302 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
Design of Experiment
Figure 2 shows the mixing vessel containing the produced
hemp biochar (a) alongside the resonant vibratory mixer
when the vessel is in its operational position. The experi-
ment aimed to assess how LFHA resonant vibrations,
specifically the operating parameters involved in the mix-
ing process, impact biochar surface area, with the goal of
enhancing the CO2 adsorption onto biochar.
The study employed the Response Surface Methodology
(RSM), a widely recognized statistical tool for optimizing
procedures involving independent variables, as proposed
by Pronzato, 2008. Analysis of Variance (ANOVA), a
statistical technique for analyzing variation in a response
variable determined by discrete factors, was also utilized,
as described by Larson, 2008. Despite the complexity
involved, many current studies avoid applying this concept
for optimization, preferring classical one-variable-at-a-time
methods like OVAT. However, these methods overlook vari-
able interactions, leading to a more extensive experimental
effort. Given the complexities of LFHA resonant vibratory
mixing and the resulting physical phenomena, RSM was
crucial for understanding higher-order effects and interac-
tions between factors.
Factors and Levels
The primary operating parameters influencing the mecha-
nochemical interactions of particles in the resonant vibra-
tory mixing system are biochar mass (grams), mixing time
(minutes), and mixing intensity (%).Therefore, these inde-
pendent variables (factors) were employed in developing
the central composite experimental design, with surface
area (m2/g) selected as the response. Table 1 summarizes
the factors and the levels used in the analysis. The levels/
ranges defined were selected to be sufficiently large to cover
and observe the best responses.
Mass (gram)
The specified range for the biochar mass is 1–11 grams. At
1 gram (–1 level), it represents the minimum mass from
which a sufficient sample can be obtained for subsequent
surface area analysis. On the other hand, at 11 grams (+1
level), it signifies the maximum mass considering the inte-
rior geometry of the mixing vessel. Selecting a higher mass
limits mixing efficiency by restricting particle movement
due to increased fill levels.
Time (min)
The selected levels or ranges for the time factor must be
extensive enough to allow for the measurement of physi-
cal changes, while avoiding extremes that could introduce
thermal effects.
Intensity (g)
In determining the optimal range for the intensity fac-
tor, the lower limit should be effective enough to capture
measurable physical changes, and the upper limit should
be selected to similarly prevent the occurrence of thermal
effects.
Using the factors and levels provided, the developed
RSM included twenty different combinations of biochar
mass (gram), mixing time (minute), and mixing intensity
(%).Performing twenty mixing tests based on these condi-
tions provided insights into the sensitivity of the response
(surface area) to these operating parameters. After finishing
each test under each particular set of conditions, the biochar
sample was retrieved from the mixing vessel for measuring
the surface area. The analysis of pore characterization, per-
formed in four replicates using the Anton-Paar Nova 800
BET, aimed to measure the surface area through N2 gaseous
adsorption at 77°K. Before the N2 gaseous adsorption, the
samples underwent essential degassing using the internal
degassing protocol of the instrument. The degassing con-
ditions were consistent with those employed during the
Table 1. The selected factors and their respective levels
for the analysis were determined based on the sample and
experimental conditions
Levels
Mass of Mixing
Intensity (%)Biochar, g Time, min
–1 1 2 15
0 (midpoint) 6 16 45
1 11 30 75
Figure 2. Resonant Vibratory Mixer (a) and the mixing vessel
containing the hemp biochar (b)
Design of Experiment
Figure 2 shows the mixing vessel containing the produced
hemp biochar (a) alongside the resonant vibratory mixer
when the vessel is in its operational position. The experi-
ment aimed to assess how LFHA resonant vibrations,
specifically the operating parameters involved in the mix-
ing process, impact biochar surface area, with the goal of
enhancing the CO2 adsorption onto biochar.
The study employed the Response Surface Methodology
(RSM), a widely recognized statistical tool for optimizing
procedures involving independent variables, as proposed
by Pronzato, 2008. Analysis of Variance (ANOVA), a
statistical technique for analyzing variation in a response
variable determined by discrete factors, was also utilized,
as described by Larson, 2008. Despite the complexity
involved, many current studies avoid applying this concept
for optimization, preferring classical one-variable-at-a-time
methods like OVAT. However, these methods overlook vari-
able interactions, leading to a more extensive experimental
effort. Given the complexities of LFHA resonant vibratory
mixing and the resulting physical phenomena, RSM was
crucial for understanding higher-order effects and interac-
tions between factors.
Factors and Levels
The primary operating parameters influencing the mecha-
nochemical interactions of particles in the resonant vibra-
tory mixing system are biochar mass (grams), mixing time
(minutes), and mixing intensity (%).Therefore, these inde-
pendent variables (factors) were employed in developing
the central composite experimental design, with surface
area (m2/g) selected as the response. Table 1 summarizes
the factors and the levels used in the analysis. The levels/
ranges defined were selected to be sufficiently large to cover
and observe the best responses.
Mass (gram)
The specified range for the biochar mass is 1–11 grams. At
1 gram (–1 level), it represents the minimum mass from
which a sufficient sample can be obtained for subsequent
surface area analysis. On the other hand, at 11 grams (+1
level), it signifies the maximum mass considering the inte-
rior geometry of the mixing vessel. Selecting a higher mass
limits mixing efficiency by restricting particle movement
due to increased fill levels.
Time (min)
The selected levels or ranges for the time factor must be
extensive enough to allow for the measurement of physi-
cal changes, while avoiding extremes that could introduce
thermal effects.
Intensity (g)
In determining the optimal range for the intensity fac-
tor, the lower limit should be effective enough to capture
measurable physical changes, and the upper limit should
be selected to similarly prevent the occurrence of thermal
effects.
Using the factors and levels provided, the developed
RSM included twenty different combinations of biochar
mass (gram), mixing time (minute), and mixing intensity
(%).Performing twenty mixing tests based on these condi-
tions provided insights into the sensitivity of the response
(surface area) to these operating parameters. After finishing
each test under each particular set of conditions, the biochar
sample was retrieved from the mixing vessel for measuring
the surface area. The analysis of pore characterization, per-
formed in four replicates using the Anton-Paar Nova 800
BET, aimed to measure the surface area through N2 gaseous
adsorption at 77°K. Before the N2 gaseous adsorption, the
samples underwent essential degassing using the internal
degassing protocol of the instrument. The degassing con-
ditions were consistent with those employed during the
Table 1. The selected factors and their respective levels
for the analysis were determined based on the sample and
experimental conditions
Levels
Mass of Mixing
Intensity (%)Biochar, g Time, min
–1 1 2 15
0 (midpoint) 6 16 45
1 11 30 75
Figure 2. Resonant Vibratory Mixer (a) and the mixing vessel
containing the hemp biochar (b)