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### SNCR System Design, Installation, and Operating Experience DavidWojichowski, Principal De-NOxTechnologies, LLC6/21/02 DOE NETL Pittsburgh 2002 2 

### The Basic Process • SNCR is a gas phase reaction between ammonia radicals and NO to form N2 and water in the absence of a catalyst.

• Strong Temperature Dependence NH2-+ NO +1/2O2 N2 + 2 H2O6/21/02 DOE NETL Pittsburgh 2002 3 

### The First Patent • First patented by Exxon for use on combustion effluents in 1975, using ammonia. • Established required temperature range andstoichiometry/performance. • Patent expired in 1990.6/21/02 DOE NETL Pittsburgh 2002 4 

### Other Patents • EPRI was soon thereafter granted a very similar patent , using urea, in 1980. • EPRI furthered the art by patenting SNCR in excess of 2000 degrees F in the absence of oxygen. • Commercialized in the late 80’s. • The original two EPRI process patents have expired as well.6/21/02 DOE NETL Pittsburgh 2002 5 

### The Perfect World • In laboratory conditions (insulated tubular reactor with perfect mixing and unlimited residence time), NOx reduction greater than 90% has been demonstrated. • Ideal Conditions – Temperature of 1800F, Residence time greater than 0.5 seconds.6/21/02 DOE NETL Pittsburgh 2002 6 "Perfect World" SNCR @NSR=2

-20 0 20 40 60 80 100

1318 1408 1498 1588 1678 1768 1858 1948 2038 2128 Temperature (F)% NOx Reduction

0.2 sec 0.4 sec 0.6 sec 1.0 sec6/21/02 DOE NETL Pittsburgh 2002 7 

### The Real World • Rapidly declining temperatures • Access limitations • Imperfect mixing • Liquid evaporation time delay • Load swings • Operator indifference • Carbon Monoxide • Ammonia Slip is Important6/21/02 DOE NETL Pittsburgh 2002 8 

### Closest to Perfect • Waste Incinerators, Wood/Bark Boilers, CFB’s, some PC Boilers. • All are characterized by reasonable furnace plan dimensions, well defined gas profiles, and adequate residence time prior to first convective surface. • Common performance is 50% reduction at NSR = 1.0 and ammonia slip L.T. 10 ppm.6/21/02 DOE NETL Pittsburgh 2002 96/21/02 DOE NETL Pittsburgh 2002 10 "Real World" SNCR @NSR=2

-20 0 20 40 60 80 100

1318 1408 1498 1588 1678 1768 1858 1948 2038 2128 Temperature (F)% NOx Reduction

0.2 sec 0.4 sec 0.6 sec 1.0 sec Optimum Injection Location6/21/02 DOE NETL Pittsburgh 2002 11 

### Ammonia Process • Simplest and least expensive* approach. • Gaseous injection. • Anhydrous ammonia has lowest delivered cost. • Storage and Handling issues. • Low boiler corrosion risk. * - Assumes typical tank/containment.6/21/02 DOE NETL Pittsburgh 2002 126/21/02 DOE NETL Pittsburgh 2002 13 

### Urea Process • Liquid Reagent, with or without atomization. • Higher reagent costs, but friendlier chemical. • Equivalent performance and stoichiometry. • More difficult to distribute reagent equally. • Local boiler corrosion common.6/21/02 DOE NETL Pittsburgh 2002 14 

### Design Considerations • Heat or Dilute • Load Range • Injector Location • Injector Number, Location, and Sizing • Controls • On-Site Urea Dissolver?6/21/02 DOE NETL Pittsburgh 2002 156/21/02 DOE NETL Pittsburgh 2002 16 

### Economic Summary • Installed Cost – Utility scale $5-10/kW • Installed Cost – Industrial $15-20/kW • Negligible Outage Costs • Operating Cost - $500-750 per ton NOx removed using urea6/21/02 DOE NETL Pittsburgh 2002 17 

### Optimization • The more injectors the better. • Use flat pattern nozzles if possible. • Check flow balance once per day. • Secondary dilution water quality is an issue. • Pull and inspect injectors once per week. • Generic reagent works fine.6/21/02 DOE NETL Pittsburgh 2002 186/21/02 DOE NETL Pittsburgh 2002 19 

### Operational Issues • Corrosion • Detached Plume Formation • Air HeaterPluggage • Nozzle Failure6/21/02 DOE NETL Pittsburgh 2002 20 

### Corrosion • Localized corrosion at liquid injected SNCR facilities is a problem. • Generally located in immediate vicinity of injector ports, or on opposite walls of narrow boilers. • Especially problematic for fuels with high chloride and sulfur.6/21/02 DOE NETL Pittsburgh 2002 21 

### LOCALIZED CORROSION6/21/02 DOE NETL Pittsburgh 2002 22 

### Short Term Corrosion Fixes • Reduce liquid impingement • Extended wall injectors • Higher air pressure/flow • Lower water flow • Inconneloverlay6/21/02 DOE NETL Pittsburgh 2002 23 

### Long Term Corrosion Fix • Evaporate solution prior to injection. • OTA (Once Through Ammonia) System – Patent Pending. • Simpler, Cheaper, Smaller. • Demo in 2002.6/21/02 DOE NETL Pittsburgh 2002 24 

### Plume Issue • Quite common in non-scrubbed flue gas • Most often detached from the stack • Caused by condensation/combination at lower temperatures. • Ammonium chloride, ammonium bisulfate, +?6/21/02 DOE NETL Pittsburgh 2002 25 

### Plume Suppression
• Slip reduction – keep less than 10ppm • Nozzle orientation/operation key. • Get good stack and operational data. • Ammonia monitors recommended for non-scrubbed facilities.6/21/02 DOE NETL Pittsburgh 2002 26 

### Not so fast • Detached plumes can be difficult to diagnose and solve. • Plumes observed at near zero slip • Plumes not observed at high slip • Not obvious from manual sampling analysis.6/21/02 DOE NETL Pittsburgh 2002 27 

### Air Heater Plugging/Corrosion • Ammonium Bisulfate is a liquid above 300F • Sticky material - difficult to remove. • Not a problem with low sulfur fuels • Again, minimize slip • Another good reason for an ammonia monitor.6/21/02 DOE NETL Pittsburgh 2002 28 

### Injector Burn-out • High Temperature Corrosion • Erosion • High alloy with heavy wall thickness • Interchangablelances6/21/02 DOE NETL Pittsburgh 2002 296/21/02 DOE NETL Pittsburgh 2002 30 

### Combination Technologies • Very compatible with combustion controls.

– LowNOx Burners

– OFA Injection

– GasReburning • NOxreduction approaching that of SCR at lower capital cost - $30/kW, 60-80% reduction.6/21/02 DOE NETL Pittsburgh 2002 31 

### SNCR Summary • Mature Technology • Fuel Indifferent • Low cost alternative for first 50% reduction. • Easily retrofitted • Compatible with combustion modifications for High NOxremoval