Influence of Sulfation-Enhancement Salt Additives on the Corrosion Behavior of Materials in Atmospheric Fluidized-Bed Combustors

摘要

Increased utilization of CaO can reduce the amount of limestone required for SO sub 2 retention in atmospheric fluidized-bed combustion (AFBC) systems. A recently developed method of improving the utilization involves treating the limestone with various salts, such as NaCl, CaCl sub 2 , or Na sub 2 CO sub 3 . The present report provides information on the influence of these sulfation-enhancement salt additives on corrosion of candidate structural materials for AFBC systems. Four 100-h and two 1000-h corrosion test runs were conducted in a 152-mm-ID fluidized-bed coal combustor. In each run, three air-cooled corrosion probes and four uncooled corrosion coupon holders, each with seven specimens, were installed at various locations in the fluidized bed and freeboard sections of the combustor. The temperature of the corrosion specimens ranged from 400 to 850 exp 0 C. As controls, some of the runs were made without any salt additions. The results indicate that the presence of salt has no effect on the corrosion behavior of the various iron- and nickel-base alloys that were placed in the freeboard section of the combustor. Although the uncooled alloys within the fluidized bed do undergo oxidation/sulfidation corrosion, the addition of CaCl sub 2 does not further affect the corrosion rate; the addition of NaCl or Na sub 2 CO sub 3 increases the corrosion rates for the high-nickel alloys, but not for the stainless steels. The observed corrosion rates for all of the alloys from within the fluidized bed containing approximately 2 mol % CaCl sub 2 or Na sub 2 CO sub 3 are in good agreement with the rates reported in other similar studies without salt additions. The corrosion data and a metallographic evaluation of the corrosion specimens are presented.