MQ Power WHISPERWATT DCA150SSJU4F2 Operation Manual page 60

SELECTIVE CATALYTIC REDUCTION (SCR)
Diesel engines can be run with a lean burn air-to-fuel ratio,
to ensure the full combustion of soot and to prevent the
exhaust of unburnt fuel. The excess of air necessarily leads
to generation of nitrogen oxides (NO
pollutants, from the nitrogen in the air. Selective Catalytic
Reduction is used to reduce the amount of NO
into the atmosphere.
Diesel Exhaust Fluid (DEF) from a separate tank is
injected into the exhaust pipeline, where the aqueous urea
vaporizes and decomposes to form ammonia and carbon
dioxide. Within the SCR catalyst, the NO
reduced by the ammonia (NH
nitrogen (N ), which are both harmless. These are then
2
released through the exhaust.
The SCR system creates a certain amount of ammonia
(NH ) that is stored in SCR catalyst. During regeneration
3
operations the increase in temperature at regular intervals
eliminates the stored ammonia.
The process of keeping accurate ammonia storage
amounts is by counting urea injection quantities from the
Dosing Control Unit (DCU).
The DOC/SCR regeneration symbol (Figure 83) will be
displayed on the ECU controller during operation when
either an automatic or forced system purge operation is
in process.
The pre-alarm lamp is only ON during DOC/SCR forced
system purging and OFF during automatic system purging.
ECU
Series 800 Controller
SCR PURGE
Alarm Screen
Option
Acknowledge Change
Figure 83. SCR Regeneration Symbol
PAGE 60 — DCA150SSJU4F2/F3 60 HZ GENERATOR • OPERATION MANUAL — REV. #0 (02/16/22)
), which are harmful
X
released
X
is catalytically
X
) into water (H O) and
3 2
Engine Started
Shutdown
Pre-Alarm
Program
Exit
NOTICE
During urea DOC/SCR system regeneration, white
smoke may be temporarily emitted from the exhaust
tailpipe. This shoud not be considered a failure. In
addition the smell of ammonia during the regeneration
process should not be considered a failure.
If the regeneration process is underway while running
a light load (0–35%), the unit may produce unusual
sounds. This should not be considered a failure or
malfunction.
SYSTEM REGENERATION GUIDELINES
NOTICE
DO NOT perform regeneration in conditions where it
may be unsafe due to high exhaust temperatures.
For safe operation of equipment, the surrounding area and
the prevention of bodily harm, use the guidelines below
when system purging is required:
NOTICE
The area above and around the generator during
the regeneration process should be free of any type
of debris, or flammable or combustible materials, as
temperatures during the purging process can reach
as high 1,022°F (550°C).
„ DO NOT operate the unit in an area with poor ventilation.
„ If operating the engine indoors, install exhaust/ventilation
equipment and ensure that there is sufficient ventilation.
„ If you begin to feel sick, stop the unit immediately and
ventilate the area.
„ Exhaust emissions from the tailpipe have a smell different
from those emitted from engines without urea DOC/SCR
systems due to the exhaust emission reduction functions
of the exhaust system.
MAINTENANCE