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EXHAUST GAS AFTERTREATMENT (ALL UNITS)
To meet the demands of Stage IIIB / Tier 4 Interim
Emission Legislation, the engine is equipped with an
exhaust aftertreatment module (EAM), consisting of
an exhaust gas recirculation system and a particulate
filter. The exhaust gas is fully automatically cleaned.
The process is monitored by the machine controller.
Step 1 Exhaust Gas Recirculation
With Exhaust Gas Recirculation (EGR), part of the
exhaust gases are cooled and then injected back into
the engine cylinders to reduce NOx.
Exhaust gas is cooled to allow the introduction of a
greater mass of recirculated gas.
The outcome is a lower peak combustion
temperature.
Step 2 Diesel Particulate Filter + Diesel
Oxidation Catalyst
To remove excess particulate matter from the exhaust
gas, a Diesel Particulate Filter (DPF) is used. This
system consists of a Diesel Oxidation Catalyst (DOC)
and a filter module. The DOC reduces CO, HC and
NO through oxidation. It also produces NO
2
to
regenerate the DPF. The filter system removes 99%
of particulate matter.
Step 3 Active regeneration
Particulate matter left in the filter system is burned in
a process called regeneration. Extending the lifetime
of a filter, it converts particulate matter into CO
2
and
ash. Atlas Copco engines use high temperature
regeneration that includes a fuel burner in the exhaust
stream that intermittently raises the temperature
above 600º C / 1100° F.
A separate High Pressure Fuel Pump (HPFP) supplies
fuel to the burner in the active regeneration system.
Active regeneration decreases in the higher load
cycles of the compressor.
Step 4 Ash removal
Additives in lube oil that do not combust during
regeneration, turn into ash. This reduces filter
volume, oxidation efficiency and backpressure.
Ash must be removed mechanically, according a
service interval, either by washing or blowing it out.
This service interval can be increased depending on
duty cycle.
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