Experimental investigation on concentration profiles and fluctuations of dense gases in wind tunnel

One of the most frequent accident scenario following a loss of containment during HazMat transportation or processing is represented by the dispersion of a dense gas release. Several dispersion models are available to this purpose, more or less rigorously accounting for gravity slumping, air entrainment and possible heat transfer. Under confined geometry, the correct evaluation of possible concentration fluctuations represent an up-to-date research topic, both considering the process sector and a peculiar application represented by operating theaters for surgery. In this last context, the use of heavier than air gas is usually performed for anaesthetic application, while few validation data are available on the dispersion behavior following a fugitive emission and exposure of persons inside the enclosure. On these bases, the experimental phase of this paper was performed in a laboratory-scale wind tunnel of circular section, under different Reynolds number regimes, considering a continuous release scenario of two tracer gases, namely carbon dioxide and sulphur hexafluoride, at different low release rates. A detailed study on concentration fluctuations and time series is presented yielding reliable information on the influence of the different source types and flow rates. Conclusions are drawn on practical feasibility and application of the experimental results, in view of safe optimization of the design and mode of operation of ventilation systems in the considered settings

Operational parameter influence on heavy metal removal from metal plating wastewater by electrocoagulation process

Among the different treatment processes available for industrial wastewater treatment, electrocoagulation represents a challenging option due to several features, such as environmental compatibility, inherent safety, energy and cost effectiveness. The effectiveness of electrocoagulation process (ECP) using aluminium and iron electrodes for the removal of heavy metals from industrial wastewater has been investigated, with particular attention to the effects of operating parameters (pH, inter-electrode distance, hydraulic retention time and current density) on removal efficiency. In the first step of the experimental phase, a laboratory-made artificial wastewater containing heavy metals (Cu, Ni and Pb) was adopted in order to identify the optimum conditions that were subsequently applied to treat a metal plating industrial wastewater. Experimental results revealed that under the optimal experimental conditions (actual pH 6.32, current density 0.026 A cm-2), the removal efficiency of heavy metals from artificial wastewater was higher than 95 %

Generalisation of the solution of the inverse Richards' problem

In inverse problems defined by models that include partial differential equations, a part of the boundary conditions are unknown and are to be estimated from experimental measurements. We have shown in a previous contribution that the solution of the inverse Richards' problem can allow estimating percolation rates at the bottom of landfills through the use of measurements at the surface only. This can be a useful complement of the information furnished by the vadose measurement system, pointing to the possible presence of biases of in-situ equipment, and making it possible to use inexpensive mobile equipment to carry out surface measurements. In this article, we consider a generalisation which makes it possible to consider the presence of unknown nonlinear parameters, such as the effective hydraulic conductivity and the root uptake coefficients. This is accomplished using the method of separation of variables in the resulting estimation problem. Thanks to the linearity of the model, all these conditions can be expressed as linear functions of the unknown lower boundary condition. Otherwise, the relevant non-linear parameters are to be estimated from the data as well. Obviously, the correlation between the linear parameters contained in the unknown lower boundary conditions and the non-linear parameters can reduce the reliability of the monitoring procedure and hence the necessity of limiting the number of the latter

Nano risk evaluation in laboratory environment by a customized layer of protection analysis approach

Nanotechnologies are widely used in various industrial settings and by the year 2020, it is expected that nearly 20 % of all products manufactured in the world will take a certain amount of nanotechnology. However, there is a substantial imbalance of knowledge between application of nanotechnology and its impact on health and environment, also considering that nanoparticle synthesis by chemical methods assumed a key role for economic, industrial and scale-up issues. The information currently available on nanomaterial risk assessment within the workplace are limited: systematic methods for assessing exposure are not known yet and the number of workers exposed is hardly estimated. This knowledge gap imposes to the scientific community the need to join efforts to provide a shared opinion on safety, health and welfare of workers who use, manipulate, or produce nanomaterials, adopting as well preventive and protective measures proportionated to the risk according to the precautionary principle. We develop a novel framework for Nano Risk Assessment within the laboratory context, by combining LOPA and HazId techniques, assigning credit factors to specific operative procedures and safety training, suitable to mitigate risk exposure and avoid over-conservative evaluations. Conclusions are drawn on applicative results and possible direction for further implementation of the approach, in view of sustainable, healthy and safe production at research and industrial level

Ageing and creeping management in major accident plants according to seveso III directive

The focus of this paper is the management of critical equipment ageing within the context of lower and upper tier Seveso process plants, with a peculiar insight into the effectiveness of safety management systems in setting-up reliable procedure for critical element identification. Recent research studies in fact evidenced that in Europe nearly 50% of major 'loss of containment' events, arising from technical plant failures, were primarily due to ageing plant mechanisms such as erosion, corrosion and fatigue. The critical ageing elements should be included in maintenance, inspection and periodic monitoring programs in relation to their reliability, as assumed in the risk assessment and their lifetime or frequency ranges, based on their operational experience. This paper will accurately discuss how the issue of ageing is currently handled in the process industry. The methodology builds on the critical results of actual findings from the inspections on the safety management systems of major accident plants, which were performed by a working group. The primary objective is to stimulate the introduction of effective ageing management changes into the safety management of companies, by taking advantages of findings of the previous assessment and establishing proper and effective audits

A Novel Graphite-Based Sorbent for Oil Spill Cleanup

The performance of an innovative material based on expanded graphite, Grafysorber\uae G+ (Directa Plus), has been tested through laboratory, tank, and confinement tests for oil removal in case of an oil spill and water treatment. In addition to the ability to retain oil, the possibility of reusing this material after regeneration via squeezing was also evaluated. As a comparison, the same experimental tests were conducted using polypropylene flakes (PP), the material currently most used to deal with spill accidents. Oils with different chemical and physical properties were used, namely kerosene, diesel, and crude oil. From the laboratory tests, the capacity of Grafysorber\uae G+ to retain oil was found to be directly proportional to the viscosity of the latter, with adsorption values ranging from 76.8 g/g for diesel to 50.8 g/g for kerosene, confirming the potential of the innovative material compared to the PP. Cyclical use tests have confirmed certain reusability of the material, even if its adsorbent capacity decreases significantly after the first cycle and continues to decrease in subsequent cycles, but a less marked manner. Finally, some considerations based on the adsorption capacities were found to suggest that the adoption of the new material is also economically preferable, resulting in savings of 20 to 40% per kg of hydrocarbon treated

Cobalt-based nanoparticles synthesis in organic solvents with environmentally sound processes

A process for the synthesis of cobalt-based nanoparticles is proposed, where standard reducing agent like hydrazine, alkali metal borohydrides, hypophosphites or other toxic reducing agents have not been employed. The solvothermal reaction is carried out in organic solvents and the dimension of the nanoparticles thus obtained have been analyzed by dynamic light scattering. Cobalt nitrate proved to be an efficient precursor, in agreement with previous literature works where its suitability for analogous processes has been tested and compared with the efficiency typical of other precursors routinely used. The soundness of this method, in terms of process safety, has been checked by analyzing the formation of toxic by-products that could be formed by side-reactions between the precursor and the solvent. This work may add some more details to a discussion pertaining to the accidental formation of N-nitroso derivatives of aliphatic compounds in the presence of alkanolamines and oxides of nitrogen

New trends in the synthesis of nanoparticles by green methods

In this brief survey, we deal with green processes concerning the synthesis of zerovalent nanoparticles, enlighting some aspects motivating their choice with respect to traditional techniques generally relying upon toxic or noxious reactants and stabilizing agents. After a short discussion about health and environmental safety related to the use of standard reductants, we run through several green methods for metal nanoparticle synthesis and we split them into two basic classes, according to the electropositivity of the elements which the nanoparticles are made of. This classification has been proposed in order to account for strengths and weaknesses of processes based on active substances of biological origin that, though being effective in the production of noble metal nanoparticles, proved to be much less suitable when tested in the synthesis of nanoparticles made of more electropositive elements. The goal of this work is essentially oriented to stimulating new research trends for the eco-friendly production of nanosized non-noble elements deserving more attention by current nanobiotechnology

ZnAl-SO4 Layered Double Hydroxide and Allophane for Cr(VI), Cu(II) and Fe(III) Adsorption in Wastewater: Structure Comparison and Synergistic Effects

Owing to their structure, layered double hydroxides (LDHs) and allophane are nowadays considered as promising materials for application in different fields. The goal of this work is to compare the efficacy of allophane and ZnAl-SO4 LDH to remove, by adsorption, some cationic and anionic pollutants from industrial wastewater. Both compounds were synthesized via the coprecipitation route (direct method) followed by hydrothermal treatment, obtaining nanoscopic crystallites with a partially disordered turbostratic (ZnAl-SO4 LDH) or amorphous (allophane) structure. The characterization of the obtained compounds was performed by means of powder xray diffraction (PXRD), thermal gravimetry analysis (TGA), field emission scanning electron microscopy analysis (FESEM), and Fourier-transform infrared spectroscopy (FT-IR). The sorbents were tested using wastewater produced by a real metalworking plant and containing ionic species such as Cu(II), Fe(III) and Cr(VI), whose concentration was measured by means of inductively coupled plasma-optical emission spectrometry (ICP-OES). This investigation represents an alternative procedure with respect to standard protocols based on customarily made and artificially lab-produced wastewaters. Both sorbents and their combination proved to be efficient in Cr(VI) removal, irrespective of the presence of cations like Cu(II) and Fe(III). A synergistic effect was detected for Cu(II) adsorption in a mixed allophane/LDH sorbent, leading to a Cu(II) removal rate of 89.5%