SESSION: Thermal, hydro, wind and other Power Plants | Eksploatacioni problemi termo, hidro, vetro i drugih elektrana
papers selected for Symposium Session titled: Thermal, hydro, wind and other Power Plants | Eksploatacioni problemi termo, hidro, vetro i drugih elektrana
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Nenad Crnomarkovic - VINCA Institute of Nuclear Sciences , Miroslav Sijercic - VINCA Institute of Nuclear Sciences , Srdjan Belosevic - VINCA Institute of Nuclear Sciences
title: MODELING OF RADIATIVE HEAT TRANSFER INSIDE THE PULVERIZED COAL FIRED FURNACE OF POWER PLANT
Abstract text
Thermal radiation is dominant mode of heat transfer from hot combustion products to furnace walls and colder parts of furnace medium, inside the pulverized coal fired steam boiler furnaces. Therefore, accurate modeling of radiative heat transfer is very important for prediction of steam boiler behavior in various operating conditions. A number of methods for radiative heat transfer has been developed, among which the most important are: Monte Carlo, finite volume method (FVM), discrete ordinate method (SN), spherical harmonics method (PN), six flux method, and Hottel’s zonal method. In this work, Hottel’s zonal method has been applied, because it is characterized by the great accuracy of evaluation of absorbed radiative fluxes.
Hottel’s zonal method is based on division of furnace volume and walls to volume and surface zones. For each pair of zones, direct exchange areas and total exchange areas that allow for multiple reflection of radiation from furnace wall are evaluated. Absorbed heat of one zone (volume or surface) is determined as sum of heat exchange of that zone with all the zones in the furnace.
Heat exchange among zones depends on radiative properties of medium that emits, absorbs and scatter radiation. Furnace medium is two phase mixture, that contains products of complete coal combustion and particles of coal, char, fly ash and soot. Since coal particles exist only in the vicinity of burners, and char particles exist in the zone of intensive combustion, which is not extensive, furnace medium can be considered to consist of gaseous combustion products and particles of fly ash and soot. The most important radiative properties are absorption coefficient, scattering coefficient and scattering phase function. Absorption coefficient of furnace gases is determined from single gray gas model. Spectral absorption coefficient of the cloud of fly ash particles is determined from the value of efficiency factor for absorption evaluated by the Mie theory, and from particle size distribution. Total absorption coefficient of the cloud of fly ash particles is determined as Planck mean value. Absorption coefficient of the cloud of soot particles is found from assumed soot volume fraction. Particle size distribution of fly ash is obtained from particle size distribution of pulverized coal under assumption that that particle of coal turns into particle of fly ash after process of complete combustion. Scattering phase function is unity, because uniform scattering of radiation at every direction is adopted.
Adopted model of radiative heat transfer has been applied for modeling the processes in the furnace of TENT A2 steam boiler rated at 240 MWe. Two phase flow has been modeled with exchange of momentum mass and heat among phases, with chemical reactions and radiative heat exchange. Temperature field, as well as flow field and concentration fields have been obtained from transport equations for momentum, heat and mass. Set of equations has been closed by the transport equations for kinetic turbulent energy and its decay. Results of modeling showed acceptable agreement with results of measurement and enabled determination of absorbed radiative fluxes along the furnace walls.
Srđan Belošević - Institut za nuklearne nauke „Vinča“, Laboratorija za termotehniku i energetiku, P.p. 522, 11001 Beograd , Miroslav Sijerčić - Institut za nuklearne nauke „Vinča“, Laboratorija za termotehniku i energetiku, P.p. 522, 11001 Beograd , Nenad Crnomarković - Institut za nuklearne nauke „Vinča“, Laboratorija za termotehniku i energetiku, P.p. 522, 11001 Beograd , Dragan Tucaković - Mašinski fakultet Univerziteta u Beogradu, Kraljice Marije 16, 11120 Beograd 35 , Titoslav Živanović - Mašinski fakultet Univerziteta u Beogradu, Kraljice Marije 16, 11120 Beograd 35
title: REGULACIJA PLAMENA U LOŽIŠTU ENERGETSKOG KOTLA PRIMENOM NUMERIČKE SIMULACIJE (FLAME CONTROL IN A UTILITY BOILER FURNACE BY MEANS OF NUMERICAL SIMULATION)
Abstract text
U sklopu ostvarenja radnih parametara energetskog kotla posebna pažnja se poklanja regulaciji geometrije i položaja plamena, zbog značajnog uticaja na razmenu toplote u ložištu. Oblik i položaj plamena zavise od različitih parametara, čiji uticaj nije jednoznačan. Kao ilustracija mogućnosti primene numeričke simulacije za efikasnu regulaciju geometrije i položaja plamena, u radu su prikazani odabrani rezultati simulacije strujnotermičkih uslova u ložištu kotla bloka TE Kostolac-B snage 350 MWe, sa sagorevanjem ugljenog praha. U cilju analize pogonskih stanja predmetnog ložišta razvijen je diferencijalni 3D matematički model spregnutih procesa dvofaznog turbulentnog reaktivnog toka sa razmenom toplote i mase i odgovarajući numerički kod i softver sa korisničkim interfejsom, koji omogućava i kuplovanje sa posebnim proračunskim modulom pripreme ugljenog praha. U radu je opisan postupak i naglašen značaj adekvatne verifikacije numeričkog koda i validacije proračuna, radi pouzdanog korišćenja razvijenog modela za simulaciju rada ložišta u promenljivim radnim uslovima. Primenom razvijenog softvera izvedena je analiza uticaja na karakteristike plamena u ložištu različitih pogonskih parametara, kao što su: raspored mlinova u radu, prisis falš vazduha i raspodela protoka ugljenog praha i sekundarnog vazduha, kao i frakcija ugljenog praha, po etažama gorionika. U cilju postizanja pozitivnih ekonomskih i ekoloških efekata i pouzdanije eksploatacije postrojenja, numerička simulacija omogućava analizu uticaja velikog broja radnih parametara, optimizaciju sagorevanja i razmene toplote i identifikaciju i rešavanje najznačajnijih pogonskih problema, kao što je suviše visok ili nizak položaj plamena.
Within efforts to attain a utility boiler unit operation parameters, a special attention is given to a control of flame geometry and position, because of the significant impact on the heat transfer in the furnace. Shape and position of the flame depend on different parameters exerting considerably complex influences. As an illustration of the possibilities for application of numerical simulation in the efficient control of the flame geometry and position, the paper presents selected results of the thermal-flow conditions simulation in pulverized coal fired-furnace of power plant Kostolac-B 350 MWe boiler unit. To analyze the furnace operation conditions, a differential 3D mathematical model has been developed, considering mutually dependent processes in two-phase turbulent reactive flow with heat and mass transfer. Corresponding numerical code and software have been also developed, with user-interface enabling additional coupling with another software module aimed for calculation of air-coal dust mixture preparation. The paper describes the method and points out the importance of a proper verification of the numerical code and validation of the calculations, for the purpose of reliable application of the model for simulation of the furnace operating in different working conditions. Using the software, an analysis has been performed regarding the influence on the furnace flame characteristics of different operation parameters, such as: the coal mills operation scheme, the false air intake and distribution of pulverized coal and secondary air flow rates, as well as coal particle fractions, over the burners tiers. To achieve positive economical and environmental effects and reliable exploitation, numerical simulation enables impact-analysis of many operation parameters, optimization of combustion and heat transfer and solving critical operation problems, like excessively high or low flame position.
Јеленко Б. Манић - ТЕ "Колубара Б"
title: Oштећења на парним турбинама после дуготрајне експлоатације
Abstract text
У раду ће бити указано на искуства из погона и најчешћа оштећења парних турбина после дуготрајне експлоатације како у нашим термоелектранама, тако и у термоелектранама у свету. Карактеристични примери биће описани и илустровани.
Prof. dr Milan Ćalović - Energoprojekt ' ENTEL, Beograd , Dr Miodrag Mesarović - Energoprojekt ' ENTEL, Beograd
title: THE VALUE OF WIND POWER PLANTS
Abstract text
The aim of any power plant in a power system is to supply the load in a reliabbe, economically viable and environmentaly friendly manner. Different power plants can fulfil these basic requirements in different ways with various degree of efficiency. This paper is devoted to the consideration of the behaviour of wind power plants of wind power plants in view of the common standards required to be met by the present power power producers in all of the three above mentioned major aspects (reliability, economy and ecology). A comparison with other power generating sources is carried out. The particular emphasis is placed to the organisation of modern power industry with respect to the acceptability of wind power when large scale wind farms are connected to electrical grids. Globally, wind power generation increased more than fivefold between 2000 and 2007, which gives raise to some specific problems they may involve. At the end of 2007, worldwide capacity of wind-powered generators was 94.1 gigawatts. Although wind currently produces about 1% of world-wide electricity use (2007 data), it accounts for approximately 19% of electricity production in Denmark, 9% in Spain and Portugal, and 6% in Germany and the Republic of Ireland. The specific requirements of grid management with high penetration of wind power are also discussed as different types of wind turbine generators behave differently during transmission grid disturbances. Electricity generated from wind power can be highly variable from hour to hour, daily, and seasonally. Annual variation also exists, but is not as significant. Because instantaneous electrical generation and consumption must remain in balance to maintain grid stability, this variability can present substantial challenges to incorporating large amounts of wind power into a grid system. Intermittency and the non-dispatchable nature of wind energy production can raise costs for regulation, incremental operating reserve, and (at high penetration levels) could require energy demand management, load shedding, or storage solutions. At low levels of wind penetration, fluctuations in load and allowance for failure of large generating units requires reserve capacity that can also regulate for variability of wind generation. Stored energy increases the economic value of wind energy since it can be shifted to displace higher cost generation during peak demand periods. All of these aspects are adressed with respect to the optimum penetration level of wind power to a power system.
Dr Radoslav Raković - Energoprojekt-Entel ad Beograd , Ivana Simović - Rudarski institut Beograd-Zemun
title: PRINCIPI IZBORA TEHNOLOGIJE ZA ON-LINE PRAĆENJE I UJEDNAČAVANJE KVALITETA UGLJA
Abstract text
Termoelektrane koje koriste ugalj kao gorivo predstavljaju jedan od najvećih emitera gasova sa efektom staklene bašte u svetu, pa i u našoj zemlji. Emisija ovih gasova zavisi od sastava uglja (u našim uslovima lignita), pre svega od sadržaja ugljenika, pa je neophodno analizirati raspoložive tehnologije za on-line analizu karakteristika uglja u cilju izbora najpovoljnije koja bi se mogla primeniti u procesu ujednačavanja kvaliteta, odnosno homogenizacije uglja za sagorevanje u termoelektranama. U radu je dat kratak pregled parametera kvaliteta uglja iz kolubarskog i kostolačkog ugljenog basena i tehničkih rešenja on-line analizatora kao i procedura za izbor najpovoljnijeg on-line analizatora za primenu u okviru sistema za kontinualno praćenje i ujednačavanje kvaliteta uglja. Posebna pažnja posvećena je uticaju homogenizacije kvaliteta uglja na energetsku efikasnost termoelektrana i emisiju ugljen dioksida.
Aleksandar Ribić - Institut Mihajlo Pupin
title: PID autotuning i primjenljivost u termotehnici
Abstract text
Danas je većina industrijskih regulatora opremljena procedurama za automatsko podešavanje parametara regulatora (autotuning). Za one koji nemaju ovu mogućnost na tržištu nalazimo širok spektar softvera za analizu i optimalno podešavanje regulacionih kontura. U radu je analizirano koliko ovakav softver stvarno može pomoći prilikom podešavanja regulatora u termotehnici, ali i ostalim granama industrije. Analiyirano je nekoliko primjera koji se često pojavljuju u termoenergetskim postrojenjima.
Рундыгин Ю.А. - Санкт-Петербургский государственный политехнический университет, Россия , Григорьев К.А. - Санкт-Петербургский государственный политехнический университет, Россия , Скудицкий В.Е. - ООО "Компания "НТВ-энерго" (Санкт-Петербург), Россия , Тринченко А.А. - Санкт-Петербургский государственный по
title: РАЗВИТИЕ НИЗКОТЕМПЕРАТУРНОЙ ВИХРЕВОЙ ТЕХНОЛОГИИ СЖИГАНИЯ ТВЕРДЫХ ТОПЛИВ
Abstract text
Создание нового и модернизация действующего котельного оборудования в энергетике на твердом топливе требует применения высокоэффективных, экологически чистых технологий сжигания, одной из которых является низкотемпературная вихревая (НТВ).
Основная идея НТВ-сжигания заключается в организации двух зон горения, которые разнесены по высоте топки. В нижнем объеме НТВ-топки за счет взаимодействия потоков горелочно-сопловых устройств организована вихревая зона активного горения, где в условиях многократной циркуляции частиц сгорает до 90…95 % топлива. Остальная часть топлива сгорает в зоне догорания, которая располагается над вихревой зоной.
Активная вихревая аэродинамика, многократная циркуляция топлива и ступенчатый подвод окислителя в зону активного горения позволяют получить ряд положительных эффектов (по сравнению с обычной технологией сжигания в прямоточном факеле), основные из которых следующие:
1) Стабилизация воспламенения и горения обеспечивает эффективное сжигание высоковлажных (до = 60 %) и низкореакционных топлив;
2) Рост конвективной составляющей в теплообмене повышает тепловую эффективность НТВ-топки и позволяет уменьшить (на 10…20 %) габариты (при создании новых котлов), либо повысить тепловую нагрузку топки (при модернизации действующего оборудования);
3) В НТВ-топках наблюдается резкое снижение интенсивности загрязнения поверхностей нагрева, что важно при сжигании сильно шлакующих топлив (с низкой температурой плавления золы);
4) Выравнивание температурного поля, снижение (на 200…300 градусов) его общего уровня, горение основной части топлива при недостатке окислителя позволяют резко снизить (на 30…50 %) генерацию оксидов азота. Кроме того, условия НТВ-процесса способствуют повышению связывания оксидов серы за счет реакций с основными оксидами (CaO) минеральной части топлива.
При НТВ-сжигании бурых углей и лигнитов желательно существенное угрубление помола (до R1000 = 10…30 %), что позволяет обеспечить взрывобезопасность системы подготовки топлива при любом составе сушильного агента и резко снизить затраты энергии на размол топлива.
НТВ-технология сжигания прошла апробацию в котлах паропроизводительностью от 20 до 420 т/ч на широкой гамме твердых топлив, таких как торф, бурые и каменные угли, горючие сланцы, отходы деревообработки и микробиологического производства. Теплотехнические характеристики опробованных топлив изменяются в широких пределах: теплота сгорания = 6,7…23 МДж/кг, влажность = 9…60 %, зольность = 6…50 %, выход летучих веществ = 15…90 %. Некоторые котельные установки уже отработали более 100 тысяч часов и длительной эксплуатацией доказали эффективность НТВ-сжигания.
За последние годы на основе обобщения опыта НТВ-сжигания и численного моделирования разработаны и опробованы в промышленных условиях новые схемы и конструкции горелочно-сопловых устройств для реализации НТВ-процесса. Новые технические решения позволили улучшить технико-экономические и экологические показатели НТВ-топок.
V.I. Mijakovski - Faculty of Technical Sciences, Bitola, Macedonia , N.I. Mijakovski - Nextsense, Skopje, Macedonia
title: WINTER OPERATING REGIME OF NATURAL DRAUGHT COOLING TOWER
Abstract text
During winter, at low temperatures of external air, air circulation through natural draught cooling tower causes greater cooling of the water and appearance of ice on places where air is introduced into the tower. In such case, with proper operation of the system cooling tower – pump station, and by reducing water's cooling range, temperature of the cold water should be maintained at sufficiently high temperature level in order to avoid freezing of the water in the tower and appearance of ice at air entering surfaces.
Dragan Tucaković - Mašinski fakultet, Univerziteta u Beogradu , Titoslav Živanović - Mašinski fakultet, Univerziteta u Beogradu , Srđan Belošević - Institut za nuklearne nauke VINČA, Laboratorija za termotehniku i energetiku
title: A COMPUTER CODE FOR THE PREDICTION OF MILL GASES AND HOT AIR DISTRIBUTION BETWEEN BURNERS' SECTIONS AT THE UTILITY BOILER
Abstract text
One of the main tasks during the design or simulation and analyses of the utility steam boiler operation is the prediction of a distribution of mill gases and hot air flow rates between burners' sections. These are the boundary conditions for the combustion process in the boiler furnace, and they strongly influence the steam boiler economy and reliability of operation. A computer code for the prediction of mill gases and hot air distribution between boiler burners has been developed. The code is based on simultaneous calculations of material and heat balances for the fan mill and corresponding air tracts. This paper presents a methodology of performed calculations, the code structure, and results obtained for the steam boiler furnace of 350 MWe thermal power plant equipped with eight fan mills.
Dragan P. Popović - Institut "Nikola Tesla", Beograd , Miloš Stojković - Institut "Nikola Tesla", Beograd
title: THE EFFECTS OF GENERATOR VOLTAGES CONTROL IN REAL TIME
Abstract text
ABSTRACT
This papers presents the possibility effects of application in real-time a method for fast and sufficiently accurate definition of generator voltages to realize the favourable voltage-reactive states of electric power interconnection. In peak- load condition, this control is made to improve the economic operation, e.g. to reduce the active and reactive power losses. In low-load condition, this control is made to reduce the generator under-exitation states.
The development of this method is inspired by known fact of great influence of adequate choice of generator voltage on established voltage-reactive states. The verification of method proposed is made in context of steady-state and dynamic simulation model, on the example of realized and perspective states of Serbian transmission network.
The application in real time will be realised by state estimator, which is the part of the new SCADA/EMS system in NDC Elektromreza Srbije. The first practical experiences of the possibility of the application in real time, of the method proposed, has been established on the model of real interconnection, which consists of the EPSs of Serbia, Montenegro, Bosnia and Herzegovina, Hungary, Croatia, Macedonia, Romania, Bulgaria, Greece and Albania.
EFEKTI UPRAVLJANJA NAPONIMA GENERATORA U REALNOM VREMENU
U radu se izlaže sagledavanje mogućih efekata primene u realnom vremenu jedne metode za brzo i dovoljno tačno definisanje naponskih referenci generatora u cilju ostvarenja povoljnih naponsko-reaktivnih stanja elektroenergetskih interkonekcija. Tu se prvenstveno misli na poboljšanje ekonomije pogona u maksimalnim stanjima, odnosno smanjivanje gubitaka aktivne i reaktivne snage. U minimalnim stanjima, to se radi u cilju minimizacije po¬treba za potpobuđenim režimima rada generatora, odnosno njihovu raspodelu na generatore koji su najpogodniji za to.
Razvoj ove metode bio je podstaknut poznatim saznanjem o veoma značajnom uticaju adekvatnog izbora vrednosti naponskih referenci angažovanih generatora na uspostavljene naponsko-reaktivne prilike. Verifikacija metode je bila obavljena u okviru statičkog i dinamičkog simulacionog modela, na primerima ostvarenog i perspektivnih stanja prenosne mreže Srbije, u njenom širokom okruženju.
Primena u realnom vremenu bila bi omogućena posredstvom estimatora stanja koji se nalazi u sastavu novog SCADA/EMS sistema, implementiranom u Nacionalnom Dispečerskom Centru Elektromreže Srbije. Prva praktična iskustva u sagledavanju mogućnosti primene predložene metode u realnom vremenu, stečena su na modelu realne elektroenergetske interkonekcije koju sačinjavaju EES Srbije, Crne Gore, Bosne i Hercegovine, Hrvatske, Mađarske, Makedonije, Rumunije, Bugarske, Grčke i Albanije.
THE EFFECTS OF GENERATOR VOLTAGES CONTROL IN REAL TIME
ABSTRACT
This papers presents the possibility effects of application in real-time a method for fast and sufficiently accurate definition of generator voltages to realize the favourable voltage-reactive states of electric power interconnection. In peak- load condition, this control is made to improve the economic operation, e.g. to reduce the active and reactive power losses. In low-load condition, this control is made to reduce the generator under-exitation states.
The development of this method is inspired by known fact of great influence of adequate choice of generator voltage on established voltage-reactive states. The verification of method proposed is made in context of steady-state and dynamic simulation model, on the example of realized and perspective states of Serbian transmission network.
The application in real time will be realised by state estimator, which is the part of the new SCADA/EMS system in NDC Elektromreza Srbije. The first practical experiences of the possibility of the application in real time, of the method proposed, has been established on the model of real interconnection, which consists of the EPSs of Serbia, Montenegro, Bosnia and Herzegovina, Hungary, Croatia, Macedonia, Romania, Bulgaria, Greece and Albania.
