Neutralization of Acid Mine Drainage Using Stabilized Flue Gas Desulfurization Material

Transcription

1 Neutralization of Acid Mine Drainage Using Stabilized Flue Gas Desulfurization Material W. Wolfe 1, C.-M. Cheng 1, R. Baker 1, T. Butalia 1, J. Massey-Norton 2 1 The Ohio State University, 2 American Electric Power

2 Stingy Run Fly Ash Impoundment

3 Reclamation of Fly Ash Impoundment

4 Highwalls and Pits in Stingy Run Impoundment

5 Sources of AMD into Stingy Run AMD Weir #4 North Pond AMD Weir #3 AMD Weir #1 AMD Weir #2 South Pond Weir # ph 4 OGS- UGMs GA-031, GA Weir #1 Weir #2 Weir #3 Weir #4 North Pond South Pond Location

6 Reclaiming using Fixated FGD Material Utilizing large volume of fixated flue gas desulfurization materials FGD by-product (calcium sulfite) stabilized with fly ash and lime Goals Encapsulate acid mine drainage (AMD) producing materials Neutralize AMD Re-contour highwalls Approaches Year I: field investigation; laboratory test; bench-scale study; numerical analysis of design approaches; background water monitoring Year II and III: permitting, water quality monitoring, construction of the demonstration project

7 Full-scale Demonstration N MW ft 3000 ft Drainage-way for AMD Discharge during Excavation 2000 ft Proposed Road Entrance from Plant 1000 ft Proposed Pomeroy Monitoring Well Sites MW Start Point Proposed Deep Monitoring Well Site Scale: Approximate Highwall Location 1000 ft Approximate Measurement of Distance

8 Establishing Background Groundwater Quality

9 Groundwater Quality Monitoring

10 Establishing Background Surface Water Quality

11 Surface Water Quality Monitoring

12 Bench Scale Testing 1 4 ~2.5 tons

13 Bench Scale Testing Assessment of FGD saturation with tap and AMD waters in the absence and presence of geo-composite intrusion Optimizing geo-composite placement design to maximize contact between AMD and stabilized FGD material Monitoring change of water quality as tap/amd water percolates through the FGD mass under different hydraulic heads AMD was transported to the lab the day before each batch of test and continuously purged with nitrogen gas to prevent oxidation and carbonation

14 Bench Scale Testing

15 12 Change of AMD ph after Contacting Fixated FGD Material ph LL1 LL2 LL3 Outlet Hydraulic Head AMD ph Hydraulic Head, ft Accumulative testing time, minutes

16 Change of AMD ph after Contacting Fixated FGD Material at Different L/S ratio ph 8 6 LL1 LL2 LL3 Outlet 4 AMD ph= L/S Ratio

17 Mineral Composition of Gavin Fixated FGD Material Hannebachite (CaSO H 2 O) Portlandite (Ca(OH) 3 ) Hematite (Fe 2 O 3 ) Magnetite (Fe 3 O4 ) Quartz (SiO 2 ) Mullite (3Al 2 O 3 2SiO 2 ) Maghemite (Fe 2 O 3 ) Ettringite (Ca 6 Al 2 (SO 4 ) 3 (OH) 12 26H 2 O)

18 Chemical Reactions between AMD and Fixated FGD Material Neutralization of AMD Portlandite + 2+ Ca( OH ) 2 + 2H Ca + 2H 2O Ettringite C Al (SO ) (OH) 26H O + 12H Al + 6Ca + 3SO + 38H Iron oxides + 3+ Fe2O3 + 6 H 2Fe + 6H 2O Fe O + 8 H 2Fe + Fe + H 2O Carbonates 2 O Fixated FGD (g)/ AMD (L) Formation of potential secondary minerals Iron hydroxides, Chrysotile (Mg 3 Si 2 O 5 ), diaspore (AlHO 2 ), bixbyite (Mn 2 O 3 ), barite (BaSO 4 )

19 Neutralization Capacity Estimated by Geochemical Modeling % Lime 4.7% Lime geochemical model 10 ph AMD Gallon AMD/Pound Fixated FGD

20 Laboratory Column Testing Simulating AMD neutralization process under similar percolation process as reclamation Two columns with different L/S flow rates Column I: ~1.0 L/S per day Column II: ~2.0 L/S per day Monitoring change of AMD water quality with extended L/S ratio Column I: ~74 (9 gallons AMD/lb fixated FGD) Column II: ~147 (17 gallons AMD/lb fixated FGD)

21 Change of AMD ph after Contacting Fixated FGD Material in Flow Through Column Test Column I Column II 9.0 ph delay depletion of portlandite/enttringite /24/14 7/1/14 7/8/14 7/15/14 7/22/14 7/29/14 8/5/14 8/12/14 8/19/14 8/26/14 9/2/14 Date/Time

22 Change of AMD ph after Contacting Fixated FGD Material in Flow Through Column Test as a Function of L/S Ratio Column I Column II Column I inlet Column II inlet ph ph at inlet L/S Ratio Gallon of AMD/pound of Fixated FGD

23 Change of Sulfate in AMD Column I Column II Column I inlet Column II inlet Sulfate, mg/l Independent of flow rate due to change of AMD chemical property L/S Ratio

24 Constituents with Elevated Levels Normalized Concentration (C i /C AMD ) Column I Column II Bench Scale Outlet 0.1 K B Mo Sr Sulfate Ca Ba V ph Constituent

25 Elements with Decreased Concentration 10 Normalized Concentration (Ci i /C AMD ) Column I Column II Bench Scale Outlet Cr Cd Si Co Zn Ni Al Mn Fe Constituent

26 Elements Showing First Flush Phenomenon Normalized Concentration (Ci i /C AMD ) Column I Column II Bench Scale Outlet 0.01 Na Cl Hg Sb Tl Se As Cu Be Pb Constituent

27 Summary Mitigating AMD using fixated FGD material Re-contour unreclaimed highwalls and highwall pits Based on laboratory leaching study and geochemical model, one pound of Gavin fixated FGD material is able to neutralize approximately 20 gallons of AMD (~160 L/S) Change of AMD water quality Based on available data from column and bench-scale tests Constituents with elevated concentrations ph, sulfate, Ca, K, B, Mo, Ba, Sr, and V Elements with decreased concentrations Fe, Mn, Zn, Cd, Co, Cr, Ni, Si, and Al Elements with first flash phenomenon Na, Cl, Hg, Sb, As, Cu, Se, Tl, Li, and Pb

28 Future Works Laboratory column test Examining the environmental response beyond the neutralization capacity of the fixated FGD material Geochemical kinetic model Bench-scale reclamation module Optimizing placement of geocomposite drainage layer and fixated FGD material in the reclamation design Establishing AMD flow model Finalizing reclamation design

29 Full-scale demonstration Future Works Continuing on water quality monitoring Carrying out statistical and hydrogeochemical analyses of background water quality data Permit application Project site preparation/construction Backfilling of fixated FGD material Post reclamation water monitoring

30 First Flush of Arsenic Arsenic, mg/l Column 1 Column 2 Inlets (under detection limt) Bench Scale LL1 Bench Scale LL2 Bench Scale LL3 Bench Scale Outlet L/S Ratio

31 First Flush of Mercury 50 Mercury, ng/l Column 1 Column 2 L/S ratio_full vs Hg L/S ratio Half vs Hg Bench Scale LL1 Bench Scale LL2 Bench Scale LL3 Bench Scale Outlet L/S Ratio