A laboratory study of the corrosion behaviour of Alloys exposed in a non‐equilibrated coal gasification atmosphere at 600°C

摘要

AbstractThe ability of alloys to resist corrosion during exposure to high temperature process atmospheres is one of the primary factors governing their selection in the manufacture of components such as heat exchangers in coal conversion plant. In particular, sulphidation attack in the low oxygen‐containing environments often encountered in such plant can pose significant problems.Many laboratory studies have been carried out over the years in gases simulating those found in coal gasifiers but these experiments have almost always utilised equilibrated gas mixtures in which the activities of the principal reactants, S, O and C were known and controlled. In many industrial situations, however, the combustion gases are quenched from very high temperatures, e.g. 1200–1400°C before coming in contact with the much cooler heat exchanger tube surfaces and therefore chemical equilibration between the gaseous constituents does not have time to occur.This paper presents results from a study concerned with the corrosion behaviour of candidate heat exchanger alloys exposed to a CO‐rich, non‐equilibrated gas mixture of the type found in a dryfeed entrained slagging gasifier. Data on three selected alloys, i. e. HR 3C (a chromia‐former), MA 956 (an alumina‐former) and HR 160 (a silica‐former) exposed at 600°C are reported. The kinetics and mechanisms of corrosive degradation are described for test durations of up to 2000 hours. Significant differences in corrosion rate and in the depths of metal loss exhibited by these alloys were observed. Alloy HR 160, containing approximately 2.75 Si, exhibited the best corro