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I am working in Diesel Hydro Desulfurization unit where diesel is produced in sulfur less than 200 ppm. after the reactor the effluent contains , Hydrogen gas . sour water an diesel. diesel is further sent to stripper where light unstabalized naphtha is separated and diesel is sent to water removal. Operating conditions of stripper are 245 C inlet , 156 C overhead & 240 bottom temperature. Operating pressure is 8.1 kg/cm2. MS steam is used with pressure 11 kg/cm2 and temperature 195 C.In the downstream of stripper diesel heat exchanges in exchanger , Fin fan coolers , trim cooler and finally go to Diesel Coalescer for moisture removal at temperature 56 C. We are facing frequent chocking of coalescing cartridges with rust particles. i need to pin point the possible location where corrosion can occur and why in order to avoid frequent chocking of cartridges with black rust particles.
 
Answers
26/04/2017 A: Khaled Alqasem, Jordan Petroleum Refinery Co, khaled.alqasem@hotmail.com
You have to carry out particulate analysis to identify the source of this particulate and to select the suitable filtration degree , boot water analysis or from the coalescer is very helpful to identfy corrosive species , personally I faced this problem in Kero strippers due to over stripping and water condensation and dissolving corrosive species , anyway if there’s no preventive solution to mitigate corrosion , then i thing automatic backwash is cost effective and very helpful in this case.
PS. please check Diesel acid number
08/10/2014 A: Satish Angadi, Haldor topsoe, satish.angadi@gmail.com
I guess there could be two or three possible sources.
1) Check that you wash water flow-rate and quality is as per PFD/design. This will remove source-corrosive matters(NH4Cl, NH4HS) coming to stripper.
2) Check that column top temperature of 156 C is at least 10 C above water dew point.
3) How is the water in stripper OVHD boot, do you have corrosion there? what is pH and iron content there? do you have corrosion inhibitor injection in stripper top? do you use it properly?
(I assume that this problem is recent development and not since plant-startup.)
25/09/2014 A: keith bowers, B and B Consulting, kebowers47@gmail.com
200 PPM of sulfur in diesel is quite high by current specifications (often <10 PPM) I suggest you obtain samples of the reactor effluent before and after the naphtha stripper. Be sure and keep the samples pressurized in a 'sample bomb' to avoid loss of H2S. Then test the samples for H2S. I suspect you will find H2S in the stripped diesel. Wet H2S in diesel is a very corrosive fluid and I would expect severe corrosion of carbon steel.