The Removal of Sodium from Low-Rank Coals

1. The Removal of Sodium from Low-Rank Coals CAMP CAST

2. Enhancement of Montana Coal- Sodium Removal Technology Evaluation and Development Co-Authors Jay McCloskey Beverly Plumb Larry Twidwell Sean Dudley

3. SPONSORS • Great Northern Properties (GNP) • The US Department of Energy (DOE) Center for Advanced Separation Technologies (CAST)

4. SPONSORS • Center for Advanced Mineral and Metallurgical Processing (CAMP) and the Metallurgy/Materials Engineering Department. • Montana Board of Research and Commercialization Technology (MBRCT)

5. PROJECT OBJECTIVES • Evaluatesodium removal technologies and sodium recovery from solutionsfor low-rank Montana coals

6. BACKGROUND • Montana ranks only 6th among the states in coal production. • Montana has approximately 120 billion tons of coal reserves, more than any other state in the U.S.

7. BACKGROUND • A major factor is the relatively high sodium content which may cause slagging in some power plant boilers

8. THREE PROJECTS • Coal Leaching • Recovery of sodium and anions from leach solutions • Anionic leaching and solution treatments

9. PRESENT PROJECT • Coal Leaching • Literature Review • Modeling • Preliminary Test Work • Experimental Design, Optimization Test Work

10. LITERATURE REVIEW Extensive literature search • Usual treatment approaches for the removal of sodium from low-rank coal. • Review includes • Specific review papers • List of searchable data bases • Specific characterization data for low-rank coals

11. Today’s topic LITERATURE REVIEW • Technologies • Two major technological approaches have been studied • Addition of compounds or mineral phasesto react with the sodium during the combustion process to form compounds that are less prone to form molten liquids. Solution leaching of coals for sodiumremoval

12. LITERATURE REVIEW Occurrenceof Inorganic Constituents in Low-Rank Coals Maceral Matter Cations of Na, K, Ca, Mg, Fe in the organic fraction (prevalent) Mineral Phases Minerals, clays, dirt (prevalent) Pore Moisture Dissolved chlorides or sulfates

13. LITERATURE REVIEW Occurrenceof Inorganic Constituents in Low-Rank Coals Na/K salts Carbon Structural Compounds Oxy-hydroxyl polymeric complexes (least prevalent)

14. General Low-Rank Coal Upgrading Techniques Hydrocyclones, Flotation, Heavy Media Separation, and Centrifugal Washing. Some low-rank Western coals respond well to washing techniques for removal of discrete mineral phases

15. General Low-Rank Coal Upgrading Techniques Many studies have reported up to70% sodium removal at pHs of 5-6.5. Treated waters contain 3-6 g/L dissolved organics and high sodium levels so waters have to be cleaned.

16. General Low-Rank Coal Upgrading Techniques Not effective for minerals Conc acid, caustic, elevated temp Technique to remove ash forming elements. Inorganic acids, ammonium acetate, calcium chloride, aluminum lactate. “Clean Coal” Inorganic acids, formic, acetic, pHs 3 to 6

17. COAL CHARACTERIZATION Samples from four coal companies

18. COAL CHARACTERIZATION Note

19. Albite (major in Coal B) Na silicate (Liq) present Albite solid has dramatically decreased

20. COAL CHARACTERIZATION Na same for all size fractions from 2 mm to 38 µm

21. COAL CHARACTERIZATION

22. MODELING

23. STABCAL MODELING Content in Mineral Phase for Coal B To completely dissolve the sodium minerals Our benchscale study range

24. PRELIMINARY LEACH RESULTS Soluble salts Soluble salts/H+ exchangeable ions Soluble salts/H+ and Ca++ exchangeable ions 10 g coal/100mL

25. 10 g coal/100mL, 20 g/L CaCl2

26. OPTIMIZED LEACH • An experimental design study was conducted to investigateimportance of four variables and to select optimum conditions for removal of sodium. • pH (0.2, 6.0) • Type Acid (HCl, H2SO4) • Type Reagent (CaCl2, NH4Acetate) • Concentration of Reagent (0 and 20 g/L) Constants: 10 g coal B fines/100 mL, ambient temp, 30 minute water preleach

27. RESPONSE SURFACE DESIGN MATRIX Response Surface Design Best for Selecting Optimum Treatment Conditions

28. RESPONSE SURFACE TWO-LEVEL DESIGN STUDY RESULTS STATEASE DESIGN EXPERT SOFTWARE

29. Response Surface Results Initial Coal: 7.7% Na2O in ash Na2O in ash = 2.8% pH 3, 1 hr Na2O in ash = 4.6% No ion exchange reagent, HCL acid

30. Response Surface Results Influence of Time and pH Time, hrs ~35% pH 3, 1 hr No ion exchange reagent, HCL acid

31. Response Surface Results Influence of CaCl2 and pH at 1 hr g/L CaCl2 pH

32. Response Surface Results-ACIDS H2SO4 HCl hrs Constants: 0 g/L CaCl2

33. Response Surface Results-Metals Al Leached, HCl, 0 g/L CaCl2 Fe Leached, HCl, 0 g/L CaCl2

34. SUMMARY AND THOUGHTS • Good extraction occurs using moderate acidic conditions (30 to 40%) In general HCl better than H2SO4 In general ion exchange reagents not needed

35. Conditions in green area achieves >40% Na Removal Time, hrs Optimization No IX reagent, HCL acid

36. Conditions to Remove 35% of the Na 2.0 1.6 [Na], mg/L: 369 Na2O in Ash, 4.7 Na Removed, 35 Na Removed, %: 35 1.3 [Al], %: 2.9 [Fe], %: 3.6 0.9 0.5 0.2 1.7 3.1 4.6 6.0 A: pH

37. SUMMARY AND THOUGHTS • Sodium removal is from maceral phase for mild acid leaching conditions • In agreement with other literature studies

38. SUMMARY AND THOUGHTS • Water cleanup required because of relatively high sodium and chloride content. • Further work will include multiple coal/solution contacts to determine influence of sodium and anion buildup in the solution

39. SUMMARY AND THOUGHTS • Evaluate where and how the leachate could be introduced into the coal treatment system Mineral processing group at CAMP

40. THE END! If you would like a copy of this powerpoint presentation: Ltwidwell@mtech.edu

41. ACKNOWLEDGEMENTS • Special acknowledgement and thanks to CAMP, CAST, MBRTC, and GNP for supporting this work.

42. QUESTIONS AND COMMENTS ?? ??? ? ? ? ? ??? ? ?? ???? ? ?? ? ? ? ?? ? ?? ? ? ?

43. Thanks for your attention!! Montana Tech of the University of Montana Website: WWW.MTECH.EDU