In 1939, a fifth steam generating unit was added to the Virginia Polytechnic Institute Central Heating and Power Plant. This unit was an E. Keeler, 500 horsepower, three drum, bent water tube type boiler, fired by a Westinghouse five retort underfeed stoker with link-grate section. Soon after the installation of this unit, W.F. Diamond and C.F. DeBush made an investigation to determine the effects of various fuel bed depths on the efficiency of the unity. Approximately 6 1/2 years have elapsed since their investigation was completed. No other tests have been conducted on the unit up to now. Consequently, its performance characteristics and maximum thermal efficiency at the present time are not accurately known. Even though Diamond and DeBusk made their investigation to determine the effect of various depths of fuel bed on the performance of the unit, the optimum percentage C0₂, and the range of load for maximum thermal efficiency, there is at the present time, a decided difference of opinion among the power plant personnel regarding these facts. It is contemplated that a sixth unit will shortly be installed in the V.P.I. Power Plant. Therefore, it is necessary to know what maximum continuous load and what peak loads for short periods of time the No. five until can be expected to carry now that it has been in operation for almost seven years. During the past two or three years, the operation of the stoker on the No. five unit has not been satisfactory. Large coke trees (see Discussion of Results, page 67) are formed in the fuel bed at the front end of the stoker where coal enters the furnace. There coke trees ride on the fuel bed as it moves from the front end of the furnace to the ash discharge orifice (see Fig 18), and are only partially consumed during combustion. When they reach the ash discharge orifice clogging results. This necessitates cleaning the orifice and ash discharge plates with a firing iron. Actual cases have been known to occur when a complete loss of load and a 50 per cent reduction in steam pressure have resulted from the clogging of the orifice. / Master of Science

Thesis. 1975. M.S.--Massachusetts Institute of Technology. Dept. of Mechanical Engineering. / Includes bibliographical references. / M.S.

D.Ing. / The thesis describes the development, installation, and testing of a neural network-based steam temperature controller for power plant boilers. Attention is focussed on the mechanical and thermodynamic aspects of the control problem, on the modelling and control aspects of the neural network solution, and on the practical and operational aspects of its implementation. A balance between theoretical and practical considerations is strived for. Experimental data is obtained from an operational coal fired power plant. As a starting point, the importance of good steam temperature control is motivated. The sensitivity of heated elements in boilers to changes in heat distribution is emphasized, and it is shown how various factors influence the heat distribution. The difficulties associated with steam temperature control are discussed, and an overview of developments in advanced steam temperature control on power plant boilers is given. The suitability of neural networks for process modelling and control are explored and the error backpropagation technique is shown to be well suited to the steam temperature control problem. A series of live plant tests to obtain modelling data is described and specific attention is given to discrepancies in the results. The prOcess of selecting the ideal network topology is covered and improvements in modelling accuracy by selecting different model output schemes are shown. The requirements for improving steam temperature control are listed and the philosophy of optimal heat distribution (OHD) control is introduced. Error backpropagation through the heat transfer model is utilized in an optimizer to calculate control actions to various fire-side elements. The scheme is implemented on a power boiler. It is shown that the optimizer manipulates control elements as expected. Problems with fuel-topressure oscillations and erroneous fuel flow measurement are discussed. Due to process oscillations caused by OHD control, a reduction in control quality is evident during mill trips and capability load runbacks. Substantial improvements over normal PID control however, are evident during load ramps.

M.S.

Thesis (MScEng (Mechanical and Mechatronic Engineering))--University of Stellenbosch, 2009. / ENGLISH ABSTRACT: Air-cooled steam condensers are used in arid regions where adequate cooling water is not available or very expensive. In this thesis the effect of steam-side and air-side effects on the condenser performance, steam distribution and critical dephlegmator length is investigated for air-cooled steam condensers as found in power plants. Solutions are found so that no backflow is present in the condenser. Both single and two-row condensers are investigated. The tube inlet loss coefficients have the largest impact on the critical dephlegmator tube length in both the single and two-row condensers. The critical dephlegmator tube lengths were determined for different dividing header inlet geometries and it was found that a step at the inlet to the dividing header resulted in the shortest tubes. Different ambient conditions were found to affect the inlet steam temperature, the steam flow distribution, heat rejection distribution and the critical dephlegmator length for the single and two-row condensers. There were differences in the steam mass flow distributions for the single and two-row condensers with opposite trends being present in parts of the condenser. The single-row condenser’s critical dephlegmator tube lengths were shorter than those of the two-row condenser for the same ambient conditions. Areas of potential backflow change with different ambient conditions and also differ between a single and two-row condenser. The two-row condenser always have an area of potential backflow for the first row at the first condenser fan unit. / AFRIKAANSE OPSOMMING: Droë lug-verkoelde stoom kondensors word gebruik in droë gebiede waar genoegsame verkoelingswater nie beskikbaar is nie of baie duur is. In hierdie tesis word die effek van stoomkant en lugkant effekte op die vermoë van die kondensor, die stoomvloeiverdeling en kritiese deflegmator lengte ondersoek vir lug-verkoelde stoom kondensors soos gevind in kragstasies. Dit word opgelos sodat daar geen terugvloei in enige van die buise is nie. ʼn Enkel- en dubbelry kondensor word ondersoek. Die inlaatverlieskoëffisiënte van die buise het die grootste impak op die lengte van die kritiese deflegmator buise in beide die enkel- en dubbelry kondensors. Die kritiese deflegmator buis lengtes is bereken vir verskillende verdeelingspyp inlaat geometrië en dit is gevind dat ʼn trap by die inlaat van die verdeelingspyp die kortste buise lewer. Dit is gesien dat verskillende omgewingskondisies die inlaat stoom temperatuur, die stoomvloeiverdeling, die warmteoordrag verdeling en die kritiese lengte van die deflegmator buise vir die enkel- en dubbelry kondensor. Daar was verskille tussen die stoomvloeiverdelings vir die enkel- en dubbelry met teenoorgestelde neigings in dele van die kondensor. Die kritiese deflegmator buis lengte vir die enkelry kondensor was korter as die vir die dubbelry kondensor vir dieselfde omgewingskondisies. Die areas in die kondensor waar terugvloei moontlik kan plaasvind in die kondensor verander met ongewingskondisies en verskil vir die enkel- en dubbelry kondensers. Die dubbelry kondensor het altyd ʼn area van moontlike terugvloei vir die eerste buisry by die eerste kondensor waaiereenheid.

Orientador: Takaaki Ohishi / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação / Made available in DSpace on 2018-08-13T16:15:59Z (GMT). No. of bitstreams: 1 Santos_ElmaPereira_M.pdf: 11960161 bytes, checksum: 3f762b2c22ed74c7ea44114aeba37c71 (MD5) Previous issue date: 2009 / Resumo: O gás natural é um combustível fóssil que pode ser utilizado tanto na indústria como no comércio, residências e veículos. Uma aplicação importante do gás natural é como fonte primária para geração de energia elétrica em usinas termelétricas. Seu uso possibilita uma maior estabilidade ao Sistema Elétrico Brasileiro, pelo fato de depender menos do nível de água nos reservatórios para atendimento da demanda de energia elétrica. Como o gás natural possui uma estocagem complexa e onerosa, a quantidade de demanda de gás afeta diretamente as suas etapas de produção e transporte, já que toda a quantidade produzida e transportada deverá ser consumida. Desse modo, a operação do sistema de suprimento de gás natural é fortemente dependente das decisões de seus consumidores. As usinas termelétricas estão entre os maiores consumidores de gás, de forma que o despacho das usinas termelétricas afeta fortemente a operação do sistema de gás. Por outro lado, restrições no sistema de suprimento de gás também podem afetar a operação das usinas termelétricas. Esta forte dependência operativa entre estes dois sistemas requer uma operação coordenada para se obter uma operação mais eficiente e segura. Esta tese apresenta um modelo de despacho econômico aplicado a usinas termelétricas que usam gás natural como fonte primária, considerando os custos de produção, transporte de gás natural e de geração de energia elétrica. A modelagem matemática resulta em um problema misto não linear. Para resolução foi utilizada uma abordagem híbrida, que combina um modelo baseado em Programação Linear e um modelo não linear. O problema não linear é resolvido através do método de Newton. / Abstract: Natural gas is a fossil fuel that can be used in industry, trade, residence and vehicles, among others. An important application of natural gas is as a primary source for electricity generation in thermoelectric power plants. In the Brazilian Electric System this source increase the system stability, once it is less dependent of the water level in tanks to serve the demand for power. As natural gas storage it is more complex and expensive, the amount of gas directly affects the production and transportation stages, once the entire amount that is produced and transported must be consumed. Thus, the operation of the supply system of natural gas is strongly dependent on decisions of their consumers. The thermoelectric power plants are among the largest gas consumers, so the dispatch of thermoelectric plants affects strongly the gas system operation. On the other hand, restrictions in the gas supply system may also affect the operation of thermoelectric plants. This strong operative dependence between these two kinds of systems, requires a coordinated operation with the aim of obtaining a more efficient and safer operation. This thesis presents a model of economic dispatch applied to thermoelectric power plants that use natural gas as a primary energy source, considering the costs of production, transportation of the natural gas and electricity generation. The mathematical modeling results in a nonlinear mixed problem. For resolution was used a hybrid approach that combines a model based on Linear Programming and a nonlinear. The nonlinear problem is solved by the Newton's method. / Mestrado / Engenharia de Computação / Mestre em Engenharia Elétrica

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Civil Engineering, 1981 / Bibliography: leaves 264-269. / by John Jay Shaw. / Ph. D. / Ph. D. Massachusetts Institute of Technology, Department of Civil Engineering