105064
Figure 59
D.P.F. catalyst is made up of an oxidiser catalyst and a
particulate filter.
Oxidiser catalyst (3) is an exhaust gas post-treatment device.
Active substances, contained in the catalyst, oxidise, at 250
°C÷450 °C temperature, carbon oxide (CO) and
hydrocarbons (HC), turning them into carbon dioxide (CO
2
)
and steam (H
2
O).
Catalyst module is made up of a ceramic structure
impregnated with platinum, as platinum is a catalysing
substance in oxidation reactions. Exhaust gasses heat the
catalyst, so triggering the conversion of pollutants into inert
compounds.
Particulate filter (4), connected to the catalyst, has a double
task: retaining particulate particles (PM) depositing between
the pores of the ceramic structure of which the filter is made
up and working as a particulate particles combustion
chamber when the filter is being clogged.
If filter interior is kept at a temperature higher than 530 ºC
and oxygen percentage is higher than 8% (oxygen being
produced by the decomposition of nitrogen oxide NO
2
),
then some combustion reactions, boosted by the catalyst put
before the filter, burn particulate particles (regeneration), so
keeping the filter clean.
On the contrary, if its temperature is lower, the filter is
clogged, with negative effects, on counterpressure, on
exhaust gasses generated by the filter.
In this case, to regenerate the filter, temperature of exhaust
gasses is artificially raised (up to 630 ºC) by fuel post-injection.
A differential pressure sensor (7), connected to D.P.F.
catalyst, as it detects a pressure difference between inlet and
outlet, sends a (feed-back) signal to the central unit to warn
about particulate filter possible clogging.
Description
D.P.F. CATALYST VIEW
1. Exhaust gas inlet- 2. Exhaust gas temperature sensor connection - 3. Catalyst module - 4. Particulate filter -
5. Exhaust gas outlet - 6. Pipes connecting pressure sensor to catalyst - 7. Differential pressure (
∆p) sensor
76
ELECTRIC/ELECTRONIC SYSTEM
D
AILY
E
URO
4
D.P.F. (Diesel Particulate Filter) CATALYST