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Grate Biomass Boiler
Dražka, Ondřej ; Křemínský, Pavel (referee) ; Lisý, Martin (advisor)
The aim of the thesis is a design of a grate steam boiler with capacity of 35 t/h and output steam parameters with temperature 430 °C and pressure 4,1 MPa. The first part of the thesis deals with stoichiometric calculations and boiler efficiency. The theses mainly focuses on the heat transfer calculation and the geometric design of individual heat transfer surfaces. The specifics of fuel are taken into consideration. The drawing of the basic boiler scheme is a part of the thesis.
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Design of steam boiler with grate firing burning contaminated wood
Král, Ondřej ; Křemínský, Pavel (referee) ; Baláš, Marek (advisor)
The master´s thesis deals with steam boiler design that burns contaminated wood with output 55 tons of steam per hour, steam pressure 4,2 MPa and temperature 423 °C. First two chapters focuses on stoichiometry and calculation of heat losses and boiler efficiency. Great part of thesis constitutes of thermal and dimensional calculations of every heat transfer surface. Some specific boiler parts are described considering special fuel properties. Final chapters contain pressure losses calculation of flue gas and heated medium for pumps and fans design. Drawing is also part of the work which is included as an attachment.
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Oxide scales damaging evaluation
Audyová, Markéta ; Vejvoda, Stanislav (referee) ; Lošák, Pavel (advisor)
This work is focused on oxide scale failure and characteristics created in high temperature – supercritical processes. The presence of high temperature corrosion in supercritical processes is minimalised by selection of the right material. For this work was selected material X10CrMoVNb9-1, where formulas of present oxidation scales are Fe2O3, Fe3O4 and FeCr2O4. Each oxidation scale has its own mechanical properties thus it is important to notice scale arrangement, thickness and geometry. Oxide scale mechanical properties, scale failure mechanisms and oxidation scale growth is evaluated in this work. Tension and pressure oxide scale failure are determined by critical values, which are mentioned in this work. Thanks to these values there was possibility to verify the authenticity of the finite element model. Oxidation scales created in heat exchangers are badly accessible thus it is difficult to observe them or remove them mechanically. Tube finite element model with oxidation scales was created in this work. There are simulations of scales on selected steel in supercritical conditions (pressure 24 MPa, temperature 500 °C). Simulation and analytic results are compared. Failure operative conditions are searched for scale FeCr2O4 until its compleate delamination and separation from metal. Aim of this work is to create an oxidation scale model with a possibility of futher use.
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High temperature corrosion behaviour of nicr-based coatings applied by twin wire arc spray technology
Lencová, K. ; Vostřák, M. ; Naďová, J. ; Lukáč, František ; Mušálek, Radek
High temperature corrosion is a serious problem related to the combustion of heavy oils with high vanadium contents. Protective overlay coatings are used to allow functioning of engineering components under extreme conditions and provide corrosion resistance to extend the component life. This article is concerned with the high temperature corrosion behaviour of two protective NiCr-based coatings and bare structural steel 1.4959 (W.nr.) in a molten salt environment of 40% Na2SO4 and 60% V2O5 at 750 °C under cyclic condition. NiCr and NiCrMoNbTa coating was deposited on steel 1.4903 (W.nr.) by Twin wire arc spray technology (TWAS). To establish the kinetics of corrosion, the thermogravimetric technique was used. The X-ray diffraction (XRD), scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS) techniques were used to analyse the corrosion products and determine the corrosion mechanism. The hot corrosion resistance of both coatings was better than bare steel samples. The NiCrMoNbTa coating showed better corrosion behaviour than the NiCr coating. However, also the NiCr coating provides sufficient protection to the substrate material.
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High temperature corrosion studies of HVOF sprayed coatings in molten sulphate salts environment
Lencová, K. ; Česánek, Z. ; Houdková, Š. ; Lukáč, František ; Mušálek, Radek
The generally applied requirements on lowering of emission production in the field of power industry have led, among others, into the application of low-emission combustion process of coal fired power plants. Besides the emissions reduction, this process has led to an increase of boilers parts corrosion degradation due to the reducing atmosphere in low-emission boilers, responsible for sulphide corrosion and molten salt attack. In such environment, the protection of the exposed surfaces gains importance. Among others, the thermal spraying technology can offer a suitable way of surface corrosion protection. In the present work, the high temperature corrosion behaviour of CoCrAlYTaCSi and Cr3C2-25%NiCr High Pressure/High Velocity Oxygen Fuel (HP/HVOF) sprayed coatings is evaluated and compared to the behaviour of bare structural steel (SPT360) substrate. The specimens were exposed to a molten salt environment, i. e., 12% Na2SO4 + 82% Fe2(SO4)3 at 690 °C under cyclic condition, simulating the working environment in low-emission boilers of coal-fired power plants. The thermogravimetric method was used to establish the kinetics of corrosion. X-ray diffraction (XRD), scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS) techniques were used to analyse the corrosion products and determine the corrosion mechanism. The thermogravimetric measurement shows high oxidation rate of SPT360 steel. Cr3C2-25%NiCr coating provides slightly better performance compared to CoCrAlYTaCSi coating. Based on the obtained results, both coatings were found to have higher corrosion resistance than the SPT360 steel substrate, offering a sufficient surface protection in a given environment.
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Grate Biomass Boiler
Dražka, Ondřej ; Křemínský, Pavel (referee) ; Lisý, Martin (advisor)
The aim of the thesis is a design of a grate steam boiler with capacity of 35 t/h and output steam parameters with temperature 430 °C and pressure 4,1 MPa. The first part of the thesis deals with stoichiometric calculations and boiler efficiency. The theses mainly focuses on the heat transfer calculation and the geometric design of individual heat transfer surfaces. The specifics of fuel are taken into consideration. The drawing of the basic boiler scheme is a part of the thesis.
|
|
|
Design of steam boiler with grate firing burning contaminated wood
Král, Ondřej ; Křemínský, Pavel (referee) ; Baláš, Marek (advisor)
The master´s thesis deals with steam boiler design that burns contaminated wood with output 55 tons of steam per hour, steam pressure 4,2 MPa and temperature 423 °C. First two chapters focuses on stoichiometry and calculation of heat losses and boiler efficiency. Great part of thesis constitutes of thermal and dimensional calculations of every heat transfer surface. Some specific boiler parts are described considering special fuel properties. Final chapters contain pressure losses calculation of flue gas and heated medium for pumps and fans design. Drawing is also part of the work which is included as an attachment.
|
|
|
Oxide scales damaging evaluation
Audyová, Markéta ; Vejvoda, Stanislav (referee) ; Lošák, Pavel (advisor)
This work is focused on oxide scale failure and characteristics created in high temperature – supercritical processes. The presence of high temperature corrosion in supercritical processes is minimalised by selection of the right material. For this work was selected material X10CrMoVNb9-1, where formulas of present oxidation scales are Fe2O3, Fe3O4 and FeCr2O4. Each oxidation scale has its own mechanical properties thus it is important to notice scale arrangement, thickness and geometry. Oxide scale mechanical properties, scale failure mechanisms and oxidation scale growth is evaluated in this work. Tension and pressure oxide scale failure are determined by critical values, which are mentioned in this work. Thanks to these values there was possibility to verify the authenticity of the finite element model. Oxidation scales created in heat exchangers are badly accessible thus it is difficult to observe them or remove them mechanically. Tube finite element model with oxidation scales was created in this work. There are simulations of scales on selected steel in supercritical conditions (pressure 24 MPa, temperature 500 °C). Simulation and analytic results are compared. Failure operative conditions are searched for scale FeCr2O4 until its compleate delamination and separation from metal. Aim of this work is to create an oxidation scale model with a possibility of futher use.
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