Q & A > Question Details
1. VGOHT is processing Hot Feed from DCU & LVGO/HVGO/HGO from CDU-VDU and combined Crack + Straight Run components from Feed Stroge Tank. I would like to know about quick inference / thumb rule to access %Crack Components in Feed from Sorage Tank by monitoring Reactor Profile and Hydrogen Demand.
19/06/2013 A: Alan Goelzer, Jacobs Consultancy, alan.goelzer@jacobs.com
Simple answer is the percentage heavy coker gas oil in heavy distillate ["VGO"] mix going into a VGO Hydrotreater Unit or Cat Feed Hydrotreater Unit can be very approximately inferred from the deltaT rise across the top catalyst bed. Large share of unsaturates [giving Bromine Number test response] will undergo hydrosaturation in the top catalyst bed with substantial exotherms. Unfortunately, significant amounts of "easy sulphur" will undergo HDS so the deltaT rise is composite of "Easy HDS" and HD-Br# reactions.
If HCGO is NOT almost exclusively hot transferred from DCU to CFH but also routed into feed storage, the differences in Bromine Number test response of hot transfer feeds and storage feeds may not be great enough to even infer a percentage.
Note best practices call for maximum or 100% direct transfer of HCGO from DCU to CFH.
18/06/2013 A: Ralph Ragsdale, Ragsdale Refining Courses, ralph.ragsdale@att.net
You can develop a curve by plotting the bromine number of the material from tankage vs total make-up H2 flow.