Search results for "impianti chimici"
showing 10 items of 190 documents
CFD simulation of gas-liquid stirred vessels
2006
Computational Fluid Dynamics is an increasingly important tool for carrying out realistic simulations of process apparatuses. As a difference from single phase systems, for multipliase systcms the development of CFD models is still at its early stages. In the present work CFD simulations of gasliquid stirred tanks are reported. All bubbles are assumed to share the same size, and a simplified approach is adopted for the description of momentum exchanges between tile two phases. In particular ir is shown that the only parameter needed for modeling drag forces is bubble terminal velocity. Results show that in a quite wide range encompassing most practical applications, bubble size has a limite…
CFD simulation of gas-liquid hydrodynamics in a rectangular air–lift loop reactor
2006
Computational Fluid Dynamics is an increasingly important tool for carrying out realistic simulations of process apparatuses. As a difference from single phase systems, for multi phase systems the development of CFD models is still at its early stages. Moreover, gas-liquid systems are characterised by an additional complexity level, related to the fact that, as a difference with solid-liquid systems, bubble sizes are not known in advance, being rather the result of formation and breakage-coalescence dynamics, and therefore of complex phenomena related to flow dynamics and interfacial effects. In the present work CFD simulations of gas-liquid air-lift reactors are reported. All bubbles are a…
Local gas-liquid hold-up and interfacial area via light sheet and image analysis
2010
Particle Image Velocimetry techniques coupled with advanced Image Processing tools are receiving an increasing interest for measuring flow quantities and local bubble-size distributions in gas-liquid contactors. In this work, an effective experimental technique for measuring local gas hold-up and interfacial area, as well as bubble size distribution, is discussed. The technique, hereafter referred to as Laser Induced Fluorescence with Shadow Analysis for Bubble Sizing (LIF-SABS) is based on laser sheet illumination of the gas-liquid dispersion and synchronized camera, i.e. on equipment typically available within PIV set-ups. The liquid phase is made fluorescent by a suitable dye, and an opt…
Measurement techniques and modelling of multiphase systems.
2011
Multiphase systems are often encountered in process industry. Widely diffused applications and operations involve the contact between different phases (gas-solid, gasliquid, solid liquid, etc.) for different purposes, such as chemical reactions of physical operations (heat transfer, mass transfer). Multiphase flows are therefore one of the most frequent applied fields in chemical engineering. The present thesis is aimed at the development of experimental techniques for the investigation of multiphase flow in general, with particular focus on the analysis of gas-solid and gas-liquid systems. Notably, the development of image analysis techniques is the central thread of the present contributi…
MODELLING OF THE GROWTH OF NANNOCHLOROPSIS GADITANA IN DIFFERENT REACTOR GEOMETRIES, EXPERIMENTAL KINETIC PARAMETERS FROM BATCH CULTURES AND BIOCHEMI…
2022
Microalgae are unicellular and photosynthetic microorganisms that grow using inorganic salts, CO2 and light, and are applied in numerous industrial sectors due to their variety and properties. Due to the lack of information on how microalgae respond to external inputs and to the different environments in which they grow, today the industrial application is not exploited as it should. It is therefore necessary to create models that allow to predict microalgal growth in different photobioreactors to improve our knowledge, still poorly investigated. In this work the Monod equation for the specific growth rate was combined with the Lambert-Beer law for the non-homogeneous light distribution in …
MIXING TIME IN UNBAFFLED STIRRED TANKS
2012
Unbaffled stirred tanks, despite their poorer mixing performance with respect to baffled vessels, are gaining a growing industrial interest as they provide significant advantages in selected applications, including a number of biochemical, food and pharmaceutical processes. There still is however a general lack of information on their mixing performance, that needs to be addressed in order to fully exploit their application potential. The present work is aimed at providing experimental information on mixing rates in an unbaffled vessel operated without top-cover (Uncovered Unbaffled Stirred Tank, UUST). The planar laser induced fluorescence (PLIF) technique was adopted for measuring the dis…
PLANT FOR WASTE DISPOSAL AND ASSOCIATED METHOD
2016
Described herein is a plant for the disposal of wastes including: a supercritical water oxidation reactor (SCWO), a supercritical water gassification reactor (SCWG), a feeding system configured for feeding at least two organic currents of wastes to said SCWO and SCWG and configured for feeding at least one aqueous flow within said plant, wherein said feeding system is configured for feeding said at least one aqueous current with a series flow throw said SCWO and SCWG and wherein said feeding system is furthermore configured for feeding said at least two organic currents of wastes with a parallel flow through said SCWO and SCWG and so as to selectively feed each of said organic currents of w…
Apparato di sintesi su letto catalitico e separazione di fasi liquido-gas
2011
Apparato di sintesi su letto catalitico e di separazione dei prodotti di sintesi comprendenti una fase gassosa e due fasi liquide, una fase liquida più pesante e l’altra fase liquida più leggera, l’apparato comprendente - un modulo di sintesi (M1) comprendente un primo tubo (1) provvisto ad una prima estremità di un’apertura e chiuso ad una seconda estremità da una griglia (7), il primo tubo (1) essendo atto a contenere al suo interno un letto catalitico (6); - ed un modulo di separazione (M2) per separare le due fasi liquide e la fase gassosa provenienti dal modulo di sintesi (M1), comprendente un secondo tubo (1’) disposto adiacente alla seconda estremità del primo tubo (1), comunicante c…
Civil Wastewater Remediation through Employment of Indigenous Microalgae and Sewage Sludge
2022
Microalgae are photosynthetic microorganisms that can employ some inorganic pollutant compounds as nutrients, for example nitrates and phosphates. Traditional wastewater treatment comprises oxidation ponds in which the Activated Sludge performs the oxidation of the organic matter. Microalgae may be well applied in these processes. In this work, we tested the potential of remediation of a mixture of a local microalga, Chlorella sp. Pozzillo, and activated sludge and compared it to controls of only microalga and only activated sludge. We found that the mixture of bacteria and microalgae leads to an improvement in nitrogen removal up to the 83,68%, while phosphorous removal is improved when th…
A NOVEL TECHNIQUE FOR MEASURING LOCAL BUBBLE SIZE DISTRIBUTION
2009
A novel experimental technique for measuring the local gas hold-up and the statistical distribution of local bubble size, is proposed. The technique is based on laser sheet illumination of the gas-liquid dispersion and synchronized camera, i.e. on equipment typically available in PIV set-ups. The liquid phase is made fluorescent by a suitable dye, and a band-pass optical filter is placed in front of the camera optics, in order to allow only fluoresced light to reach the camera CCD. In this way bubbles intercepted by the laser sheet are clearly identified thanks to the neat shade resulting in the images. This allows excluding from subsequent analysis all bubbles visible in the images but not…