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Filters -> The CRT® system
The CRT® system
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The CRT® system is the most widely
used DPF system in the world and is a patented Johnson
Matthey technology. It comprises an oxidation catalyst
followed by a DPF. The principle of its operation
is shown below.
The oxidation catalyst removes CO and
HC and oxidises some of the NO in the exhaust gasses
to NO2. This NO2 then reacts
with the PM trapped in the filter, producing NO and
CO2 and cleaning the filter.
 CRT®
system performance
This chart shows the emissions reduction achieved
by a CRT® system fitted to a Euro 1
truck engine over the ESC 13-mode cycle. The conversions
shown are typical of the performance of a CRT®
system.
Operating conditions
The conditions normally required for reliable
CRT® performance are:
- a significant proportion (~50%) of the operating
time with an exhaust temperature >250°C,
- a ratio of NOx:PM in the exhaust gases 20:1 or
greater,
- the use of fuel with a maximum sulphur content
of 50ppm.
These conditions are conditional on
each other and exact requirements depend on the system
and the application. If these conditions cannot be
met, a CCRT® system should be considered
instead. Johnson Matthey has many years of experience
of specifying CRT® systems for diverse
applications and is able to advise on which system
is most suited to individual applications.
Typical applications:
Truck and
Bus
Non-road
Mobile Machinery
Cars, Vans and Light
Trucks
Stationary Source
Related products:
CCRT®
systems – a CRT® system with
catalysed filter element to give the same emissions
control performance as a CRT® but in
an even wider range of conditions
SCRT®
systems – a CRT® system working
with SCR to give CO, HC, PM and NOx control
NAC
+ DPF – integrated
diesel particulate filter and NOx adsorber catalyst
systems giving CO, HC, PM and NOx control
EGRT®
system (US retrofit only) – a CRT®
system working with exhaust gas recirculation to give
CO, HC, PM and NOx control
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