Thomas Stenhede 1 April 27, 2006 - Energiteknik | KTH · g/kWhe mg/MJfuel mg/Nm3 ppm-vol ppm-vol 5%...

Wärtsilä Power Plants KTH/Emissions

April 27, 2006Thomas Stenhede 1

Emissions of IC-engines

•Exhaust gases•Water•Noise

•Residuals



NOx:• acid rain, acidification• ozone/smog formation in the lower atmosphere • (potential damage on vegetation and human health)

CO:• detrimental to health

Hydrocarbons/VOC:• ozone/smog formation in the lower atmosphere• some considered• contribute to the greenhouse effect

Paticulates:• detrimental to health in lungs

CO2:• contribute to the greenhouse effect

Sulphur:

• acid rain, acidification• affects components erosion and corrosion

Exhaust compounds and their environmental impact



Red - diesel engines

Blue - otto engines

g/kWhe mg/MJfuel mg/Nm3 ppm-vol ppm-vol5% O2 dry 15% O2 dry act O2 dry

NOx 14 1630 5350 985 14901,3 153 500 92 140 TA-luft0,65 76 250 46 70 ½TA-luft

CO 0,9 595 298 90 1352,3 1520 760 230 345

THC 0,7 80 258 134 2026,5 740 2400 1240 1880

Used units for NOx values



Comparison diesel (W32) vs. gas engine (W34SG)

Diesel-engine Otto-engine

Fuel HFO Natural gas

Power (bmep) 22.9 bar 20 bar

Shaft output per cyl 460 kWm 450 kWm

Efficiency shaft (η) 44.5 % 46.1 %.

Exhaust gas temp 347 °C 400°C

Nitrogen oxides (NOx) 14.4 g/kWh 1.2 g/kWh

Carbon monoxide (CO) 0.9 g/kWh 2.2 g/kWh

Hydrocarbons (THC) 0.7 g/kWh 6.5 g/kWh

Particulates 0.5 g/kWh 0.07 g/kWh

Carbon dioxide (CO2) 650 g/kWh 450 g/kWh



Nitrogen N2 : 76%Oxygen O2: 13%Carbon dioxide CO2: 6% Low due to

high efficiencyWater H2O: 5%

Carbon monoxide CO Low due to good combustion

Hydrocarbons CXHy - “ -

Nitrogen oxides NOX To be controlled

Typical Exhaust Gas Composition of a Diesel Engine



Thermal NOX formation

Nitrogen source: combustion air

Formation process: extremely complex including hundreds of different reactions

Strong temperature influence (exponential)

NOX Formation Process



Mechanism for NO2 formation:

NO + HO2 ==> NO2 +OH

NOX Formation Process



“partly oxidized fuel”

HC + 1/2 O2 => CO + H2O

due to: - quenching

CO formation process



“totally or partly unburned fuel”

HC + O2 => CO2 + H2O

due to quenching

HC formation process



Rated engine speed (rpm)Test Procedure according to IMO NOx Technical CodeReference Fuel: Marine Diesel OilImplementation: New Ships from 1.1.2000

0

20

18

16

14

12

10

8500

NO

xem

issi

ons,

wei

ghte

d (g

/kW

h)

1000 1500 2000

NOx (g/kWh) = 17= 45 x rpm= 9.8 2000

130 rpm < 130

rpm ><rpm < 2000-0.2

IMO Global Marine NOx Regulation



NOx Reduction Application:potential:

• Engine modifications 25-35 % All fuels

New installationsRetrofit installations

• Direct Water 50-60% All fuelsInjection New installations

Retrofit installations

• SCR Catalyst 85-95% All fuelsNew installationsRetrofit not alwayspossible

NOx Control Concepts



Rearranged diesel cycleVery late fuel injection startHigher compression ratioHigher fuel injection pressureOptimized combustion chamber

ResultsLower combustion temperaturesShorter duration at high temperatures

ConclusionsNOX reduction typically 25-35%Unaffected fuel consumption

Low Nox Combustion Engine Design



Typical water content of exhaust gas:

Without Direct Water Injection: 5 %-volumeWith Direct Water Injection: 7 %-volume

Typical difference in exhaust temperature:

15-20 oC lower exhaust temperature with Direct Water Injection

DWI - Exhaust Water Content and Temperature



NOx emission compliance of Wärtsilä engines

CASS = Combustion Air Saturation SystemSCR = Selective Catalytic Reduction

SPEC

IFIC

NO

EM

ISSI

ON

S (g

/kW

h)

x

4

6

10

12

14

16

0 200 400 600 800 1000 1200 1400 1600 1800 2000

2

RPM

18

20

0

IMO proposal

Medium-speed High-speedLow-speed

SCR

Low NOx combustion

EPA and EU proposal for 2007IMO -30%

Direct water injection or CASS8



What are the alternatives for 30 % NOx reduction?

• Dry technologies (Low NOx combustion)• Miller timing +VIC• SOI retard• Common Rail• EGR (Only for sulphur free fuels)

• Wet technologies• Fuel/Water Emulsion• Humidification of suction air• WetPack• DWI

• SCR (Selective Catalytic Reduction)

NOx reduction technology



Principle of Selective Catalytic Reduction



Before Entering the Reactor:(NH2)2 CO + H2O 2 NH3 + CO2

In the Reactor:4 NO + 4 NH3 + O2 4 N2 + 6 H2O6 NO2 + 8 NH3 7 N2 + 12 H2O

SCR Reactions with Urea



Before catalyst

THC 1380 ppm

CO 900 mg/Nm3 5%O2

NOx 42 mg/MJ

NMHC 282 mg/Nm3 act% O2

O2 12,4 %

After catalyst

THC 1280 ppm

CO 46 mg/Nm3 5%O2

NMHC 180 mg/Nm3 act% O2

Conversion factor:

THC 7,2 %

CO 95 %

NMHC 35%

Pripps

3*W18V28SG Engine #2with catalyst

Operating conditions:

Generator power 4265 kW

El efficiencies 40,8%

Charge air pressure 2,5 bar

Ign angle 14,5





Water effluents originates from cooling waterwhich contains various additives which must beconsider before emitted into the sewage system.

When anti-freeze additives are used propyleneglycol is preferred instead of ethylene glycol.

Water



Lubricating oil

•Gas engines normally consume lube oils, which is emitted via the stack

•Diesel engines, running on sulphur containing oils, must change oil from time to time based on theTBN value, such oils must be properly disposed



A plant consists of four main sound sourcesNoise levels are given as sound power levels and the totalsound pressure level shall be estimated at a given distance.

Sound source Sound power level Distance Sound pressure levelat origin dB(A) m dB(A) μPa/m2 p2=Σpi

2

Stack 90 35 48,3 5182 27E+6Radiators 70 35 28,3 518 269E+3Air intake 70 40 27,1 454 206E+3Builing&equipm 60 35 18,3 164 27E+3Total plant noise 48,4 5230 27E+6

Back ground noise 50,0 6325 40E+6Plant noise 48,4 5230 27E+6Total noise 52,3 8207 67E+6Sphere/semi-sphere propagation 6Unit sphere diam 0,282

BG 50,0Plant 48,4Total 52,3

Building andequipment

Air intake

Radiators

FenceMeasuring

point

Sitearea

Noise

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Thomas Stenhede 1 April 27, 2006 - Energiteknik | KTH · g/kWhe mg/MJfuel mg/Nm3 ppm-vol ppm-vol 5%...

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