Man L23/30DF, Руководство по проекту

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Compressed air reservoir module
(MOD-085) and soot blowing system
(MOD-086)
The compressed air required for the operation of
the SCR system is provided by the compressed air
module. It receives its compressed air via the ship´s
compressed air grid. For the quality requirements
read section Specification of compressed air. The
main supply line feeds the compressed air reservoir
module, where a compressed air tank is installed.
This high-pressure tank is a reservoir with enough
capacity to ensure the supply of the dosing unit and
the air consumption for the periodically cleaning of
the catalysts´ surface, by avoiding fluctuations in the
soot blowing system. In case of black out the vol-
ume of the tank will be used for flushing the urea
line and nozzle.
The module has to be positioned close to the reac-
tor and the dosing unit. The maximum length of the
compressed air line to the soot blowing system is
10 m.
The soot blower valves are positioned upstream
each catalyst layer in order to clean the complete
surface of the catalyst elements by periodical air
flushing. The soot blowing always has to be in oper-
ation while engine running.
Urea pump modul (MOD-084)
The urea pump module boosts urea to the dosing
unit and maintains an adequate pressure in the urea
lines. The complete module is mounted in a stand-
ard cabinet for wall fastening. Upstream of the sup-
ply pump, a filter is installed for protection of solid
pollutants. Downstream, the module is equipped
with a return line to the urea storage tank with a
pressure relief valve to ensure the required urea
flow.
The urea pump module has to be positioned on a
level below the minimum urea level of the urea stor-
age tank. The pump accepts a maximum pressure
loss of 2 bar. One urea pump module can supply
up to four SCR systems.
Urea quality according section Specification of
urea solution is required. For urea consumption
calculation for Tier III read section Urea con-
sumption for emission standard IMO Tier III.
Dosing unit (MOD-082)
The dosing unit controls the flow of urea to the
injection nozzle based on the operation of the
engine. Furthermore it regulates the compressed air
flow to the injector.
In order to avoid clogging due to the evaporation of
urea in the urea pipe and in the nozzle, a line
between compressed air line and urea line is instal-
led. An installed solenoid valve will open to flush
and cool the urea line and nozzle with compressed
air before and after injecting urea into the exhaust
gas.
The dosing unit has to be installed close to the urea
injection lance and mixing unit (maximum pipe
length 5 m).
Urea injection lance and mixing unit
(MOD-087)
The urea solution will be injected into the exhaust
gas using a two-phase nozzle. The urea will be
atomised with compressed air. The evaporation of
the urea occurs immediately when the urea solution
gets in contact with the hot exhaust gas.
The urea injection and the mixing unit have to be
positioned according to MAN Diesel & Turbo
requirements. In general, the mixing section is
between 3.0 – 4.5 m long and of DN 500 to DN
2,300. The mixing duct is a straight pipe upstream
of the reactor. The exact length has to be calcula-
ted. Additional, it has to be considered that an inlet
zone upstream the reactor of 0.5 x diameter of the
exhaust gas pipe has to be foreseen.
SCR reactor (R-001)
Each engine is equipped with its own SCR reactor
and it is fitted in the exhaust gas piping without a
by-pass. The SCR reactor housing is a steel struc-
ture with an inlet cone. The reactor configuration is
MAN Diesel & Turbo
3700467-8.1
Page 13 (17)
SCR (Selective Catalytic Reduction)
B1600 0
V28/32S, L28/32S, L28/32H, L27/38S, L27/38, L23/30S, L23/30H, L21/31S,
L21/31, L16/24S, L16/24