Atmospheric Tower Corresion

[engzeidan]

Based on the reflux stream temperature, how can I determine if aqueous droplets will form in the tower potentially causing corrosion? Do I check if the reflux temperture is colder than the condensation temperature of water at the tower operating pressure? Or do I use the free water formation temperature of the vapor flow in the top section of the tower?

Using the condensation temperature seems not reasonable for me because condensed water droplets will disolve in the condensed hydrocarbon droplets.

Any opinions/ideas?

 

[25362]

Henry Z. Kister's Distillation operations McGraw Hill, may have answers to your query.

 

[thiru4vino]

Your top temoperature cud be nearer to the dew point, that's Y u 're getting aqueous drops in the column top much before condenser.

Calculate ur dew point and adjust ur top temperature..
BOL
atm_chill

 

[22082002]

It may not be reasonable to you( but may I know why do you feel so..?), that's how the columns are designed.

 

[gedomin]

Top trays in a crude tower are prone to corrosion due to shock localized condensation, specially if the reflux temperature is lower than the water dew point. A combination of proper construction materials and a corrosion control with chemicals injection is the common mitigating practice.
Free water formation normally occurs along the condenser, where corrosion and fouling problems are also usual.
You can contact BETZ or NALCO companies who can give you more advise on the subject.

 

[mchohan]

Corrosion problem in this section will be reduced if operate the reflux return temperature about 10-15F above the water dew point. According to my experience, monel trays also last not more than 3-4 years in this region of tower (we always order new trays before T/A). Keeping the return temperature up helps reducing the schock condensation on trays. The use of corrosion inhibitor in reflux is highly uneconomical because of amount of flow.
The water presence in this reflux stream is even bigger problem for heat exchanges in this circuit, which develop high pressure drop due to NH4Cl deposition on tube sheets.

 

[PAN]

I do not have experience to use monel tray for the atmospheric crude tower. However, I always use monel strip lining at the shell.

Please share your experience about tray material. Should we use AISI 304 in the upper portion of crude tower?