Interdiffusion along grain boundaries: Diffusion induced grain boundary migration, low temperature homogenization and reactions in nanostructured thin films

LBK

Pickering Emulsion and Derived Materials

Particle-stabilized emulsions, today often referred to as Pickering/Ramsden emulsions, are vital in many fields, including personal care products, foods, pharmaceuticals, and oil recovery. The exploitation of these Pickering emulsions for the manufacture of new functional materials has also recently become the subject of intense investigation. While much progress has been made over the past decade, Pickering emulsion still remains a rich topic since many aspects of their behavior have yet to be investigated. The present “Pickering Emulsion and Derived Materials” Special Issue aims to bring together research and review papers pertaining to the recent developments in the design, fabrication, and application of Pickering emulsions. The themes include, but are not limited to: 1. Interactions of colloidal particles confined at fluid interfaces 2. Pickering emulsion-based polymerization 3. Interfacial assembly and emulsion stabilization 4. Rheology of particle laden interfaces and Pickering emulsions 5. Functional materials templated from Pickering emulsion

Investigation of the CO2 carbonation reaction: kinetic models, CFD simulations and thermogravimetric data analysis

This work of thesis deals with the kinetics of the CO2 carbonation reaction. A Random Pore Model (RPM) is chosen to simulate the kinetics of the carbonation. The results of this model are then compared with TGA data. Afterwards, the intra-particle diffusion is considered. Finally, a fuid-dynamic study on an horizontal TGA is presented using a CFD commercial cod

Denitrification of recirculated aquaculture system effluents using fish sludge as primary substrate

Recirculating Aquaculture System (RAS) is a technology in which water is reused after different biological and mechanical treatment steps in fish farming. RAS produces a nitrate rich water effluent containing approximately 70-100 mg NO3/l, and a typical plant will have to offload between 50-100 kg NO3-N/d which needs to be denitrified before release to the marine environment to avoid eutrophication. Denitrification is a heterogenic process whereby reduced substrates (primarily organic, but also some reduced inorganic salts, like H2S and Fe2+, may serve as electron donors) are oxidized anoxically by reduction of NO3 and NO2 to N2. Organic substrates may come from external sources (easily biodegradable substrateslike acetate or methanol) or from internal, like the collected fish waste sludge containing feces and feed pellet residuals. Fish waste sludge is mainly particulate slowly biodegradable, and hydrolysis is necessary for use as C-source for denitrification. Fish sludge has been considered waste in the fish farming industries. Therefore, it is free, and applying it to run RAS is a resource recovery process. The kinetics (reaction rate) of denitrification using fish sludge is dependent on the chemical oxygen demand (COD) level; slowly biodegradable CODs (sbCODs) should be converted to readily biodegradable CODs (rbCODs) to provide the nitrate uptake process. Raw fish sludge was step-fed once or twice a day to a batch reactor containing substrate adapted activated sludge loaded with an initial nitrate concentration of 360 mg/l. Fish sludge characterization wet analysis was done on three different sludge batches and were compared. Two fermentation tests at 12 and 20 ℃ were done on fish sludge to investigate the effect of fermentation on biodegradability of fish sludge. Biomass specific nitrate uptake rates (NUR) were measured by an ion selective electrode, and substrate degradability and was estimated. NUR was also estimated using an equivalent initial COD concentration of acetate, and maximum NUR rates using fish sludge and fermented fish sludge were evaluated relative to the acetate driven denitrification rate. Fish sludge COD were split into three biodegradable fractions (easily biodegradable, slowly biodegradable, and slowly biodegradable particulate) based on NUR profiles, and their corresponding COD estimated using typical denitrifying yield factors. The observed acetate specific denitrification rate was 3.64 mg NO3-N/g VSS. h while the fish sludge rates were estimated to 1.2, 0.9 and 0.2 mg NO3-N/g VSS. h for the easily, slowly, and particulate degradable COD fractions respectively. Additionally, the effect of fermentation during anaerobic storages (over seven days) on sludge characteristics and volatile fatty acid production was investigated and the specific denitrification rate of settled and supernatant fermented sludge for easily degradable CODs was 3 and 2.2 mg NO3-N/g VSS. h. We conclude that direct use of fish sludge for denitrification of RAS effluents is possible, but design and operation would have to allow for the relative slow kinetics of the process, hypothetically limited by hydrolysis of slowly biodegradable dissolved and particulate COD fractions, which could be accelerated through fermentation

Large-scale dynamic hydrofracturing, healing and fracture network characterization

Permeability of a rock is a dynamic property that varies spatially and temporally. Fractures provide the most efficient channels for fluid flow and thus directly contribute to the permeability of the system. Fractures usually form as a result of a combination of tectonic stresses, gravity (i.e. lithostatic pressure) and fluid pressures. High pressure gradients alone can cause fracturing, the process which is termed as hydrofracturing that can determine caprock (seal) stability or reservoir integrity. Fluids also transport mass and heat, and are responsible for the formation of veins by precipitating minerals within open fractures. Veining (healing) thus directly influences the rock’s permeability. Upon deformation these closed factures (veins) can refracture and the cycle starts again. This fracturing-healing-refacturing cycle is a fundamental part in studying the deformation dynamics and permeability evolution of rock systems. This is generally accompanied by fracture network characterization focusing on network topology that determines network connectivity. Fracture characterization allows to acquire quantitative and qualitative data on fractures and forms an important part of reservoir modeling. This thesis highlights the importance of fracture-healing and veins’ mechanical properties on the deformation dynamics. It shows that permeability varies spatially and temporally, and that healed systems (veined rocks) should not be treated as fractured systems (rocks without veins). Field observations also demonstrate the influence of contrasting mechanical properties, in addition to the complexities of vein microstructures that can form in low-porosity and permeability layered sequences. The thesis also presents graph theory as a characterization method to obtain statistical measures on evolving network connectivity. It also proposes what measures a good reservoir should have to exhibit potentially large permeability and robustness against healing. The results presented in the thesis can have applications for hydrocarbon and geothermal reservoir exploration, mining industry, underground waste disposal, CO2 injection or groundwater modeling

Mass Transfer in Multiphase Systems and its Applications

This book covers a number of developing topics in mass transfer processes in multiphase systems for a variety of applications. The book effectively blends theoretical, numerical, modeling and experimental aspects of mass transfer in multiphase systems that are usually encountered in many research areas such as chemical, reactor, environmental and petroleum engineering. From biological and chemical reactors to paper and wood industry and all the way to thin film, the 31 chapters of this book serve as an important reference for any researcher or engineer working in the field of mass transfer and related topics