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Recent Canadian advances in nuclear-based hydrogen production and the thermochemical Cu-Cl cycle
Greg F. Naterer, S. Suppiah, M. Lewis, K. Gabriel, İbrahim Dinçer, Marc A. Rosen, Michael Fowler, G. Rizvi, E. B. Easton, B. M. Ikeda, M. H. Kaye, L. Lu, I. Pioro, P. Spekkens, P. Tremaine, J. Mostaghimi, Jurij Avsec, J. Jiang, 2009, izvirni znanstveni članek

Opis: This paper presents recent Canadian advances in nuclear-based production of hydrogen by electrolysis and the thermochemical copper-chlorine (Cu-Cl) cycle. This includes individual process and reactor developments within the Cu-Cl cycle, thermochemical properties, advanced materials, controls, safety, reliability, economic analysis of electrolysis at off-peak hours, and integrating hydrogen plants with Canada's nuclear power plants. These enabling technologies are being developed by a Canadian consortium, as part of the Generation IV International Forum (GIF) for hydrogen production from the next generation of nuclear reactors.
Ključne besede: nuclear-based hydrogen production, thermochemical copper-chlorine cycle, electrolysis
Objavljeno: 31.05.2012; Ogledov: 1107; Prenosov: 52
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Influence of small solar power plants on power quality
Sebastijan Seme, Jurček Voh, Jože Voršič, 2012, objavljeni znanstveni prispevek na konferenci

Opis: The solar power plants are usually connected to the distribution network in node with transformer. Small, mini and micro solar power plants are connected as real dispersed production in the middle or at the end of line as consumers.This paper describes measurements, according to standard SIST EN 50160, at 274 m long line, fed at one side from 20/0,4 kV transformer and at the other side from small solar power plant and in between are 15 users (houses).
Ključne besede: dispersed production, small solar power plants, SIST EN 50160, measurements
Objavljeno: 01.06.2012; Ogledov: 1426; Prenosov: 0

Kefir grains production - An approach for volume optimization of two stage bioreactor system
Andreja Goršek, Marko Tramšek, 2008, izvirni znanstveni članek

Opis: The main objective of the present study was to design a continuous two-stage bioreactor system for kefir grains production. Based on the experimental data of time-depended kefir grain mass increase and average pH profile during kefir grains batch propagation, parameters of predictive growth and exponential pH models were initially estimated. Afterwards, the non-linear programming (NLP) optimization problem for estimating the optimal volumes of two unequal in series connected continuously stirred tank bioreactors (CSTB) has been developed. The NLP problem is based on criterion of minimal total holding time (MTHT), kefir grain mass balances in CSTB and parameters of the growth and pH models. The results showed that novel kefir grains production plant with two-stage continuous operation, at capacity, qm,KG,pr=3 kgh-1 and conversion, Xo,2=0.980, would primarily require investment in two CSTB with V1=5.93 m3 and V2=5.62 m3, respectively. Technological and economical authorization for a two-stage continuous bioreactor system was mainly confirmed with a more than five times lower total bioreactor volume compared to one-stage plant.
Ključne besede: chemical processing, bioprocesses, milk products, kefir grains production, bioreactor design, modeling, optimization
Objavljeno: 31.05.2012; Ogledov: 1807; Prenosov: 63
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Energy saving and modifications in the methanol process, using the NLP model optimization
Anita Kovač Kralj, Peter Glavič, 2006, objavljeni znanstveni prispevek na konferenci

Opis: The opportunities for additional profit depend very much on the existing plant and energy system. Heat and power integration can reduce fuel usage in chemical processes. Nonlinear programming contains equations which enable structural and parametric optimization. The NLP model is formulated using an optimum energy target of process integration and electricity generation using a gas turbine with separator. The reactor acts as a combustion chamber of the gas turbine plant, producing a lot of energy. The simultaneous NLP approach can account for capital cost, integration of combined heat and power, process modification and additional production of trade-offs, and can thus yield a better solution. The combined production of electricity, heat and chemical products can lead to better process efficiency. The methanol plant was optimized using a mathematical nonlinear programming model by including an additional flowrate of hydrogen in crude methanol recycle and increasing the methanol production by 2,5%. The electricity can be generated in methanol recycle using a gas turbine. The total additional profit is 2,5 MEUR/a.
Ključne besede: chemical engineering, methanol production, simultaneous process optimization, nonlinear programming, cogeneration, product increase
Objavljeno: 30.05.2012; Ogledov: 1430; Prenosov: 12
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Review of sustainability terms and their definitions
Peter Glavič, Rebeka Kovačič Lukman, 2007, izvirni znanstveni članek

Opis: Terminology in the field of sustainable development is becoming increasingly important because the number of terms continues to increase along with the rapid increase in awareness of the importance of sustainability. Various definitions of terms are used by different authors and organizations, for example, green chemistry, cleaner production, pollution prevention, etc. The importance of this topic has stimulated research into the problems of clarifying ambiguity and classifying terms used in the sustainability field. This paper provides results of the literature survey and summarizes the definitions of the terms, focusing on the environmental engineering field. In some cases, it proposes an improved definition. A hierarchical classification of the terms and their relationships has been based on a layer format that is presented graphically.
Ključne besede: chemical process design, sustainability, environmental protection, cleaner production, terminology, definitions, classification
Objavljeno: 31.05.2012; Ogledov: 1323; Prenosov: 66
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Fuzzy Logic Model for the performance benchmarking of sugar plants by considering best available techniques
Damjan Krajnc, Miro Mele, Peter Glavič, 2007, izvirni znanstveni članek

Opis: This paper deals with the problem of performance benchmarking of traditional beet sugar plants, by considering Best Available Techniques (BAT) for beet sugar production, as determined by the Integrated Pollution Prevention and Control (IPPC) Directive. A Fuzzy Logic Model, based on fuzzy set theory, was constructed for this purpose, in order to compare the performances of sugar plants within the sector's best standards, as expressed in the Reference Document on BAT. The effectiveness of the model was tested in the case study,in which three sugar plants were benchmarked against the BAT regarding the consumption of energy, water, raw materials and the production of wastes, wastewater, by-products and the main product. The model was recognized as helpful for the benchmarking needs of sugar plants. In addition, by integrating BAT Reference Document analysis into the model, it provides IPPC permitting authorities with an objective method and uniform BAT benchmarks to manage permitting process.
Ključne besede: chemical processing, beet sugar production, sugar industry, clean technologies, performance benchmarking, IPPC Directive, technology performance assessment, fuzzy set theory, best available techniques, IPPC permitting process
Objavljeno: 31.05.2012; Ogledov: 1600; Prenosov: 48
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CO2 separation from purge gas and flue gas in the methanol process, using NLP model optimization
Anita Kovač Kralj, Peter Glavič, 2007, izvirni znanstveni članek

Opis: The concentration of CO2 in the atmosphere has to be stabilized, requiring a reduction in current emission rates in existing plants. This will be done by reducing the environmental burden imposed in such areas as materials input andCO2 emission reduction and using cleaner production, resources, and energy recycling. Any opportunities for emission reduction and CO2 reuse largely depend on existing plant and energy systems. CO2 can be separated from the outlet stream (purge gas) and from flue gas by a membrane or absorption system(absorber and regenerator) or adsorption system and reused as a reactantin a reactor system. Therefore, product yield can be increased and CO2emissions reduced, simultaneously. CO2 emissions can be reduced at the source. The authors of this paper studied CO2 reuse in a methanol process, in which electricity can be generated using an open gas turbine, followed by a separator. Simultaneous optimization of a process structure and its parametersusing simplified nonlinear programming (NLP) ensures an additional annual profit, influenced by reusing the flow rate of CO2. The additional electricity cogeneration and additional flow rates of the raw material could generate an additional profit of 2.79 MEUR/a.
Ključne besede: chemical processing, methanol production, optimization, nonlinear programming, CO2 emissions, CO2 reuse
Objavljeno: 31.05.2012; Ogledov: 1191; Prenosov: 44
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H2 separation and use in fuel cells and CO2 separation and reuse as a reactant in the existing methanol process
Anita Kovač Kralj, Peter Glavič, 2007, izvirni znanstveni članek

Opis: Fuel-cell efficiencies yield substantial reductions in the emissions of climate-change gases and promise an end to exclusive reliance on carbon fuels for energy. Fuel cells, CO2 reuse, process heat integration, and open gas turbine electricity cogeneration can be optimized simultaneously, using a nonlinear programming (NLP) algorithm. The simplified NLP model contains equations of structural and parametric optimization. This NLP model is used tooptimize complex and energy-intensive continuous processes. This procedure does not guarantee a global cost optimum, but it does lead to good, perhaps near-optimum, designs. The plant, which produces methanol, has a surplus of hydrogen (H2) and CO2 flow rates in purge gas. H2 is separated from the purge gas by an existing pressure swing adsorption (PSA) column. Pure H2 can be usedas fuel in fuel cells. CO2 can be separated from the outlet stream (purge gas) by a membrane or absorption system (absorber and regenerator) or an adsorption system and reused as a reactant in a reactor system. Therefore, theproduct yield can be increased and CO2 emissions can be reduced, simultaneously. CO2 emissions can then be reduced at the source. The retrofitted process can be operated within existing parameters. Using a methanol process as a case study, the CO2 emission flow rate can be reduced by4800 t/a. The additional electricity cogeneration in the gas turbine and in fuel cells and additional flow rates of the raw material could generate an additional profit of 2.54 MEUR/a.
Ključne besede: chemical processing, methanol production, optimization, nonlinear programming, CO2 reuse, fuel cells, heat integration, energy cogeneration
Objavljeno: 31.05.2012; Ogledov: 1532; Prenosov: 39
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Development and validation of business process reengineering (BPR) variables: a survey research in Slovenian companies
Nataša Vujica-Herzog, Andrej Polajnar, Stefano Tonchia, 2007, izvirni znanstveni članek

Opis: Business Process Reengineering (BPR) literature is based primarily on case studies and there is a lack of rigorous wide-ranging empirical research covering all its aspects. This paper presents the results of a survey researchcarried out in 73 medium and large-sized Slovenian manufacturing companies. Seven crucial areas were identified based on a synthesis of BPR literature, which must be practised to achieve effective process reengineering: management commitment, education & training, team work, BPR project characteristics, employee cooperation, information technology support,and levers & results. Variables have been constructed within these areas, using Likert scales, and statistical validity and reliability analyses.These developed variables can be important both for understanding BPRand in terms of the descriptive statistics, also reported in this paper. What emerges is the crucial importance of process orientation, goal setting, and top management commitment. Furthermore, these variables can be helpful forfurther research aimed at investigating BPR and its linkages with other areas, such as strategy, performance measurement, etc.
Ključne besede: production management, process management, business process reingeneering, survey research
Objavljeno: 31.05.2012; Ogledov: 1035; Prenosov: 60
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