Corrosion in Alloy WFGD Absorber Reaction Tanks

摘要

Unexpected aggressive corrosion has been observed in alloy wet flue gas desulfurization (FGD) absorber reaction tanks industry-wide. Babcock & Wilcox Power Generation Group, Inc. (B&W PGG) has conducted research on the potential causes of this corrosion, associated process chemistry implications, and development of a test methodology to assess suitability of materials in the wet FGD environment. A primary cause of corrosion appears to be fluoride-induced under-deposit attack. Additionally, highly oxidative environments within some absorbers cause manganese in the slurry to precipitate as manganese oxide, thereby creating a galvanic effect which appears to greatly exacerbate the under-deposit attack mechanism. Various process chemistry parameters that influence manganese deposition also have implications on mercury, selenium and other trace metal phase partitioning, and on acid gas emissions. Presented in this paper are analytical data and results from various process slurries and deposits from operating units, and laboratory data from tests that recreate the observed reaction tank corrosion and predict the behavior of candidate alloys.