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Mechanistic aspects of carburization in oil‐fired power plants
Author(s) -
LópezLópez D.,
WongMoreno A.,
TeranSarabia A.,
VelascoTellez A.,
Martínez L.
Publication year - 1998
Publication title -
materials and corrosion
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.487
H-Index - 55
eISSN - 1521-4176
pISSN - 0947-5117
DOI - 10.1002/(sici)1521-4176(199804)49:4<272::aid-maco272>3.0.co;2-9
Subject(s) - boiler (water heating) , metallurgy , superheater , materials science , decarburization , corrosion , combustion , coal , waste management , chemistry , engineering , organic chemistry
Abstract Materials degradation due to surface carburization has been recently reported in connection to failures or high corrosion rates of superheaters or reheater tubes of oil‐fired and coal‐fired boilers. Reducing conditions to explain carburization process of materials are hardly to expect because fuel is burned with oxygen excess to attain its complete combustion. The formation of sodium carbonate as a carburization catalyst has been proposed in order to explain carburization phenomenon in boilers, however this carburization catalyst has been rarely found in ash deposits on carburized tubes. In order to study the role of some compounds present in boiler deposits as possible carburization catalysts and the corrosion behavior of 304H‐type stainless steel in boiler deposits under reducing conditions, pack‐carburization experiments were carried out at 650°C by 1000 hours. Mixtures of 60 wt.% carbon and 40 wt. % of different typical compounds of boiler tube deposits were used. The experimental results show that ash deposits and several deposit compounds act as carburization enhancers, they increase carburization of the alloy if carbon is present in ash deposits. Furthermore, corrosion were detected in some cases. However, other mechanisms might be considered to explain carburization of boiler steels. Analysis of these mechanisms is presented. It is concluded that surface deposition of partially burned particles and its further burning supplying carbon monoxide to the local atmosphere is considered as the main mechanism contributing to carburization of boiler tubes.