Background information

In the course of constantly increasing global industrialisation and the related increase in emissions generated in combustion processes, it is necessary to tighten the prescribed limit values continuously for health and environmental reasons. As a result, huge efforts are made to continue reducing the emission of exhaust gas pollutants.

Pollutants from engine combustion can both be prevented using suitable measures in the engine to prevent their generation or can be minimised outside of the engine through the aftertreatment of the exhaust gases in catalytic converters or filters in the exhaust gas system.

The extensive group of the most varied hydrocarbons (including formaldehyde) and carbon monoxide can be oxidised to form harmless gases using oxidation catalysts if there is enough residual oxygen in the exhaust. The most varied catalysts and coatings are used depending on the fuel and the combustion procedure.

Soot from diesel engine combustion and non-combustible components of the exhaust gas, such as ash, wear debris, etc., can be filtered out of the exhaust gas using suitable media. The combustible main component of the soot particulate mass "stored temporarily" in the particulate filter can be continually passively oxidised with the help of the CRT effect using nitrogen dioxide or can be combusted thermally with oxygen by adding additives or using an active regeneration aid as of a certain temperature.

Exomission’s portfolio also includes another technology to reduce soot: the patented Fuel Water Emulsion (FWE). This makes soot reductions of up to 90% possible when liquid fuels such as diesel or vegetable oils are used. This prevents soot production in the engine, and this without increasing fuel consumption and with virtually no maintenance required.

Nitrogen oxides or nitrogen-oxygen compounds, especially NO and NO2 cannot be converted into harmless materials by simple oxidation, but instead can only be converted back to the required elemental nitrogen by releasing oxygen.

Petrol engines can be operated oscillating around the stoichiometric fuel-air mixture (lambda = 1), so that quickly changing oxygen surplus (lean) can be set for the oxidation of CO and HC on the one hand, and lack of air (rich) can be set for the reduction of nitrogen oxides on the other hand. This is referred to as a lambda-controlled system. If a catalytic converter system is located in the exhaust gas system, this is called a three-way catalytic converter, as the three main pollutant groups CO, HC and NOx are reduced.

Exhaust gases from engines that operate in accordance with the diesel engine principle, however, always have a systemic large amount of excess oxygen, meaning that the three-way catalyst principle for reducing the nitrogen oxides described above cannot be used.

The NOx storage catalyst has limited effectiveness with diesel engines (and thus a limited application). Here, nitrogen oxides are temporarily stored in a special catalyst and reduced using brief rich phases at short intervals. The effectiveness and durability are, however, limited; the increased fuel consumption is not insignificant.

Nitrogen oxide reduction using selective catalytic reduction (SCR) has been used successfully for industrial applications for decades and also in mobile applications for a few years now.

Nitrogen oxides can also be reduced by about up to 45% using Fuel Water Emulsion (FWE) by lowering the combustion temperature in the combustion chamber. FWE is also the only technology that can simultaneously reduce soot and nitrogen oxides significantly.

Only in very few applications is it sufficient to implement just one technology to achieve the legal requirements. It is often necessary to combine various technologies. All of the Exomission technologies that have been described can be combined when designed accordingly. 

For example, combining SCR and emulsion technology makes it possible to halve the consumption of AdBlue® – a huge cost-saving effect!

Depending on the conditions, we would be happy to draw up a system design customised to your individual requirements.

 

We look forward to hearing from you.

 

 
                          

 

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