This document discusses NOx and SOx emissions from ships and their regulation. It provides background on the major air pollutants from ships, NOx and SOx formation chemistry, hazards they cause, and MARPOL legislation which sets emission standards in three tiers and establishes emission control areas. It then describes technologies for reducing SOx emissions including lowering sulfur fuel content, removing sulfur before or during combustion, and flue gas desulfurization. Operational concerns with low-sulfur fuels are also discussed.

1. NOX AND SOX EMISSION
CONTROL

2. ABSTRACT
 Ship’s SOX emissions forms 60% of total SOX
Emissions.
 We are polluting our environment by our
choice of fuel.
 Emission control in the angle of MARPOL
and the technologies for reduction are taken
into account.

3. POLLUTANTS
 Air pollutants can also be of primary or secondary
nature.
 Primary is emitted directly to atmosphere.
 Secondary is formed by reactions between primary
pollutants.
 The major pollutants are
1. Oxides of nitrogen
2. Oxides of sulphur
3. Particulate matter

4. CHEMISTRY OF FORMATION
 N2+O2 2NO
 2NO+O2 2NO2
 S+O2 SO2
 SO2+NO2 NO+SO3
 2NO+O2 2NO2
 NO2+SUNLIGHT NO+O
 O+O2 O3

5. HAZARDS
 Corrosion
 Climate change
 Photochemical smog
 SO2 irritates the eyes, nose and lungs
 SO2 causes acid rain
 NO2 causes pulmonary edema

6. MARPOL LEGISLATION
 Annex VI- Regulations for the prevention of
air pollution from ships
 Came to force on 19th May 2005
 For every ship with 400 gross tonnage and
above and for fixed and floating drilling rig
 Certificate- “International air pollution
prevention certificate”
 Validity- period not exceeding five years

7. MAJOR REGULATIONS
 There are 19 Regulations but the following
Regulations impact Vessel operation :
 Regulation 12 – Ozone Depleting Substances
 Regulation 13 – NOx emissions
 Regulation 14 – Sulphur Oxide emissions
 Regulation 15 – VOC emissions
 Regulation 16 – Shipboard Incinerators
 Regulation 18 – Fuel Oil Quality control

8.  Emission standards are referred to a Tier I,
II,III
 Tier I came into force on 19th May 2005.
 The revised Annex VI enters into force on 1st
July 2010.
 Tier II,III are more stringent than Tier I .
 Tier II standards are expected to be met by
combustion process optimization.
 Tier III standards are expected to require
dedicated NOx emission control technologies.

9. REGULATION 13
 Deals with control of NOX emissions.
 All engines with power more than 130KW and
built on or after 1/1/2000
 Doesn’t apply to engines used in emergency.
 Emissions must be limited to,
 17.0 g/kWh when n <130 rpm;
 45.0 x n-0.2 g/kWh when n is 130 or more but
less than 2000 rpm;
 9.8 g/kWh when n is 2000 rpm or more

12. SOX CONTROL
 Sulphur content of fuel shall not exceed 4.5%.
 SOX emission ECA include Baltic and North sea
area.
 Sulphur content shall not exceed 1.5% in ECA.
 Total emission must be less than 6 g SOX/kWh
in ECA

15. FUEL OIL QUALITY
 Fuel oil shall be free from inorganic acid.
 Bunker delivery note must be maintained.
 Bunker delivery note must kept for 3 years.
 Fuel oil sulphur content must never exceed
4.5%.
 Parties of 1997 protocol must maintain a
register of local suppliers of fuel oil.

16. EMISSION MEASUREMENT
 For Attaining Interim Certificate of
Compliance.
 Engines combined into engine groups by
manufacturer
 Engine from this group selected for emission
testing

17. EXHAUST GAS MONITORING
TECHNIQUES
Exhaust Gas
Monitoring
Equipments
EExxttrraaccttiivvee
SSyysstteemmss NNoonn--EExxttrraaccttiivvee
SSyysstteemmss
UUVV AAnnaallyysseerrss Chemi-luminescence
IInnffrraarreedd
AAnnaallyysseerrss
UUllttrraa--VViioolleett
AAnnaallyysseerrss

18. Extractive Systems
 Permanently installed
 Requires additional equipment to process the
exhaust gas sample.
 Advantages
 Able to be remotely located in a controlled environment
 Easier to operate, calibrate and maintain.
 Can be set up to monitor exhaust gas emissions from more
than one engine.
 Disadvantage
 High Cost

19. NON-EXTRACTIVE SYSTEMS
 Predominately use infrared or ultra-violet
techniques.
 Measure the exhaust gas emissions without
extracting the exhaust gas from the uptake
system.
 Advantages
 More portable
 Provides more rapid responses.
 Disadvantages
 Difficult to calibrate.

20. CHEMILUMINESCENCE
 HCD (Heated Chemiluminescence Detector).
 Accepted standard for laboratory and test cell
measurement of NOx.
 Was the only available NOx detector available
during the development of the IMO Technical
code.
 Needs to have a continuous supply of clean
dry air else damage to the analyser
components will result.
 NO determination with detection limits down
to 1 ppb.

21. ULTRA-VIOLET ANALYSERS
 Particularly useful for measuring SO2 .
 Used in extractive and non-extractive systems.
 Not suitable for the measurement of NOx.

22. REDUCING SOX EMISSIONS
 2 Possibilities :-
 Burning fuels with lower sulphur content
 Treating the engine exhaust gases
 At Present limits on sulphur content of marine
fuel
 Globally – 4.5%
 SECA – 1% from 1st july,2010
 SOX emission control areas (SECA)
 North Sea, English Channel and the Baltic Sea.

24. TECHNIQUES FOR
REDUCING SOX EMISSIONS
 3 possibilities to reduce SO2 emissions from
combustion processes:
1) REMOVAL OF SULPHUR BEFORE COMBUSTION
2) REMOVAL OF SULPHUR DURING COMBUSTION
3) REMOVAL OF SOX AFTER COMBUSTION ( I.E.
FLUE GAS DESULPHURISATION )

25. REMOVAL OF SULPHUR
BEFORE COMBUSTION
 Process used : Hydrotreating or Hydrodesulphurisation
 Treatment of the oil with hydrogen gas obtained e.g. during
catalytic reforming.
 Sulphur compounds are reduced by conversion to hydrogen
sulphide (H2S) in the presence of a catalyst.
 H2S washed from the product gas stream by an amine wash
 H2S is recovered in highly concentrated form
 Converted to elemental sulphur via the Claus-Process
 Feedstock is mixed with hydrogen-rich make-up and recycled
gas and reacted at temperatures of 300 - 380 °C.

26.  Removal of sulphur from heavier oils such as marine fuel oil
often requires pressures of up to 200 bar.
 Catalysts employed : cobalt, molybdenum or nickel finely
distributed on alumina extrudates.

27. CLAUS PROCESS
 Most significant Gas desulphurizing process
 Recovers elemental sulphur from gaseous
hydrogen sulphide
 The overall main reaction equation is:
2 H2S + O2 → S2 + 2 H2O

29. REMOVAL OF SULPHUR
DURING COMBUSTION
 Experimental Stage
 The combustible compound is mixed with an
admixture of water soluble and water insoluble
sulphur sorbent.
 Such admixtures, remarkably, produces a
reduction in the SOX level far greater than
would be expected based on the activity of
each sorbent alone.

30. REMOVAL OF SOX AFTER
COMBUSTION
TTHHEE
SSEEAAWWAATTEERR
SSCCRRUUBBBBEERR
SSPPRRAAYY
DDRRYY
SSYYSSTTEEMM
WWEELLLLMMAANN--LLOORRDD
PPRROOCCEESSSS
LLIIMMEESSTTOONNEE
//GGYYPPSSUUMM
SSYYSSTTEEMM
FFLLUUEE
GGAASS
DDEESSUULLPPHHUURRIISSAATTIIOONN
((FFGGDD))

31. LIMESTONE/GYPSUM
SYSTEM
 Most widely used process
 Principle
 Suspension of crushed limestone in water is
sprayed into the flue gases.
 SO2 reacts with calcium ions to form calcium
sulphite slurry
 Aeration of the slurry with compressed air
oxidizes calcium sulphite to calcium sulphate
 After removal of the water, the calcium
sulphate can be disposed off

33.  Advantage :
 SO2 reduction around 90 %
 Disadvantages :
 limestone has to be stored onboard
 large quantities of gypsum waste is produced

34. SPRAY DRY SYSTEM
 A slurry of slaked lime is used as an alkaline
sorbent
 The slurry is injected into the flue gases in a
fine spray.
 The flue gases are simultaneously cooled by
the evaporation of water
 The SO2 present reacts with the drying sorbent
to form a solid reaction product, with no
wastewater.

35. WELLMAN-LORD PROCESS
 Hot flue gases are passed through a pre-scrubber
 Ash, hydrogen chloride, hydrogen fluoride and SO3 are
removed.
 the gases are then cooled and fed into an absorption tower
 SO2 reacts with a saturated sodium sulphite solution to form
sodium bisulphite.
 The sodium bisulphate is regenerated after a drying step to
sodium sulphite again.
 The released and clean SO2 - may then be liquefied or
converted to elemental sulphur or sulphuric acid.
 The sorbent is regenerated during the combustion process and
is continuously recycled, but the products (sulphur
compounds) have to be stored.

36. TTHHEE SSEEAAWWAATTEERR SCRUBBER
 Krystallon Sea-Water Scrubber
 Removes 90-95 % of SO2
 In addition removes 80 % of the particulates
and 10-20% of hydrocarbons.
 Advantages
♦ no limestone has to be stored on board,
♦ no waste (gypsum) is produced, which has to
be deposited on land,
♦ the seawater already contains substantial
amounts of sulphate and nitrate
♦reduction of engine noise and a reduction of
the diesel smell..

37. FFeeaattuurreess
 Uses Cyclone Technology
 The system needs only a little extra space
 Aeration of the effluent is necessary
 high degree of recirculation

38. WWoorrkkiinngg
 Water in contact with hot exhaust gas
 Exhaust gas is channelled through a concentric
duct into a shallow water tank.
 Mixing baffles break up large gas flow into
smaller bubbles
 SOx in exhaust gas is dissolves in seawater
 Larger particles (greater than 2.5 micron)
captured in the water.
 Fine particles (smaller than 2.5 micron) may
pass through without capture.

39.  Pumped through a set of large cyclones
 Designed to separate some of the heavy
particles, as well as light particles in a two-stage
system.
 Fed to a settling tank for collection of soot and
oil.
 Runs with no ongoing maintenance
 Cleaned recirculated water is maintained at
extremely low concentrations of hydrocarbons,
making it safe for discharge to sea.

41. OPERATIONAL CONCERNS
AROUND THE CHANGE TO
LOW SULPHUR FUELS
 REDUCED FUEL VISCOSITY
 FUEL ACIDITY
 IGNITION AND COMBUSTION QUALITY
 FUEL LUBRICITY

42. REDUCED FUEL VISCOSITY
 MGO and MDO fuels have a lower inherent
viscosity than heavy fuel oil which can :
 Effect Diesel Engines
 Effect Steam Boilers

43. Effect On Diesel Engines
 Changes in fuel atomisation
 Adversely affects power output and engine
starting performance.
 Solution Recommended : Use fuel coolers to
control fuel viscosity

44. Effect On Steam Boilers
 Affects fuel flow setting (for a given pressure)
at the burners
 Can lead to “Over Firing”
 Increased risk of flame failures and flame
impingement on boiler tube plates.
 Solution Recommended :
 Change the nozzle
 Or the air/fuel ratio settings

45. FFUUEELL AACCIIDDIITTYY
 Does not present a problem for steam boilers
 But has a significant effect on diesel engines
 Engine lube oils are formulated with alkaline
additives to neutralise the acidic, sulphur, by-products
of combustion.
 IF amount of sulphur in the fuel is reduced, THE
amount of alkaline additives should be reduced.
 Too much alkalinity causes build-up of deposits that
will affect the lubricating film
 Solution Recommended : Oil with a lower Base
Number (BN).

46. IIGGNNIITTIIOONN AANNDD
CCOOMMBBUUSSTTIIOONN QQUUAALLIITTYY
 Effect On Diesel Engines
 Effect On Steam Boilers

47. Effect On Diesel Engines
 Poor combustion and ignition may lead to
increased fouling of the engine
 Fouling is so excessive that moving parts such
as exhaust valves are inhibited by the soot,
leading to broken/bent valves
 Excessive fouling of the scavenge air receiver
combined with late ignition or prolonged
combustion may lead to a buildup of soot
deposit and the risk of fire.

48. Effect On Steam Boilers
 Leads to starting failures and more frequent
flame failures
 May lead to increased soot formation and
consequent fouling of the boiler and exhaust
system.
 Solution Recomended: Follow detailed advice
given by manufactures on procedures to follow
when switching fuel qualities.

49. FFUUEELL LLUUBBRRIICCIITTYY
 Ultra Low Sulphur Diesel (ULSD) contains
<15ppm sulphur.
 Inherent lubricity of such diesel is reduced
which in turn increases wear on fuel pumps
and injectors.
 Solution : Lubricity additives are commonly
added at source to such fuels to reduce these
problems

50. EENNGGIINNEE EEXXHHAAUUSSTT DDEEPPEENNDDSS
UUPPOONN
 ENGINE TYPE ( i.e LOW,MEDIUM AND
HIGH SPEED)
 ENGINE SETTING ( i.e LOAD,SPEED AND
FUEL INJECTION TIMING)
 FUEL USED

51. FFAACCTTOORRSS AAFFFFEECCTTIINNGG
NNOOxx FFOORRMMAATTIIOONNSS
 SPEED OF ENGINE
 MAXIMUM TEMPERATURE
INSIDE CYLINDER
 COMPRESSION RATIO/PEAK
PRESSURE
 AMOUNT OF SCAVENGE AIR

52. NNOOxx RREEDDUUCCTTIIOONN
TTEECCHHNNIIQQUUEESS
PRE-TREATMENT
INTERNAL
MEASURE
(PRIMARY
METHODS)
AFTER
TREATMENT
(SECONDARY
METHODS)

53. NNOOxx RREEDDUUCCTTIIOONN
TTEECCHHNNIIQQUUEESS
PRE-TREATMENT
INTERNAL
MEASURE
(PRIMARY
METHODS)
AFTER
TREATMENT
(SECONDARY
METHODS)

54. AALLTTEERRNNAATTIIVVEE FFUUEELLSS
 METHANOL
 LIQUIFIED PETROLEUM GAS

55. MMEETTHHAANNOOLL
 50% REDUCTION
 NO SULPHUR
 BAD IGNITION QUALITY
 CORROSIVE
 EXPENSIVE FUEL

56. LLIIQQUUIIFFIIEEDD PPEETTRROOLLEEUUMM GGAASS
 BUTANE(C4H10)+PROPANE(C3H8)
 LOW ENERGY DENSITY SO MORE FUEL
CONSUMPTION
 NON-CORROSIVE
 NON-TOXIC

57. WWAATTEERR AADDDDIITTIIOONN TTOO FFUUEELL
 UNDER RESEARCH WITH 30% OF
WATER IN FUEL
 30% REDUCTION IN NOx EMISSION
 EFFECT ON ENGINE COMPONENTS IS
NOT KNOWN
 DECREASE MAXIMUM TEMPERATURE
INSIDE CYLINDER
 HIGH SPECIFIC HEAT

58. NNOOxx RREEDDUUCCTTIIOONN
TTEECCHHNNIIQQUUEESS
PRE-TREATMENT
INTERNAL
MEASURE
(PRIMARY
METHODS)
AFTER
TREATMENT
(SECONDARY
METHODS)

59. MMOODDIIFFIICCAATTIIOONNSS IINN
CCOOMMBBUUSSTTIIOONN PPRROOCCEESSSS
 INJECTION TIMING RETARDATION
 INCREASE IN INJECTION PRESSURE
 OPTIMIZATION OF INDUCTION SWIRL
 MODIFICATION OF INJECTOR
SPECIFICATION
 CHANGE IN NUMBER OF INJECTORS

60. IINNJJEECCTTIIOONN TTIIMMIINNGG
RREETTAARRDDAATTIIOONN
 REDUCE MAXIMUM COMBUSTION
TEMPERATURE & PRESSURE
 REDUCTION UPTO 30% OF NOx
EMISSION
 INCREASE IN SFC BY 5%
 MORE EFFECTIVE FOR MEDIUM/HIGH
SPEED ENGINES

61. IINNCCRREEAASSEE IINN IINNJJEECCTTIIOONN
PPRREESSSSUURREE
 COMBINED WITH OTHER TECHNIQUES
 PROVIDES BETTER ATOMIZATION

62. OOPPTTIIMMIIZZAATTIIOONN OOFF
IINNDDUUCCTTIIOONN SSWWIIRRLL
 COMBINED WITH OTHER NOx
REDUCTION TECHNIQUES
 HELPS IN GOOD COMBUSTION
 NO ADDITIONAL COST

63. IINNJJEECCTTOORR SSPPEECCIIFFIICCAATTIIOONNSS
 INJECTION PRESSURE
 NUMBER AND ANGLE OF HOLES
 SIZE OF HOLES

64. CCHHAANNGGEE IINN NNUUMMBBEERR OOFF
IINNJJEECCTTOORR
 COMBUSTION PROCESS CAN BE
CONTROLLED BETTER
 REDUCE MAXIMUM COMBUSTION
TEMPERATURE
 ADDITIONAL COST OF FUEL INJECTOR
AND PIPING
 INCREASE IN MAINTENANCE COST
 30% REDUCTION IS ACHIEVABLE

65. SSCCAAVVEENNGGEE//CCHHAARRGGEE AAIIRR
CCOOOOLLIINNGG
 14% REDUCTION IS POSSIBLE BY
LOWERING CHARGE AIR TEMP. FROM
40oC to 25oC
 REDUCE COMBUSTION TEMPERATURE
 SUITABLE FOR MEDIUM AND HIGH
SPEED ENGINES
 COOLING AIR TOO MUCH COULD LEND
TO COMBUSTION PROBLEMS

66. WWAATTEERR IINNJJEECCTTIIOONN
 DURING COMBUSTION THROUGH
SPECIAL INJECTOR
 REDUCES THE BULK TEMPERATURE OF
COMBUSTION
 40% REDUCTION IN NOx EMISSION IS
ACHIEVED

68. WWAATTEERR IINNJJEECCTTIIOONN
LLIIMMIITTAATTIIOONNSS
 NEED OF SEPARATE PUMP FOR FUEL
AND WATER
 COST FACTOR
 CORROSION

69. NNOOxx RREEDDUUCCTTIIOONN
TTEECCHHNNIIQQUUEESS
PRE-TREATMENT
INTERNAL
MEASURE
(PRIMARY
METHODS)
AFTER
TREATMENT
(SECONDARY
METHODS)

70. WWHHAATT IISS SSCCRR??
SELECTIVE CATALYST REDUCTION IS
THE PROCESS OF REDUCING NOx
COMPOUNDS WITH AMMONIA INTO
NITROGEN AND WATER VAPOURS IN
PRESENCE OF CATALYST.

72. SSCCRR SSYYSSTTEEMM CCOOMMPPOONNEENNTTSS
 REDUCTANT STORAGE TANK
 PUMP
 VAPORIZER (NOT IN CASE OF
ANHYDROUS AMMONIA)
 MIXER
 INJECTION NOZZELS
 CATALYST CHAMBER

73. WWOORRKKIINNGG OOFF SSCCRR SSYYSSTTEEMM
 AFTER TREATMENT TECHNIQUE
 REDUCTANT(AMMONIA) IS INJECTED
AND MIXED INTO EXHAUST
 PASS THIS MIXTURE THROUGH
CATALYST CHAMBER
 TEMPERATURE OF CATALYST
CHAMBER SHOULD BE 450K-720K

75. RREEAACCTTIIOONNSS IINNVVOOLLVVEEDD

76. RREEDDUUCCTTAANNTTSS UUSSEEDD
 ANHYDROUS AMMONIA
 AQUEOUS AMMONIA
 UREA

77. CCAATTAALLYYSSTT UUSSEEDD
 BASE METAL OXIDES SUCH AS
(VANADIUM AND TUNGSTEN)
 TITANIUM OXIDE
 ZEOLITE (HIGH TEMPERATURE
DURABILITY)

78. EEXXHHAAUUSSTT GGAASS
RREECCIIRRCCUULLAATTIIOONN
 REDUCES LOCAL COMBUSTION
TEMPERATURE.
 HIGH SPECIFIC HEAT OF EXHAUST GAS
AND WATER VAPOUR.
 DECREASES OXYGEN
CONCENTRATION.

81. BBUUBBBBLLEE BBAATTHH SSCCRRUUBBBBEERR

83. EMISSION TRADE
 Credit based system
 This system was proposed by the swedish ship
owners association.
 Large combustion installations are capped by
their maximum annual emissions.
 Installation that emits less than its allocated
credits can trade the difference in the
emissions market.

85. HOW IT WORKS?
 Emission reductions become a tradable
commodity, which can be bought and sold like
any other product in the market.
 Each ship will be allocated points depending
on its yearly emissions in tons.
 Trading can be made anonymously through an
emissions market.

86. CONCLUSION
 Emission control is a necessity to make
shipping transport viable.
 CSR and Green marketing are the new buzz
words.
 One time investment and high returns.
 Decrease in peak temperature can limit NOX
emission.
 Limit SOX by removing sulphur prior
combustion.

87. REFERENCES
 Reduction of NOx and SOx in an emission a snapshot of
prospects and benefits for ships in the northern European
SECA area.
 www.imo.org
 MARPOL consolidated edition 2006
 Exhaust emissions from ship engines - significance,
regulations, control technologies by Laurie Goldsworthy
 www.dieselnet.com

88. TTHHAANNKK YYOOUU