Upload
hanga
View
212
Download
0
Embed Size (px)
Citation preview
Wärtsilä Power Plants KTH/Emissions
April 27, 2006Thomas Stenhede 1
Emissions of IC-engines
•Exhaust gases•Water•Noise
•Residuals
Wärtsilä Power Plants KTH/Emissions
April 27, 2006Thomas Stenhede 2
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
Wärtsilä Power Plants KTH/Emissions
April 27, 2006Thomas Stenhede 3
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
Wärtsilä Power Plants KTH/Emissions
April 27, 2006Thomas Stenhede 4
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
Wärtsilä Power Plants KTH/Emissions
April 27, 2006Thomas Stenhede 5
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
Wärtsilä Power Plants KTH/Emissions
April 27, 2006Thomas Stenhede 6
Thermal NOX formation
Nitrogen source: combustion air
Formation process: extremely complex including hundreds of different reactions
Strong temperature influence (exponential)
NOX Formation Process
Wärtsilä Power Plants KTH/Emissions
April 27, 2006Thomas Stenhede 7
Mechanism for NO2 formation:
NO + HO2 ==> NO2 +OH
NOX Formation Process
Wärtsilä Power Plants KTH/Emissions
April 27, 2006Thomas Stenhede 8
“partly oxidized fuel”
HC + 1/2 O2 => CO + H2O
due to: - quenching
CO formation process
Wärtsilä Power Plants KTH/Emissions
April 27, 2006Thomas Stenhede 9
“totally or partly unburned fuel”
HC + O2 => CO2 + H2O
due to quenching
HC formation process
Wärtsilä Power Plants KTH/Emissions
April 27, 2006Thomas Stenhede 10
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
Wärtsilä Power Plants KTH/Emissions
April 27, 2006Thomas Stenhede 11
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
Wärtsilä Power Plants KTH/Emissions
April 27, 2006Thomas Stenhede 12
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
Wärtsilä Power Plants KTH/Emissions
April 27, 2006Thomas Stenhede 13
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
Wärtsilä Power Plants KTH/Emissions
April 27, 2006Thomas Stenhede 14
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
Wärtsilä Power Plants KTH/Emissions
April 27, 2006Thomas Stenhede 15
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
Wärtsilä Power Plants KTH/Emissions
April 27, 2006Thomas Stenhede 16
Principle of Selective Catalytic Reduction
Wärtsilä Power Plants KTH/Emissions
April 27, 2006Thomas Stenhede 17
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
Wärtsilä Power Plants KTH/Emissions
April 27, 2006Thomas Stenhede 18
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
Wärtsilä Power Plants KTH/Emissions
April 27, 2006Thomas Stenhede 20
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
Wärtsilä Power Plants KTH/Emissions
April 27, 2006Thomas Stenhede 21
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
Wärtsilä Power Plants KTH/Emissions
April 27, 2006Thomas Stenhede 22
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