Iskanje po katalogu digitalne knjižnice

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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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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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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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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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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