Several methodologies, based on different thermodynamic assumptions and requiring substance properties and thermodynamic data, have been proposed in the literature for the prediction of the mechanical energy released by a Boiling Liquid Expanding Vapour Explosion (BLEVE) and the associated overpressure. A new method, simple and easy to use, is presented which only requires the vessel filling degree and the temperature at failure as input variables to estimate this energy. The polynomial approach has been used to obtain the equation corresponding to the diverse substances most commonly involved in these explosions. The comparison of the predicted values with experimental data shows a good agreement.
Hosseini Asl, S.; Masomi, M.; Hosseini, M.; Javadian, H.; Ruiz, M.; Sastre, A. Process safety and environmental protection Vol. 107, p. 153-167 DOI: 10.1016/j.psep.2017.02.012 Data de publicació: 2017-04-01 Article en revista
The aim of this research was to estimate the possibility of using synthesized hydrous iron oxide/aluminium hydroxide composite loaded on coal fly ash (FA3) as an efficient sorbent for Cr(VI) sorption from aqueous solution. In this regard, dissolution and precipitation processes were performed to rearrange and load the intrinsic iron and aluminum on the surface of fly ash. Different characterization techniques including XRD, XRF, FT-IR, SEM, LPS and BET surface area were applied to analyze the sorbent properties. Moreover, sorption kinetics were studied using Morris–Weber intra-particle diffusion, Lagergren pseudo-first-order and pseudo-second-order models. The kinetic analyses indicated that pseudo-first-order model controlled the sorption process. In order to estimate the sorbent capacity, Langmuir, Freundlich and D–R models were applied. The thermodynamic parameters of Cr(VI) sorption were also studied. In addition, removal efficiency of Cr(VI) was predicted using the developed fuzzy logic model. The fuzzification of four input variables including pH, contact time, adsorbent dose and initial Cr(VI) concentration versus removal efficiency as output was carried out using an artificial intelligence-based approach. A Mamdani-type fuzzy interface system was employed to fulfill a collection of 24 rules (If-Then format) using triangle membership functions (MFS) with seven levels in fuzzy sets. The proposed fuzzy logic model demonstrated high predictive performance with correlation coefficient (R2) of 0.95 and acceptable deviation from the experimental data, confirming its suitability to predict Cr(VI) removal efficiency. Based on experimental data and statistical analysis, the synthetized sorbent was effective for treating wastewater containing Cr(VI).
The mechanical effects of a BLEVE are overpressure and ejection of fragments. Although fragments reach much longer distances, peak overpressure can be very strong over a certain area. Diverse authors have proposed methodologies for the estimation of the explosion energy and peak overpressure from these type of explosions, based on different thermodynamic and physical assumptions. Here these methodologies are commented and compared. Their predictions, which show an important scattering, are checked by comparison with two sets of experimental data taken from the literature. The results obtained indicate that none of the models take into account Reid’s theory. The models based on ideal gas behaviour and constant volume energy addition, isentropic expansion and isothermal expansion give quite conservative (i.e., high) values of both energy released and overpressure, while those assuming real gas behaviour and adiabatic irreversible expansion give lower values, much closer to the real/experimental ones. The diverse uncertainty factors affecting the prediction of peak overpressure are also commented.
Bubbico, R.; Carbone, F.; Ramírez-Camacho, J. G.; Pastor, E.; Casal, J. Process safety and environmental protection Vol. 104, num. Part A, p. 95-110 DOI: 10.1016/j.psep.2016.08.011 Data de publicació: 2016-11-01 Article en revista
Pipelines are commonly considered a safe alternative for the transportation of hazardous materials. However, in case of failure, pipelines still pose major risks to the environment and to the population potentially exposed. The aim of the present work is to provide occurrence probabilities of the intermediate and final events following the accidental release of hazardous materials from pipelines. A collection of incidents and accidents occurred worldwide in connection with the use of onshore long-distance pipeline networks, has been gathered to make up a specific database for the analysis of incidents in pipelines. A qualitative and quantitative analysis of the data has allowed to develop detailed event trees for the different classes of hazardous materials, and to calculate the probability of occurrence of the final outcomes. The investigation has also aimed at identifying, for each type of release, the relationship between the final events and the causes of the pipeline failure. The results obtained represent a useful and needed starting point in Quantitative Risk Analysis of hazardous materials transportation via pipelines.
Several studies have demonstrated the presence of pollutants from the pharmaceuticalindustry in surface and groundwater. The main inputs of pollutants come from households,hospitals and the industry and many of these compounds are not completely removed by WWTPs. The purpose of this research is to study the adsorption of paracetamol, phenoland salicylic acid using coal-based activated carbons. A lignite from Mequinenza (M) andan anthracite from Coto Minero Narcea (CN) from Spain were chemically activated withalkaline agents obtaining two activated carbons (MAC and CNAC). Two commercial activated carbons widely used in water treatment (F400 and NPK) were selected for comparison purposes. The activated carbons were characterized and the results showed a high surface BET (1839 m2g-1) and total pore volume (0.83 cm3g-1) on CNAC while MAC was charac-terized by high sulphur content (6%). Vapour isotherms indicated a chemical interaction between the surface functional groups of MAC and the water molecules. The highest uptake of the three pharmaceutical compounds was achieved by CNAC. MAC showed a high affinity for anion salicylates (at pH 4–8). The maximum adsorption capacity of the pollutants onto the activated carbons followed the order salicylic acid > phenol > paracetamol which can be explained by hydrophobicity.
González Dan, J. R.; Guix, A.; Martí, V.; Arnaldos, J.; Darbra, R.M. Process safety and environmental protection Vol. 102, p. 441-449 DOI: 10.1016/j.psep.2016.04.024 Data de publicació: 2016-07 Article en revista
The frequency of occurrence of an accident is a key aspect in the risk assessment field. Vari- ables such as the human factor (HF), which is a major cause of undesired events in process industries, are usually not considered explicitly, mainly due to the uncertainty generated due to the lack of knowledge and the complexity associated to it. In this work, failure frequencies are modified through Monte Carlo (MC) simulation includ- ing the uncertainty generated by HF. MC is one of the most commonly approach used for uncertainty assessment based on probability distribution functions that represent all the variables included in the model. This technique has been also proved to be very useful in the risk assessment field. The model takes into account the uncertainty and variability generated by several HF variables. In order to test the model, it has been applied to two real case studies, obtaining new frequency values for the different scenarios. Together with the consequences assessment, new isorisk curves were plotted. Since the uncertainty generated by the HF has now been taken in to account through MC simulation, these new values are more realistic and accurate. As a result, an improvement of the final risk assessment is achieved.
The frequency of occurrence of an accident is a key aspects in the risk assessment field. Variables such as the human factor (HF), which is a major cause of undesired events in process industries, are usually not considered explicitly, mainly due to the uncertainty generated due to the lack of knowledge and the complexity associated to it.
In this work, failure frequencies are modified through Monte Carlo (MC) simulation including the uncertainty generated by HF. MC is one of the most commonly approach used for uncertainty assessment based on probability distribution functions that represent all the variables included in the model.
This technique has been also proved to be very useful in the risk assessment field. The model takes into account the uncertainty and variability generated by several HF variables.
In order to test the model, it has been applied to two real case studies, obtaining new frequency values for the different scenarios. Together with the consequences assessment, new isorisk curves were plotted. Since the uncertainty generated by the HF has now been taken in to account through MC simulation, these new values are more realistic and accurate. As a result, an improvement of the final risk assessment is achieved.
Llado, J.; Lao, C.; Ruiz, B.; Fuente, E.; Sole, M.; Dorado, A.D. Process safety and environmental protection Vol. 95, p. 51-59 DOI: 10.1016/j.psep.2015.02.013 Data de publicació: 2015-05-20 Article en revista
Adsorption of two widespread emerging water contaminants (atrazine and paracetamol) onto three different activated carbons was investigated. The carbons were characterized and the influence of their physicochemical properties on the adsorption performance of atrazine and paracetamol was evaluated. The adsorption equilibrium data were fitted to different adsorption isotherm models (Langmuir, Freundlich, and Dubinin-Radushkevich) while the adsorption rates were described using three different kinetic models (pseudo second order, intraparticle diffusion and a new approach based on diffusion-reaction models). The results indicated that hydrophobic character of the compounds does not affect the sorption capacity of the tested carbons but does influence the uptake rate. The model proposed, based on mass balances, lead to interpret and compare the kinetic of different adsorbents in contrast to classical empirical models. The model is a simple and powerful tool able to satisfactorily estimate the sorption capacities and kinetics of the carbons under different operation conditions by means of only two parameters with physical meaning. All the carbons studied adsorbed paracetamol more effectively than atrazine, possibly due to the fact that sorption takes place by H-bonding interactions.
The mine disaster of gas at working face and goaf creates a risky working environment for miners, and causes a mass of casualties in mining industry around the world. The key points of resolving the gas problem are to properly increase fresh air volume in ventilation network, exactly determining the gas emission zone, and implementing a reasonable gas drainage plan. This article provides multiple gas control methods with the aim of improving the gas drainage knowledge and techniques. Both of the CFD model and the mini mine gas emission zone based on U + L type ventilation network are established, and the gas distribution and movement rules of working face and goaf are accurately obtained during the numerical and laboratorial simulation experiments are performed. The results reveal that gas problems at working face and goaf cannot be effectively resolved by only increasing the air volume; instead, it must be combined with optimizing the ventilation network and excavating special gas drainage tunnels. The experimental results also demonstrate that the most effective gas extraction spot constantly varies with the zone where mining activities are performed. Therefore, the arrangement of gas drainage tunnels is determined according to the obtained rules and experimental results. The field verification results show that the layout of the drilling boreholes is rational and effective; the gas drainage quantity is reliable and stable, which indicates that it is valid and feasible to arrange the layout of gas drilling tunnels based on the combination experimental results of numerical simulations and laboratory tests.
Four strategies can be used to achieve safety in chemical processes: inherent, passive, active and procedural; however, the one that offers better results is the inherent safety approach, especially if applied at the initial stages of a project. Inherently Safer Design (ISD) permanently eliminates or reduces hazards to avoid or reduce the consequences of incidents, and can be applied using four strategies: substitution, minimization, moderation and simplification. In this paper, a methodology which allows combining ISD strategies with Quantitative Risk Assessment (QRA) in order to optimize the design of storage installations is proposed; taking into account that 17% of the major accidents in the chemical industry occur during the storage process, causing significant losses, it becomes important to improve safety in these installations. The proposed method applies QRA to estimate the risk associated to a specific design, which can later be compared to others in order to decide which one is inherently safer, incorporating complex phenomena like the domino effect and possible affectation to material and human vulnerable elements. The methodology is applied to two case studies, one based on the San Juanico tragedy occurred in Mexico, 1984, and another one focused on a chlorine storage installation; in this way the method is evaluated on two types of plant, one related to flammable materials and another to toxic substances.
Mary, G.; Dorado, A.D.; Fortuny, M.; Gabriel, D.; Gamisans, X. Process safety and environmental protection Vol. 92, num. 3, p. 261-268 DOI: 10.1016/j.psep.2013.02.002 Data de publicació: 2014-05-01 Article en revista
An industrial-scale biotrickling filter for the removal of high concentrations of H2S is described in this work. The system has been operating at H2S inlet concentrations between 1000 and 3000 ppmv at acidic conditions. A decrease of pH from 2.6 to 1.8 did not affect the biological activity inside the biofilter while reducing the water make-up consumption up to 75%. The current oxygen supply system, based on direct injection of air to the liquid phase, has demonstrated to be inefficient for a long-term operation leading to elemental sulfur accumulation in the packing material (i.e. promoting clogging episodes). The present study demonstrates it is possible to partially remove (40.3%) the deposited elemental sulfur by bio-oxidation when biogas is not fed. In normal operation conditions, the implementation of an aeration system based on jet-venturi devices has shown quite promising results in terms of oxygen transfer efficiency and robustness. Such improvement of oxygen transfer was translated in a better conversion of H2S to sulfate, which increased around 17%, prolonging the lifespan operation at low-pressure drop.
It is well known that the domino effect can have a major impact on accidents in storage facilities, as it can increase the consequences of an initial event considerably. However, quantitative risk assessments (QRAs) do not usually take the domino effect into account in a detailed, systematic way, mostly because of its complexity and the difficulties involved in its incorporation. We have developed a simple method to include the domino effect in QRAs of storage facilities, by estimating the frequency with which new accidents will occur due to this phenomenon. The method has been programmed and implemented in two case studies. The results show that it can indeed be used to include the possibility of domino effect occurrence in a QRA. Furthermore, depending on the design of a facility, the domino effect can have a significant effect on the associated risk.
Darbra, R.M.; Casal, J.; Pastor, E.; Vílchez, J.; Arnaldos, J.; Planas, E. Process safety and environmental protection Vol. 90, num. 5, p. 430-435 DOI: 10.1016/j.psep.2012.06.002 Data de publicació: 2012 Article en revista
Risk analysis is a topic of high relevance in chemical engineering. Courses on this topic are being introduced increasingly
into the university curricula. The investigation of real cases is an interesting opportunity to consolidate the
concepts taught in such courses and to get a better engagement of students through a creative work. The exercise
proposed in this paper has to be performed by a group of students to whom a set of information has been provided.
In the exercise, the students play the role of an expert team: they have to deliver a final report including diverse
sections such as the description of the accident, the explanation of why and how it occurred, different calculations
and finally, some conclusions. From the pedagogical point of view, the results obtained from this type of exercise are
very positive and promote the students active and cooperative learning.
Dunjó, J.; Fthenakis, V.; Darbra, R.M.; Vilchez, J.; Arnaldos, J. Process safety and environmental protection Vol. 89, num. 4, p. 214-223 DOI: 10.1016/j.psep.2011.03.001 Data de publicació: 2011-07 Article en revista
Dunjó, J.; Fthenakis, V.; Darbra, R.M.; Vilchez, J.; Arnaldos, J. Process safety and environmental protection Vol. 89, num. 4, p. 224-233 DOI: 10.1016/j.psep.2011.03.002 Data de publicació: 2011-07 Article en revista
In the present work a fuzzy logic model to preliminary assess the risk of accidental releases of ecotoxic substances in hazard plants has been developed. The methodology is based in three steps, the characterization of the hazardousness of the substance, the delimitation of the soil and groundwater vulnerability and the identification of the protective and preventive measures of the plant. The tool has been tested with a set of storage yards of ecotoxic substances, mainly oil, in the Regione Piemonte area (Italy). The results obtained are in good agreement with the real situation of the surveyed storage yards. Thus, by using this methodology it is possible to preliminary assess the risk from uncertain data.
Stüber, F.; Font, J.; Eftaxias, A.; Paradowska, M.; Suárez-Ojeda, M.E.; Fortuny, A.; Fabregat, A. Process safety and environmental protection Vol. 83, num. 4, p. 371-380 DOI: 10.1205/psep.05017 Data de publicació: 2005-07 Article en revista