Post on 23-Feb-2016
description
MEASURES TO REDUCE NOx EMISSIONS
M. Sc. Engineering Policy and Technology Management Energy Management and Policy
Por:Miguel Leocádio
João Meyer
MEASURES TO REDUCE NOMEASURES TO REDUCE NOxx EMISSIONS EMISSIONS
MEASURES TO REDUCE NOx EMISSIONS
M. Sc. Engineering Policy and Technology Management Energy Management and Policy
• Flame Temperature (above~1600ºC)
• Presence of O2 (Slightly lean mixtures)
PRIMARY MEASURESPRIMARY MEASURESModification of the Combustion Process
NOx formation strongly depends on:
MEASURES TO REDUCE NOx EMISSIONS
M. Sc. Engineering Policy and Technology Management Energy Management and Policy
PRIMARY MEASURESPRIMARY MEASURES
• Low Excess Air • Reduce the air inlet into combustion chamber
Main fe
atures
: •Simple to implement
•Inflammability problems
•Possible formation of unburned fuel & CO
•Efficiency: 10 - 44%
MEASURES TO REDUCE NOx EMISSIONS
M. Sc. Engineering Policy and Technology Management Energy Management and Policy
• Air Staging • Divide combustion into 2 separate zones
1. Lack of Oxygen Zone2. Excess of Oxygen zone
• Biased Burner Firing (BBF)Lower burners: Oxygen; Upper Burners:
Oxygen • Burners Out Of Service (BOOS)
Lower Burners Oxygen; Upper Burners not in use
• Over Fire Air (OFA)Air ports (15-30%) installed in addition to existing
burners
10-65% Efficiency
PRIMARY MEASURESPRIMARY MEASURES
MEASURES TO REDUCE NOx EMISSIONS
M. Sc. Engineering Policy and Technology Management Energy Management and Policy
• Flue Gas Recirculation
• Reduction of available oxygen in chamber• Decrease of flame temperature (dilution effect)
• Difficult adaptation• Increase fan work• Flame instability
Main fe
atures
:
Introduction of Flue gas (20-30%) into chamberGas Should be cleaned
20-50% Efficiency
PRIMARY MEASURESPRIMARY MEASURES
MEASURES TO REDUCE NOx EMISSIONS
M. Sc. Engineering Policy and Technology Management Energy Management and Policy
• Reduced Air Preheat
Disavan
tages:
Inlet Air temperature For the same fuel
amount
Lower flame temperature
20-30% Efficiency
• Reduction of Thermal efficiency (Carnot)• Increase of fuel consumption or bigger heat
exangers for maintaining energy output
PRIMARY MEASURESPRIMARY MEASURES
MEASURES TO REDUCE NOx EMISSIONS
M. Sc. Engineering Policy and Technology Management Energy Management and Policy
• Fuel Staging (Reburning)
Main Fea
tures:
Staged injection of fuel and air
50-60% Efficiency
• Slightly lean primary zone• Rich reburning zone• Reburning zone temp.~1200ºC• Increased residence time• Conditioned to site specifications
85-90%
PRIMARY MEASURESPRIMARY MEASURES
MEASURES TO REDUCE NOx EMISSIONS
M. Sc. Engineering Policy and Technology Management Energy Management and Policy
• Low NOx Burner
Traditionally:- Air and fuel introduced at the same time- Hot oxidizing primary zone + colder secondary zone at flame end
Now: Air Staged LNOx Burner Flue Gas LNOx Burner Fuel Staged LNOx Burner
PRIMARY MEASURESPRIMARY MEASURES
MEASURES TO REDUCE NOx EMISSIONS
M. Sc. Engineering Policy and Technology Management Energy Management and Policy
• Air Staged Low NOx Burner
• Flame instability• Incomplete Burn Out
25-30% Efficiency
Disavan
tages:
PRIMARY MEASURESPRIMARY MEASURES
MEASURES TO REDUCE NOx EMISSIONS
M. Sc. Engineering Policy and Technology Management Energy Management and Policy
• Flue Gas Recirculation Low NOx Burner
• Zones separated with flue gas
• High N content fuels
up to 20% Efficiency
PRIMARY MEASURESPRIMARY MEASURES
MEASURES TO REDUCE NOx EMISSIONS
M. Sc. Engineering Policy and Technology Management Energy Management and Policy
• Fuel Staged Low NOx Burner
• Very Lean Primary zone (low temperatures)
• Rich Secondary zone Reduction of already formed NOx.
• Burnout zone
50-60% Efficiency
PRIMARY MEASURESPRIMARY MEASURES
MEASURES TO REDUCE NOx EMISSIONS
M. Sc. Engineering Policy and Technology Management Energy Management and Policy
End-of-Pipe techniques to reduce the NOx already formed
Injection of Ammonia or Urea in the flue gas to reduce
NOx to molecular Nitrogen
(Independently or in combination with primary measures)
• Selective Catalytic Reduction (SCR)
• Selective Non Catalytic Reduction (SNCR)
Concep
t:
How:
Forms:
SECONDARY MEASURESSECONDARY MEASURES
MEASURES TO REDUCE NOx EMISSIONS
M. Sc. Engineering Policy and Technology Management Energy Management and Policy
• The reducing agent is injected into the flue gas upstream of the catalyst
• Selective Catalytic Reduction (SCR)
• NOx conversion takes place on the catalyst surface at a temperature between 300 and 450ºC
Materials: Heavy metal oxides, zeolites, iron oxides and activated carbon
SECONDARY MEASURESSECONDARY MEASURES
MEASURES TO REDUCE NOx EMISSIONS
M. Sc. Engineering Policy and Technology Management Energy Management and Policy
4 NO + 4 NH3 + O2 4 N2 + 6 H2O
6 NO2 + 8 NH3 7 N2 + 12 H2O
4 NO + 2 (NH2)2CO + 2 H2O + O2 4 N2 + 6 H2O + 2 CO2
with urea as a reduction agent:
with ammonia as a reduction agent:
6 NO2 + 4 (NH2)2CO + 4 H2O 7 N2 + 12 H2O + 4 CO2
• Selective Catalytic Reduction (SCR)
SECONDARY MEASURESSECONDARY MEASURES
MEASURES TO REDUCE NOx EMISSIONS
M. Sc. Engineering Policy and Technology Management Energy Management and Policy
4 NO + 4 NH3 + O2 4 N2 + 6 H2O
6 NO2 + 8 NH3 7 N2 + 12 H2O
with ammonia as a reduction agent:
Homogeneous mixing of ammonia with the flue gasInjection through a system of nozzles and addictionally the
placement of static mixer in the exhaust gas channel
Homogeneous NH3 / NOx ratio in the exhaust gasNOx removal efficiency vs. NH3 slip
Main fe
atures
:
• Selective Catalytic Reduction (SCR)
SECONDARY MEASURESSECONDARY MEASURES
MEASURES TO REDUCE NOx EMISSIONS
M. Sc. Engineering Policy and Technology Management Energy Management and Policy
Existing configuration of abatement technologies
• Selective Catalytic Reduction (SCR)
SECONDARY MEASURESSECONDARY MEASURES
MEASURES TO REDUCE NOx EMISSIONS
M. Sc. Engineering Policy and Technology Management Energy Management and Policy
• Selective Catalytic Reduction (SCR)SECONDARY MEASURESSECONDARY MEASURES
MEASURES TO REDUCE NOx EMISSIONS
M. Sc. Engineering Policy and Technology Management Energy Management and Policy
• It is operated without a catalyst at a temperature between
850 and 1100ºC• The temperature window is strongly dependent on the reagent used
(ammonia, urea or caustic ammonia)
• Selective Non Catalytic Reduction (SCR)
4 NH3 + 5 O2 4 NO + 6 H2O
4 NO + 4 NH3 + 5 O2 4 N2 + 6 H2O
Using ammonia as a reagent:
SECONDARY MEASURESSECONDARY MEASURES
MEASURES TO REDUCE NOx EMISSIONS
M. Sc. Engineering Policy and Technology Management Energy Management and Policy
SECONDARY MEASURESSECONDARY MEASURES
• Selective Non Catalytic Reduction (SCR)
MEASURES TO REDUCE NOx EMISSIONS
M. Sc. Engineering Policy and Technology Management Energy Management and Policy
Additive and NOx must undergo sufficient mixing
Main fe
atures
:
4 NH3 + 5 O2 4 NO + 6 H2O
4 NO + 4 NH3 + 5 O2 4 N2 + 6 H2O
Using ammonia as a reagent:
The size of additive drops
reduced NOx abatement rate vs. NH3 slip
NH3 / NOx ratio must be ammonia-rich rather thanstoichiometric
Optimization of the NH3 / NOx molar ratio (1.5 - 2.5)
• Selective Non Catalytic Reduction (SCR)
SECONDARY MEASURESSECONDARY MEASURES
MEASURES TO REDUCE NOx EMISSIONS
M. Sc. Engineering Policy and Technology Management Energy Management and Policy
Ammonia, caustic ammonia or urea
Criteria:
• formation of N2O (nitrous oxide)
• corrosion problems
Choice
of th
e add
itive:
• Selective Non Catalytic Reduction (SCR)
SECONDARY MEASURESSECONDARY MEASURES
MEASURES TO REDUCE NOx EMISSIONS
M. Sc. Engineering Policy and Technology Management Energy Management and Policy
General performance of secondary measures to reduce NOX emissonsGeneral performance of secondary measures to reduce NOX emissons