4
noteworthy StackCell installation is the Kanawha Eagle
coal preparation plant flotation expansion, which resulted
in an increase of 8 to 11 ton/hr of fine coal production with
a corresponding payback period of less than three months
[16]. This paper details the successful development and
implementation of a StackCell flotation circuit for recovery
of metallurgical coal from ultrafine refuse from the deslime
cyclone overflow at Arch Resource’s Leer preparation plant.
Details on the process development are included to dem-
onstrate the scale-up from laboratory and pilot-scale testing
methodologies to the full-scale circuit design. Furthermore,
learnings from the commissioning and ramp- up period
are shared along with performance data through the first
year of operation. Overall, a substantial opportunity is con-
firmed for additional metallurgical coal production in des-
lime coal flotation circuits utilizing the StackCell flotation
technology.
STACKCELL TESTING AND CIRCUIT
DESIGN
StackCell Laboratory and Pilot Plant Testing
The StackCell flotation circuit design process consisted
of bench scale flotation tests followed by a pilot scale test
campaign. The basis for this evaluation was the determina-
tion of a froth carrying capacity limit and required flotation
residence time. The objective of the work was to determine
the appropriate StackCell model and quantity for the Leer
deslime cyclone overflow duty.
Coal flotation is a high mass pull, low residence time
process. As a result, for coal applications a StackCell flota-
tion circuit is generally defined by froth carrying capacity
rates. With decades of coal flotation experience, Eriez has
developed an in-house relationship for feed particle size
distribution versus carrying capacity for various coal types.
For this coal, with a minus 0.050-mm (by zero) particle
size distribution, a carry capacity limit of 0.04 tph/ft2 was
selected. The next step in the design process was to simulate
the StackCell performance through a bench-scale release
analysis test and determine the residence time requirement
by a bench-scale flotation kinetics test.
The bench-scale flotation tests were performed at Eriez’
global flotation laboratory in Erie, Pennsylvania on a rep-
resentative deslime cyclone overflow sample obtained from
the Leer preparation plant. Figure 3 illustrates product
ash versus combustible recovery from the release analysis
test and residence time versus combustible recovery from
the kinetics test. As shown, a 70% combustible recovery
is achievable with less than 7% product ash at a residence
time in the range of 90 seconds.
The next phase of development was an in-plant
StackCell pilot test campaign at the Leer preparation
plant to confirm StackCell performance and residence
time requirements. For this evaluation, flotation feed was
obtained from a single deslime cyclone overflow redirected
into a small surge tank for frother and diesel addition
(Figure 4), which was fed by gravity to the StackCell pilot
circuit. The StackCell pilot flotation circuit consisted of
three 2-ft diameter StackCells arranged in series with tail-
ings from the first StackCell feeding the second StackCell,
and the tailings from the second StackCell feeding the third
StackCell (Figure 5).
0
20
40
60
80
100
0 10 20 30
Product Ash (%)
Release Analysis
Kinetics Test
0
20
40
60
80
100
0 120 240 360 480 600 720
Flotation Residence Time (sec)
Kinetics Test
Figure 3. Combustible recovery versus product ash (top)
and residence time (bottom) for bench-scale flotation release
analysis and kinetics tests
Combustible
Recovery
(%)
Combustible
Recovery
(%)
noteworthy StackCell installation is the Kanawha Eagle
coal preparation plant flotation expansion, which resulted
in an increase of 8 to 11 ton/hr of fine coal production with
a corresponding payback period of less than three months
[16]. This paper details the successful development and
implementation of a StackCell flotation circuit for recovery
of metallurgical coal from ultrafine refuse from the deslime
cyclone overflow at Arch Resource’s Leer preparation plant.
Details on the process development are included to dem-
onstrate the scale-up from laboratory and pilot-scale testing
methodologies to the full-scale circuit design. Furthermore,
learnings from the commissioning and ramp- up period
are shared along with performance data through the first
year of operation. Overall, a substantial opportunity is con-
firmed for additional metallurgical coal production in des-
lime coal flotation circuits utilizing the StackCell flotation
technology.
STACKCELL TESTING AND CIRCUIT
DESIGN
StackCell Laboratory and Pilot Plant Testing
The StackCell flotation circuit design process consisted
of bench scale flotation tests followed by a pilot scale test
campaign. The basis for this evaluation was the determina-
tion of a froth carrying capacity limit and required flotation
residence time. The objective of the work was to determine
the appropriate StackCell model and quantity for the Leer
deslime cyclone overflow duty.
Coal flotation is a high mass pull, low residence time
process. As a result, for coal applications a StackCell flota-
tion circuit is generally defined by froth carrying capacity
rates. With decades of coal flotation experience, Eriez has
developed an in-house relationship for feed particle size
distribution versus carrying capacity for various coal types.
For this coal, with a minus 0.050-mm (by zero) particle
size distribution, a carry capacity limit of 0.04 tph/ft2 was
selected. The next step in the design process was to simulate
the StackCell performance through a bench-scale release
analysis test and determine the residence time requirement
by a bench-scale flotation kinetics test.
The bench-scale flotation tests were performed at Eriez’
global flotation laboratory in Erie, Pennsylvania on a rep-
resentative deslime cyclone overflow sample obtained from
the Leer preparation plant. Figure 3 illustrates product
ash versus combustible recovery from the release analysis
test and residence time versus combustible recovery from
the kinetics test. As shown, a 70% combustible recovery
is achievable with less than 7% product ash at a residence
time in the range of 90 seconds.
The next phase of development was an in-plant
StackCell pilot test campaign at the Leer preparation
plant to confirm StackCell performance and residence
time requirements. For this evaluation, flotation feed was
obtained from a single deslime cyclone overflow redirected
into a small surge tank for frother and diesel addition
(Figure 4), which was fed by gravity to the StackCell pilot
circuit. The StackCell pilot flotation circuit consisted of
three 2-ft diameter StackCells arranged in series with tail-
ings from the first StackCell feeding the second StackCell,
and the tailings from the second StackCell feeding the third
StackCell (Figure 5).
0
20
40
60
80
100
0 10 20 30
Product Ash (%)
Release Analysis
Kinetics Test
0
20
40
60
80
100
0 120 240 360 480 600 720
Flotation Residence Time (sec)
Kinetics Test
Figure 3. Combustible recovery versus product ash (top)
and residence time (bottom) for bench-scale flotation release
analysis and kinetics tests
Combustible
Recovery
(%)
Combustible
Recovery
(%)