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Nox and sox emission control

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Nox and sox emission control

  1. 1. NOX AND SOX EMISSION CONTROL
  2. 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. 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. 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. 5. HAZARDS  Corrosion  Climate change  Photochemical smog  SO2 irritates the eyes, nose and lungs  SO2 causes acid rain  NO2 causes pulmonary edema
  6. 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. 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. 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. 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
  10. 10. 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
  11. 11. 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.
  12. 12. EMISSION MEASUREMENT  For Attaining Interim Certificate of Compliance.  Engines combined into engine groups by manufacturer  Engine from this group selected for emission testing
  13. 13. EXHAUST GAS MONITORING TECHNIQUES Exhaust Gas Monitoring Equipments EExxttrraaccttiivvee SSyysstteemmss NNoonn--EExxttrraaccttiivvee SSyysstteemmss UUVV AAnnaallyysseerrss Chemi-luminescence IInnffrraarreedd AAnnaallyysseerrss UUllttrraa--VViioolleett AAnnaallyysseerrss
  14. 14. 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
  15. 15. 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.
  16. 16. 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.
  17. 17. ULTRA-VIOLET ANALYSERS  Particularly useful for measuring SO2 .  Used in extractive and non-extractive systems.  Not suitable for the measurement of NOx.
  18. 18. 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.
  19. 19. 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 )
  20. 20. 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.
  21. 21.  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.
  22. 22. 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
  23. 23. 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.
  24. 24. REMOVAL OF SOX AFTER COMBUSTION TTHHEE SSEEAAWWAATTEERR SSCCRRUUBBBBEERR SSPPRRAAYY DDRRYY SSYYSSTTEEMM WWEELLLLMMAANN--LLOORRDD PPRROOCCEESSSS LLIIMMEESSTTOONNEE //GGYYPPSSUUMM SSYYSSTTEEMM FFLLUUEE GGAASS DDEESSUULLPPHHUURRIISSAATTIIOONN ((FFGGDD))
  25. 25. 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
  26. 26.  Advantage :  SO2 reduction around 90 %  Disadvantages :  limestone has to be stored onboard  large quantities of gypsum waste is produced
  27. 27. 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.
  28. 28. 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.
  29. 29. 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..
  30. 30. FFeeaattuurreess  Uses Cyclone Technology  The system needs only a little extra space  Aeration of the effluent is necessary  high degree of recirculation
  31. 31. 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.
  32. 32.  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.
  33. 33. OPERATIONAL CONCERNS AROUND THE CHANGE TO LOW SULPHUR FUELS  REDUCED FUEL VISCOSITY  FUEL ACIDITY  IGNITION AND COMBUSTION QUALITY  FUEL LUBRICITY
  34. 34. REDUCED FUEL VISCOSITY  MGO and MDO fuels have a lower inherent viscosity than heavy fuel oil which can :  Effect Diesel Engines  Effect Steam Boilers
  35. 35. 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
  36. 36. 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
  37. 37. 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).
  38. 38. IIGGNNIITTIIOONN AANNDD CCOOMMBBUUSSTTIIOONN QQUUAALLIITTYY  Effect On Diesel Engines  Effect On Steam Boilers
  39. 39. 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.
  40. 40. 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.
  41. 41. 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
  42. 42. 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
  43. 43. FFAACCTTOORRSS AAFFFFEECCTTIINNGG NNOOxx FFOORRMMAATTIIOONNSS  SPEED OF ENGINE  MAXIMUM TEMPERATURE INSIDE CYLINDER  COMPRESSION RATIO/PEAK PRESSURE  AMOUNT OF SCAVENGE AIR
  44. 44. NNOOxx RREEDDUUCCTTIIOONN TTEECCHHNNIIQQUUEESS PRE-TREATMENT INTERNAL MEASURE (PRIMARY METHODS) AFTER TREATMENT (SECONDARY METHODS)
  45. 45. NNOOxx RREEDDUUCCTTIIOONN TTEECCHHNNIIQQUUEESS PRE-TREATMENT INTERNAL MEASURE (PRIMARY METHODS) AFTER TREATMENT (SECONDARY METHODS)
  46. 46. AALLTTEERRNNAATTIIVVEE FFUUEELLSS  METHANOL  LIQUIFIED PETROLEUM GAS
  47. 47. MMEETTHHAANNOOLL  50% REDUCTION  NO SULPHUR  BAD IGNITION QUALITY  CORROSIVE  EXPENSIVE FUEL
  48. 48. LLIIQQUUIIFFIIEEDD PPEETTRROOLLEEUUMM GGAASS  BUTANE(C4H10)+PROPANE(C3H8)  LOW ENERGY DENSITY SO MORE FUEL CONSUMPTION  NON-CORROSIVE  NON-TOXIC
  49. 49. 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
  50. 50. NNOOxx RREEDDUUCCTTIIOONN TTEECCHHNNIIQQUUEESS PRE-TREATMENT INTERNAL MEASURE (PRIMARY METHODS) AFTER TREATMENT (SECONDARY METHODS)
  51. 51. MMOODDIIFFIICCAATTIIOONNSS IINN CCOOMMBBUUSSTTIIOONN PPRROOCCEESSSS  INJECTION TIMING RETARDATION  INCREASE IN INJECTION PRESSURE  OPTIMIZATION OF INDUCTION SWIRL  MODIFICATION OF INJECTOR SPECIFICATION  CHANGE IN NUMBER OF INJECTORS
  52. 52. 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
  53. 53. IINNCCRREEAASSEE IINN IINNJJEECCTTIIOONN PPRREESSSSUURREE  COMBINED WITH OTHER TECHNIQUES  PROVIDES BETTER ATOMIZATION
  54. 54. OOPPTTIIMMIIZZAATTIIOONN OOFF IINNDDUUCCTTIIOONN SSWWIIRRLL  COMBINED WITH OTHER NOx REDUCTION TECHNIQUES  HELPS IN GOOD COMBUSTION  NO ADDITIONAL COST
  55. 55. IINNJJEECCTTOORR SSPPEECCIIFFIICCAATTIIOONNSS  INJECTION PRESSURE  NUMBER AND ANGLE OF HOLES  SIZE OF HOLES
  56. 56. 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
  57. 57. 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
  58. 58. WWAATTEERR IINNJJEECCTTIIOONN  DURING COMBUSTION THROUGH SPECIAL INJECTOR  REDUCES THE BULK TEMPERATURE OF COMBUSTION  40% REDUCTION IN NOx EMISSION IS ACHIEVED
  59. 59. WWAATTEERR IINNJJEECCTTIIOONN LLIIMMIITTAATTIIOONNSS  NEED OF SEPARATE PUMP FOR FUEL AND WATER  COST FACTOR  CORROSION
  60. 60. NNOOxx RREEDDUUCCTTIIOONN TTEECCHHNNIIQQUUEESS PRE-TREATMENT INTERNAL MEASURE (PRIMARY METHODS) AFTER TREATMENT (SECONDARY METHODS)
  61. 61. WWHHAATT IISS SSCCRR?? SELECTIVE CATALYST REDUCTION IS THE PROCESS OF REDUCING NOx COMPOUNDS WITH AMMONIA INTO NITROGEN AND WATER VAPOURS IN PRESENCE OF CATALYST.
  62. 62. SSCCRR SSYYSSTTEEMM CCOOMMPPOONNEENNTTSS  REDUCTANT STORAGE TANK  PUMP  VAPORIZER (NOT IN CASE OF ANHYDROUS AMMONIA)  MIXER  INJECTION NOZZELS  CATALYST CHAMBER
  63. 63. 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
  64. 64. RREEAACCTTIIOONNSS IINNVVOOLLVVEEDD
  65. 65. RREEDDUUCCTTAANNTTSS UUSSEEDD  ANHYDROUS AMMONIA  AQUEOUS AMMONIA  UREA
  66. 66. CCAATTAALLYYSSTT UUSSEEDD  BASE METAL OXIDES SUCH AS (VANADIUM AND TUNGSTEN)  TITANIUM OXIDE  ZEOLITE (HIGH TEMPERATURE DURABILITY)
  67. 67. EEXXHHAAUUSSTT GGAASS RREECCIIRRCCUULLAATTIIOONN  REDUCES LOCAL COMBUSTION TEMPERATURE.  HIGH SPECIFIC HEAT OF EXHAUST GAS AND WATER VAPOUR.  DECREASES OXYGEN CONCENTRATION.
  68. 68. BBUUBBBBLLEE BBAATTHH SSCCRRUUBBBBEERR
  69. 69. 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.
  70. 70. 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.
  71. 71. 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.
  72. 72. 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
  73. 73. TTHHAANNKK YYOOUU

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