Thermal-hydraulics of evaporating tubes in the forced circulation loop of a steam boiler

Elektroprivreda Srbije je u toku 2005. godine nastavila radove na izgradnji TE Kolubara B snage 350 MW, koji su započeti još davne 1989. godine. Sam kotao je toranjske konstrukcije, a za isparivač kotla predviđeno je cirkulaciono kolo sa prinudnim strujanjem. Osim toga, ekranske cevi u ložištu su ožljebljene sa unutrašnje strane, što predstavlja jedinstveni slučaj u kotlovima termoelektrana u Srbiji. Da bi se izvršile termohidrauličke analize ovog isparivača urađeni su termički proračuni kotla, kao i hidraulički proračuni isparivača za različita radna opterećenja. U ovom radu prikazana je metodologija hidrauličkog proračuna isparivača sa prinudnom cirkulacijom. Na osnovu dobijenih rezultata, za spomenuti kotao, izvršena je analiza uticaja ožljebljenja cevi na povećanje hidrauličkog otpora u cirkulacionom kolu. S obzirom da ožljebljene cevi obezbeđuju sigurniji rad isparivača, održavajući nisku temperaturu zida cevi i pri visokim sadržajima pare, vršeno je njihovo upoređivanje sa glatkim cevima za slučajeve ravnomernog i neravnomernog toplotnog opterećenja u ložištu.Rifled evaporating tubes are applied in a steam boiler with the aim to increase the steam-water mixture turbulization and to prevent tubes' wall burnout. The evaporating rifled tubes and the working fluid forced circulation are applied in the steam boiler at the Thermal Power Plant 'Kolubara B' that is being built by the Electric Power Utility of Serbia. In order to investigate operating characteristics of the steam boiler of such an advanced design, a simulation and analysis of complex coupled thermal processes on the furnace gas side and thermal-hydraulics in the evaporating tubes were performed for the whole range of the plant designed operating loads. In this paper the methodology for the hydraulic calculations of forced circulation loops is presented. The rifled tubes thermal-hydraulics is calculated. An acceptable temperature of the evaporating tube wall, even under a high void fraction of the coolant is obtained. It is shown that the rifled tubes prevent the occurrence of the critical heat transfer conditions. The obtained increased thermal safety margin of the rifled tubes is compared with the safety margin of the smooth tubes for uniform and variable heat loads between walls of the boiler furnace. The influence of the rifled tubes on the increase of the hydraulic resistance in the circulation loop is analyzed

Thermal-hydraulics of evaporating tubes in the forced circulation loop of a steam boiler

Elektroprivreda Srbije je u toku 2005. godine nastavila radove na izgradnji TE Kolubara B snage 350 MW, koji su započeti još davne 1989. godine. Sam kotao je toranjske konstrukcije, a za isparivač kotla predviđeno je cirkulaciono kolo sa prinudnim strujanjem. Osim toga, ekranske cevi u ložištu su ožljebljene sa unutrašnje strane, što predstavlja jedinstveni slučaj u kotlovima termoelektrana u Srbiji. Da bi se izvršile termohidrauličke analize ovog isparivača urađeni su termički proračuni kotla, kao i hidraulički proračuni isparivača za različita radna opterećenja. U ovom radu prikazana je metodologija hidrauličkog proračuna isparivača sa prinudnom cirkulacijom. Na osnovu dobijenih rezultata, za spomenuti kotao, izvršena je analiza uticaja ožljebljenja cevi na povećanje hidrauličkog otpora u cirkulacionom kolu. S obzirom da ožljebljene cevi obezbeđuju sigurniji rad isparivača, održavajući nisku temperaturu zida cevi i pri visokim sadržajima pare, vršeno je njihovo upoređivanje sa glatkim cevima za slučajeve ravnomernog i neravnomernog toplotnog opterećenja u ložištu.Rifled evaporating tubes are applied in a steam boiler with the aim to increase the steam-water mixture turbulization and to prevent tubes' wall burnout. The evaporating rifled tubes and the working fluid forced circulation are applied in the steam boiler at the Thermal Power Plant 'Kolubara B' that is being built by the Electric Power Utility of Serbia. In order to investigate operating characteristics of the steam boiler of such an advanced design, a simulation and analysis of complex coupled thermal processes on the furnace gas side and thermal-hydraulics in the evaporating tubes were performed for the whole range of the plant designed operating loads. In this paper the methodology for the hydraulic calculations of forced circulation loops is presented. The rifled tubes thermal-hydraulics is calculated. An acceptable temperature of the evaporating tube wall, even under a high void fraction of the coolant is obtained. It is shown that the rifled tubes prevent the occurrence of the critical heat transfer conditions. The obtained increased thermal safety margin of the rifled tubes is compared with the safety margin of the smooth tubes for uniform and variable heat loads between walls of the boiler furnace. The influence of the rifled tubes on the increase of the hydraulic resistance in the circulation loop is analyzed

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

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

Technical solution for use of gas turbine exhaust gases in the existing steam boilers in MSK Kikinda

U okviru energetike Metanolsko-sirćetnog kompleksa u Kikindi nalaze se, pored procesnog kotla i ostale prateće opreme, tri jednaka parna kotla proizvodnje 'Minel-Kotlogradnja' koji su predviđeni za sagorevanje prirodnog gasa, mazuta i procesnih gasova. U cilju povećanja energetskog kapaciteta energane MSK Kikinda predviđena je ugradnja jedne gasne turbine snage 14 MW. S obzirom da izduvni gasovi iz gasne turbine imaju relativno visoku temperaturu i veliku količinu neiskorišćenog kiseonika iz vazduha, predviđeno je da se oni podele na dve jednake struje i da se uvedu u dva postojeća parna kotla produkcije od po 16,67 kg/s (60 t/h). Da bi se iskoristila ova toplota izduvnih gasova, kao i kiseonik sadržan u njima, neophodno je prvo zameniti postojeće gorionike i izvršiti neophodne rekonstrukcije grejnih površina u vertikalnom konvektivnom gasnom kanalu parnog kotla. Osim toga potrebno je proveriti da li postojeći ventilator za dimne gasove može da zadovolji novi režim rada pri kome se u jedan kotao uvodi polovina izduvnih gasova turbine. .Within the energy system in Methanol & Acetic acid Complex (MSK) in Kikinda, beside process boiler and auxiliary equipment, there are three identical steam boilers made by 'Minel Kotlogradnja', provided for combustion of natural gas, fuel oil, and process gases. To increase capacity of the power plant in MSK Kikinda, installation of one 14 MW gas turbine is planed. Since the exhaust gases are at the relatively high temperature and contain large quantity of oxygen, it is specified to split exhaust gas into two equal streams and introduce them into two existing steam boilers, each having production of 16,67 kg/s (60 t/h). In order to use heat as well as oxygen from the exhaust gases in the existing boilers, it is necessary to replace the existing burners and to reconstruct heat exchangers in the vertical convective gas channel. Besides, it is necessary to verify if the existing flue gases fan can comply with the new operating regime, during which a half of the turbine exhaust gas is introduced into the steam boiler.

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