Design optimization of storage facilities taking into account the domino effect

Storing hazardous substances is a process that entrails high risk, and in which many resources are spent in the planning of safety measures; however, safety could be included at the initial stages of the design of this type of installations, by optimizing the number of tanks that are used to store the substance. The effects and consequences of major accidents are directly proportional to the mass of materials involved in them; therefore, if the mass was divided in more containing units, the consequences at the moment of an accident occurrence would be lesser. However, as more units are used to store a dangerous substance in an installation, the risk of domino effect occurrence at the moment of an accident also increases. The objective of this paper is to develop a methodology that allows finding the optimum number of units that have to be used to store dangerous materials, taking the possibility of domino effect occurrence into account. The proposed methodology is described and applied to a case study as a decision making tool, obtaining results that demonstrate that the design of storage installations can be improved from a risk point of view, by combining quantitative risk analysis and optimization techniques.Postprint (published version

Estudi de l'estabilització dels llits fluïditzats sòlios-gas mitjançant l'aplicació d'un camp magnètic

La tesi s’inicia fent una presentació del comportament dels llits estabilitzats magnèticament i de les seves aplicacions, així com de les limitacions que tenen degut a les pèrdues de les propietats magnètiques en certes condicions.A continuació, es proposa un model matemàtic dels llits fluïditzats estabilitzats magnèticament, basat en la distribució que segueixen les partícules amb les línies del camp. L’estabilització magnètica també s’ha aplicat a llits fluïditzats amb barreges de partícules magnètiques i no magnètiques. S’ha estudiat el comportament d’aquests sistemes, així com la influència de la fracció màssica de material magnètic en el retard en l’aparició del bombolleig. Els resultats obtinguts mostren que l’estabilització magnètica pot aplicar-se no solament a la fluïdització de partícules magnetitzables sinó també a partícules no magnetitzables, si una certa fracció de material magnètic és present en el llit. Es proposen diferents correlacions per al càlcul de la velocitat de transició en funció de les propietats del sistema gas-sòlid i les condicions d’operació.També s’estudia l’efecte del camp magnètic sobre el comportament tèrmic dels llits fluïditzats de partícules magnètiques escalfats amb una superfície calefactora introduïda dins el llit. S’ha determinat la distribució axial i radial de temperatures en el llit. A partir dels resultats experimentals, s’ha desenvolupat un model que permet el càlcul de la conductivitat tèrmica efectiva del llit. A més, mitjançant l’aplicació de l’analogia de Chilton i Colburn a les dades experimentals obtingudes, s’han proposat diferents correlacions per a l’estimació del coeficient de transferència de calor en llits estabilitzats i semi estabilitzats.Finalment, s’ha estudiat experimentalment, mitjançant l’assecament d’aire humit en llits formats per barreges d’alúmina-acer, la transferència de matèria en llits estabilitzats i semi estabilitzats. S’han emprat dos paràmetres, eficiència del llit i factor de eficiència, per comparar el comportament dels diferents tipus de llits. La precisió del model teòric desenvolupat s’ha provat amb els resultats experimentals obtinguts. Els models corresponents als llits fluïditzats clàssics no presenten un bon ajust amb les dades experimentals; ara bé, quan aquests models són modificats tenint en compte l’efecte del camp magnètic, l’ajust amb les dades és molt millor.First, in this thesis, the behaviour of the magnetically stabilized fluidized bed is presented, as well as its applications; the limitations due to the loss of magnetic properties in certain conditions are also considered.Later, a mathematical model of the magnetically stabilized fluidized bed, based on the arrangement of particles following field lines is proposed. Magnetic stabilization has also been applied to fluidized beds with mixture of magnetisable and non-magnetisable particles. The behaviour of these systems is studied, as well as the influence of the magnetic material mass fraction on the delay of bubbling. The results obtained show that the magnetic stabilization can be applied not only to the fluidization of magnetisable materials but also to non-magnetisable particles, if a certain fraction of magnetisable material is present. Correlations are proposed to calculate the transition velocity as a function of gas-solid properties and operating conditions.Also, the effect of the magnetic field on the thermal behaviour of a fluidized bed of magnetisable particles with an immersed heating surface has been studied. The temperature distribution inside the bed has been determined, both in the radial and axial directions. A model has been developed which allows calculation of the effective thermal conductivity of the bed from experimental data. In addition, by means of the application of the Chilton and Colburn analogy to the experimental data obtained, different correlations for the estimation of the heat transfer coefficient in stabilized and semi-stabilized beds have been proposed.Finally, the mass transfer in magnetically stabilized and semi-stabilized beds has been studied experimentally using the drying of moist air in beds of alumina-steel mixtures. Two parameters, bed efficiency and efficiency factor have been used to compare the behaviour of the different beds. The accuracy of the theoretical model developed has been tested using the results obtained. The models corresponding to the classical fluidized bed do not agree with experimental data; however, when these models are modified to take into account the effect of magnetic stabilization, the accuracy is much better

Multi-objective optimization of hazardous substance storage facilities. The decision between risks and costs associated to the project

The design storage installations for dangerous substances can be optimized from a safety and risk point of view by combining quantitative risk analysis and mathematical optimization techniques; the consequences of accidents are directly proportional to the mass involved in them, which means that in a storage installation, if the totality of the stored substance is divided into more tanks, the consequences when an accident occurs in any of the units will be less significant than if all the mass was stored in one tank (in installations where there is low possibility of domino effect occurrence). However, as more tanks are used to store the mass, the economical investment will also increase; then, a situation arises between two conflicting objectives, that can be solved through the use of multi objective optimization.Postprint (published version

Experimental methodology for characterizing flame emissivity of small scale forest fires using infrared thermography techniques

An experimental methodology based on thermography techniques has been developed and implemented with the aim of finding emissivity values of forest fuel flames. In this paper, previous works by different authors are discussed and theoretical fundamentals of heat transfer by radiation and of infrared thermography on which experimental method relies are briefly described. Then, designed methodology, equipments, devices and experimental tests are detailed in depth. Finally, analysis procedure is pointed out and some conclusions from the study of theresults are announced.Postprint (published version

Avaluació de l'engegada de la cubeta nº 2 en el marc de l'ampliació de la planta de recepció, emmagatzematge i distribució que Terquimsa té ubicada al moll d'inflamables al Port de Barcelona

Preprin

Avaluació de l'engegada de la cubeta nº 10 en el marc de l'ampliació de la planta de recepció, emmagatzematge i distribució que Terquimsa té ubicada al moll d'inflamables al Port de Barcelona

Preprin

Optimizing the design of storage facilities through the application of ISD and QRA

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.Peer Reviewe