Mercury content in the refinery wastewater

[Dendrobium1975]

thread483-123687


My refinery haven't had experience to process crude oil with high mercury content before, but I'm sure that it will be a possibility in the near future that must be anticipated. What I would like to know is about the mercury in the waste water. Which waste water stream that will most likely contains the highest concentration of mercury? Will it be the sour water from Crude Column overhead Receiver, from Desalter's brine water, or probably from other stream?

Any sharing in experience will be highly appreciated.

 

[Jason5000]

I've seen elemental mercury found in Crude preheat exchangers. Mercury boils at 674 F; however, it exerts a fairly high vapor pressure. It tends to concentrate in naphtha stabilizer/debutanizer areas. Also, catalyst units tend to be too hot to tie up mercury as amalgem, so the stuff can carry clear through alkylation units. I guess that narrows it down to just about anywhere, sorry.

Don't overlook other chemical inputs to your refinery processes either. Purchased caustic and sulfuric acid can have mercury in them too. They may be very low concentrations, but in terms of your overall mercury mass balance they may not be insignificant.

 

[dosto]

yes agreed with Jason.my worksite also havin mercury problem especially on the naphta minus stream most are at the sour water loop,naphta stabilizer and also tops naphta splitter,how ever it was quite costly to have a special Decontamination Plan just incase we are going to have major turn arround and even for small maintainance.

 

[dosto]

Jason,other than caustic and sulfuric acid,from your experience is there any chemical that can contribute to mercury in your process...

 

[Jason5000]

Sulfuric acid and and caustic are where I've had the best luck reducing mercury throughput. Between Alky and Merox units and other various uses they tend to see a lot more bulk use than other chemicals in a refinery. Crude and natural gas might be the only things you actually purchase more of.

And there's certain types to watch out for like mercury cell caustic, surprisingly enough. Mercury cell used to be the most expensive grade due to its very high purity, with the exception of the mercury, but I'm not so sure that's the case any longer.

Sorry, but I can't give you any leads as to other chemicals to watch out for. A little testing of your effluent streams from your various units might give you some good ideas as to where to focus your search if you have a mercury problem.

 

[Dendrobium1975]

Dear Jason and Dosto,

Thanks for this great discussion. I have also found a good reference in this link : ipec.utulsa.edu/Conf2006/Papers/Braden_92.pdf

Have a nice day, guys.

 

[moltenmetal]

The mercury cell caustic may give you traces of mercury depending on the spec. The membrane cell caustic WILL give you more than traces of chloride. 50% caustic can routinely be 1% chloride. So with caustic, unfortunately it's "pick your poison"...