3 replies to this topic

[GSaikrishn]

Dear sirs,


Ammonium chloride salt deposition occurs in the colder sections of the Platfomer fractionation sections like the stabilizer oevrhead sections, compressor suction lines etc.

Now Nh4 cl salt deposition is known to cause havoc in the piping sections and eat away the metallurgy (e.g. it just managed to eat away the entire stariner mesh of my recip compressor).

Is prior identification before process upsets occur due to nh4cl salt deposition possible.

Is there any known method adopted anywhere or else literature sources which address this above issue.

regards
Saikrishna

[kkala]

I dare give some notes, though not aware of the subject (which has not received an answer so far).
1. Corrosion mechanism can be seen in http://books.google.gr/books?id=OHsKYj8T9z8C&pg=PA60&lpg=PA60&dq=NH4Cl+corrosion&source=bl&ots=iZCzVbVQHV&sig=8o6PVTwUh9mDXzTcVGvpjEDEECY&hl=el&sa=X&ei=L9bmT7z2OoOp4gSSh-S7AQ&ved=0CF0Q6AEwBg#v=onepage&q=NH4Cl%20corrosion&f=false and some preventive measures (but generic).
Also http://books.google.gr/books?id=kChI_04rB1wC&pg=PA31&lpg=PA31&dq=NH4Cl+corrosion&source=bl&ots=Um7BN43waA&sig=ShUtzN4ZbsO5TKO0GwtM6YNJ-6A&hl=el&sa=X&ei=L9bmT7z2OoOp4gSSh-S7AQ&ved=0CEkQ6AEwAg#v=onepage&q=NH4Cl%20corrosion&f=false.
2. http://www.nace.org/cstm/Store/Product.aspx?id=e93a21dd-a77b-4015-b4cf-b933865d48f8 seems to be useful, though it is not free.
3. Useful information, even in pieces, could be collected by searching the Web.

Note: In fertilizers (~1979) we selectively used better (stainless) metals on the equipment parts, where corrosion was severe.

Edited by kkala, 24 June 2012 - 04:17 AM.

[ankur2061]

Saikrishna,

What is the source of the ammonium chloride in your platformer fractionator? Are you injecting ammonia to control hydrochloric acid corrosion in the fractionator similar to what is done in an atmospheric distillation tower?

The best solution to prevent ammonium chloride deposit is to inject aqueous ammonia instead of introducing anhydrous ammonia which will reduce the formation of crystalline ammonium chloride deposits

If you are facing repeated corrosion related problems due to corrosion from ammonium chloride, the best way to prevent this is to provide monel lining of the wetted parts.

Hope thsi helps.

Regards,
Ankur.

[Himanshu Sharma]

I cant foresee any reason for ammonia presence in the Feed to CCR (UOP trade name PLATFORMER i.e PLATinum reFORMER) unless or until there is some problem in the stripper column of Naphtha Hydrotreater unit.

Since you are observing NH4Cl corrosion on recovery plus compressor suction lines,it affirms my belief.

Residual water must be maintained in the hydrotreated naphtha feed. An alumina-supported reforming catalyst requires moisture to activate the acid function and provide homogeneous chloride content over the whole catalyst bed. When the environmental atmosphere is too wet, however, chloride in the catalyst may be leached off and thus deteriorate its acidic behavior. Therefore, water control must be performed along with chloride control to maintain a proper chloride–water balance in the environmental atmosphere.As per what my memory recalls , the chloride content on the catalyst should be kept in the range of 0.9– 1.2 wt% for most bimetallic catalysts. To meet this requirement you should maiantain an environment of 1–5 ppm of hydrogen chloride and 10–20 ppm of water should be provided in the circulating gas over the bimetallic reforming catalysts.

In your case the remedy lies in increasing wash water in the Hydrotreater along with performance monitoring of stripper.