Q & A > Question Details
We are processing local crude in which sulphur content is very less....Light naphtha is being separated from pre-flash tower...for corrosion control we are using filming amine...the iron content in boot water of naphtha reflux drum is within range...but chlorides are reporting more that 50 ppm... we are also using wash water that is recycling from booth water to the inlet of overhead condensers....what should be the maximum allowable range of chloride content in naphtha reflux drum?
19/05/2014 A: Sunderam Nagar, ALBEMARLE CATALYST CO BV, snagar31@gmail.com
A important information of salt in crude ex desalter is not provided, thus the first point to start is the desalter.
1) Check the emulsion breaker, increase the dosage if possible possible 4-6ppm, increase the amount of wash water addition to desalter, this will help the salt in desalted crude to come down. Tweak the mix valve deltaP to get the minimum BS&W in the crude ex desalter.
2) Do you add ammonia or a Neutralizing amine, this option is better than adding caustic. Add around 10-15 ppm of Neutralizing amine in the overhead of Atm Column.
3) Check for the concentration of Filming amine, in general the filming amine molecules ar heavy and dilution with naptha at 1:30 is best needed for a uniform layer of filmer over the internal surface of the header.
4) Check the recycled wash water quality.
5) The max allowable range of chloride in naptha reflux drum should be less than 20 ppm. For a crude with less sulphur content it should be anywhere between 7 to 14ppm.
15/05/2014 A: Sunderam Nagar, ALBEMARLE CATALYST CO BV, snagar31@gmail.com
In my view, a neutralizing amine is to be added in the overhead system to neutralize the acid species present in the vapours. The Iron levels will be giving wrong information, as this can be a classic case of pitting corrosion happening in the overhead exchangers. Depending on the crude, the maximum limit sof Chloride content in the Naptha reflux drum should be 20ppm, ( in light crudes it varies from 7 to 14 ppm) and heavy crudes from 21 to 35 ppm). Caustic should always be avoided and can be taken a a last resort if the problem is not solved. Also check for Tramp amines and the Chloride content in the Desalter Wash water and Overhead Wash Water. At this temp and pressure I dont think any Phantom Chloride would be present.
05/04/2014 A: ROBERT BOIT, KENYA PETROLEUM REFINERIES LTD, robert.k.boit@gmail.com
Try the following:
1. introduce/increase caustic injection on the crude train before the pre-flash tower.
2. reduce the amount of recycled booth water and increase the fresh stream of water injection before the desalter.
3. reduce further the temperature of the recycled wash water.
4. confirm also the levels of the booth water, maintain minimum level allowed
Hopefully this might help.
04/04/2014 A: Celso Pajaro, Sulzer Chemtech, celso.pajaro@sulzer.com
Have you tried adding slow concentration caustic into the crude after the desalter before the preflash? this should help you to reduce chlorides. You have to be careful to avoid overdose, so every day you should adjust caustic injection