XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 1325
high oxidation levels, low iron content and the challenges
of beneficiation (Liu et al., 2020 Wang et al., 2019).
However, the presence of valuable minerals such as rare
earths and fluorite in these ores offers the potential to alle-
viate resource scarcity through their effective development.
Traditional beneficiation methods are limited in their
ability to process these low-grade ores, resulting in wasted
resources and environmental degradation (Yuan et al.,
2022 Zhang et al., 2019). Fortunately, with the continu-
ous advancement of metallurgical technology, the recovery
of iron and other valuable minerals from these complex,
low-grade and difficult-to-process ores has become feasible
(Qin et al., 2023 Qiu et al., 2023 Zhou et al., 2021) It has
been reported that magnetic roasting followed by magnetic
separation can effectively process the polymetallic refrac-
tory iron ores from the Bayan Obo region. In addition,
high-temperature direct reduction can convert low-grade
iron ores directly into raw materials for blast furnace steel-
making (Gao et al., 2010). However, such methods require
roasting temperatures in excess of 1000°C, resulting in high
energy consumption (Zhou et al., 2020). During the roast-
ing process, the use of additives (such as Ca (OH)2 and
Na2CO3) can significantly reduce the roasting temperature
(Zheng et al., 2017). However, this approach introduces
additional impurities that are detrimental to the subse-
quent recovery of the ore samples.
In addition, most current reduction roasting methods
rely on carbon-based reducing agents (Roy et al., 2020 She
et al., 2016 Zhang et al., 2023a). While effective, these
methods are energy intensive and generate significant
amounts of carbon dioxide, posing challenges to environ-
mental protection and sustainable development. Therefore,
finding a clean and efficient alternative to traditional car-
bon-based reduction has become a research focus. In this
regard, Hydrogen-based Mineral Phase Transformation
(HMPT) technology offers a promising solution (Li et al.,
2021 Yu et al., 2023 Yuan et al., 2020b Zhou et al., 2021)
.This technology uses hydrogen-rich gas as a reducing
agent, which significantly lowers the reduction temperature
and energy consumption while reducing CO2 emissions,
providing significant environmental and resource recovery
benefits. Ongoing studies have explored the feasibility of
using HMPT technology to process the difficult-to-select
iron ores from the Bayan Obo region, but its prospects for
industrial application require further validation (Ning et
al., 2024).
The purpose of this study is to process the refractory
iron ores from the Bayan Obo region using a hydrogen-
based mineral phase transformation (HMPT) pilot plant,
to verify the reliability of this method, and to study the
phase transformation of iron minerals during the roast-
ing process. Trials were conducted to optimize the HMPT
temperature, gas flow rate, reducing gas concentration, and
feed rate, followed by a 48-hour continuous stability exper-
iment. Samples were crushed and magnetically separated
to evaluate concentrate yield, TFe grade, and recovery to
assess the reliability of the HMPT system. The phase trans-
formation, microstructure and magnetic properties of the
samples were investigated using X-ray diffraction (XRD),
scanning electron microscopy coupled with energy disper-
sive spectroscopy (SEM-EDS) and vibrating sample mag-
netometer (VSM).
MATERIALS AND EXPERIMENTAL
Materials
Complex polymetallic ore samples from Baotou City, Inner
Mongolia Autonomous Region, China were subjected to
magnetic separation for pre-enrichment processing (Ning
et al., 2024). The primary chemical and iron mineralogi-
cal compositions of the samples are presented in Tables 1
and 2, respectively. The results indicate that iron is the
most valuable element for recovery with a total iron con-
tent of 37.72%, mainly in the form of hematite (19.14%)
and magnetite (17.14%). Major impurities include SiO2
(7.40%), with CaO, F and REO contents of 11.20%,
6.07% and 5.33%, respectively. X-ray diffraction analysis
shows that the major mineral phases composed of these
elements are fluorite and bastnaesite, which also have sig-
nificant recovery value. Quartz and dolomite are the major
impurities in the samples. It is evident that the mineralogi-
cal composition of the sample is highly complex and poses
significant challenges for recovery.
Experimental Equipment and Method
This study investigated the effects of key operational param-
eters of HMPT on the recovery of iron products at pilot
scale, and a continuous and stable HMPT experiment was
conducted for 48 h under optimal conditions. The pilot
scale HMPT experiment was conducted in an innovative
roasting system (Figure 2). Thermocouples and pressure
sensors were installed at several critical locations within the
system, allowing real-time transmission of temperature and
pressure data back to the central control system for precise
adjustments.
The HMPT reactor operates under vacuum generated
by a Roots blower. Iron ore is fed from the storage bin to
the screw feeder by a loss-in-weight system and then trans-
ported to a cyclone preheater where it is preheated by hot
gases (300–600°C). The ore then passes through a shut-
off valve into the suspension furnace. During this process,
high oxidation levels, low iron content and the challenges
of beneficiation (Liu et al., 2020 Wang et al., 2019).
However, the presence of valuable minerals such as rare
earths and fluorite in these ores offers the potential to alle-
viate resource scarcity through their effective development.
Traditional beneficiation methods are limited in their
ability to process these low-grade ores, resulting in wasted
resources and environmental degradation (Yuan et al.,
2022 Zhang et al., 2019). Fortunately, with the continu-
ous advancement of metallurgical technology, the recovery
of iron and other valuable minerals from these complex,
low-grade and difficult-to-process ores has become feasible
(Qin et al., 2023 Qiu et al., 2023 Zhou et al., 2021) It has
been reported that magnetic roasting followed by magnetic
separation can effectively process the polymetallic refrac-
tory iron ores from the Bayan Obo region. In addition,
high-temperature direct reduction can convert low-grade
iron ores directly into raw materials for blast furnace steel-
making (Gao et al., 2010). However, such methods require
roasting temperatures in excess of 1000°C, resulting in high
energy consumption (Zhou et al., 2020). During the roast-
ing process, the use of additives (such as Ca (OH)2 and
Na2CO3) can significantly reduce the roasting temperature
(Zheng et al., 2017). However, this approach introduces
additional impurities that are detrimental to the subse-
quent recovery of the ore samples.
In addition, most current reduction roasting methods
rely on carbon-based reducing agents (Roy et al., 2020 She
et al., 2016 Zhang et al., 2023a). While effective, these
methods are energy intensive and generate significant
amounts of carbon dioxide, posing challenges to environ-
mental protection and sustainable development. Therefore,
finding a clean and efficient alternative to traditional car-
bon-based reduction has become a research focus. In this
regard, Hydrogen-based Mineral Phase Transformation
(HMPT) technology offers a promising solution (Li et al.,
2021 Yu et al., 2023 Yuan et al., 2020b Zhou et al., 2021)
.This technology uses hydrogen-rich gas as a reducing
agent, which significantly lowers the reduction temperature
and energy consumption while reducing CO2 emissions,
providing significant environmental and resource recovery
benefits. Ongoing studies have explored the feasibility of
using HMPT technology to process the difficult-to-select
iron ores from the Bayan Obo region, but its prospects for
industrial application require further validation (Ning et
al., 2024).
The purpose of this study is to process the refractory
iron ores from the Bayan Obo region using a hydrogen-
based mineral phase transformation (HMPT) pilot plant,
to verify the reliability of this method, and to study the
phase transformation of iron minerals during the roast-
ing process. Trials were conducted to optimize the HMPT
temperature, gas flow rate, reducing gas concentration, and
feed rate, followed by a 48-hour continuous stability exper-
iment. Samples were crushed and magnetically separated
to evaluate concentrate yield, TFe grade, and recovery to
assess the reliability of the HMPT system. The phase trans-
formation, microstructure and magnetic properties of the
samples were investigated using X-ray diffraction (XRD),
scanning electron microscopy coupled with energy disper-
sive spectroscopy (SEM-EDS) and vibrating sample mag-
netometer (VSM).
MATERIALS AND EXPERIMENTAL
Materials
Complex polymetallic ore samples from Baotou City, Inner
Mongolia Autonomous Region, China were subjected to
magnetic separation for pre-enrichment processing (Ning
et al., 2024). The primary chemical and iron mineralogi-
cal compositions of the samples are presented in Tables 1
and 2, respectively. The results indicate that iron is the
most valuable element for recovery with a total iron con-
tent of 37.72%, mainly in the form of hematite (19.14%)
and magnetite (17.14%). Major impurities include SiO2
(7.40%), with CaO, F and REO contents of 11.20%,
6.07% and 5.33%, respectively. X-ray diffraction analysis
shows that the major mineral phases composed of these
elements are fluorite and bastnaesite, which also have sig-
nificant recovery value. Quartz and dolomite are the major
impurities in the samples. It is evident that the mineralogi-
cal composition of the sample is highly complex and poses
significant challenges for recovery.
Experimental Equipment and Method
This study investigated the effects of key operational param-
eters of HMPT on the recovery of iron products at pilot
scale, and a continuous and stable HMPT experiment was
conducted for 48 h under optimal conditions. The pilot
scale HMPT experiment was conducted in an innovative
roasting system (Figure 2). Thermocouples and pressure
sensors were installed at several critical locations within the
system, allowing real-time transmission of temperature and
pressure data back to the central control system for precise
adjustments.
The HMPT reactor operates under vacuum generated
by a Roots blower. Iron ore is fed from the storage bin to
the screw feeder by a loss-in-weight system and then trans-
ported to a cyclone preheater where it is preheated by hot
gases (300–600°C). The ore then passes through a shut-
off valve into the suspension furnace. During this process,