Title: NOx Emissions Control from Industrial Boilers, Furnaces, and Gas Turbines
1NOx Emissions Control from Industrial Boilers,
Furnaces, and Gas Turbines
- Larry Swanson
- David Moyeda
- GE Energy
Alberta Research Council NOx and SOx Control
Technologies Symposium Alberta, Canada 9 April
2008
2Fuel Impact on Sources of NOx
- Thermal NOx
- Formed by the thermal fixation of molecular
nitrogen, N2 - Requires high temperatures (gt 1,370C)
- Fuel NOx
- Oxidation of nitrogen bearing species contained
in the fuel - Prompt NOx
- Reaction of nitrogen with fuel fragments
3Approaches to NOx Control
Technique
Gas
Fuel Oil
Coal
Operational Modifications
Low Excess Air
X
X
X
Reduced Air Preheat
X
X
Fuel Biasing
X
Burners Out of Service (BOOS)
X
X
Combustion Equipment Modifications
Flue Gas Recirculation (FGR)
X
X
Overfire Air (OFA)
X
X
X
Steam Injection
X
Low-NOx Burners (LNB)
X
X
X
Reburning
X
X
Post-Combustion Techniques
Selective Non-Catalytic Reduction (SNCR)
X
X
X
Selective Catalytic Reduction (SCR)
X
X
X
4NOx emissions control technologies vary in
performance and cost
LNB
OFA
Reburning
SNCR
SCR
NOx Control Technologies
Components Involved
Replace or Modify burners
X
Staged Air Injection
X
X
Staged Fuel Injection
X
Nitrogen Agent Injection
X
X
Catalyst Reactor
X
Nominal NOx Reduction
30-50
20-30
50-60
15-35
80-90
LNB Low-NOx Burners OFA Overfire Air SNCR
Selective Non-Catalytic Reduction SCR Selective
Catalytic Reduction
5Technology layering reduces NOx emissions to low
levels
Main Fuel
Air
6Overfire air consists of air staging to reduce
NOx emissions
- Overfire Air (OFA) moves a portion of the
combustion air to a location away from the main
combustion zone. - Combustion staging reduces conversion of
fuel-bound nitrogen into NOx and lowers thermal
NOx formation.
Overfire Air
Main Fuel
Air
7Application of overfire air and SNCR to CO boiler
with refractory furnace
Overfire Air
8Application of overfire air and SNCR to CO boiler
with refractory furnace
High TFN Baseline
Low TFN Baseline
TFN Total Fixed Nitrogen (NH3, HCN, NO) NSR
Nitrogen Agent Stoichiometric Ratio
9Reburning process consists of both fuel and air
staging to reduce NOx emissions
- NOx generated in the main combustion zone reacts
with fuel fragments injected into the reburn
zone, reducing it to molecular nitrogen. Overfire
air addition completes combustion in the burn-out
zone.
Overfire Air
Reburn Fuel
Main Fuel
Air
10All hydrocarbon fuels can be used as a reburn
fuel on different types of units
11Industrial boiler retrofit with gas reburning
system
Overfire Air Injectors
Reburn Fuel Injectors
Low-NOx Burners Firing High-N Fuel
12Selective non-catalytic reduction consists of
nitrogen agent injection
SNCR
- Technology involves the injection of a nitrogen
agent (ammonia, urea, etc.) into the
post-combustion flue gases. - At the proper temperature, the SNCR reagent
selectively reduces NO to molecular nitrogen.
Main Fuel
Air
13SNCR reaction occurs in narrow temperature window
Reaction chemistry involves reagent activation
and reaction with NO
At high temperatures, reagent is oxidized to
NOx. At low temperatures, reagent does not react,
leading to ammonia slip.
14Impact of gas temperature and reagent on SNCR
performance
- Several reagents are available for SNCR
applications. - At ideal conditions, SNCR can yield high levels
of NOx reduction. - Reagent performance depends on mode of injection
and application specific conditions.
15Typical SNCR systems
Ammonia
to Unit
from Skid
Mixer
Indirect Steam Vaporizer
NH3 Supply
Steam Heat Exchanger
Blower
Flue Gas
Urea
to Unit
Piping System
Main Fuel
Urea Tank
Dilution Water
Urea Pump
Air
16Use of CFD for SNCR system design
Droplet Trajectories Temperature Contours
Resulting Contours of NOx Concentration
17Application of SNCR to furnace
Temperature
Flue Gas Outlet
Convective Pass
Off-Gas Ports
CO Levels
Burners
Combustion Air Ports
18SNCR performance on industrial furnace
19Gas Turbine NOx Control DLN-1
- Benefits
- Guarantee 5ppm NOx 25ppm CO
- Firing temperature range 2020-2100F
- Retrofit design for 7EA, 6B and 9E
- 24K CI combustor hardware
- No impact on turbine durability
- Demonstrated Ability
- Fielded 7EA unit July 2005
- 7 turbines in operation (several customers)
- Sub 5 ppm NOx, 25 ppm CO
- Closed Loop Emissions Control
- 48,000 fleet hours of operation
- Fleet leader has 14300 hours of operation
20Teaming with industry to develop innovative
combustion solutions
Headquarters Santa Ana, CA
CFD Modeling
Physical Flow Modeling
Pilot-Scale Combustion Testing
21e
22Reburn zone stoichiometric ratio is optimum
around 0.9
23All hydrocarbon fuels can be used as a reburn fuel
24Influence of flue gas parameters on SNCR
temperature window
- Influence on Temperature Window
- Increase in Flue Gas Parameter
- CO
- O2
- SO2
- CO2
- NOx
- H2
- Agent/NOx (NSR)
- Temp Quench
25Reburn achieved 50-70 NOx reduction on all units
26Tangentially fired boiler retrofit with low-NOx
burners, reburn, SNCR
- Plant Somerset Station
- Location Massachusetts, USA
- Capacity 120 MW
- Fuel Bituminous coal
- Integrated NOx Control Solution
- Low-NOx Burners
- Gas Reburn System
- Urea Injection System
SNCR System (not shown)
Overfire Air Injectors
Reburn Fuel Injectors
Low-NOx Burners
27Performance achieved with low-NOx burners, gas
reburn, SNCR
28GE Emissions Technology Leadership
- First
- Premixed Combustor
- E-class Dry Low NOx (DLN)
- 15 ppm DLN (E Class)...DLN1
- 9 ppm DLN (E Class)...DLN1
- 9 ppm DLN (F Class)...DLN2.6
29DLN1 System Advancements
9ppm DLN1
Dilution
5ppm DLN1
Premixing
- Integrated aft mount
- Cloth seals
- Class C TBC
Independent pilot gas
Dilution
Extendor wear surfaces
Can Level Primary Fuel Tuning Valves
Closed Loop Emissions Control (CLEC)
30DLN 1 Enhancement for 3 ppm NOx
Low Emissions Technology Advancement
- Technologies
- Flame stabilization
- Fuel distribution
- Closed-loop controls
- Variation reduction
DLN1 9 ppm
DLN15 ppm
3 ppmGoal
CO (ppmvd)
- Demonstrated 36 hours Sub 3 ppm
- Demonstrated 1280 hours Sub 3.5 ppm
- Commitment for 8 operational turbines at sub 3
ppm NOx in April 2008
NOx (ppmvd _at_ 15 Oxygen)