ENCYCLOPÉDIE DE LA RECHERCHE SUR L’ALUMINIUM AU QUÉBEC 2013 | Page 25
PRODUCTION DE L’ALUMINIUM
Pondération de la réaction chimique et du
ALUMINIUM PRODUCTION
transport de masse sur la réactivité
anodique au CO2 à 960OLA RÉACTION CHIMIQUE ET DU TRANSPORT
PONDÉRATION DE C
23
Estimation of the weightDE chemical reactivity and
of MASSE SUR LA RÉACTIVITÉ ANODIQUE AU CO2 À 960°C
mass transport ESTIMATION OF THE WEIGHT anode
on the overall CO2 reactivity of OF CHEMICAL REACTIVITY AND MASS
at 960OC
TRANSPORT ON THE OVERALL CO2 REACTIVITY OF ANODE AT 960°C
F. Chevarin1,2, H. Alamdari1,2, G. Aryanpour1,2, D. Picard2, M. Fafard2, D. Ziegler3
1Department
of Mining, Metallurgical and Materials Engineering, 1065 avenue de la Médecine
Université Laval, Québec, QC, G1V 0A6,2
Canada
Auteur 1, Author
Industrial Research Chair MACE3 and Aluminium Research Centre – REGAL
1 Département et G1V 0A6, 1
Université Laval, Québec, QC,Institution Canada
3Alcoa Primary Metals, Alcoa Technical Center, 100 Technical Drive, Alcoa Center, PA,15069-0001, USA
2NSERC/Alcoa
2
department and Institution 2.
Objectives
Introduction
Carbon anode used in Hall-Héroult electrolysis process is subject to carboxy
1st: To confirm the chemical regime of carbon
gasification. The rate of the reaction between carbon and CO2 is affected by mass
mass loss under CO2 at 960 OC;
transport through anode pores. A concentration gradient is created through anode. To
2nd: To evaluate the weight of chemical
quantify the effect of mass transport limitations on the chemical reaction, the mass loss
reactivity versus the reactivity under mass
of carbon powder bed, determined in chemical regime (without mass transport
limitations), has been compared with mass loss under [CO2] limitations.
transport limitations.
Problematic
How the CO2 anode reactivity is decreased by the mass transport ?
Experimental procedure
Mass loss versus time at
different temperatures
CO2 reactivity test, TGA with
sleeve (CO2 flow : 100 ml/min)
Anode milling
at high energy
Anode compacting
and baking
1,00
Anode
particles
(27 µm)
0,40
ln m(t) (mg)
Baked
anode
Ln m(t) vs Reaction time of anode powder (2 mg)
on fixed bed reactor with CO2 at different
temperatures in a TGA Apparatus
0,70
0,10
-0,20
-0,50
-0,80
860 °C
-1,40
910 °C
-0.0047x + 0.6931 -0.019x + 0.6931
R² = 0.9927
R² = 0.9966
-1,10
0
20
40
935 °C
960 °C
-0.0094x + 0.7419 -0.0283x + 0.6931
R² = 0.9986
R² = 0.9973
60
80
Reaction time (min)
985 °C
-0.0354x + 0.8755
R² = 0.9948
100
120
Results
Kinetic constant vs Temperature of anode powder
(≈ 2 mg, 27 µm) with CO2 on TGA apparatus
0,80
0,82
0,84
0,86
0,88
0,90
-3,5
ln k = -24.320 x 1000/T + 16.060
R² = 0.979
ln k (1/min)
-4,0
-4,5
Arrhenius