Successful Mitigation of SO3 By Employing Dry Sorbent Injection of Trona Upstream of the ESP John Maziuk Solvay Chemicals Background: SO3 Plume z Fine aerosols scatter light z Low concentrations (10 ppm) visible as blue secondary plume z Does not disperse readily, touch down risk z Plume appearance depends on z Weather: sunny, clouds, rain, etc. z Time of day, angle of sun z Visible to the Public Solvay Chemicals, Inc. Copyright 2005, Solvay America, Inc. Background – Plume Problem z SCR Additions to Control NOx Emissions resulted in unintended increase in SO3 generation. z High Sulfur Coal, along with SCRs resulted in a highly visible secondary plume. Solvay Chemicals, Inc. Copyright 2005, Solvay America, Inc. Background – SO3 Sources z SO3 Generation in Steam Generator: 0.1 to 1.5% z z Oxidation of sulfur during combustion Catalytic oxidation of SO2 by corrosion products z SO3 Generation in SCR z z Catalytic oxidation of SO2 to SO3 z Low conversion catalyst: design conversion 1.3% z Regular conversion catalyst: design conversion up to 3% Function of inlet SO2 concentration, catalyst material, and operating temperature Solvay Chemicals, Inc. Copyright 2005, Solvay America, Inc. SO3 Formation Fe2O3 Catalytic Oxidation of SO2 to SO3 Coal Ash 60 SO2 Oxidized % 50 40 30 20 10 0 200 300 400 500 600 700 800 900 1000 1100 1200 Temperature C Solvay Chemicals, Inc. Copyright 2005, Solvay America, Inc. What is Trona? z Trona is a ore that is mined underground z Trona is naturally formed sodium sesquicarbonate z Na2CO3• NaHCO3• 2H2O z Green River formation z Numerous beds of Trona z Contain billions of tons of Trona Solvay Chemicals, Inc. Copyright 2005, Solvay America, Inc. Solvay Minerals Operations z Solvay Minerals, Inc. Currently Mines Trona Ore at an Approximate Depth of 1500’ (457m) z 12’ (3.67m) Thick and of Very High Quality z Provide Ore for Many Years z Use Both Longwall Mining and Bore Miners Solvay Chemicals, Inc. Copyright 2005, Solvay America, Inc. Room and Pillar Mining Solvay Chemicals, Inc. Copyright 2005, Solvay America, Inc. The Surface Plant Solvay Chemicals, Inc. Copyright 2005, Solvay America, Inc. Trona Dry Sorbent Injection (DSI) z “Popcorn Effect” z ...5 to 20 times the original surface area z 2(Na2CO3• NaHCO3• 2H2O) → 3Na2 CO3 + CO2 + 5H2O Solvay Chemicals, Inc. Copyright 2005, Solvay America, Inc. Trona SEM After Calcination Solvay Chemicals, Inc. Copyright 2005, Solvay America, Inc. Trona DSI Chemistry Na2CO3• NaHCO3• 2H2O +3HCl →3NaCl +4H2O + 2 CO2 2(Na2CO3• NaHCO3 • 2H2O) + 3SO2 →3Na2SO3 + 4 CO2 + 5H2O 3Na2SO3 + 1.5O2 →3Na2SO4 Solvay Chemicals, Inc. Copyright 2005, Solvay America, Inc. Parameters Constraints That Affect Sorbent Utilization: z Sorbent Injection Rate z NSR (Normalized Stoichiometric Ratio) z Sorbent Particle Size z Sorbent Residence Time In The Flue Gas Stream z Sorbent Penetration And Mixing Within The Flue Gas z Particulate Control Device Used z Other Acids Solvay Chemicals, Inc. Copyright 2005, Solvay America, Inc. Impact of Particle Size on T200 Performance @325oF Effect of Sorbent Size @ NSR 1 Source: Solvay Chemicals %SO2 Removal 100 80 60 40 20 0 11 14 32 65 93 microns Solvay Chemicals, Inc. Copyright 2005, Solvay America, Inc. Sodium SO3 Reactions z 2 (Na2CO3·NaHCO3·2H2O) + heat Æ 3 Na2CO3 + CO2 + 5 H2O z Na2CO3 + SO3 Æ Na2SO4 + CO2 z Na2CO3 + H2O +2SO3 Æ 2NaHSO4 + CO2 z NaHCO3 + SO3 Æ NaHSO4 + SO3 z Na2SO4 + H2SO4 Æ 2NaHSO4 z 2NaHSO4 Æ Na2S2O7 Solvay Chemicals, Inc. Copyright 2005, Solvay America, Inc. Sodium SO3 Reactions (continued) 1.0E+06 Na2S2O7 (l) (H2SO4 + SO3) ppm 1.0E+05 1.0E+04 NaHSO4 (s) Na2S2O7 (s) NaHSO4 (l) 1.0E+03 1.0E+02 Na2SO4 (s) 1.0E+01 1.0E+00 100 150 200 250 300 350 400 450 500 T (C) Solvay Chemicals, Inc. Copyright 2005, Solvay America, Inc. Initial Trial Data with T200 DSI % SO3 Reduction Measured at ESP Outlet. Figure 4: Gavin U-2, SO3 Reduction with Dry Trona Injection Testing 100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0% SCR O/S SCR I/S 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 Moles Sorbent : Moles SO3 Solvay Chemicals, Inc. Copyright 2005, Solvay America, Inc. Cold Side ESP Performance Data Figure 5: Gavin U-2, 2003 ESP Total Current Density vs. Trona Injection Levels Current Density, mA/ 1000 Sq. Ft . 35 30 25 20 Lower Boxes Upper Boxes All Boxes 15 10 5 0 0 0.5 1 1.5 2 2.5 3 DSI, TPH Solvay Chemicals, Inc. Copyright 2005, Solvay America, Inc. Trona Injection Location S T A C K SCR Trona By-Pass Damper Air Heater Furnace Solvay Chemicals, Inc. ESP FGD Copyright 2005, Solvay America, Inc. Hot Side ESP Experience @ 800 ppm SOx SO2 Removal SO2 Removal w/ T200 @ 1.5 NSR 100% 95% 90% 85% 80% 75% 70% 65% 60% 55% 50% 680 Solvay Chemicals, Inc. 700 720 740 760 Temperature F 780 800 820 Copyright 2005, Solvay America, Inc. ESP Perf Plates Using Sodium Bicarbonate >700oF Solvay Chemicals, Inc. Copyright 2005, Solvay America, Inc. Perf Plate Before Hot Side of ESP in Previous Slide After Two Weeks of T200 DSI and still “clean as a whistle” Solvay Chemicals, Inc. Copyright 2005, Solvay America, Inc. Typical T200 DSI Loading/Storage System Solvay Chemicals, Inc. Copyright 2005, Solvay America, Inc. Proven SO3 Mitigation Systems Trona Injection At ESP Inlet: z z z z z Alone Is Sufficient For SO3 Mitigation, No Visible Plume Enhances ESP Performance Capital Costs About The Same As Hydrated Lime Operating Costs Less Than Lime No ESP Operational Problems As With Lime Solvay Chemicals, Inc. Copyright 2005, Solvay America, Inc. The End Solvay Chemicals, Inc. Copyright 2005, Solvay America, Inc.
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