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Direct enthalpy exchange between process utilities
Zorka Novak-Pintarič, Peter Glavič, 2002, strokovni članek

Opis: This paper presents an application of the improved pinch methodology by performing a simplified exergy analysis in a real-size ammonia plant. Besides the well known pinch technics like composite curves and grand composite curve, the improved approach with the extended grand composite curve was implemented. The latter presents the most energy intensive units in the process separated from the process background as well as the direct transfer of enthalpy from hot utilities to cold utilities. Based on this presentation the synthesis of modified heat exchanger network was performed which results in considerable decrease of utilities demand.
Ključne besede: chemical engineering, process design, exergy analysis, ammonia plant, pinch methodology, extended hrand composite curve method, enthalpy exchange, distillation column, heat exchanger network
Objavljeno: 10.07.2015; Ogledov: 916; Prenosov: 53
.pdf Celotno besedilo (182,17 KB)
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“Thermodynamic and physical properties for high pressure process design”
Maša Knez Hrnčič, 2014, doktorska disertacija

Opis: The thesis is comprised of three main categories. The first part of dissertation covers investigations of phase equilibria of compounds from natural materials in conventional and also non conventional supercritical fluids. In details, the impact of pressure and/or temperature on the system behaviour (miscibility, solubility, phase inversion) is investigated, quantitative and qualitative analyses to evaluate and identify compounds contained after performing preliminary extraction experiments from different natural tissues are presented. The impact of operating parameters (pre-treatment of the raw material with SFE; different extraction solvents: propane, CO2, non conventional SCFs; different extraction temperatures and pressures) on extraction kinetics is observed. Following substances were taken into consideration: vanillins, caffeine, carnosoic acid extract and lecithin. Second part of dissertation covers studies of phase equilibria of the systems bio oil/gas, which is crucial in biorefinery process design. In this part of dissertation, which covers studies of phase equilibria of binary and ternary systems, the impact of pressure and/or temperature on the system behaviour (miscibility, solubility, phase inversion) for binary system bio oil/supercritical fluid (bio oil/CO2) and (bio oil/H2) was studied. Additionally, phase behaviour of ternary systems of (bio oil/diesel/CO2) and (bio oil/tail water/CO2) under the impact of pressure and/or temperature is observed. These data are of a high importance for bio refineries as an important part of necessary sustainable development. In recent years, studies on biodiesel synthesis have focused on development of process intensification technologies to resolve some of these issues. Fundamental data to design fractionation process of components of bio oil are crucial for an efficient hydrogenation process of bio oil. In the third part of dissertation observation of phase equilibria and determination of the parameters like diffusion coefficient, density and viscosity for the systems polymer/CO2 at elevated pressures is investigated. An overview of different methods applied to determine the parameters like diffusion coefficient, density and viscosity of the systems polymer (PEG)/CO2 at elevated pressures is offered. Observation of phase equilibria of the binary system PEG/CO2, determination of the impact of pressure and/or temperature on the system behaviour (miscibility, solubility, phase inversion), determination of thermodynamically and physically properties of the system with new applicative methods and finally, comparison of the results obtained by different methods is provided. The interfacial tension (IFT) at the (PEG)/CO2 interface has been determined by using an experimental technique developed to study the interfacial interactions of the liquids in equilibrium with gas in a glass-windowed equilibrium cell by the means of Capillary Rise (CR) method. Advantages and disadvantages of methods that were applied are exposed and discussed.
Ključne besede: phase equilibria, natural materials, conventional and non conventional supercritical fluids, extraction, bio oil, data for biorefinery process design, systems polymer (PEG)/CO2, diffusion coefficient, density, viscosity, surface tension, Capillary Rise (CR) method.
Objavljeno: 28.10.2014; Ogledov: 1735; Prenosov: 250
.pdf Celotno besedilo (4,46 MB)

Uvajanje računalniško podprte proizvodnje
Uroš Trupej, 2013, diplomsko delo

Opis: V svoji diplomski nalogi sem se osredotočil na uvajanje računalniško podprte proizvodnje in kakšne prednosti prinaša. Računalniško podprta proizvodnja združuje moderno računalniško tehnologijo z naprednimi obdelovalnimi stroji in povezavo z informacijskim sistemom, kjer je človek še vedno vodilo napredka. Na teoretičnem primeru sem prikazal kakšne spremembe mora neko podjetje opravit in kakšne pogoje mora zadostiti, da lahko uvede računalniško podprto proizvodnjo.
Ključne besede: RIP - Računalniško integrirana proizvodnja, CIM - Computer integrated manufacturing, CAD - Computer Aided Design.CAM - Computer Aided Manufacturing, CAE - Computer Aided Engeneering, CAQ - Computer Aided Quality Assurance, CAPP - Computer Aideded Process Planning, CABS - Computer Aideded Business Sysytem, CAST - Computer Aideded Storagee and Transport, CNC - Computer Numerical Control, POS - Prilagodljivi obdelovalni stroji
Objavljeno: 16.10.2013; Ogledov: 1409; Prenosov: 179
.pdf Celotno besedilo (2,14 MB)

Investigations of the structure and process parameters of sewing operation
Daniela Zavec Pavlinič, Zvonko Dragčević, Dubravko Rogale, Jelka Geršak, 1999, izvirni znanstveni članek

Opis: An original measuring equipment and a system for investigating process parameters of the sewing operation structure and for establishing optimal working methods and real working conditions of the man-machine system in garment sewing are presented. The measuring equipment consists of a process parameter measuring and data storing system and a bi-plane video recording system. The measuring and data storage system is equipped with four sensors which measure the rotation speed of the main shaft, the movements of arms in the picking-up and laying-off zones, and the movements of the pedal regulator used to control the sewing dynamics. The bi-plane video recording system is used to record simultaneously the working movements (working methods) performed at the discussed workplace. From the process parameter measurements graphs for the technological operation structure are obtained, including the duration of individual suboperations and changes occuring due to pedal regulator movements. The bi-plane video recording system investigates the working method employed, the basic movements and and the optimal logical sets of movements, as well as the cyclograms of the movements used to define space and time values. The results obtained are compared with the MTM results, and the differences between them are presented.
Ključne besede: textile industry, garment engineering, sewing operation structure, process parameters, bi-plane video recording, workplace design
Objavljeno: 01.06.2012; Ogledov: 1521; Prenosov: 31
URL Povezava na celotno besedilo

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: 1293; Prenosov: 75
URL Povezava na celotno besedilo

Synthesis of non-isothermal heat integrated water networks in chemical processes
Miloš Bogataj, Miguel J. Bagajewicz, 2008, izvirni znanstveni članek

Opis: This paper presents a new approach for the simultaneous synthesis and optimization of heat integrated water networks. A new superstructure for heat exchanger network (HEN) synthesis is proposed. The procedure is based on mixed integer non-linear mathematical programming (MINLP). Four relevant examples are presented to illustrate various aspects of the proposed approach.
Ključne besede: chemical processing, chemical process design, process water networks, water networks, wastewater minimization, heat integration, MINLP, HEN synthesis, superstructures, process synthesis
Objavljeno: 31.05.2012; Ogledov: 1523; Prenosov: 75
URL Povezava na celotno besedilo

Analysis of growth models for batch kefir grain biomass production in RC1 reaction system
Marko Tramšek, Andreja Goršek, 2008, izvirni znanstveni članek

Opis: This work describes the statistical analysis of three mathematical models, modified for describing the kefir grain biomass growth curve. Experimental data of time-dependent kefir grain mass increase were used. The propagation was performed in RC1 batch reaction system under optimal bioprocess parameters (temperature, rotational frequency of stirrer, glucose mass concentration) using traditional cultivation in fresh, high-temperature, pasteurized whole fat cow's milk. We compared values of biological parameters obtained by applying the nonlinear regression of experimental data in logistic, Gompertz and Richards models. The most statistically appropriate model was determined using the seven statistical indicators. We established that the kefir grain biomass growth curve during batch propagation under optimal bioprocess conditions can be most successfully described using the Gompertz growth model.
Ključne besede: chemical processing, milk products, kefir grain growth, process parameters, design of experiments, modeling, mathematical models, Gompertz growth model, RC1
Objavljeno: 31.05.2012; Ogledov: 2123; Prenosov: 112
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