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Equipment for Thickening Waste Water from Biogas Plants
Vondra, Marek ; Bébar, Ladislav (referee) ; Hoffman,, Pavel (referee) ; Stehlík, Petr (advisor)
This dissertation thesis deals with the development of technology which could tackle two major issues related to biogas plants. These issues concern the insufficient use of waste heat from biogas combustion and its subsequent processing. It also concerns the use of the fermentation residues which are formed in large quantities and whose use is restricted by law. Based on a literary search of separation methods, a vacuum evaporator was selected as the most suitable technology. Its advantages include its simple construction, operational reliability and robustness, low costs of thickening medium pre-treatment, potential for a quick commercial application and, especially, the chance to use a low-potential waste heat. A primary purpose of this technological unit is the reduction in the volume of fermentation residues. Other benefits include the efficient use of waste heat from a biogas plant, which would otherwise be wasted. Evaporators with a low consumption of electrical energy (which is a main product of a biogas plant) seem to be the best option for applications in the biogas plants. Three of these technologies were subjected to a more thorough analysis, which included the development of computational models and their quantification for conditions in a sample biogas plant. A one-stage evaporator with a forced circulation (680 – 712 kWhth/m3, 25.9 – 30.5 kWhel/m3) was evaluated as the least suitable option in terms of energy demands. The energy intensity of a three-stage evaporator with a falling film (241 – 319 kWhth/m3, 12.0 – 23.6 kWhel/m3) and a nine-stage flash evaporator (236 – 268 kWhth/m3, 13.6 – 18.4 kWhel/m3) is significantly lower. A multi-stage flash evaporator (MSF) was then chosen for development and will form the central focus of this thesis. The reasons for the choice are as follows: the low requirements on the heat transfer surface, good operational experience in the field of desalination, its simple construction, modularity and evaporation outside the heat transfer surface. A thorough technical-economic evaluation was also performed on the integration of the evaporator into the biogas plant. The main part of the work included the experimental development of a MSF evaporator prototype. The main objective of this development was to achieve a stable flow rate of the thickening liquid digestate fraction and the continuous formation of the distillate. This was not an easy objective to achieve, especially due to the properties of the liquid digestate, which has a non-newtonian characteristic and increased density and viscosity compared to water. The tendency of the liquid digestate to form foam was also the subject of analysis. The development of the evaporator and first successful operational test are described in the thesis in detail. This required the use of an anti-foaming product. A fully-developed prototype of the MSF evaporator allowed us to achieve continuous operation with a distillate production, reaching from 5 to 10 kg/h at a liquid digestate flow rate of 0.4–0.5 m3/h. The main drawback of this technology is the pollution of the distillate with ammonia nitrogen, and it is for this reason that the basic procedures of its subsequent elimination was selected for further analysis.
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The image of a the city in contemporary Croatian authors' writings. Edo Popović's and Robert Perišić's Zagreb - reality or illusion
Stuchlík, Jan ; Otčenášek, Jaroslav (advisor) ; Stehlík, Petr (referee)
The thesis The Image of the City in the Contemporary Authors' Writings-Edo Popović's and Robert Perišić's Zagreb-reality or illusion is a literary-culturological study of the image of the Croatian capital city Zagreb in the literary work of the contemporary Croatian authors Edo Popović and Robert Perišić. The thesis deals with the urban environment from sociological, cultural and literary aspects focusing on the situation in Croatia. The thesis illustrates the developement of the urban themes in the Croatian literature since the middle of the 19th century and their relation to similar themes in the world. Through the analysis of Edo Popović's and Robert Perišić's work the method which both authors use working with the urban subject is explicated, the features of Zagreb in their writings are outlined and last but not least the significance of their urban literature contextualized with other Croatian urban literature, characteristics of similar literature in Slovenia and at the European level in Great Britain are presented.
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Visualization of Network Security Events
Stehlík, Petr ; Kováčik, Michal (referee) ; Krobot, Pavel (advisor)
This thesis focuses on visualization of network security events via modern web technologies. Multiple technologies for creating modern web application supporting visualising large volume of security events were studied. The application was designed for NEMEA system which thanks to this thesis acquired graphical user interface allowing big data visual analysis. Visualized events allow drill-down analysis. The application operates on security events stored in IDEA format which is used among other network security services and the application is therefore transferrable to them. NEMEA Dashboard has been tested on the target group of network administrators using acceptance tests.
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Effective Investment Planning in Waste-to-Energy Systems
Šomplák, Radovan ; Klemeš,, Jiří (referee) ; Žaloudík, Petr (referee) ; Stehlík, Petr (advisor)
PhD thesis deals with the application of the simulation and optimization methods in the waste-to-energy field. An introduction describes the current state of the waste management in the EU with the focus on the Czech Republic. In the following chapter the evaluation criteria for investment intentions and the basic principles of stochastic programming are discussed. The core of the work lays in the mathematical models for the planning and operation of the process plants as well as in the mathematical models for the waste collection. The transportation problem involves all considered technological elements and therefore it is possible to simulate the waste streams between the producers and processors. This approach is demonstrated with five case studies. In the first three studies the calculations for the potential investor are presented. The main outcome of these case studies is the determination of the level of attractiveness of investment and the identification the greatest risks. Another case study is devoted to an analysis with the focus on perspective of government policies and in the last case study the issue of the waste management is analyzed in detail from the perspective of the waste producers. Developed computational tools are flexible and can be further developed and adapted based on the objectives of the specific tasks.
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Energy Intensity Reduction of a Professional Laundry Care Process
Bobák, Petr ; Klemeš,, Jiří (referee) ; Noskievič, Pavel (referee) ; Stehlík, Petr (advisor)
Doctoral thesis deals with professional laundry care process and reduction of energy intensity and use of other operational commodities used in the process. Professional laundry care process is a specific energy intensive process; its purpose is to re-establish original properties of the now dirty laundry so that it may fulfil its functions again. This is basically a recycling and regeneration process comprising many sub-operations. Key operation is washing of the laundry in a washing bath, which removes impurities from the laundry. This thesis describes the most common technology of impurities removal, which is washing in a hot washing bath in cooperation with mechanical work and detergents. However, all of the described procedures may also be applied on alternative technologies, such as ozone washing, washing with low-temperature enzymes and ultrasound. Water is applied in all these technologies as a soaking agent. Water must have appropriate properties and must be removed from the laundry after the washing process in subsequent operations (drying, ironing, and pressing). Theoretical introduction of the thesis describes professional laundry care process in detail, and continues with mathematical modelling of the process and its main sub-operations (washing, drying) using mass and heat balance, and data acquisition and their application in research and development. Thesis further describes design of information system on the basis of relational database controlled by web application. This system enables to organize data and information from various sources – measured experimental data, data concerning measurement devices, operational records of machines, etc. Thesis further proposes how to evaluate and reduce energy intensity of a process. Descriptions are validated by examples and case studies. Key section of the thesis is a chapter describing experimental infrastructure. This infrastructure integrates several instalments of laundry equipment and is a fully functional operation of industrial laundry facility with 500kg/shift capacity, which serves as a model of energy intensive process. Sophisticated infrastructure and data acquisition system allows measuring wide spectrum of physical entities and examining factors influencing energy intensity of processes, and relationships between these factors as well as effectiveness of various savings measures in real life facilities.
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Modelling as Efficient Tool in Industrial Practice and Economic Aspects
Šarlej, Marek ; Klemeš,, Jiří (referee) ; Žaloudík, Petr (referee) ; Stehlík, Petr (advisor)
This doctoral thesis focuses on modelling as an efficient tool in industrial practice in the field of power industry and environmental engineering. It represents the modelling for technical as well as for economic part and their combination. Industrial companies do not evaluate only technical solutions in terms of investment costs, however, they search for optimized technical-economic solutions. The doctoral thesis describes the modelling of individual equipment as well as technological units in various levels of complexity. Case studies utilising various levels of modelling are represented herein.
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Modelling as Efficient Tool in Industrial Practice and Economic Aspects
Šarlej, Marek ; Stehlík, Petr (advisor)
This doctoral thesis focuses on modelling as an efficient tool in industrial practice in the field of power industry and environmental engineering. It represents the modelling for technical as well as for economic part and their combination. Industrial companies do not evaluate only technical solutions in terms of investment costs, however, they search for optimized technical-economic solutions. The doctoral thesis describes the modelling of individual equipment as well as technological units in various levels of complexity. Case studies utilising various levels of modelling are represented herein.
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PERSPECTIVE METHODS OF SEWAGE SLUDGE UTILISATION FOR ENERGY PRODUCTION
Elsässer, Thomas ; Klemeš,, Jiří (referee) ; Žaloudík, Petr (referee) ; Stehlík, Petr (advisor)
Tato práce o energetickém využití čistírenských kalů obsahuje popis vlastností kalu (hustota, měrná tepelná kapacita a dynamická viskozita). Stěžejní kapitoly jsou věnovány desintegraci kalu pro zvýšení obsahu sušiny po odvodnění a experimentálnímu zkoumání tvorby emisí při spalování kalu, kde byl posuzován vliv přídavku alkálie. Spalování vysušeného kalu proběhlo ve fluidní vrstvě, byla zkoumána produkce škodlivin a distribuce těžkých kovů. Druhá ucelená část práce je věnována termochemické desintegraci stabilizovaného kalu, přičemž byl experimentálně vyhodnocován vliv na obsah vody v odvodněném kalu. Provedené experimenty sloužily k detekci vhodné teploty a dávky chemikálie. Výsledky experimentů byly rovněž podkladem pro ekonomickou bilanci, která je založena na úsporách za likvidaci menšího množství kalu.
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Methods for Determination of Characteristic Parameters of Combustion Processes on the Basis of Experiments and Modeling
Bělohradský, Petr ; Klemeš,, Jiří (referee) ; Žitný, Rudolf (referee) ; Stehlík, Petr (advisor)
The present thesis is concerned with methods for determination and modeling of characteristic parameters of combustion of gaseous fuels. The focus is stressed on formation of nitrogen oxides and heat transfer from hot flue gases into combustion chamber’s walls. Experimental work, which is focused on testing of two burners with suppressed formation of nitrogen oxides, is an important part of the thesis. Its aim is to obtain data that is necessary for further processing and modeling. The work presents two methods that may be used in modeling of characteristic combustion parameters, namely the method based on statistical processing of data and the method based on computational fluid dynamics. The approaches are applied to two devices (burner with two-staged fuel supply, burner with two-staged air supply) with the objective to analyze their parameters. First approach covers detailed planning of burner test prior to its own carrying out (definition of the goal of experiment, choice of input factors and response, experimental plan) and subsequent statistical processing of experimental data. On the contrary, CFD approach offers simulations as an alternative option to traditional experimental methods. The simulation of combustion includes building of computational grid, setup of boundary conditions, turbulence model, heat transfer model and chemical kinetics. Results of simulations are compared with experimental measured data.
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