Powertrain engineering specialists FEV are showing off a number of new technologies at the SAE World Congress this week including this new NOx reduction system for diesel engines. The basic principle of the Solid SCR is the same as the urea injection systems found on most of the new 50-state legal diesel vehicles coming to market. Ammonia is reacted with the NOx in the exhaust gases to convert it to nitrogen and water. Where it differs is the source of the ammonia. Instead of an aqueaous urea solution that is injected into the exhaust stream, this one uses a solid known as a ammonia carbomate that is a byproduct of fertilzer production.

The ammonia carbomate is stored within a canister similar to an oil filter. A small amount of diesel fuel is passed through the canister after being heated to just 60 C which causes the ammonia carbomate to sublimate directly into gaseous ammonia. The ammonia and diesel are passed through an oil separator to recover the fuel. The ammonia is injected into the exhaust stream to react with the NOx. No diesel is consumed in the process and the solid system is one third the volume of a urea system. The solid system provides easier handling and packaging and doesn't require the heated storage tanks that urea needs to keep from freezing in cold weather.

FEV is working with supplier Tenneco to market the system and the retrofit market is seen as a prime target for the system. The solid SCR could be adapted to older buses and trucks to bring them up to modern emissions standards.

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