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showing 10 items of 453 documents
CFD prediction of solid particle distribution in baffled stirred vessels under partial to complete suspension conditions
2013
Solid-liquid mixing within tanks agitated by stirrers can be easily encountered in many industrial processes. It is common to find an industrial tank operating at an impeller speed N lower than the minimum agitation speed for the suspension of solid particles: under such conditions the distribution of solid-particles is very far from being homogeneous and very significant concentration gradients exist. The present work evaluates the capability of a Computational Fluid Dynamics (CFD) model to reliably predict the particle distribution throughout the tank under either partial or complete suspension conditions. A flat bottomed baffled tank stirred by a Rushton turbine was investigated. Both tr…
Comparison of Agitators Performance for Particle Suspension in Top-Covered Unbaffled Vessels
2015
Power savings is a problem of crucial importance nowadays. In process industry, suspension of solid particles into liquids is usually obtained by employing stirred tanks, which often are very power demanding. Notwithstanding tanks provided with baffles are traditionally adopted for this task, recent studies have shown that power reductions can be obtained in top-covered unbaffled vessels. In the present work experiments were carried out in a top-covered unbaffled vessel with a diameter T=0.19m and filled with distilled water and silica particles. Two different turbines were tested: a standard six-bladed Rushton Turbine (RT) and a 45° four bladed Pitched Blade Turbine (PBT). For the case of …
Oxygen Transfer Performances of Unbaffled Bio_Reactors with Various Aspect Ratios
2014
Cultivation of microorganisms, plants or animal cells requires liquid agitation in order to ensure oxygen and nutrient transfer and to maintain cell suspension. Many studies on animal cell damage due to mechanical agitation and sparging aeration have shown that mechanical damage of freely suspended animal cells is in most cases associated with bursting bubbles at the air–liquid interface (Barrett et al., 2010). Gas bubbles are usually generated by direct air sparging aimed at supplying oxygen to the culture medium. Mechanical agitation may also introduce gas bubbles in the culture medium via vortexing entrainment from the free surface. In this work oxygen transfer performance of an unbaffle…
Stability analysis of type-2 fuzzy logic controllers
2009
The application of the direct Lyapunov method to the stability analysis of systems controlled by type-2 fuzzy logic controllers (FLC) is presented. The method is an extension of a method proposed for type-1 fuzzy systems. It is usually applied to systems described by state equations and controlled by fuzzy controllers using state variables as inputs but has been extended to controllers that have the error and the integral of error of the controlled variable as inputs. The proposed method allows to modify the controller rule base so that the controlled system is stable in the operating range defined by the manipulative variable constraints. The method is applied to the stability analysis of …
Experimental Analysis via Thermochromic Liquid Crystals of the Temperature Local Distribution in Membrane Distillation Modules
2013
A reliable and optimized design of channels for Membrane Distillation (MD) requires knowledge of local temperature distributions within the module. This information is essential to measure the temperature polarization, choice the module configuration (net spacer features, channel size, etc) providing the best process performance. Notwithstanding such crucial aspects, only few studies have been devoted to the experimental characterization of MD channels and none of them includes data on the local temperature distribution. In the present work, an experimental technique based on the use of Thermochromic Liquid Crystals (TLCs) and digital image processing, previously proposed by the authors (Pi…
Electrochemical Processes and Apparatuses for the Abatement of Acid Orange 7 in Water
2014
We have studied the electrochemical treatment of aqu eous solutions contaminated by Acid Orange 7 (AO7) by electro-Fenton process (EF). The main object ive was to evaluate how the electrochemical route affects the performances of the d egradation process. EF process was carried out in a number of very different reactors: conventional bench scale electrochem ical cell, microfluidic electrochemical reactor, microbial fuel cell and stack for reverse electrodialysis processes. The utilisation of micro devices allowed to work without the addition of a supporting elec trolyte and improved the performances of EF. Microbial fuel cell did not need the supply of electric energy bu t our device requir…
Magnesium Hydroxide Nanoparticles Production from Natural Bitterns
2022
Magnesium hydroxide nanoparticles are widely employed in numerous industrial applications. Several preparation methods have been proposed using mainly synthetic Mg2+ containing solutions. In the present work, the possibility of producing Mg(OH)2 nanoparticles from real bitterns, the by-product of sea salt production, is investigated. Bitterns are highly concentrated Mg2+ containing solutions whose exploitation can turn a waste into valuable products embracing the circular economy idea. Two bitterns collected from Galia and Margi saltworks of the district of Trapani (Italy) were studied. Galia and Margi bitterns had a 1 M and 2.5 M Mg2+ concentration, respectively. A 2 mm diameter circular-c…
A process model of electrodialysis including membrane deformation effects
2020
Electrodialysis (ED) is an electro-driven process that makes use of ion exchange membranes (IEMs) under an applied electric field. The main application of ED is the desalination for drinking water production. A transmembrane pressure (TMP) distribution may arise in ED stacks due to an uneven pressure distribution in the two fluid channels, thus causing membrane/channel deformation and flow redistribution. This can occur in large-scale non-parallel configurations, e.g. crossflow arrangements. Detrimental effects of membrane deformation have widely been studied with reference to several membrane processes. However, this aspect has been neglected in ED applications. In this work, a novel proce…
Electromembrane Processes: Experiments and Modelling
2021
The increasing demand for water and energy poses technological challenges to the implementation of efficient concepts for a sustainable development. In this perspective, electromembrane processes (EMPs) can play a crucial role in green chemistry schemes oriented towards circular economy approaches and renewable energy systems. EMPs are based on the use of ion-exchange membranes under the action of an electric field. Versatility, selectivity, high recovery, and chemical-free operations are their main strengths. Experimental campaigns and modelling tools are prompting the improvement of consolidated processes and the development of novel concepts. Several application fields have been proposed…
Lagrangian simulation of bubbling dynamics in a lab-scale 2D fluidized bed
2013
The present work focuses on the development of a novel computational code able to predict with a reasonable level of accuracy the bubble behavior in gas fluidized beds with minimum computational demands. The code simulates the bubble chaotic rise motion and coalescence along bed height via simple lagrangian tracking of bubbles. An original empirical model for the assessment of bubble-bubble interactions is developed. The code is used to simulate a lab-scale unit in bubbling and slugging mode. On this basis, fast simulations are performed to successfully predict bubble population and fluxes within the bed. The main aim of this code is to be embedded within CAPE codes for the process simulati…