Q & A > Question Details
In an Reformer Stabilizer Debutanizer Column, we do regular water washing of the column to get rid of the ammonium salts. We do this procedure by reducing the throughput and pressure of the column and produce off-spec reformate during the process.
We do like to ask if any refiners have a practice of introducing steam into the column while the unit is online to clean the ammonium slats deposits in the column and condenser? If yes, what are the concerns and precautions to be observed?

I would like to confirm that what you had mentioned. HIGH PH contributing to the severe corrosion. We have a similiar system upstream(the first column for the FRN Feed) and found severe corrosion in the overhead system of the distillation column and we found that the pH was very low and ammonium salts, in the range of 4.5. Hence,we are injecting a highly basic chemical to increase the pH and are currently maintaining 9 pH. But to our confusion , we are still finding a very high amount of corrosion. If what you mentioned is true, what we did in the system is not going to help us but rather worsen the condition?

Thanks Stephan, Could you please elucidate on the corrosion due to high pH? We have a Debutanizer Column , the first column in the Aromatics Complex which is severely corroded in the overhead due to ammonium salts. The feed is from the refinery , Full Range Naphtha. We had initially of an pH of less than 4. Then we injected an chemical to boost the pH and are currently mainly in the range of 9 pH. But the corrosion is still not under control. Could the high pH be one of the concerns to look at?
09/10/2014 A: Berthold Otzisk, Kurita Europe GmbH, Berthold.Otzisk@kurita.eu
Reformer debutanizer columns, FCC main fractionator columns and their overhead systems often suffer with ammonium salt fouling and corrosion. Some kind of “water washing” by injection of water, steam or pressure reduction is often practised to remove these ammonium salts. In general ammonium salts such as NH4Cl or NH4HS are highly soluble in water, but the results of a water washing procedure of a Reformer or FCC column are often doubtful and not satisfactory. Ammonium salts still remain in the system and products are off-spec during the washing procedure.
Kurita´s patented ACF technology is a very interesting and powerful alternative as it can be used continuously without water washing procedures and production losses. The additives used for this technology are chemical liquid formulations based on a very strong organic base. The ACF additives directly react with ammonium salts and are converted into liquid, non-depositing components with a neutral pH of 7. These liquid ACF reaction products are routed to the overhead system, where they can be removed.
20/08/2014 A: Stefan van der Wal, Mettler-Toledo Process Analytics, stefan.vanderwal@mt.com
Important for sure is to carefully monitor and control pH of the wash as ammonium salts, ammonium bisulfide in particular, are very corrosive, especially at high pH. Above pH 7.6 corrosion caused by ammonium bisulfide increases exponentially. Continuous pH control is very helpful in reducing corrosion. Also high flow rates of wash water need to be avoided as ammonium salt wash velocity also cause an increase in corrosion. Very similar effects are also observed in hydrocrackers.