Regarding desalter 1

[vbpp]

Hi,
i work in crude distillation unit.the problem that we are facing in our plant is even having the salt content @ desalter outlet at around 0.5 ptb we are getting chloride around 70 ppm in the column overhead.can u suggest me some ideas?

 

[mfelzien]

The chlorine is coming from someplace, and either through a recycle stream or fresh feed accumulating to 70ppm. Are the side strippers using de chlorinated H2O, or the Desalter wash water, is there a possibility of carry over from the desalters into the CC?

There may be other generative sources sources of chlorine in (stream reactions) the crude that are not being removed. Etc. If you could give more information I think people might be able to suggest more detailed answers. But give what you said, it is hard to go much further and be specific.

 

[vbpp]

hi mfelzien,
We are using stripped sourwater to spray on the tube side of the overhead exchangers.Today i have sent the sample to check chlorine in it,Apart from this there is no possibility as steam we are using has no chlorine content.
Can u guide me by giving some datas to find chlorine from the corrosion probe(corrosion rate) which is inserted on the column overhead
one day while processing Sour crude it shows around 30 miles per year
while processing sweet it shows around 10 miles per year
wat we can predict o seeing the probe value?

 

[mfelzien]

corrosion rates are very subjective and difficult to determine. One solution is the use of corrosion coupons to determine the actual corrosion rate. A probe that determines this in my mind would be unreliable. What I think your probe is doing is measuring the concentration of a disolve species in solution, say oxygen or chlorine. From that perhaps you could determine the mpy corrosion rate, but it would be really unreliable.

If you have side strippers on the CC that are using clean steam, and you have a closed loop on your reboiler and condenser, then your chlorine is coming in at the feed and accumulating. Check the upstream units to see if the makeup water has chlorine in it. Hope this helps.

 

[Yordif]

Becareful about the assumptions on CL levels. The common ways to measure are with a boiling water test of the desalted crude. Inorganic salts are water soluable, and all of your naturally occuring salts coming in with the crude will show up. The danger is if you have organic salts, either in the crude or in re run slop oil. Those are generally not water soluable and will not be caught by the boiling water test.

I had that happen to me in the early nineties. My salt out of the desalter was fine , by test, but my OH chlorides were high. Unknown to me some slop oil with some cleaners was being added. Once we moved that to the coker, everything went back to normal.