Weekly Topic-20090304-Can the lower section of the wastewater stripping tower be made of stainless steel?
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In the wastewater stripping unit of our facility, the upper part of the stripping tower is made of stainless steel, while the lower part is made of carbon steel. Please discuss whether it is possible to use stainless steel for the lower part as well What are the disadvantages of using stainless steel? (The material of the filler is: 0cr18Ni9Ti) Your support is the driving force that propels us forward! ! We earnestly ask everyone to actively participate in discussions. Our moderators will assign different levels of scores or rewards based on the depth of the discussions, and they will also review the scores given by members among themselves! ! ! On Saturday, a “Classic Reply” will be selected from all responses, awarding 3 Charm points. At the end of the month, participants take part in the monthly evaluation; those who win are rewarded with 5 Charm points. Those who are rated as having “Classic Replies” for three consecutive months receive 10 Charm points as a reward. The weekly topic will be updated on Monday. This post was last edited by lxzzl on 2009-3-26 10:14]
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Please provide the names of the substances contained in the wastewater; otherwise, how can it be analyzed?
It should be related to the materials in the wastewater. By the way, may I ask the original poster what material the filler inside is made of?
It is wastewater; the material of the filler is 0cr18Ni9Ti. This post was last edited by lxzzl on 2009-3-25 15:14.]
What kind of wastewater is it? Please provide detailed information; of course, the choice depends on the material and medium involved. This post was last edited by lxzzl on 2009-3-26 10:15]
I guess it shouldn’t be a problem to use stainless steel for the lower part; it’s probably better than carbon steel! But the cost will be higher!
The pH value ranges from 2 to 13, while the temperature is between 45 and 90°C. The COD is generally 5,000–9,000 mg/L. This post was last edited by lxzzl on 2009-3-25 15:14.]
In my opinion, the possible reason for using stainless steel in the upper part and carbon steel in the lower part is that the volatiles present in the material are corrosive to carbon steel at certain concentrations. Therefore, the concentration of the distillates in the filler and the upper part of the tower increases as one goes higher, which is why stainless steel is used there. In the lower part, since the concentration of the distillates is not very high, the corrosive effect on carbon steel is not strong; for economic reasons, carbon steel can be used there as long as an adequate margin against corrosion is provided. In this case, stainless steel could also be used in the lower part, but the cost would increase significantly. This post was last edited by lxzzl on 2009-3-25 15:13]
In the wastewater stripping tower, the H2S concentration increases gradually from bottom to top. The reason for using carbon steel in the lower part and stainless steel in the upper part is mainly to consider corrosion resistance and cost savings; if cost is not a factor, it is also acceptable to use stainless steel throughout the entire tower. This post was last edited by lxzzl on 2009-3-25 15:13]
Hello LZ: The upper part of the stripping tower in the wastewater stripping unit is made of stainless steel because there are many corrosive substances present in that upper section; the range of pH values mentioned indicates that corrosion caused by strong acids or H2S is likely at play； The lower part is made of carbon steel mainly because the degree of corrosion there is not as severe as in the upper part; thus, the material requirements are reduced to save costs. I don’t think it’s necessary to use stainless steel for the lower part as well, because after all stainless steel is more expensive than carbon steel. Moreover, the original poster didn’t mention any issues with using carbon steel; therefore, I believe using stainless steel would be an inappropriate choice.