Modeling Mercury Capture by Powdered Activated Carbon in a Fluidized Bed Reactor

A steady state model of mercury capture on activated carbon in a bubbling fluidized bed of inert material is presented. The model takes into account the fluidized bed fluid-dynamics, the presence of both free and adhered carbon in the reactor as well as mass transfer limitations and mercury adsorption equilibrium. The activated carbon adsorption parameters and the relative amount of free versus adhered carbon in the reactor have been estimated with purposely designed experiments. Model results are compared with results from mercury capture experiments conducted with commercial powdered activated carbon at 100°C in a lab-scale pyrex fluidized bed of inert particles. The role of free versus adhered carbon in determining the overall mercury capture efficiency is discussed

Local anaesthesia efficacy as postoperative analgesia for open shoulder instability surgery. a prospective randomised controlled study

Background and objectives: The aim of present study was to evaluate for the first time, the clinical effect of local anaesthetic infiltration as postoperative analgesia in open shoulder surgery for anterior-inferior instability. The comparison of the local infiltration and interscalenic brachial plexus block to a control group test the local anaesthetic efficacy in this surgery. Methods: 78 patients scheduled for open shoulder surgery were enrolled and randomly assigned to one of three groups: local infiltration anaesthesia (LIA), interscalenic brachial plexus block (IBPB) and control (C). All patients received standardized general anaesthesia and all injections were performed with the same dose and volume of anaesthetic. The number boluses delivered by a PCA pump applied at the end of surgery and the visual analogue score (VAS) at 0, 2, 4, 6, 12, 18 and 24 hours after intervention were recorded. A patient satisfaction score was also assessed. Results: Mean bolus consumption of the rescue analgesic, compared to C, was significantly less both in the LIA and IBPB groups (P<0.05). The IBPB group showed VAS scores that were significantly better than C group at all time points (P<0.05). The VAS scores for LIA group were clinically comparable to IBPB, and only at the 2 and 6 hours, postoperative time points there were no significant differences found in respect to the C group. IBPB and LIA showed comparable patient satisfaction scores. Conclusion: The local anaesthetic infiltration as postoperative analgesia appears to be a clinically valid alternative, statistically comparable to IBPB, with no clinical meaningful adverse effects

Active and capable fault? The case study of Prata D'Ansidonia (L'Aquila, Central Apennine)

The study deals with the morphogenetic meaning of several linear scarps that carved the paleo-landsurface of Valle Daria, an extended geomorphological feature located between Barisciano (AQ) and Prata D'Ansidonia (AQ). These villages are situated in the southern termination of the L'Aquila intermontane basin (one of the largest basin of the central Apennines), nearby the epicentral area of the 6th April 2009 earthquake (Mw 6.1). These scarps, up to 3 meters high and up to 1.5 km long, define narrow/elongated flat-bottom depressions, filled by colluvial deposits. These depressions are carved into fluvial-deltaical conglomerates, dated back to the lower Pleistocene. Even if different authors have interpreted these shapes as a paleodrainage or secondary faults, a morphometrical study of the Valle Daria paleo-landsurface provided several information which cast doubt on these two interpretations. In order to better understand the nature and the state of activity of these lineaments, geological, geomorphological and geophysical surveys were carried out. A paleoseismological trench pointed out two events of deformation. The curvilinear shape of the shear plane seems to be related to a slow deformation, attributable to collapse-phenomena. Three GPR profiles, two ERT profiles and two microgravimetrical profiles seem to corroborate this interpretation. Therefore, this study permits to attribute the genesis of these scarps to tectono-karstic phenomena, excluding the presence of an active and capable fault.Published346-3494T. Sismologia, geofisica e geologia per l'ingegneria sismicaN/A or not JC

Modeling flue gas desulfurization by spray-dry absorption

A detailed model for flue gas desulfurization by spray-dry absorption with a lime slurry is presented. The model combines a steady state one-dimensional spray-dryer model with a single-drop model for SO2 absorption with instantaneous irreversible reaction in a rigid droplet containing uniformly dispersed fine lime particles. The fate of the droplets is followed from atomization until formation of a porous coherent shell around the drying droplets. The model results were validated against available experimental spray-dry FGD results, showing excellent agreement at low to medium Ca/S feed ratios. The model was then used to study the relevance of the different resistances to SO2 absorption and to predict the influence of the main operating variables on the spray-dryer desulfurization performance. Analysis of variables profiles along the spray-dry column showed that the initial droplet velocity has no influence on model results and that the initial droplets decelerating phase always accounts for negligible SO2 capture. Results further showed that the controlling resistance to SO2 absorption shifts from a liquid-phase one near the atomizer to a gas-phase one at the column exit. The operating variables that exert the largest influence on the overall desulfurization efficiency are the Ca/S molar feed ratio, the mean initial droplet size and the mean lime particle size. In particular, careful control of the last two variables is critical in order to obtain a good spray-dryer performance. (C) 2003 Elsevier B.V. All rights reserved