1,721,076 research outputs found
Introduzione alla Sicurezza degli Incidenti Rilevanti
No full textQuesto volume si pone l’obiettivo di affrontare in modo introduttivo ma
completo il tema della sicurezza industriale, relativamente agli incidenti rilevanti.
Partendo da una disamina sulla valutazione del rischio, il testo approfondisce le tecniche di identificazione dei pericoli e degli scenari incidentali (incluse HazOp ed AOR) ed il calcolo della frequenza di accadimento (albero dei guasti), per poi passare a metodologie di stima della magnitudo per dispersioni, incendi ed esplosioni.
Nella seconda parte, il volume si sofferma sull’analisi dell’attuale normativa di riferimento, identificando gli adempimenti in capo alle aziende e ponendosi come un aiuto nella fase di stesura della documentazione richiesta dalla legge per le imprese a rischio di incidente rilevante.
Il volume è destinato agli studenti dei corsi di laurea in Ingegneria della
Sicurezza, ma vuole porsi anche come utile guida per chi, nel mondo industriale, si trova a ricoprire il ruolo di addetto alla sicurezza nelle industrie di processo
Safe intensification of potentially runaway reactions: From semibatch to continuous processes
No full textFast and highly exothermic reactions are commonly carried out in semibatch reactors (SBRs) in order to better control the heat evolution by the feeding rate. In fact, for such processes, a phenomenon known as "thermal runaway", that is an uncontrolled reactor temperature increase, may be triggered whenever the rate of heat removal becomes lower than the rate of heat release. This dangerous temperature increase, occurring in practically adiabatic conditions, can trigger secondary undesired exothermic reactions or, in some cases, the decomposition of the whole reacting mixture with consequent reactor pressurization and, eventually, explosion followed by the release of high amounts of hazardous products. As a consequence, several studies on the detection of the so called "runaway boundaries" have been performed during years. However, from a practical perspective, the desired goal of whatever enterprise is to attain the maximum productivity maintaining safe conditions. Such a goal can be achieved using a series of continuous stirred tank reactors (CSTRs) operated in the isothermal temperature control mode; but a possible change of the reactor type, from discontinuous (e.g. batch or SB) to continuous (series of CSTRs), with the aim of increasing the productivity cannot be performed so easily when a potentially runaway process is involved. The main aim of this work has been to compute the number of CSTRs in a series that, guaranteeing the requested productivity and reactants conversion under safe operating conditions (runaway phenomena cannot be triggered), minimizes the volume of each reactor of the series. Such a number results to be a function of the employed kinetic scheme and the dosing policy of the co-reactants. In this work, two different dosing policies (1-co-reactant dosed into the first reactor of the series; 2) co-reactant dosed into the first NR-1 reactors of the series) will be analyzed for the relevant case study of the synthesis of N-(4-nitro, 2-phenoxyphenyl) methane sulphonamide. The obtained results have shown that it is possible to increase the overall productivity of the process, simply shifting from discontinuous to continuous operating mode, also achieving a safe intensification, that is, having lower reacting volumes at the full plant
Study of the performance of disinfection with sodium hypochlorite on a full-scale sewage treatment plant
Full text linkA full-scale sewage treatment plant was investigated to assess the performance of the disinfection stage. Sodium hypochlorite was used as a disinfectant agent and the process efficiency was evaluated by E.coli removal. The research took place over a period of two years in order to evaluate the effect of retention time (t) and residual chlorine (Cr) under different seasonal conditions. The effectiveness of E.coli removal with sodium hypochlorite proved to be strictly dependent on the factor CR t (product of residual chlorine with the contact time). The regression line of the experimental points was, on the whole, well comparable with the model proposed by Collins, especially in the field of CRt lower than 30 mg L-1 min
Batchsize e criteri topologici: un approccio combinato per l'ottimizzazione in sicurezza
No full textLe piccole e medie imprese chimiche sono una tipologia di industria ampiamente diffusa in Italia. In particolare, esse operano i loro processi in modalità batch e semi-batch, lavorando spesso su commessa e facendo un uso massiccio di reattori multifunzione aventi un sistema di sfogo delle sovrappressioni già installato. Un approccio di tipo “batchsize” è un metodo focalizzato sulla ricerca del livello massimo di riempimento di un reattore multipurpose tale da portare ad un efflusso monofase vapore in caso si verifichi un incendio esterno (in tal modo il dispositivo installato può proteggere il reattore da eventuali sovrappressioni).
In questo lavoro, tale approccio è stato completamente rivisitato, scegliendo come peggior scenario incidentale il caso di reazione fuggitiva, ed integrato con un’opportuna procedura di ottimizzazione basata su criteri di tipo topologico.
Il nuovo approccio “batchsize” permette di calcolare un livello di riempimento del reattore molto più ragionevole per applicazioni industriali rispetto a quello previsto dal metodo classico, mentre l’approccio topologico permette di identificare il tempo di dosaggio minimo in grado di garantire sia la sicurezza dei reattori sia un’elevata produttività. I risultati teorici di questo studio sono stati convalidati sperimentalmente mediante dati ottenuti da test di calorimetria di reazione, condotti in un reattore RC1 operante in modalità isoperibolica, utilizzando come caso studio la polimerizzazione in soluzione dell’acrilato di butile.Small and medium chemical enterprises are widely diffused in Italy. Particularly, they operate batch and semi-batch processes working on job orders and making a massive use of multipurpose reactors having an Emergency Relief System (ERS) already installed. A batchsize approach is a method focused on finding the reactor fill level that can lead to a single phase vapor flow whether an external fire occurs, so that the installed ERS can protect the reactor from overpressures. In this work, such an approach has been revised, by choosing a runaway reaction as design incidental scenario, and integrated with a suitable optimization procedure based on topological criteria. The new batchsize approach allows for computing a reactor
fill level which is much more reasonable for industrial applications with respect to that one predicted by the older method, while the topological approach permits to identify the minimum dosing time capable of guaranteeing both reactor safety and high productivity. Theoretical results have been experimentally validated using data obtained by reaction calorimetry experiments, carried out in an isoperibolic RC1 equipment, implementing the relevant case study of the solution homopolymerization of butyl acrylate
Behavioral Safety: A way to decrease injuries at work (with science)
No full textWork-related injuries are a well known problem all around European Union (EU): every year, at
least 170000 workers die and even more suffer severe and permanent injuries.
Even if EU placed the goal of reducing this number by 25% by 2012, in many countries the situation remains
unchanged despite the enforcement of increasingly stringent laws that, anyways, elude the most important
question: why?
Moreover, in spite of a lot of American and European studies demonstrated that at least 76% of work-related
accidents are due to workers unsafe behaviors, blaming workers is not a effective solution because it eludes
again the question: why a worker should act unsafe?
An answer to this last question comes from studies about human behavior: a person acts a certain way
because he is subject to a number of external stimuli, before and after his act. So, if a person receives a
positive consequence as a reward for his behavior, he continues to output the same behavior.
Till 80's, Behavior-Based Safety (B-BS) uses this mechanic to provide positive consequences to safe
behaviors, instead of negative ones, increasing safety and reducing injuries.
But does B-BS work? Even if a lot of literature case studies of successful B-BS implementation are present,
all across the world, there is a lack of scientific experiments to unequivocally state that B-BS increases safe
behaviors and reduces injuries. This work provides two different case studies, using not only a before-after
analysis but also using an appropriate mathematical test (Young’s C Test), to examine workers’ behavior
changes during time.
The work puts in competition two different B-BS protocols, which share all the fundamentals but differ for
start-up time and cost, applied on two different Italian industrial sites: a glass bottle factory and a paint
factory.
These protocols obtains the same results, demonstrating not only that B-BS works, but also that behavioral
safety can be achieved at low cost even for small European industries
Application of a decision support system to the transport of hazardous materials
No full textThe transport of hazardous substances is an essential economic activity because it represents a quite relevant percentage of the total goods transportation. The risk associated to such an activity is fundamentally related to the possibility of an accident triggering that may cause negative environmental and public health consequences. A recent example is the Viareggio accident (2009), which involved the blast of tank wagons containing liquefied petroleum gas (LPG) and caused more than thirty deaths. In this paper, a modified algorithm for risk evaluation and a decision support system, called TrHaM (TRansport of HAzardous Materials), are proposed in order to both quantify the overall risk due to the transport of hazardous materials via road, railroad,
waterway and pipeline and help in planning transport activities. The algorithm evaluates and shows the risk distribution using a stand-alone GIS software, which also considers sensitive targets with high crowding (such as schools, hospitals, shopping malls, stadiums and camping areas). Moreover, it allows for finding the transport solution and its logistics which minimize risk distribution, including intermodal shipping.
TrHaM reliability has been tested onto the circulation of hazardous materials in the Varese district (Northern Italy). The area is characterized by a high level of both population and industrial density combined with heavy road traffic. TrHaM has been used with the aim of comparing the current scenario with a potential one that introduces some mitigating interventions which may reduce risk, such as a partial conversion of haulage from road to railway
Estimation of the deflagration index KSt for dust explosions: A review
No full textCombustible dust explosions are among the most serious criticalities affecting a broad number of industries around the world. According to a Chemical Safety and Hazard Investigation Board report, more than 50 accidents have occurred only in the U.S. between 2008 and 2012; this datum shows that such a problem requires a relevant attention from both researchers and authorities. The aim of this review is to provide an overview of the currently available techniques able to estimate the severity of a combustible dust explosion. Moreover, the main criticalities arising from these methodologies are discussed, also providing some suggestions for future works
Experimental design of topological curves to safely optimize highly exothermic complex reacting systems
No full textStrongly exothermic solution homopolymerizations are a class of chain reactions particularly difficult to be optimized from both a safety and a productivity viewpoint. Particularly, lots of side undesired reactions (e.g., backbiting, propagation of tertiary radicals, chain transfer to monomer or solvent, etc.), which affect the selectivity with respect to the desired product, and relevant mass and heat transfer problems, due to the increasing system viscosity, take place during such syntheses. Under these unavoidable operating conditions, it is difficult to employ theoretical procedures that are able to safely optimize the analyzed process, because the development of a reliable mathematical model is often not affordable or too time-consuming. In this work, it is shown that the topological criterion theory and its related optimization procedure can be used to optimize experimentally (through a dedicated set of isoperibolic reaction calorimetry tests) a complex reacting system even if its reaction scheme and all information about the kinetics are not available
Topological criteria to safely optimize hazardous chemical processes involving consecutive reactions
No full textSafe operating conditions, for strongly exothermic chemical systems involving multiple reactions, are particularly critical to be obtained, because of the complex interactions between selectivity and safety constraints. In this work, new criteria, which are useful for isoperibolic semibatch processes involving consecutive reactions and based on the topology of a particular phase space, are presented. Such criteria are able to detect both the runaway boundary and the so-called “quick onset, fair conversion, smooth temperature profile” (QFS) operating region by performing a topological analysis of the phase space of the system of ordinary differential equations (ODEs) that describe the analyzed process. Moreover, a safe optimization procedure, the objective of which is to obtain the optimum values both of the dosing time of the dosed reactant and the initial reactor temperature, based on such criteria, has been developed. Finally, such a set of optimum operating parameters has been validated through a comparison with experimental data from published literature
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