Diploma thesis deals with problematics of offtake of flue gasses. In experimental part there was measured compound of flue gasses by analyzator of flue gates. Aplication is a project of heating of object of The Academy of Sciences of the Czech Republic in Brno. Project solves design of heating system, flue and of source of heat. Heating area is created by floor convectors,towel rails and radiators. Source of heat is designed in two variants : as a cascade of condensation boilers and as a cascade of low-temperature boilers.

Sootblowing is a process in which supersonic steam jets are used to periodically blast deposits off heat transfer tubes in kraft recovery boilers. However, sootblowing significantly consumes the valuable high pressure steam generated by the boiler, hence it should be optimized. A recovery boiler consists of three convective sections - superheater, generating bank and economizer. The tube arrangement in these sections, particularly the tube spacing is different from each other. Moreover, tubes in an economizer are finned. A sootblower jet will interact differently with these tube arrangements, potentially affecting its strength, and hence deposit removal capability. The objective of this work was to characterize jet/tube interaction in the three sections of a recovery boiler. Lab-scale experiments were conducted in which these interactions were visualized using the schlieren technique coupled with high-speed video, and were quantified by pitot pressure measurements. This work is the first to visualize the interactions. The offset between the jet and tube centrelines, the nozzle exit diameter relative to the tube diameter, and the distance between the nozzle and tube were varied to examine their effects on jet/tube interaction. Results showed that due to the very low spreading rate of a supersonic jet, a jet (primary jet) stops interacting with a superheater platen when the jet is only a small distance away from it. When the jet impinges on a tube, the jet deflects at an angle, giving rise to a weaker ‘secondary’ jet. Due to the large inter-platen spacing, a secondary jet has an insignificant impact in a superheater. In a generating bank, the primary jet weakens between the closely spaced tubes due to increased mixing. However, a secondary jet impinges on the adjacent tubes exerting a high impact pressure on those tubes. The primary jet also weakens between finned economizer tubes, but remains stronger for a greater distance than in a generating bank. As in the case inside a generating bank, a secondary jet also impinges on adjacent rows of tubes in an economizer. The results imply that in a superheater, a sootblower jet must be directed close to the platens to yield useful jet/deposit interactions, and to avoid wasting steam by blowing between the platens. In a generating bank, deposits beyond the first few tubes of a row experience a weaker sootblower jet, and thus may not be removed effectively. However, secondary jets may contribute to removing deposits from the first few adjacent tubes. They may also induce erosion-corrosion of those tubes. Secondary jets may also help remove deposits from adjacent rows in a finned tube economizer. In an economizer, the strength and hence, the deposit removal capability of a sootblower jet diminish only slightly beyond the supersonic portion of the jet. A mathematical model was also developed to determine the feasibility of using inclined sootblower nozzles in recovery boiler superheaters, and suggests that it may be possible to clean superheater platens more effectively with slightly inclined nozzles.

Sootblowing is a process in which supersonic steam jets are used to periodically blast deposits off heat transfer tubes in kraft recovery boilers. However, sootblowing significantly consumes the valuable high pressure steam generated by the boiler, hence it should be optimized. A recovery boiler consists of three convective sections - superheater, generating bank and economizer. The tube arrangement in these sections, particularly the tube spacing is different from each other. Moreover, tubes in an economizer are finned. A sootblower jet will interact differently with these tube arrangements, potentially affecting its strength, and hence deposit removal capability. The objective of this work was to characterize jet/tube interaction in the three sections of a recovery boiler. Lab-scale experiments were conducted in which these interactions were visualized using the schlieren technique coupled with high-speed video, and were quantified by pitot pressure measurements. This work is the first to visualize the interactions. The offset between the jet and tube centrelines, the nozzle exit diameter relative to the tube diameter, and the distance between the nozzle and tube were varied to examine their effects on jet/tube interaction. Results showed that due to the very low spreading rate of a supersonic jet, a jet (primary jet) stops interacting with a superheater platen when the jet is only a small distance away from it. When the jet impinges on a tube, the jet deflects at an angle, giving rise to a weaker ‘secondary’ jet. Due to the large inter-platen spacing, a secondary jet has an insignificant impact in a superheater. In a generating bank, the primary jet weakens between the closely spaced tubes due to increased mixing. However, a secondary jet impinges on the adjacent tubes exerting a high impact pressure on those tubes. The primary jet also weakens between finned economizer tubes, but remains stronger for a greater distance than in a generating bank. As in the case inside a generating bank, a secondary jet also impinges on adjacent rows of tubes in an economizer. The results imply that in a superheater, a sootblower jet must be directed close to the platens to yield useful jet/deposit interactions, and to avoid wasting steam by blowing between the platens. In a generating bank, deposits beyond the first few tubes of a row experience a weaker sootblower jet, and thus may not be removed effectively. However, secondary jets may contribute to removing deposits from the first few adjacent tubes. They may also induce erosion-corrosion of those tubes. Secondary jets may also help remove deposits from adjacent rows in a finned tube economizer. In an economizer, the strength and hence, the deposit removal capability of a sootblower jet diminish only slightly beyond the supersonic portion of the jet. A mathematical model was also developed to determine the feasibility of using inclined sootblower nozzles in recovery boiler superheaters, and suggests that it may be possible to clean superheater platens more effectively with slightly inclined nozzles.

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.

M. Tech. Mechanical Engineering. / Discusses the economiser design to absorb as much heat as possible within the flue gases. Fly ash particles, a product of combustion, entrained in the flue gas of the furnace part of the boiler in coal fired boilers, affect economiser thermal performance by causing erosive wear and scale on the outer surface of the economiser tubes along the flow path, which in turn increases the thermal resistance characterisation of coals in relation to combustion behaviour traditionally relies on staged quenching of the reaction and subsequent gravimetric analysis of the remaining sample. Three typical steam-raising coals are compared with regard to reactivity and broadly examined relative to their petro-graphic constituents and other standard laboratory tested samples. A significant correlation was found between the ignition temperature and the hydrogen or carbon ratio determined by the ultimate analysis, inter alia, the erosion rate and the heat transfer rate.

This thesis presents the development of a Neural Network Based Controller (NNBC) for chain grate stoker fired boilers. The objective of the controller was to increase combustion efficiency and maintain pollutant emissions below future medium term stringent legislation. Artificial Neural Networks (ANNs) were used to estimate future emissions from and control the combustion process. Initial tests at Casella CRE Ltd demonstrated the ability of ANNs to characterise the complex functional relationships which subsisted in the data set, and utilised previously gained knowledge to deliver predictions up to three minutes into the future. This technique was then built into a carefully designed control strategy that fundamentally mimicked the actions of an expert boiler operator, to control an industrial chain grate stoker at HM Prison Garth, Lancashire. Test results demonstrated that the developed novel NNBC was able to control the industrial stoker boiler plant to deliver the load demand whilst keeping the excess air level to a minimum. As a result the NNBC also managed to maintain the pollutant emissions within probable future limits for this size of boiler. This prototype controller would thus offer the industrial coal user with a means to improve the combustion efficiency on chain grate stokers as well as meeting medium term legislation limits on pollutant emissions that could be imposed by the European Commission.

Made available in DSpace on 2016-08-18T17:23:41Z (GMT). No. of bitstreams: 1 DISSERTACAO_MONICA JACYRA DA SILVA CARVALHO.pdf: 12590784 bytes, checksum: d0f58b8044b522477f67a264ed154573 (MD5) Previous issue date: 2014-10-03 / The metallurgical Alfa has three areas of operations: the Port, the Refinery and the Smelter. The intermediate area produces alumina using steam as an energy source. This comes from two High Pressure Boilers that operate together and are essential for the full operation of the process, so it is necessary make it reliable equipment. With this in mind, Alfa industry bases its operations management in a Own Business System adapted guidelines of the Toyota Production System (TPS) and Total Productive Maintenance (TPM). So, this was seen as an opportunity for research, which was carried through the search for understanding of the Business System, the definition and understanding of the equipment, the realization of hiking equipment by a multidisciplinary team, with a survey of existing equipment failures, by mapping the current situation, identifying the losses associated with the faults previously raised by raising costs and monitoring focused on technical resolution and human reliability during maintenance activities, which were carried out to remedy or minimize failures, as described. Thusthere was a reduction in production losses around 3484.28 t SGA/year and 304.526,07 US$/year of 2011compared to the year 2012. And also proof that the boiler reaches 100% of their operational availability and yes, they can become confident with the implementation of continuous improvement. / A indústria metalúrgica Alfa possui três áreas de operações: o Porto, a Refinaria e a Redução. A área intermediária produz alumina utilizando como fonte de energia, o vapor. Este é oriundo de duas Caldeiras de Alta Pressão que operam juntas e são essenciais ao pleno funcionamento do processo, por isso é necessário torná-las equipamentos confiáveis. Com este intuito, a indústria Alfa alicerça sua gestão de operações em um Sistema de Negócios Próprio adaptado das diretrizes do Sistema Toyota de Produção (STP) e da Manutenção Produtiva Total (MPT). Assim, esta situação foi vista como oportunidade de pesquisa, a qual foi realizada através da busca pelo entendimento do Sistema de Negócios, pela definição e entendimento dos equipamentos, pela realização de caminhadas pelos equipamentos com equipe multidisciplinar, pelo levantamento das falhas existentes nos equipamentos, pelo mapeamento da situação atual, pela identificação das perdas associadas as falhas levantadas anteriormente, pelo levantamento de custos e pelo acompanhamento focado na resolução técnica e na confiabilidade humana durante as atividades de manutenção, as quais foram realizadas para sanar ou minimizar as falhas, já descritas. Desta forma, houve uma redução nas perdas de produção em torno de 3.484,28 t SGA/ano e 304.526,07 US$/ano do ano de 2011 em relação ao ano de 2012. E também a comprovação que as caldeiras alcançam 100% da sua disponibilidade operacional e sim, podem tornar-se confiáveis com a implementação da melhoria contínua.

Orientador: Jorge Isaías Llagostera Beltrán / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica / Made available in DSpace on 2018-08-20T08:08:23Z (GMT). No. of bitstreams: 1 GuarineloJunior_FlavioFernando_D.pdf: 112586941 bytes, checksum: 8ca74b9cc6e907dc47ec88f2c901a8b1 (MD5) Previous issue date: 2012 / Resumo: O atendimento da demanda crescente de eletricidade, associado à necessidade do cumprimento de metas de emissões de gases causadores do aquecimento global, será um grande desafio ao setor elétrico nas próximas décadas. A geração de eletricidade ainda necessitará de combustíveis fosseis por muitos anos e a busca por eficiência energética nos processos térmicos que envolvem as usinas termoelétricas será determinante ao cumprimento das metas de emissões. Neste contexto, o ciclo combinado tem sido apresentado como a tecnologia mais eficiente e com o menor impacto ambiental quando se considera o uso de combustíveis fósseis na geração de eletricidade. Possui curtos prazos de instalação e custos relativamente baixos em comparação às outras tecnologias, quer façam uso de fontes renováveis ou não, e tem passado por processos de evolução tecnológica que permitem eficiências de até 62%. Mesmo que apresente características tão favoráveis, o desempenho do ciclo combinado é uma tecnologia sensível quando passa a operar em condições ambiente diferentes daquelas especificadas em projeto. A análise do comportamento do desempenho nestas condições é de extrema importância para fins de avaliação da viabilidade técnica e econômica do ciclo no local a ser instalado e é o tema central deste trabalho. Portanto, a proposta deste trabalho é analisar termodinamicamente a operação do ciclo combinado operando em condições fora-de-projeto (off design) através do desenvolvimento de um sistema de equações não lineares que representam os balanços de massa e energia de cada componente e as relações entre si. O conjunto de equações do modelo analítico é resolvido através de uma ferramenta computacional comercialmente disponível, a qual permite a definição de variáveis independentes e das restrições necessárias a uma solução objetiva. A lógica empregada na solução do conjunto de equações define uma relação direta entre as mesmas através da redução do grau de liberdade de uma determinada variável. A modelagem analítica revelou ser uma ferramenta importante na investigação do comportamento do desempenho do ciclo como um todo e a dependência termodinâmica entre os seus componentes / Abstract: The worldwide growing demand for electricity associated with global warming issues is becoming a great challenge to the electric sector for the next decades. As the power generation still depends on the fossils fuels as main source, the combined cycle is further recognized for its better environmental performance in mitigating air pollution and by reducing the global warming effects. Based on this perspective, the combined cycle has been presented as the most efficient technology, by providing advantages due to its smaller environmental impact when considering the use of fossils fuels in power generation. It is characterized by its low capital cost and short construction lead time in comparison with other technologies, whatever type of renewable fuel is being used or not, it has been experiencing a technological evolution that boost its overall efficiencies to more than 62%. Even though it has been presented with such favorable characteristics, the overall efficiency of the combined cycle is very sensitive to environmental conditions as well as running from the base load. By analyzing all thermodynamic parameters in the combined cycle under off - design conditions it can provide a better understanding in order to develop a technical and economical feasibility and it is the core issue of this work. Therefore, the proposal of this work aims to develop a system of non linear equations that represent the mass and energy balances of all component and the thermodynamic relationships among them. The group of equations of the analytical model is solved through a computational tool, commercially available, which allows the definition of independent variables and all constraint needs to reach a target solution. The logic employed in solving the system of equations defines a direct relationship among each combined cycle's component through the reduction of the degree of freedom of a certain variable. The analytical modeling revealed to be an important tool in the investigation of the combined cycle operation behavior as a whole and the thermodynamic dependence among all components / Doutorado / Termica e Fluidos / Doutor em Engenharia Mecânica

Med skenade bunkerkostnader och överdimensionerade motorinstallationer har allt fler handelsfartyg börjat operera under benämningen slow steaming, vilket innebär att sotbränderna har ökat i avgaspannor/ekonomiser och i en del extrema fall har branden övergått till en vätgasbrand. Arbetet utreder främst dieselmotorer som använder restoljor som bränsle och opererar med en låg motorbelastning. Syftet med undersökningen var att se vad som leder till att oförbränt bränsle och cylinderolja ackumuleras i avgassystem samt beskriva vilka åtgärder som kan göras för att eliminera risken för att en brand uppstår i en avgaspanna alternativt en ekonomiser. Metoden som har används för undersökningen är en litteraturstudie genom datainsamling och facklitteratur inom området dieselmotorer och främst marina ångpannor. Resultaten som framkommit av undersökningen visar på svårigheten att köra en dieselmotor på ett lägre effektuttag då hela fartyget ofta är konstruerat för en drift med tjockolja där motorn belastas på ca 80% av sin effekt. Några av de slutsatser ur studien visar på att även när en felfri motor ej uppnått drifttemperatur sker en ofullständig förbränning av bränsle och smörjolja på grund av den låga temperaturen i förbränningsrummet. Detta kan medföra operativa risker genom att oförbränt bränsle och cylinderolja ackumuleras i avgassystem som blöta och sotiga beläggningar. Slutsatserna som kan dras utifrån de olika sotningsmetoder vilka har jämförts i resultatet har vattentvättning, ångsotning och rengöringsmedel med katalytisk verkan fungerat bäst på de flesta beläggningar. / With escalating bunker costs and oversized engine installations an increasing number of vessels have started to operate in a mode known as slow steaming. This means that the soot fires in exhaust gas boilers/economizers have increased and in some extreme cases led to hydrogen fires. This thesis focus on how diesel engines use residual fuels and operate with a low engine load. The purpose of this thesis is to investigate whether incomplete combustion caused by a low combustion temperature leads to the accumulation of unburned fuel and cylinder oil in the exhaust gas system and to describe which precautions eliminate the risk of a fire in the exhaust gas boiler or exhaust gas economizer. A literature review has been conducted and data has been collected in the field of diesel engine with priority given to marine steam boilers. The result of the study shows how difficult (problematic) it is to run a diesel engine at a lower power output, since the vessel often is designed for a heavy fuel oil operation when the engine load approximately 80 % output.                      Conclusions from the study show that even when a faultless engine has not reached operating temperature, incomplete combustion of fuel and lubricating oil occurs due to the low temperature in the combustion chamber. This can entail operational risks by accumulating unburned fuel and cylinder oil in exhaust systems such as wet and sticky carbon deposit. The result shows that water washing, steam cleaning and catalytic cleaning are the most efficient cleaning methods for most deposits in exhaust gas boilers and economizers.

The topic of a master thesis is solution of infant’s school heating. The thesis summarizes state of art infant’s school heating from practical and legislative point of view. The thesis contains solution of infant’s school heating created by author of thesis. In addition, the thesis contains an experiment which is focused on examination of heat output from cover radiator.