Dense Solid-Liquid Suspensions in Top-Covered Unbaffled Stirred Vessels

In the present work solids suspension is investigated in an unbaffled tank stirred by a Rushton turbine and provided with a top-cover in order to avoid the formation of the well known central vortex. The data obtained are compared with those pertaining baffled stirred tanks via comparison with the well known Zwietering’s correlation. The dependence of Njs on particle concentration is found to be similar to that well established for baffled vessels, while, as a difference from the latter, Njs is found to decrease when liquid viscosity increases. Results also show that Njs is substantially independent of particle size, a feature that may advice the adoption of unbaffled tanks when large heavy…

PLANT FOR WASTE DISPOSAL AND ASSOCIATED METHOD

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…

Measurements of Njs and Power Requirements in Unbaffled Bioslurry Reactors

The remediation of urban/industrial polluted lands is a topic of crucial importance nowadays. Bioremediation techniques are widely employed to remove organic pollutants from contaminated soils because of their simplicity and cheapness. The bioslurry reactors mechanically agitated by stirrers represent one of the most promising bioremediation techniques. In the present work an unbaffled stirred vessel filled with solids and water is experimentally investigated from a fluid dynamic point of view. Air presence within the tank is guaranteed by the central vortex formation (typical occurrence concerning stirred vessels unprovided with baffles) instead of an intrinsically more expensive insufflat…

Power requirements for complete suspension and aeration in an unbaffled bioslurry reactor

Remediation of contaminated soils is spreading as a matter of crucial importance nowadays. Bioremediation via bioslurry reactors of sites polluted by recalcitrant pollutants has been proved to be a valuable option, although optimization is needed to reduce process costs. Free-surface unbaffled stirred tanks (with central air vortex) have been recently proposed as a promising alternative to the more common systems provided with baffles. In a bioslurry reactor solid-liquid interfacial area, oxygen supply, solid loading per reactor unit volume should be maximized, and, at the same time, operation costs have to be kept low. In this regard, the minimum impeller speeds for complete suspension Njs…

Magnesium recovery from concentrated brines

Growing microalgae in a “quasi-isoactinic” photobioreactor

The aim of this work is setting up the conditions of an “iso-actinic” photobioreactor that is a photoreactor for the cultivation of microalgae in which the local volumetric rate of photon absorption (LVRPA), can be considered uniform to a good extent. We describe the composition of this cheap photoreactor and how we made it. The system is driven by an Arduino platform that makes it possible to control light intensity as well as light-dark cycles. Preliminary results obtained by growing Nannochloropsis gaditana, a microalga famous for its fat content, in this innovative reactor are presented. We finally observed how microalgae responds to flashing light irradiation.

Mortality rate and risk factors for gastrointestinal bleeding in elderly patients

Abstract Background Gastrointestinal bleeding (GIB) is burdened by high mortality rate that increases with aging. Elderly patients may be exposed to multiple risk factors for GIB. We aimed at defining the impact of GIB in elderly patients. Methods Since 2008, samples of elderly patients (age ≥ 65 years) with multimorbidity admitted to 101 internal medicine wards across Italy have been prospectively enrolled and followed-up (REPOSI registry). Diagnoses of GIB, length of stay (LOS), mortality rate, and possible risk factors, including drugs, index of comorbidity (Cumulative Illness Rating Scale [CIRS]), polypharmacy, and chronic diseases were assessed. Adjusted multivariate logistic regressio…

Prophylaxis of venous thromboembolism in elderly patients with multimorbidity

none 327 si Pharmacological thromboprophylaxis (TP) is known to reduce venous thromboembolism (VTE) in medical inpatients, but the criteria for risk-driven prescription, safety and impact on mortality are still debated. We analyze data on elderly patients with multimorbidities admitted in the year 2010 to the Italian internal medicine wards participating in the REPOSI registry to investigate the rate of TP during the hospital stay, and analyze the factors that are related to its prescription. Multivariate logistic regression, area under the ROC curve and CART analysis were performed to look for independent predictors of TP prescription. Association between TP and VTE, bleeding and death in …

Dense Solid-Liquid Off-Bottom Suspension Dynamics: Simulation and Experiment

Dense solid-liquid off-bottom suspension inside a baffled mechanically agitated stirred tank equipped with a standard Rushton turbine is investigated. Dynamic evolution of the suspension from start up to steady state conditions has been inspected by both visual experiments and computational fluid dynamics. A classical Eulerian-Eulerian Multi Fluid Model along with the “homogeneous” k-epsilon turbulence model is adopted to simulate suspension dynamics. In these systems the drag inter-phase force affects both solids suspension and distribution. Therefore, different computational approaches are tested in order to compute this term. Simulation results are compared with images acquired on the re…

Apparatus for synthesizing and separating synthesis products e.g. gaseous and liquid phases on bed, maintains heavier liquid phase at lower portion of first meatus due to gravity and lighter liquid phase at upper portion of meatus

NOVELTY - The apparatus has header that is set to make the heavier and lighter liquid phases flow along outer side surface of a third tube (8) as far as first closure element (13). The third tube is provided with second side openings for directly connecting the first and second meatus. The heavier liquid phase is maintained at lower portion of the first meatus due to gravity and lighter liquid phase is maintained at upper portion of the first meatus until the liquid phases fall into a fourth tube (9). The heavier liquid phase is collectible through a collection hole (12). USE - Apparatus e.g. reactor/separator for synthesizing and separating synthesis products e.g. gaseous phase and heavier…

Need for Deprescribing in Hospital Elderly Patients Discharged with a Limited Life Expectancy: The REPOSI Study

<b><i>Objective:</i></b> Older people approaching the end of life are at a high risk for adverse drug reactions. Approaching the end of life should change the therapeutic aims, triggering a reduction in the number of drugs.<b><i></i></b>The main aim of this study is to describe the preventive and symptomatic drug treatments prescribed to patients discharged with a limited life expectancy from internal medicine and geriatric wards. The secondary aim was to describe the potentially severe drug-drug interactions (DDI). <b><i>Materials and Methods:</i></b> We analyzed Registry of Polytherapies Societa Italiana di Medicina I…

ON THE MEASUREMENT OF MASS TRANSFER COEFFICIENT KLA IN GAS-LIQUID CONTACTORS VIA OXYGEN CONCENTRATION DYNAMICS

Residence Time Distribution of Solid Particles in a High-Aspect Ratio Multiple-Impeller Stirred Vessel

Despite its importance, experimental information on the Residence Time Distribution (RTD) of solid particles in continuous-flow stirred vessels is still scant. In this work, experimental data on particle RTD in a high-aspect-ratio vessel stirred by three equally-spaced Rushton turbines, was obtained by means of a special technique named Twin System Approach (TSA). Quite surprisingly, results indicate that, among the various possibilities that could have been devised (e.g. 6, or 3, or 1 ideal tanks in series), the flow model closest to reality for the particle phase, at least in the experimental range here investigated, is that of a single perfectly stirred vessel.

Valorization of waste solvents through supercritical water gasification

The supercritical water gasification of various organic species belonging to the groups of organic acids, aldehydes, ketones, alcohols and phenols, has been studied as a possible waste disposal method for polluted water stream produced in industries and laboratories. Gasification has been investigated using a 200 cm3 down flow reactor working continuously at 24 MPa and 660 °C. Supercritical water gasification (SCWG) is effective for the syngas production at very high conversion rate for all the species investigates, but phenol. Phenol, when mixed with other species, has an inhibitory effect of the radical chain gasification mechanism that dramatically reduced the gasification performance. …

High temperature solid-catalized transesterification for biodiesel production

Biodiesel has become more attractive recently because of its environmental benefits and the fact that it is made from renewable resources. Biodiesel is a mixture of monoalkyl esters of long chain fatty acids derived from renewable feed stock like vegetable oils and animal fats, mainly made of fatty acid glycerides. It is produced by transesterification processes in which oil or fat are reacted with a monohydric alcohol in the presence of a catalyst. The transesterification process is affected by reaction conditions, alcohol to oil molar ratio, type of alcohol, type and amount of catalysts, temperature and purity of reactants. Heterogeneous acid catalysts are quite efficient in promoting the…

Free vortex shape in Uncovered Unbaffled Stirred Tanks (UUST) agitated by Rushton turbines

The main feature of unbaffled stirred tanks is the highly swirling liquid motion, which leads to the formation of a central vortex on the liquid free surface, when the vessel is operated without top-cover (Uncovered Unbaffled Stirred Tanks, UUST). In this work, original data on fluid dynamics characteristics of (UUST) agitated by a Rushton turbine are presented. In particular, digital image analysis is employed to accurately assess vortex shape and validate an original model for its description. The model describes vortex shape in the case of sub-critical systems (when vortex bottom is placed above the impeller plane) as well as in the case of super-critical systems (when vortex bottom fall…

CFD Simulation of Dense Cloud Dispersion in Urban Areas

A national multicentre study on severe paediatric recurrent idiopathic pericarditis treated with IL-1 blockers: appropriateness of the standard of care and pros and cons of anti-IL-1 treatments

Recurrent pericarditis (RP) is a rare cause of morbidity in children. Non-steroidal anti-inflammatory drugs (NSAIDs), glucocorticoids and colchicine are the standard of care in adults. Recently, anakinra has been proven to be effective in patients with steroid-dependence and colchicine resistance.

Proceedings of the 12th European Conference on Mixing