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High Acid No. in Crude
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Source：Internet Author：Unknow Pubdate：2008-04-15
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taylorg (Mechanical)
2 Jun 05 8:51
Could someone please advise me of the best way to counteract and/or effectively reduce the acid no. in raw crude oil?
The industry norm (and comments in other threads on this issue) seems to be to add corrosion inhibiting chemicals, but as this will be expensive I wonder if it's possible to flush out the acidic components by adding water and then removing it again through centrifuging?
I need to reduce it to 1.0 mgKOH/g from around 2-3 mgKOH/g...
Any comments appreciated!
25362 (Chemical)
2 Jun 05 10:12
One commonly applied method is diluting down the acidity by suitable blending with (not-necessarily sweeter) lower acid-number crudes.
As for naphthenic acidity, there are treating methods for the distillates, mainly kerosines. See, for example, www.merichem.com/Process/TechnicalArticles/Causticjet.htm 字串4
25362 (Chemical)
2 Jun 05 10:28
See also US Patent 6627069.
taylorg (Mechanical)
2 Jun 05 10:46
Thanks 25362, the patent you mentioned is very interesting and relatively new, which suggests that research in this area is still ongoing.
It looks like we need a treatment plant to effectively deal with the high acid number - not good news!
StoneCold (Chemical)
2 Jun 05 15:37
taylorg
I have neutralized acidic residue with potasium hydroxide and separated off the water but it was at the lab scale. Maybe this helps and maybe not.
StoneCold
0707 (Petroleum)
3 Jun 05 12:51
Naphtenic corrosion control is important when corrosion is over 5 MPY. 字串4
Naphtenic corrosion is mitigated by chemical treatment of the feed of vacuum and atmospheric columns through the injection of phosphorous organic composites, when the corrosion rates exceed 5 mpy, particularly in VGO and HVGO cuts. A good practice is blending naphtenic crude with lower TAN crude so that the feed crude mix has a sulphur contents of 2% and produces a TAN less than 1 in VGO and HVGO cuts. It is also important to make nickel and iron analyses in order to establish corrosion relations between the feed of the columns and those cuts. For corrosion monitoring is a good practice to install corrosion ER probes in turbulent piping flow zones with high velocity.
Regards
Luis Marques
visangio (Chemical)
7 Jun 05 6:27
Dear Taylorg,
the question you should first ask is "What is the cost of not processing an acidic crude and processing a normal crude oil to avoid corrosion problems?".
The price difference between an acidic and a normal crude oil is so big that any treatment cost is fully justified. 字串4
In aany case blending with a low acidity crude oil is an opportunity, but that depends by the type of supply to the refinery, otherwise, as said, the cost is very high.
Another solution to avoid corrosion is to use appropriate materials, austenitic stainless steel higher than 2 %, better 2.5 %, Mo.
Extraction with water is not feasible as very high pH is required, making the separation almost impossible (a naphtenate soap will be formed).
Corrosion inhibitors are finally the most economical way to handle those crude oils. Anyhow please rememebr that, apart of chemicals, appropriate monitoring tools must be applied.
Best regards
Vincenzo Sangiorgio
www.ge.com Vincenzo Sangiorgio
www.gewater.com
taylorg (Mechanical)
17 Jun 05 6:01
Thanks for your informative responses - extremely useful for a non-petroleum guy like me.
To elaborate a little, we are using this crude in a power plant before it goes anywhere near a refinery. It only has the BS&W knocked out before it comes to us. The plant is already installed and I doubt the materials will handle the Acid No. We will use approximately 2000 cubic metres of crude every week. 字串8
As extraction with water appears to be unsuitable your advice all points towards corrosion inhibitors and corrosion monitoring (incidently I came across an article in which BP recently and successfully trialed this at their Grangemouth refinery as they were looking to take on high acid feed stocks). I imagine this is going to be expensive and will require a chemical storage and injection plant to be installed.
Can anyone suggest a few companies experienced in this field and some likely costs of plant and chemical usage? Perhaps Baker-Hughs, Schlumberger etc?
I'm going to have to move quickly on this!...
Thanks & Regards
0707 (Petroleum)
20 Jun 05 4:33
When we start dealing with the processing of high TAN crudes we have received a good assessment from Baker-Hughes. There are others specialist in this matter such as Nalco Ondeo.
Field studies suggest that Naphthenic acid corrosion is prevented by the use of metals with +2.5% Moly (best is 317 SS with 3.5% Mo). Temperature - in general, corrosion rate of all alloys in the distillation units increases with increase in temperature. Naphthenic acid corrosion occurs primarily in high velocity areas of crude distillation units in the temperature-range 220 to 400 C (430 to 750 F). No corrosion damage is usually found at temperatures above 400 C (750 F), most probably because of the decomposition of naphthenic acids or protection from the coke formed at the metal surface. 字串9
Luis Marques
visangio (Chemical)
26 Jun 05 9:35
Contact also GE Infrastructure Water & Precess Technologies.
Vincenzo Sangiorgio Vincenzo Sangiorgio
www.gewater.com
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