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I am process eng. at diesel hydrotreater unit. Recently we decided to treat blending naphtha in diesel unit
spec of blending naphtha: IBP=145 dry point=195, sulphur in feed= 2000 ppm, sp.gr of feed is= .7640
flash point=35 deg c. We are planning to produce solvent aw402 from blending naphtha but we have two questions:
1) catalyst volume is 75 m3 and we are worried about LHSV (design capacity for diesel is 18000 bbl/day and minimum throughput of unit is 60%in design case).
Is minimum 200 m3/hr for new feed OK or we can process lower feed?
2) What's the minimum inlet reactor temperature to hold minimum cracking because we have problem to set flash point in stripping section. Can we reduce temp. below 290 deg c ?
 
Answers
25/09/2013 A: Virendra Kapoor, Petroleum Refining Consultants, vkkapoor9@yahoo.com
1800 bbl/day leads to about 1.6 LHSV for diesel. SRN hydrotreating can be carried out in the range of about 3 to 8 LHSV depending on hydrogen partial pressure and temperature Keeping in view of the product sulfur temperature may be kept in the range of about 280 to 330 degree C at reactor inlet for SRN. Naphta in the reactor may be in vapor phase. It is important to look into the simulation for stripper performance as suggested by Mr.Alen Goelzer
21/09/2013 A: Ralph Ragsdale, Ragsdale Refining Courses, ralph.ragsdale@att.net
I agree with Alan. Recycling product is always a reliable option when a unit is too large for the available feed rate.
11/09/2013 A: Alan Goelzer, Jacobs Consultancy, alan.goelzer@jacobs.com
To operate at thruput percentages below 85% of base Am3/hr flow through high pressure charge pump, I always recommend recycling stripped product from the product stripper back to suction of the HP charge pump. Keeping oil flow at 85%-100% of base design BPSD and treat gas flow at 85%-100% of base design Nm3/hr will minimize incidental thermal cracking in the high-pressure charge heater and in the HT reactor.
Stripper operations should be simulated on computer to determine what operating conditions work with hydrotreated heavy naphtha.
Reactor outlet temperature below 290C might be "too cold" if catalyst is aged. On the other hand, incidental thermal cracking should be low below HT RxT,outlet = 330C-340C for heavier naphtha if oil flow and treat gas flow are sustained near base design values---especially if RxP,inlet is reasonably high.