In this thesis, analytical and computational models have been created for the electroreduction of CO2 in gas-diffusion electrodes. It initially covers the creation of a 1D analytical model of CO2 mass transport and reaction in a gas-diffusion electrode catalyst layer in an electrolyser with a flowing catholyte layer. This model balances the diffusion of CO2 through the porous media against the reaction of CO2. Both electrochemical conversion, with concentration dependent Tafel kinetics, and chemical reaction with OH- in the bicarbonate buffer system, rapidly consume CO2. It shows that the OH- produced in the reduction reaction and competing hydrogen evolution reaction lead to an alkalinity problem, in which large fractions CO2 are converted to bicarbonate and carbonate instead of the intended electroreduction product. This problem is pervasive in the catalyst layer environment, and the rising pH further causes significant increases in local carbonate concentrations, limiting the CO2 solubility through the salting-out effect. The carbonate concentrations can approach the solubility limit in the electrolyte and precipitate with cations into solid carbonate crystals in the pore structure.

Rudimentary optimisation is performed on this 1D system, and it determines that the effectiveness of a catalyst layer is governed to an extent by the Thiele modulus. Furthermore, a thick catalyst layer is usually underutilised when there is insufficient CO2 partial pressure in the gas feed or excessive cathode potential. In these cases, the regions of the catalyst furthest from the gas supply perform very little CO2 electroreduction, but still perform hydrogen evolution. This hydrogen evolution produces OH- ions that further consume CO2 and consumes electricity that would ideally instead be used to produce the more valuable products of CO2 reduction.

The 1D model necessarily used averaged values for components that depend on the perpendicular flow direction, namely the flowing catholyte channel and the reactant gas CO2 channel. We note that this treatment is insufficient to describe the whole electrolyser, as CO2 conversion to carbonate and OH- production create a developing concentration boundary layer. Similarly, the partial pressure of the gas channel CO2 will vary along the electrolyser as it reacts away.

To address these issues, the model is converted into a computational 2D system, solved in COMSOL Multiphysics. This also permits the inclusion of some of the more convoluted effects of ionic strength and temperature on the system. Homogeneous reaction rates, anodic and cathodic reaction rates, pH, and reaction equilibrium potentials and constants are all corrected in this way. This gives a more detailed representation of the physical processes, but given the complicated forms of the corrections it becomes far more difficult to interpret the interactions behind observed phenomena when compared to the analytical model. With some additional computational methods of domain decomposition and variable recasting, the model is applied to both a small lab-scale scenario and an upscaled metre-long channel, to demonstrate the scaling relations and limitations of a typical CO2 electrolyser with flowing catholyte. It shows that the reaction environment at the inlet is far more favourable than further down the stream, as the reactant partial pressure is higher, the local catalyst layer pH is lower, the local CO2 solubility is higher, the catholyte is purer, and the catholyte concentration boundary layer is thinner. The model allows us to see that the majority of reactant and current utilisation limitations come from unabated hydrogen evolution in the poorly utilised regions, similar to what was found in the perpendicular direction in the 1D model. We propose some methods to mitigate these limitations. One of these methods is the selective removal of catalyst in these poorly utilised areas, to ensure that limiting kinetics and limiting mass transport share similar values and hydrogen evolution only occurs where necessary.

With the rudimentary hypothesis of selective catalyst removal showing some promising results, we return to a readily optimisable 1D system in the flow-wise direction of both a simple flow-through reactor and a gas-diffusion electrode with flowing catholyte. We find that variable catalyst loading can act as a modifier of the dimensionless Damk\"{o}hler number that typically governs the performance of such a system. The effect is more profound in a gas-diffusion electrode however, so we create a numerical framework in which we can perform functional optimisation to find ideal loading profiles for a range of electrolyser setups and operational loads. We found that high single-pass conversion is associated with lower reaction selectivity, and subsequently constructed a more robust financial cost weighted metric. This metric reveals that many electrolyser setups can be improved by reducing the amount of catalyst used further down the channels, as the reduced cost of electricity spent on the hydrogen evolution reaction far outweighs the reduction in product yield and reactant utilisation. Furthermore, the optimisation process reveals that the most economically feasible setups for contemporary costs are categorically those that operate at minimal cell voltage and single-pass conversion, as
electrolysis cost is dominant, even in cells with optimised catalyst loading. This high electrolysis cost, exceeds reactant cost and separation costs, so a low single-pass conversion is preferable to maintain a high reactant availability for efficient electrolysis in the catalyst layer, even if this leads to higher product stream separation costs due to more unreacted CO2 in the outlet.
We conclude with a recommendation for a focus on minimising electrolysis cost and maximising long-term stability and scalability, with less of a focus on reactant utilisation and intensive upstream or downstream processing, as the former attributes are of greater financial significance. @en

The negative environmental effects of large-scale use of fossil fuels, chemicals, and energy-intensive processes are forcing us to develop green alternatives to mitigate the climate crisis. Electrochemistry, powered by renewable energy, provides us with a direct way to produce precursors or materials from green electricity and benign reagents such as water, carbon dioxide (CO2), or oxygen. A widely known example is water electrolysis to produce hydrogen as a green fuel and chemical building blocks for other chemicals. Alternatively, CO2 can be fed to an electrolyzer to produce sustainable carbon-based materials - such as pharmaceuticals, paints, and synthetic fuels - that are otherwise obtained from fossil fuels. Electrochemistry is therefore a versatile and promising technology that could provide a strong foundation for sustainable alternatives to various environmentally unfriendly processes.
Because electrochemical systems are often studied as replacements for well-established and optimized industrial processes, the benchmarks to achieve an economically viable and competitive status are high. Most importantly, the processes must be efficient with materials and energy,
resulting in requirements such as high current density, energy efficiency and product selectivity. These are hampered in many systems by poor solubility of reagents in water, such as the aforementioned CO2 and oxygen. The low reagent concentration results in reagent depletion, intensified competition with parasitic side reactions, and low selectivity at industrially relevant current densities. Such systems are severely limited by the slow mass transport and availability of reagents towards and at the electrode surface.@en

Crystallization is one of the most widely used purification and separation processes applied in a multitude of industries such as pharmaceuticals, food & beverages, agriculture, and fine chemicals. However, the initial step of the crystallization process, nucleation, is still poorly understood and highly stochastic. As a result, most crystallization processes lack proper control over the properties of the crystals produced. Among many techniques for achieving better control over the nucleation process, the application of non-photochemical laser induced nucleation (NPLIN) has gathered significant interest. This is because of its potential to improve product quality in crystallization processes by directly controlling the nucleation rate, both spatially and temporally. Additionally, NPLIN can induce crystallization in solutions that would otherwise take a long time to nucleate, offering a unique advantage over traditional methods. However, despite its promising capabilities, NPLIN is not widely used in practice yet. The fundamental mechanism behind NPLIN is not fully understood, making it unclear how it should be applied effectively in practice and for which systems NPLIN could be beneficial.

This Ph.D. project aims to delve into the fundamental mechanisms of NPLIN, by examining how specific laser and solution parameters influence nucleation kinetics, leveraging innovative experimental setups. Laser parameters being studied include laser-exposed volume, laser irradiation position, laser intensity, and laser wavelength, and solution parameters include supersaturation levels, solution filtration, and the presence of impurities or dopants, particularly nanoparticles.

The thesis begins with a comprehensive review of the experimental and computational literature on NPLIN. It then presents a detailed study on the effect of the laser-exposed volume and laser irradiation position on the nucleation probability within partly illuminated supersaturated aqueous potassium chloride solutions. An increase in the laser-exposed volume resulted in a higher nucleation probability and a higher number of crystals per nucleated sample. Furthermore, laser irradiation, particularly through the air/solution interface, not only enhances nucleation probability but also influences the formation of different crystal morphologies. These observations are partly explained by the Nanoparticle Heating mechanism and the Dielectric Polarization model (Chapter 2).

The research then transitions to a microfluidic platform, which allows for high-throughput and crystallization detection using the deep learning method. This innovative approach addresses the need for large data sets in NPLIN research, which has been a significant challenge due to the manual nature of traditional experiments. The study examines the effects of laser intensity, wavelength, supersaturation, solution filtration, and intentional doping on nucleation probability in supersaturated potassium chloride solutions. Higher laser intensities and increased supersaturation significantly enhance nucleation probabilities. The laser wavelength effect was only observed for 355 nm at higher laser intensities. Solution filtration suppresses the NPLIN effect, whereas the addition of nanoparticles as dopants into the solution not only increases the NPLIN probabilities but also affects the crystal morphology. The results highlight the importance of impurities in the solution and support the hypothesis that nanoparticle or impurity heating could be the key mechanism in understanding NPLIN (Chapter 3).

The study finally investigated the effects of solution filtration, laser intensity, and nanoparticle properties including nanoparticle concentration and material on NPLIN probability in supersaturated aqueous urea solutions. The study highlights the significant role of impurities in NPLIN, demonstrating that doping with different nanoparticle materials leads to varied nucleation probabilities. In particular, gold nanoparticles were found to enhance nucleation more effectively than silica nanoparticles. Additionally, it was observed that NPLIN probabilities followed a Poisson distribution to changes in nanoparticle concentration and laser intensity respectively. The findings in this chapter enhance our understanding of the critical role of impurities in comprehending the NPLIN mechanism (Chapter 4).@en

With the increasing importance of renewable electricity as a primary source of energy on the planet, the importance of electricity–based technologies in process industries is expected to rise as well. Microwave heating is a well–known electricity–based industrial technology that is used in a variety of commercial applications.

This work addresses challenges and explores opportunities for industrial–scale utilization of microwave heating in heterogeneous catalytic gas-phase reactors. Through critical analysis of microwave applicators, the thesis highlights the limitations of traditional cavity–based reactors and underscores the potential of traveling–wave systems for achieving uniform heating profiles in heterogeneous catalytic flow reactors. The contribution of the thesis lies primarily in the design and optimization of traveling microwave reactors (TMRs). Challenges associated with catalyst heating profiles and process scale–up are addressed by introducing a coaxial waveguide structure and a tailored catalyst loading pattern. The TMR model demonstrates its effectiveness in accurately predicting temperature profiles and reaction dynamics along the reactor through simulation studies and experimental validation. Furthermore, the thesis introduces the Reverse Traveling Microwave Reactor (RTMR) as a novel reactor concept aiming to minimize temperature gradients along the catalyst bed by periodic reversal of microwave irradiation. Simulation–based studies showcase the RTMR’s potential in achieving temperature uniformity within the catalyst bed, offering new insights into reactor design and scale–up considerations for microwave–assisted catalytic flow processes.@en

This thesis presents a novel method for using sodium borohydride (NaBH₄) as a circular hydrogen carrier, addressing the current lack of commercially viable approaches for hydrogen storage in NaBH₄. The traditional approach of using NaBH₄ for circular hydrogen storage through hydrolysis was reevaluated, leading to the development of a novel reaction system consisting of solely a one-pot reaction for the hydrogen release process. Alcoholysis reactions were performed using different alcohols resulting in the selective formation of borate esters. Subsequently, successful regeneration of the gained boric ester to NaBH₄ was achieved by adopting reaction conditions from the Brown-Schlesinger process, thus realizing a complete circular hydrogen storage process for the proposed system. Attempts were made to minimize the energy intensity of NaBH₄ synthesis by exploring alternate reaction pathways that could potentially lower reaction temperatures. This involved the use of radical sources such as sodium naphthalenide and sodium biphenyl, leading to the formation of boron radical anions that facilitated homolytic hydrogen cleavage which initiated borohydride formation.
To address the challenge of heat transfer during hydrogen release, a heat transfer limitation model was developed. Real-time data was collected to extrapolate temperature profiles for different NaBH4 quantities and their respective proportions of reactants and reactor volumes for predicting temperature trajectories. This data was functionalized and used for the prediction of cooling water temperature profiles and minimum cooling water flow rates upon up scaling. It was seen that heat transfer in this system has a linear correlation to the amount of reacting NaBH₄ upon scaling. Therefore, the envisioned hydrogen release process is not assumed to be forming a problem for the reactor design upon up scaling with regards to heat transfer limitations.
Furthermore, an economic assessment was conducted to evaluate the viability of the envisioned system. A process flow diagram of the alcoholysis reaction pathway was initially constructed. Subsequently, this diagram served as the foundation for establishing an energy balance for both the hydrogen release process and the NaBH₄ regeneration process, which enabled a comparative examination between the hydrolysis pathway and the proposed alcoholysis pathway.

Enhancing the efficiency of industrial water electrolysis for hydrogen production is vital for the energy transition. In Alkaline Water Electrolysis (AWE), hydrogen is produced at the cathode, and the bubbles are formed when the local hydrogen concentration exceeds the solubility limit. It is important to understand the exact local conditions that result in the nucleation of bubbles in this multi-phase and reactive system. With modeling, it is possible to gain insight into the relation between various local properties, but the model needs to include all relevant physics and chemistry. Thus, this work focuses on the multi-species electrochemical transport phenomena with reaction occurring on the electrode-electrolyte interface.

The electrochemical transport phenomena and the bubble nucleation are meso-scale phenomena occurring at the electrode-electrolyte interface. Lattice Boltzmann Method (LBM) is well suited for modeling meso- scale behavior but it is computationally memory expensive. Consequently, a hybrid approach combining Finite Difference Method (FDM) and LBM has been developed to simulate transport phenomena in the migration-diffusion problem with heterogeneous reaction kinetics. The Debye-Hückel theory is used as a benchmark to validate the developed model. Subsequently, the model is employed to simulate the transport phenomena occurring in the hydrogen half-cell of AWE, with a specific focus on the Hydrogen Evolution Reaction (HER) governed by the Butler-Volmer kinetics equation.

The model captures the dynamic evolution of physical parameters such as electric potential, concentration of species, and fluxes within the system particularly in the Electric-Double layer (EDL). The effect of electrode potential on the distribution of species involved in the reaction are studied by performing simulations for different electrode potential. The influence of secondary fluxes on the species distribution
is studied by implementing a spatially varying boundary condition to the reacting site. Finally, the formulated methodology is extended to solve a multi-phase system with species transportation occurring
around a catalyst particle.

Experimentally investigating the nanoscale behavior at oxide-electrolyte interfaces has proven to be extremely challenging. Molecular Dynamics (MD) simulations have arisen as a potential computational alternative to gain atomic level insights at these interfaces. But how accurately do these simulations represent the physics and chemistry at the interface? In many situations we do in fact not know. Validation at the interface remains challenging. The force fields used in MD simulations, that describe the inter-particle interactions, are generally optimized for purposes deviating considerably from interfaces. Yet, these same force fields are blindly used to model surface-fluid interactions, yielding wildly varying results of for example ion adsorption. This dissertation tackles the problem of simulating interfaces by critically looking at MD simulations and proposing novel solutions, both for MD simulations in general and specifically targeting their validity and limitations with regards to modeling interfaces… @en

Separation of particles from suspensions has been an integral part of many industrial, chemical and biological processes. Traditional methods such as sieving, flocculation, centrifugation etc. have many demerits. This has lead to an interest in unconventional separation methods that use physical properties of the particles. Acoustophoresis is one such method that has gained popularity in recent times. Acoustophoretic separation is based on the density contrast between the particles and the medium, as well as the size of the particles. A particle in a medium in which an acoustic field has been applied, experiences an acoustic force. This acoustic force is greater in standing waves than traveling waves, which is why acoustophoretic devices generally use standing wave fields. Particles with positive contrast factor are pushed to the pressure nodes; once the particles reach the nodes, they are trapped. If the medium is in flow, the particles also experience drag force. The interplay between the drag and the acoustic force forms the basis for separation. Standing wave fields can further be distinguished as static fields or dynamic acoustic fields (DAF). In a static field, the nodes are stationary, while in DAF, there is movement of the nodes, caused by variation of source frequency. Here, the tendency of different-sized particles to follow the nodal movement gives rise to separation. DAF devices seem preferable when separation needs to be done on a larger scale.In this thesis, two novel DAF devices were studied; one device works on the principle of frequency sweeping, while the other works on frequency modulation. Both devices are 3D printed, and have two inlets and two exits, with separation occurring in an acoustic chamber where the DAF acts. Both devices are multi-nodal & milli-fluidic. The samples to be separated consist of polyethylene particles of a continuous size distribution between 32-106 µm, dispersed in water. The devices were tested at a total channel flow rate of 1000 mlh-1 (Reynolds number of 20). The aim was to understand how varying the flow and acoustic field parameters affect the separation/filtration performance of the devices. This was done by defining a “threshold size” or the cut-off size at which the entire particle distribution is divided into two separate distributions. Flow and acoustic field parameters were adjusted to see how the threshold size increases/decreases.The analysis for each device was done by a parametric study using Design of Experiments (DOE). First the available features (both design and operation) were studied and suitable parameters and their values were selected. The DOE was then designed, having 27 combinations of parameters known as ‘runs’. Each run of the DOE was first simulated on an available 2D COMSOL model, followed by experimental validation. The DOE was then analysed using both theoretical and actual values, to find out the parameters that had the maximum effect on the threshold size, and their respective trends.

The CFD modeling based on the two-fluid model (TFM) was used on studying the novel indirectly heated bubbling fluidized bed steam reformer (IHBFB-SR). This is a collaborative project between Petrogas and TU Delft for testing the advance’s reactor configuration, which indirectly supplies the heat via radiant burner on the center toward the surrounding bed, thereby improving heat transfer efficiency and reduced the losses. The present work aimed to observe the hydrodynamic and heat transfer of the reactor by first employing air as the fluidizing gas and corundum (Geldart B size) as the bed material. The minimum fluidization condition, bubbles development, and voidage profile are the main objectives for the hydrodynamic simulation. In the heat transfer study, the effect of radiative heat transfer, bubbles and voidage profiles, and different radiative models (P1 and DO) on the heat transfer mechanism were examined. The 2D and 3D models were built, and three drag models: Gidaspow, adjusted Syamlal, and EMMS/Bubbling was employed. The simulation results were then compared to the experimental data obtained, such as minimum fluidization flowrate, pressure drop, bed expansion, and temperature profile on a specific flow rate.

Initially, a grid independency test was conducted using five different grid sizes. It is concluded that the appropriate grid size for simulating the IHBFB-SR with a bed material particle size of 0.496 mm should be at least 7.5 mm or 15 times the corundum particle size. The present research used 2.5 mm or five times dp. The minimum fluidization obtained was in the range of 14-16 kg/h based on both 2D and 3D simulation. Nonetheless, if primarily refers to the 3D model results, the minimum fluidization condition should lie around 14 kg/h. Three drag models have also been compared. It was found that the adjusted Syamlal gives the closest result compared to the experimental data. Nevertheless, the drag modification, based only on minimum fluidization conditions like modified Syamlal, tends to overpredict the drag coefficient on the entire range of solid volume fraction. There are also no significant differences in the bubbles or voidage profiles among those three drag models. Adjusted Syamlal has a slightly larger bubble while Gidaspow and EMMS bubbling has a bit smaller one. The expected better result of using the EMMS bubbling drag model does not appear to have a considerable impact on the case of Geldart B or larger particles. There was also an underprediction of pressure drop and bed expansion on the simulation. Two major factors were the absence of proper particle shape representation through a sphericity factor and the lack of precise simulation of particle size distribution. Only a perfect rounded sphere of corundum with a sphericity factor of one and one uniform size of the particle was assumed.

In the case of heat transfer simulation, bubbles and voidage effect firstly studied. It was found that the increase of the bubbles frequency and size, as represented on the voidage profile, would improve the heat transfer process indicated by the increase of the heat flux. The bubbles’ occurrence on the bed plays a critical role in the mass transfer’s improvement from and to the vicinity of the radiant burner wall, thus increasing heat transfer. In contrast with the voidage, the increase of superficial gas velocity does not directly influence the heat flux. It was also proved that the radiative heat transfer improved the overall heat flux in this bubbling fluidized bed reactor by about 16.11 %. Though it appears small, this contribution fits the range of other proven works, with a similar operating environment and particle size used. There are two different radiative models performed in the simulation: first-order spherical harmonics method (P1) and discrete ordinate method (DO). Both models presented a similar trend, with P1, has a slightly higher magnitude. However, the P1 model shows a peculiar result of having a strange lower temperature lower on the bottom part of the bed. On the contrary, that is not the case for the DO, which is well known for its accuracy but a higher computational cost demand. It is then concluded that for the present setup, the DO model could perform better. Lastly, the overall heat transfer process was investigated. Since no specific experimental data available for validating the heat transfer properties, only the final steady temperature values of five different thermocouples were used. Comparing these two, it was found that the present model did not give satisfactory results due to overprediction of air temperature above the bed and underprediction of bed temperature at the same time. Some improvements are required, as will be presented in the recommendations section.

For drinking water treatment applications, it is possible to predict the external porosity of an expanded bed of granular activated carbon in fluidized conditions. A new model has been developed with a 2% relative prediction error.

In order to supply sufficient and safe drinking water, water utilities use a treatment train consisting of several unit processes. One of these treatment unit processes is granular activated carbon (GAC) filtration, a crucial unit process widely used for its filtration and adsorption capabilities as a barrier for undesired macro and micro-pollutants. The point of interest for this research is one of the critical steps in the filtration part of the unit process, the backwashing procedure.
Backwashing is a cleaning procedure, which consists on stopping the normal operation of the filter and reversing the normal downward water flow. This upward flow leads to the expansion of the filter’s media and washes away any undesired particles caught in between and on the surface of the media. Inadequate backwashing can lead to unwanted operational outcomes, for instance, solids accumulation and mud balls or media washout, resulting in costly operational expenses. In addition, currently there is a tendency for water utilities to explore new sustainable GAC filter media, which have different expansion tendencies. These operational requirements create the need for the development of prediction models to estimate the expansion degree of the filter bed during backwash procedures. Additionally, a deep understanding of the phenomena that governs this unit process is required to increase its resiliency.

The main goal of this research was to predict the expansion degree of GAC in the water phase. In order to achieve this goal, two innovative approaches combining advanced laboratory techniques and prediction models was the course of action. The first approach was the development of an input model known as the AquaGAC model, to describe the different characteristics of porous media and perform checks using calculated and measured hydraulic parameters. With the combination of the AquaGAC input model and an existing fluidization model (FBI) that computed the expressions of five classical models, the prediction of porosity of the performed experiments was achieved. The second approach consisted on using a data driven model, which consisted on the combination of the outputs the FBI and AquaGAC models with several morphological parameters to derive empirical expressions that accurately estimated the external porosity.

Obtained results suggest that using the 10th percentile of the particle diameter in classical models, delivers porosity prediction errors of 10% in comparison to the 50th percentile used in practice with errors up to 25%. Based on symbolic regression, data driven models produced expressions with accurate correlations with porosity errors ranging from 2-5%.

The results of this research are encouraging as the AquaGAC input model can serve as a basis for other fluidization models that use porous media with different shapes. Recommendations are made to improve the experimental set-up, the accuracy in estimating the particle envelope and wet densities, and the quantitative evaluation of the orientation. Future research of the expansion behavior of mixtures is also recommended.

Zero Emission Fuels(ZEF) is a start up, and ZEF is building a micro plant which is ableto produce bio-methanol from solar energy and air. CO2and H2O are absorbed from theair, the H2O is split into H2which is fed together with the CO2in the methanol synthesisreactor. The reaction product is distilled and Grade AA MeOH is the product. Thisresearch the focus is on the continuous Direct Air Capture unit. The component consistsof 2 sub components, the absorber and the desorber. In the absorber the amine is broughtin contact with the air and absorbs CO2and H2O. As pure CO2and H2O molecules areneeded, the amine is desorbed in the desorber.This research specifically focuses on the desorption part of the DAC, amines(PEI andTEPA) are used to capture the CO2and H2O. The CO2is captured in two ways, via thecarbamate and the bicarbonate route. Carbamate is formed with primary and secondaryamines, bicarbonate is formed with the help of H2O and protonated primary, secondaryor tertiary amines. Bicarbonate is formed at loadings higher than 0.4 [mol CO2/ mol Namine], as the absorption capture capacity is low due to the low CO2partial pressure inthe air, this means that bicarbonate is not formed in the range of ZEF. After absorption30 wt% H2O and the CO2loading is expected to be 1.5 [mol CO2/ mol N amine].A VLE experiment is done to find the equilibrium between CO2in the gas phase andCO2in the amine, using the apparatus is was also possible to find the H2-Amine VLE.The experiment done with a 30 wt% failed due to high viscosity after which the solutionwas not homogeneous anymore. Adding more H2O up to 70 wt% solves the problem.However, the VLE is not accurate enough in low loading range(ZEF range. But, usingtwo isotherms, at 80 and 120°C the heat of absorption can be calculated. The results isa heat of absorption of -73.6 and -68.2 [kJ/mol CO2] for TEPA and PEI, respectively.To find the total desorption of CO2and H2O a desorption experimental setup isbuilt, experiments are performed at three pressures(50 100 and 200 mbar) and increasingtemperatures steps(80,90,100,110,120°C) . As the H2O evaporated at low temperature(<80°C). At higher temperatures than 90°C only CO2was present in the gas phase, hencethe partial pressure is equal to the total pressure. The output of CO2increases withdecreasing pressure and increases with temperature. The maximum output is equal to0.9 [mol CO2/ kg amine] using TEPA. The output of TEPA is twice as high as the outputof PEI.Using the experimental data from both tests, an energy model is made find the energypenalty of the desorption component. A base case study, a simple one-stage flash vesselat T = 120°C and p = 100 mbar, a total energy penalty of 18.1 and 33.6 MJ/ kg CO2,TEPA and PEI respectively. By altering the pressure and temperature the energy penaltycan be reduced to 16.6 [MJ/ kg CO2]. As the CO2demand is known, the correspondingneeded power is equal to 159 [W]. A design is suggested to put two flash vessels in parallelto reduce the H2O output of the system. At at temperature of 100 and 110°C with aconstant pressure of 100 mbar, a minimum of 15 [MJ/ kg CO2] is reached, a reductioni of 17% compared to the base case. Using a pinch analysis 93 [W] of the total 159 [W]can be retrieved by heat integration. Furthermore, the integration of a specially designedsolar boiler could provide the remained 66 [W] with heat

This work focuses on creating a recipe for parametrizing flow around assemblies of non-spherical particles. A multi-relaxation time lattice Boltzmann method (MRT-LBM) is used to simulate the flow. The research focuses on 3 different developments. First, different boundary conditions available in the literature for LBM are tested to identify the best for the flow problem. The second part of the thesis focuses on developing more widely applicable scaling laws for drag and lift of various isolated non-spherical particles. In the third part, a recipe to describe hydrodynamic forces on assemblies of axisymmetric, non-spherical particles is proposed. With the described parameters, drag, lift and torque correlations are proposed accordingly. This research is funded by the European Research Council under its consolidator grant scheme, contract no. 615096 (NonSphereFlow).@en

Noise generated due to flow over corrugated pipes has extensively been studied, because of its presence in various engineering applications. Flexible risers used in the oil and gas industry are one of these applications, where noise is produced due to corrugations present at the innermost layer of the riser. Dry-gas flow through a corrugated pipe generates an unstable shear layer over each of the corrugations. Under certain conditions, this shear layer can roll up into discrete vortices, which impinge on the downstream cavity edge, producing pressure pulsations. When the frequency of impingement matches with one of the natural pipe frequencies, a ‘lock-in’ mechanism causes intensification of the associated noise and vibrations, which can have serious implications on the structural integrity of the corrugated pipe. This phenomenon is called Flow Induced Pulsations (FIP). Liquid injection in a corrugated pipe with gas flow has shown the potential to mitigate whistling caused by FIP. A number of mechanisms play a role in the whistling mitigation. It is shown in literature that the filling of cavities due to liquid film or rivulets present on the pipe wall is an important mechanism. The cavity filling results in an altered cavity geometry, which changes the shear layer dynamics. The effect of liquid and gas flow rate on the cavity filling, however, remains unknown. The present work aims to study the liquid filling behaviour of a single cavity, due to a gas flow driven liquid film.
An experimental setup is constructed which consists of a rectangular channel containing a cavity. Liquid is injected in the channel as a film at the channel wall, which is driven upward by gas flow. The liquid film thickness upstream of the cavity is measured first, followed by the cavity filling itself. Both measurements are performed using a Laser Induced Fluorescence (LIF) based technique. After several post-processing steps, the film thickness and cavity filling are quantified.
At low liquid flow rates, a partial film is created at the channel wall with a dry patch at the center. Increasing the liquid flow rate results in a full film covering the entire channel width. The film thickness varies in the transverse direction due to the presence of localized horseshoe shaped disturbance waves on the liquid film. Overall, the film cross-sectional area increases with increasing liquid flow rate, either due to an increase in film thickness of full films, or an increase in width of the partial films. The liquid film fills up the cavity, accumulating mainly at the upstream edge. The downstream edge remains relatively free from liquid. The amount of filling is found to increase with increasing local film thickness at the measurement position away from the channel side-wall. Changes in the cavity geometry due to liquid filling are estimated based on the cavity effective depth and length. The effective cavity depth does not significantly change and only decreases by 8% with a 25% increase in filling ratio. However, the effective length decreases substantially by 30% with a 25% increase in filling ratio. This could lead to a mode parameter value (ratio of cavity length to incoming gas momentum thickness), such that it does not fall in the range where whistling is observed, resulting in mitigation of whistling.