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The Removal of Sodium from Low-Rank Coals. CAMP. CAST. Enhancement of Montana Coal- Sodium Removal Technology Evaluation and Development. Co-Authors. Jay McCloskey. Beverly Plumb. Larry Twidwell. Sean Dudley. SPONSORS. Great Northern Properties (GNP).

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Presentation Transcript
slide2

Enhancement of Montana Coal-

Sodium Removal Technology

Evaluation and Development

Co-Authors

Jay McCloskey

Beverly Plumb

Larry Twidwell

Sean Dudley

slide3

SPONSORS

  • Great Northern Properties (GNP)
  • The US Department of Energy (DOE) Center for Advanced Separation Technologies (CAST)
slide4

SPONSORS

  • Center for Advanced Mineral and Metallurgical Processing (CAMP) and the Metallurgy/Materials Engineering Department.
  • Montana Board of Research and Commercialization Technology (MBRCT)
slide5

PROJECT OBJECTIVES

  • Evaluatesodium removal technologies and sodium recovery from solutionsfor low-rank Montana coals
slide6

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.
slide7

BACKGROUND

  • A major factor is the relatively high sodium content which may cause slagging in some power plant boilers
slide8

THREE PROJECTS

  • Coal Leaching
  • Recovery of sodium and anions from leach solutions
  • Anionic leaching and solution treatments
slide9

PRESENT PROJECT

  • Coal Leaching
  • Literature Review
  • Modeling
  • Preliminary Test Work
  • Experimental Design, Optimization Test Work
slide10

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
slide11

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

slide12

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

slide13

LITERATURE REVIEW

Occurrenceof Inorganic Constituents in Low-Rank Coals

Na/K salts

Carbon Structural Compounds

Oxy-hydroxyl polymeric complexes (least prevalent)

slide14

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

slide15

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.

slide16

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

slide17

COAL CHARACTERIZATION

Samples from four coal companies

slide19

Albite (major in Coal B)

Na silicate (Liq) present

Albite solid has dramatically decreased

slide20

COAL CHARACTERIZATION

Na same for all size fractions from 2 mm to 38 µm

slide23

STABCAL MODELING

Content in Mineral Phase for Coal B

To completely dissolve the sodium minerals

Our benchscale study range

slide24

PRELIMINARY LEACH RESULTS

Soluble salts

Soluble salts/H+ exchangeable ions

Soluble salts/H+ and Ca++ exchangeable ions

10 g coal/100mL

slide26

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

slide27

RESPONSE SURFACE DESIGN MATRIX

Response Surface Design Best for Selecting Optimum Treatment Conditions

slide29

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

slide30

Response Surface Results

Influence of Time and pH

Time, hrs

~35%

pH 3, 1 hr

No ion exchange reagent, HCL acid

slide31

Response Surface Results

Influence of CaCl2 and pH at 1 hr

g/L CaCl2

pH

slide32

Response Surface Results-ACIDS

H2SO4

HCl

hrs

Constants: 0 g/L CaCl2

slide33

Response Surface Results-Metals

Al Leached, HCl,

0 g/L CaCl2

Fe Leached, HCl,

0 g/L CaCl2

slide34

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

slide35

Conditions in green area achieves >40% Na Removal

Time, hrs

Optimization

No IX reagent, HCL acid

slide36

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

slide37

SUMMARY AND THOUGHTS

  • Sodium removal is from maceral phase for mild acid leaching conditions
  • In agreement with other literature studies
slide38

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
slide39

SUMMARY AND THOUGHTS

  • Evaluate where and how the leachate could be introduced into the coal treatment system

Mineral processing group at CAMP

slide40

THE END!

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

slide41

ACKNOWLEDGEMENTS

  • Special acknowledgement and thanks to CAMP, CAST, MBRTC, and GNP for supporting this work.
slide42

QUESTIONS AND COMMENTS

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slide43

Thanks for your attention!!

Montana Tech of the University of Montana

Website: WWW.MTECH.EDU