Host of advances help refiners cut ULSD costs

Diesel Fuel News,  April 23, 2003  by Jack Peckham

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San Antonio -- Technology vendors continue to discover or refine techniques to cut the cost of producing ultra-low sulfur diesel (ULSD), according to technical presentations to National Petrochemical & Refiners Association (NPRA) meeting here.

Some examples:

* Linde-BOC Process Plants is now completing a novel "Isotherming" reactor at Giant's Ciniza, N.M., refinery (see Diesel Fuel News 8/5/02, p15), enabling the production of ULSD and "premium diesel" thanks to a 5-7 point boost in cetane.

Giant's feed to this new reactor is fairly typical of many U.S. refineries, a 60/40 mix of straight-run and light-cycle oil with total sulfur around 2,100 ppm.

"Based on the experience with Giant and detailed cost estimates, the estimated cost to the refiner (including catalyst and installation) of an IsoTherming retrofit to convert an existing 15,000 b/d diesel hydrotreater from a product-outlet sulfur specification of 500-ppm [sulfur] to 10-ppm is about $300/barrel," Linde-BOG process engineering director Ron Key explained in an NPRA paper (AM-03-11) here.

The "IsoTherming" unit has advantages of relatively modest size, modest increase in hydrogen consumption, a favorable boost in cetane, reduced aromatics and can boost ULSD product yield.

For the Giant refinery, Linde took the unusual step of moving directly from pilot-plant to commercial scale -- a 162,000 times scale-jump. Engineering, design and construction took only 12 months from contract award. Downtime for refinery retrofit is "less than one week plus the usual time for catalyst sulfiding," Key said.

While this scale jump might seem a huge leap of faith, commercial pressure to demonstrate technology at commercial-scale right now is critical since many refiners are about to finalize their ULSD process lans.

"Installed in the pre-treat position in a ULSD application, the IsoTherming unit will account for 90-98% of the sulfur removal and 70-90% of the hydrogen consumption while containing only 15 to 30% of the total catalyst volume," Key said.

The two-stage scheme also allows refiners to avoid the high cost of upgrading or replacing existing low-pressure hydrotreaters.

The unit is about to come on-line next month. Catalyst deactivation rates could be known by early summer, thus giving refiners another timely opportunity to make a decision about possible application of "IsoTherming" at other refineries.

* UOP just reported 10 new ULSD refining projects in design/construction all over the world, including two in India, one in Africa, two in the Middle East and one in South America. This is in addition to eight other recent UOP projects that have enabled ULSD production today -- two in India, one in Africa, three in the U.S. and two in Europe.

In a paper presented here (AM-03-119), UOP technology manager Ronnie Maddox cited numerous examples of recent UOP innovations in "Unicracking" and "Unionfining" processes to "minimize the capital investment required to revamp existing assets."

Among these are new reactor designs, reactor internals, separation schemes, process schemes and co-processing. One featured innovation is the use of an "enhanced hot separator" design that can boost the capacity of existing hydrocracker or FCCU pretreater or mild hydrocracking unit. Another is the new application of "divided wall columns" to boost ULSD yields.

In one case study at Wynnewood Refining, UOP determined that it could achieve a revamp at well under 60% of the cost of grassroots diesel hydrotreating, with additional benefits of "shorter implementation time, lower utilities, reduced manpower and maintenance costs, and no additional plot space required."

* Lyondell Chemical unveiled a hydroperoxide-based "oxidative de-sulfurization" (ODS) process for refiners that lack hydrogen to make ULSD.

"As a result of the mild process conditions, the capital cost required to install the process is reduced" to an estimated $600-750 per daily barrel, Lyondell's new product commercialization manager Frank Liotta explained in a paper (AM-03-23) here. "This estimate assumes the unit is build on a cleared site, includes all inside battery limits and 'project-specific' offsite battery limits costs such as oxidant feed tanks.

"Based on our current estimates, we expect that the cash operating cost for a unit taking today's low-sulfur diesel fuel to ultra-low sulfur diesel with less than 10-ppm of sulfur to be less than 2.5 cents per gallon," including the cost of oxidant, all utilities, labor, taxes and insurance.

The company aims to build and operate a demonstration-scale unit of 100 to 1,000 b/d "in late 2003 or early 2004" or possibly move directly to small-scale commercial size, he said.

Lyondell's process differs from some other proposed oxidation technologies that use hydrogen peroxide and recycle an organic acid co-oxidant.