Control of Emission from Ships Exhaust Smoke

This
article discusses about as how to control the emissions from the ships, thus
reducing the air pollution caused by them. Annex 6 of MARPOL is all about the
emissions that are getting out from the ship, particularly Nox and Sox. Let’s
read this piece of information for further knowledge. 

Sources
of Air Pollution from Ship

1        
Ozone depleting substances like halogens or Chloro-Fluro-Carbons
(cfc).
2       
Nitrogen oxides (Nox) found in emission from
diesel engines
3       
Sulphur dioxide emissions (sox) due to
combustion of High Sulphur Fuels.
4       
Volatile organic compounds (Voc) that are released
by certain cargoes carried in oil tankers, chemical tankers or gas tankers.
5       
Incineration of waste material.
6       
Ozone Depleting Substances
7       
Use of ozone depleting substance is prohibited
in new installations on ships.
8      
Use of halogens for fire fighting and CFC in
refrigeration system may be permitted on existing ships.
9       
Use of Hydro-chloral-fluro-carbons (HCFC) in
equipment installed before 1st January 2020 may continue in service.

What is
Nitrogen Oxide (Nox)

Control
of NOx is applicable to Diesel engines of more than 130 kW installed on ships
constructed on or before 1st January 2000. It is not applicable to equipments
used solely in emergency, e.g., emergency generator, emergency fire pump or
life boat engine. Controls are applicable if an engine undergoes a major
conversion after 1st January 2000.
Emission
is calculated as the total weighted emission of Nox, based on the engine speed
and power.  It should be within following
limits.
17.0 g
/ kWh, if the engine speed (n) is less than 130 r.p.m.
45.0 x
n0.2 g / kWh, if the speed  (n) is
between 130 and 2000 r.p.m.
9.8 g /
kWh, if the speed (n) is 2000 Revolution per minute (RPM) or more.
Operation
of engines with exhaust gas cleaning system to reduce on board emission to
above limits is permitted. Emission monitoring and recording devices be fitted.

What is
SOx Emission?

SOx
emission is controlled by limiting the sulphur content in the residual fuels that
are used on ships to 4.5%m/m. When Sulphur content residual fuel supplied to
all ships, the levels should be monitored. Emission control area include the
Baltic Sea, North Sea such other area which may be designated by IMO,
subsequent to requests from the contracting state administration, supported by
relevant studies and data.
Marine Air Pollution Prevention

Ships
operating in Sox emission control areas should not use fuel oil with sulphur
contents exceeding 1.5% m/m. Alternately, exhaust gas cleaning system as per
IMO guide lines may be installed which reduces SOx emission from main &
auxiliary boiler to 6.0 g SOx / kWh or less.If the ship uses two grades of fuel
oils, change over to low sulphur fuel oil should take place well before entry
in to the control area.
Fuel
oil delivery notes issued by the suppliers shall be preserved on ships for duration
of at least 3 years. Sealed fuel oil samples, signed by the supplier and ship’s
officer shall be retained till the fuel is subsequently consumed or 12 months,
whichever is more in this case. The delivery note shall contain information in
the product name, quality, density at 150C and sulphur content.
Fuel oil should be free from inorganic acids. It should not include added substances
or chemical waste, which will or may affect safety of the ship, working of
machinery, well being of personnel or cause additional air pollution. Government
or administration shall monitor and manage the fuel oil supplier in their state.

Emission
OF VOCs

This is
regulated by port administration. Size of the tankers and types of cargoes
shall be specified in the notifications issued for this purpose. Control system
should be provided by the port or terminal. Tankers ships which are required to
use such control systems, should provide vapour collection system and use the
same during loading of cargoes.
This
regulation applies to all carriers when the loading and containment system
allow safe retention of non-methane VOCs on board or their safe return ashore.

Incinerator
Emission

Shipboard incinerator should be approved by the administration, and meet IOM standards.
The
incinerator shall operate within following limits.
Oxygen
in furnace or combustion chamber is to be 6 – 12 %
Carbon
monoxide in flue gases   – 200 Mg / MJ
Soot
number which is Bacharach 3 or Ringelman 1 – (20% Opacity)
Higher
number accepted during short starting up periods. Combustion chamber flue gas
outlet temperature 850-1200 degree Celsius.

Onboard
incineration of these substances is prohibited

  • Residues
    of cargoes covered under annexes I, II and III and related contaminated
    packaging material.
  • Polyclorinated
    biphenyls (PCV).
  • Garbage
    that are containing more than traces of heavy metals in them.
  • Those Refined
    petroleum products which are containing halogen compounds.
  • Incineration
    of sewage sludge and oil sludge in main or auxiliary boilers is permitted
    except when the ship is inside ports and harbors.

Incinerator
should be operated by trained personnel. Flue gas temperature should be monitored at
all times. Waste
should not be fed in to a continuous feed incinerator when the temperature is
below 850 degree Celsius. For batch loading of incinerators, the combustion
chamber temperature should reach 600 degree Celsius within five minutes after start up.

Contracting
government should provide reception facilities in their ports for Ozone
depleting substances during ship repairs and ship breaking and exhaust gas
cleaning residues, which may affect marine environment. This was all about Marpol Annex 6.

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