Termohidraulika cevnih sistema kotlova na blokovima B1 i B2 termoelektrane “Nikola Tesla B”

Abstract

U okviru projekta povećanja snage blokova B1 i B2 na Termoelektrani „Nikola Tesla B“ izvršena je analiza promene pritiska u cevnim sistemima kotlova. Izmerene vrednosti pokazuju značajno veći pad pritiska na oba bloka od projektom predviđenih vrednosti. Stoga su izvršeni proračuni i analize strujanja vode i vodene pare u cevnim sistemima kotlova, od ulaza napojne vode u ekonomajzer, do izlaza sveže pare iz kotla, za projektne uslove rada i nominalnu produkciju pare, kao i za sadašnje termičke i hidrauličke uslove pogona kotlova i različita opterećenja. Utvrđena su značajna povećanja hidrauličkih otpora u odnosu na projektom definisane uslove duž celog cevnog sistema: počev od ekonomajzera, zatim kroz spusne cevi napojne vode i isparivačke cevi do separatora, kao i od separatora, kroz liniju pregrevanja sveže pare do izlaza iz poslednjeg pregrejača pare. Sprovedeni spregnuti termički i hidraulički proračuni daju detaljan uvid u promenu pritiska i temperature radnog fluida u cevnom sistemu kotla za različita opterećenja bloka. Određene su zavisnosti pritisaka radnog fluida na karakterističnim mestima u cevnom sistemu kotla u zavisnosti od snage bloka pri radu sa obe i jednom linijom zagrejača visokog pritiska, kao i maksimalna moguća opterećenja parnih blokova. Analiziran je uticaj termičkih i hidrauličkih uslova na povećanje pada pritiska u cevnom sistemu.

The analysis of pressure changes in tube systems of the steam boilers in Thermal Power Plant “Nikola Tesla B” has been performed within the project of power increase of Units B1 and B2. Measured pressure values have shown much higher pressure drops than design values at both Units. Therefore, the predictions and analyses of the water and steam flows have been performed for the boilers’ tube systems, from the feedwater inlet at the economizer till the live steam outlet from the boiler, for the nominal design operation and steam generation rate, as well as for the present thermal and hydraulic conditions of boilers’ operation at various loads. Substantial hydraulic resistances have been indicated compared to the design conditions along the whole tube system, starting from the economizer, than through the feedwater downcomer tubes and evaporating tubes till the separator, and than from the separator, through the steam superheating line till the steam outlet from the last superheater. The conducted coupled thermal and hydraulic calculations provide detailed insight in the working fluid pressure and temperature change in the boiler tube system under various loads. The pressure dependence on the Unit power has been predicted for the characteristic points at the boiler tube system and under operation with one and two lines of the high pressure feedwater heaters. The maximal boilers loads have been predicted too. The influence of thermal and hydraulic conditions on the increase of the pressure drop has been analyzed.