2054 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
decreases gradually. With the increase of grinding time, the
density grade ash fluctuation is not big. Among them, the
ash of –1.35 g/cm3 density level is very low, in which the
vitrinite is mainly enriched. From Figure 8b, it can be seen
that when the grinding time is 10 min, the density level of
–1.35 g/cm3 decreases, and the density level of +1.40 g/
cm3 increases. After the grinding time is more than 10 min,
the density level of –1.35 g/cm3 firstly increases and is
almost flat, and the density level of +1.40 g/cm3 gradually
decreases. The reason for this phenomenon is that when
the dissociation degree is just good, the combustible body
tends to be enriched in the low density, the ash is more
inclined to enrich in the high density level.When the dis-
sociation is too much, the particle agglomeration phenom-
enon is intensified, the mismatch phenomenon is obvious,
resulting in the decline of the ash content of the products
of the high density level.
Macerals Analysis
The density and macerals composition of the rod milled
product were analyzed and the results are shown in Table 5.
With the increase of grinding time, the vitrinite content of
–1.35 g/cm3 density class first increases and then decreases,
while the inertinite content of 1.35–1.40 g/cm3 density
class first increases and then decreases. This phenomenon
occurs mainly due to the vitrinite and inertinite in the early
stage of milling have a good dissociation, and more dis-
sociation between macerals and minerals will be carried
out and mismatch phenomenon will be produced with the
increase of grinding time. Combined with the analyses in
the previous section, the yield of –1.35 g/cm3 is the largest
at 10 min of rod milling, and the corresponding vitrinite
content is the highest. The grinding time should be reason-
ably controlled to avoid excessive dissociation between the
components to produce mismatch phenomenon.
Enhanced Gravity Separation
A single-factor testof enhanced gravity separation was car-
ried out, the key factors rotational frequencyf, backwash
water pressureP, and feed rate V were selected.The test
invariants were: slurry concentration of 10% and feed
quantity of 100 g. The coal sample used in the test was
the product after rod milling for 10 min, and its vitrinite
content was 56.53%.
Figure 8. The ash of each density level under different grinding time
Table 5. The maceral content of each density level at different
grinding time
Grinding
Time, min Targets, %
Density, g/cm3
–1.35 1.35 1.40 +1.40
5 Vitrinite 73.26 34.57 49.77
Inertinite 26.74 65.43 50.23
10 Vitrinite 75.83 31.84 44.62
Inertinite 24.17 68.16 55.38
15 Vitrinite 74.49 32.80 45.11
Inertinite 29.51 67.20 54.89
20 Vitrinite 70.78 34.70 45.99
Inertinite 34.22 65.30 54.01
30 Vitrinite 66.53 39.77 46.45
Inertinite 33.47 60.23 53.55
decreases gradually. With the increase of grinding time, the
density grade ash fluctuation is not big. Among them, the
ash of –1.35 g/cm3 density level is very low, in which the
vitrinite is mainly enriched. From Figure 8b, it can be seen
that when the grinding time is 10 min, the density level of
–1.35 g/cm3 decreases, and the density level of +1.40 g/
cm3 increases. After the grinding time is more than 10 min,
the density level of –1.35 g/cm3 firstly increases and is
almost flat, and the density level of +1.40 g/cm3 gradually
decreases. The reason for this phenomenon is that when
the dissociation degree is just good, the combustible body
tends to be enriched in the low density, the ash is more
inclined to enrich in the high density level.When the dis-
sociation is too much, the particle agglomeration phenom-
enon is intensified, the mismatch phenomenon is obvious,
resulting in the decline of the ash content of the products
of the high density level.
Macerals Analysis
The density and macerals composition of the rod milled
product were analyzed and the results are shown in Table 5.
With the increase of grinding time, the vitrinite content of
–1.35 g/cm3 density class first increases and then decreases,
while the inertinite content of 1.35–1.40 g/cm3 density
class first increases and then decreases. This phenomenon
occurs mainly due to the vitrinite and inertinite in the early
stage of milling have a good dissociation, and more dis-
sociation between macerals and minerals will be carried
out and mismatch phenomenon will be produced with the
increase of grinding time. Combined with the analyses in
the previous section, the yield of –1.35 g/cm3 is the largest
at 10 min of rod milling, and the corresponding vitrinite
content is the highest. The grinding time should be reason-
ably controlled to avoid excessive dissociation between the
components to produce mismatch phenomenon.
Enhanced Gravity Separation
A single-factor testof enhanced gravity separation was car-
ried out, the key factors rotational frequencyf, backwash
water pressureP, and feed rate V were selected.The test
invariants were: slurry concentration of 10% and feed
quantity of 100 g. The coal sample used in the test was
the product after rod milling for 10 min, and its vitrinite
content was 56.53%.
Figure 8. The ash of each density level under different grinding time
Table 5. The maceral content of each density level at different
grinding time
Grinding
Time, min Targets, %
Density, g/cm3
–1.35 1.35 1.40 +1.40
5 Vitrinite 73.26 34.57 49.77
Inertinite 26.74 65.43 50.23
10 Vitrinite 75.83 31.84 44.62
Inertinite 24.17 68.16 55.38
15 Vitrinite 74.49 32.80 45.11
Inertinite 29.51 67.20 54.89
20 Vitrinite 70.78 34.70 45.99
Inertinite 34.22 65.30 54.01
30 Vitrinite 66.53 39.77 46.45
Inertinite 33.47 60.23 53.55