Appendix FNorthshore Process Boilers BART AnalysisNOx ControlAvailable and Applicable ReviewReference(s)Revised: June 8, 2006

Reference No.

1NOxPollution ControlTechnologyAvailable? Applicable? MPCA Taconite BART Report AWMA Journal 9/05 Other

2CommentsBasic PrincipleCombustion Controls1 Overfire Air (OFA) Yes Yesx xCombustion air is separated into primary and secondary flow sections to achievecomplete burnout and to encourage the formation ofN2rather than NOx2External Flue GasRecirculation (EFGR)Yes Yesx xMixes flue gas with combustion air which reduces oxygen content and thereforereduces flame temperature3 Low-NOx Burners Yes Yesx x xBurners are designed to reduce NOx formation through restriction of oxygen,flame temperature, and/or residence time4Induced Flue GasRecirculation BurnersYes Yesx x xNeed to be upfired. Needconvective loop to get gasrecirculatedDraws flue gas to dilute the fuel in order to reduce the flame temperature5 Low Excess Air Yes YesxReduces production Reduces oxygen content in flue gas and reduces flame temperature6Burners out of Service(BOOS)Yes NoxNeed capacity of allburners for worst casescenarioShut off the fuel flow from one burner or more to create fuel rich and fuel leanzones7 Fuel Biasing Yes NoxCombustion is staged by diverting fuel from the upper level burners to the lowerones or from the center to the side burners to create fuel-rich and fuel-lean zones8 Reburning Yes Yesx xPart of the total fuel heat input is injected intothe furnace in a region above theprimary (main burners) flames to create a reducingatmosphere (re-burn zone),where hydrocarbon radicals react with NOx to produce elemental nitrogen9 Load Reduction Yes YesxThis is a strategy to reduce load on a power plantby reducing the electricaldemand throught efficiency projects.10 Energy Efficiency Projects Yes Yesxdecrease amount of fuel required to make an acceptable product11 Coal Drying Yes YesxRequires available excessheat.Dry coal will increase the as-burned BTU value, andtherefore less fuel is requiredto be burned. Specific energy efficiency project14 Combustion Zone Cooling Yes Yesx xCould reduce loadcapabilitiesCooling of the primary flame zone by heat transferto surrounding surfacesY:\23\38\131\NMC Process Boilers List of Control Technologies 2006-07-11.xls1 of 4Appendix FReference(s)Revised: June 8, 2006

Reference No.

1NOxPollution ControlTechnologyAvailable? Applicable? MPCA Taconite BART Report AWMA Journal 9/05 Other

2CommentsBasic Principle15 Alternate Fuels Yes Yesx xRequires case by caseanalysis. Typically,facilities experience lowerNOx when burning solidfuels.Lower combustion temps with solid fuels vs gas. May also reduce fuel NOx byusing a fuel with less nitrogen.16Oxygen EnhancedCombustionNo Nox xResearch level A small fraction of the combustion air is replaced with oxygen.17 Preheat Combustion No Nox xResearch levelPulverized coal preheated and volatiles and fuel-bound nitrogen compounds arereleased in a controlled reducing atmosphere wherethe nitrogen compounds arereduced to N2.18 ROFA-ROTAMIX Yes Yesx xCombination of OFA and SCR. Wall-fired or tangentially-fired furnace thatutilizes high velocity overfire air. Additional NOxreductions are achieved withammonia injection (Rotamix)19 NOx CEMS Yes YesxOptimization of combustion20 Parametric Monitoring Yes YesxOptimization of combustion38Catalyst Injection(EPS Technologies)No NoxResearch LevelA combustion catalyst is directly injected into theair intake stream and deliveredto the combustion site, initiating chemical reactions that change the dynamics ofthe flame.Post Combustion Controls21Non-Selective CatalyticReduction (NSCR)Yes Nox xFor clean services. Toomuch stuff in flue gaswould poison catalystUnder near stoichiometric conditions, in the presence of a catalyst, NOx isreduced by CO, resulting in nitrogen (N2) and carbon dioxide (CO2).22Low Temperature Oxidation(LTO) - Tri-NOx®Yes Yesx xRequires ozone generationUtilizes an oxidizing agent such as ozone to oxidize various pollutants includingNOx23Low Temperature Oxidation(LTO) - LoTOxYes Yesx x xHas been included as an"applicable and available"technology in recent BACTanalyses from multiplefacilities.Utilizes an oxidizing agent such as ozone to oxidize various pollutants includingNOxY:\23\38\131\NMC Process Boilers List of Control Technologies 2006-07-11.xls2 of 4Appendix FReference(s)Revised: June 8, 2006

Reference No.

1NOxPollution ControlTechnologyAvailable? Applicable? MPCA Taconite BART Report AWMA Journal 9/05 Other

2CommentsBasic Principle24Selective Catalytic Reduction(SCR)Yes Yesx x xNeed to inject atappropriate temperature.Applicable on clean sideonly.Ammonia (NH3) is injected into the flue gas stream in the presence of a catalystto convert NOx into N2and water25 Regenerative SCR Yes YesxClean side only26Selective Non-CatalyticReduction (SNCR)Yes Yesx x xUrea or ammonia-based chemicals are injected into the flue gas stream to convertNO to molecular nitrogen, N2, and water27 Adsorption No NoxStill in research stages. Use of char (activated carbon) to adsorb oxides of nitrogen28 Absorption Yes YesxSimilar to TriNOxUse of water, hydroxide and carbonate solutions, sulfuric acid, organic solutions,molten alkali carbonates, or hydroxides to absorb oxides of nitrogen.29 Oxidizer Yes YesxRedundant to regenerativeSCRGas stream is sent through the regenerative, recuperative, catalytic or direct firedoxidizer where pollutants are heated to a combustion point and destroyed.30 SNOX No Nox xEarly commercialdevelopment stageCatalytic reduction of NOx in the presence of ammonia (NH3), followed bycatalytic oxidation of SO2to SO3. The exit gas from the SO3converter passesthrough a novel glass-tube condenser in which the SO3is hydrated to H2SO4vapor and then condensed to a concentrated liquid sulfuric acid (H2SO4).31 SOx-NOx-Rox-Box No NoxTechnology has not beendemonstratedDry sorbent injection upstream of the baghouse forremoval of SOx and ammoniainjection upstream of a zeolitic selective catalytic reduction (SCR) catalystincorporated in the baghouse to reduce NOx emissions.32 Electron (E-Beam) Process No Nox xNo operating commercialapplications on coalElectron beam irradiation in the presence of ammonia to initiate chemicalconversion of sulfur and nitrogen oxides into components which can be easilycollected by conventional methods such as an ESP orbaghouse.33 Electrocatalytic Oxidation No NoxSimilar to cold plasma.Will keep watch foravailability of thistechnologyUtilizes a reactor in which SO2, NOx, and mercury are oxidized to nitrogendioxide (NO2), sulfuric acid, and mercuric oxide respectively using non-thermalplasma.On recent project, the vender was doing final trials on full-scale applications.Y:\23\38\131\NMC Process Boilers List of Control Technologies 2006-07-11.xls3 of 4Appendix FReference(s)Revised: June 8, 2006

Reference No.

1NOxPollution ControlTechnologyAvailable? Applicable? MPCA Taconite BART Report AWMA Journal 9/05 Other

2CommentsBasic Principle34 NOXSO No NoxCommercial version ofadsorption. Limitedexperience (proof-ofconcept tests).Uses a regenerable sorbent to simultaneously adsorbSO2and NOx from flue gasfrom coal-fired utility and industrial boilers. Inthe process, the SO2is convertedto a saleable sulfur by-product (liquid SO2, elemental sulfur, or sulfuric acid) andthe NOx is converted to nitrogen and oxygen.35 Copper-Oxide No Nox xAbsorption and SCR.Experience limited to pilotscale.SO2in the flue gas reacts with copper oxide, supported on small spheres ofalumina, to form copper sulfate. Ammonia is injected into the flue gas before theabsorption reactor and a selective catalytic reduction-type reaction occurs thatreduces the nitric oxides in the flue gas. In the regeneration step, the coppersulfate is reduced in a regenerator with a reducingagent, such as natural gas,producing a concentrated stream of SO2.36 Cold Plasma No NoxResearch Level37 Biofilters Yes NoxResearch levelGas stream is passed through a filter medium of soil and microbes. Pollutants areadsorbed and degraded by microbial metabolism forming the products carbondioxide and water.38 Pahlman Process No NoxResearch LevelGas stream is passed through a filter baghouse in which specially-developed,small-particle, high-surface area metal oxide sorbent have been deployed.Pollutants are removed from the gases by adsorption.1) This number is for reference only. It does notin any way rank the control technologies.2) a) Air Pollution: Its Origin And Control. Wark,Kenneth; Warner, Cecil F.; and Davis, Wayne T. 1998. Addison Wesley Longman, Inc.b) US EPA Basic Concepts in Environmental Science, Module 6, http://www.epa.gov/eogapti1/module6/index.htmc) New and Emerging Environmental Technologies,http://neet.rti.org/d) ND BART ReportsY:\23\38\131\NMC Process Boilers List of Control Technologies 2006-07-11.xls4 of 4