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Umbrella NOx Reduction StrategyFor Existing & New Refineries
What is NOx?
• NOx is oxides of nitrogen– Including NO, NO2, and N₂O
• NOx has adverse effects on health & the environment– Acid rain, smog, depletion of
ozone in upper atmosphere.
• Emission of NOx is regulated – Permits for maximum NOx
emission vary by region
API 536: Post-Combustion NOx
Control for Fired Equipment in
General Refinery Services
NOx Formation
• Fuel NOx
• Thermal NOx
• Prompt NOx
C
N N
NPredominate in Coal and Oil
Predominate in Gas Firing
More Predominate at
Lower Flame Temperatures
O2 + N2 + = NOx
Nitrous Oxide, N₂O
Regulatory Perspective
• United States– Started in California– U.S. Clean Air Act (1967)– EPA formed (1970)
• EPA/DOJ Consent Decrees• Standards for Petroleum Refineries (1974)
– American Clean Energy & Security Act (‘09)• Passed the House of Representatives• Refiners responsible for GHG emissions
– Cap & trade next???
NOxContinuing trend of tightening legislation
NOx Reduction Trend (EEA)
Europe also aggressive in NOx reduction
Legislative Drivers
• IPPC (Integrated Pollution Prevention Committee)
• LCPD (Large Combustion Plant Directive)
Global NOx Reduction Trend
UNFCCC – United Nations Framework Convention on Climate Change
KYOTO Protocol – 1998
Nghi Son
Esmeralda
Reducing Thermal NOx
• Reduce O2
– Excess Air Control
• Reduce Flame Temperature– Staged Fuel Burners
• Reduce O2 and Flame Temperature– Fluegas Recirculation (FGR)
– Inert Gas Injection (steam)
– Internal FGR (IFGR)
– Fuel Induced Recirculation (FIR)
O2 + N2 + = NOx
Oxygen
Concentration
in Flame Zone
Flame
Temperature
Courtesy of Callidus
Factors Affecting NOx• Furnace Geometry
• Firebox Temperature
Narrow Width Short Length Multi-Level
Hydrogen
Ethylene
Boilers
Factors Affecting NOx
• Tramp Air
Solution: Anticipate & Control
• Oxygen Migration
Solution: Sealing
Factors Affecting NOx
• Burner Tip Plugging
– Affects Operation (flame quality)
– Affect Performance (staging)
• Solution: Fuel Conditioning
Burner
Options:
- Piping: SS or CS, New or Existing
- Filters and/or Coalescers
- Insulation and/or Heat Tracing
Filter /
Coalescer
Factors Affecting NOx
• Oxygen Control
– Proper Burner Design
• Custom Dampers, etc
– Manual/Automatic=
f(operation) Process in
Process out
AT
O2
PT
AT
COAC
PC
CONSTRAINT
Are You Planning For?
• NOx Regulation?
• Technology Selection?
• Implementation Timeframe?
• Operations Impact?
• Budget Impact?
Common Refinery NOx Sources
Range of NOx Reduction Options
• LoTox
• Ultra low NOx burners
• Selective Non Catalytic Reduction
• Selective Catalytic Reduction
• Fuel conditioning
• Combustion modifications
• Proper excess air maintenance
• Flue gas recirculation
• Burners out-of-service
Operating Considerations Technology Considerations
……Best Available Technologies
Cost Effectiveness (CE)
• Select interest rate, project life
• Determine “Application CE”
• Not “Technology CE”
CE = (Capital Cost EPC + Operating + Maintenance) Cost/Year
Tons of NOx Removed/Year
Calculate for cost effectiveness by “application”
Seek lowest
€ / lb of NOx
Reduction
Range of NOx reduction options
• Flue gas recirculation– Up to 30% reduction
• Ultra Low NOx burners– Up to 60% reduction
• Selective Non-Catalytic reduction– Up to 75% reduction
• Selective Catalytic Reduction– Up to 95% reduction
Seek lowest
€ / lb of NOx
Reduction
Recommend Baseline Analysis
• One size (solution) does not fit all!
• Baseline of existing application / installation:– Fuel
– Age of the equipment
– License of the equipment
– Configuration of furnace
– APH installed?
– Sealed for tramp air?
– FGR installed?
Factors necessary
to determine
incremental NOx
reduction potential
Crude & Vacuum Heaters
• Optimal solution to reach plant-wide NOx target:
– Retrofit with an SCR
USA
Crude & Vacuum Heaters2nd Illustration
• Optimal solution to reach plant-wide NOx target:
– Retrofit with an SCRCentral SCR and Air Preheat System
for multiple crude & vacuum units
USA
Selective Catalytic Reduction
CFD Modeling
Mechanical Design
• 4NH₃ + 4NO + 0₂ 4N₂ 6H₂O• 4NH₃ +2NO₂ + O₂ 3N₂ + 6H₂O
SCR Technology
Low Temperature
325° F - 680° F
(sulfur dependent)
Conventional
550° F - 750° FHigh Temperature
800° F - 1100° F
SCR Operating Philosophy
Design Factors
• Flue gas: flow rate & temperature
• Inlet NOx concentration
• Required NOx reduction efficiency
• Ammonia slip
• SO₂ and SO₃ levels
• Particulate loading rate
• Allowable pressure drop
• Physical site characteristics
• Location relative to other equipment in Flue Gas station
• Catalyst poisons
Alternative Option / SNCR• Ammonia or Urea Injection
• Temperature window 1500° - 1800° F
• Factors: Residence time, geometry, distribution & steady state operation
• NOx reduction 40 - 75%
Typical bridge wall temperatures:
Hydrotreater 1450°F – 1700°FCat. reformer 1450°F
Steam Superheater 1800°F
Change in temperature
from floor to arch is 200°F.
NH3 evaporator
NH3 + carrier
Bridge wall
Coker
• Optimal solution to reach plant-wide NOx target:
– Retrofit with LoNOxburners Courtesy
of Callidus
Alternative OptionUltra Low NOx Burners
• CUBL Ultra LoNOxburner reduces NOx by two methods:
– Highly staged (in excess of 80%)
– Mix stage fuel with re-circulated flue gas
Courtesy of Callidus
Heat Recovery Steam Generator
• Optimal solution to reach plant-wide NOx target:
– Retrofit with an SCR
USA
Steam Reformer
• Optimal solution to reach plant-wide NOx target:
– Design with SCR (new capital project)
Middle East
Hydrogen
Gas Turbine
• Optimal solution to reach plant-wide NOx target:
– Retrofit with SCR
USA
Fluid Catalytic Cracking Unit
• Optimal solution to reach plant-wide NOxtarget:
– Retrofit with SCR
Citgo
USA
Summary of Options
5,000 10,000 15,000 20,000
Cost Effectiveness €/ton NOx Removed)
Ultra LoNOx burners;
large emitter
SCR; large emitter
Tech
no
log
y R
an
ge
Cost Effectiveness Range
SCR; small emitter
Central SCR / multiple units
Low
High
€/ton
LoNOx burners;
small emitter
LoNOx burners; large emitter
Improved operating efficiency
Peter Armstrong
Director of Business Development
713.816.5784 (Houston, Texas)
Grazie
