Abstract:
Carboxymethyl cellulose is an organic binder used in the iron ore
pelletizing industry. The basic principles of how carboxymethyl cellulose
(CMC) solutions behave during the pelletizing process and how these
principles affect the drop and compression strengths of the pellets are
poorly understood. The aim of the investigation was therefore to gain
knowledge on the behaviour of CMC during the pelletizing of haematite
concentrate.
Haematite pellets with different additions of CMC (0.1–0.4 wt%), were
subjected to drop tests, compression tests, and free moisture content
analysis. The relationship between the drop strength, compression
strength, free moisture content, elapsed time, and CMC concentration was
analysed.
The drop strength had a strong correlation with the free moisture
content of the haematite pellets, with a correlation coefficient of 0.94. The
compression strength of the CMC-bonded haematite pellets increased as
the free moisture content decreased, reaching a maximum upon depletion
of the free moisture content. Haematite pellets with CMC concentrations of
0.1 and 0.2 wt% developed most of their strength within the first day after
pelletizing, whereas pellets with concentrations of 0.3 and 0.4 wt%
developed most of their strength between one and two days after
pelletizing. The time within which CMC-bonded haematite pellets develop
most of their strength is therefore dependent on the CMC concentration.
