XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 3811
immediately before the specific test. A detailed description
of all HPGR tests is prepared in Table 1
The initial gap width in the press was set at 4 mm, and
the speed of rolls 16 rpm (0.4 m/s). After each single test,
only the central product of HPGR was collected for further
analyses, and it constituted approximately 70% of the feed
weight.
The crushing products were analysed to determine
the Bond working index. The Bond index (Wi) was deter-
mined according to the procedure worked out by Bond
(Bond, 1961). Individual tests were performed in a ball mill
with dimensions 305 mm × 305 mm, filled with 20.1 kg
of grinding medium (steel balls) with different diameters
ranging from 15.2 to 38.1 mm, and approximately 0.7 dm3
of the unified material from the input feed After each turn
of grinding, the mass of material under 0.1 mm has been
removed from the grinding product and the remaining
sample Q2 was replenished with the portion of material
Q1 from the unified input feed (Figure 2).
RESULTS OF INVESTIGATIONS
Investigations include analysis of HPGR product fineness
and analysis of Bond working index, which was performed
for all HPGR products. Figure 3 presents an exemplary set
of particle size distribution curves for the HPGR product
crushed at the press force F =160 kN was presented in
Figure 3.
The code of products is provided in Table 1. In gen-
eral, the particle size distribution (PSD) of the individual
crushing product was finer together with the increase of the
pressing force F. The impact of the moisture content (M)
appeared to be lower for higher values of F, compared to F =
100 and 130 kN. The effects of the fineness of the moisture
content on the product are significant when results for M
=0% and 2% are compared. A further increase in mois-
ture results in relatively lower increase in fineness. For F
=130 kN, in turn, increasing of product fineness is to a
major extent proportional to the increase in the value of M.
To make more detailed evaluations, specific values of
comminution ratios Sx were calculated for each HPGR
product according to Equation (1).
S d
D
x
x
x =(1)
In equation (1), x denotes the characteristic particle, that
is, average—50% (d50 and D50), 80% (d80 and D80) or
95% (d95 and D95). Referring to that we can talk about
average comminution degree (S50), eighty per cent com-
minution degree (S80) or a maximum comminution degree,
respectively. For the purpose of analysis carried out in the
Table 1. Characteristics of HPGR Crushing Experiments
Denotation of HGR
Experiment
Pressing Force
F, kN
Moisture Content
M, %
P1 100 0
P2 100 2
P3 100 4
P4 130 0
P5 130 2
P6 130 4
P7 160 0
P8 160 2
P9 160 4
Figure 2. The procedure of Determination of the Bond
Working Index Wi
immediately before the specific test. A detailed description
of all HPGR tests is prepared in Table 1
The initial gap width in the press was set at 4 mm, and
the speed of rolls 16 rpm (0.4 m/s). After each single test,
only the central product of HPGR was collected for further
analyses, and it constituted approximately 70% of the feed
weight.
The crushing products were analysed to determine
the Bond working index. The Bond index (Wi) was deter-
mined according to the procedure worked out by Bond
(Bond, 1961). Individual tests were performed in a ball mill
with dimensions 305 mm × 305 mm, filled with 20.1 kg
of grinding medium (steel balls) with different diameters
ranging from 15.2 to 38.1 mm, and approximately 0.7 dm3
of the unified material from the input feed After each turn
of grinding, the mass of material under 0.1 mm has been
removed from the grinding product and the remaining
sample Q2 was replenished with the portion of material
Q1 from the unified input feed (Figure 2).
RESULTS OF INVESTIGATIONS
Investigations include analysis of HPGR product fineness
and analysis of Bond working index, which was performed
for all HPGR products. Figure 3 presents an exemplary set
of particle size distribution curves for the HPGR product
crushed at the press force F =160 kN was presented in
Figure 3.
The code of products is provided in Table 1. In gen-
eral, the particle size distribution (PSD) of the individual
crushing product was finer together with the increase of the
pressing force F. The impact of the moisture content (M)
appeared to be lower for higher values of F, compared to F =
100 and 130 kN. The effects of the fineness of the moisture
content on the product are significant when results for M
=0% and 2% are compared. A further increase in mois-
ture results in relatively lower increase in fineness. For F
=130 kN, in turn, increasing of product fineness is to a
major extent proportional to the increase in the value of M.
To make more detailed evaluations, specific values of
comminution ratios Sx were calculated for each HPGR
product according to Equation (1).
S d
D
x
x
x =(1)
In equation (1), x denotes the characteristic particle, that
is, average—50% (d50 and D50), 80% (d80 and D80) or
95% (d95 and D95). Referring to that we can talk about
average comminution degree (S50), eighty per cent com-
minution degree (S80) or a maximum comminution degree,
respectively. For the purpose of analysis carried out in the
Table 1. Characteristics of HPGR Crushing Experiments
Denotation of HGR
Experiment
Pressing Force
F, kN
Moisture Content
M, %
P1 100 0
P2 100 2
P3 100 4
P4 130 0
P5 130 2
P6 130 4
P7 160 0
P8 160 2
P9 160 4
Figure 2. The procedure of Determination of the Bond
Working Index Wi