2296 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
export, contributing to rising prices and consequent cost
escalation for depressants used in mining.
Due to these factors, several studies, such as those by
Moreira (2013), Kar et al. (2013), Marins et al. (2020),
and Silva et al. (2021), have been exploring the application
of alternative botanical sources of starch that are efficient,
cost-effective, and sustainable. Silva et al. (2018) observed
in flotation tests for pure hematite and quartz, conducted
in a Hallimond tube, that sorghum starch exhibits depres-
sant action similar to or even superior to corn starch on
the hematite surface under certain conditions. Sorghum,
a cereal grown in Brazil exclusively as feedstock for animal
nutrition, offers advantages such as low water and soil fer-
tility requirements and a short vegetative cycle compared
to corn cultivation. Additionally, it has a price per sack 20
to 30% lower than corn. Due to these characteristics, sor-
ghum starch can be a viable alternative, both technically
and economically, to corn starch as a depressant in iron ore
flotation.
Therefore, this study aims to show the performance
of sorghum flour from the graniferous variety Sorghum
bicolor (L.) Moench as a depressant in the reverse cationic
flotation of a Brazilian iron ore from Serra do Sapo deposit,
situated in Minas Gerais state. The analysis will be carried
out through bench-scale rougher flotation tests, compar-
ing the results with the use of the conventional depressant
(corn grits) industrially adopted for this ore. Additionally,
the influence of varying flotation operational parameters on
the performance of sorghum flour will be examined.
METHODOLOGY
Ore and Depressant Samples Preparation
Approximately 250 kg of iron ore samples from the feed
of the flotation circuit (underflow of the desliming hydro-
cyclones) of the Minas-Rio concentration plant, owned
by Anglo American, were received and allocated in the
Laboratory of Modeling and Research in Mineral Processing
(LaMPPMin). The preparation procedure was carried out
by drying, homogenization and quartering operations, and
the separation of 1.0 kg aliquots for bench-scale flotation
tests.
The grains of the Sorghum bicolor (L.) Moench species
were used as the raw material in the production of flour.
Initially, the grains were sifted through a manual sieve to
remove contaminants such as straw and soil. After the clean-
ing procedure, the grains were properly dried and ground
to produce flour using a cereal mill. Meanwhile, corn grits
samples, which were already suitable for the gelatinization
process, were provided by Anglo American.
Indirect Determination of Fe and SiO2 Content
The Fe and SiO2 content of the flotation products were
indirectly estimated by measuring concentrate densities
using a 1000 mL pycnometer. The correlation between
density and the content assumes that the ore has a binary
composition of only hematite and quartz, with densities of
5.3 and 2.65 g/cm3, respectively. The equations correlat-
ing these parameters were developed by Anglo American
through systematic data collection from the industrial flo-
tation circuit, allowing the generation and refinement of
the proposed mathematical models. In order to maintain
industrial confidentiality, these models could not be dis-
closed in this work. Further, the results will be validated by
chemical analysis via XRF of the samples.
Bench-Scale Flotation Tests
The tests were conducted in the Flotation Laboratory of
LaMPPMin using a bench-scale mechanical cell manu-
factured by ENGENDRAR, model CFB 1000N, with
rotation control by a frequency inverter and aeration by
compressed air injection. The experimental parameters for
the tests are summarized in Table 1. These values follow the
parameters adopted by Anglo American in the industrial
plant.
The preparation of the Flotigam 7500 (amine) collec-
tor, supplied by Clariant ®, started by diluting 1.0 g in 100
Table 1. Experimental parameters for iron ore flotation tests
Experimental Parameters Value
Impeller rotation (rpm) 1500 (conditioning) and 1300 (flotation)
Solids content in conditioning (%)60
Solids content in flotation (%)40
Conditioning time (min) 1 (collector) and 5 (depressant)
Air flow rate (L/min) 2.5
Collector dosage (g/t
SiO2 )150
Starch :NaOH ratio in gelatinization 5:1
Depressant dosage (g/tFe) 1450
pH 10.5
export, contributing to rising prices and consequent cost
escalation for depressants used in mining.
Due to these factors, several studies, such as those by
Moreira (2013), Kar et al. (2013), Marins et al. (2020),
and Silva et al. (2021), have been exploring the application
of alternative botanical sources of starch that are efficient,
cost-effective, and sustainable. Silva et al. (2018) observed
in flotation tests for pure hematite and quartz, conducted
in a Hallimond tube, that sorghum starch exhibits depres-
sant action similar to or even superior to corn starch on
the hematite surface under certain conditions. Sorghum,
a cereal grown in Brazil exclusively as feedstock for animal
nutrition, offers advantages such as low water and soil fer-
tility requirements and a short vegetative cycle compared
to corn cultivation. Additionally, it has a price per sack 20
to 30% lower than corn. Due to these characteristics, sor-
ghum starch can be a viable alternative, both technically
and economically, to corn starch as a depressant in iron ore
flotation.
Therefore, this study aims to show the performance
of sorghum flour from the graniferous variety Sorghum
bicolor (L.) Moench as a depressant in the reverse cationic
flotation of a Brazilian iron ore from Serra do Sapo deposit,
situated in Minas Gerais state. The analysis will be carried
out through bench-scale rougher flotation tests, compar-
ing the results with the use of the conventional depressant
(corn grits) industrially adopted for this ore. Additionally,
the influence of varying flotation operational parameters on
the performance of sorghum flour will be examined.
METHODOLOGY
Ore and Depressant Samples Preparation
Approximately 250 kg of iron ore samples from the feed
of the flotation circuit (underflow of the desliming hydro-
cyclones) of the Minas-Rio concentration plant, owned
by Anglo American, were received and allocated in the
Laboratory of Modeling and Research in Mineral Processing
(LaMPPMin). The preparation procedure was carried out
by drying, homogenization and quartering operations, and
the separation of 1.0 kg aliquots for bench-scale flotation
tests.
The grains of the Sorghum bicolor (L.) Moench species
were used as the raw material in the production of flour.
Initially, the grains were sifted through a manual sieve to
remove contaminants such as straw and soil. After the clean-
ing procedure, the grains were properly dried and ground
to produce flour using a cereal mill. Meanwhile, corn grits
samples, which were already suitable for the gelatinization
process, were provided by Anglo American.
Indirect Determination of Fe and SiO2 Content
The Fe and SiO2 content of the flotation products were
indirectly estimated by measuring concentrate densities
using a 1000 mL pycnometer. The correlation between
density and the content assumes that the ore has a binary
composition of only hematite and quartz, with densities of
5.3 and 2.65 g/cm3, respectively. The equations correlat-
ing these parameters were developed by Anglo American
through systematic data collection from the industrial flo-
tation circuit, allowing the generation and refinement of
the proposed mathematical models. In order to maintain
industrial confidentiality, these models could not be dis-
closed in this work. Further, the results will be validated by
chemical analysis via XRF of the samples.
Bench-Scale Flotation Tests
The tests were conducted in the Flotation Laboratory of
LaMPPMin using a bench-scale mechanical cell manu-
factured by ENGENDRAR, model CFB 1000N, with
rotation control by a frequency inverter and aeration by
compressed air injection. The experimental parameters for
the tests are summarized in Table 1. These values follow the
parameters adopted by Anglo American in the industrial
plant.
The preparation of the Flotigam 7500 (amine) collec-
tor, supplied by Clariant ®, started by diluting 1.0 g in 100
Table 1. Experimental parameters for iron ore flotation tests
Experimental Parameters Value
Impeller rotation (rpm) 1500 (conditioning) and 1300 (flotation)
Solids content in conditioning (%)60
Solids content in flotation (%)40
Conditioning time (min) 1 (collector) and 5 (depressant)
Air flow rate (L/min) 2.5
Collector dosage (g/t
SiO2 )150
Starch :NaOH ratio in gelatinization 5:1
Depressant dosage (g/tFe) 1450
pH 10.5