XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 2061
They remain relevant for enriching both low-grade and
high-grade ores, with studies suggesting that diverse equip-
ment combinations within or across gravity methods can
optimize concentrate production and plant design. Spiral
concentrators, known for their low operating costs, are par-
ticularly common due to their versatility in handling ores
with diverse mineral densities and a wide size range (3 mm
to 45 μm). This adaptability has made them increasingly in
demand in recent decades. Each spiral concentrator design
has a unique profile, pitch, and diameter tailored for maxi-
mum recovery based on its application. Conventional spiral
concentrators had constraints related to particle size, with
upper limit of 1 to 2 mm and 75 μm as the lower limit.
Mineral spirals are capable of effectively treating low-grade
and high-grade ores within the size range of 30 to 60 μm,
considering the differences in densities between minerals
and gangue materials (Richards et al., 2000). Notably, finer
and denser particles below 75 μm face challenges in existing
trough designs, as they tend to be entrained in the outer
turbulent zones, leading to their loss in tailings. This phe-
nomenon is attributed to their failure to migrate towards
the inner zones. Additionally, very fine, lighter particles
are prone to being swept into the inner zones of the spiral
trough due to agglomeration and interlocking within the
coarser concentrates. Spiral concentrators find application
in treating a variety of ores, including chromite, iron ore,
gold ore, beach sands, and coal cleaning, which often con-
sist of bi-component and multi-component mixtures. To
enhance separation efficiency, it is essential to comprehend
the particle-particle interactions and segregation patterns
during the separation process. A detailed understanding
on particle separation in spiral concentrators by using vari-
ous mineral ores is limited in the past (Holland-Batt and
Holtham 1991 Atasoy and Spottiswood 1995 Mahran et
al. 2015 Mishra and Tripathy 2010 Boucher et al., 2016).
Several research studies have been explored the effec-
tiveness of spiral concentrators for mineral recovery across
various applications, including coal cleaning, low-grade
chromite and iron ore beneficiation, and tailings reprocess-
ing. Spiral concentrators proved to be highly advantageous in
coal cleaning due to its ease of operation, cost-effectiveness,
and high efficiency (Phengsaart et al., 2023). The low-cost
separation technologies developed to eliminate undesirable
mineral matter and moisture, enhancing the efficiency in
both coarse/intermediate and fine/ultrafine coal cleaning
circuits (Noble and Luttrell 2015). Across Europe, coal spi-
rals stand out for their affordability, simplicity, and effec-
tiveness in both primary and secondary fine coal cleaning
(3–0.1 mm), making them an attractive option for exist-
ing plants to boost efficiency (Bohle and Wellings 1989).
Fine coal spirals outperform a water cyclone in ash removal
for larger particles, while the efficiency for both decreased
below 125 microns (Hornsby and Watson 1993). Low-rank
lignite coals pose a cleaning challenge due to their abun-
dance of near-gravity material, potentially hindering their
use as an energy source. Utilizing gravity separation and
enhanced gravity separation techniques (DMS, Reichert
Spiral, MGS, Falcon concentrator) on low-rank lignite coal
revealed more efficient cleaning in finer size fractions, offer-
ing calorific value improvements for diverse uses (Tozsin,
Acar, and Sivrikaya 2018). Reichert spiral, developed for
fine coal beneficiation in the size range of –3 +0.1 mm effec-
tively clean bituminous coal at specific densities, requiring
fewer cleaning stages than lignitic coals but having a mini-
mum separation density threshold (Atesok, Yildirim, and
Celik 1993). Dense medium separation and Reichert spi-
rals effectively cleaned low-rank lignite coal for both coarse
and fine fractions., achieving high recoveries and suitable
ash content for industrial use (Sivrikaya 2014). Multi-stage
spiral recycling and specific gravity separation offer prom-
ising results for ash reduction and yield improvement of
Indian high ash non-coking coal (NCC) compared to jig-
ging and spiral concentrator operations(Saida et al., 2020).
Modified water-only cyclones (MWOC) offer a simple and
cost-effective option for pre-enriching fine coal, matching
clean coal quality with spiral and flotation but requiring
further processing due to lower yield and combustible losses
in rejects (Hacifazlioglu 2012). A high-sulphur fine coal
cleaning study found a linear screen and enhanced gravity
separator circuit outperformed a classifying cyclone circuit,
achieving significant sulfur and ash reductions of -2 mm
particle size (Mohanty, Samal, and Palit 2008). The turk-
ish coal processed via gravity methods yielded promising
results, with MGS significantly improving calorific value
and ash content in finer fractions (Erdem et al., 2012).
(Chaurasia, Sahu, and Nikkam 2018) explored the utility
of the multi-gravity separator (MGS) for effective benefi-
ciation of ultrafine size coal fines below –75 µm, resulting
in a maximized yield of 74.59%, an 84.56% combustibles
recovery, and the lowest ash content of 19.22% from a feed
ash of 33.5%.
Many research studies have demonstrated the benefici-
ation of low-grade chromite ores through the application of
gravity concentration techniques. Chromite ore is a complex
multi-component mineral that contains iron, aluminium,
chromium, and silica in major proportions. Utilizing grav-
ity concentration methods, it is possible to upgrade low-
grade Indian chromite ore, typically containing 16–25%
Cr2O3, to meet the refractory-grade specifications of
30–40% Cr2O3. (Murthy, Tripathy, and Kumar 2011).
They remain relevant for enriching both low-grade and
high-grade ores, with studies suggesting that diverse equip-
ment combinations within or across gravity methods can
optimize concentrate production and plant design. Spiral
concentrators, known for their low operating costs, are par-
ticularly common due to their versatility in handling ores
with diverse mineral densities and a wide size range (3 mm
to 45 μm). This adaptability has made them increasingly in
demand in recent decades. Each spiral concentrator design
has a unique profile, pitch, and diameter tailored for maxi-
mum recovery based on its application. Conventional spiral
concentrators had constraints related to particle size, with
upper limit of 1 to 2 mm and 75 μm as the lower limit.
Mineral spirals are capable of effectively treating low-grade
and high-grade ores within the size range of 30 to 60 μm,
considering the differences in densities between minerals
and gangue materials (Richards et al., 2000). Notably, finer
and denser particles below 75 μm face challenges in existing
trough designs, as they tend to be entrained in the outer
turbulent zones, leading to their loss in tailings. This phe-
nomenon is attributed to their failure to migrate towards
the inner zones. Additionally, very fine, lighter particles
are prone to being swept into the inner zones of the spiral
trough due to agglomeration and interlocking within the
coarser concentrates. Spiral concentrators find application
in treating a variety of ores, including chromite, iron ore,
gold ore, beach sands, and coal cleaning, which often con-
sist of bi-component and multi-component mixtures. To
enhance separation efficiency, it is essential to comprehend
the particle-particle interactions and segregation patterns
during the separation process. A detailed understanding
on particle separation in spiral concentrators by using vari-
ous mineral ores is limited in the past (Holland-Batt and
Holtham 1991 Atasoy and Spottiswood 1995 Mahran et
al. 2015 Mishra and Tripathy 2010 Boucher et al., 2016).
Several research studies have been explored the effec-
tiveness of spiral concentrators for mineral recovery across
various applications, including coal cleaning, low-grade
chromite and iron ore beneficiation, and tailings reprocess-
ing. Spiral concentrators proved to be highly advantageous in
coal cleaning due to its ease of operation, cost-effectiveness,
and high efficiency (Phengsaart et al., 2023). The low-cost
separation technologies developed to eliminate undesirable
mineral matter and moisture, enhancing the efficiency in
both coarse/intermediate and fine/ultrafine coal cleaning
circuits (Noble and Luttrell 2015). Across Europe, coal spi-
rals stand out for their affordability, simplicity, and effec-
tiveness in both primary and secondary fine coal cleaning
(3–0.1 mm), making them an attractive option for exist-
ing plants to boost efficiency (Bohle and Wellings 1989).
Fine coal spirals outperform a water cyclone in ash removal
for larger particles, while the efficiency for both decreased
below 125 microns (Hornsby and Watson 1993). Low-rank
lignite coals pose a cleaning challenge due to their abun-
dance of near-gravity material, potentially hindering their
use as an energy source. Utilizing gravity separation and
enhanced gravity separation techniques (DMS, Reichert
Spiral, MGS, Falcon concentrator) on low-rank lignite coal
revealed more efficient cleaning in finer size fractions, offer-
ing calorific value improvements for diverse uses (Tozsin,
Acar, and Sivrikaya 2018). Reichert spiral, developed for
fine coal beneficiation in the size range of –3 +0.1 mm effec-
tively clean bituminous coal at specific densities, requiring
fewer cleaning stages than lignitic coals but having a mini-
mum separation density threshold (Atesok, Yildirim, and
Celik 1993). Dense medium separation and Reichert spi-
rals effectively cleaned low-rank lignite coal for both coarse
and fine fractions., achieving high recoveries and suitable
ash content for industrial use (Sivrikaya 2014). Multi-stage
spiral recycling and specific gravity separation offer prom-
ising results for ash reduction and yield improvement of
Indian high ash non-coking coal (NCC) compared to jig-
ging and spiral concentrator operations(Saida et al., 2020).
Modified water-only cyclones (MWOC) offer a simple and
cost-effective option for pre-enriching fine coal, matching
clean coal quality with spiral and flotation but requiring
further processing due to lower yield and combustible losses
in rejects (Hacifazlioglu 2012). A high-sulphur fine coal
cleaning study found a linear screen and enhanced gravity
separator circuit outperformed a classifying cyclone circuit,
achieving significant sulfur and ash reductions of -2 mm
particle size (Mohanty, Samal, and Palit 2008). The turk-
ish coal processed via gravity methods yielded promising
results, with MGS significantly improving calorific value
and ash content in finer fractions (Erdem et al., 2012).
(Chaurasia, Sahu, and Nikkam 2018) explored the utility
of the multi-gravity separator (MGS) for effective benefi-
ciation of ultrafine size coal fines below –75 µm, resulting
in a maximized yield of 74.59%, an 84.56% combustibles
recovery, and the lowest ash content of 19.22% from a feed
ash of 33.5%.
Many research studies have demonstrated the benefici-
ation of low-grade chromite ores through the application of
gravity concentration techniques. Chromite ore is a complex
multi-component mineral that contains iron, aluminium,
chromium, and silica in major proportions. Utilizing grav-
ity concentration methods, it is possible to upgrade low-
grade Indian chromite ore, typically containing 16–25%
Cr2O3, to meet the refractory-grade specifications of
30–40% Cr2O3. (Murthy, Tripathy, and Kumar 2011).
