How the CRT^® Works

The Eminox CRT^® system uses a patented process that functions on the basis that soot will begin to oxidise in the presence of NO₂ at around 250°C, compared to 600°C with oxygen. This lower temperature is compatible with the typical exhaust temperature of diesel engines.

The CRT^® system is made up of two chambers, a highly active platinum oxidation catalyst followed by an extremely fine ceramic wall-flow filter.

Catalyst

As the dirty exhaust gas enters the first chamber, it hits a diffuser plate which distributes the gas evenly through the catalyst. The platinum oxidation catalyst oxidises the CO and HC into CO₂ and H₂O, virtually eliminating them from the exhaust gas. It also oxidises some of the NO to NO₂. This is the key to the removal of soot collected by the CRT^® filter.

CO + ½O₂ -> CO₂
[HC] + O₂ -> CO₂ + H₂O
NO + ½O₂ -> NO₂

Filter

The wall-flow filter in the second chamber traps the particulate matter in the exhaust gas. This trapped soot is continually oxidised by the NO₂, removing it from the exhaust gas.

[C]+ 2NO₂ -> CO₂ + 2NO

The Eminox CRT^® system gives outstanding performance, eliminating over 90% of all particulate matter, hydrocarbons and carbon monoxide. NO_X reductions, while not guaranteed, are typically in the 5 - 10% range.

Catalysed Filter

In demanding applications a catalytic coating can also be applied to the filter itself. This is called a CCRT^® – Catalysed Continuously Regenerating Trap. This enables the CRT^® to cover a wider range of operating conditions, with lower exhaust temperatures or NO_X:PM ratio.

In the CCRT^®, after the NO₂ has reacted with the soot trapped in the filter, producing NO and CO₂, some of the NO is re-oxidised to NO₂ which then reacts with any soot remaining in the filter.

Soot in the filter reacts with the NO₂:
[C]+ 2NO₂ -> CO₂ + 2NO

Some the NO produced in the reaction is re-oxidised into NO₂:
NO + ½O₂ -> NO₂

The NO₂ reacts with any remaining particulate removing it from the exhaust gas:
[C]+ 2NO₂ -> CO₂ + 2NO