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Kerosene Ht Feed Filter Dp Problem


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#1 agravatajay

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Posted 27 February 2011 - 05:43 AM

We have a Kerosene hydrotreater which is processing straight run light kerosene from crude unit to produce ATF. My feed conditions are : Temp at battery limit: 80-100 Deg C, pressure: 6.5 kg/cm2. Density: 0.804 @ 15 Deg C. Kerosene is being filtered by two basket type filter having 100 mesh (one stand by) (Filter temp around: 135-145 Deg C). We are facing a problem of frequent filter chocking, but filter element is clear, no dirt, no scale, no corrosion particles, you can say crystal clear like clean filter element, still having high DP.
what may be the reason of higher DP across filter?
Is there any chance of gum formation/ polymerisation (Because of additives in crude unit), which u can not see by naked eye, but may create DP?

Additional info:
Filter is getting chocked frequently. i.e. sometimes in 3-4 hrs (best achieved life 15-20 days). Once filter got chocked 16 times in 2.5 days. Dirty filter baskets are being cleaned by hydrojetting and followed by steaming.
Original design was of 25 micron (500 mesh), but because of frequent chocking filter mesh has been changed to 74 micron (200 mesh) temporarily. Filter element is of stainless steel.
Till date no adverse effect observed in reactor DP or heat exchanger fouling.

LK feed is straight run from crude unit.
which feed characterization study can be carried out to identify problem.

#2 Zauberberg

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Posted 27 February 2011 - 09:54 AM

What do you mean by saying "the filters are found clean"? After hydrojetting? Please explain. There isn't any PFD uploaded in your post so it is difficult to understand how the Kero loop is configured. At first you say "the filter is getting choked several times per day", followed by "we never found anything inside the filter that could cause plugging".

Furthermore, why there is a difference in Kero temperature at the battery limit (80-100 degC), and across the filter (135-145 degC)? Due to higher temperature, perhaps you might encounter vaporization of Kero while passing across the filter (and that would certainly cause higher DP) but we can't say more without knowing Kero properties (IBP/D86, Flash point) and the pattern of DP across the filter by time.

#3 agravatajay

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Posted 27 February 2011 - 01:08 PM

What do you mean by saying "the filters are found clean"? After hydrojetting? Please explain. There isn't any PFD uploaded in your post so it is difficult to understand how the Kero loop is configured. At first you say "the filter is getting choked several times per day", followed by "we never found anything inside the filter that could cause plugging".

Furthermore, why there is a difference in Kero temperature at the battery limit (80-100 degC), and across the filter (135-145 degC)? Due to higher temperature, perhaps you might encounter vaporization of Kero while passing across the filter (and that would certainly cause higher DP) but we can't say more without knowing Kero properties (IBP/D86, Flash point) and the pattern of DP across the filter by time.


Filter Found clean means when we remove basket from filter to Hydrojett it/clean it. but nothing found that seems to choke filter.

We having one exchanger just before filter so temperature is more at filter than B/L.

Kero feed IBP:143 Deg Cand FBP:256 Deg C.

Our main concern is filter frequent choking problem.

#4 Zauberberg

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Posted 27 February 2011 - 02:59 PM

Can you upload the DCS trend, showing filter DP and Kerosene flow over 24 hours period?

#5 Chellani

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Posted 01 March 2011 - 03:28 AM

Kerosene itself should have very low tendency for polymerization / gum formation and on top of that your Kero is straight run. If it would have been coming from cracker / coker, there would have been chances of gum formation but for staright run; I don't expect that. I guess Bromine number can give an indication of unsaturates and hence tendency for polymerization.

The heat exchanger mentioned by you (available in the upstream of filter) can add to some deposits because of corrosion (or rather erosion) but you've also mentioned that no impurities were found.

Similar to Zauberberg, I am also not clear on what are you cleaning by hydrojetting which reduces your delta P across filters.

I've invested (or rather wasted) lot of manhours in investingating bigger problem of higher reactor delta P and have analyzed lot of variables but never found the root cause. I have seen filter clogging in case of heavy feed (VGO) but a thick layer of coke (or rather polymerized product) was easily visible on filters.

So all the best and do share your experience if you can resolve the problem.

#6 agravatajay

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Posted 04 March 2011 - 10:07 AM

Kerosene itself should have very low tendency for polymerization / gum formation and on top of that your Kero is straight run. If it would have been coming from cracker / coker, there would have been chances of gum formation but for staright run; I don't expect that. I guess Bromine number can give an indication of unsaturates and hence tendency for polymerization.

The heat exchanger mentioned by you (available in the upstream of filter) can add to some deposits because of corrosion (or rather erosion) but you've also mentioned that no impurities were found.

Similar to Zauberberg, I am also not clear on what are you cleaning by hydrojetting which reduces your delta P across filters.

I've invested (or rather wasted) lot of manhours in investingating bigger problem of higher reactor delta P and have analyzed lot of variables but never found the root cause. I have seen filter clogging in case of heavy feed (VGO) but a thick layer of coke (or rather polymerized product) was easily visible on filters.

So all the best and do share your experience if you can resolve the problem.



same here its like mystery,
and by the way we are cleaning is the filter basket (we have baske type filter).
K and if We found something I will same post it here.
Thanks lot guys.




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