XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 2057
with the increase of rotational frequency and the decrease
of backwash water pressure. The decrease of RV with the
increase of the rotational frequency is steeper than back-
wash water pressure, which indicates that RV responds to
the change of the rotational frequency more significantly.
As shown in Figure 12b, the EV response surface shows an
increasing trend with the increase of rotational frequency,
and the changing trend response to the feed rate is oppo-
site to it. The decreasing trend of EV is steeper with the
decreasing of the rotational frequency and slower with the
increasing of the feed rate, which indicates that EV is more
significant in response to the changes of the rotational
frequency.
The main evaluation indexes of enhanced gravity sepa-
ration of macerals are RV and EV, andthere is a negative
correlation between the two evaluation indexes through the
previous single-factor tests.When EV is between 1.1 and
1.2,the sorting effect is good, and when EV is greater than
1.2, the vitrinite is very well enriched. Setting the target
value of EV as 1.2 and the RV as the maximum value, the
optimal combination of conditions for enhanced gravity
separation of macerals was obtained as shown in Table 8.
The mean value of RV and EV obtained from the optimal
test conditions are 71.61% and 1.15, which can well realize
the low-cost, low-pollution and high-efficiency enrichment
of low-rank bituminous coal macerals. The relative errors
are only –0.43% and 1.74% compared with the predicted
values, which indicates that the predictive models are well
fitted, and verifies the accuracy of the constructed models.
CONCLUSION
With the prolongation of rod grinding time, the amount
of 0.5~0.25 mm particle size is gradually reduced,
0.25~0.125 mm particle size is accumulated in a certain
period of time.When the milling time tends to be 30 min,
0.5~0.25 mm particle size is gradually disappeared. At the
Figure 11. Variation of sorting and evaluation indicators with feed speed
Table 6. Parameter levels in the Box–Behnken design
Levels
Coded
Levels
Actual levels
A: f
(Hz)
B: P
(Mpa)
C: V
(ml/s)
Lower level –1 30 0.025 15
Middle level 0 35 0.030 25
Upper level +1 40 0.035 35
Table 7. Orthogonal test results of Box–Behnken
Std No. A: f, Hz B: P, Mpa C: V, ml/s RV, %EV
1 30 0.025 25 71.34 1.11
2 40 0.025 25 56.50 1.33
3 30 0.035 25 71.24 0.92
4 40 0.035 25 65.34 1.19
5 30 0.03 15 72.56 1.12
6 40 0.03 15 62.30 1.24
7 30 0.03 35 71.33 0.97
8 40 0.03 35 62.52 1.23
9 35 0.025 15 68.45 1.20
10 35 0.035 15 72.33 1.03
11 35 0.025 35 67.77 1.18
12 35 0.035 35 70.88 1.01
13 35 0.03 25 71.27 1.08
14 35 0.03 25 70.69 1.07
15 35 0.03 25 71.49 1.08
16 35 0.03 25 70.65 1.07
17 35 0.03 25 71.49 1.08
with the increase of rotational frequency and the decrease
of backwash water pressure. The decrease of RV with the
increase of the rotational frequency is steeper than back-
wash water pressure, which indicates that RV responds to
the change of the rotational frequency more significantly.
As shown in Figure 12b, the EV response surface shows an
increasing trend with the increase of rotational frequency,
and the changing trend response to the feed rate is oppo-
site to it. The decreasing trend of EV is steeper with the
decreasing of the rotational frequency and slower with the
increasing of the feed rate, which indicates that EV is more
significant in response to the changes of the rotational
frequency.
The main evaluation indexes of enhanced gravity sepa-
ration of macerals are RV and EV, andthere is a negative
correlation between the two evaluation indexes through the
previous single-factor tests.When EV is between 1.1 and
1.2,the sorting effect is good, and when EV is greater than
1.2, the vitrinite is very well enriched. Setting the target
value of EV as 1.2 and the RV as the maximum value, the
optimal combination of conditions for enhanced gravity
separation of macerals was obtained as shown in Table 8.
The mean value of RV and EV obtained from the optimal
test conditions are 71.61% and 1.15, which can well realize
the low-cost, low-pollution and high-efficiency enrichment
of low-rank bituminous coal macerals. The relative errors
are only –0.43% and 1.74% compared with the predicted
values, which indicates that the predictive models are well
fitted, and verifies the accuracy of the constructed models.
CONCLUSION
With the prolongation of rod grinding time, the amount
of 0.5~0.25 mm particle size is gradually reduced,
0.25~0.125 mm particle size is accumulated in a certain
period of time.When the milling time tends to be 30 min,
0.5~0.25 mm particle size is gradually disappeared. At the
Figure 11. Variation of sorting and evaluation indicators with feed speed
Table 6. Parameter levels in the Box–Behnken design
Levels
Coded
Levels
Actual levels
A: f
(Hz)
B: P
(Mpa)
C: V
(ml/s)
Lower level –1 30 0.025 15
Middle level 0 35 0.030 25
Upper level +1 40 0.035 35
Table 7. Orthogonal test results of Box–Behnken
Std No. A: f, Hz B: P, Mpa C: V, ml/s RV, %EV
1 30 0.025 25 71.34 1.11
2 40 0.025 25 56.50 1.33
3 30 0.035 25 71.24 0.92
4 40 0.035 25 65.34 1.19
5 30 0.03 15 72.56 1.12
6 40 0.03 15 62.30 1.24
7 30 0.03 35 71.33 0.97
8 40 0.03 35 62.52 1.23
9 35 0.025 15 68.45 1.20
10 35 0.035 15 72.33 1.03
11 35 0.025 35 67.77 1.18
12 35 0.035 35 70.88 1.01
13 35 0.03 25 71.27 1.08
14 35 0.03 25 70.69 1.07
15 35 0.03 25 71.49 1.08
16 35 0.03 25 70.65 1.07
17 35 0.03 25 71.49 1.08