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Our NHT reactor DP increased when we changed the light feed material, orginal feed case design is 55% paraffins but we change this feed to 72% paraffinic feed. No reactor inlet temp / outlet temp or pressure changed. H2 consumption 100nm3/hr gone up but not too high. DP increased to 1500mmh2o from normal one (5000mmh2o).
My question is, is high paraffin in feed is the problem or some another causes, if yes, then how?

Additional info:
Tank feed bromine was analized and we got 1.1 to 1.2 only and no olefins with new feed case.
 
Answers
17/06/2011 A: carlos hugo mendiondo, ypf sa, cmendiondoc@ypf.com
If the delta p is reversible , do you verify the changes in molecular weight of your 72 %parafinic feedstock? If It is less than design case , the gas volume flow ( G) will be increased in the same proportion and delta P is increased more still cause it is proportional to is G**2
05/04/2011 A: Thomas Wellborn, WellbornYX Corp, twellborn@wellbornyx.com
My guess is the paraffins are coking up the catalyst, in turn causing an increase in dP. Remember high N+A provides higher octane conversion at constant severity, so conversely higher paraffins should reduce the RONC of your reformate at constant inlet temperature. Has this happened? Paraffins in a diesel hydrotreater usually cause coking pretty fast, so my guess is the same result would be obtained in a naphtha hydrotreater.
24/03/2011 A: Virendra Kapoor, Petroleum Refining Consultants, vkkapoor9@yahoo.com
Your question needs additional clarification on delta P increase. It is written that delta P increased to 1500 mm of water from normal one of 5000 mm of water ? Actually 1500 mm of water is about 2.1 psi and 5000 mm of water is 7.1 psi. Please review.
24/03/2011 A: Virendra Kapoor, Petroleum Refining Consultants, vkkapoor9@yahoo.com
please refer to my answer dated 22nd instant. It was inadvertently written as increase in void fraction. Instead of that it has to be decrease in the void fraction of the bed that may cause increase in delta P due to scale or gummy materials deposited in or over the bed.
23/03/2011 A: Raghavendra Sangam, Libra Techcon Ltd., rsangam0504@yahoo.co.in
Check feed composition (PONA analysis) and compare the change over time.
Check any increase in S and N loading from feed which increase H2 consumption. If S and N loading has increased but H2 consumption has not, probably cracking/carbonisation is taking place which may be causing the pr drop increase.
The change in feed composition asks for change in H2 partial pressure. Check licensor's recommendations/operating manual and tune the reactor conditions and H2 flow accordingly.
Check whether catalyst is at the end of its life-cycle based on past history of MT throughput per Ton of catalyst norms.
22/03/2011 A: Ralph Ragsdale, Ragsdale Refining Courses, ralph.ragsdale@att.net
If there was a shutdown between feed types, scale could have carried over from the heater.
22/03/2011 A: Virendra Kapoor, Petroleum Refining Consultants, vkkapoor9@yahoo.com
NHT is normally vapor phase reaction. Change in Parrafin is not likely to affect delta P. If velocity increase occurs, void fraction increases due to foreign materials or gummy materials deposit there may be increase in delta P. Verify whether increase in hydrogen consumption was due to olefins? Olefins are not reflected by temp? Was bromine number/ bromine index checked. Any change in RG flow?