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Modelling of fouling and its influence on technical-economic characteristics of tubular heat transfer equipment in units for thermal processing of wastes
Keliš, Michal ; Kohoutek, Josef (referee) ; Jegla, Zdeněk (advisor)
The main subject of this study is the improvement of predicative ability of previously developed mathematical model for prediction of so-called “fouling critical velocity”. Attention is devoted especially to the flue gas side fouling process on active heat transfer surfaces in tubular heat exchange tube banks installed in waste incineration process plants and also a technical – economic analysis based on obtained results. The model improvement consists among others in taking into account another forces (electrostatic, capillary etc.) haven't yet been considered, which influence the mutual contact between flue gas particles in case of sedimentation fouling or the contact between particles and heat exchanger tube walls respectively. The improved model has therefore more predicative ability to the reality of fouling process. The results are used for technical – economic analysis, which determines an optimal heat exchanger design with respect to fouling. Furthermore, the algorithm of this analysis, essential fouling mechanisms, fouled heat exchanger surface cleaning methods as well as fundamental knowledge of fouling coefficient prediction are presented, whereas the emphasis is placed on industrial tubular heat exchange equipment installed in waste incineration process plants.
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Risk assessment design margin of process and power equipment
Horsák, Jan ; Pačíska, Tomáš (referee) ; Jegla, Zdeněk (advisor)
This work is devoted to description of methodology of determining process and power equipment design margins, which is based on assessment of a relative process importance of the equipment in question. The methodology is theoretically analysed, brought into context of common design practice and demonstrated on actual cases. Substantial part of this work analyses heat transfer in general as a base of heat exchanger design process.
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Optimization of the cleaning of the heating surfaces on the coal boiler K1 in Plzeňská teplárenská
Kostrhounová, Petra ; Tomáš, Zdeněk (referee) ; Baláš, Marek (advisor)
This master’s thesis deals with the assessment of cleaning of heat transfer surfaces of a coal-fired steam boiler. The first part is devoted to the description of the knowledge about the formation of deposits, the deposits influence on the operation of the plant and cleaning mechanisms. Then, basic information on the operation, design and method of removal of deposits of the K1 boiler is summarised. Based on this knowledge, operating data from four summer months of boiler operation are analysed to determine the fouling condition of the boiler surfaces and over fifty graphs are produced showing the evolution of selected operating values between each cleaning cycle of the convective and plate superheater as well as air preheater. Subsequently, a parametric model of the K1 boiler at 60 % output is created in PPSD, which allows a more detailed analysis of the boiler operating characteristics and is used for a more thorough interpretation of the operating data. In addition, two models for higher boiler outputs and three theoretical models of operating conditions with different levels of surface fouling were developed. To verify the accuracy of the developed model, a calculation of heat transfer through the outlet superheater is performed. Finally, the calculation of steam consumption for sootblowing is performed.
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CFD modelling of the initial phase of fouling inside convective section of a combustion facility
Zlámal, Filip ; Juřena, Tomáš (referee) ; Strouhal, Jiří (advisor)
The aim of this thesis was to create, based on the knowledge obtained from research, a CFD simulation of initial phase of fouling of solid particles during the combustion of solid fuels. The introduction of the work summarizes the mechanisms of fouling by solid particles. The introduction of the work summarizes the mechanisms of fouling by solid particles. Approaches to modelling the impact and deposition of particles are also described. A model is built, which is implemented in the ANSYS Fluent software with the addition of user-defined functions. The model is tested on a model of the convective part of an experimental device for burning solid fuels.
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Combustion of Solid Fuels in Rotary Kiln and Influence of their Composition on Emissions
Bojanovský, Jiří ; Jegla, Zdeněk (referee) ; Puchýř, Radim (referee) ; Máša, Vítězslav (advisor)
The work is focused on the study of the influence of solid fuel composition on the formation of pollutants during combustion in a rotary kiln. This is a highly topical issue related to the need to increase the share of alternative fuels as a substitute for fossil ones. The author builds on the research already carried out in this area, defines the basic characteristics of the problem under study and formulates hypotheses based on the summary of the current state of knowledge. The main hypothesis is ("The composition of the solid fuel mixture can be chosen in such a way as to reduce the generation of pollutants.") To verify this hypothesis, the author chooses experimental verification in combustion tests on a semi-operational experimental device. For the combustion tests, it was proposed to extend this equipment with apparatus that allows the evaluation of the fouling rate of heat transfer surfaces and the formation rate of particulate matter pollutants. This equipment was successfully used for combustion tests of 6 selected alternative fuels (refuse-derived fuel RDF, sewage sludge, and forest waste). Based on the combustion tests conducted with these sub-fuels, 6 fuel mixtures with high potential for industrial applications were defined. These mixtures were also burned in a rotary kiln. Based on the results obtained, the main hypothesis of the work was confirmed and the fuel mixture consisting of 70 wt.% forest waste, 20 wt.% RDF and 10 wt.% sewage sludge (MIX 6 in the work) was identified as the most suitable alternative to fossil fuels. This mixture did not show any operational problems and the best results were obtained in the formation of gaseous pollutants and particulate matter. The results of this work are a crucial point in the search for a methodology for the specification of suitable alternative fuel blends for combustion in the energy and manufacturing industries.
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Optimization of the cleaning of the heating surfaces on the coal boiler K1 in Plzeňská teplárenská
Kostrhounová, Petra ; Tomáš, Zdeněk (referee) ; Baláš, Marek (advisor)
This master’s thesis deals with the assessment of cleaning of heat transfer surfaces of a coal-fired steam boiler. The first part is devoted to the description of the knowledge about the formation of deposits, the deposits influence on the operation of the plant and cleaning mechanisms. Then, basic information on the operation, design and method of removal of deposits of the K1 boiler is summarised. Based on this knowledge, operating data from four summer months of boiler operation are analysed to determine the fouling condition of the boiler surfaces and over fifty graphs are produced showing the evolution of selected operating values between each cleaning cycle of the convective and plate superheater as well as air preheater. Subsequently, a parametric model of the K1 boiler at 60 % output is created in PPSD, which allows a more detailed analysis of the boiler operating characteristics and is used for a more thorough interpretation of the operating data. In addition, two models for higher boiler outputs and three theoretical models of operating conditions with different levels of surface fouling were developed. To verify the accuracy of the developed model, a calculation of heat transfer through the outlet superheater is performed. Finally, the calculation of steam consumption for sootblowing is performed.
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Effect of exchanger fouling and heat transfer coefficient
Konopiský, Karel ; Kracík, Petr (referee) ; Baláš, Marek (advisor)
This diploma thesis covers the influence of fouling in heat exchangers and heat transfer coefficient. In the first part of the thesis are covered the characteristics of fouling and its formation, process, and effects on heat transfer surfaces in exchangers. In the next part of the thesis, chemical analysis of cooling water is performed on an extracted sample and the potential of fouling is determined based on the analysis. In the conclusion part, computational models of fouling in the tube side of the heat exchanger are presented; fouling of an actual heat exchanger is calculated and compared with data captured during the operation of the heat exchanger.
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Application of Polymeric Hollow-Fiber Membranes in Air Filtration
Bulejko, Pavel ; Dohnal, Mirko (referee) ; Friess, Karel (referee) ; Svěrák, Tomáš (advisor)
Membrány z dutých vláken jsou široce využívány v aplikacích týkajících se úpravy kapalin jako např. při čištění odpadních vod, v membránových kontaktorech a bioreaktorech, membránové destilaci apod. I když jsou často využívány při separacích směsí plynů, je jejich použití pro mechanickou filtraci aerosolů velmi vzácné. Tato práce se zabývá filtrací vzduchu pomocí polypropylenových membrán z dutých vláken včetně jejich filtrační účinnosti, tlakových ztrát a také zanášením při dlouhodobé filtraci. Filtrační účinnost byla proměřena za použití různých aerosolů jako TiO2 a síran amonný. Tlakové ztráty byly měřeny při různých konfiguracích, tj. různé filtrační ploše a průměru vlákna membrány. Zanášení membrán bylo testováno použitím normovaného prachu definovaného normou ANSI/ASHRAE 52.2. Predikční modely pro filtrační účinnost a permeabilitu/tlakovou ztrátu membrány byly aplikovány na parametry membrán z dutých vláken a porovnány. Tyto membrány mají velikost pórů kolem 90 nm a poměrně nízkou porositu a tím vysoký potenciál pro separaci nanočástic ze vzduchu. Dále byla provedena analýza filtračního koláče a vyhodnocení energetických nároků a porovnány s teoretickými modely. V závěru práce je nastíněn odhad ceny životního cyklu při filtraci pomocí těchto membrán.
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The effect of boiler tube bundle fouling on its service life
Volná, Kateřina ; Ing. Zdeněk JŮZA, Ph.D., MBA (referee) ; Naď, Martin (advisor)
Fouling of tube bundles in boilers on the flue gas side affects not only the service life, but also the boiler heat output and increases maintenance and operating costs. Therefore, it is necessary to minimize or completely eliminate this process. This thesis focuses on comparison of the service life and the heat output of the tube bundles with and without deposit in the coal fired boiler. Simulations of flue gas flow in area of tube bundles with and without deposit are performed using ANSYS Fluent software, which shows that the surface of tube bundles with deposit is much less heated than the surface without deposit. The thermal loads of tubes obtained by the CFD analysis are applied to the model, which is created in the program ANSYS Mechanical, where the calculation of the temperature field in the cross section of the pipe is realized. The effect of fouling on creep life and heat output is then evaluated based on simulation results. The results show that fouling increases creep life, but significantly reduces heat output of heavily fouled tubes. Hence the flue gas flows at a higher temperature to the rest of the tube bundle, and the service life of those tubes will therefore probably decrease.
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Evaluating and modeling of fouling process in heat exchanger
Čirka, Martin ; Kilkovský, Bohuslav (referee) ; Jegla, Zdeněk (advisor)
This diploma thesis discusses fouling processes and mechanisms of industrial heat exchangers, with focus on shell side fouling of heat transfer area by flue gases, and eventually taking fouling into account, or more precisely its modeling and predicting by calculation. Thermal-hydraulic design of heat exchanger is focused mainly on shell side, as flue gases are dominant process medium in terms of fouling and heat transfer. Based on available operational data of evaluated industrial heat exchanger, specific process has been developed to determine by calculation, or more precisely predict change of fouling factor throughout operational period of heat exchanger. Usage and various options of this specific calculation technique are being discussed in conclusion, whether there is a potential to use this technique regarding more complex operational inputs or prediction of fouling process for different operational regime of heat exchanger.
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