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<strong>MAN</strong> B&W 3.03<br />
NO x Reducti<strong>on</strong> by SCR<br />
The NO x in the exhaust gas can be reduced with<br />
primary or sec<strong>on</strong>dary reducti<strong>on</strong> methods. Primary<br />
methods affect the engine combusti<strong>on</strong> process<br />
directly, whereas sec<strong>on</strong>dary methods reduce the<br />
em<str<strong>on</strong>g>is</str<strong>on</strong>g>si<strong>on</strong> level without changing the engine performance<br />
using equipment that does not form<br />
part of the engine itself.<br />
For further informati<strong>on</strong> about em<str<strong>on</strong>g>is</str<strong>on</strong>g>si<strong>on</strong> c<strong>on</strong>trol we<br />
refer to our publicati<strong>on</strong>:<br />
Exhaust Gas Em<str<strong>on</strong>g>is</str<strong>on</strong>g>si<strong>on</strong> C<strong>on</strong>trol Today and Tomorrow<br />
The publicati<strong>on</strong> <str<strong>on</strong>g>is</str<strong>on</strong>g> <str<strong>on</strong>g>available</str<strong>on</strong>g> at www.mandiesel.com<br />
under ‘Quicklinks’ → ‘Technical Papers’<br />
Engine with Selective Catalytic Reducti<strong>on</strong> System<br />
Opti<strong>on</strong>: 4 60 35<br />
If a reducti<strong>on</strong> between 50 and 98% of NO x <str<strong>on</strong>g>is</str<strong>on</strong>g> required,<br />
the Selective Catalytic Reducti<strong>on</strong> (SCR)<br />
system has to be applied by adding amm<strong>on</strong>ia or<br />
urea to the exhaust gas before it enters a catalytic<br />
c<strong>on</strong>verter.<br />
The exhaust gas must be mixed with amm<strong>on</strong>ia before<br />
passing through the catalyst, and in order to<br />
encourage the chemical reacti<strong>on</strong> the temperature<br />
level has to be between 300 and 400 °C. During<br />
th<str<strong>on</strong>g>is</str<strong>on</strong>g> process the NO x <str<strong>on</strong>g>is</str<strong>on</strong>g> reduced to N 2 and water.<br />
<str<strong>on</strong>g>Th<str<strong>on</strong>g>is</str<strong>on</strong>g></str<strong>on</strong>g> means that the SCR unit has to be located<br />
before the turbocharger <strong>on</strong> two�stroke engines<br />
because of their high thermal efficiency and thereby<br />
a relatively low exhaust gas temperature.<br />
The amount of amm<strong>on</strong>ia injected into the exhaust<br />
gas <str<strong>on</strong>g>is</str<strong>on</strong>g> c<strong>on</strong>trolled by a process computer<br />
and <str<strong>on</strong>g>is</str<strong>on</strong>g> based <strong>on</strong> the NO x producti<strong>on</strong> at different<br />
loads measured during the testbed running. Fig.<br />
3.03.0 .<br />
As the amm<strong>on</strong>ia <str<strong>on</strong>g>is</str<strong>on</strong>g> a combustible gas, it <str<strong>on</strong>g>is</str<strong>on</strong>g> supplied<br />
through a double�walled pipe system, with<br />
appropriate venting and fitted with an amm<strong>on</strong>ia<br />
leak detector (Fig. 3.03.0 ) which shows a simplified<br />
system layout of the SCR installati<strong>on</strong>.<br />
<strong>MAN</strong> B&W MC/MC-C/ME/ME-C/ME-GI/ME-B Engines<br />
<strong>MAN</strong> <strong>Diesel</strong><br />
Page of 2<br />
198 58 94-7.1
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