Characterization and comparison of new limestone additives
for LKAB's pellets according to texture and disintegration
properties
Abstract: The Swedish mining company LKAB is using limestone as additives for the
production of its iron ore pellets. The company is considering five new
proposals of limestones since the Nordkalk Company is soon no longer able
to provide limestone from the Storugns quarry which is the one that is used
today.
The first purpose in this study was to characterize and compare these five
new limestones in respect to their texture and their disintegration during
the transport from the quarry to the final destination in Malmberget,
considering the Storugns limestone as a reference material. The second aim
was to focus on finding any link between texture and disintegration
properties of the limestones. Another intention is that the methodology
which is used in this study will help the company to consider new proposals
of limestones in the future.
Six limestones from the Orsa, Storugns, Stucks, Vasalemma, Verdal and
Võhmuta quarries were analyzed by an optical microscopy analysis of the
textures. Two types of physical tests were also included in the study: a
tumbler test and a breakage test.
Six different textures were identified by a qualitative thin section
analysis which shows similarities between the limestones from different
origins but also a high variability of texture within a same quarry. A more
quantitative optical microscopy analysis led to the assumption of both the
degree of lithification and the amount of initial micro-cracks for each
sample. According to the physical test results, the limestones disintegrate
as follows, from the less to the more disintegrated: Stucks (7,6%),
Storugns (9,4%), Verdal (10,3%), Võhmuta (11,1%), Vasalemma (11,8%) and
Orsa (17,6%).
There is no evident textural parameter which is controlling directly the
disintegration of limestone. However the samples with a rather high
lithification and a rather low fracturing disintegrate less than samples
with a rather low lithification and a rather high fracturing. It is assumed
that the combination of degree of lithification together with the amount of
initial micro-cracks is somehow controlling the disintegration of
limestone.
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