A methodology for the thermodynamic-kinetic evaluation of circulating systems as TSA carbon capture processes is developed and used in the assessment of a novel CFB configuration against a benchmark (co-current riser). The novel CFB features a counter-current adsorber, a counter-current regenerator and a riser, the latter element playing a double role of solids conveyer and co-current adsorber. The advantages sought by using a counter-current adsorber are not only the more efficient gas-solid contact mode with respect co-current, but also a low pressure drop derived from operation at lower gas velocities and hydrostatic head partially supported on the contactor internals. Knowledge of the adsorption equilibrium alone is sufficient to realise the much higher sorbent circulation rates required by co-current configurations –compared to counter-current– to meet the stringent carbon capture specifications of 90% recovery and 95% purity. Higher solids circulation rates imply higher energy requirements for regeneration, and therefore research and development of co-current gas-solid contactors cannot be justified in terms of searching for energy-efficient post-combustion carbon capture processes. Parallel experimental investigation in the operation and fluid dynamics of cold model CFB rigs is carried out with the purposes of: 1) providing information that may impact the process performance and can be fed into the mathematical model used in the theoretical assessment for more realistic evaluation, and 2) determine gas and solids residence time distributions (RTDs), which are used for the estimation of axial dispersion and comparison with published results in similar systems. Gas RTD data is generated using a tracer pulse injection-detection technique, whereas RTD for the solid phase is studied using positron emission particle tracking (PEPT). The PEPT technique proved to be adequate for the identification of flow regimes in the novel design of the counter-current adsorber, featuring inclined orifice trays. At low gas velocities the particles flow straight down through the tray holes, whereas at higher velocities the particles flow down in zig-zag, increasing the residence time of the particles and reducing the particle axial dispersion, both beneficial in terms of separation efficiency.

In oil and gas field operations, the dynamic interactions between reservoir and wellbore cannot be ignored, especially during transient flow in the near-wellbore region. As gas hydrocarbons are produced from underground reservoirs to the surface, liquids can come from condensate dropout, water break-through from the reservoir, or vapor condensation in the wellbore. In all three cases, the higher density liquid needs to be transported to the surface by the gas. If the gas phase does not provide sufficient energy to lift the liquid out of the well, the liquid will accumulate in the wellbore. The accumulation of liquid will impose an additional backpressure on the formation that can significantly affect the productivity of the well. The additional backpressure appears to result in a "U-shaped" pressure distribution along the radius in the near-wellbore region that explains the physics of the backflow scenario. However, current modeling approaches cannot capture this U-shaped pressure distribution, and the conventional pressure profile cannot explain the physics of the reinjection. In particular, current steady-state models to predict the arrival of liquid loading, diagnose its impact on production, and screen remedial options are inadequate, including Turner's criterion and Nodal Analysis. However, the dynamic interactions between the reservoir and the wellbore present a fully transient scenario, therefore none of the above solutions captures the complexity of flow transients associated with liquid loading in gas wells. The most satisfactory solution would be to couple a transient reservoir model to a transient well model, which will provide reliable predictive models to link the well dynamics with the intermittent response of a reservoir that is typical of liquid loading in gas wells. The modeling work presented here can be applied to investigate liquid loading mechanisms, and evaluate any other situation where the transient flow behavior of the near-wellbore region of the reservoir cannot be ignored, including system start-up and shut-down.

In order to investigate the two-phase flow behaviour in a complex reactor-typical geometry and to supply suitable data for CFD code validation, a model of the hot leg of a pressurised water reactor was built at FZD. The hot leg model is operated in the pressure chamber of the TOPFLOW test facility, which is used to perform high-pressure experiments under pressure equilibrium with the inside atmosphere of the chamber. This technique makes it possible to visualise the two-phase flow through large windows, also at reactor-typical pressure levels. In order to optimise the optical observation possibilities, the test section was designed with a rectangular cross-section. Experiments were performed with air and water at 1.5 and 3.0 bar at room temperature as well as with steam and water at 15, 30 and 50 bar and the corresponding saturation temperature (i.e. up to 264°C). The total of 194 runs are divided into 4 types of experiments covering stationary co-current flow, counter-current flow, flow without water circulation and transient counter-current flow limitation (CCFL) experiments. This report provides a detailed documentation of the experiments including information on the experimental setup, experimental procedure, test matrix and on the calibration of the measuring devices. The available data is described and data sheets were arranged for each experiment in order to give an overview of the most important parameters. For the cocurrent flow experiments, water level histograms were arranged and used to characterise the flow in the hot leg. In fact, the form of the probability distribution was found to be sensitive to the boundary conditions and, therefore, is useful for the CFD comparison. Furthermore, the flooding characteristics of the hot leg model plotted in terms of the classical Wallis parameter or Kutateladze number were found to fail to properly correlate the data of the air/water and steam/water series. Therefore, a modified Wallis parameter is proposed, which takes the effect of viscosity into account.

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In this thesis study, air bubble motion in counter-current water flow conditions in a vertical pipe is investigated experimentally. For this purpose, a test set-up was designed and constructed. Images of motions of single bubbles, having different diameters in the range of 3.0-4.8 mm, generated by specially designed bubble injectors were recorded by using a monochrome camera, an image capture card and a PC. Recorded video images were processed to obtain the necessary data for the The purpose of the study is to determine variation as a function of the equivalent bubble diameter, water flow velocity and related dimensionless numbers / Reynolds, Re / E&ouml / tv&ouml / s, Eo / and Weber, We, and is to investigate the bubble shapes and bubble travel paths. Bubble behaviour was investigated at six different counter-current water flow velocities (6.5 cm/s, 7.9 cm/s, 10.5 cm/s, 12.9 cm/s, 15.4 cm/s, and 18.2 cm/s) in addition to stagnant water condition which is taken as the reference case. The direction of the bubble motion is upwards and the direction of the water flow is downwards (i.e. counter-current). Distilled water was used in the experiments. The results of this thesis study for the stagnant water condition have shown good consistency with the previous theoretical and experimental studies found in the literature. For the studied range of bubble diameters, it is observed that the bubble average relative velocity for a certain bubble diameter is less under counter-current water flow conditions than that under stagnant water condition and the drag coefficient values for a certain bubble diameter is higher under counter-current water flow conditions than those under stagnant water condition.

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For the pharmaceutical industry, the manufacture of high value pharmaceuticals from natural products, chemical synthetic routes or fermentation processes all require intensive downstream processing steps to produce a pure final product. A small footprint liquid-liquid processing method would help to reduce the capital cost and process development time of this downstream processing. In this thesis, it is hypothesised that continuous liquid-liquid extraction can be achieved using a standard hydrodynamic counter-current chromatography (CCC) instrument by switching the flow of the liquid phases between normal phase and reversed phase intermittently, so separating a feed stream into two eluant flows. A model of the process was derived and tested on three scales of instrument, from the semipreparative to the pilot scale. The method developed, Intermittent Counter-current Extraction (ICcE) was compared to dual-flow counter-current chromatography (DFCCC), the classical method of applying continuous extraction using a counter-current chromatograph. ICcE was found to be advantaged due to the more stable phase volume ratio achievable in the columns and the ability to operate the procedure on standard commercial twin-column CCC instruments which operate at high g-field. The robustness of the ICcE method was successfully demonstrated across a range of phase system polarities and at high throughput (1kg/day on a preparative instrument) with model mixtures of pharmaceutical compounds. The effectiveness of this new processing method was confirmed on three industrially relevant case studies. Firstly a polar extract from natural senna pods to extract important sennosides, secondly an intermediate polarity highly complex active pharmaceutical ingredient waste stream to recover the main active component and thirdly a non-polar natural product extract to recover macrocarpal compounds. In summary, the ICcE method now offers another tool in the range of liquid-liquid separation methods available to the pharmaceutical and other high value industries.

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In the event of hypothetical accident scenarios in PWR, emergency strategies have to be mapped out, in order to guarantee the reliable removal of decay heat from the reactor core, also in case of component breakdown. One essential passive heat removal mechanism is the reflux condensation cooling mode. This mode can appear for instance during a small break loss-of-coolant-accident (LOCA) or because of loss of residual heat removal (RHR) system during mid loop operation at plant outage after the reactor shutdown. In the scenario of a loss-of-coolant-accident (LOCA), which is caused by the leakage at any location in the primary circuit, it is considered that the reactor will be depressurized and vaporization will take place, thereby creating steam in the PWR primary side. Should this lead to ¿reflux condensation¿, which may be a favorable event progression, the generated steam will flow to the steam generator through the hot leg. This steam will condense in the steam generator and the condensate will flow back through the hot leg to the reactor, resulting in counter-current steam/water flow. In some scenarios, the success of core cooling depends on the behaviour of this counter-current flow. Over several decades, a number of experimental and theoretical studies of counter-current gas¿liquid two-phase flow have been carried out to understand the fundamental aspect of the flooding mechanism and to prove practical knowledge for the safety design of nuclear reactors. Starting from the pioneering paper of Wallis (1961), extensive CCFL data have been accumulated from experimental studies dealing with a diverse array of conditions A one-dimensional two field model was developed in order to predict the counter-current steam and liquid flow that results under certain conditions in the cold leg of a PWR when a SBLOCA (small break loss of coolant accident) in the hot leg is produced. The counter-current model that has been developed can predict the pressure, temperature, velocity profiles for both phases, also by taking into account the HPI injection system in the cold leg under a counter-current flow scenario in the cold leg. This computer code predicts this scenario by solving the mass, momentum and energy conservation equations for the liquid and for the steam separately, and linking them by using the interfacial and at the steam wall condensation and heat transfer, and the interfacial friction as the closure relations. The convective terms which appear in the discretization of the mass and energy conservation equations, were evaluated using the ULTIMATE-SOU (second order upwinding) method. For the momentum equation convective terms the ULTIMATE-QUICKEST method was used. The steam-water counter-current developed code has been validated using some experimental data extracted from some previously published articles about the direct condensation phenomenon for stratified two-phase flow and experimental data from the LAOKOON experimental facility at the Technical University of Munich. / Romero Hamers, A. (2014). STUDY OF THE THERMAL STRATIFICATION IN PWR REACTORS AND THE PTS (PRESSURIZED THERMAL SHOCK) PHENOMENON [Tesis doctoral]. Editorial Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/36536 / Alfresco

Counter-Current Flow Limitation (CCFL) is of importance for PWR safety analyses in several accident scenarios connected with loss of coolant. Basing on the experiences obtained during a first series of hot leg tests now new experiments on counter-current flow limitation were conducted in the TOPFLOW pressure vessel. The test series comprises air-water tests at 1 and 2 bar as well as steam-water tests at 10, 25 and 50 bar. During the experiments the flow structure was observed along the hot leg model using a high-speed camera and web-cams. In addition pressure was measured at several positions along the horizontal part and the water levels in the reactor-simulator and steam-generator-simulator tanks were determined. This report documents the experimental setup including the description of operational and special measuring techniques, the experimental procedure and the data obtained. From these data flooding curves were obtained basing on the Wallis parameter. The results show a slight shift of the curves in dependency of the pressure. In addition a slight decrease of the slope was found with increasing pressure. Additional investigations concern the effects of hysteresis and the frequencies of liquid slugs. The latter ones show a dependency on pressure and the mass flow rate of the injected water. The data are available for CFD-model development and validation.