Benintendi R.,Megaris Ltd.
Education for Chemical Engineers | Year: 2016
Process safety has undergone a tremendous growth over the last decades, both in terms of required competencies and in terms of market demand. Although its cultural background mainly consists of the traditional subjects of chemical and process engineering, a multifaceted range of expertise has made it autonomous and different from the general chemical engineering frame: the interdisciplinary degree is much wider, the relevant regulations and standards have become so stringent and specific to become a key driver for the scientific and technical development of the discipline, its current growth trend is probably incomparable to others, role and functions of process safety engineers have acquired more significances and implications in the industrial scenario. This article considers the learning lessons of a long tutoring and teaching activity that the author has carried out in process safety between university and industry in Europe and in Asia. The findings have been analysed and converted into specific indicators and trend data, with the aim to contribute to reduce the significant gap which still exists in a branch of chemical engineering that is expected to increase its complexity and importance in the near future. © 2016 The Institution of Chemical Engineers.
Benintendi R.,Megaris Ltd
Journal of Loss Prevention in the Process Industries | Year: 2011
A previous article dealt with turbulent jet flow modelling with the aim at developing a method for estimating the size of explosive clouds following a high Reynolds number release, within hazardous area classification scheme. The results have demonstrated that the standard EN 60079-10 (2009) largely overestimates the real size of clouds resulting from a piping or a vessel leak. On the other hand, laminar jets are possible also at moderately high Reynolds numbers; furthermore, a reduced momentum, typical of laminar jets, is often assumed in QRA studies, as a conservative assumption, due to the expected lower air entrainment and to the corresponding larger size of the flammable cloud volume. These considerations have suggested the suitability to extend the previous analysis also to laminar regime, taking into account the effect of density and viscosity differences between air and flammable gas. © 2010 Elsevier Ltd.
Benintendi R.,Megaris Ltd
Journal of Loss Prevention in the Process Industries | Year: 2010
Hazardous area classification, as per EN 60079-10, is based on the explosive gas volume of the clouds in which the average gas concentration is related to the Low Explosion Limit (LEL). The higher Reynolds number, the less this approach is valid, because of the development of a concentration gradient due to the momentum driven flow. The resulting areas and volumes may be overestimated by two or three orders of magnitude, which is often critical in equipment design and selection. This paper proposes and technically justifies an overview of turbulent jet flow modelling, with the aim at developing a more realistic calculation method of the hazardous areas, within the ATEX approach. © 2009 Elsevier Ltd. All rights reserved.
Benintendi R.,Megaris Ltd
Process Safety and Environmental Protection | Year: 2015
This article deals with role and importance of adsorption in the activated sludge substrate degradation. This process is typically described according to the Monod-Michaelis-Menten (M-MM) kinetics, which is based on the assumption that the substrate has been pre-adsorbed on flocs in order for the biochemical reaction to take place. However, the simple and generalised use of M-MM equation in wastewater treatment modelling could be misleading in describing some specific scenarios, where substrate in the liquid phase is not in equilibrium with substrate inside the flocs and, in general, when adsorption and kinetic rates are not comparable. This can occur in numerous process configurations, during plant start-up, when substrate peaks or significant fluctuations are met, in batch processes. An experimental test has been carried out with the aim to investigate the characteristics of the adsorption mechanism and its relationship with the stored mass degradation. Direct application of M-MM kinetics failed in fitting the experimental data. External transport and Glueckauf and Coates particle-phase diffusion relations have been adopted to study substrate transfer to active sites. Andrews and Busby model has then been applied and an excellent accordance with the experimental data has been found. As a final aim of the work, transition from adsorption-to-kinetics has been modelled, which has shown to be very effective for a full understanding of phenomena. © 2015 The Institution of Chemical Engineers.
Benintendi R.,Amec Foster Wheeler |
Rega S.,Megaris Ltd.
Chemical Engineering Research and Design | Year: 2014
Rapid phase transition (RPT) is a phenomenon which frequently occurs after an LNG release on water. Its effects are potentially hazardous mainly because of the very fast rate of high energy release, in addition to fire and explosion. A significant case history and various experimental campaigns provide evidence which has allowed assessing different aspects of this event. This paper aims at offering a unified thermodynamic analysis of RPT. The thermodynamic and the kinetic limits of liquid superheat have been fully reviewed and specifically applied to LNG, within the homogeneous nucleation theory for multi-component liquids. Thermal and thermo-mechanical interface properties, such as interface temperature, evaporation rate, surface properties and liquid fragmentation have also been investigated. The importance of LNG composition has been analysed with respect to the experimental data. Finally, on the basis of the well known Shepherd and Sturtevart test, bubble growth rate has been modelled according to Mikic, Rohsenow and Griffith (MRG) equation and a new rigorous method has been set up to predict RPT overpressure, in line with Lighthill's acoustic theory, which removes the existing uncertainty and some subjectivities of the available models and possibly increases the thermo-fluid dynamic understanding of the phenomenon. © 2014 The Institution of Chemical Engineers.
Benintendi R.,Megaris Ltd
Journal of Loss Prevention in the Process Industries | Year: 2016
Release of liquids from vessels and pipelines is a very important scenario in consequence assessment. When the operating pressure is significant, its evolution and the corresponding discharge rate are affected by the elastic behaviour of the liquid. Bulk modulus is the key-driver of the related fluid-dynamics and is expected to govern the elastic-to-atmospheric pressure transition. Despite the well known physical background, the availability of release models relevant to the elastic phase is rather poor, compared to those relevant to vapours, gases and atmospheric liquids. On the other hand, if the operating pressure is high, release times and dynamics are expected to be strongly affected by the elastic behaviour and prediction of release time and flow rate is fundamental. This article carries outs a general analysis of the elastic behaviour of liquids, including water and hydrocarbons. Lumped (vessel-type) and distributed (pipeline) parameters systems have been modelled with the aim to characterize the pressure evolution during the elastic phase and to evaluate the significance of the associated duration. The findings have shown that, depending on pressure and geometric features, the importance of the elastic phase is high and that the availability of reliable and relatively simple models could be beneficial in consequence assessment. The approach is strictly valid for non-boiling liquid, but accounting for vaporisation of flashing or boiling liquids such as LPG and LNG would not imply significant complications. © 2016 Elsevier Ltd.