Corrosion behavior of heat exchanger tube materials in simulated coal gasification atmospheres with different H2O-content

Corrosion behavior of three Fe-base heat-exchanger-tube alloys was investigated in CO—CO2—H2—H2S-HCl-containing gas mixtures of different (0–17%) H2O content which simulated the heat-recovery-boiler environment of a dry-fed, entrained slagging-type coal gasifier. Sample temperatures during the 500 hour-long tests were kept at 300, 450 and 600°C in the low-pressure (LP; latm) tests and at 450°C in the high-pressure (HP; 31 atm) tests. Surface recession of the 2.25Cr1Mo steel increased while those of the 12Cr steel and 20Cr32Ni alloy decreased with increasing H2O-content of the gas in the LP-600°C tests. Surface recession of the alloys decreased with temperature regardless of the H2O-content of the gas mixture. Increasing the total gas pressure at 450°C caused changes in the surface recession of all alloys. However, the effect of H2O-content on corrosion at high pressure was less significant for the 20Cr32Ni alloy. The effect of the steam content of the gas on alloy corrosion was observed to be related to a...