The Ammonia Storage and Delivery System (ASDS), developed by Amminex, has demonstrated an ability to nearly eliminate nitrogen oxide (NOx) pollutants from diesel engines. Called a “new generation” of NOx reduction technology, ASDS is designed ultimately to replace conventional tanks containing a diesel exhaust fluid (DEF) or AdBlue with lighter, high-efficiency cartridges containing a solid material called AdAmmine, also developed by the Danish company.
In December, Faurecia acquired a 91.5% share of Amminex, to intensify the development of this technology for both commercial vehicles and passenger cars. Faurecia has worked with Amminex since mid-2009 and previously owned 42% of the company.
“ASDS functions at lower exhaust temperatures, even in winter driving conditions. Moreover for equivalent quantities of ammonia, ASDS requires only half the volume than that required for AdBlue,” said Christophe Bouly, CTO of Faurecia Emissions Control Technologies.
One 11-L ASDS cartridge is comparable to 20 L of AdBlue/DEF.
Selective catalytic reduction (SCR) using liquid reductant is the most widely used method for reducing NOx emissions. Bouly believes ASDS has the potential to become “the new world standard for NOx reduction.”
AdAmmine consists of ammonia adsorbed in strontium chloride salt in a solid form. AdBlue, currently the most widely-used NOx reduction fluid, can be injected into the exhaust stream only at exhaust temperatures above 180°C (356°F), while ASDS has the ability to optimize SCR in lower exhaust temperature ranges—from 140-180°C (284-356°F), according to Faurecia.
The ASDS cartridges can be stored or transported safely at temperatures ranging from -40 to +80°C (-40 to +176°F).
How it works
The ASDS system begins releasing pure ammonia in gaseous form into the exhaust line within a few minutes after engine start-up. Faurecia describes how the system works: At ignition of the engine, the start-up unit is electrically heated. In less than 2 minutes the temperature reaches 60°C (140°F) and the salt releases pure ammonia on demand. The pure ammonia is routed under low pressure to the control unit. An electrical valve pilots the distribution of ammonia that is then sent to the exhaust line.
While the start-up unit is operating, one of the main cartridges that is larger in size is heated. When the main cartridge reaches its operating temperature, it takes over the release of pure ammonia from the start-up unit. When the engine is turned off, the distribution of the ammonia is stopped. As the temperature drops, the pure ammonia returns to its solid form and is again stored in the salt.
ASDS has been proven to reduce NOx emissions by up to 85-99% on more than 15 million km (9.3 million mi) of real-world use on buses. This compares to an average 32% NOx reduction with AdBlue in the same city-driving conditions. These findings are the result of monitoring hundreds of ASDS-equipped buses in Copenhagen and London, and comparing them with buses using AdBlue on the same streets.
Demonstration vehicles are also running in Germany, China and Korea. In total an estimated 400 vehicles are in operation today, with the total fleet exceeding 25 million km (15.5 million mi). Faurecia has supplied more than 25,000 refilled cartridges, roughly equivalent to 500 ton of DEF/AdBlue.
System cost on the vehicle is comparable to a DEF system, Dave DeGraaf, President of Faurecia Clean Mobility North America, told Truck & Off-Highway Engineering.
“ASDS has no injector and uses a simple steel nozzle. The ammonia flows in through a non-heated tube,” he explained. “Unlike the deposits left in the exhaust system from the liquid urea used in AdBlue/DEF systems, ASDS uses gas that does not leave deposits. This ultimately will allow a fleet owner to stay with diesel technology longer, and reduces the need to refresh the fleet frequently.”
Potential off-highway application
Faurecia showed the Amminex solution for commercial vehicles at the 2016 Paris Motor Show, as well as an ASDS system in a new format for diesel passenger vehicles. The company is also investigating other applications of ASDS, including for off-highway vehicles and high horsepower (HHP) engines used on ships and vessels.
“This is something that is still in development,” DeGraaf said. “We believe the same commercial-vehicle ASDS system that is used on buses and trucks today can be used for off-highway and marine when the engines are comparable in size. We are still exploring specific solutions for larger engines using the same core technology.”
For passenger cars, engineers have created a smaller package for ASDS that fits in the trunk or any other available space. Faurecia proposes offering a full line-up of cartridge sizes from 1 to 11 L. The smaller cartridges can be changed out by the driver in plug-and-play fashion.
What kind of weight savings are possible? “Light duty [vehicles] that currently use the 17-L AdBlue system would see a 30-40% weight reduction,” said DeGraaf. “In commercial vehicles that currently use the 40-L AdBlue system, the weight reduction is slightly lower at approximately 20%...Preliminary results also indicate that ASDS could potentially optimize fuel consumption in the range of 2%.”
Faurecia says the compact ASDS cartridges will be available for post-2020 passenger vehicles.
Ultra-low NOx regulations
Ultra-low NOx regulations are likely coming in the U.S. for heavy-duty on-highway engines beginning in model year 2024, lowering the allowable limit from 0.2 g/bhp-hr to 0.02 g/bhp-hr. DeGraaf believes ASDS can help achieve these targets with reduced impact on fuel economy.
“In-use performance in city driving is of high interest for the next step in U.S. legislation, in particular CARB,” he said. “ASDS can help enable high performance in real driving conditions—particularly in cities—without the use of exhaust heating strategies that are needed in DEF injection.”
In Copenhagen, for example, estimates indicate that buses have contributed to as much as 10% of the NOx pollution, DeGraaf noted. Faurecia’s data suggests that the 261 ASDS-retrofitted buses there have already collectively removed more than 45 tons of NOx from the air.
“It has a positive impact on both fuel economy and CO2,” he added. “Exhaust heat management typically consumes 3-5% of extra fuel/CO2 during light to medium load conditions. Since ASDS is not a liquid, it does not need catalyst heat management to function properly, which saves that fuel/CO2 consumption.”
Amminex employs 50 people at its headquarters in Søborg, near Copenhagen, and its 6500-m² production facility in Nyborg. Annika Isaksson, Amminex CEO, and Tue Johannsen, CTO and inventor of the ASDS technology, have remained in their positions following the Faurecia acquisition, to help lead the technology’s new stage of development.
Johannsen and other Amminex experts wrote an SAE Technical Paper in 2008, 2008-01-1027, in which they offer an initial look at the storage concept, including system design, performance data, and implications for vehicle integration.