Challenges facing refiners
Bob Williams' excellent overview "Refiners' future survival hinges on adapting to changing feedstocks, product specs" (OGJ, Aug. 11, 2003, p. 20) touched on several challenges facing refiners. On page 32 there is a quote, "The biggest challenges (in desulfurization) besides dealing with a more severe operating mode ... may be how to dispose of unwanted refinery streams." Treating the unwanted 640-700º F. boiling range hydrocarbons will largely determine refiners' ULSD investment costs. FCC LCO and Coker LCGO contain more than 75% of the difficult-to-remove sulfur and the majority of the nitrogen compounds that drive up ULSD treating costs. Furthermore, as US refiners process more of the Canadian and Latin American extra-heavy crudes, and synthetic crudes, the 640-700º F. cut from the crude unit also contains increasing amounts of the nastiest sulfur species and more nitrogen compounds.
Most often the solutions quoted include upgrading the ULSD diesel hydrotreater to process the 640-700º F. or undercutting the ULSD diesel hydrotreater feed streams to eliminate the 640-700º F. from the ULSD hydrotreater. Yet, as you noted there is not enough fuel oil to even remotely take the volumes produced, and undercutting drives up feed rates to the FCC. Because most refiners have little additional FCC capacity, increasing its feed rate further raises investment. Moreover, feeding these hard-to-remove sulfur and nitrogen compounds to the FCC doesn't destroy them, but simply concentrates them in the FCC LCO product stream.
Williams' article noted that the 640-700º F. material must go to ULSD pool. Currently there is no proven low-capital cost technology to treat this material. Hydrocracking or high pressure hydrotreating are the most-often discussed solution. Because these technologies are costly, minimizing the volume of 640-700º F. hydrocarbons reduces investment. Refiners need to consider solutions that minimize the volume of 640-700º F. material that must be treated. Improving upstream fractionation in the crude unit and coker and cat feed hydrotreater (CFHT) increases recovery of hydrocarbons containing the easy-to-treat sulfur compounds for ULSD pool and minimizes FCC feed. Because treating cost for the 640º F. minus hydrocarbons is low, these should be fed to the ULSD hydrotreater, not the FCC. Furthermore, the 640-700º F. should be fed to CFHT where they can be treated and fractionated or to FCC where cracking reduces volume by 70-75%.
Simply put, feeding 1,000 b/d of 640-700º F. hydrocarbons to the FCC reduces it to 250 b/d or less of LCO. The heavy 640-700º F. LCO material should then be fractionated in the FCC into a heavy LCO product for severe treating. While this material is very poor quality and high in difficult-to-remove sulfur and nitrogen, this approach greatly reduces the volume which can lower overall investment.
Scott Golden
Chemical Engineer
Process Consulting Services
Houston
Running out of oil
Why shouldn't you break the most important story of the century? Please tell your readers that our world faces a crisis of unimaginable consequences: We are running out of oil.
For well-researched information, please read the "Coming Oil Crisis," by Colin Campbell, published by Petroconsultants (England), 1997.
I also recommed "Hubbert's Peak, the Impending World Oil Shortage" by Kenneth S. Deffeyes, Princeton University Press, 2001, and "The Hydrogen Economy," by Jeremy Rifkin, Penguin Putnam Inc., 2002. All of these men are well qualified to write on the issue.
Virtually all independent experts say world oil production will peak about 2005. The peak is critical, because that is the time when rising world demand separates from declining supply, and prices go very high. Oil company experts and the Department of Energy put the peak between 2010 and 2020. No respected expert puts the peak beyond 2030.
Regardless of who is right, our urgent task is to move our civilization off of its dependence on oil. In the past 10 years, we have made no progress on vital energy conservation, except for a dip in energy use in 2001 due to economic factors. Also, we have made little progress on the development of alternative fuels and energy systems.
Oil is still essential to our way of life, because it provides nearly all of our energy for transportation. It also provides some of our heating and electric power needs. Oil is a vital feedstock for products for our way of life.
Thomas S. Dickerman
Engineering Consultant
Daly City, Calif.
