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Feed Filter Chocking Problem At Diesel Hydrotreater

filter hydrotreater choke plugging deposits refinery fuji metallic sintered chemical cleaning

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#1 vectorangel


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Posted 12 January 2018 - 03:10 AM

Dear Sir,


We have been experiencing a problem at feed filters of Diesel Hydrotreater due to which filters get chocked frequently. New filters are chocked after ~10 days whereas washed filters have a running life of 2-3 days. We have been cleaning the chocked filters by first soaking them in 20% caustic solution at 70 oC for 50min, hydrojetting with Demineralized water, dipping them again in 12% Nitric acid for 50 minutes and finally hydrojetting. 


Filters are cartridge type with 25 micron sintered wire mesh. Feed is straight run gas oil from CDU column and light vacuum gas oil from VDU. In an analysis of the deposits, it was analyzed that majority of deposits consist of iron as Fe2O3 and nickel as NiO2 with little constituents of copper (CuO), Calcium (CaO), Mg (MgO), Chromium (Cr2O3), Zn (ZnO), Potassium (K2O), Sodium (Na2O), sand, silt and SiO2.


Despite the cleaning methodology being followed, service life of filters is very low. I want to know a better chemical recipe or a different cleaning method that will restore the service life of filters to its original condition. 


If anyone knows how to troubleshoot this problem, please let me know. If any further information is needed, do let me know. Thanks.




Edited by vectorangel, 16 January 2018 - 04:06 AM.

#2 PingPong


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Posted 12 January 2018 - 04:58 AM

Are you feeding vacuum gasoil to a diesel hydrotreater?

What kind of vacuum gasoil is that? Crude source, boiling range, density, viscosity, TAN, ASTM color, asphaltene content, et cetera?


In the absence more detailed information about processing scheme and feed properties and temperature, it could be that the filters are doing what they are supposed to do: remove solids from the feed.


The solids appear to be mainly rust and also some salts, so probably that is what you should focus on.


Why is there an increase in corrosion products from upstream piping and equipment?

Did the problem start soon after the refinery started operating on a different crude type with a higher TAN ?


Why are there salts, and even sand, in the vacuum gasoil feed?

Is there a problem with the crude desalter(s), possibly due to a change in crude type?


So focus on what changed in the operation of the refinery just before the problem started.


In any case do also daily filter tests on a vgo sample in the laboratory to determine exact amount and type of solids present.

Edited by PingPong, 12 January 2018 - 05:02 AM.

#3 Arsal


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Posted 14 June 2019 - 05:51 AM

Are your feed tanks blanketed?

When Feed tanks were cleaned last time?

Are feed tanks epoxy coated?


Mostly, source of rust is feed tanks.

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