1Dry Sorbent Injection of Sodium Sorbentsby Solvay ChemicalsEmission Control and MeasurementWorkshopMarch 24-25, 20102Presentation OutlinezWhat are the sodium sorbents?– We’ll talk about Trona and Sodium BicarbonatezHow effective are sodium sorbents in mitigatingSO2and SO3?– We’ll review some data.zWhich sorbent is better?– We’ll discuss the factors affecting the decision.zWhat parameters impact the effectiveness ofDSI?– We’ll look at how we optimize systems and factors thatlimit effectiveness.3What Is Trona?zIt is a naturally formed sodium sesquicarbonate rock– (Na2CO3•NaHCO3•2H2O)– The Green River WY deposit is the largest and purest in the worldzSolvay mills this rock into a fine powder– Average particle size 30 – 35 microns– Material for FGD is sold under the trade name SOLVAir Select 200– Select 200 is the product known as trona in the industryzSelect 200 is very dry, typically less than 0.03% moisture– It is a good idea to keep it dry, wet trona is tough to handle.– Contact with water will cause problems.zSelect 200 can compact while storedzSelect 200 calcines instantly at 280oF– Trona gives up water when it calcines– At 140oF Trona begins to calcine4Sodium BicarbonatezSodium Bicarbonate is a downstream product made fromTrona– It is the same baking soda you add to food– It is a purified processed productmade from soda ash, so it ismore expensive– But is much more reactive with SO2zBicarbonate has to be milled prior to use– Milling on site to d90 less than 20microns with direct injectiongives the best results– Premilled material with a D90 less than 40 microns is available– Handling issues become severe as d90 approaches 20 microns.zNew capacity for sodium bicarbonate– A new process that skips the soda ash step makes a moreeconomical Flue Gas grade.56Advantages of Sodium DSIzDry Sorbent Injection systems are the lowest capital costoption to treat acid gases.– Small utilities and industrial boilers can’t afford wet scrubberszSodium DSI is compatible with ESP particulate control– Even with higher loading, sodiumsalts reduce ash resistivity andusually lower opacity and particulate emissions.zSodium DSI is also effective on HCl and HFzRemoval rates can adapt to changing conditions byadjusting the feed rate.– Fuel changes, load changes, regulation changes7Trona compared to LimezTrona is more efficient than lime so less material isneededzTrona is easier to handleand less prone to pluggingzTrona enhances ESP performancezTrona can be added further upstream, even ahead of theeconomizerzLime is less expensive per ton on a delivered basis– Delivered trona costs are highly freight dependantzLime is more compatible with beneficial use of fly ash– Sodium levels in the ash ofless than 1.5% are typicallyacceptable8What we mean by NSRzNormalized Stoichiometric Ratio– MW trona is 226 MW SO2is 64 MW SO3 is 80–2 moles trona for every 3 moles SO2 or 452/192 = 2.35–2 moles trona for every 3 moles SO3 or 452/240 =1.88– MW bicarbonate is 84–2 moles bicarbonate for every mole of SO2 or 168/64 = 2.62–To fully calculate the amount of sorbent for an NSR of 1, all acidgasses must be accounted for. For trona, figure 97.5% purity.9Trona Performance Curve10Sodium BicarbonatePerformance Curve11Comparison of SO2 Treatment Rates withTrona and Sodium Bicarbonate (SBC)01020304050607080901000.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0NSR

SO 2 Removal Rate (%)Trona 2006Trona 2007SBC• The 2006 data was obtained during a test using a temporary set up.• The 2007 data was generated from a permanent installation• Unmilled trona Select 200: d90= 140 μm, d50= 30 μm12Should You Use Trona or SodiumBicarbonatezSodium bicarbonate becomes more economical to use than trona as thefollowing situations exist– An ESP is the particulate control device– Higher SO2removals are required– Injection is after the air heater• Bicarbonate needs less than 800oF• Trona efficiency increases as temperature and residence timeincrease– On site milling is available– Freight costs are high– Fly ash disposal costs are highzUse of sodium sorbents results in highersodium content in the fly ash. Thecustomers should check the fly ash properties for beneficial applications ordisposal.13Effect of Sodium Bicarbonate Particle SizeEffect of SBC Particle Size at Same SO2Removal Rate01000200030004000500060007000800010 20 30 40 50 60 70SBC Particle Size d90(micron)

SBC Feedrate (lb/h)* Outlet SO2concentration @ 0.3 lb/mmBTU for all tests14Fly Ash ConsiderationszHigher sodium content in the fly ash.zAshes from SO2treatment typically not suitablefor applications in concrete or structural fillzSolubility of sodium compounds in the fly ash(i.e. Na2SO4, Na2CO3)zDisposal issues should be investigated early inthe process. Customers encouraged to checkproperties and work closely with their fly ashmarketers.15Other BenefitszHigh removal efficiencies for HCl and HFzMercury removal is enhanced at locations thathave high sulfur coalzSelenium and arsenic are also removed from theflue gas.16Contact the SOLVAir Group ofSolvay ChemicalszBusiness Manager–Mike.Wood@solvay.comzSales–Michael.Atwell@solvay.com–Stan.Carpenter@solvay.comzTechnical–Yougen.Kong@solvay.com–Heidi.Davidson@solvay.com