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.

Maanpuolustustahto asevelvollisen koulutuksen ja palveluksen onnistumista selittävänä tekijänä

Lähtökohta tälle tutkimukselle oli havainto siitä, että varusmiehillä maanpuolustustahto ja taisteluluottamus korreloivat. Tämä huomio oli mahdollista tehdä aikaisemmissa varusmiesaineistoilla tehdyissä tutkimuksissa, joissa olin ollut mukana. Tutkimuksen aineistoina olivat useat puolustusvoimissa kerätyt varusmiesten kyselytutkimusaineistot. Vertailuaineistoina käytin reserviläisille kertausharjoituksissa tehtyjen kyselyiden aineistoja. Olennaista oli selvittää, säilyikö havaittu riippuvuus kun muita mahdollisia tekijöitä otettiin huomioon. Tutkimus oli aikaisemmin kerättyjen aineistojen sekundaarianalyysi ja tutkijana en ollut voinut vaikuttaa kyselyjen sisältöön tai käytettyjen muuttujien ja mittareiden valintaan. Aineistot on kerätty kuvaileviin tarkoituksiin ja tästä syystä tämä tutkimus oli tilastollisesti kuvaileva. Keskeiset käytetyt aineistot olivat varusmiesten kotiuttamiskyselyiden eli loppukyselyiden aineistot kaikista varuskunnista vuosilta 2000 – 2008 sekä vuonna 2010 Siilasmaan työryhmää varten kerätty aineisto kolmesta varuskunnasta. Vuoden 2010 varusmiestutkimus oli toteutettu siten, että kysely tehtiin sekä palveluksen alussa että lopussa. Tässä aineistossa käytettiin monipuolisesti varusmiesten psykososiaalisen toimintakyvyn erilaisia mittareita. Maanpuolustustahto on käsitteellisesti laaja kokonaisuus, kuitenkin tässä tutkimuksessa se oli operationalisoitava käytettävissä olleiden osioiden avulla. Maanpuolustustahtoa tarkasteltiin sekä henkilökohtaisena että yleisenä maanpuolustustahtona sekä niiden yhdistelmänä, josta käytettiin myös nimitystä maanpuolustusajattelu. Käsitteellisesti suppeampi taisteluluottamus operationalisoitiin siten, että muuttujana se kuvasi varusmiehen luottamusta aseisiinsa, saamaansa koulutukseen sekä lähiryhmäänsä. Taisteluluottamuksen mittaamisen taustalla oli ajatus siitä, että tämän yksilökohtaisen mittarin keskiarvo on joukon koulutuksen onnistuneisuuden estimaatti. Taisteluluottamus oli tutkimuksessa varsinainen tulosmuuttuja. Tulosten perusteella yksittäisten varusmiesten psykososiaalisessa toimintakyvyssä on eroja. Erityisesti erottui yksittäisenä tekijänä sosiaalisuus, joka summamuuttujana oli muodostettu varusmiestutkimus 2010:n aineistossa Maanpuolustuskorkeakoulun Käyttäytymistieteen laitoksen laatimista osioista. Sosiaalisuus ennusti voimakkaasti varusmiehen etenemistä koulutuksessa aina johtajakoulutukseen saakka. Sosiaalisuuden kontrollointi tilastollisesti ei poistanut maanpuolustusajattelun ja taisteluluottamuksen välistä riippuvuutta. Varusmiestutkimus 2010 aineistossa oli mahdollista tarkastella maanpuolustusajattelun muutosta palvelusaikana ja muutoksen yhteyttä psykososiaalisen toimintakyvyn kuvaajiin. Stressaantumistaipumus ja neuroottisuus olivat yhteydessä maanpuolustustahdon laskuun. Tunteiden hallinnan kyky tuki varusmiehen maanpuolustustahdon ja taisteluluottamuksen kehittymistä. Tilastollinen kuvaus toteutettiin Mplus-ohjelmistolla lasketulla rakenneyhtälömallilla. Aineistoon sopiva malli oli mahdollista löytää. Mallin mukaan sosiaalinen pääoman yksilökohtaisena resurssina antaa mahdollisuuden kehittää ja säilyttää maanpuolustusajattelua, joka on yhteydessä itseluottamuksen luontoiseen taisteluluottamukseen varusmieskoulutuksen päättyessä. Koulutuksen aikana joukkoon kehittynyt kiinteys ja luottamus tukevat tätä kehitystä. Joukkotuotantomallilla saadaan aikaan joukkoja, joissa taisteluluottamus on yleensä tarvittavalla tasolla ja niitä voidaan käyttää osoitettuihin tehtäviin. Kertausharjoitukset ylläpitävät kiinteyttä, taisteluluottamusta ja sitä kautta joukon suorituskykyä. Tutkimuksessa havaittiin myös, että pysyvissä miehistön ryhmissä, joissa ryhmänjohtaja ja/tai jäseniä ei vaihtunut, koulutuksen tulokset olivat parempia kuin muuttuneissa ryhmissä. Edelleen havaittiin, että 12 kuukautta palvelleiden miehistön jäsenten joukossa palvelusmotivaatio laski enemmän kuin muissa varusmiesryhmissä. Yhdestätoista koulutuksen ja tutkimuksen asiantuntijasta koottu ryhmä arvioi tutkimuksen tuloksia sovelletulla Q-menetelmällä Facilitate Pro -ohjelmistoa käyttäen. Menettely tuotti lisänäkökohtia tulosten arviointiin sekä niiden soveltamiseen.

Modelling of vegetative filter strips in catchment scale erosin control

Selostus: Valuma-aluetason mallisovellus suojakaistojen käytöstä eroosion torjunnassa

Objectives and motivations of small-scale forest owners : theoretical modelling and qualitative assessment

Abstract

A study of combustion phenomena in circulating fluidized beds by developing and applying experimental and modelling methods for laboratory-scale reactors

The results shown in this thesis are based on selected publications of the 2000s decade. The work was carried out in several national and EC funded public research projects and in close cooperation with industrial partners. The main objective of the thesis was to study and quantify the most important phenomena of circulating fluidized bed combustors by developing and applying proper experimental and modelling methods using laboratory scale equipments. An understanding of the phenomena plays an essential role in the development of combustion and emission performance, and the availability and controls of CFB boilers. Experimental procedures to study fuel combustion behaviour under CFB conditions are presented in the thesis. Steady state and dynamic measurements under well controlled conditions were carried out to produce the data needed for the development of high efficiency, utility scale CFB technology. The importance of combustion control and furnace dynamics is emphasized when CFB boilers are scaled up with a once through steam cycle. Qualitative information on fuel combustion characteristics was obtained directly by comparing flue gas oxygen responses during the impulse change experiments with fuel feed. A one-dimensional, time dependent model was developed to analyse the measurement data Emission formation was studied combined with fuel combustion behaviour. Correlations were developed for NO, N2O, CO and char loading, as a function of temperature and oxygen concentration in the bed area. An online method to characterize char loading under CFB conditions was developed and validated with the pilot scale CFB tests. Finally, a new method to control air and fuel feeds in CFB combustion was introduced. The method is based on models and an analysis of the fluctuation of the flue gas oxygen concentration. The effect of high oxygen concentrations on fuel combustion behaviour was also studied to evaluate the potential of CFB boilers to apply oxygenfiring technology to CCS. In future studies, it will be necessary to go through the whole scale up chain from laboratory phenomena devices through pilot scale test rigs to large scale, commercial boilers in order to validate the applicability and scalability of the, results. This thesis shows the chain between the laboratory scale phenomena test rig (bench scale) and the CFB process test rig (pilot). CFB technology has been scaled up successfully from an industrial scale to a utility scale during the last decade. The work shown in the thesis, for its part, has supported the development by producing new detailed information on combustion under CFB conditions.

Stand dynamics modelling approaches for multicohort management of eastern Canadian boreal forests

Abstract

Innovation Process Management and System Modelling

Työn tavoitteena oli perehtyä innovaatiojohtamisen ja järjestelmän soveltamiseen prosessiteollisuuden toimintaympäristöön. Kirjallisuuslähteitä apuna käyttäen perehdyttiin liiketoimintaympäristön innovaatiojohtamiselle asettamiin vaatimuksiin ja erilaisiin innovaatiojärjestelmiin. Olennaisena osana innovaatiojohtamiseen liittyy sidosryhmien tarpeiden ja niiden tarjoamien resurssien huomioiminen toiminnassa. Myöskin tuotekehityksen menetelmät ja työkalut ovat omalta osaltaan merkittävässä asemassa toiminnan tehokkuutta arvioitaessa. Innovaatiojärjestelmä tulee sopeuttaa yrityksen toimintoihin ja sen erityispiirteet huomioonottaen siten, että toiminnan johtaminen prosessina tuo yritykselle ja sen sidosryhmille lisäarvoa. Innovaatiojärjestelmän luominen yritykselle on ainayksilöllinen prosessi ja siihen ei ole olemassa yleispätevää menetelmää, joka voitaisiin ottaa käyttöön sellaisenaan. Yritys, jonka liiketoiminta keskittyy kuitupohjaisten pakkausmateriaalien valmistamiseen, joutuu täyttämään toiminnassaan materiaalintoimittajien, omien tuotantoprosessiensa ja asiakkaiden sekä jopa loppukäyttäjien uusille tuotteille luomat odotukset. Innovaatiojohtamista sävyttää toiminnan tulosten suuri epävarmuus ja sen vaativien aineellisten ja henkisten resurssien mittavuus. Innovaatiotoiminnan johtaminen prosessina, käyttäen hyväksi järjestelmämallia, tavoittelee systemaattista ja asetettujen kriteerien täyttämää lähestymistapaa tuotekehityksen ja uusien liiketoimintainnovaatioiden alueella. Kehitetyn mallin tulee palvella monimutkaista liiketoimintaympäristöä, jokatoisaalta perustuu tehokkaaseen massatuotantoon ja toisaalta pyrkii erilaistumaan palvelemalla sekä huomioimalla asiakkaidensa tuotteille asettamat vaatimukset.

Demographic Modelling of Human Population Growth

This work presents models and methods that have been used in producing forecasts of population growth. The work is intended to emphasize the reliability bounds of the model forecasts. Leslie model and various versions of logistic population models are presented. References to literature and several studies are given. A lot of relevant methodology has been developed in biological sciences. The Leslie modelling approach involves the use of current trends in mortality,fertility, migration and emigration. The model treats population divided in age groups and the model is given as a recursive system. Other group of models is based on straightforward extrapolation of census data. Trajectories of simple exponential growth function and logistic models are used to produce the forecast. The work presents the basics of Leslie type modelling and the logistic models, including multi- parameter logistic functions. The latter model is also analysed from model reliability point of view. Bayesian approach and MCMC method are used to create error bounds of the model predictions.

Effect of hydrodynamics on modelling, monitoring and control of crystallization

Crystallization is a purification method used to obtain crystalline product of a certain crystal size. It is one of the oldest industrial unit processes and commonly used in modern industry due to its good purification capability from rather impure solutions with reasonably low energy consumption. However, the process is extremely challenging to model and control because it involves inhomogeneous mixing and many simultaneous phenomena such as nucleation, crystal growth and agglomeration. All these phenomena are dependent on supersaturation, i.e. the difference between actual liquid phase concentration and solubility. Homogeneous mass and heat transfer in the crystallizer would greatly simplify modelling and control of crystallization processes, such conditions are, however, not the reality, especially in industrial scale processes. Consequently, the hydrodynamics of crystallizers, i.e. the combination of mixing, feed and product removal flows, and recycling of the suspension, needs to be thoroughly investigated. Understanding of hydrodynamics is important in crystallization, especially inlargerscale equipment where uniform flow conditions are difficult to attain. It is also important to understand different size scales of mixing; micro-, meso- and macromixing. Fast processes, like nucleation and chemical reactions, are typically highly dependent on micro- and mesomixing but macromixing, which equalizes the concentrations of all the species within the entire crystallizer, cannot be disregarded. This study investigates the influence of hydrodynamics on crystallization processes. Modelling of crystallizers with the mixed suspension mixed product removal (MSMPR) theory (ideal mixing), computational fluid dynamics (CFD), and a compartmental multiblock model is compared. The importance of proper verification of CFD and multiblock models is demonstrated. In addition, the influence of different hydrodynamic conditions on reactive crystallization process control is studied. Finally, the effect of extreme local supersaturation is studied using power ultrasound to initiate nucleation. The present work shows that mixing and chemical feeding conditions clearly affect induction time and cluster formation, nucleation, growth kinetics, and agglomeration. Consequently, the properties of crystalline end products, e.g. crystal size and crystal habit, can be influenced by management of mixing and feeding conditions. Impurities may have varying impacts on crystallization processes. As an example, manganese ions were shown to replace magnesium ions in the crystal lattice of magnesium sulphate heptahydrate, increasing the crystal growth rate significantly, whereas sodium ions showed no interaction at all. Modelling of continuous crystallization based on MSMPR theory showed that the model is feasible in a small laboratoryscale crystallizer, whereas in larger pilot- and industrial-scale crystallizers hydrodynamic effects should be taken into account. For that reason, CFD and multiblock modelling are shown to be effective tools for modelling crystallization with inhomogeneous mixing. The present work shows also that selection of the measurement point, or points in the case of multiprobe systems, is crucial when process analytical technology (PAT) is used to control larger scale crystallization. The thesis concludes by describing how control of local supersaturation by highly localized ultrasound was successfully applied to induce nucleation and to control polymorphism in reactive crystallization of L-glutamic acid.

Socially Competent Leadership - predictors, impacts and skilling in engineering

Earlier management studies have found a relationship between managerial qualities and subordinate impacts, but the effect of managers‘ social competence on leader perceptions has not been solidly established. To fill the related research gap, the present work embarks on a quantitative empirical effort to identify predictors of successful leadership. In particular, this study investigates relationships between perceived leader behavior and three selfreport instruments used to measure managerial capability: 1) the WOPI Work Personality Inventory, 2) Raven‘s general intelligence scale, and 3) the Emotive Communication Scale (ECS). This work complements previous research by resorting to both self-reports and other-reports: the results acquired from the managerial sample are compared to subordinate perceptions as measured through the ECS other-report and the WOPI360 multi-source appraisal. The quantitative research is comprised of a sample of 8o superiors and 354 subordinates operating in eight Finnish organizations. The strongest predictive value emerged from the ECS self- and other-reports and certain personality dimensions. In contrast, supervisors‘ logical intelligence did not correlate with leadership perceived as socially competent by subordinates. 16 of the superiors rated as most socially competent by their subordinates were selected for case analysis. Their qualitative narratives evidence the role of life history and post-traumatic growth in developing managerial skills. The results contribute to leadership theory in four ways. First, the ECS self-report devised for this research offers a reliable scale for predicting socially competent leader ability. Second, the work identifies dimensions of personality and emotive skills that can be considered predictors of managerial ability and benefited from in leader recruitment and career planning. Third, the Emotive Communication Model delineated on the basis of the empirical data allows for a systematic design and planning of communication and leadership education. Fourth, this workfurthers understanding of personal growth strategies and the role of life history in leader development and training. Finally, this research advances educational leadership by conceptualizing and operationalizing effective managerial communications. The Emotive Communication Model devised directs the pedagogic attention in engineering to assertion, emotional availability and inspiration skills. The proposed methodology addresses classroom management strategies drawing from problem-based learning, student empowerment, collaborative learning, and so-called socially competent teachership founded on teacher immediacy and perceived caring, all constituting strategies moving away from student compliance and teacher modelling. The ultimate educational objective embraces the development of individual engineers and organizational leaders that not only possess traditional analytical and technical expertise and substantive knowledge but are intelligent also creatively, practically, and socially.

Loss Modelling of Three-Level Inverters controlled with Space Vector Modulation Technique

The objective of this master’s thesis is to investigate the loss behavior of three-level ANPC inverter and compare it with conventional NPC inverter. The both inverters are controlled with mature space vector modulation strategy. In order to provide the comparison both accurate and detailed enough NPC and ANPC simulation models should be obtained. The similar control model of SVM is utilized for both NPC and ANPC inverter models. The principles of control algorithms, the structure and description of models are clarified. The power loss calculation model is based on practical calculation approaches with certain assumptions. The comparison between NPC and ANPC topologies is presented based on results obtained for each semiconductor device, their switching and conduction losses and efficiency of the inverters. Alternative switching states of ANPC topology allow distributing losses among the switches more evenly, than in NPC inverter. Obviously, the losses of a switching device depend on its position in the topology. Losses distribution among the components in ANPC topology allows reducing the stress on certain switches, thus losses are equally distributed among the semiconductors, however the efficiency of the inverters is the same. As a new contribution to earlier studies, the obtained models of SVM control, NPC and ANPC inverters have been built. Thus, this thesis can be used in further more complicated modelling of full-power converters for modern multi-megawatt wind energy conversion systems.

Simulation methods in the modelling of bioaffinity assays

Computational model-based simulation methods were developed for the modelling of bioaffinity assays. Bioaffinity-based methods are widely used to quantify a biological substance in biological research, development and in routine clinical in vitro diagnostics. Bioaffinity assays are based on the high affinity and structural specificity between the binding biomolecules. The simulation methods developed are based on the mechanistic assay model, which relies on the chemical reaction kinetics and describes the forming of a bound component as a function of time from the initial binding interaction. The simulation methods were focused on studying the behaviour and the reliability of bioaffinity assay and the possibilities the modelling methods of binding reaction kinetics provide, such as predicting assay results even before the binding reaction has reached equilibrium. For example, a rapid quantitative result from a clinical bioaffinity assay sample can be very significant, e.g. even the smallest elevation of a heart muscle marker reveals a cardiac injury. The simulation methods were used to identify critical error factors in rapid bioaffinity assays. A new kinetic calibration method was developed to calibrate a measurement system by kinetic measurement data utilizing only one standard concentration. A nodebased method was developed to model multi-component binding reactions, which have been a challenge to traditional numerical methods. The node-method was also used to model protein adsorption as an example of nonspecific binding of biomolecules. These methods have been compared with the experimental data from practice and can be utilized in in vitro diagnostics, drug discovery and in medical imaging.