The optimal estimation theory of the Wiener-Kalman filter is extended to cover the situation in which the number of memory elements in the estimator is restricted. A method, based on the simultaneous diagonalisation of two symmetric positive definite matrices, is given which allows the weighted least square estimation error to be minimised. A control system design method is developed utilising this estimator, and this allows the dynamic controller in the feedback path to have a low order. A 12-order once-through boiler model is constructed and the performance of controllers of various orders generated by the design method is investigated. Little cost penalty is found even for the one-order controller when compared with the optimal Kalman filter system. Whereas in the Kalman filter all information from past observations is stored, the given method results in an estimate of the state variables which is a weighted sum of the selected information held in the storage elements. For the once-through boiler these weighting coefficients are found to be smooth functions of position, their form illustrating the implicit model reduction properties of the design method. Minimal-order estimators of the Luenberger type also generate low order controllers and the relation between the two design methods is examined. It is concluded that the design method developed in this thesis gives better plant estimates than the Luenberger system and, more fundamentally, allows a lower order control system to be constructed. Finally some possible extensions of the theory are indicated. An immediate application is to multivariable control systems, while the existence of a plant state estimate even in control systems of very low order allows a certain adaptive structure to be considered for systems with time-varying parameters.

In Sweden, there are about 0.5 million single-family houses that are heated by electricity alone, and rising electricity costs force the conversion to other heating sources such as heat pumps and wood pellet heating systems. Pellet heating systems for single-family houses are currently a strongly growing market. Future lack of wood fuels is possible even in Sweden, and combining wood pellet heating with solar heating will help to save the bio-fuel resources. The objectives of this thesis are to investigate how the electrically heated single-family houses can be converted to pellet and solar heating systems, and how the annual efficiency and solar gains can be increased in such systems. The possible reduction of CO-emissions by combining pellet heating with solar heating has also been investigated. Systems with pellet stoves (both with and without a water jacket), pellet boilers and solar heating have been simulated. Different system concepts have been compared in order to investigate the most promising solutions. Modifications in system design and control strategies have been carried out in order to increase the system efficiency and the solar gains. Possibilities for increasing the solar gains have been limited to investigation of DHW-units for hot water production and the use of hot water for heating of dishwashers and washing machines via a heat exchanger instead of electricity (heat-fed appliances). Computer models of pellet stoves, boilers, DHW-units and heat-fed appliances have been developed and the parameters for the models have been identified from measurements on real components. The conformity between the models and the measurements has been checked. The systems with wood pellet stoves have been simulated in three different multi-zone buildings, simulated in detail with heat distribution through door openings between the zones. For the other simulations, either a single-zone house model or a load file has been used. Simulations were carried out for Stockholm, Sweden, but for the simulations with heat-fed machines also for Miami, USA. The foremost result of this thesis is the increased understanding of the dynamic operation of combined pellet and solar heating systems for single-family houses. The results show that electricity savings and annual system efficiency is strongly affected by the system design and the control strategy. Large reductions in pellet consumption are possible by combining pellet boilers with solar heating (a reduction larger than the solar gains if the system is properly designed). In addition, large reductions in carbon monoxide emissions are possible. To achieve these reductions it is required that the hot water production and the connection of the radiator circuit is moved to a well insulated, solar heated buffer store so that the boiler can be turned off during the periods when the solar collectors cover the heating demand. The amount of electricity replaced using systems with pellet stoves is very dependant on the house plan, the system design, if internal doors are open or closed and the comfort requirements. Proper system design and control strategies are crucial to obtain high electricity savings and high comfort with pellet stove systems. The investigated technologies for increasing the solar gains (DHW-units and heat-fed appliances) significantly increase the solar gains, but for the heat-fed appliances the market introduction is difficult due to the limited financial savings and the need for a new heat distribution system. The applications closest to market introduction could be for communal laundries and for use in sunny climates where the dominating part of the heat can be covered by solar heating. The DHW-unit is economical but competes with the internal finned-tube heat exchanger which is the totally dominating technology for hot water preparation in solar combisystems for single-family houses. / <p>QC 20100916</p>

O avanço da capacidade do processamento dos computadores e do desenvolvimento de métodos numéricos tem proporcionado ferramentas de modelagem, projeto e otimização cada vez mais eficientes para a constante melhoria de caldeiras de recuperação química Kraft. Dentre as técnicas utilizadas, os modelos CFD abrangentes tem sido empregados nos últimos anos para representar a operação da caldeira de recuperação considerando o maior número possível processos vinculados ao escoamento dos gases de combustão. O presente trabalho busca desenvolver um modelo CFD abrangente considerando o escoamento turbulento dos gases de combustão, o arraste das gotas de licor, a combustão homogênea dos voláteis em fase gasosa, as etapas de combustão heterogênea do licor preto e uma representação simplificada do leito carbonizado. Os resultados se mostraram coerentes com o comportamento apresentado na literatura. A simulação do modelo permite análise dos projetos e das operações da caldeira. / The advance of computer processing power and the development of numerical methods promote more efficient tools for modeling, design and optimization aiming to increase improvements in Kraft recovery boilers. Among the available techniques, the comprehensive CFD models have been applied in the last years to represent the recovery boiler operation considering as much as possible processes linked with flue gas flow. The objective of present work is the development of a comprehensive CFD model considering turbulent flue gas flow, black liquor droplets drag, volatiles homogeneous combustion in gas phase, the steps of heterogeneous black liquor combustion and the simplified interaction between flue gas flow and char bed. The results have good agreement with boiler behavior presented in the literature. The simulation of the comprehensive model allows the analysis of design and operations of the boiler.

Submitted by Andrea Pereira (andrea.pereira@unipampa.edu.br) on 2017-04-10T17:48:36Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Dissertação_Rodrigo_Final_Impressão.pdf: 2591713 bytes, checksum: 3d6be77e2f47aca595d592660db94e02 (MD5) / Approved for entry into archive by Andrea Pereira (andrea.pereira@unipampa.edu.br) on 2017-04-10T17:48:55Z (GMT) No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Dissertação_Rodrigo_Final_Impressão.pdf: 2591713 bytes, checksum: 3d6be77e2f47aca595d592660db94e02 (MD5) / Made available in DSpace on 2017-04-10T17:48:55Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Dissertação_Rodrigo_Final_Impressão.pdf: 2591713 bytes, checksum: 3d6be77e2f47aca595d592660db94e02 (MD5) Previous issue date: 2015-08-21 / Esta pesquisa estudou o desgaste por erosão atuante nos tubos de troca térmica do economizador de uma caldeira por meio de testes in loco, testes em laboratório seguindo os padrões da norma (ASTM G76-95) e simulações computacionais. Durante as análises, foram avaliados os comportamentos das ligas de aço como: ASTM A213T2, ASTM A213T22, ASTM A213T91, ASTM A210C e ASTM A106B, em função das variáveis velocidades, concentração, composição da cinza volante, temperatura e erosão quando expostos às mesmas condições operacionais. Esta investigação objetivou fornecer subsídios às premissas de projeto e seleção de materiais, bem como aumentar o tempo de vida útil dos componentes quando submetidos a condições adversas na caldeira em função das variáveis observadas. O controle da erosão e desgaste dos tubos tem como propósito a contribuição para a redução dos custos de manutenção, verificando-se falhas nos tubos do economizador prematuras, que causam indisponibilidades forçadas da caldeira o que gera prejuízos de grande vulto. Utilizou-se difração de raio x para análise de composição mineralógica das cinzas volantes. Para auxiliar na escolha da região de estudo, foram realizados cálculos de simulação CFD com o propósito de verificar o local exato onde a ação da velocidade dos gases de exaustão mais prejudicam os dutos no interior do economizador da caldeira. A avaliação da erosão por cinza volante, oriunda da Caldeira 4, do Complexo Termelétrico de Candiota, ocorreu em duas etapas distintas. A primeira foi realizada em condições de processo e, a segunda, em testes de bancada. Os testes em condições de processo foram acompanhados por ensaios para avaliar a evolução do desgaste das ligas de aço, como, pesagem, medição de espessura por ultrassom, digitalização em scanner 3D e dureza. O teste de bancada utilizou, como referência, a norma ASTM G76-95, fornecendo parâmetros para a confecção das amostras, assim como a própria bancada de testes. Os ensaios foram fundamentais para quantificar os resultados, como, pesagem e digitalização em scanner 3D. Os resultados encontrados por meio deste estudo possibilitaram um maior conhecimento dos mecanismos de erosão nas ligas de aço com o uso das cinzas volantes. Dessa forma, foi possível encontrar soluções para melhorar as premissas de projeto, assim como identificar os limites de aplicação dos materiais estudados em um projeto dessa natureza. / This research studied the erosion mechanism active in heat exchange tubes of a boiler by means of in site tests, laboratory tests following the standard (ASTM G76-95) and computer simulations. During the analysis, we evaluated the behavior of alloy steel such as: ASTM A213T2, ASTM A213T22, ASTM A213T91, ASTM A210C and ASTM A106B, in function on the variable speed, concentration, fly ash composition, temperature and erosion when exposed to the same conditions operational. This objective investigation to provide inputs on design assumptions and material selection, and increase the service life of components when subjected to adverse conditions in the boiler depending on the observed variables. Control of erosion and wear of the tubes are intended to contribute to the reduction of maintenance costs, checking for failures in premature economizer tubes, causing forced outages boiler which generates large-scale losses. It was used x ray diffraction for the analysis of mineralogical composition of fly ash. To auxiliary in choose the region the study, were performed CFD simulation studies with the purpose the verify the exact place where the action of the velocity of the exhaust gases more prejudice the ducts inside the boiler economizer. The assessment of erosion by fly ash, coming from the boiler 4, the Thermoelectric Complex Candiota, occurred in two distinct stages. The first was realized in process conditions and, the second in bench tests. The tests in process conditions were followed tests to assess the evolution of wear of alloy steel, as, weighing, measuring thickness by ultrasound, 3D scanner and hardness. The test bench utilize as a reference to ASTM G76-95, providing parameters for confection the samples, as well as own bench tests. The tests were fundamental to quantify the results, as, weighing and scanning 3D. The results found by means of this study allowed a more knowledge of erosion mechanisms in alloy steel with the use of fly ash. In this way, it is possible to find solutions to improve the design assumptions, as identify the application limits of the materials studied in a project of this nature.

O avanço da capacidade do processamento dos computadores e do desenvolvimento de métodos numéricos tem proporcionado ferramentas de modelagem, projeto e otimização cada vez mais eficientes para a constante melhoria de caldeiras de recuperação química Kraft. Dentre as técnicas utilizadas, os modelos CFD abrangentes tem sido empregados nos últimos anos para representar a operação da caldeira de recuperação considerando o maior número possível processos vinculados ao escoamento dos gases de combustão. O presente trabalho busca desenvolver um modelo CFD abrangente considerando o escoamento turbulento dos gases de combustão, o arraste das gotas de licor, a combustão homogênea dos voláteis em fase gasosa, as etapas de combustão heterogênea do licor preto e uma representação simplificada do leito carbonizado. Os resultados se mostraram coerentes com o comportamento apresentado na literatura. A simulação do modelo permite análise dos projetos e das operações da caldeira. / The advance of computer processing power and the development of numerical methods promote more efficient tools for modeling, design and optimization aiming to increase improvements in Kraft recovery boilers. Among the available techniques, the comprehensive CFD models have been applied in the last years to represent the recovery boiler operation considering as much as possible processes linked with flue gas flow. The objective of present work is the development of a comprehensive CFD model considering turbulent flue gas flow, black liquor droplets drag, volatiles homogeneous combustion in gas phase, the steps of heterogeneous black liquor combustion and the simplified interaction between flue gas flow and char bed. The results have good agreement with boiler behavior presented in the literature. The simulation of the comprehensive model allows the analysis of design and operations of the boiler.

Les variations de la composition des gaz naturels nécessitent un system de réglage automatique de la richesse de flamme pour des chaudières domestiques à gaz. Dans ce travail,deux solutions potentielles sont étudiées, à savoir la chimiluminescence de flamme et le courant d’ionisation. Des indicateurs de richesse sont déduits des signaux de chimiluminescence obtenus expérimentalement. L’impact de l’échange de chaleur entre la flamme et le brûleur sur des signaux de chimiluminescence est ensuite étudié. Une analyse est également faite des principaux facteurs pouvant perturber la caractérisation du signal de chimiluminescence. Le courant d’ionisation est ensuite étudié sur une flamme conique pour comprendre l’évolution de son intensité avec la position de sonde et avec les conditions de flamme. Il est montré ensuite que ces évolutions sont corrélées avec le changement de la distance entre la flamme et le brûleur. Enfin, une boucle de contrôle est développée pour démontrer la faisabilité d’un réglage automatique de richesse en exploitant le signal de chimiluminescence. / The variations of natural gas composition call for an automatic equivalence ratio regulation system for domestic gas boilers. Two potential techniques for this purpose are investigated, i.e. the flame chemiluminescence and ionization current. Equivalence ratio indicators are inferred from the chemiluminescence signal based on the experiments. The investigation proceeds by examining effects of the flameburner heat exchange on the chemiluminescence signal. The interference of several disturbing factors for the chemiluminescence signal characterization is also analyzed. The flame ionization current is investigated on a conical flame to understand the evolution of its intensity with the probe position and flame conditions. These changes are then attributed to modifications of the distance between the flame base and the burner rim. Finally a control loop is developed to demonstrate the feasibility of equivalence ratio self-regulation with the chemiluminescence signal.

The recovery boiler in a pulp and paper mill plays a dual role of recovering pulping chemicals and generating steam for either chemical processes or producing electricity. The efficiency of producing steam in the recovery boiler is limited by the first melting temperature of ash deposits that accumulate on the superheater tubes. Above the first melting temperature, the molten salt reacts with the protective oxide film that develops and dissolves it. The most protective oxide is determined by evaluating how little it dissolves and how its solubility changes in the molten salt. Solubility tests were done on several protective oxides in a known salt composition from a recovery boiler that burns hardwood derived fuel. ICP-OES was used to measure concentration of dissolved metal in the exposure tests while EDS and XRD were used to verify chemical compositions in exposure tests. NiO was found to be the least soluble oxide while Cr₂O₃ and Al₂O₃ had similar solubility with Fe₂O₃ being less soluble than Cr₂O₃ but more soluble than NiO. Exposure tests with pure metals and selected alloys indicated that even though Fe₂O₃ has little solubility, it is not a protective oxide and causes severe corrosion in stainless steels. The change in performance of iron based alloys was due to the development of a negative solubility gradient for Fe₂O₃ where Fe₂O₃ precipitated out of solution and created a continuous leaching of oxide. Manganese was found to be beneficial in stainless steels but its role is still unknown. Nickel based alloys were found to be least corroded due to nickel's low solubility and because it did not form a negative solubility gradient.

Lietuvoje nėra didelių iškastinio kuro išteklių (akmens anglies, gamtinių dujų ar naftos), galinčių patenkinti šalies energetinius poreikius. Todėl Lietuvai yra ypač svarbus tinkamas vietinių ir atsinaujinančių energijos išteklių galimybių išnaudojimas. Didžiausią potencialą Lietuvoje turi biomasė ir biokuras. Taip pat ne mažiau reikšmingas bioenergijos gamybos ir naudojimo privalumas yra mažesnis neigiamas poveikis aplinkai bei klimatui. Magistrantūros baigiamojo darbo tikslas yra išanalizuoti Lietuvos medienos išteklius bei jų atsinaujinimą. Išanalizuoti biokuro katilinių parametrus esant skirtingam šiluminiam našumui ir sudaryti bandymų lentelę remiantis energetiniame objekte sumontuota pakura. Darbe atliekama kietojo biokuro sudėties ir charakteristikų analizė. Aprašomas technologinio proceso automatinis valdymas, katilinės sandara ir t.t. / Lithuania there are no significant fossil fuel resources (coal, natural gas or oil) that can meet the country's energy needs. Therefore, the country is vital to the local and renewable energy opportunities. Lithuania has the highest potential of biomass and biofuels. It is also no less important bioenergy production and use of the advantage of a lower negative impact on the environment and climate. Master's thesis is to analyze the Lithuanian wood resources and their regeneration. Also consider biofuel combustion process using the latest technology of biofuels through the regime of the test results table. The work carried out in the solid biofuel composition and characteristics of the analysis. Chosen object and the regime carried out research and calculations to determine the biomass boiler parameters at different thermal performance. Describe the process automatic control, boiler structure.

The current boilers at the Brunna plant were installed in 1979 using oil and solvents to produce steam for the production and heating of the plant. To reduce the carbon dioxide emissions in compliance with Fresenius Kabi strategy a new biofuel boiler is about to be installed. Since the steam demand has been reduced during the years and it’s expensive to install a new boiler this study has been performed to calculate the actual steam demand for the plant at different scenarios. A smaller boiler requires a lower investment, achieves higher efficency and contributes to reduced carbon dioxide emissions. This report is intended to supply the management with information so that a decision regarding investments and employees can be made. The result is presented as different possible scenarios that are of great importance when deciding which boiler effect that is needed. Destillation, heating and the production have a major impact and must be considered when installing a new boiler. The results show that a boiler should be between 2-4 MW net effect depending on which scenario that is most likely to occur.

Purpose of this study was to investigate the possibilities of using Near-infrared (NIR) spectroscopy to detect glass in refuse derived fuel (RDF) as well as what on-line data of glass content could be used for in terms of boiler operation and performance determination. Sample configurations were done with dried RDF (to prevent mass loss due to moisture and spectroscopic disturbance) and increasing concentrations of colored soda-lime glass, total of 100 samples. Glass was randomly scattered among the RDF by shaking the added glass and RDF in a bucket to generate representative samples of real life conditions. NIR-spectra acquisition was done between 12000 and 4000 cm-1, at 8 cm-1 resolution and average of 32 scans. The determination of boiler performance was done in accordance to Swedish standards for acceptance testing and heat loss due to glass was treated as slag. Resulting performance calculations showed boiler efficiency via indirect method matching efficiency calculated via direct method (deviating at maximum 2 %) which validates the summarized losses (including due to glass). The heat loss due to glass was calculated to 0,068 MW/%glass, which equated to average of 0,16 MW for 2,37 % glass. Total heat loss was amounted to an average of 11,53 MW. The developed models were not satisfactory in their quality of regression prediction. Although some had, through pre-processing, good development of explained variance at increasing factors, but still had a “Not Applicable” coefficient of determination by regression prediction. The poor quality of models can be explained by poor glass detection (poor representation) of the spectroscopic instrument due to a combination of glass being randomly scattered in the background material and sometimes covered by RDF as well as that the NIR-spectroscopy light beam only hits a small area. By increasing the number of samples upwards 300 -500, the effect of random scatter of glass can be mitigated and acceptable models could be acquired. / FUDIPO