TransForum Vol. 4, No. 1

ARGONNE SCIENTISTS TEAM UP TO DEVELOP NEW DIESEL REFORMER

Argonne's Di-Jia Liu conducted extensive testing of the diesel reformer; his experiments are the first to show that an autothermal reformer can be operated without vaporizing diesel fuel.

Sometimes, the road to scientific discovery is a marathon: a scientist diligently works alone in his laboratory for years until — eureka! — he hits upon the solution to splitting an atom or freeze-drying coffee. More often, though, researchers work together as a team and build on the knowledge and discovery of those who have come before. So it was in the case of Argonne's new technology to reform diesel fuel for use in fuel cell applications.

The first efforts began when a team of scientists led by Michael Krumpelt in Argonne's Chemical Engineering (CMT) Division developed a new type of sulfur-resistant catalyst for use in fuel processors that efficiently converts a variety of fuels — including methanol, natural gas, and gasoline — into a hydrogen-rich gas for use in automotive fuel cell systems. The catalyst was named one of the top 100 technological innovations of 2001 by R&D Magazine.

Getting the reformer to convert diesel fuel to hydrogen — a process for which there is a substantial commercial market (see sidebar) — posed a whole new set of challenges because diesel is difficult to vaporize. The vaporization requires high temperatures, which lead to pyrolysis and coking (carbonaceous deposits). Also, the conversion reaction to hydrogen from diesel requires three things — fuel, water/steam, and air — that must be present in specific proportions and must be very finely mixed. The key to solving these challenges is the kind of nozzle that is used in the autothermal reactor. So, building on the success of CMT's reformer catalyst and sponsored by the U.S. Department of Energy's Office of Hydrogen, Fuel Cells and Infrastructure Technologies, researchers Rajesh Ahluwalia and Vince Novick in Argonne's Nuclear Engineering Division designed a new nozzle to overcome the limitations of existing nozzle technology for diesel applications: namely, mixing and dispersion. Because the three feeds (high-temperature steam, air, and fuel) cannot be premixed, the trick is to mix them in situ — right at the tip of the nozzle — to provide a uniform droplet size and dispersion across the catalyst bed.

Back in CMT's laboratories, another team made up of Tom Kaun, Candido Pereira, Kai Liao, Dan Applegate, and Sheldon Lee took the new nozzle, combined it with the Argonne catalyst, now commercially available from Süd Chemie, Inc. (under a licensing agreement with Argonne), and designed a reactor setup that would allow Argonne to test the nozzle on an engineering scale.

The reactor team then turned to CMT's Di-Jia Liu, who conducted extensive testing of the reactor and generated data revealing that diesel can be converted to hydrogen by using the new nozzle. These experiments are the first to show that an autothermal reformer can be operated without vaporizing diesel fuel and therefore, without having to solve the kinds of problems that vaporization causes. According to CMT's Shabbir Ahmed, "The technology proved a success on three fronts: temperature and product distribution, product composition, and sustainability. Under typical operating conditions, we can sustain operation of the reactor for 5-6 hours. And we've done it for many, many days."

For commercial applications, the diesel reformer technology has a way to go. Argonne needs to test the reformer over thousands of hours. Researchers have obtained substantial industry input in the form of information about priorities and potential constraints, and the new nozzle technology and the data obtained thus far represent a big step forward.