3 replies to this topic

[naeemullah]

i am a bignner, any one can explain briefly the phenomena of atmospheric crude distillation overhead corrosion.

Edited by naeemullah, 28 September 2012 - 04:39 AM.

[Fr3dd]

Hi naeemullah,

The problem on atmospheric distillation colums overhead is the chloride. As you may know, the crude received by the refineries frequently have certain salt content. If you preheat this crude (before feeding it to the distillation column) by hidrolisis, the chlorides will be converted in Hydrochloric acid (HCL). After feeding to the distillation column, the HCL will go out the column as part of the overhead product, which causes the corrosion.

The crude is usually not fed directly to the ADU (Atmospheric Distillation Unit), it is pretreated before entering the column in order to remove free water and salts (usually Chlorides).

The crude then is mixed with water, taking advantage of the salts solubility, and then enough time is given to settle and separate (salty) water phase from oil phase (sometimes with the help of a electrostatic separator). This is a really important step of the crude pretreatment, a lot of corrosion problems can be prevented in this phase.

Regards,

[Technical Bard]

It is also possible to see corrosion in crude overheads from other species, although most plants are designed to deal with sulfide corrosion from H2S cracking out of the oil. Another example I have seen is problems from the presence of phosphates and sulfates in the crude, largely from production chemicals added in the oil field.

[naeemullah]

thanks for your replies