Iron power found in the process
Iron power found in the process
(OP)
Friends,
Over the weekend we opened a couple towers and took out alot of very fine black solids which were plugging distributors. We just had a shutdown and the same towers were well cleaned and flushed. On drying these solids are magnetic, and there has apparently been a history of such iron containing solids in this plant. The towers and packing are primarily carbon steel, running at atmospheric pressure, and using a solvent containing some 3-5% water.
Years ago in a previous plant (vacuum tower, no water) I encountered the same type magnetic solids on start-up and used rare earth magnets in a basket strainer to capture and mitigate the problem which eventually went away. Since this problem appears to be common in these processes, and the amount of metal loss looks significant, I would like to get a better understanding of the formation mechanism this time around.
Does anyone have any suggestions for where to get some knowledge of this? Is it possible that flash rust or chip scale can be reduced in the process back to a magnetic state? What passivation or treatments might be effective? Is this likely to be from vessels and pipe, or packing, etc. As I know little on the subject at this point, any suggestions would be helpful.
best wishes,
sshep
Over the weekend we opened a couple towers and took out alot of very fine black solids which were plugging distributors. We just had a shutdown and the same towers were well cleaned and flushed. On drying these solids are magnetic, and there has apparently been a history of such iron containing solids in this plant. The towers and packing are primarily carbon steel, running at atmospheric pressure, and using a solvent containing some 3-5% water.
Years ago in a previous plant (vacuum tower, no water) I encountered the same type magnetic solids on start-up and used rare earth magnets in a basket strainer to capture and mitigate the problem which eventually went away. Since this problem appears to be common in these processes, and the amount of metal loss looks significant, I would like to get a better understanding of the formation mechanism this time around.
Does anyone have any suggestions for where to get some knowledge of this? Is it possible that flash rust or chip scale can be reduced in the process back to a magnetic state? What passivation or treatments might be effective? Is this likely to be from vessels and pipe, or packing, etc. As I know little on the subject at this point, any suggestions would be helpful.
best wishes,
sshep





RE: Iron power found in the process
Does anyone have any comments or experiences along these lines?
Are any of you using passivation washes on some equipment before exposing carbon steel to the air after steaming or chemical cleaning? What type of passivation washes are you doing (caustic, ammonia, etc)?
any help is appreciated,
sshep
RE: Iron power found in the process
How to deal with it is the hard thing, you can use chemical inhibitors or you could try material changes or alter some parameters pH/Temp pressure etc but again totally dependednt on your process.
RE: Iron power found in the process
Thanks for reminding me not to jump to a conclusion about the product involved.
A story: My previous experience with these type solids was many years back. A younger less experienced sshep was working night shift in a shutdown and we were chemically cleaning an HF alkylation unit to remove iron floride scale prior to opening. The last steps of the procedure called for a rinse, then a caustic wash and then a second rinse. The operators and I believed the caustic wash was conservative to nuetralize any residual acid from the chemical cleaning. Because our first rinse came back with a pH around 7, we did not make a caustic wash. Later I learned that the caustic wash was a passivation step to avoid surface rusting when the equipment was opened. On start-up we had a lot of magnetic solids show up in a stream that was also used for pump seal flushes. A short term crises which eventually went away. This negative experience is still influencing my judgement this time around.
best wishes as always,
sshep