TY - JOUR
T1 - Impact of boiler load and limestone addition on SO3 and corrosive cold-end deposits in a coal-fired CFB boiler
AU - Vainio, Emil
AU - Vänskä, Kyösti
AU - Laurén, Tor
AU - Yrjas, Patrik
AU - Coda Zabetta, Edgardo
AU - Hupa, Mikko
AU - Hupa, Leena
N1 - Funding Information:
This work has been carried out within the industrial consortium in Åbo Akademi University combustion research supported by the companies: Andritz Oy, Valmet Technologies Oy, Amec Foster Wheeler Energia Oy, UPM-Kymmene Oyj, Clyde Bergemann GmbH, International Paper Inc., and Top Analytica Oy Ab. Support from the National Technology Agency of Finland (Tekes) and Academy of Finland (Decision No. 289869 and 333917) is gratefully acknowledged.
Funding Information:
This work has been carried out within the industrial consortium in ?bo Akademi University combustion research supported by the companies: Andritz Oy, Valmet Technologies Oy, Amec Foster Wheeler Energia Oy, UPM-Kymmene Oyj, Clyde Bergemann GmbH, International Paper Inc. and Top Analytica Oy Ab. Support from the National Technology Agency of Finland (Tekes) and Academy of Finland (Decision No. 289869 and 333917) is gratefully acknowledged.
Publisher Copyright:
© 2021
PY - 2021/11/15
Y1 - 2021/11/15
N2 - The risk of cold-end corrosion caused by two different phenomena was studied: the well-known sulfuric acid-induced corrosion and corrosion caused by hygroscopic fly ash deposits. Measurements were performed in a full-scale circulating fluidized bed boiler firing bituminous coal with high contents of sulfur and chlorine. The boiler was run both with and without limestone addition to reveal the effects of limestone on corrosion. Furthermore, the impact of boiler load on corrosion and deposit composition was studied. Corrosion probe, SO3, and dew point measurements were performed up- and downstream of the electrostatic precipitator. Ash deposits were collected from the different sides of the corrosion probe and were analyzed. The formation of SO3 was low in all cases (<0.1 ppmv), which was connected to the relatively low furnace temperature in fluidized bed combustion and the efficient SO3 capturing of the fly ash and limestone. The different operational parameters of the boiler had a significant impact on deposit composition and on expected corrosion risk. At full load and without limestone addition, the chlorine of the fuel stayed as gaseous HCl, whereas no Cl was found in the deposits. However, when limestone was added, corrosion was caused by the presence of deliquescent calcium chloride. At low load operation of the boiler, ammonium chloride was formed on the cold-end deposit probe. Ammonium chloride was formed via the reaction between HCl and NH3 in the cooling flue gases. Laboratory studies with NH4Cl was further conducted to assess its corrosivity.
AB - The risk of cold-end corrosion caused by two different phenomena was studied: the well-known sulfuric acid-induced corrosion and corrosion caused by hygroscopic fly ash deposits. Measurements were performed in a full-scale circulating fluidized bed boiler firing bituminous coal with high contents of sulfur and chlorine. The boiler was run both with and without limestone addition to reveal the effects of limestone on corrosion. Furthermore, the impact of boiler load on corrosion and deposit composition was studied. Corrosion probe, SO3, and dew point measurements were performed up- and downstream of the electrostatic precipitator. Ash deposits were collected from the different sides of the corrosion probe and were analyzed. The formation of SO3 was low in all cases (<0.1 ppmv), which was connected to the relatively low furnace temperature in fluidized bed combustion and the efficient SO3 capturing of the fly ash and limestone. The different operational parameters of the boiler had a significant impact on deposit composition and on expected corrosion risk. At full load and without limestone addition, the chlorine of the fuel stayed as gaseous HCl, whereas no Cl was found in the deposits. However, when limestone was added, corrosion was caused by the presence of deliquescent calcium chloride. At low load operation of the boiler, ammonium chloride was formed on the cold-end deposit probe. Ammonium chloride was formed via the reaction between HCl and NH3 in the cooling flue gases. Laboratory studies with NH4Cl was further conducted to assess its corrosivity.
KW - CaCl
KW - Cold-end corrosion
KW - HSO
KW - Hygroscopic deposits
KW - NHCl
KW - SO
UR - http://www.scopus.com/inward/record.url?scp=85112829716&partnerID=8YFLogxK
U2 - 10.1016/j.fuel.2021.121313
DO - 10.1016/j.fuel.2021.121313
M3 - Article
AN - SCOPUS:85112829716
SN - 0016-2361
VL - 304
JO - Fuel
JF - Fuel
M1 - 121313
ER -