Air Pollution and GHG Emissions • Low NOx Emission Technologies for Gas Turbines • GHG Emissions Prevention • Canadian and International Emissions Standards • Clean Energy Systems - Balancing Objectives
TransCanada PipeLines RB211dle
General Electric LM2500 CHP Plant
Manfred Klein Coordinator, Energy & Environment Gas Turbine Labs, National Research Council 613-949-9686
[email protected]
Typical Industrial Gas Turbine Energy Systems • • • • • • •
Simple Cycle, Standby power New Gas Combined Cycle Combined Cycle Repowering Utility Coal Gasification Large Industrial Cogen Oilsands Gasification Pipeline Compression
• • • • •
Small Industrial Cogeneration Municipal District Energy Micro-T Distributed Power/Heat Waste Heat Recovery Process Off-Gases, Biofuels
About 24 000 MW in Canada
2
Air Emissions Air Pollution • • • • • • •
Sulphur Dioxide SO2 Nitrogen Oxides NO2 Volatile Organics VOC Fine Particulates PM Mercury & Heavy Metals Ammonia NH3 Carbon Monoxide CO
GHGs • • • •
Carbon Dioxide CO2 Methane CH4 Nitrous Oxide N20 SF6 et al
Ozone Depletion • CFCs Individual .. or …
System 3
What are Cleaner Energy Choices? Low Air Pollution, GHG Emissions, Air Toxics and Water Impacts
• Aggressive Energy Conservation and Efficiency • Small Renewable Energies, Biomass Fuels • High Efficiency Nat. Gas Systems (GTCHP, GTCC) • Large Hydro & Nuclear Facilities • Coal & Bitumen Gasification, Polygen w/CCS
New GT systems can lead to large GHG red’ns
• Energy Delivery; pipes & wires • Waste Energy Recovery
‘Clean Energy’ definition ? - Include thermal energy ?
IEA WEO ‘Blue Map’
4
Air Pollution NOx Emissions
CO NOx
O + N2 N + O2
NO + N NO + O
3 Compounds of Concern:
2000 K
NO, NO2 smog , N2O ghg Thermal NOx: High Temperature Combustion Fuel NOx: From N2 Content of Oil, Coal •
Nitrous Oxide is N2O, a GHG (Solar Turbines)
T
Fuel Combustion CxHy + (x + y/4) O2 = x CO2 + Energy Content
Carbon Hydrogen Sulphur CO
Coal ~ CH
BTU/lb
14 000 61 000 4 000 4 400
Oil ~ CH2
y/2
H2O + heat
GJ/kg
33 142 (LHV, 120) 9 10
Nat. Gas CH4
Simple CO2 Calculations - Energy (Heat RateHHV x CO2 factor) Coal Heavy Oil Natural Gas Gasoline
85-95 kg/GJ 74 kg/GJ 50 kg/GJ 68 kg/GJ ~ 2.4 kg/litre
Examples Coal Boiler
10 GJ/MWhr x 90 kgCO2/GJ
=
900 kgCO2/MWhr
Gas Cogen
6 GJ/MWhr x 50 kgCO2/GJ
=
300 kgCO2/MWhr
Car
10 l /100km x 20000 km x 2.4 kg/l =
4.8 tCO2/yr
Kg/MWh
3
Air Pollution
2.5
Comparing Emissions from Thermal Energy Systems
SO2 NOx PM
2 1.5 1 0.5
“Cannot produce Air Pollution without making CO2”
0 Coal
Oil
Gas
GTCC
GTCHP
Bio
IGCC
1200 Kg/MWh
1000
• Natural Gas
800
• Coal and Oil
600
• Biomass and Syngas
400
‘Integrated analyses’
Carbon Dioxide
200 0 Coal
Oil
Gas
GTCC GTCHP
Bio
IGCC
Emissions in Gas Turbine Engines Factors Affecting NOx Emissions
• Unit efficiency ( AIR mass flow, Pressure Ratio, Turbine Inlet Temp) • Engine type (Aero or Frame) • Dry Low NOx combustor
• Full & Part load operation, starts • Cold and hot weather, humidity • Type of air compressor (spools) • N1/N2, Output Speeds • Specific Power (kW, per lb/sec air) • NOx Concentration vs Mass Flow
NOx Reduction Methods Steam/Water Injection • Prevention, 2/3 red‟n to 1 kg/MWhr • Some Combustion Component Wear • Plant Efficiency Penalty • Depends upon value of plant steam
(Kawasaki)
Selective Catalytic Reduction (SCR) •
NH3 injection in HRSG catalyst, ~ 80% NOx Red‟n
• Backend Control - Ammonia emissions & handling (toxic), - fine PM, N2O ? - Cold Weather, Cycling duty - ammonia slip - Efficiency loss in HRSG - Full Fuel Cycle impact – Prod‟n, Delivery etc
IST Aecon
EA Assessments of Gas Turbine Plants (2002
Study, for TransCanada P/L and Environment Canada)
• Companies may be required to install added ammonia-based SCR controls after DLN • Ammonia transportation & handling is a serious local health and safety issue • Given the capital & operating costs and collateral impacts associated with SCR systems, the environmental benefits do not justify the economic expense. (T. McCann, B. Howard, M. Klein)
Marginal, low $/tonne benefit after DLN
Dry Low Emissions Combustion • Preventative reduction by 60-90% • Maintains High Efficiency
• Good experience with large industrial units • Some Reliability Issues for Aeroderivatives • Too Low Values may lead to inoperability and combustor problems • How important are CO emissions? • Effects of Plant Cycling
• Applied to Syngas combustion ?
Solar SoLoNox
Dry Low NOx on Large GT Units
Annular EV burner
GE Frame 7F, DLN2
Alstom
Siemens
DLN Systems for GE Heavy Duty Gas Turbines
Aero-Derived DLN Systems
GE LM6000 DLE Triple Annular Dome
Air flow Air gas mixture Combustion products Cooling air
Rolls Royce Canada
Rolls Royce Canada RB211 DLE
Gas Turbine Emission Guidelines & Standards Objectives • Prevention of Air Pollution,Toxics • Minimize GHGs • Energy Conservation • System Efficiency • Size and Location • Minimize Water Impacts • Noise
• Reduce CFCs • Energy Security • Emissions Trading
NOVA Chemicals, Joffre AB
Look for solutions with; Multiple Economic Benefits, Systems Analysis Balanced Approach
Clean Energy Balancing Act Energy Supply Choices
Energy Security
Global Atmosphere Climate & Ozone Layer
Conservation & Efficiency
Emissions Trading
Policy, Regulations, Technology
Demand & Consumption System Reliability
Economic Performance 17
Examples of International Standards – 2005 (for GT Units Larger than ~ 10 MWe, gas fuel)
United States United Kingdom Germany France Japan Canada Australia EU LCPD World Bank • •
2 - 42 ppm 60 mg/m3 75 mg/m3 50 mg/m3 * 15 - 70 ppm 140 g/GJout * 70 mg/m3 50 - 75 mg/m3 * 125 mg/m3
Facility Cogeneration Incentives (Values Subject to Change) Uncontrolled NOx levls were 100-300 ppm (200-600 mg/m3 )
Sample Emissions Unit Conversions for NOx Percent O2 conversions for ppmv • from 25 ppmv at 15% O2 to value for 16% O2 = 21 ppmv 3% O2 = 76 ppmv
NOx ppmv to mg/Nm3 with the same % O2 basis • from 50 mg/m3 = 24 ppmv
Natural Gas at 15% O2 (LHV Basis, fuel input)
• 25 ppmv NOx = 0.099 lb/MMBTU (= 42.9 g/GJ) 1 lbNOx/MMBTU = 252 ppmv
Diesel fuel at 15% O2 (LHV Basis, fuel input) 25 ppmv NOx = 0.10 lb/MMBTU (= 43.5 g/GJ)
From Solar Turbines (mysolar.cat.com) See “Customer Support” Toolbox
Gas Turbine Emissions Criteria Traditional concentration (ppm, mg/m3) and fuel input (g/Gjin , lb/MMBTU) criteria; • • • •
difficult to interpret do not give appropriate design signal do not encourage system efficiency do not encourage Pollution Prevention
• Aviation uses ‘LTO’ Operations Cycle • Recip engines have kg/MWhr rules
ICAO - aircraft (kgNOx/thrust)
Output-based Rules; Mass per Product Output (kg/tonne, kg/MWhr, g/GJout ) tonnes/yr $/tonne $/MWhr
Lbs/HpHr
Canadian GT Emission Guidelines (1992) • Guideline Reflects National Consensus • Balanced NOx Prevention Technology • Regulatory Certainty • Output-Based Standard for Efficiency (140 g/GJout Power + 40 g/GJ Heat) • • • • • • •
Engine Sizing Considerations Promotes Cogeneration and low CO2 Peaking units ( 20 MWe
10 20
40
60
Overall Plant Thermal Efficiency %
80
100
New US EPA Rules for Gas Turbines Can choose Output-based, or Concentration-Based Rules (EPA OAR-2004-0490) Size, Heat Input (MMBTU/hr)
ppm
(New Units, Natural Gas Fuel) < 50 (electricity, 3.5 MWe) (mechanical, 3.5 MW) 50 to 850 (3 – 110 MW) Over 850 (> 110 MW)
42 100 25 15
2.3 5.5 1.2 0.43
Units in Arctic, Offshore < 30 MW > 30 MW
150 96
8.7 4.7
• MW could include MWth for waste heat in CHP • Efficiency based, SCR likely not required • Flexible Emissions Monitoring
lb/MWhr
Alberta Environment NOx Emission Guidelines (Gas Turbines for Electricity Generation, 2005)
Size
3-20 MW 20-60 MW over 60
Alberta
CCME
(kg/MWhr)
(kg/MWhr)
0.6 0.4 0.3
0.86 0.5 0.5
-
MWhr includes power and thermal energy.
-
Alberta levels were developed through CASA in 2004 as a modest reduction from national CCME levels, also taking into account the needs of larger units over 60 MW in size.
Gas Turbine Operability in Cold Climates • How well does DLN operation adjust to very cold ambients ? (-30 to - 50oC) • How can unit power & efficiency be optimized during cold weather ? • Acoustic Oscillations, noise
TCPL Northern Ontario
• How important are CO emissions? • Remote O&M capabilities • Can an Output-based GT design contribute to solutions?
Rolls Royce RB211dle
Stittsville ON (MK)
Combustor Dynamics “Humming” Acoustic Oscillations Under Transient Conditions, caused by; • Ultra-Low NOx ppm Design • CO and turndown req‟ts • Cyclic GT Unit Loading • Ambient Temp, Pressure Ratio, Fuel properties (Nat Gas, LNG, Syngas ...)
(turbinetech.com)
1. Natural Frequencies and Resonance 2. Vibration, Trips & Shutdown 3. „Zero‟ GT emissions
use coal instead?
(KEMA)
Waste Heat and Duct Burners in CHP • Duct Burners for auxiliary firing can double/triple steam output from HRSG ~100 % efficiency for heat) • Duct burners can add a bit of combustion NOx, … but they allow a smaller size of GT engine for given heat load (reduces annual fuel & emissions) • Also increases heat transfer, lowers stack temp • HRSG naturally silences GT exhaust noise IST
Heat : Power ratio (Solar Turbines)
(Coen)
Duct Firing Creates a higher Heat:Power ratio which can enhance system efficiency and plant operating flexibility. To meet periodic high steam demands; - Lowers stack exhaust temperature, improving heat recovery and efficiency
C. Meyer-Homji, Bechtel Corp.
Allows for a smaller Gas Turbine engine choice, or avoids an additional Boiler
Are there PM2.5 particulate emissions from gas-fired turbines? (AP42 - 0.07 lb/MWhr ?)
?
2 million t/yr Air
Air Filter 99.8%
60 kT/yr fuel
Does dry NG combustion produce fine PM emissions? What is the Inlet-Exhaust mass balance ?
Are there any Air Toxics ?
Emissions Measurement • Compliance and Emission Inventories • Emissions Trading - NOx, SO2, CO2 • • • •
Continuous Emissions Measurement Process Estimation Methods Surrogate & parametric methods Predictive Emissions Monitoring
CEM Specialties
PEMs; • • • •
good predictability of GT operation cost-effective emissions reporting process efficiency optimization a good solution for DLN facilities
Emissions Averaging Time is Important Env Can CEM van at TCPL, ON
Env‟tl Solutions for Gas Pipeline Compression • Efficient and Reliable Gas Turbine, with DLN Combustion
• Minimizing Stops and Starts • Waste Heat Recovery • Gas-to-Gas Exchange, Aerial Coolers • Dry Gas Seals to reduce methane leakage, and reduced Venting
Gas Compressor Dry Gas Seals
• Air or Hydraulic Engine Starters • System Optimization
Aerial coolers
TCPL/EPCOR, Nipigon, ON
Critical Elements for CHP Systems Producing 2-3 forms of energy from the same fuel, in same process. •
Awareness of Opportunities
•
Nearby Site
•
Plant Sizing to Match Thermal Load
•
Seasonal Heat/Cooling Design
•
Electrical Utility Interconnection
•
Availability of Gas, Bio, H2 fuels
•
Low Air Pollution, Local Impacts
•
Greenhouse Gases & Allocation
•
Output-based Emission Rules
•
Energy Quality (Exergy)
32
Gas Turbine Emission Prevention & Control (NOx, GHGs) CEM or PEM
Proper Thermal Sizing
HRSG Heat
HEPA filter Duct Firing
Steam or N2 injection
Selective Catalytic Reduction ? CH4 Leakage Prevention Maximizing System Output CHP Efficiency
Dry Low NOx Combustion
H2 , Syngas Fuels
System Reliability GE Power Systems33
Env’tl Assessment of Mackenzie Gas Pipeline (2004-06) 95% of GHG & NOx emissions are from gas turbine units and small gensets - 20 gas turbines (270 MW) - 10 small recip engines (13 MW) • NOx combustion levels which are too low will cause engine instability. • CCME Guideline balances NOx prevention to moderate level, with low GHGs • Cold weather, O&M considerations BAT = • Dry Low NOx, Waste Heat Recovery • BMPs for fugitive, vented methane • Maintain system reliability
(Imperial Oil)
Solid Fuel Gasification System Air N2
Air separation
CO2
To pipeline
Water O2
Coal Petcoke
Gasifier
CO
H2
Gas Cleanup
Water Shift Reaction
Slag
H2
Sulphur
Difficult Dry Low NOx solution - need dilution from N2 Is very low ppm NOx necessary, or even possible ?
Is this a gas plant, or a coal plant?
Gas Turbine Combined Cycle
MW
Process Heat
N2 Injection
Fuel Flexibility - Combustion Characteristics of SynGas Fuels Hydrogen • High Volume and Heat Value • High Flame Temp. • High Flame speed
• Flashback, auto-ignition • Higher NOx ? (Hannemann et al, Siemens)
Carbon Monoxide • High Flame Temp. • High Density • Low flame speed • Toxicity
(Solar Turbines)
Some Issues for Consideration … Gas Turbine is an Engine (hot pressurized air for Power & Heat) How can various types of Air Emissions be managed effectively ? What is the ‘right’ level of NOx emissions from a reliable system? Can ‘output-based’ design improve performance over a ‘ppmv’ design? How do we deal with off-design, cold weather & cycling conditions ? What does BAT or BACT mean ? Can CAP-ex choices be made consistent with OP-ex choices ? How can CAC and GHG emissions be reported effectively ?
Concluding Remarks • Gas Turbine & CHP systems represent key solutions • Best Available Technology: Waste Heat Recovery, DLN, Gasification • Cogeneration: HEAT POWER • Emissions: Air Pollution
Carbon Dioxide
• Fuel flexibility & Gasification are important GT challenges • Need ‘System Integration’ , Balancing of Issues • Need Collaborative R&D and Knowledge TCPL Ottawa
GTAA Pearson