Project OptiMon: Implementation of the optimized ammonia supply for SCR catalysts in the exhaust gas of non-road diesel engines (Duration: 12/2018 - 04/2020)




The SCR process (Selective Catalytic Reduction) has prevailed as a method to reduce NOx emissions from combustion engines and comply with emission limits. In this process, nitrogen oxides (NOx) are catalytically converted into nitrogen and water using ammonia (NH3). The ammonia is chemically stored in urea solution (AdBlue). This solution is carried along on-board and is injected into the exhaust gas stream ahead of the SCR catalyst. The release of ammonia from the solution is a multi-stage process consisting essentially of the evaporation of the water and the thermal decomposition of the urea to ammonia and carbon dioxide.

Although the SCR technology is already in series application, it is still in the focus of scientific and technical investigations. A reason for this is the insufficient decomposition of urea at low exhaust gas temperatures, which can lead to the formation of undesirable by-products. As a result, deposits can occur in the exhaust gas system as well as on the SCR catalyst, which compromise the operation of the exhaust gas treatment. Deposits reduce the accessible volume and catalyst surface area, which causes a decline of the SCR reaction as well as a disruption of the system pressure.

This issue was the motivation for the companies Autotechnik GmbH Johanngeorgenstadt and Argomotive GmbH Dresden as well as for the TU Bergakademie Freiberg to carry out a joint project with the title "Implementation of optimized ammonia supply for SCR catalysts in the exhaust gas of non-road diesel engines" (OptiMon). The project is funded by the European Regional Development Fund and is carried out over a period of 18 months.

In previous cooperations (SAB project OptiNOx) of the project partners various fluid dynamic and chemical approaches have already been investigated. As a result, strategies which have the potential to achieve the set objectives were developed. These include the modified design of the exhaust gas system including AdBlue injection nozzle (e.g. installation location and angle, flow control of the exhaust gas) and the coating of relevant components with a catalytically active component. The measures have been successfully tested under laboratory conditions.

The scientific and technical objective of the project is to apply the developed fluid dynamic and chemical solutions in practice. For this purpose, it is intended to implement the optimized ammonia supply system in a variable prototype and to design, construct and test prototypes for defined applications. The designated area of application is the non-road sector. The optimized process is intended to enable the reliable dosing of AdBlue already above 180°C. However, according to the current state of the art, AdBlue can only be used at temperatures above 200 to 230°C.