To reduce NO_x emissions from combustion engines and comply with emission limits, the so-called SCR process (SCR, selective catalytic reduction) has become established. In this process, the nitrogen oxides (NO_x) are converted to nitrogen and water using ammonia (NH₃) on catalytic converters. The ammonia is used in chemically bound form as a urea solution (AdBlue). This solution is stored on-board and injected into the exhaust gas flow upstream of the SCR catalytic converter. The release of ammonia from this solution is a multi-stage process that essentially consists of the evaporation of the water and the thermal decomposition of the urea into ammonia and carbon dioxide.

Although SCR technology is already being used in series production, it is still the focus of scientific and technical investigations. One of the reasons for this is the problem of insufficient decomposition of the urea at low exhaust gas temperatures, which can lead to the formation of undesirable, sometimes ceramic-like by-products. As a result, deposits can form in the exhaust tract and on the SCR catalytic converter, which significantly impair the functioning of the exhaust gas aftertreatment system. Deposits cause a reduction in the volume to be flowed through or a smaller catalytic converter surface area that can be flowed through, which both reduces the SCR reaction and severely disrupts the system pressure.

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

In previous collaborations (OptiNO_x project ) between the partners, various fluidic and chemical solutions have already been investigated. As a result, strategies have been developed that have the potential to achieve the set objective. These include the modified design of the exhaust tract including the AdBlue injection nozzle (e.g. installation location and angle, flow routing 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 fluidic and chemical solutions in practice. To this end, it is intended to implement the optimized ammonia supply for SCR catalytic converters in the form of an appropriately designed, prototypical variable system for defined applications and to design, build and test prototypes for defined applications. The intended area of application is the non-road sector. The optimized process should enable the reliable dosing of AdBlue above 180°C. In contrast, AdBlue can only be used at temperatures above 200 to 230°C according to the current state of the art.