Modeling of processes in utility steam boiler with air staging

Предмет истраживања представља развој прорачунског система који обухвата диференцијални математички модел процеса у ложишту и интегрални математички модел рада постројења са међусобним интеракцијама, а све у циљу процене рада енергетског парног котла у целини. Овакав систем омогућио је шири приказ свих релевантних стања струја које учествују у процесима енергетског парног котла на угљени прах. Потреба за оваквим начином истраживања проистекла је из чињенице да није могуће посматрати део сложеног постројења а притом занемарити његово садејство са остатком система у коме он функционише, односно са којим чини целину. Развијени метод је применљив за инверзне проблеме процене радног стања код постојећих постројења, као и за оне директне, како модификације постојећих тако и развоја нових енергетских објеката. У склопу развоја прорачунског система предвиђено је дефинисање математичког модела сагоревања честица угљеног праха, струјања и зрачења продуката сагоревања, као и подмодела формирања и деструкције азотних оксида који у корелацији са интегралним термичким и аеродинамичким прорачунима омогућавају формирање свеобухватног описа погонског режима енергетског парног котла. Развој оваквог прорачунског модела је значајан ради поузданог предвиђања перформанси енергетских парних котлова. Квалитет рада самог котла који је могуће проценити применом развијеног система прорачуна може се поделити у групе ефективног, ефикасног, сигурног и еколошки прихватљивог рада. Оваква анализа нарочито је битна с обзиром да рад котла може имати пресудан утицај на расположивост и економичност целокупног енергетског система чија је он компонента...The subject of research is the development of a calculation system comprising a differential mathematical model of processes within the furnace and an integral mathematical operation model of plant with mutual interactions, with the aim of overall utility steam boiler operation assessment. Such system enabled a wider overview of all relevant flows involved in the processes of the utility steam boiler operating on pulverized coal. The need for such research originated from the fact that it is not possible to observe a part of a complex plant and disregard its joint action with the rest of the system, with which it forms a whole. The developed method is applicable to inverse problems of operation mode assessment at existing plants, as well as to direct problems both for modification of existing and development of new utility objects. Within the development of the programme system, it has been anticipated to define a mathematical model of pulverized coal particles combustion, flow and radiation of two-phase gas-particles mixture, as well as a submodel of nitrogen oxides formation and destruction, which, in correlation with integral thermal and aerodynamic calculations, allow the formation of a comprehensive description of the utility steam boiler operating regime. The development of such a calculation model is significant in the aim of reliable prediction of utility steam boilers’ performances. The operation quality of boilers that may be assessed by using the developed calculation system can be divided into groups of effective, efficient, safe and ecologically acceptable work. Such analysis is of particular importance due to the fact that boiler operation can have a decisive impact on the availability and cost of the entire energy conversion system of which it is a component..

Work verification of the energy steam boiler evaporator in the Power plant 'Kostolac B'

U okviru Elektroprivrede Srbije 1991. godine puštena je u rad Termoelektrana 'Kostolac B' snage 2 × 350 MW. Na osnovu dosadašnjih ispitivanja cevnog sistema parnog kotla utvrđeno je da se on nalazi u 'lošem' stanju. Njegovi najugroženiji delovi su isparivačke grejne površine. S obzirom da postoje oblasti u isparivaču koje su se češće oštećivale, zbog čega je parni kotao ispadao iz pogona, neophodno je utvrditi razloge zbog kojih je dolazilo do tih oštećenja. Da bi se locirala ugrožena područja isparivača, sproveden je detaljan hidraulički proračun. Takođe je izvršen termički proračun parnog kotla u celini, s obzirom da se isparivač nalazi i u zoni konvektivnih grejnih površina. Utvrđivanjem najugroženije lokacije isparivača - horizontalni deo nosećih cevi, omogućeno je da se pri kapitalnom remontu izvrše određene rekonstrukcije u smislu promene njihovog ugla nagiba, što bi u krajnjem obezbedilo sigurniji rad, kako isparivača tako i kotla u celini.Within Electric Power Utility of Serbia 1991, a thermal power plant 'Kostolac B', power 2 × 350 MW, started. Based on the examination of steam boiler pipe system, it is confirmed that it is in a 'bad' shape. Its most jeopardized parts are evaporating heating surfaces. Considering that there are areas within the evaporator that suffered more damage, wherefore the steam boiler is out of production, it is necessary to settle the reasons for those damages. In order to locate the jeopardized areas of the evaporator, we carried out a detailed hydraulic calculation. A thermal calculation of steam boiler was also carried out, considering that the evaporator is also located in the convective heating surfaces part. By settling the most jeopardized evaporator locations - a horizontal part of support tubes, it was enabled to make certain reconstructions during the capital repair, in regard of changing their inclination angle, which would provide safer work of the evaporator, and steam boiler as a whole

Impact of air stagging in furnace on processes in power steam boiler TPP Kostolac B

U cilju dostizanja propisanih normi koncentracije azotnih oksida za velika ložišta na ugalj od 200 mg/Nm3 (u suvim gasovima na 6% O2) u termoelektrani Kostolac B, 2015. godine, primenjena je primarna mera višestepenog dovođenja vazduha po visini ložišta. U radu je prikazana analiza efekata modernizacije na rad parnog kotla u celini, proračunskim sprezanjem diferencijalnih matematičkih modela procesa sagorevanja čestica ugljenog praha, strujanja i zračenja produkata sagorevanja, kao i formiranja azotnih oksida sa integralnim termičkim i aerodinamičkim proračunskim procedurama. Ovakav proračunski sistem omogućava pouzdano predviđanje radnih karakteristika energetskih parnih kotlova i u uslovima neprojektnog - podstehiometrijskog sagorevanja. Primenom ovakvog pristupa kvalitet rada samog kotla moguće je proceniti sa aspekta efektivnog, efikasnog, sigurnog i ekološki prihvatljivog načina rada. Na osnovu navedenog izvršeni su proračuni parnog kotla bloka 1 TE Kostolac B za postojeći i reorganizovani sistem sagorevanja. U radu je prikazan uticaj većeg broja parametara na rad parnog kotla sa izvedenim konceptom primarnih mera.The European normatives prescribe the maximum content of 200 mg/Nm3 in dry flue gases with oxygen content of 6% for existing pulverized coal-fired power plants. In order to analyse the effects of applying some of the primary measures for NOx reduction on the overall steam boiler operation, calculational coupling of differential mathematical models has been applied. This calculation system enables reliable prediction of the performance of power steam boilers also in substoichiometric conditions, and the quality of the boiler operation can be described from the perspective of its effective, efficient, safe and ecological operation. In accorrdance to that, calculations of the steam boiler unit 1 TE Kostolac B have been carried out for the existing and the air staging combustion system. This paper presents an analysis of the influence of various parameters on the operation of the steam boiler with the application of primary measures

Impact of air stagging in furnace on processes in power steam boiler TPP Kostolac B

U cilju dostizanja propisanih normi koncentracije azotnih oksida za velika ložišta na ugalj od 200 mg/Nm3 (u suvim gasovima na 6% O2) u termoelektrani Kostolac B, 2015. godine, primenjena je primarna mera višestepenog dovođenja vazduha po visini ložišta. U radu je prikazana analiza efekata modernizacije na rad parnog kotla u celini, proračunskim sprezanjem diferencijalnih matematičkih modela procesa sagorevanja čestica ugljenog praha, strujanja i zračenja produkata sagorevanja, kao i formiranja azotnih oksida sa integralnim termičkim i aerodinamičkim proračunskim procedurama. Ovakav proračunski sistem omogućava pouzdano predviđanje radnih karakteristika energetskih parnih kotlova i u uslovima neprojektnog - podstehiometrijskog sagorevanja. Primenom ovakvog pristupa kvalitet rada samog kotla moguće je proceniti sa aspekta efektivnog, efikasnog, sigurnog i ekološki prihvatljivog načina rada. Na osnovu navedenog izvršeni su proračuni parnog kotla bloka 1 TE Kostolac B za postojeći i reorganizovani sistem sagorevanja. U radu je prikazan uticaj većeg broja parametara na rad parnog kotla sa izvedenim konceptom primarnih mera.The European normatives prescribe the maximum content of 200 mg/Nm3 in dry flue gases with oxygen content of 6% for existing pulverized coal-fired power plants. In order to analyse the effects of applying some of the primary measures for NOx reduction on the overall steam boiler operation, calculational coupling of differential mathematical models has been applied. This calculation system enables reliable prediction of the performance of power steam boilers also in substoichiometric conditions, and the quality of the boiler operation can be described from the perspective of its effective, efficient, safe and ecological operation. In accorrdance to that, calculations of the steam boiler unit 1 TE Kostolac B have been carried out for the existing and the air staging combustion system. This paper presents an analysis of the influence of various parameters on the operation of the steam boiler with the application of primary measures

Detection of cause of pipe burst in economizer of process CO steam boiler

U radu su prikazani rezultati analize rada procesnog parnog kotla sa maksimalnom kontinualnom produkcijom pare od 75 t/h pritiska 45,5 bar i temperature 412 oC. Predmetni kotao je deo postrojenja za proizvodnju pare u Rafineriji nafte u Pančevu, Srbija. Prema zahtevu naručioca predviđeno je da kotao radi sa više vrsta goriva kao i sa dve ili tri vrste goriva istovremeno. Pristupnim instalacijama u ložište je moguće dovesti rafinerijski gas, ložno ulje kao i otpadni gas visoke temperature. Otpadni gas se u kotao dovodi iz postrojenja za katalitički kreking (eng. FCC - Fuel catalyst cracking) i predstavlja dvokomponentu mešavine gasne faze i polidisperznih čestica prečnika ne većeg od 40 µm. Skorije promene u proizvodnji pare u rafineriji dovele su do potrebe za modifikacijom radnog režima kotla, odnosno, do modifikacije njegovih radnih parametara. Trenutno, u novim radnim uslovima, u toku rada kotla dešavaju se učestala pucanja cevi na zagrejaču vode što zahteva momentalni prekid proizvodnje pare kao i sprovođenje vremenski i finansijski zahtevanih postupaka u cilju otklanjanja uzroka zastoja i nastavka rada parnog kotla. U ovom radu predstavljeni su rezultati termičkog proračuna predmetnog kotla za projektne i nove uslove rada u cilju identifikacije uzroka učestalih neplankih zastoja u proizvodnji pare. Nakon izvršene analize rezultata proračuna date su preporuke u vezi modifikacije radnih parametara u cilju eliminisanja ili smanjivanja mogućnosti za pojavu neželjenih efakata na zagrejaču vode.In this paper results of analysis of process steam boiler operation with maximum continuous steam production of 75 t/h, steam pressure and temperature of 45,5 bar and 412 oC are presented. Steam boiler is predicted to operate within steam production facility of oil and gas refinery in Pancevo, Serbia. On the demand of purchaser steam boiler is enabled to operate with various fuels as well as with two or three fuels simultaneously. By fuels intake facilities it is enabled to introduce refinery gas, fuel oil and high-temperature waste gas to the boilers furnace. Waste gas is guided from FCC (Fuel catalyst cracking) facility and presents two-component fluid with polydisperse solid phase composed of particles of diameter smaller than 40 µm. Recent changes in steam consumption in refinery resulted in modifications in boiler's operating regime and, further on, in significant changes in its operational parameters. At present, in new conditions, boiler operates with frequent pipe bursts on pipe bundles of boiler economizer which requires forced interruption in steam production as well as time and cost consuming operations for resuming boiler work. In this paper results of thermal calculations for design and new operational conditions are presented for the purpose of identification of cause of frequent unscheduled steam production interruptions. After analysis of presented results, recommendations on how to modify certain boiler operational parameters in order to eliminate or reduce possibility of such unfavourable occurance has been provided

Reconstruction of the aero-mixture channels of the pulverized coal plant of the 100 MW power plant unit

After the last revitalization of thermal power block of 100 MW in TPP 'Kostolac A', made in the year 2004, during the operation of the plant, pulverized coal deposition often occurred in horizontal sections of the aero-mixture channels. Deposition phenomenon manifested itself in places ahead of spherical compensators in the direction of flow of pulverized coal to the burners, due to unfavorable configuration of these channels. Coal dust deposited in the channels dried and spontaneously combusted, causing numerous damage to channels and its isolation as well as the frequent stoppage of the operation for necessary interventions. The paper presents the original solution of reconstruction of aero-mixture channels which prevented deposition of coal dust and its eventual ignition. In this way the reliability of the mill plant is maximized and higher availability of boiler and block as a whole is achieved

Air staging application effects on overall steam boiler operation

This paper presents the results of calculation system of main processes in power steam boiler, before and after application of air staging. Modified air injection scheme was implemented during 2015 on the power steam boiler within unit 1 of TPP Kostolac B. Measurements performed on site showed that applied reconstruction led to a permanent loss of the steam boiler power. This study was performed in order to define the cause of such an occurrence and to consider the possibility for regaining the designed steam parameters along with keeping NOx concentration in prescribed limits. This paper discusses the influence of repositioning the air injection location on processes within the furnace. Furthermore, the influence of the redistribution of injected air-flow along the furnace height on important boiler operation parameters has been analyzed. Analysis showed that, with appropriate dosing of air along the height of the existing furnace, it is possible to achieve the optimum of the boiler's operation parameters. Results of research showed that air staging throughout the furnace height in best test case additionally reduces NO concentration (195-225 mg/Nm(3)) and increases the power of x considered boiler (828.8-751.1 MW) with an insignificant decrease of the boiler's efficiency (86.27-86.77%). Furthermore, the designed temperatures of superheated (540-498 degrees C) and reheated (540-518 degrees C) steam have been reached again, whereby the safety of the boiler's operation has been significantly increased. Results of this study improve the present explanation of the processes occurred in the furnace with applied primary measures. They also give directions on defining the most influential parameters on considered processes with the final purpose to increase the efficiency and availability of the entire plant

Air staging application effects on overall steam boiler operation

This paper presents the results of calculation system of main processes in power steam boiler, before and after application of air staging. Modified air injection scheme was implemented during 2015 on the power steam boiler within unit 1 of TPP Kostolac B. Measurements performed on site showed that applied reconstruction led to a permanent loss of the steam boiler power. This study was performed in order to define the cause of such an occurrence and to consider the possibility for regaining the designed steam parameters along with keeping NOx concentration in prescribed limits. This paper discusses the influence of repositioning the air injection location on processes within the furnace. Furthermore, the influence of the redistribution of injected air-flow along the furnace height on important boiler operation parameters has been analyzed. Analysis showed that, with appropriate dosing of air along the height of the existing furnace, it is possible to achieve the optimum of the boiler's operation parameters. Results of research showed that air staging throughout the furnace height in best test case additionally reduces NO concentration (195-225 mg/Nm(3)) and increases the power of x considered boiler (828.8-751.1 MW) with an insignificant decrease of the boiler's efficiency (86.27-86.77%). Furthermore, the designed temperatures of superheated (540-498 degrees C) and reheated (540-518 degrees C) steam have been reached again, whereby the safety of the boiler's operation has been significantly increased. Results of this study improve the present explanation of the processes occurred in the furnace with applied primary measures. They also give directions on defining the most influential parameters on considered processes with the final purpose to increase the efficiency and availability of the entire plant

ASSESSING THE IMPACT OF SPECIFIC WEIGHT OF DIFFERENT-SIZED PARTICLES ON OPERATIONAL PERFORMANCE OF COAL PREPARATION PLANT

In case of firing pulverized coal in power steam boiler certain fuel preparation process has to be taken in order to ensure stable and optimal combustion in boil-er furnace. Before entering furnace low caloric coal is introduced from coal bun-ker to the coal preparation system where milling/pulverization and drying pro-cesses of raw large coal particles are conducted. For the purpose of defining fineness of grinding of pulverized coal mill gaseous mixture at mill outlet is in-troduced to the separator where large coal particles, separated from outgoing mill gaseous mixture, are recirculated to mill for regrinding. In this paper char-acter of two-phase flow in inertial separator at milling plant in TPP Nikola Tesla Unit B under various operating conditions has been analyzed. The CFD ap-proach has been used for calculating two-phase flow in separators flow domain. Measurement data taken on site along with results of performed heat balance calculations of milling plant have been used for validating calculation model as well as for setting appropriate boundary conditions in CFD model. The CFD cal-culations has been performed for different positions of all regulating flaps, recir-culation rates of gaseous phase and values of specific weight of solid phase in two-phase mixture. For evaluating separators operating performance at different operating regimes changes of milling capacity and fineness of grinding of pulver-ized coal at separators outlet have been observed. Additionally, deviation rate of trajectories of different-sized particles to the streamlines of gaseous phase has been examined

NUMERIČKA SIMULACIJA KRETANJA ČESTICA UGLJENOG PRAHA PRILIKOM NAPUŠTANJA MLINSKOG SEPARATORA KROZ KANAL AEROSMEŠE

U radu su prikazani rezultati numeričke simulacije kretanja čestica ugljenog praha prilikom napuštanja mlinskog inercijalnog separatora i ulaza u kanal aerosmeše. Korišćeni geometrijski model u simulacijama obuhvata inercijalni separator ugljenog praha i deo kanala aerosmeše u kome je analizirano strujanje dvokomponentne mešavine. Model separatora identičan je inercijalnom separatoru ventilatorskog mlina N 400.42 koji je sastavni deo postrojenja za pripremu ugljenog praha u termoelektrani "Nikola Tesla" B. Kanal aerosmeše predstavlja sledeći element nakon inercijalnog separatora kroz koji struji aerosmeša. U korišćenom geometrijskom modelu površina i oblik poprečnog preseka kanala konstantni su na celoj njegovoj dužini i identični su izlaznom poprečnom preseku inercijalnog separatora. Ovakva koncepcija odgovara novijim konstrukcijama kanala koje se ugrađuju prilikom rekonstrukcije postojećih višeetažnih gorionika u cilju ugradnje gorionika sa niskom emisijom azotnih oksida nakon sagorevanja. Za potrebe proračuna strujanja dvokomponentne mešavine korišćen je kombinovani Oiler – Lagrange pristup. Oiler-ov pristup i k-ε turbulentni model korišćeni su za modeliranje strujanja gasne faze dok su trajektorije čestica ugljenog praha različitih frakcija sračunate primenom Lagrange-ovog DPM (Discrete Phase Model) modela. Za potrebe definisanja graničnih uslova analiziranog strujnog prostora korišćena su merenja izvršena na realnom modelu inercijalnog separatora u eksploataciji. Dostupna merenja izvršena su u izlaznom poprečnom preseku predmetnog separatora pri jednom određenom položaju tri regulacione klapne. Raspored čestica u ulaznom poprečnom preseku separatora (izlazu iz mlina) variran je sve do postizanja poklapanja granulometrijske karakteristike ugljenog praha u izlaznom poprečnom preseku sa pomenutim merenjima. Nakon postizanja poklapanja sa rezultatima merenja izvršenim na separatoru u eksploataciji u daljim simulacijama variran je položaj dve regulacione klapne: nezavisne klapne postavljene ispod plafona separatora a ispred „kragne“ izlaznog kanala i tri regulacione klapne vezane za zajednički pokretni mehanizam i postavljene u prelaznom, horizontalnom kanalu separatora. Analizirano je strujanje aerosmeše za više različitih položaja svake od pomenutih klapni. Nakon toga, razmatrano je kretanje čestica ugljenog praha različitih dimenzija u izlaznom prostoru separatora i ulazu u kanal aerosmeše. Dodatno, izvršena je analiza rasporeda čestica različitih dimenzija u dva poprečna preseka po visini dela kanala za aerosmešu. Izvedeni zaključci na osnovu dobijenih rezultata mogu doprineti boljem uvidu u kretanje ugljenih čestica različitih dimenzija prilikom napuštanja separatora. Takođe, oni se mogu iskoristiti u cilju poboljšanja procesa razdvajanja frakcija čvrste faze u individualnim modifikovanim sistemima za pripremu ugljenog praha sa direktnim uduvavanjem kao i u kotlovima sa višeetažnim gorionicima