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Rotary drying and sintering kilns
Rafaj, Svatomír ; Hudák, Igor (referee) ; Skryja, Pavel (advisor)
This thesis deals with rotary drying and sintering kilns. The first part focused upon construction of the kilns, kiln processes and the options of technological arrangement of the kilns. The thesis second part presents two experiments. The first one is targeted to find the relation between residence time, kiln rotary speed and kiln slope in longitudinal direction. The examinations analysed individually the relation between kiln rotary speed and residence time and the relation between kiln slope and residence time. Finally, the regression equation describing the relation between holding time, kiln rotary speed and kiln rake was established. The results given by regression equation much closer to the real one then the results given by literature. The difference between real residence time and the regression one is about one minute. The second one is concerned with producing a set of equations with respect of mass and heat balance in case of drying process. The input material was wet crushed tetra packs. There were established technological conditions of the material, necessary burner energy input, heat losses and distribution of heat between material and flue gas. There were taken away almost 80 percent of heat energy by flue gases. The remaining 20 percent was divided between latent heat, material and heat losses through the shell of the rotary kiln.
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CFD modelling of granular flow in rotary kiln
Slowik, Roman ; Vondál, Jiří (referee) ; Juřena, Tomáš (advisor)
This work deals with modeling the flow of particulate matter in rotary kilns. For this purpose, a combined CFD and Discrete Element Method (DEM) model was used. Using Ansys Fluent software, several simulations were performed in order to determine the mean residence time and movement of the material in the rotary drum dryer. Results of the computational model were used to develop a regression model of the mean residence time and compared to the values as given by empirical equations. Furthermore, a simplified sensitivity analysis was performed for the selected input parameters of the model such as the stiffness constant, air mass flow rate and the particle size.
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Mathematical Modeling of Heat and Mass Transfer in a Rotary Kiln
Kozakovič, M. ; Havlica, Jaromír ; Huchet, F.
The main objective of this research was to compare the results of the proposed 1D transport model with numerical simulations of mass transport in a direct-heat rotary kiln at laboratory scale. Another objective was to investigate the effect of the number of flights on the formation of an active particle surface in the airborne phase, which enables efficient heat transport. The studied rotary kiln is a low-angle cylinder with a length of 0.5 meter and a diameter of 0.108 meter with regularly arranged flights on the inside. The heat is transported into the rotary kiln by hot air at the inlet. The load in the rotary kiln consists of spherical particles with 1 millimeter diameter. The rotary kiln rotation speed is 21.5 rpm. For each simulation, 20 rotations were performed. The Discrete Element Method implemented in an open-source code LIGGGHTS was used for simulations.Efficient heat transfer is made possible primarily by the large number of particles in the airborne phase, which are heated by the warm air blowing in. To begin with, the number of flights and their geometry were found to be a key parameter controlling the amount of particles in the gaseous regime. It was also found that an area in the right part of the base of the cylinder is formed which is not reached by particles from the flights. This phenomenon is due to the dynamics of particle transport, as the particles are not maintained in the active phase and move rapidly towards the load due to gravity. In conclusion, the effect of this zone is negative, as hot air flows through it without resistance, preventing the system from heating effectively.
Plný tet:  PDF
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Mathematical Modeling of Heat and Mass Transfer in a Rotary Kiln
Kozakovič, M. ; Čada, J. ; Kokavcová, A. ; Havlica, Jaromír ; Huchet, F.
The main objective of this research was to compare the results of the proposed 1D transport model with numerical simulations of mass transport in a direct-heat rotary kiln at laboratory scale. Another objective was to investigate the effect of the number of flights on the formation of an active particle surface in the airborne phase, which enables efficient heat transport. The studied rotary kiln is a low-angle cylinder with a length of 0.5 meter and a diameter of 0.108 meter with regularly arranged flights on the inside. The heat is transported into the rotary kiln by hot air at the inlet. The load in the rotary kiln consists of spherical particles with 1 millimeter diameter. The rotary kiln rotation speed is 21.5 rpm. For each simulation, 20 rotations were performed. The Discrete Element Method implemented in an open-source code LIGGGHTS was used for simulations.Efficient heat transfer is made possible primarily by the large number of particles in the airborne phase, which are heated by the warm air blowing in. To begin with, the number of flights and their geometry were found to be a key parameter controlling the amount of particles in the gaseous regime. It was also found that an area in the right part of the base of the cylinder is formed which is not reached by particles from the flights. This phenomenon is due to the dynamics of particle transport, as the particles are not maintained in the active phase and move rapidly towards the load due to gravity. In conclusion, the effect of this zone is negative, as hot air flows through it without resistance, preventing the system from heating effectively.
Plný tet: PDF
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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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CFD modelling of granular flow in rotary kiln
Slowik, Roman ; Vondál, Jiří (referee) ; Juřena, Tomáš (advisor)
This work deals with modeling the flow of particulate matter in rotary kilns. For this purpose, a combined CFD and Discrete Element Method (DEM) model was used. Using Ansys Fluent software, several simulations were performed in order to determine the mean residence time and movement of the material in the rotary drum dryer. Results of the computational model were used to develop a regression model of the mean residence time and compared to the values as given by empirical equations. Furthermore, a simplified sensitivity analysis was performed for the selected input parameters of the model such as the stiffness constant, air mass flow rate and the particle size.
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Rotary drying and sintering kilns
Rafaj, Svatomír ; Hudák, Igor (referee) ; Skryja, Pavel (advisor)
This thesis deals with rotary drying and sintering kilns. The first part focused upon construction of the kilns, kiln processes and the options of technological arrangement of the kilns. The thesis second part presents two experiments. The first one is targeted to find the relation between residence time, kiln rotary speed and kiln slope in longitudinal direction. The examinations analysed individually the relation between kiln rotary speed and residence time and the relation between kiln slope and residence time. Finally, the regression equation describing the relation between holding time, kiln rotary speed and kiln rake was established. The results given by regression equation much closer to the real one then the results given by literature. The difference between real residence time and the regression one is about one minute. The second one is concerned with producing a set of equations with respect of mass and heat balance in case of drying process. The input material was wet crushed tetra packs. There were established technological conditions of the material, necessary burner energy input, heat losses and distribution of heat between material and flue gas. There were taken away almost 80 percent of heat energy by flue gases. The remaining 20 percent was divided between latent heat, material and heat losses through the shell of the rotary kiln.
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