5 replies to this topic

There is an issue of ‘jelly’ or some form of emulsion in our diesel. This thin layer of emulsion floated throughout the diesel, it does not settle at the bottom. It takes the color of diesel, probably slightly darker. Note that the diesel is a mix straight run diesel from condensate and crude. We tried to re create this jelly, so far only one chemical when injected to the mix diesel will form this jelly and this chemical is the neutralising amine. Need to know the possible mechanism of this jelly formation and whether any of u have faced similar problem before. Appreciate yr opinion.

[Zauberberg]

Hello MTM,

During my experience gained in refinery Operations so far, we had two similar issues:

1) Unacceptable ASTM D1094 results ("water reaction test") of hydroprocessed Kerosene Jet A1. Cloudy appearance of kerosene sample, with sort of jelly-structure at water-hydrocarbon interface, was a direct consequence of corrosion inhibitor dozing problem at HDS unit (actually, we were dozing as much as 10 times higher than we should). The problem disappeared after we fixed the inhibitor dozing pump. Kerosene feed had not these kind of impurities, which was a clue for investigation.

2) We had almost the same situation with virgin kerosene, produced at atmospheric distillation unit. Here, the problem was the origin of crude oil. During shipment, the crude was contaminated with surfactants having boiling range within Kerosene cut. Situation has been somewhat corrected by lowering kerosene end point, which caused certain amount of impurities to end up in lower side product, LGO.

Kerosene in both cases had a boiling range 175-250C.
You should identify the spot within refinery where this problem begin: is it ADU, HDS, way up to tankfarm or after blending activities.

Regards,

[Alawi]

Hello MTM,

In one case water was not separating as usual from the diesel in our diesel storage tanks due to the formation of some type of emulsion mainly located at the water diesel interface (there was no exact interface,there was an emulsion) , although the problem just disappeared by itself in a very short time supporting what MR. Zauberberg went to about the possibility of a mix up in the dosing of a certain chemical that may have possibly occurred due to a mistake of operation or some mechanical problem in the dosing pump (note : it is a good idea to keep track of the chemical consumption by recording the chemical storage tank level not just reading the pump dosage rate). We inject neutralizing amine in the atmospheric distillation O/H section making the possibility of its mix with diesel rather slim. The only chemical I can remember that is injected at a location allowing it be mixed with diesel during operation is the crude preheat antifouling chemical. Tank warm wise there are flow improvers (we use) and cetane improvers (we don’t use). Any way during our very short problem we were advised to check the diesel fro bio-organism growth (bacteria or Algae ) using special Petri dish kits for diesel, we didn’t find any and the problem just disappeared.

Alawi

[Zauberberg]

MTM,

What is the origin of your diesel? Is it virgin LGO, hydroprocessed diesel, LCO, Coker gas oil etc.? What is the moisture (water) content of the sample that has jellyform emulsion problem? Did you track emulsion formation issue up to the process plants, or did you see it only in the diesel storage tanks?

MTM,

What is the origin of your diesel? Is it virgin LGO, hydroprocessed diesel, LCO, Coker gas oil etc.? What is the moisture (water) content of the sample that has jellyform emulsion problem? Did you track emulsion formation issue up to the process plants, or did you see it only in the diesel storage tanks?

Hi,

Thks for yr reply. We have 2 sources of diesel (1) Atmos crude distiller producing single straight run diesel. The stream is treated with salt drier. (2) Condy fractionator producing single straight run diesel as the heaviest product. Recently, we are injecting caustic to the fractionator. The moisture content is < 100 ppm at the r/d. As both of u described it, the emulsion mostly lies at the water-HC interface. Some of it seems to be located throughout the diesel product.

Currently, amine has become one of the major suspect is the bcos we manage to detect it in the diesel. However, I still do not understand the transfer mechanism since this chemical is injected in the ovhd line. Although it can be recycled thru reflux line, still a long way to go to the diesel tray. Caustic is another suspect, but since we cannot recreate the emulsion using this chemical – it was rule out.

Zauberberg, I’m interested to know the method u use to detect the surfactant contaminant in the feed. I put this as one of the cause, but do not know how to verify it. Cheers.

[Zauberberg]

ASTM D1094 is very subjective method and it is not a common/wide-accepted procedure for determination of water separation characteristics of jet fuels and kerosene. The alternative is ASTM D3948, which can be found (and downloaded for 56$) at http://www.techstree...product_id=9429 or at ASTM website: http://www.astm.org

Experimental procedure for identifying the impurities is to perform a crude oil TBP analysis in your R&D laboratory - if the problem lies in crude oil contamination. Doing that way, we managed to isolate a mixture of components with blue visual appearance (within naphtha/kero cuts), but with no success in compound identification. If your R&D laboratory cuts are OK, you should move your investigation further to caustic treaters and their operation.

And another thing that is worth to mention: if your ADU is two-stage overhead system (hot and cold reflux drums), injecting neutralizing amines upstream of the 1st stage condensers almost always leads to tower top zone corrosion, separation efficiency loss (between naphtha and kerosene) and other possible problems - and this may be the accumulation of amine salts/surfactants in your column side-cuts.

Please inform us what you have found so far, this is an interesting thread.
I think it is better to post these kind of questions inside Refining forum. There is much bigger chance to get appropriate answers and support from people experienced in refining operations.