Q & A > Question Details
Are there any differences between a naphtha hydrotreater and a diesel hydrotreater?
12/03/2018 A: Morgan Rodwell, Fluor Canada Limited, morgan.rodwell@fluor.com
There may be other differences than those mentioned by the other commenters, but they are all related. A naphtha hydrotreater needs to remove S and N, and will saturate olefins, but is unlikely to saturate aromatics because the pressures are too low for those reactions to proceed. Increasing severity in a naphtha hydrotreater generally reduces octane number for gasoline (which is why hydrotreating is usually done ahead of a catalytic reformer).
In a diesel hydrotreater, if there are a lot of aromatics, then pressures need to be much higher to saturate aromatics and increase cetane number. Sometimes, diesel hydrotreaters operate in two stages, one to remove sulfur and nitrogen and the second to saturate aromatics. If you have a very paraffinic crude, the running in a dewax configuration may be necessary as well.
05/03/2018 A: Sridhar Balakrishnan, Bharat Oman Refineries Limited , laksrid@yahoo.com
Differences between naphtha and diesel hydrotreaters are process conditions or variables of the hydrotreating , different , Naphtha hydrotreaters - temperature - 300 - 325 Deg.C , Pressure - 35 to 60 ( Atom ) , LHSV - 3.0 to 7.0 , catalyst cycle life - nearly more than 5 years. Diesel Hydrotreater - temperature - 350 - 400 Deg.C , Pressure - 75 -125 ( Atom ) , LHSV - Around 2.0 , catalyst cycle life - 3 years ( around) .
05/03/2018 A: Eric Vetters, ProCorr Consulting Services, ewvetters@yahoo.com
The process flow schemes are very similar, but the two processes have a bit different operating conditions. Diesel is higher in Sulfur than naphtha and the benzo and dibenzothiophene sulfur compounds found in diesel are much harder to treat than the sulfur compounds found in naphtha. As a result the diesel hydrotreater usually operates at a higher pressure and lower LHSV than a naphtha hydrotreater. DHT will typically perate at around 1000 psig reactor pressure and an LHSV of~1 to meet ULSD specs. An NHT will usually operate more like 600 psig with an LHSV of 4-6.
Much more NH3 and H2S is formed in a DHT than an NHT (unless the crude is really low sulfur) so a water wash is usually required on a DHT to limit ammonium bisulife and ammonium chloride salt formation. A continuous water wash is necessary much less often on an NHT.
The reactor delta T is normally much higher on a DHT than an NHT because the hydrogen consumption is also significantly higher in the DHT (more chemcial reactions going on to remove S & N and saturate aromatics). Sometimes DHT reactors employ a hydrogen quench to limit reactor delta T. NHT's are usually vapor phase reactors while in a DHT the diesel is either liquid or only partially vaporized.
02/03/2018 A: Ralph Ragsdale, Ragsdale Refining Courses, ralph.ragsdale@att.net
There are differences in pressure, temperature, LHSV, hydrogen consumption, and catalyst life. Some diesel units have a diolefins saturation reactor, feed filter, and/or recycle gas scrubber. E-mail me for a table from my workshop manual comparing the parameters of all hydrotreating applications.
02/03/2018 A: Ganesh Maturu, Reliance Industries Limitied, maturu.ganesh@gmail.com
Yes.... there are significant differences with respect to design and operation.
1. Naphtha hydrotreaters objective is to produce sulfur spec of <0.5 ppm and with less aromatic saturation.
2. Diesel Hydrotreaters objective is to produce sulfur spec of <10-50ppm and high aromatic saturation to improve cetane no.
3. Naphtha hydrotreaters reactors are gas phase reactors and Diesel HT are trickle phase reactors
4. Many more differences and we can write hundreds of differences between these 2 units.