Q & A > Question Details
In case of heavy residue upgrading, we are encountered with vacuum residue as feed. The main features of this feed especially about contaminants and problematic materials are as below:
Total sulfur>4.5 wt%
Conradson Carbon >25 wt%
Ni+V >500 ppmwt
Nitrogen ~ 1 wt%
We have two cases for VR upgrading project, One is RCD+RFCC and another is HOIL(Hydrocracking)+FCC. Both of these cases use huge amount of fresh catalysts because of high possibility of catalyst deactivation and poisoning. So the operating cost should be high.
Is this rational to charge such a feed to the catalytic system directly or is it better to use the process to somehow get rid of metals at least? If we need to use the solvent deasphalting system at the upstream of two before-mentioned cases and draw off about 20% of feed as pitch, we will succeed to lower the operating cost and increase the reliability of catalytic system because of the elimination of the major part of the metals. But in the opposite side, we have missed 20% of primary feed as pitch that it is a low value product. So the profit margin of the residue upgrading cases will decrease. However, as a second question, can we miss 20% of feed charge at the expense of increment of catalyst life cycle?
 
Answers
11/07/2016 A: Saleh Daryabari, Senior Process Engineer of RCD and RFCC, Arak Refinery, daryabari@gmail.com
It is quiet challenging feed, especially for fixed bed residue hydrotreating unit. For 500 ppm Ni+V the catalyst consumption would be very high and also life cycle is very short. For your case based on unit severity, the life cycle for fixed bed residue hydrotreating unit would be 4 to 6 months, so by considering catalyst change out time, it would not be economical. Also for ebullated bed hydrotreating this feed very challenging and tough and even by reliable operation, the catalyst consumption is too much.
By applying solvent deasphalting, as a rule of thumb you can get rid of 80% metals and 50% of Nitrogen by 80% DAO yield, and significantly improve the life cycle and decrease catalyst consumption in both residue hydrotreating and RFCC units.
As an option you can consider coke fired boiler in your project and use 20% pitch to produce utility for upgrading units.
03/07/2016 A: Ralph Ragsdale, Ragsdale Refining Courses, ralph.ragsdale@att.net
As you have noted, there are advantages and disadvantages to each option. From the many studies on the subject, these factors have emerged:
• Unless the resid hydrocracker can achieve 80 % conversion, other routes will have the best economics.
• The HDS/RFCC route can produce the lowest sulfur content in heavy fuel oil.
• Delayed coking has the best payout and can handle the worst crudes and the coke can be sold.
01/07/2016 A: NS Murthy, GE, murthy.ns@ge.com
With feed (vac residue) having high metals, it could worth looking at super critical deasphalting process to throw away bulk of metals and high asphalt content from feed which saves both hydrogen and catalyst cost. Further, if there is road asphalt (paving grade bitumen) need exists in the region where this refinery is situated, it will another straight value creation of the asphalt rejected in this unit. Alternatively, simply go for Coker for the vac residue (which will shed all the metals and asphaltenes) in Petcoke (fuel grade) and take the distillates for subsequent hydro conversion / FCC. Of late modern coking technology operating on concepts like zero recycle, ultra low pr coke drum, etc. can maximize the distillate yield. In case your refinery is lube base stock producing, then deasphalting is a better route to make bright stock lubes which are higher value too. Good luck.
30/06/2016 A: Morgan Rodwell, Fluor Canada Limited, morgan.rodwell@fluor.com
Solvent Deasphalting can be a useful method to remove refractory materials from the oil that don't convert well in hydroprocessing or RFCC processes anyway. On top of the catalyst consumpion, attempting to convert asphaltenes via hydroprocessing will have very high hydrogen consumption, and most hydrocracking technologies can't convert past about 80% in any event, and these high CCR feeds just make coke in the RFCC and make heat and waste gas. The only downside is that you need an outlet for asphaltene, either in asphalt, or a gasification unit.
30/06/2016 A: Keng Chung, Well Resources Inc., kengchung@hotmail.com
Consider SELEX, the game-changer commercial technology for selectively removal of asphaltenes. See the following publications.

PTQ, Q4, 2006, p99-105
OGJ, April 5, 2010 issue, p52-59
OGJ, June 6, 2016 issue, p70-77
OGJ, January 20, 1997 issue, p66-69

The RCD and Ebullated BED Hydrocracking are "catalytic coking" processes. See Fuel, 2001, v80, 1165-1177. It all comes down to the economics of 1) remove the "nasties" and process the "cleaned" residua using the conventional packed bed hydrocracker, vs 2) catalytic coking followed by disposal of unconverted pitch (not to mention lots of process operability problems, such as fouling).