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Crude oil desalter problem:
It is observed that during normal running of Crude oil desalter(2 stage in series), the Amperage increased from 45 to 90Amp. It was also checked that there is no water shot with crude(i.e. < 500PPM H2O). Immediately wash water stopped, still current doesen't comes down. Hence, wash water resumed and observed current at higher side. Evev, the crude oil type processed is also the same as earlier. What could be the reason for high current and suggest solution to bring down current?
 
Answers
15/12/2018 A: Jayaraj Jayam, Chennai Petroleum Corporation Limited, njayaraj@gmail.com
You have mentioned that there is no water shot and no change in crude oil type or characteristics. It is hard to find solution with the available data. However, try to attempt with the following suggestions:
1. Check the quality of your de-emulsifier, its dilution rate and dosing rate are as per designer recommendations.
2. Ensure desalting water flow is not more than 6% of your desalter feed.
3. If mix valve dp is more than the design value or > 1.0 kg/cm2, limit it to 1.0 kg/cm2.
4. Sludge from crude tank can cause this kind of problem as its density falls in between water and crude oil. Hence it is carried along with the outlet crude oil as the density difference is not sufficient to settle.
5. Raise desalter temperature to raise settling velocity of water particle.
6. If the level indication is displacer type, drain the level troll to eliminate the possible settled sludge as it will lead to erratic level.
7. Do not forget to do de-sludging operation.
8. Last but not least, at times it helps, that is just switch off the electric grip power, pause for a few minutes and then switch on. This may disrupt the rag layer closer to the grid.
12/12/2018 A: Sam Lordo, Nalco Company, salordo@comcast.net
if both stage see a increase in amperage then it is possible the crude itself is conductivity, no much you can do if that is the case
Another item could be high metal content, or polar materials
Unless the water content you quote is karl fischer you may have a tight emulsion, or water that is bound up in the crude.. a tell tail sign of this would be if only the first stage showed the elevated amps
12/12/2018 A: GAURAV BURDE, BHARAT OMAN REFINERIES LIMITED, burdegaurav88@gmail.com
Caary out the desludging activity and operate the desalter with low interface level. Check tri-cock when reducing interface level.
12/12/2018 A: Vijay Beleri, Rateau energy systems, v_beleri@hotmail.com
Is this observed only in the first stage?. If so it could be an increased rag layer that you are drawing higher current. How many transformers per vessel and what are the ratings. Is wach level of electrode powered by 1 transformer. Or each transformer powers 1/3rd of top 1/3rd of middle and 1/3rd of bottom grids.