Estimates of the Chemical form of fluorine in Steel Slag by the

application of saturated column test

Environmental Risk Analysis,

Kyoto University

Kengo NAKAMURA, Minoru YONEDA

1

Steel Slag as Recycled Materials

2

Back Ground

Oxidation Slag：70kg/t Reduction Slag：40kg/t

Recycled Materials ・Building material (Ex. Base course material)

・Cement raw material (Ex. Aggregate)

Fluorine regulated environmental standards in Japan

CaF2 Benefit: low temperature = low cost = Save energy

Environmental Standards Relating to use Steel Slag

Designated standard

Leachate Standard (㎎/L) Concentration Standard (㎎/kg)

0.8 4000

3

Back Ground

Fluorine Environmental Standards

WHO : 1.5Fmg/L Ex. Sea : 1.3~1.7Fmg/L

The standard of fluorine addition will become trade between

the reduction of energy consumption and human health risk.

More Strict

Purpose in this study

• To determined chemical form of the fluorine that influenced or indicate the solubility of fluorine component by.

4

Purpose

The method of estimate fluorine compounds is saturation column test

1. Dissolution fluorine trend from steel slag is reproduced through column test

2. PHREEQC fluorine compound is determined by comparing PHREEQC database

Sample (Oxidation slag, Reduction slag)

Oxidation slag Reduction slag O 36.09 O 46.85 Fe 18.81 Ca 29.75 Ca 15.59 Si 8.71 Si 8.69 Al 5.25 Al 6.73 Mg 3.84 Mn 5.29 C 2.55 Mg 3.15 S 0.71 C 1.32 Mn 0.27

Na 0.38 Fe 0.26

Ti 0.29 Ti 0.20 F 0.40 F 1.17

others 3.26 others 0.44

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Method

It is composed mainly of solid phase described above, quantities evaluation of solid phase in steelmaking slag has

not been achieved.

Saturation Column Test

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Method

Inflow

Outflow

Filter

Sample

Acryl Column

• The saturation column test is a method to estimate short term behavior of dissolution of element in solid recycled materials.

Condition

The final condition of column test will be achieved if the composition of Liquid (Solvent in liter) : solid (steel slag in kg) = 10 :1

Oxidation slag Reducing slag

Column height（cm） 30

Column bore（cm） 5

Solvent Ultra pure water Flow rate（mL/min） 19.6

Fill ration(g) 1264.39 699.96 Water content

rate（%） 0.06 2.8

Fill ration （Dry）（g） 1263.63 680.38

Density（g/ml） 3.96 3.2

Filling amount (Dry)（ml） 319.1 212.62

Porosity（%） 45.83 63.9

Results of Column Test Decrease of dissolution fluorine compounds, fluorine phase is transformed from high solubility phase to low solubility phase.

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Result

Oxidation Slag

Reduction Slag

Fluorine compounds are possible that it is seen not change due to the migration of solubility by water flow.

F Concentration : 3.6mg/L pH:10.4

F Concentration : 0.2mg/L pH:10.4

F Concentration : 2.2mg/L pH:11.6

F Concentration : 0.6mg/L pH:11.5

Chemical Equilibrium Model PHREEQC • Geosphere transition model PHREEQC is used to

calculate an ionic transfer as surface of aqueous and solid phase. Inorganic thermodynamic model in PHREEQC has been taken into account solid phase in the transition between the dissolution as well as an action of ion.

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Result

Example

Dissolution of the mineral fluorine(CaF2) CaF2 ↔ Ca2+ + 2F－

At equilibrium the aqueous concentrations obey the solubility product: Kfluorite = [Ca2+][F-]2 = 10-10.57 at 25℃ Relation can be rewritten in logarithmic form as: logKfluorite = log[Ca2+] + log[F-]2 = -10.57

Fluorine Components Name Reaction logK deltaH(kJ)

AlF3 AlF3 = Al+3 + 3F- -17.21 -34.04

Fluorite(CaF2) CaF2 = Ca+2 + 2F- -10.04 12.13

FeF2 FeF2 = 2F- + Fe+2 -2.38 -51.69 FeF3 FeF3 = 3F- + Fe+3 -19.24 -13.81

Sellaite(MgF2) MgF2 = 2F- + Mg+2 -9.38 -12.46

NaF NaF = Na+ + F- -0.021 -569

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Result

Fluorine component on the surface of steel slag

Calculation condition

Fluorine compounds are presented 0.1mol/kg and reappearance dissolution fluorine concentration on water 1L (density of water: 1g/cm3)

Relationship pH and pe of fluorine

compounds are created using PHREEQC

≡ 𝐴𝑙𝐹3 → 𝐴𝑙3+ + 3𝐹−

≡ 𝑁𝑎𝐹 → 𝑁𝑎+ + 𝐹−

≡ 𝑀𝑔𝐹2 → 𝐹𝑒2+ + 2𝐹−

≡ 𝐹𝑒𝐹3 → 𝐹𝑒3+ + 3𝐹−

≡ 𝐹𝑒𝐹2 → 𝐹𝑒2+ + 2𝐹−

≡ 𝐶𝑎𝐹2 → 𝐶𝑎2+ + 2𝐹−

Chemical Property of Fluorine Components

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Result

pH dependence pe dependence

CaF2, MgF2, FeF3 are showed pH dependence.

Fluorine compounds are not showed pe dependence except

FeF3.

In order to reproduce the fluorine trend in the column test, solvent conditions are used to measure the value of pH which was obtained from column test and chemical equilibrium computation.

Estimate of fluorine in steel slag by PHREEQC for calculating fluorine compounds

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Result

Parameter of column test are set at the same condition with PHREEQC (flowing amount water, water flow time, column height, sample density)

Each fluorine compound was calculated in each column. Fluorine compounds are assumed to present each fluorine compounds 100% in column

Oxidation Slag

Reduction Slag

AlF3, CaF2, FeF2, FeF3, MgF2, NaF (6 column)

AlF3, CaF2, MgF2 (3 column)

It is assumed that liquid solution condition is used same pH parameter of column test

(Oxidation slag: max pH10.4, Reduction slag: max pH11.8)

Estimate fluorine in steel slag by PHREEQC

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Result

Oxidation Slag

Reduction Slag

Conclusion

• Base on column test it can be conclude that fluorine concentration is high in initial condition which was rate of liquid : solid is 1 :1.

• In addition, from PHREQCE simulation (the relationship between dissolution concentration and fluorine dissolution rate) , it suggest that fluorine chemical compounds of oxidation slag are ALF3 and NaF .

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Conclusion

Oxidation Slag

Reduction Slag

• The decreased of fluorine concentration in reduction slag was lower compare with the decreased of fluorine concentration in oxidation slag.

• From PHREEQC simulation it can be showed that the chemical compound of fluorine in reduction slag is AlF3.

Thank you for your attention.

14

15

Result

鉄鋼スラグ Iron slag

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生産量と利用量：Amount of production & utilization

17

14107 13722

12168 1230212916

13427 1386514400

347 385 361 374 392317 342

452

0

200

400

600

800

1000

1200

1400

1600

1800

2000

0

2000

4000

6000

8000

10000

12000

14000

16000

2000 2001 2002 2003 2004 2005 2006 2007

(t)

(t)

year

amount of production (Right) amount of recycle (Left)

Final waste disposal amount of accessory product Produce and recycle amount of steel slag *left: produce amount arbor right: recycle amount arbor

再使用

17,3%

道路

29,5%

地盤改

良材

5,2%

土木 35,6%

セメント

4,4%

ｺﾝｸﾘｰﾄ

骨材

0,3%

加工用

原料

2,4%

他利用

3,0% 埋立等

2,3%

製鋼スラグ

再使用

21,0%

道路

27,1%

地盤改良

材

5,5%

土木

37,3%

セメント

5,2%

ｺﾝｸﾘｰﾄ骨

材

0,0%

加工用原

料 0,3%

他利用

2,8% 埋立等

0,8%

転炉スラグ

再使用

1,6%

道路

39,4%

地盤改

良材

3,9%

土木

28,5%

セメント

1,0%

ｺﾝｸﾘｰﾄ

骨材

1,3%

加工用

原料

11,5%

他利用

4,0%

埋立等

8,8%

電気炉スラグ

Saturation Column Test

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Method

Oxidation

slag Reducing slag

Colume

height（cm） 30

Colume bore

（cm） 5

Solvent Ultra pure water Flow rate

（mL/min） 19.6

Fill ration(g) 1264.39 699.96 Water content

rate（%） 0.06 2.8

Fill ration

（Dry）（g） 1263.63 680.38

Density

（g/ml） 3.96 3.2

Filling

amount (Dry)（ml）

319.1 212.62

Porosity（%） 45.83 63.9