5 replies to this topic

[drilling2013]

I have question about Desalter operation. I need to know which wash water is recommended for desalter, references and codes such as API, NACE....etc

 

I know that some refinery companies are using service water or stripped water. I asked above question because I investigate about corrosion failure for topping plant (cooler coils for mechanical seal at residue pump)

[daniwibowo8]

Hi Drilling2013,

 

I dont know the standard from NACE or API but commonly the specification of wash water as follows:

1. pH = 5.5 to 6.6

2. Oil Content = as minumum or traces

3. Hardness = as minimum

4. Rate wash water = minimum 3% from crude flow

5. H2S and NH3 = as minimum.

6. Temperature = ambient or heated until around 150 deg C

 

Thx.

[P.K.Rao]

I have seen some refineries using stripped sour water.

[gegio1960]

My 2 cents...

Best choice is demi water.

Stripped water is used but it adds some other contaminants to the ones carried by the crude. An old practice used to send phenolic stripped water as wash water to the desalter (and then, brine to the WWTP): phenols were absorbed by the crude and so they were unloaded from the WWTP....

In a recent CDU design, I've seen BFW used as Wash Water: anyone can choose his way to waste money...

Good luck!

 

questions for dani:

- why 5.5 - 6.6 for pH?

- 3% appears very low to me

thanks

[daniwibowo8]

Hi Gegio,

 

apologize for mis-typo, it was 6.5 i/o 6.6

Yes, gegio, i found the wash water from several said that minimum flow 3% but in case low salt content at crude.

 

I have something need to ask 

We have wash water which have chloride content up to 336 ppm and if i am not wrong it is almost same as 13.9 ptb (assumed Cl to be NaCl).

The source of wash water from overhead CDU and HVU (sour water).

The overhead water for overhead CDU accumulator split by two. one stream recyled for wash water fin-fan and the rest flow to desalter wash water surge drum. sour water from surge drum mostly pumped to desalter and some of them send to effluent water treatment.

 

any suggestion to upgrade the wash water quality? we have limited source of demin and stripped water.

 

Regards, DW

[gegio1960]

A lot of "thirsty" refineries adopt the same processing scheme you mention above. Of course, it works until the desalter performances are satisfied and there aren't big corrosion troubles (especially at topping tower overhead).

In case demi water production can't be increased, some possible improvements to this situation could be:

- a capacity revamp of the SWS

- an increased recovery of condensates

- optimization (saving) of steam consumptions, possibly thru increased heat recovery from the hydrocarbon streams

Other (classical) solutions can be found by knowing/studying the overall refinery water balance.

Good luck!