In the industry’s quest to develop durable and cost-effective diesel emissions systems—particularly potential alternatives to urea injection—engineers at NxtGen Emission Controls believe they’re on to a significant solution. They are encouraged by recent progress made in marrying NxtGen’s proprietary syngas generator system with the latest diesel-particulate filter (DPF) technology from the ceramics division of Japan’s Ibiden Co. Ltd.
“From our back-to-back tests we know there’s a 30% fuel savings during the trap regeneration process using syngas, rather than injecting diesel [into the DPF for trap regeneration],” NxtGen President and CEO Jeremy Holt told AEI.
“We can do the trap regen in about half the time it takes to do conventional post-injection using diesel fuel,” he said. “And we believe our process will equate to up to 3% real-world fuel-economy improvement for the vehicle.”
Vancouver, Canada-based NxtGen is developing its novel syngas-based emissions-control system for a wide range of diesel-engine displacements. Initially it is targeting medium-duty diesel retrofits—potentially a huge market for vehicles made 1990 and later. Dynamometer testing to date is aimed at validating the syngas system’s capability of meeting the more stringent U.S. 2010 heavy-duty emissions regulations.
The syngas technology—the term is an abbreviation of “synthesis gassing”—is derived from a petrochemical-industry process. Its primary hardware is the syngas generator, a stainless-steel cylindrical chamber mounted near the vehicle’s fuel tank. The generator combines a percentage of diesel fuel with an oxidant (air or exhaust gas) to produce a highly reactive composition of H2 and CO. The gas is ideal for use in diesel exhaust aftertreatment for regenerating lean-NOx traps and particulate filters.
Compared with conventional trap-regeneration strategies involving late fuel injection, NxtGen’s syngas process effectively decouples trap regeneration from engine operation.
The high concentrations of H2 have proven to be an effective reducing agent, while allowing lower regeneration temperatures. This helps improve the system’s long-term durability, according to NxtGen founder and Vice President of Technology Erik Johannes (see April 2008 AEI, p. 108).
Holt said the simulation- and bench-test program conducted by Ibiden using current and advanced iterations of that company’s silicon-carbide (SiC)-based filters adds to test results from several catalyst manufacturers. Those results, he said, have shown the ability of the syngas generator to reduce DPF platinum loading by up to 60%.
“There’s a really good value proposition coming out of the test work that’s being done,” he said.
NxtGen testing using Ibiden’s advanced SiC DPF showed total engine fuel consumption reduced by an additional 2%, compared with the current filter (both filters had equal soot-mass limits). Holt noted that the filter’s design, along with the advanced SiC material, allows it to capture and safely regenerate greater amounts of particulate matter. This effectively extends the duration between trap-regeneration events.
NxtGen also is well along in proving out the trap-regeneration strategy for idle conditions. “With low-temperature exhaust, the DPF regeneration is a key technical problem,” Holt explained. “We can do active regen down to the 200°C range. Theoretically, we can start to create heat in the exhaust at 150°C with the syngas.”
Holt describes NxtGen’s design for the medium-duty application as “mature.” The company is currently installing equipment in place at its manufacturing and applications center in Wixom, MI, for assembly of the syngas generators, in anticipation of getting through the U.S. EPA verification process.
“It’ll be low volume to start, for the retrofits,” he said. “The population of diesel vehicles in North America that can be retrofitted is huge. We’ll start by addressing 6.0- to 9.0-L engines; those from the mid-1990s to the 2003 range are prime targets for aftertreatment retrofits.”
System durability is proving to meet or exceed the company’s expectations, Holt noted.
“The EPA test takes you to 1000 hours on the vehicle, then you have to do an EPA test to the FTP cycle on a dyno,” he explained. “We’re running twice that without problems.“
The company is racking up real-world testing hours as well. Vehicle applications include a light-duty box van with the DPF technology and syngas generators running delivery cycles “with hundreds of hours on it” and a number of test fleets in Canada, the identities of which Holt would not divulge. One is a transit bus authority.
NxtGen also is collaborating with aftermarket diesel-equipment specialist ATS Diesel Performance. The two companies unveiled a demonstrator vehicle at the recent SEMA Show that combines the syngas-based emissions control system with various ATS engine-performance tweaks.