MEASURES TO REDUCE NO x EMISSIONS M. Sc. Engineering Policy and Technology ManagementEnergy Management and Policy Por: Miguel Leocádio João Meyer MEASURES TO REDUCE NO x EMISSIONS

M. Sc. Engineering Policy and Technology ManagementEnergy Management and Policy Flame Temperature (above~1600ºC) Presence of O 2 (Slightly lean mixtures) PRIMARY MEASURES Modification of the Combustion Process NO x formation strongly depends on:

MEASURES TO REDUCE NO x EMISSIONS M. Sc. Engineering Policy and Technology ManagementEnergy Management and Policy PRIMARY MEASURES Low Excess Air Reduce the air inlet into combustion chamber Main features: Simple to implement Inflammability problems Possible formation of unburned fuel & CO Efficiency: %

MEASURES TO REDUCE NO x EMISSIONS M. Sc. Engineering Policy and Technology ManagementEnergy Management and Policy Air Staging Divide combustion into 2 separate zones 1.Lack of Oxygen Zone 2.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 MEASURES

MEASURES TO REDUCE NO x EMISSIONS M. Sc. Engineering Policy and Technology ManagementEnergy 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 features: Introduction of Flue gas (20-30%) into chamber Gas Should be cleaned 20-50% Efficiency PRIMARY MEASURES

MEASURES TO REDUCE NO x EMISSIONS M. Sc. Engineering Policy and Technology ManagementEnergy Management and Policy Reduced Air Preheat Disavantages: 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 MEASURES

MEASURES TO REDUCE NO x EMISSIONS M. Sc. Engineering Policy and Technology ManagementEnergy Management and Policy Fuel Staging (Reburning) Main Features: 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 MEASURES

MEASURES TO REDUCE NO x EMISSIONS M. Sc. Engineering Policy and Technology ManagementEnergy 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 MEASURES

MEASURES TO REDUCE NO x EMISSIONS M. Sc. Engineering Policy and Technology ManagementEnergy Management and Policy Air Staged Low NOx Burner Flame instability Incomplete Burn Out 25-30% Efficiency Disavantages: PRIMARY MEASURES

MEASURES TO REDUCE NO x EMISSIONS M. Sc. Engineering Policy and Technology ManagementEnergy Management and Policy Flue Gas Recirculation Low NOx Burner Zones separated with flue gas High N content fuels up to 20% Efficiency PRIMARY MEASURES

MEASURES TO REDUCE NO x EMISSIONS M. Sc. Engineering Policy and Technology ManagementEnergy 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 MEASURES

MEASURES TO REDUCE NO x EMISSIONS M. Sc. Engineering Policy and Technology ManagementEnergy Management and Policy End-of-Pipe techniques to reduce the NO x already formed Injection of Ammonia or Urea in the flue gas to reduce NO x to molecular Nitrogen (Independently or in combination with primary measures) Selective Catalytic Reduction (SCR) Selective Non Catalytic Reduction (SNCR) Concept: How: Forms: SECONDARY MEASURES

MEASURES TO REDUCE NO x EMISSIONS M. Sc. Engineering Policy and Technology ManagementEnergy Management and Policy The reducing agent is injected into the flue gas upstream of the catalyst Selective Catalytic Reduction (SCR) NO x 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 MEASURES

MEASURES TO REDUCE NO x EMISSIONS M. Sc. Engineering Policy and Technology ManagementEnergy Management and Policy 4 NO + 4 NH 3 + O 2 4 N H 2 O 6 NO NH 3 7 N H 2 O 4 NO + 2 (NH 2 ) 2 CO + 2 H 2 O + O 2 4 N H 2 O + 2 CO 2 with urea as a reduction agent: with ammonia as a reduction agent: 6 NO (NH 2 ) 2 CO + 4 H 2 O 7 N H 2 O + 4 CO 2 Selective Catalytic Reduction (SCR) SECONDARY MEASURES

MEASURES TO REDUCE NO x EMISSIONS M. Sc. Engineering Policy and Technology ManagementEnergy Management and Policy Homogeneous mixing of ammonia with the flue gas Injection through a system of nozzles and addictionally the placement of static mixer in the exhaust gas channel Homogeneous NH 3 / NO x ratio in the exhaust gas NOx removal efficiency vs. NH3 slip Main features: Selective Catalytic Reduction (SCR) SECONDARY MEASURES

MEASURES TO REDUCE NO x EMISSIONS M. Sc. Engineering Policy and Technology ManagementEnergy Management and Policy Existing configuration of abatement technologies Selective Catalytic Reduction (SCR) SECONDARY MEASURES

MEASURES TO REDUCE NO x EMISSIONS M. Sc. Engineering Policy and Technology ManagementEnergy Management and Policy Selective Catalytic Reduction (SCR) SECONDARY MEASURES

MEASURES TO REDUCE NO x EMISSIONS M. Sc. Engineering Policy and Technology ManagementEnergy 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 NH O 2 4 NO + 6 H 2 O 4 NO + 4 NH O 2 4 N H 2 O Using ammonia as a reagent: SECONDARY MEASURES

MEASURES TO REDUCE NO x EMISSIONS M. Sc. Engineering Policy and Technology ManagementEnergy Management and Policy SECONDARY MEASURES Selective Non Catalytic Reduction (SCR)

MEASURES TO REDUCE NO x EMISSIONS M. Sc. Engineering Policy and Technology ManagementEnergy Management and Policy Additive and NO x must undergo sufficient mixing Main features: The size of additive drops reduced NO x abatement rate vs. NH 3 slip NH 3 / NO x ratio must be ammonia-rich rather than stoichiometric Optimization of the NH 3 / NO x molar ratio ( ) Selective Non Catalytic Reduction (SCR) SECONDARY MEASURES

MEASURES TO REDUCE NO x EMISSIONS M. Sc. Engineering Policy and Technology ManagementEnergy Management and Policy Ammonia, caustic ammonia or urea Criteria: formation of N 2 O (nitrous oxide) corrosion problems Choice of the additive: Selective Non Catalytic Reduction (SCR) SECONDARY MEASURES

MEASURES TO REDUCE NO x EMISSIONS M. Sc. Engineering Policy and Technology ManagementEnergy Management and Policy General performance of secondary measures to reduce NOX emissons