Aluminium electrolytic bath analysis

CubiX3 Potflux

The production of aluminium from purified alumina by electrolysis (Hall-

Héroult-process) is a very energy-consuming process. The concentration

of main components in the electrolyte must be rigidly controlled in

order to maintain optimum conditions during the production process.

X-ray diffraction (XRD) is the optimal

technique for fast and accurate

monitoring of the bath parameters

and the phase composition. It can be

applied on different types of electrolytic

baths (addition of Ca, Mg, Li, K).

Innovative methods provide true phase

concentrations in addition to common

bath parameters such as bath ratio (BR),

excess AlF3 (exAlF3), calcium content

(CaF2) and free alumina content

(α-Al2O3).

In addition to the monitoring of electrolytic

baths, XRD can also be used to inspect

incoming goods such as, refined alumina,

carbon anodes, cryolites and bauxites.

Benefits

• Maintain optimal bath conditions

by frequent monitoring of bath

parameters

• Simultaneous analysis of true

bath parameters and real phase

composition

• One method for a wide range of

bath ratios

• No consumables for sample taking

and analysis

• Fully automatable (from sample

preparation to result reporting)

• Fast ROI due to multiple

applications (raw materials,

alumina, electrolytic baths, carbon

anodes)

• Effective use of energy

Alt

ho

ug

h d

ilig

ent

care

has

bee

n u

sed

to

en

sure

th

at t

he

info

rmat

ion

her

ein

is a

ccu

rate

, no

thin

g c

on

tain

ed h

erei

n c

an b

e co

nst

rued

to

imp

ly a

ny

rep

rese

nta

tio

n o

r w

arra

nty

as

to t

he

accu

racy

, cu

rren

cy o

r co

mp

lete

nes

s o

f th

is in

form

atio

n. T

he

con

ten

t h

ereo

f is

su

bje

ct t

o c

han

ge

wit

ho

ut

furt

her

no

tice

. Pl

ease

co

nta

ct u

s fo

r th

e la

test

ver

sio

n o

f th

is d

ocu

men

t o

r fu

rth

er in

form

atio

n. ©

PA

Nal

ytic

al B

.V.,

Alm

elo

/ Th

e N

eth

erla

nd

s. 9

498

702

1651

2 PN

1037

8

Modern Rietveld analysis of electrolytic bathsThe powerful and fast full pattern Rietveld method is the state-of-art technique for the determination of the phase composition and the relevant bath parameters (e.g. bath ratio, excess AlF3, CaF2, MgF2, α-Al2O3, etc.) in electrolytic bath samples. Typical measurement times are ca. 1-2 minutes. No standards, intensity monitors and recalibrations are required. Different Ca-cryolite phases in standard electrolytic baths samples can easily be quantified using the Rietveld method which is not possible with traditional calibration line based analysis.

Traditional calibration line based bath analysisCalibration based analysis of aluminium baths can be done with a linear detector such as the X’Celerator or with a point detector. For the simultaneous monitoring of the total calcium content (CaF2) the CubiX3 Potflux diffractometer features a high intensity XRF channel. Benefits are very short measurement times that allow frequently bath monitoring.

6.0

Co

nce

ntr

atio

n

Intensity [kcps]

CaF25.5

5.0

4.5

4.0

3.5

3.0

2.5

2.0

60 80 100 120 140 160 180

Calibration curve for fluorite

Global and near PANalytical B.V.Lelyweg 1, 7602 EA AlmeloP.O. Box 13, 7600 AA AlmeloThe NetherlandsT +31 (0) 546 534 444F +31 (0) 546 534 598 info@panalytical.comwww.panalytical.com

Regional sales officesAmericasT +1 508 647 1100 F +1 508 647 1115

Europe, Middle East, AfricaT +31 (0) 546 834 444 F +31 (0) 546 834 499

Asia PacificT +65 6741 2868 F +65 6741 2166

Analysis of carbon anodesCubiX3 Potflux can also be used to monitor the quality of the carbon anodes. The efficiency and lifetime of an anode is mainly controlled by the average crystallite size (Lc) of the graphite platelets. XRD allows the analysis of the crystallite size and respectively the efficiency of the anodes.The ASTM standard test method (ASTM D5187) is included in PANalytical’s solution for electrolytic bath analysis.

Example of the analysis of the crystallite size Lc of a graphite anodeReferencesScarlett, N.V.Y. & Madsen, I.C. (2006) Quantification of phases with partial or no known crystal structure. Powder Diffraction, 21(4), 278-284

Rietveld analysis of a standard electrolytic bath showing phase concentrations, including two different Ca-Cryolite phases from a minute scan

CaF2 calibration curve