Bentonite has been used by the taconite industry
since commercialization of the process in the early 1950's.
Although many alternate binders have been tested, including
organic materials, bentonite still remains the preferred
binder. Bentonite has the unique qualities that promote
stable green balling conditions and provides acceptable
strengths during drying, preheating, and contributes to the
fired pellet strength at an acceptable cost. The incentive
to consider other binders is based on such factors as
improving the metallurgical properties of the pellets,
decreasing their silica content, and lower overall costs.
The USBM conducted a number of small scale tests
using papermill sludge and other additives in place of
bentonite as a binder for taconite pellets. Their balling
tests indicated that acceptable green-ball strength could
be achieved with papermill sludge. The fired pellet evaluations,
however, were based on muffle furnace tests which do
not accurately predict the fired pellet quality. Although
the fired pellet data were also encouraging it was recognized
that pot-grate tests were needed to obtain more definitive
test data that could be directly related to commercial
practice. Subsequently, the USBM recommended that the IRRRB
fund an extension of the program to include pot-grate tests
to verify the fired pellet quality obtained in the muffle
furnace work. A test program was prepared by the Coleraine
Research Laboratory of the Natural Resources Research
Institute (NRRI) in cooperation with Dr. J. Nigro and Dr.
L. Haas, USBM, and Mr. S. Dickinson, IRRRB. The contract
proposal was submitted to the IRRRB January 27, 1988. The
contract included evaluation of concentrate and sludge filtering
and blending aspects, green-ball quality, and fired pellet
quality based on pot-grate tests. This report presents data on
all three aspects as stated in the contract and conclusions
regarding future efforts in this area.
Prepared for: Iron Range Resources and Rehabilitation Board
University of Minnesota Duluth, Natural Resources Research Institute, 5013 Miller Trunk Highway, Duluth, MN 55811-1442
Goetzman, Harold E.
Investigation of Papermill Sludge as a Taconite Binder.
University of Minnesota Duluth.
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