4 replies to this topic

[yeek]

Dear all,

Does anyone with experience in working with hydrocracker units have any guidelines on what should be the design guideline for wash water injection rate into the high pressure section just before the air fin cooler?

From my little research, it seems like an important step as a water injection rate that is too low can cause severe corrosion due to build up of corrosive materials.

I would be most grateful if anyone with experience can share what is the minimum required wash water injection rate.

Regards,
yeek

[omarmco]

The basic idea is to mantain liquid water to wash the salts.

Usually minimum 20% of the injected water @liquid state is recomended for hydrotreaters.

[yeek]

Attached article would be of help. API 581, appendix G, section G.11 also has a section on estimating corrosion rate.

This form of corrosion essentially occurs at temperatures below 150 oC.

Remedy is to ensure sufficient wash water injection that is sufficient to take care of salt dissolution and evaporation.

Regards,

Sachin

Dear All, thanks for your help.

[murthy.nelakanti]

If you are still looking for the answer to your question, Here are general guideline for determining wash water rate in hydroprocessing units:

• At least 20% of water remains in liquid form after injection. :- to avoid flashing all water and creating an acidic environment or a localized high conc of salts when first drop of water begins to condensate.
• To maintain the conc of NH4(HS)2 in sour water below 8 wt%:- to minimize potential corrossivivty of sour water in reactor effluent condenser tubes and outlet piping.
• 5 vol% of fresh feed rate.

Regards,

[rabindra]

In addition to the above, since the Chloride salts has higher sublimation temperature, there is a chance that they form salts in the Feed-Bottom heat exchangers itself before the Air cooler. So you may need to inject wash water before the air cooler. Most of UOP's design have this provision.