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Foaming of fermentation residues during a vacuum evaporation
Knob, Jan ; Brummer, Vladimír (referee) ; Vondra, Marek (advisor)
The diploma thesis deals with the processing of digestate, which is the remaining material after biogas production. It aims to experimentally prove how chosen operational parameters of antifoaming agents influence digestate foaming associated with the vacuum evaporating technology. Based on the research of available antifoamers and the issue of digestate foaming itself, it was observed how three selected antifoamers (i.e. rapeseed oil, silicone antifoamer Erbslöh Schaum-ex and oleic acid), together with the decrease in the pH factor of the evaporating digestate, influence the final foam production. For the purposes of the research, an apparatus simulating the vacuum evaporating process was set up in which the heated sample was brought to boil by gradual pressure decrease. The process of foaming was observed in a transparent cylinder of a testing culumn. The essential part of the experimental activity is represented by a planned experiment which by means of a DoE (Design of experiments) method proved rapeseed oil to be very efficient. In contrast, other antifoamers, as well as the influence of the pH factor decrease, manifested themselves as insignificant factors, while the oleic acid even supported the foaming. The supplementary measurements led to a more detailed research of the effects of rapeseed oil and to the construction of a mathematical model describing how the concentration of rapeseed oil undermines the amount of generated foam. The main contribution of the thesis is firstly the evidence that rapeseed oil plays an important part in the reduction process of digestate foaming and secondly the determination of minimum substance concentration leading to the foaming reduction of a particular sample which is considered efficient enough to enable functioning of a vacuum evaporator. The thesis has also experimentally demonstrated the influence of some polymer organic flocculants which have been proved to support the foaming.
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MODERN TECHNOLOGIES IN WIRE ELECTRICAL DISCHARGE MACHINING THE METAL ALLOYS
Mouralová, Kateřina ; Karpíšek, Zdeněk (referee) ; Pokorný, Peter (referee) ; Píška, Miroslav (advisor)
The dissertation is focused on streamlining production on wire electric discharge machine during cutting metal alloys, specifically low-alloy steel quality by CSN 41 4220. The first part contains a study of the current and modern technologies EDM wire cutting. The second part is focused on identifying key parameters to influence the WEDM process, a detailed analysis of the machined surfaces of samples and wire electrodes used for cutting. The result of this work was to explore the possibility, whether by performing planned experiment and subsequent evaluation in the future to determine exactly setting the key parameters influencing the process of WEDM.
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Optimization of poly(3-hydroxybutyrate) based biocomposite with respect to its printability and mechanical properties
Chaloupková, Kateřina ; Obruča, Stanislav (referee) ; Přikryl, Radek (advisor)
The presented theses deals with preparation and optimalization of biocompatible material based on poly(3-hydroxybutyrate). Other components of prepared samples are polylactid acid, hydroxyapatite and commercially available plasticizer Syncroflex3114. These components were chosen based on their biocompatibility and properties that can be possibly used in tissue engineering. Theoretical part of this theses contains general overview of bone tissue and review of materials used in bone tissue regeneration. Part of this thesis also deals with the problematics of scaffolds. Aim of the experimental part is a planned experiment, which is used to optimize the mixture with respect to printability and mechanical properties. The first step is the preparation of samples based on the proposed conditions and their subsequent processing into a filament with an exact diameter of 1,75 mm for 3D printing using the fused deposition modeling method. From the prepared filaments, test specimens were printed for the following experiments: temperature tower, warping coefficient measurement, bending and pressure test. Data from these experiments were processed using a mathematical model in the form of graphs and equations which show the effect of material components on the measured quantity. It was found that the amount of plasticizer in the sample affects the properties the most. This effect is negative in all cases and worsens the properties of the material. The result of the planned experiment is also a mixture optimized for the best possible printability and mechanical properties (bending modulus 3,3 GPa and pressure modulus 2,3 GPa). With regard to the potential application of the material in bone tissue engineering, the first accelerated biodegradation screening tests were performed for selected samples. The results of accelerated degradation tests are ambiguous and further optimization is needed. Simultaneously with the diploma thesis, biological testing of scaffolds printed on a 3D printer from prepared samples took place. All tested samples were found to be biocompatible.
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Design of Experiment
Holec, Tomáš ; Popela, Pavel (referee) ; Bednář, Josef (advisor)
In this thesis, the design of experiment is studied. Firstly, a theoretic background in mathematical statistics necessary for understanding is built (chapter 2). The design of experiment is then presented in chapters 3 and 4. Chapter 3 is divided into several subchapters in which its brief history is provided as well as its complex theoretic description (basic principles, steps for planning, etc.). Chapter 4 deals with particular types of the design of experiment (Factorial experiments or Response surface design). Simple examples are provided to illustrate the theory in chapters 3 and 4. Last part of the thesis is strictly practical and focuses on an application of the theory for particular data sets and its evaluation (chapter 5).
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THEORETICAL PROPERTIES AND APPLICATIONS OF ADVANCED DESIGNS OF EXPERIMENT
Hrabec, Pavel ; Hlávka,, Zdeněk (referee) ; Kraus, David (referee) ; Bednář, Josef (advisor)
The methodology of the design of experimnet has become an integral part of the optimisation of manufacturing processes in recent decades. Problems regarding designs of experiments are still up to date, especially because of a variety of approaches to collecting and evaluating data. Scientists in different research and development areas often do not take into account possible shortcommings or even essential assumptions of selected design and/or its evaluation methods. This disertation thesis summarizes theoretical bases of selected designs of experiments. Describes several applications of central composite design on responses regarding wire electrical discharge machining process. And compares different designs of experiment for response surfaces of five parameters with regards to algoritmic selection of statistically signifficant parameters.
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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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Vacuum evaporation efficiency improvement
Havlásek, Martin ; Máša, Vítězslav (referee) ; Vondra, Marek (advisor)
This thesis is focused on experimental work in the domain of vacuum evaporation efficiency improvement. The first part introduces theory of liquids evaporation and its influencing factors, then multi-stage flash distillation technology. The next part of theory is an overview of other technologies used for desalination of sea water and introduction to the design of experiments. In the practical part are selected factors affecting efficiency of device and experiment plan is designed for them. When the experiment is done, optimal operating conditions of technology are designed on basis of analysis.
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Inner geometry optimization of flat-panel photobioreactor
Hlaváč, Ivan ; Babička Fialová, Dominika (referee) ; Rebej, Miroslav (advisor)
This master thesis focus on optimatization of flat-panel photobioreactor. The optimatization was performed using CFD models and Design of experiement. The CFD model used for the optimatizaion was before performing the experiment validated with real experiment data. Hydrodynamic parameters affecting microalgae yield were monitored during CFD calculations. They were: gas holdup, gas velocity, turbulent kinetic energy, dead zone ratio. interfacial area and shear stress.The photobioreactor with a stirrer and with vertical baffles, which were selected based on research, were compared. The higher values of hydrodynamic parameters were reached with a stirrer. Baffels were evaluated as more suitable for microalgae, which are more sensitive to shear stress.
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Methods for liquid-gas separation
Matoušek, Jakub ; Touš, Michal (referee) ; Vondra, Marek (advisor)
This diploma thesis is devoted to the separation of liquid from gas. Functional principles and methods for the separation of droplets from the gas phase stream are presented in the introductory part. The research also lists the types of separators and mist eliminators, including their advantages and disadvantages. Cyclone separators are described in detail in the thesis in terms of the separation principle, design and factors influencing the efficiency of separation. The experimental activity took place on salt water and dealt with finding the optimal operating conditions for a cyclone with a given geometry using the method of Design of experiments (DOE). The vapor-liquid mixture generated in the evaporator entered the cyclone and the effect of salt concentration and inlet flow rate on the separation efficiency and pressure drop of the cyclone was investigated. Experimentally, the highest efficiency of 97.22% was achieved at a flow rate of 8.59 kg/h and with a salinity of water supplied to the evaporator of 14,246 µS/cm. The quality of the distilled water was therefore 5 µS/cm. Without the inclusion of a cyclone, the conductivity of the condensed steam would correspond to 175.31 µS/cm. In the final part, a proposal for modifications of the tested equipment was presented to improve the separation efficiency within the evaporator technology.
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