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31.
32.
Identification of critical points for the design and synthesis of flexible processes
Zorka Novak-Pintarič, Zdravko Kravanja, 2008, izvirni znanstveni članek

Opis: Optimization problems for the design and synthesis of flexible chemical processes are often associated with highly discretized models. The ultimate goal of this work is to significantly reduce the set of uncertain parameter points used in these problems. To accomplish the task, an approach was developed for identifying the minimum set of critical points needed for flexible design. Critical points in this work represent those values of uncertain parameters that determine optimal overdesign of process, so that feasible operation is assured within the specified domain of uncertain parameters. The proposed approach identifies critical values of uncertain parameters a-priori by the separate maximization of each design variable, together with simultaneous optimization of the economic objective function. During this procedure, uncertain parameters are transformed into continuous variables. Three alternative methods are proposed within this approach: the formulation based on Karush-Kuhn-Tucker (KKT) optimality conditions, the iterative two-level method, and the approximate one-level method. The identified critical points are then used for the discretization of infinite uncertain problems, in order to obtain the design with the optimum objective function and flexibility index at unity. All three methods can identify vertex or even nonvertex critical points, whose total number is less than or equal to the number of design variables, which represents a significant reduction in the problem's dimensionality. Some examples are presented illustrating the applicability and efficiency of the proposed approach, as well as the role of the critical points in the optimization of design problems under uncertainty.
Ključne besede: chemical processing, process synthesis, flexibility, design, critical point, vertex, nonvertex
Objavljeno: 01.06.2012; Ogledov: 1005; Prenosov: 49
URL Povezava na celotno besedilo

33.
Assessment of the consequences of accident scenarios involving dangerous substances
Zorka Novak-Pintarič, 2007, izvirni znanstveni članek

Opis: This paper highlights the major steps in the procedure for evaluating the consequences of accidents involving dangerous substances, especially during storage, loading and unloading activities. The procedure relies on identifying accident scenarios that could be encountered in particular plants, followed by modelling of these scenarios by means of available modelling systems. Finally, the resultant outcomes are identified, together with their effects on both people and property. The resources needed to perform this proceedure are discussed, in order to clarify the roles of operators, external experts and other institutions when evaluating any accident conesquences. Four examples, all relevant in industrial practice, are given in order to illustrate the procedure: the releasing of liquefied petroleum gas, flammable organic solvents, toxic chlorine, and fuel oil. The results of these studies may be used for a quick order-of-magnitude estimation of accidents consequences.
Ključne besede: chemical industries, dangerous substances, transportation, storage, risk, accidents, consequences estimation, Seveso II, loading, unloading, safety report
Objavljeno: 01.06.2012; Ogledov: 1235; Prenosov: 57
URL Povezava na celotno besedilo

34.
A strategy for MINLP synthesis of flexible and operable processes
Zorka Novak-Pintarič, Zdravko Kravanja, 2004, izvirni znanstveni članek

Opis: Abstract This paper presents a sequential two-stage strategy for the stochastic synthesis of chemical processes in which flexibility and static operability (the ability to adjust manipulated variables) are taken into account. In the first stage, the optimal flexible structure and optimal oversizing of the process units are determined in order to assure feasibility of design for a fixed degree of flexibility. In the second stage, the structural alternatives and additional manipulative variables are included in the mathematical model in order to introduce additional degrees of freedom for efficient control. The expected value of the objective function is approximated in both stages by a novel method, which relies on optimization at the central basic point (CBP). The latter is determined by a simple set-up procedure based on calculations of the objective functionćs conditional expectations for uncertain parameters. The feasibility is assured by simultaneous consideration of critical vertices. The important feature of the proposed stochastic model is that its size depends mainly on the number of design variables and not on the number of uncertain parameters. The strategy is illustrated by two examples for heat exchanger network synthesis.
Ključne besede: chemical processing, process synthesis, MINLP, mixed integer nonlinear programming, flexibility, operability, controllability, steady state model
Objavljeno: 01.06.2012; Ogledov: 1518; Prenosov: 49
URL Povezava na celotno besedilo

35.
Estimation of solid solubilities in supercritical carbon dioxide: Peng-Robinson adjustable binary parameters in the near critical region
Mojca Škerget, Zorka Novak-Pintarič, Željko Knez, Zdravko Kravanja, 2002, izvirni znanstveni članek

Opis: The density dependence of the binary parameters of the Peng-Robinson equation of state in near the critical region was examined. Published solubility data of eight compounds in pure CO2 have been fitted to the Peng-Robinson equation in combination with one and two parameters van der Waals mixing rules and in combination with the three parameter density dependent mixing rule of Mohamed and Holder. A systematic study has been done to determine the influence of different terms in the mixing rules. In order to obtain density dependence, binary parameters were calculated for each isotherm at particular experimental point separately in the way to equalise experimental and calculated solubility data. The system was formulated as an equation-oriented model and solved by means of a nonlinear programming optimisation algorithm. For all compounds the binary interaction parameters thus obtained were found to vary strongly with pressure in the range from 75 bar to approximately 150 bar, i.e. near the critical end point (CEP) of the low temperature branch of the three phase solid-liquid-gas (SLG) curve. At higher pressures, the parameter is practically independent on pressure. In general, for the systems investigated, kij increases linearly with increasing density and reaches a constant value at higher densities in the range from 700 to 800 kg/m3, depending on the system under investigation.
Ključne besede: solid liquid equilibria, equation of state, mixing rules, binary parameters, near critical region, nonlinear programming, thermodynamic model, supercritical fluids, CO2, solubility
Objavljeno: 01.06.2012; Ogledov: 1331; Prenosov: 60
URL Povezava na celotno besedilo

36.
Ocenjevanje posledic nesreč z naftnimi derivati
Petra Zver, 2013, diplomsko delo

Opis: V diplomskem delu so opisani scenariji nesreč z naftnimi derivati, ki smo jih definirali na osnovi razpoložljivih podatkov v literaturi. Opredelili in ovrednotili smo najverjetnejše in najtežje scenarije, na primer nenadni izpust iz rezervoarja, iztekanje iz vagonske ali avtocisterne, prepolnitev rezervoarja in razpok drenažnega ventila. Modeliranje scenarijev in napovedovanje posledic smo izvedli z računalniškim programom Phast. Upoštevali smo različne vremenske pogoje, kot so: letni čas, temperatura, vlažnost zraka, hitrost vetra itd. Posledice razlitja naftnih derivatov so lahko hude, kot je pokazala nesreča v skladišču goriv Buncefield, v Veliki Britaniji leta 2005. Rezultati ocenjevanja posledic kažejo, da lahko tudi majhne nepravilnosti in napake pri ravnanju z naftnimi derivati privedejo do hudih posledic, ki imajo že pri majhnih izpustih velika območja vplivanja. Zato mora vsako podjetje, ki se ukvarja z nevarnimi snovmi, izvesti celovito oceno tveganja za zmanjšanje nevarnosti in ustrezno ukrepanje ob izrednih dogodkih.
Ključne besede: gorivo, nesreča, scenarij, posledice, računalniški program Phast
Objavljeno: 26.03.2013; Ogledov: 1099; Prenosov: 151
.pdf Celotno besedilo (1,79 MB)

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Razvoj produktov in procesov : zbirka nalog za računske vaje
Zorka Novak-Pintarič, 2014, drugo učno gradivo

Opis:
Ključne besede: razvoj procesov, razvoj produktov
Objavljeno: 30.05.2014; Ogledov: 884; Prenosov: 38
.pdf Celotno besedilo (58,18 KB)

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