Numerička optimizacija procesa u ložištu sa aspekata emisije NOx i efikasnosti energetskog kotla

Abstract

Razvijen je matematički model, namenjen za predviđanje procesa u energetskim parnim kotlovima TE Kostolac B tangencijalno loženim sprašenim lignitom. Model je primenjen za numeričku analizu rada kotla radi smanjenja emisije NOx, uz istovremeno održavanje visokog stepena korisnosti kotla. Kompleksni dvofazni tok gas-čestice modeliran je Ojler-Lagranževim pristupom. Povezivanje faza je ostvareno kuplovanjem pomoću PSI-Cell koncepta. Radi ostvarivanja željenih analiza, ugrađen je pod-model formiranja/destrukcije NO, unutar složenog koda za sagorevanje, koji se koristi za predviđanje emisije na izlazu iz ložišta. Modelirani su termički i gorivi NO, kao najuticajniji oksidi azota pri sagorevanju ugljenog praha. Proračunski program je razvijen radi lakše upotrebe od strane inženjerskog osoblja prilikom analiza procesa u kotlovskim postrojenjima. Numeričke simulacije su izvršene za različite radne uslove kotla, prilikom loženja lignitom sa kopa Drmno. Suprotstavljeni zahtevi a smanjenjem emisije i efikasnim sagorevanjem, sa osvrtom na bezbedan rad pregrejača pare često zahtevaju rad kotla u uskim granicama radnih parametara, koji su utvrđeni pomoću termičkog proračuna kotla.

Mathematical model, aimed for prediction of processes in TE Kostolac B power plant utility boiler furnace tangentially fired by pulverized lignite, was developed in-house. The model was applied in numerical analysis of boiler operation, in order to reduce NOx emission by combustion modifications in the furnace, while maintaining high efficiency of the boiler unit. Complex two-phase gas-particle flow was modelled using Euler-Lagrange approach. Coupling between phases was done by using PSI-Cell concept. In order to perform necessary analysis, NO formation/destruction sub-model was implemented, within comprehensive combustion code, used to predict emission from the furnace. Thermal and fuel NO were modelled, as the most influential nitrogen oxides during pulverized coal combustion process. The computational code was developed to be easily used by engineering staff dealing with the process analysis in boiler units. Numerical simulations were performed for the boiler fired by the lignite Drmno, under different operating conditions. Contradictory requirements with respect to emission reduction and efficient combustion with safe operation of super-heaters often require boiler to operate within narrow limits of operation parameters, which is determined by means of the boiler thermal calculation.