1Comparison of Sodium Bicarbonate and Trona forSO2Mitigation at A Coal-Fired Power PlantYougen KongJim VysokySolvay Chemicals Inc.ELECTRIC POWER 2009Rosemont, IllinoisMay 12-14, 20092Presentation Outline•Plant Description•Dry Sorbent Injection of Sodium Bicarbonate•Results•Summary3Plant•Two units: 45 and 109 MW•One stack•Down-fired boiler•PRB coal–Moisture: 24.59%–Ash:4.86%–Heating value: 9,092 Btu/lb–Sulfur:0.27%–SO2: 0.59lb/mmBtu•Tubular air preheater•Fabric filters for PM control•Have usedtronafor SO2control for bothunits since 1980s4SiloEconomizerAir HeaterBoilerAirMillTronaBag HouseTrona Injection System5Trona Storage SiloThree silos for two units. Silo size: 6100 ft3– 150 tons of trona.6Trona Injection•103’ from fabric filterinlet•Duct: 17’3” wide 9’9”tall•Two separatesorbent supplysystems.•One system for eachduct side.•Each supply systemfeeds 6 injectionlances .•Two sides – 12injection lances total.•Normally run onlyone system.7Arrangement of Injection LancesAir Heater Exit Duct (view from the Boiler)WestEastA Side InjectorB Side Injector8Why Sodium Bicarbonate (NaHCO3)?•Sodium Bicarbonate is more effectivethan trona in SO2removal. In otherwords, less sorbent is needed for thesame SO2removal.–Lower sodium concentration in fly ash–Less waste disposal–More expensive9What is Sodium Bicarbonate?•NaHCO3-Baking soda•SOLVAir® Select SBC (sodium bicarbonate) ismanufactured at Solvay Chemicals’ Parachute,Colorado plant.•Starting January 2010, a new plant in Green River,Wyoming, will start to produce low cost sodiumbicarbonate based sorbent - SOLVAir® Select 300.•Either Select SBC or Select 300 is a coarse particleand requires milling prior to use. An air-classifier millis often used to reduce the particle size beforeinjection although other types of particle sizereduction devices may be appropriate.10Solvay Parachute Plant in Colorado•SOLVAir® Select SBC (sodium bicarbonate)11Solvay Plant in Green River, Wyoming•SOLVAir® Select 200 (trona)•SOLVAir® Select 300 (sodium bicarbonate)12Dry Sorbent Injection of Sodium Bicarbonate•Some studies in 1970s and 1980s showed goodperformance of sodium bicarbonate for SO2mitigation.•Have not achieved wide applications due to:•Product availability•High cost•Solvay Chemicals is building a plant in Green River,Wyoming, to produce low-cost sodium bicarbonatebased sorbent with a patented process:•Phase I: 125,000 tons/year starting 01/2010.•Phase II: Another 125,000 tons/year is forecast.13Heating Up Sodium Bicarbonate Makes Difference!Sodium BicarbonateT > 275 °F2NaHCO3Na2CO3CO2H2O+ +Activated Sodium Carbonate14Acid Mitigation Chemical Reactions•Na2CO3+SO2+1/2O2→Na2SO4+ CO2•Na2CO3+SO3→Na2SO4+ CO2•Na2CO3+ 2HCl→2NaCl+ H2O + CO2•Na2CO3+ 2HF→2NaF+ H2O + CO2Na2SO4,NaClandNaFare collected in fly ash.15•Sorbent injection rate /Normalized StoichiometricSorbent injection rate /Normalized StoichiometricRatio (NSR)Ratio (NSR)•Sorbent particle sizeSorbent particle size•Sorbent residence time in flue gas streamSorbent residence time in flue gas stream•Sorbent penetration and mixing with flue gasSorbent penetration and mixing with flue gas•Particulate control device used (ESP or Baghouse)Particulate control device used (ESP or Baghouse)•Flue gas temperatureFlue gas temperature–Minimum 275Minimum 275oF–The higher, the better up to 1500The higher, the better up to 1500oFParameters Affecting Performance16Effect of Sorbent Particle Size on SO2Removal(Lab Results on Fabric Filter)Effect of Sorbent Particle Size on SO2Removal @ NSR=10204060801000 10 20 30 40 50 60 70 80 90 100Particle Size d90(micron)

SO 2 Removal Rate (%)17TronaSOLVAir® Select 200(Na2CO3.NaHCO3.2H2O)D50: ~ 32 μmD90: ~ 162 μmAfter milling with a pin millD50: ~ 24 μmD90: ~ 74 μm18Sodium BicarbonateSOLVAir® Select SBC (sodiumbicarbonate NaHCO3)–D50: 110 μm–D90: 234 μmAfter Milling with a pin mill–D50: 28 μm–D90: 71 μm19SO2Removal Rates with Trona and Sodium Bicarbonate (SBC)•Flue gas temperature at the injection ports: ~ 290oF•Tested on 100 MW unit0102030405060700.0 0.2 0.4 0.6 0.8 1.0 1.2NSR

SO 2 Removal Rate (%)SBCTronaUnmilled SBC20NO2Formation0510152025300 20 40 60 80 100SO2Removal Rate (%)

NO 2 Concentration (ppm)Sodium BicarbonateTronaHigh NO2can cause brown plume21NO2Brown Plume•Two other trials showed NO2brown plume•Over 30 trona or sodium bicarbonate systemshave not shown this problem.•The exact mechanism of NO2formation isunknown.•The following measures can help avoid NO2brown plume:–Injection at high temperatures (i.e. upstream of airpreheater)–Use SCR or SNCR to lower NOx concentrationbefore injection.–Good mixing between injected sodium sorbent andflue gas.22Summary•Sodium Bicarbonate was able to remove more SO2thanTrona at the same NSR. At the same SO2removal rate,40% less reagent is required with sodium bicarbonate.•Less fly ash generated with Sodium Bicarbonate due toless sorbent needed.•There is some economical advantage to switch fromtrona to sodium bicarbonate.23For more information, please visit www.solvair.usQuestions?