Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Crude unit corosion

Crude unit corosion

Crude unit corosion

What is the effect of phenole in corosion regime on crude tower overhead condenser? HCl is also present in aqueous phase (liquid).

RE: Crude unit corosion


I would be far more concerned with HCl corrosion in the overhead condenser than the effects of phenol. Companies such as GE Betz, Nalco and Baker-Hughes to name a few are well versed in corrosion inhibition in these systems through application of filming amine and/or neutralizing amine products.....they should be able to serve your needs.


RE: Crude unit corosion


On top of overhead CDU as pH increases toward the neutral region the concentration of bisulphide ion in solution increases. It has been demonstrated by several investigators that there is a sharp increase to the rate of corrosion in the region of pH 6.8 to 7.3. The sharp increase in corrosion rate is apparently the result of faster reduction of bisulphide ions both from the scale lattice and solution. As the scale lattice is altered FeS is released, exposing unreacted iron, and the FeS enters the water phase. In a crude unit this phenomena is recognized as black water.

The dissociation of H2S in HS- and S++ is minimum at 5 pH.

A good and proper water wash would probably be the key to minimize corrosion problems on overhead distillation units. The quality of water wash is very important.

In our crude unit we use continuous water washing of the overhead air coolers. The water from the dessalters is refluxed through a feed water drum to the inlet nozzles of air coolers header boxes. When water is saturated and chloride contents on overhead drum are above 50 PPM we empty the feed water drum and we add make up water. The optimum water wash should be with demineralised but this is not economic.

The standard wash water quality normally is as fallows:

Ph ? 5.5-7.5
Total hardness- < or = 50PPM
Total HCO3- and CO3- content < or = 50PPM
Ammonium hydrosulphide (NH4HS) < or = 100PPM
Chloride < or = 2000PPM
Sulphate < or = 200PPM
Oxygen < or = 1PPM

Some years ago because of ammonium chloride under deposit corrosion and difficulties in stabilizing pH we give up injecting liquid NH3, we start controlling Ph with a neutralize inhibitor up stream overhead air coolers. On overhead line of the column we have a corrosion inhibitor injection. Down stream of dessalters we have a caustic injection to neutralize the chlorides. This caustic injection should be as much as possible stequiometric, we should inject caustic OHNA in the same proportion of the salts we have at dessalters outlet. The caustic injection is to form sodium chloride salts at dessalters outlet and not to control PH. The caustic limit injection of 12 PPM of OHNA at dessalters outlet is to avoid caustic embritllement downstream dessalters equipment minimizing as much as possible coking formation at crude heaters. The caustic injection should be performed through a proper quill. From times to times is important to check quill condition.
Good dessalters performance is also a good way to control crude overhead corrosion.

Try to get good advice on this subject from Baker, Nalco, Betz or others, they will help you.

Luis Marques

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members! Already a Member? Login


Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close