Environmental Engineering Reference
In-Depth Information
The basic phenomenological model for a classical grinding circuit as depicted
in Figure 5.10 consists of a rod mill model, a ball mill model, a sump model and
pump-cyclone models.
M
T
M
T
2
PSM
Step1
particle size distribution
LC1
0.5376
LC4
HYDROCYCLONE
WF2
W
BALL MILL
Mmi
MIX WMmi1
ROD MILL
MIX PP1
Step2
MF1
LC2
WF3
DT1
100
MIX WP1
DT
density
mass flow
M
T
MT
SUMP
level
PID
50
PUMP1
ciculating load
% Solids
pump
density
noise1
noise2
Time
u1
u2
circulating load
%Solids
Automatic control
Figure 5.10
Block diagram of a conventional grinding circuit
The grinding process is represented by a multiple-input multiple-output (MIMO)
system for which the following control inputs are considered:
1. water addition to the sump box (
u
1
);
2. fresh ore feedrate to the rod mill (
u
2
);
3. pump speed (
u
3
).
The outputs are:
1. product fineness (
y
1
);
2. circulating load (
y
2
);
3. sump level (
y
3
).
Water addition to the rod mill is a constant fraction of the fresh ore feedrate
(m
3
/
h of water = ton/h of fresh ore/1.86) [24]. Sump box level is regulated with a
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