), CO2 levels are at their highest in over 40 years (330 ppm in 1977); consequently, regulations in certain areas require the reduction of CO2 emissions to combat this trend. For effective carbon capture, we require a sorbent that has high adsorption capacity, stability, and recyclability; in addition, an efficient and economical way to release the captured gas is needed as well. Metal-organic frameworks (MOFs) possess a high surface area for adsorption, but releasing the stored gases requires additional energy input that limits the overall efficiency of carbon capture. Ag/UiO-66 provides a thermally stable complex with a high surface for adsorption of CO2 while the silver nanoparticles utilize light-induced local heating to act as a photoswitch for dynamic release of CO2; visible light in the 400 nm spectrum is used to liberate the captured CO2.

This Master's thesis aims to examine Canada's historical and contemporary attempts to establish a sustainable hydrogen market in Canada. Specifically, my research sought to answer whether hydrogen is poised to take off within the current hype cycle or will be stifled, such as in previous attempts. My research aimed to explore this question by examining and comparing historical and contemporary literature relevant to hydrogen development in Canada. My research utilized an ESPELT analysis and involved interviewing multiple experts from across the country to reveal any nuances that underline the barriers and opportunities for determining the viability of Canada's domestic hydrogen market within the contemporary context.