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    Identifikation des mechanischen Verhaltens und Kopplung mit verbesserter interner Strukturanalyse von gefrorenen Partikel-Fluid-Systemen
    Gefrorene Partikel-Fluid -Systeme (PFS) können als partikelverstärkte Verbundwerkstoffe betrachtet werden und sind sowohl in natürlichen als auch in technischen Systemen häufig vorkommend. Wenn sie bei niedrigen Temperaturen mechanischer Belastung ausgesetzt werden, erfolgt für das Fluid, wenn es sich um Wasser handelt, innerhalb der PFS ein Phasenübergang, der zu Veränderungen ihres mechanischen Verhaltens und ihrer sonstigen damit verbundenen Eigenschaften führt. So ist beispielsweise in der Arktis die Bodenstabilität für Bauvorhaben entscheidend, und künstliches Bodenfrieren (AGF) wird häufig eingesetzt, um den Boden bei Bergbau- und Tunnelbauprojekten zu stabilisieren. Ebenso sind Materialien, die bei niedrigen Temperaturen in Silos gelagert werden oder einer kryogenen Mahlung unterzogen werden, Veränderungen in ihren mechanischen Eigenschaften ausgesetzt. Daher ist die Untersuchung von gefrorenen PFS mittels in-situ Methoden wichtig, um ihre charakteristischen Eigenschaften und ihr Verhalten unter realen Bedingungen zu verstehen. Derzeit werden verschiedene Ansätze zur Simulation von gefrorenen PFS verwendet, einschließlich Finite-Elemente-Methode (FEM)-Simulationen und Diskrete-Elemente-Modell (DEM)-Simulationen mit einem alternierenden Kontaktmodell. Diese Ansätze haben jedoch Einschränkungen, wie höherer Rechenaufwand, Probleme bei der Diskretisierung und die Unfähigkeit, das Verhalten komplexer Materialien präzise zu beschreiben. Um diese Einschränkungen aufzuheben, schlägt dieses Projekt die Verwendung eines neuartigen Bonded-Particle-Models (BPM) vor, das die DEM erweitert, indem Partikel mit Brücken verbunden werden, wodurch sich Agglomerate bilden. Es berücksichtigt das Kriechverhalten, um die Mechanik von gefrorenen PFS in Bezug auf unterschiedliche Temperaturen, Dehnungsraten und volumetrische Eisgehalte zu beschreiben. Um die interne Struktur der gefrorenen PFS in Abhängigkeit unterschiedlicher volumetrischer Eisgehalte und Partikel zu generieren werden zudem Mikro-Computertomographie (Mikro-CT)-Messungen durchgeführt, die eine zerstörungsfreie dreidimensionale Bildgebung der inneren Partikelstruktur mit einer hohen räumlichen Auflösung der Schnittbilder mittels Röntgenstrahlung nutzt. Es soll eine miniaturisierte uniaxiale Drucktest-Apparatur entwickelt werden, um den Gefrierprozess mit gekoppelter mechanischer Belastung in Zeitraffer mittels in-situ Mikro-CT-Gerät direkt zu erfassen. Es sollen Künstliche Neuronale Netze (KNN) verwendet werden, um die DEM-BPM-Materialparameter zu kalibrieren und die mechanischen Eigenschaften der Agglomerate während des Frierens und Belastens in Größenordnungen schneller vorauszuberechnen. Dafür wird zuvor eine Datenbank erstellt, die aus Tausenden von Simulationen besteht und erweitert wird, um weitere Szenarien und realistische Experimentaldaten zu korrelieren, was die Fähigkeit dieses Vorhersagewerkzeugs noch weiter ausbauen wird.
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    Investigation of Chemical Looping Combustion with a novel two stage fuel reactor for reduction of CO2 emissions
    Compared to conventional thermal power plant processes, Chemical Looping Combustion (CLC) enables an inherent CO2 capture without the need for costly separation of N2 and CO2. At the Institute of Solids Process Engineering and Particle Technology at Hamburg University of Technology, a 25 kWth pilot-scale CLC reactor with two combustion reactor stages is being operated. The second reactor stage enables higher conversion of volatile fuel gases. Experience has been gained with the combustion of methane and coal. Recently conducted first experiments with wood as fuel showed very high conversion rates. In the future, negative CO2 emissions, which are unavoidable for reaching the world’s 1.5 °C climate targets, should be achieved by using biomasses as a fuel. The aim of this project is to investigate wood particles, sewage sludge, agricultural waste and torrefied biomass as fuel in the two-stage 25 kWth CLC system. Due to the different compositions of the fuels, a detailed investigation of the different reaction mechanisms and optimization of the operating conditions of the pilot plant will be performed. Process dynamics such as start-up and shut-down as well as load changes will be investigated. Furthermore, a new reactor concept will be developed: The fuel reactor stages will be replaced by a spouted bed with an annular gas inlet to achieve lower pressure losses, which are essential for future scale ups. The experimental investigations will also be used to validate and extend a model in the open-source flowsheet simulation environment DYSSOL (Dynamic Simulation of SOLids Processes), which can then be used in the future to design and optimize new plant configurations. DYSSOL was developed in the DFG priority program (SPP1697) with a total of 27 subprojects across Germany and published in 2020. The focus of this work is on the formulation of enthalpy balances as well as an interface to connect DYSSOL and a software for CFD multiphase particle-in-cell method simulation. At last, a flowsheet simulation of an entire hypothetical 100 MWth industrial scale bio-CLC plant will be performed. Here for a first time, the whole process with the hydrodynamics and the chemical reactions including gasification and devolatilization of biomass particles will be included into one simulation. Pilot-scale biomass experiments and industrial-scale numerical simulations are essential for the development and design of future larger scale facilities. This work will evaluate if CLC is a potential candidate for future use for bioenergy with carbon capture and storage.
      78
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    Magnetic resonance imaging and numerical modelling of hydrodynamics in vibrated bubbling fluidized beds
    Fluidized beds are widely applied in several industrial fields, such as chemical engineering, energy conversion, and pharmaceuticals production. Vibrated bubbling fluidized beds are typically used in the food industry for drying of powders due to the resulting enhanced particle movement. Despite their widespread use, our fundamental physical understanding of the hydrodynamics occurring within fluidized beds is still limited and based on empirical or semi-empirical relations, that are valid only within narrow parameter ranges, making the scale-up of the apparatus design unreliable and expensive. Typical analysis methods are either intrusive and thus interfering with the process or based on 2D data. In recent years, non-intrusive tomographic techniques are increasingly used to study fluidized beds. Magnetic resonance imaging (MRI), a technique that has been mainly applied in the medical field, is particularly suited for obtaining spatially and temporally resolved dynamic information from the interior of fluidized beds. Besides experimental investigations, numerical modelling of fluidized beds has become more and more important during the last years due to increased computational power.The main aim of this project is to combine expertise in fluidized bed technology and novel simulation approaches with innovative real-time magnetic resonance imaging. An MRI system granted by DFG as part of a major instrumentation application (INST 153/152-1 FUGG) is currently being installed at TUHH. The MRI system will feature a vertical bore orientation of a diameter similar to those of clinical systems and a magnetic field strength of 3 Tesla. The system will employ powerful magnetic field gradients and radiofrequency hardware allowing high spatial and temporal resolution. Fluidized beds with and without vibration and different particle types will be investigated to get a detailed and thorough understanding of the effect of particle properties and fluidization parameters on the 3D hydrodynamics. The 3D MRI data obtained in this project are compared with frequently used correlations and with the results of intrusive probe measurements and image data obtained in pseudo-2D apparatuses. In addition to these experimental investigations, computational fluid dynamics simulations coupled with the discrete element model (CFD-DEM) will be performed. The MRI data are again used to test and validate these numerical models and benchmark their prediction accuracy of fluidization hydrodynamics. A specific focus here will be on the validation of frequently used models for drag forces and turbulence as well as coarse graining approaches. The vibration will be modelled by moving geometry and mesh. The real-time MRI data of vibrated and non-vibrated fluidized beds will allow us to validate the accuracy of existing correlations or develop new and more accurate correlations with the unparalleled detail in spatial and temporal resolution in the novel MRI system at TUHH.
      91
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    Development of an intelligent Digital Twin for prediction and control of the process behavior via transient flowsheet simulation using the example of fluidized bed spray granulation
    The process monitoring and control of production plants comes along with the ongoing demand for new developments to avoid unwanted process states and sub-specification production charges even though the processes in the field of particle technology have been used in industry for many decades. The main aim of this transfer project is increasing the efficiency of processes from chemical engineering by the development of an intelligent Digital Twin. This will be demonstrated using the example of the fluidized bed spray granulation process. The Digital Twin reproduces the state of the physical plant and predicts its future behavior, enable reliable control of the process. The intelligence of the Digital Twin is defined by the underlying models, which will be obtained by comprehensive data acquisition with continuous offline and online analysis methods. The high attention to detail of the models result in decision recommendations available faster the real-time, which allows predictions as well as process optimization steps. This is developed as a process-specific knowledge module that calls a flowsheet module, calibrates and consolidates the data. The results of the simulations are interpreted by soft sensors. A communication gateway will be developed that is responsible for the interaction between the simulation results and the digital process picture. The fluidized bed spray granulation model will be developed by experiments with a lab-scale plant at Hamburg University of Technology by application of statistical design of experiments. Unwanted process conditions will be deliberately adjusted in order to define the borders of stable process operation. The resulting model is implemented in the flowsheet simulation software Dyssol which has been developed during the DFG predecessor project (SPP 1679). By applying this software tool, the development procedure of the Digital Twin can be easily transferred to other processes and process chains of solids process engineering with minimal effort.Based on the future process states derived by the simulations, recommendations for actions will be implemented into the process control system of the plant. An optimization algorithm determines those parameters that result in a stable operation. The implementation into the process control system is conducted at the industrial partner, the company Pergande Group. Besides the operation of lab-scale plants, the transferability to larger plants will be demonstrated. The extension of current assistant systems will result in a competitive advantage for the distribution of new plants and is a unique feature in the field of fluidized bed technology for the industrial partner. In addition, it is assumed that the efficiency in the field of contract manufacturing can be increased by about 15 % due to a higher availability of the plants.
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    Dynamic flowsheet simulation system for solid phase processes
    Within the project “Central project: Dynamic simulation of interconnected processes” of the DFG priority programme “SPP 1679: Dynamic simulation of interconnected solids processes” a new dynamic flowsheet simulation system for solid phase processes has been developed. The designed modelling framework, named Dyssol, is able to simulate transient behaviour of complex process structures in the area of solids process engineering. It applies waveform relaxation method, supplemented by convergence and extrapolation methods for rapid dynamic calculations. The used approach with transformation matrices allows proper calculation of multidimensional interdependent distributed parameters of the solid phase. Due to its features, the Dyssol system is not limited to a certain scope, but is generally applicable for a variety of dynamic and steady-state processes. Although the modelling system is validated and fully functional in the scope of the SPP 1679, it was designed as research software, counting upon the close interaction of developers with end users. Therefore, Dyssol is not fully adapted for sustainable use as a free, publicly available, open source application.The main objective of the project presented in this proposal is to provide the community with a unique open source system for dynamic flowsheet simulation of granular materials, which can be used for research and education in a wide range of areas of solids process engineering. To achieve this goal, it is planned to solve such tasks as: design a suitable user interface to simplify interaction with the system; extend the library of models with new operations to make the framework more attractive and useful for a wide range of researchers and engineers; provide easier and more flexible ways to expand the system with new models; improve system performance; provide stability, maintainability and extensibility of program code; develop comprehensive documentation for all aspects of the system; organize easy public access to the source code, binary packages and documentation.
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    Monitoring and control of continuous multi-compartment fluidized bed spray granulation: Real-time predictions and flow-topology based process actuation
    Even though the fluidized bed spray granulation has been applied for more than 60 years, it is still a challenge to control the product particle size. The aim of our project is the development of a real-time monitoring and prediction framework, which enables the control of the product particle size distribution in continuous multi-compartment fluidized bed granulation processes. This objective will be achieved by three innovative pillars: novel switching-topology for fluidized bed operation, real-time simulations allowing for online process control and on online particle size measurement setup. Central part of the experimental investigations will be a two-stage lab-scale fluidized bed equipped with an underflow weir. We propose to use the phenomenon of segregation to influence which particles enter the spray zone and thus increase in particle size. By switching from homogeneous aeration to heterogeneous aeration, the topology of the particle circulation pattern will be changed. In homogeneous aeration mode, only larger particles are handed over to the consecutive stage by an underflow weir while smaller particles remain in the top-spray zone. The injection of a higher velocity gas stream (heterogeneous aeration) will cause circulation within the fluidized bed and thus homogenize the particle size distribution. Large particles will grow further just the same as smaller particles. As a novel measurement concept, we intend to assess the particle-size-distribution while particles pass the underflow gate between individual stages. To this end, the underflow weir gate is equipped with a mirror and an imaging system. By taking periodic snap-shots we will receive images of a set of particles on their flight through the gate. Online digital image analysis will provide instantaneous PSDs. The control of the spray granulation process will be performed by real-time simulations of fluidized bed dynamics by the recurrence CFD (rCFD) approach. rCFD uses recurrence plots of short-time CFD-DEM simulations (recurrence database) to time-extrapolate the fast dynamics based on the assumption that similar states will have a similar near-time evolution. Using this method, the internal state of the system can be simulated faster than real-time, which is not possible with pure CFD-DEM simulations. In this project, this radically new methodology will be further developed for poly-disperse systems. For this purpose we have to track and modify local particle size distributions. The fluidized bed control system will be integrated with the rCFD solver to synchronize the system state with choice of the database. This includes communication of outlet air temperature and humidity, as well as particle size distribution determined from the gate measurement setup and an interface for the control of the switching mechanism. Thus, the predictions from the rCFD solver will be used to choose the correct flow topology to yield the desired product particle size distribution.
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    Training in Upscaling particle Systems: Advancing Industry across Length-scales
    Ensuring particle models reflect system behaviour on industrial scales Particulate matter is ubiquitous – from grains of sand on the beach and aerosols in our environment to powders in pharmaceutical pills and raw materials for industrial processes. Numerical models are fundamental to enhancing our understanding of the behaviours of such matter. However, there is always a trade-off: retaining enough detail as the model is scaled up from particle to system so that accuracy is maintained versus simplifying so that computation does not become intractable without adding value to the outcome. The EU-funded TUSAIL project is training a new generation of researchers to develop and apply novel methodologies of upscaling that ensure a scaled model retains the information necessary to capture system behaviour. Outcomes will be invaluable to numerous industries, significantly enhancing EU competitiveness and human capacity.
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    Lab-scale fluidized bed system
    Particle formulation in fluidized beds includes the micro processes agglomeration, granulation and coating and is applied for the production of a lot of different products from chemical, pharmaceutical and food industry. The main aim is the production of particulate products out of the liquid phase by spraying liquid droplets (from solutions, suspensions or melts) into the fluidized bed. By directed adjustment of the process parameters granular, free-flowing, dust-free, stable and high-value particles with defined product and application properties can be produced.The Institute of Solids Process Engineering and Particle Technology has a long-term experience in the application and multi-scale simulation of fluidized beds for particle formulation by agglomeration, granulation and coating as well as for thermal treatment of particulate materials and for drying. Nevertheless, the experimental research area is limited as the existing lab-scale fluidized bed does not include a dust-explosion protection system, an inlet air dehumidification or a washing-in-place possibility. The requested lab-scale fluidized bed will overcome these limitations and will allow the investigation of additional material systems.The plant will be used in research projects focused on coating of highly-porous aerogel particles, generation of particles with high energy dissipation density as well as production of composite materials and additional functional particles. In addition, the general applicability of the fluidized bed spray granulation process for further material systems will be investigated. These systems include dusty powders, which can often be found in pharmaceutical and food industry. The size enlargement or coating or these powders presents an interesting research area in times of increased ecological awareness as the stability of the powders themselves can be increased by particle formulation while the amount of packaging material can be reduced. A major research focus of the institute is the investigation of the connection between process and apparatus specific parameters and the resulting product and application properties. The interaction of these pillars will be investigated for different material systems in order to improve the predictability of fluidized bed processes in industry and academia. In this context, a strong link to the multiscale simulation approaches will be created in order to calibrate the simulations and to create process kinetics for flowsheet simulations, respectively. Another research focus will be the development of scaling laws. By installation of a plant with two process chambers with same geometry but different size, the influence of the plant size can be quantified and novel scaling approaches will be developed.
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