Air cooler fouling and cleaning methods 4

[Kresimir]

What would be the best way to do a chemical cleaning of HDS plant reactor effluent air cooler (before the high pressure separator) that is fouled with anorganic salts (bisulphides and chlorides) and maybe some solidified heavy (vacuum) gas oil?
Shoud I use water, or water and some chemical agent?

 

[0707]

Kresimir

For a chemical cleaning you should contact a special contractor on the job. Special concerns chemical cleaning are; type of tube material, expected fouling organic compound, Ph control, iron analysis during cleaning time. Any chemical cleaning should be followed by a precise neutralizing operation. A chemical cleaning if not proper controlled can damage your air cooler tubes and accelerate your tube corrosion rate. If your fouling compounds are not hard or viscous high-pressure blast water jet is a good alternative to a chemical cleaning.

Hope it helps

Luis Marques

 

[pkpbip]

Typically if the process side foulant is ammonium chloride and bisulfide salts then water is sufficient in cleaning the exchanger when dealing with hydrotreaters. These salts are extremely soluble in water.

A lot of hydrofiners have either continuous or intermittent water washes for coolers in a spot where these salts would form.

One thing to note is that these salts can be extremely corrosive in the presence of water especially if there is a lack of water to sufficiently dissolve the salt. There have been many cases where loss of containment has occured because of these type salts. I would assume that there is no water in this stream. Is this correct?

Also, hotter water is better!

 

[25362]

In addition...

Apart from corrosion to iron by sublimation of the very hygroscopic ammonium chloride white saltlike solids and formation of iron sulfides (pyrophoric iron) blackish-gray deposits, which together react to form corrosive HCl, the common trouble-causing problem these air coolers suffer from is flow mal-distribution.

This maldistribution is caused by nonsymmetrical flows that create slightly lower flow rates in those tubes farther away from the inlet, which thus become cooler, a fact that induces fouling, that brings about corrosion in a vicious circle.

The recommended practice is to make inlet and outlet headers large enough so that their pressure drops are very small when compared to that of the bundles themselves.

 

[visangio]

Kresimir,
as observed by pkpbip and 25362 water washing is the proper practice to prevent deposition of inorganic salts in HDS effluent coolers.
To prevent the corrosion that could occur in presence of water a corrosion inhibiton program should also be applied.
Best regards,

Vincenzo Sangiorgio

Vincenzo Sangiorgio

http://www.gewater.com

 

[0707]

Kresimir

Everything other posters said on this subject is true, but I suppose you have that. Let us know.

Luis

 

[Kresimir]

A forgot to mention that my plant has continuous reactor effluent water washing, before the air cooler.
However, due to the facts that the air cooler has 4 banks, and its piping is simetrically balanced; also that it is running at around 40 % design flow; and that the water injection is in one point; we found that outer air cooler banks are heavily fouled.
This is why we are planning warm water washing, at plan shut down, without mechanical cleaning.

Also, method we used for establishing the condition of tubes with respect to fouling is, thermography (or FLIR scanner).

Kresimir

 

[LuizSouza]

Kresimir,

I think that all posts are just about chemical compouds that could provide the foulling, and concerns about chemical cleanings, but, in fact, you should have all your tubes not clogged to permit the chemicals flow.

Have you even think of mechanical cleaning?

Luiz Souza
Brazil