| OCR Text |
Show Ansaldo Energia s.p.a. The very good mixing performance of the installed post-combustion air (OFA) injection system allows the attainment of pollutant emission levels below the target in a "pure air staging mode" for boiler loads lower than 7 5 % M C R . Figs. 21 and 22 outline the most interesting test results. 'V 11 • PPC KCKATtMl l/nrt I . lit M W. |HO»U IS 1 • v v . • • ( • , • »*.» • " • /--".". a ' a a ax -TOO "i -600 1^ oo 300 • 100 -0 .NOi BB 15* OFA » » 2c . N O K RO • NCkFIB • cone oCORB OCORB 11% OFA ool Jp i nt O F A on 3p SSOFApr* 2c I«OFA0Ol2p r«OFA0|>3c F\.a-ITCMBRATmilMat - ItfUW, _ jsac J _ _ !i_ _ I I • i ----" n ' ; ; ; . " • • • • « » « ' ' " I I I . -,-;-• , <LA ' * 1 1 1 1 1 •NO. U 11* • » , » « AODfll n. OOP Of A Cassano 2 This 320 MWe natural circulation, box type boiler, manufactured by Ansaldo Breda and operating since 1983, has a pressurized furnace and was equipped with 18 barrel type burners (3 rows of 3, front and rear) oil and gas fired. The pollutant emission targets set by the Customer for this unit ( N O x < 190 mg/Nm3 in oil firing, < 170 mg/Nm3 in gas firing) take into account a "bubble" criterion according to which the "stack average" N O x emission of unit 1 & 2 (see previous description of unit 1, averaging 220 4- 225 mg/Nm3 in oil firing) has to be achieved in compliance with the law limit. Being the A E M pollutant emission strategy based on the same approach of E N E L (in-furnace control and proper fuel selection) a gas reburn system has been designed and installed, making use of extensive C F D modeling and leading to a slightly simpler arrangement (5+5 Reb. injectors, 4+4 OFA's - see fig. 23). i • oao •**<* OPPOWl - B UNrr aon-armofrr cotasumoN rrrreu eotmaimxnoH LEmocwau paoarr»a*aawau* •JOMT ajocwAii. + + + + + + + + + + + + + + + I + + + + + + + Fig. 23 - AEM Cassano #2 - 320 MWe Opposite Fared Unit Post-retrofit Combustion System Configuration Existing burners have been replaced with new T E A M K 2 low N O x burners, without any need for pressure parts modification in the burners area. Fig. 24 shows a simplified isometric view of the overall layout (only front burners' windbox and left side OFA's are reported, for better clarity). The unit has come back to commercial operation since several months, and optimization tests are still ongoing mainly due to low sulphur fuel oil availability problems. Fig. 24 - Isometric view of the combustion system implemented at Cassano 2 -10- |
