Solving the corrosion problem in the stripping pipeline of the condensed liquid stripping tower
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This post was last edited by 654262293 on 2011-3-30 at 15:44. Sulfur-tolerant shift reaction is used to produce gas from coal water slurry; the shifted gas is washed in a wash tower using boiler water. The washed water is then stripped with steam. The main components of the stripped gas are CO2, H2S, NH3, and H2O, with small amounts of CO, H2, CH4, and N2. The pipelines for this stripped gas are made of 304 material. During maintenance work, it was found that the elbows in these pipelines were severely corroded. Could anyone explain the reasons for this corrosion? What measures should be taken? What material should be used to prevent corrosion?
If the temperature isn’t high enough, water containing H2S should corrode stainless steel pipelines quite rapidly; that’s just my opinion
It’s over 120 degrees at the bottom of the tower, and 70–80 degrees at the top; moreover, this refers to the stripping gas line at the top of the tower.
I'm talking about the stripping gas line. It seems that the temperature you mentioned is fine; then the remaining possible cause could be chloride corrosion, which is a quite likely possibility given that it’s located at the elbow area, probably near the weld. Have you had your water analyzed for chloride levels?
Reply to 4# Wang Jingliang: The washing water uses boiler water, so there should be no problem. Where does the chlorine ion come from? Besides, the washing tower is also made of stainless steel; then why doesn’t the washing tower corrode, while only the condensate stripping tower does?
This post was last edited by Wang Jingliang on 2011-3-31 at 11:53. In my opinion, the only possible reasons are the two mentioned above. What you said makes sense; if it’s chloride ion corrosion, then the corrosion is more likely to occur in the conversion system earlier in the process (chloride ions come from water gas – I’m not sure if that’s the case for your system as well). Such an environment also makes stress corrosion more likely to occur; this is a complex issue that is closely related to the stress conditions in the piping. It is recommended that you use pipes made of 0Cr18Ni10Ti (or 304L) to prevent intergranular corrosion, and that you try to eliminate any residual welding stresses.
Reply to 6# Wang Jingliang: If the source of chloride ions is water gas, then the scrubber should be corroded first, right?
The equipment is fine; it’s usually the pipelines that cause problems, and there should be no issues with the scrubber as well. The main problem lies before and after the converter
It is said that molybdenum steel can resist this type of corrosion; I wonder if anyone who has used it can share some experience.
Chromomolybdenum steel is most susceptible to chloride corrosion, right? When chromium is displaced by hydrogen, the steel loses its functionality. However, it seems to be a type of microelectrochemical corrosion. . .