1,720,972 research outputs found
Template assisted synthesis of organic, inorganic and organic-inorganic hybrid hollow spheres
No full textprocess & energyMechanical, Maritime and Materials Engineerin
Characterization and Population Balance Modelling of Eutectic Freeze Crystallization
No full textMechanical Maritime and Materials Engineerin
VibroCav: Hydrodynamic Vibration and Cavitation Technology
No full textVibration and cavitation can be generated in many ways and serve many useful purposes. This study describes physical aspects of useful vibration and cavitation for a broad spectrum of applications at atmospheric or elevated pressures. After a review of available devices, hydrodynamic vibrating-body-in-pipe tools as described in patents by Ivannikov are identified as having a major potential and being largely unexplored. Major advantages of these tools are simplicity of construction, scalability, powerful effects and attractive frequency range for well cleaning applications. Self induced vibration with a free body colliding with the pipe wall causes alternating flow around the body with a water hammer effect that enhances the vibration and cavitation. Cavitation can thus be generated at lower flow rates and at higher backpressures than with passive tools such as orifices. Cavitational collapse at high backpressure creates exceptionally strong effects, giving access to novel applications. At backpressures where even water hammer enhanced cavitation ceases to exist, very strong vibrations persist to pressure levels encountered in deep wells. This unique dual enhanced vibration and cavitation behaviour of the tools is the key to vibrating-body-in-pipe technology for which the new name VibroCav was coined. The study focuses on VibroCav tools with balls, except for one series of tests with a so-called flip-flop body. Exploratory tests in a 350 bar test circuit in Assen lead to the design of a 50 bar laboratory closed test circuit installed in the 3ME lab in Delft with facilities to apply up to 10 bar backpressure and up to 40 bar pressure differentials over the tools. In the 50 bar test circuit many experiments were carried out, firstly with bottom supported balls in a straight pipe and secondly with hanging balls in a pipe with a conical outlet allowing remote adjustment of the gap between the ball and the pipe wall. The influence of water composition, gas content and various ball materials was tested. Selected high backpressure test were carried out with a 350 bar closed test circuit in Drachten. A total of 29 field trials on an industrial scale were carried out for cleaning the porous media around water and oil wellbores under widely varying conditions and 5 field trials were done to evaluate the potential of the technology for the removal of scale deposits in wellbores. The laboratory experiments with the 50 bar test circuit delineated various operational modes of the VibroCav tools as function of flow rate and backpressure with regimes designated as (i) vibration only, (ii) active cavitation always combined with vibration, (iii) no vibration and passive cavitation and (iv) no vibration and no passive cavitation. The vibration regime persists to the maximum backpressure that could be reached and probably to much higher pressures, however at high flow rate conditions and a narrow gap vibration ceases when the Re value increases beyond the point of drag reduction due to shifting of the boundary separation point (Re approximately 3 x 105 for unbounded flow). Active cavitation is just as passive cavitation subdued by increasing backpressure; but in this test circuit it has still been observed at a backpressure of 63 barg. With a bottom supported tool as used in this test circuit a significant path downstream of the ball is obscured and active cavitation closer to the gap might still exist. This is the basis for the expectation that for this tool active cavitation may survive up to 100 barg backpressure. Tools with a hanging ball, in which cavitation is more clearly visible, were not tested at such high backpressures. The influence of water quality and gas content proved to be insignificant. Lightweight balls showed in bottom supported tools violent vibration and strong active cavitation but were easily damaged by the high contact forces between the ball and the support. With hard steel balls and softer steel supports, bedding-in is observed due to contact forces beyond the elastic limit of the support. If the ball is softer than the support, the ball flattens, breaks or is otherwise damaged by the support. The field trials for cleaning porous media around wellbores combined with theoretical analysis provided valuable semi-quantitative understanding of the influence of frequency, source directivity, source energy, wellbore geometry and permeability damage on the penetration depth of sources for vibration based well cleaning. The most significant wave energy for cleaning porous media is provided by the slow Biot wave, which is a compressional wave in fluid in the interconnected pore network. The higher the virgin permeability of the rock and the lower the wave frequency the better is the penetration depth. Permeability deterioration due to pore fouling reduces the penetration depth of the cleaning treatment and with progressive fouling the pore damage may get out of reach of the cleaning tools. The limited number of scale removal trials showed significant potential of the VibroCav tools due to the combination of physical hammering, jetting, wave energy and shock waves of collapsing cavitation bubbles. The study provides a solid basis for a scientifically founded continuation of the development of VibroCav technology for many areas of application in several industrial sectors and should be regarded as the precursor for a range of innovating techniques.3MEMechanical, Maritime and Materials Engineerin
Model-Based Control of Industrial Batch Crystallizers: Experiments on Enhanced Controllability by Seeding Actuation
No full textCrystallization is one of the oldest separation and purification techniques. Batch crystallizers are widely used in production of fine chemicals, food ingredients, specialty chemicals, and active pharmaceutical ingredients. Control of the crystalline material properties is a challenging task due to complexity and nonlinearity of batch crystallization processes and the lack of reliable measurement and actuation techniques. The goal of the research presented in this thesis was to design, validate, and evaluate different model-based control strategies for industrial batch crystallizers. A systematic approach was adopted in the development of control strategies that satisfy the requirements of industrial control systems. The followed approach included a number of steps such as process modeling, model reduction, controllability analysis, and control-system design. In the iterative design process, a particular attention was paid to experimental validation of the full-order and reduced crystallization models, state estimators, and model-based controllers by making use of pilot crystallization facilities of different scale and type. As a result of an extensive experimental study, the seeding technology was shown to be the pillar of the designed model-based control systems as it resulted in a reproducible operation and an improved quality of the end product. The yield of the crystalline product was increased by using model-based predictive optimizing controllers. For the given chemical system and batch crystallizers, linear control techniques were shown to be as suitable as nonlinear control methods for application in the designed strategies for control of the crystallization process.Delft Center for Systems and ControlMechanical, Maritime and Materials Engineerin
Crystal Growth in a novel airlift crystallizer
No full textCrystal growth in a high electrolyte and ionic shear enviroment, minimizing attrition and maximizing control over crystal growth and size.IRSProcess and EnergyMechanical, Maritime and Materials Engineerin
Preferential crystallization of a racemic compound via its conglomerate co-crystals
No full textPreferential crystallization, as a powerful chiral resolution technique, is intrinsically limited to chiral molecules that crystallize as conglomerates. Many studies have been conducted on using chemical reactions to convert the target molecules, which originally form racemic compounds, into conglomerate-forming derivatives salts or by creating solvate, for the application of preferential crystallization. Up to this date conglomerate co-crystals of racemic compounds have never been applied as the intermediate for chiral resolution. In this study, preferential crystallization of the model compound Ibuprofen (IBU), originally a racemic compound, was carried out via its conglomerate co-crystal with 2,4-bipyridine ethylene (BPE) in heptane. Suitable operation conditions were selected based on pseudobinary phase diagram of the model compound system constructed under different IBU-BPE ratio. A unique measurement method combining polarimeter and Nuclear Magnetic Resonance (NMR) measurements was developed to identify the enantiopurity and the yield of the final product, which was a mixture of racemic IBU and IBU-BPE co-crystals, a likely result from this complex system. With respect to the results, preferential crystallization of IBU was successfully performed by slowly cooling down a saturated solution of racemic IBU-BPE, initially at T=57.5°C, after seeding it with S-IBU/BPE crystals to T=53°C with a cooling rate of 0.3°C/min. The recovered crystalline product contained pure IBU and a mixture of R-co-crystals and S-co-crystals with a yield of 44%, with the amount of S-co-crystals recovered four times higher than the amount of R-co-crystals present in the final product. The existence of R-IBU/BPE indicates that the primary nucleation of the undesired enantiomer still took place. This can be minimized by performing the experiment at bigger scale, where samples of the mother liquor can be taken during the process in order to monitor the evolution of the enantiomeric excess enabling the defining of an optimum filtration time. The crystallization of racemic IBU along with the cocrystals lowered the purity of S-IBU. By using new ratios of IBU/BPE close to the stoichiometric co-crystal ratio and with IBU in excess, this impurity can be diminished. Additionally a comprehensive study of the Metastable Zone Width (MSZW) in a bigger volume and the exploration of mixture of solvents can improve the definition of the final temperature in order to avoid the presence of racemic IBU and R-co-crystals in the crystals produced.Mechanical, Maritime and Materials EngineeringProcess and Energ
A Modelling Tool for Dynamic Simulation of Solution Crystallization Processes
No full textThe design of current industrial crystallizers is strongly focused on optimisation of known types of crystallization equipment. To get a better control over the physical events governing crystalline product quality the TU Delft started with the development of a task based design (TBD) strategy, which is an example of a phenomena based approach. Task-based design uses physical phenomena to construct tasks, which are used as building blocks for design. In this research, a modelling tool for dynamic simulation of task based solution crystallization processes is developed. This is an important step towards the long term aim of model-based optimisation driven process synthesis. The developed TBD model can be applied to a wide range of crystallization processes: various crystallization methods, operation modes, configurations and a variety in number of streams, compartments and crystallization tasks. The modelling structure is based on compartmental modelling. A new way to connect tasks to this compartment model is developed. This framework supports rapid generation of consistent process models and facilitates analysis of the influence of individual tasks. The model is implemented in gPROMS. To show the ability to quickly construct networks of units representing all kinds of crystallization processes, three different cases are simulated with the new model. Already existing innovative task based equipment from the TU Delft is also implemented, such as an airlift crystallizer, a membrane unit for solvent removal and an ultrasound vessel for the creation of primary nuclei. The first case simulates batch cooling crystallization experiments of ammonium sulphate in an airlift crystallizer with tasks Growth and Seeding and a cooling curve. The results are in agreement with experimental values. Case 2 shows the effect of individual tasks on a batch adipic acid crystallization system using a membrane unit for solvent removal. To demonstrate the future potential of TBD, in the third case a crystallization process is modelled which is never experimentally tested: continuous crystallization of adipic acid in a cascade of airlift crystallizers. Influence of the crystallizers in series on the CSD width is investigated. As expected, more larger crystals with a narrower CSD are produced in the cascade of airlifts. The results show that the developed structure works well. Using the task-function framework, newly developed tasks can be easily added, such that innovative Process Intensifications can be included in the model. The developed TBD model offers potential for model based process design of innovative task based crystallizers.Intensified Reaction & Separation SystemsProcess and EnergyMechanical, Maritime and Materials Engineerin
Ultrasonic irradiation and its mixing and nucleation consequences
No full textThis project aim to determine the macro streaming, the heat input and crystal nucleation induced by ultrasonic irradiation of a vessel containing solutions at different power input and irradiation time. First, experimental determination of the mixing induced by the ultrasound irradiation at different power input was studied using a high speed, high resolution camera. The particle image velocimetry (PIV) technique was used for these studies. The experiments showed that when increasing the power of the ultrasound processor, the velocity increased subsequently. Also, when power was increased, vorticity was increased. After, the heat input given by the sonotrode was studied using high speed camera and liquid crystals which change the color with temperature. The particle image thermometry (PIT) method was used to determined 2D temperature profiles. From the 2D temperature measurement 2D supersaturation profiles was determined. Experiments showed that when temperature increases, supersaturation decreases. The distribution of supersaturation and temperature were assessed at the same moment. Lastly crystal nucleation was performed at power inputs of 50% and 75% and different insonation time from 30 to 120 seconds. The solution used in these experiments was lactose. It was found that when power input increases, the amount of lactose crystals formed was also increasing. With higher power input and increased insonation time, the number of the crystals increased as well as the mean diameters. However there were exception. Above a certain level of insonation time the volume based diameter did not correspondently grow.Intensified Reaction & Separation SystemsProcess and EnergyMechanical, Maritime and Materials Engineerin
Dynamic modeling and validation of an industrial adipic acid plant
No full textAn industrial crystallization process is a complex process consisting of a lot of physical phenomena. Temperature, stirrer speed and other process inputs determine the rate of physical phenomena like agglomeration and growth. This study aims to develop a dynamic model structure that describes the physical phenomena in the crystallization process. The population balance equation is the basis of the model structure. Simple kinetic relations and the concentration balance are coupled to the population balance. The high resolution finite volume scheme is applied as the numerical solution method to solve the population balance equation. The dynamic model is validated with experimental results from an adipic acid crystallizer. Gathering the experimental results is a large part of this study. The process inputs of the crystallizer are changed to see the effect on the crystal size distribution (CSD). A change in the temperature seems to have the largest influence on the CSD. But the recirculation rate is the most effective process input to vary. The experimental results were used to validate the model structure. The model results shows that the model can simulate the measured mean crystal size accurately. Improvements on the kinetic relations have to be made to also simulate the complete CSD.PEQProcess and EnergyMechanical, Maritime and Materials Engineerin
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