Selective Catalytic Reduction

Abbreviation: SCR

Exhaust after-treatment that injects urea into hot exhaust gas, converting NOx to N2 and water on a vanadium-titanium catalyst.

In practice

Operated continuously on Tier-III engines in NOx ECA waters. The duty engineer monitors urea injection rate, exhaust temperature window (>270 °C), and NH3 slip. Catalyst poisoning by sulphur is the major maintenance cost; some operators bypass SCR outside ECAs.

Regulatory detail & full definition

Required on most newbuilds operating in NOx ECAs to meet IMO Tier III (3.4 g/kWh below 130 rpm). Operating window is 250-450 deg C — auxiliary boiler often used to maintain temperature at low load. Urea is supplied as 32.5% AdBlue solution; consumption ~3% of fuel mass.

Authoritative source: MARPOL Annex VI (Air pollution) ↗

MARPOL Annex VI

Source: MARPOL Annex VI Reg. 13 (NOx); IMO MEPC.291(71) (NOx Technical Code)

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Selective Catalytic Reduction

In practice

Related

Selective Catalytic Reduction

In practice

Related