CFD study of penetration and mixing of fuel in a circulating fluidized bed furnace

The aim of this thesis is to study the mixing of fuel and, also to some extent, the mixing of air in a circulating fluidized bed boiler. In the literature survey part of this thesis, a review is made of the previous experimental studies related to the fuel and air mixing in the circulating fluidized beds. In the simulation part of it the commercial computational fluid dynamics software (FLUENT) is used with the Eulerian multiphase model for studying the fuel mixing in the two and three-dimensional furnace geometries. The results of the three-dimensional simulations are promising and, therefore suggestions are made for the future simulations. The two-dimensional studies give new information of the effects of the fluidization velocity, fuel particle size and fuel density on the fuel mixing. However, the present results show that three-dimensional models produce more realistic representation of the circulating fluidized bed behavior.

Development of Furnace Model for Bubbling Fluidized Bed Boiler

The aim of this thesis was to develop a model, which can predict heat transfer, heat release distribution and vertical temperature profile of gas phase in the furnace of a bubbling fluidized bed (BFB) boiler. The model is based on three separate model components that take care of heat transfer, heat release distribution and mass and energy balance calculations taking into account the boiler design and operating conditions. The model was successfully validated by solving the model parameters on the basis of commercial size BFB boiler test run information and by performing parametric studies with the model. Implementation of the developed model for the Foster Wheeler BFB design procedures will require model validation with existing BFB database and possibly more detailed measurements at the commercial size BFB boilers.

Aurora lucis evangelicae ante saeculum XII in Finlandia fuit exorta

Invocatio: I.N.J.C.

Dissertatio historica de vrbe Vloa, : cujus partem priorem, adprobante amplissima facultate philosophicae in regia ad Auram universitate, praeside ... Algotho A. Scarin, ... Publicae censurae, qua par est modestia, sistit Johannes Joh. Snellmann, scholae triv. Vloënsis collega superior. In auditorio superiori & maximo, ad diem XXVI. Martii, anni repar. salutis MDCCXXXVII. Horis ante meridiem solitis.

Dedicated to: Carl Cronstedt, Carl Gustaf Tessin, Theodor Ankarkrona, Otto Reinhold Wrangel, Olof Sandberg, Jacob von Hökerstedt, Carl von Groot, Carl Friedrich Piper, Olof von Törne, Petter Drufwa, Johan Löwen, Swen Cederström, Johan Maurits Klinkowström, Leonhard Klinkowström, Reinholdt Berndt Hauswolff, Christopher Christopherssen, Johan Williamsson, Olof Malmer, Johan Adam Petersson, Gustaf Kierman, Anders Plomgren.

Dissertatio academica, de Alandia, Maris Baltici insula, cujus partem posteriorem, consensu ampliss. facultatis philosoph. in Reg. Acad. Upsal. praeside ... mag. Petro Ekerman, ... Ad publicum examen, pro gradu, modeste defert alumnus regius, Christophorus Tärnström, Uplandus, ... In auditor. Carol. majori die XXVII. Nov. MDCCXLV. Horis ante meridiem solitis

Dedicated to: Jacobus Benzelius, Theodorus Ankarcrona, Matthias Grunerus, Olaus Thorin, Andreas Backman, Martinus Jonae Friberg, Carolus Gustavus Hallman, Andreas Sylvanus, Daniel P. Mansnerus, Daniel Lindqvist.

Dissertatio gradualis, de vrbe Vloa, : cujus partem posteriorem, ex indultu amplissimi senatus philosophici in regio [et] illustri, ad Auram, Athenaeo, praeside Henrico Hassel, ... In publico eruditorum consessu, bonis placidè examinandam modestè exhibet Johannes Joh. Snellmann, ... In auditorio maximo, ad diem XXII. Octobris, anno reparatae salutis MDCCXXXVII. Horis, ante meridiem, consuetis.

Dedicated to: Joachim Georg von Ganschav, Gustaf Fabricius, Simon Ruuth, Matthias Dan. Blohm, Barthold Frese, Henric Rungeen, Carl Fagerholm.

Specimen historicum, de Alandia, Maris Baltici insula, cujus partem priorem, consensu ampliss. facultatis philosoph. in Reg. Acad. Upsal. praeside ... mag. Elia Frondin, ... Publico examini submittit alumnus regius, Christophorus Tärnström, Uplandus, ... In auditor. Gustav. maj. ad diem I. Dec. MDCCXXXIX. Horis ante meridiem solitis

Dedicated to: Joanni Steuchio, Johanni Brauner, Stenoni Carolo Bielke, Maurits Wilhelm Nisbeth, Erico Klint, Gideoni Bille, Petro Bergdahl, Gudmundo Rothovio.

Dissertatio gradvalis de vrbe Torna, eique adjacentibvs paroeciis, : qvam ... sub praesidio ... Erici Alstrin ... placidae bonorum sistit disquisitioni Ericvs Brvnnivs, Er. fil. westro-botniensis. In audit. Gustav. majori ad diem 12. Junii anni MDCCXXXI. Horis ante meridiem solitis.

Dedicated to: Johannes Steuchius, Nicolaus Sternel.

Dissertatio historica de paroecia Alandiae Lemland, eique annexa Lumparland, cujus partem priorem ... : praeside mag. Johanne Bilmark, ... Publice examinandam proponit Daniel Ferdinandus Mallén, alumnus regius, Alandus, in auditorio majori die XXV Februarii anni R. S. MDCCXCII, horis ante meridiem consuetis.

Dedicated to: Isaacus Nordberg.

Modelling of combustion and sorbent reactions in three-dimensional flow environment of a circulating fluidized bed furnace

This thesis presents a three-dimensional, semi-empirical, steady state model for simulating the combustion, gasification, and formation of emissions in circulating fluidized bed (CFB) processes. In a large-scale CFB furnace, the local feeding of fuel, air, and other input materials, as well as the limited mixing rate of different reactants produce inhomogeneous process conditions. To simulate the real conditions, the furnace should be modelled three-dimensionally or the three-dimensional effects should be taken into account. The only available methods for simulating the large CFB furnaces three-dimensionally are semi-empirical models, which apply a relatively coarse calculation mesh and a combination of fundamental conservation equations, theoretical models and empirical correlations. The number of such models is extremely small. The main objective of this work was to achieve a model which can be applied to calculating industrial scale CFB boilers and which can simulate all the essential sub-phenomena: fluid dynamics, reactions, the attrition of particles, and heat transfer. The core of the work was to develop the model frame and the required sub-models for determining the combustion and sorbent reactions. The objective was reached, and the developed model was successfully used for studying various industrial scale CFB boilers combusting different types of fuel. The model for sorbent reactions, which includes the main reactions for calcitic limestones, was applied for studying the new possible phenomena occurring in the oxygen-fired combustion. The presented combustion and sorbent models and principles can be utilized in other model approaches as well, including other empirical and semi-empirical model approaches, and CFD based simulations. The main achievement is the overall model frame which can be utilized for the further development and testing of new sub-models and theories, and for concentrating the knowledge gathered from the experimental work carried out at bench scale, pilot scale and industrial scale apparatus, and from the computational work performed by other modelling methods.

Experimental and discrete element simulation studies of bell-less charging of blast furnace

This thesis presents an experimental study and numerical study, based on the discrete element method (DEM), of bell-less charging in the blast furnace. The numerical models are based on the microscopic interaction between the particles in the blast furnace charging process. The emphasis is put on model validation, investigating several phenomena in the charging process, and on finding factors that influence the results. The study considers and simulates size segregation in the hopper discharging process, particle flow and behavior on the chute, which is the key equipment in the charging system, using mono-size spherical particles, multi-size spheres and nonspherical particles. The behavior of the particles at the burden surface and pellet percolation into a coke layer is also studied. Small-scale experiments are used to validate the DEM models.

Model-based estimation of liquid flows in the blast furnace hearth and taphole

This thesis presents a set of methods and models for estimation of iron and slag flows in the blast furnace hearth and taphole. The main focus was put on predicting taphole flow patterns and estimating the effects of various taphole conditions on the drainage behavior of the blast furnace hearth. All models were based on a general understanding of the typical tap cycle of an industrial blast furnace. Some of the models were evaluated on short-term process data from the reference furnace. A computational fluid dynamics (CFD) model was built and applied to simulate the complicated hearth flows and thus to predict the regions of the hearth exerted to erosion under various operating conditions. Key boundary variables of the CFD model were provided by a simplified drainage model based on the first principles. By examining the evolutions of liquid outflow rates measured from the furnace studied, the drainage model was improved to include the effects of taphole diameter and length. The estimated slag delays showed good agreement with the observed ones. The liquid flows in the taphole were further studied using two different models and the results of both models indicated that it is more likely that separated flow of iron and slag occurs in the taphole when the liquid outflow rates are comparable during tapping. The drainage process was simulated with an integrated model based on an overall balance analysis: The high in-furnace overpressure can compensate for the resistances induced by the liquid flows in the hearth and through the taphole. Finally, a recently developed multiphase CFD model including interfacial forces between immiscible liquids was developed and both the actual iron-slag system and a water-oil system in laboratory scale were simulated. The model was demonstrated to be a useful tool for simulating hearth flows for gaining understanding of the complex phenomena in the drainage of the blast furnace.

Modeling of temperature regimes in a furnace of bubbling fluidized bed boiler

The work is mainly focused on the technology of bubbling fluidized bed combustion. Heat transfer and hydrodynamics of the process were examined in the work in detail. Special emphasis was placed on the process of heat exchange in a freeboard zone of bubbling fluidized bed boiler. Operating mode of bubbling fluidized bed boiler depends on many parameters. To assess the influence of some parameters on a temperature regime inside the furnace a simplified method of zonal modeling was used in the work. Thus, effects of bed material fineness, excess air ratio and changes in boiler load were studied. Besides the technology of combustion in bubbling fluidized bed, other common technologies of solid fuels combustion were reviewed. In addition, brief survey of most widely used types of solid fuel was performed in the work.

Three-dimensional modeling of biomass fuel flow in a circulating fluidized bed furnace

The reduction of greenhouse gas emissions in the European Union promotes the combustion of biomass rather than fossil fuels in energy production. Circulating fluidized bed (CFB) combustion offers a simple, flexible and efficient way to utilize untreated biomass in a large scale. CFB furnaces are modeled in order to understand their operation better and to help in the design of new furnaces. Therefore, physically accurate models are needed to describe the heavily coupled multiphase flow, reactions and heat transfer inside the furnace. This thesis presents a new model for the fuel flow inside the CFB furnace, which acknowledges the physical properties of the fuel and the multiphase flow phenomena inside the furnace. This model is applied with special interest in the firing of untreated biomass. An experimental method is utilized to characterize gas-fuel drag force relations. This characteristic drag force approach is developed into a gas-fuel drag force model suitable for irregular, non-spherical biomass particles and applied together with the new fuel flow model in the modeling of a large-scale CFB furnace. The model results are physically valid and achieve very good correspondence with the measurement results from large-scale CFB furnace firing biomass. With the methods and models presented in this work, the fuel flow field inside a circulating fluidized bed furnace can be modeled with better accuracy and more efficiently than in previous studies with a three-dimensional holistic model frame.