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Measurement of the Oxygen Potential of Non-Ferrous Slags with an Ex-Situ Electrochemical Device
N. Moelans1, B. Coletti1, J. Plessers2, M. Straetemans2, B. Blanpain1, P. Wollants1
1Department

of Metallurgy and Materials Engineering, Katholieke Universiteit Leuven, Kasteelpark Arenberg 44, B-3001 Leuven, Belgium 2 Heraeus Electro-Nite Int. N.V. , Centrum Zuid 1105, B-3530 Houthalen, Belgium

Contents
• Introduction • Experimental procedure
– Measurement – Materials – Calculations

• Results and discussion • Conclusion

Introduction : importance of pO2
• Affects reactivity with
• Metal • Matte • Lining of reactor

• Available devices
• In-situ: CeloxTM, Celox-SLACTM • Ex-situ: Ferro-ActisTM, RAPIDOXTM

Experimental procedure: measurement
• Electrochemical cell
Ni / NiO // ZrO2(MgO) // slag / Ir
• Reference electrode : – Ni/NiO (1050 0C-1400 0C) – Mo/MoO (1400 0C -1650 0C) • Bath electrode : – Iridium conductor partially covered by silica • Solid electrolyte : – MgO stabilized ZrO2
Ni O2e-

V

ZrO2

Ir

NiO

M/MO

Experimental procedure: measurement
• Formulas
– Nernst’s law :

RT pO2 ( slag ) ln EMF = nF pO2 ( ref )

– For a Ni/NiO reference :

log pO2

( )

20.171* EMF − 24,420 = + 8.88 T pO2(bar), EMF (mV), T (K)

Experimental procedure: measurement
• RAPIDOX Sensor

Experimental procedure: measurement
• Atmosphere
• Nitrogen (99.8 %) (N2) • Nitrogen + 5% hydrogen (N2+5%H2) • Nitrogen + thin layer (30-40 g) carbon black fine cokes (N2+C)

• Rotating crucible + eccentrically placed sensor
• Limitation of polarisation • Homogenisation of melt

Experimental procedure: measurement
1400

Melt
1200

Measurement

Sensor out

Temperature (°C)

1000 800 600 400 200

Measurement Sensor in

Gas closed Cool down

Heating

Gas in
0 0 50 100 150 200 250 300 350 400 450

Time (min)

Experimental procedure: materials
Pb
Slag 1 Slag 2 Slag 3 Slag 4 Slag 5 2.5