Introduction - Advanced Control and Supervision of Mineral Processing Plants - page 6

in rotary driers using a heated (oil or gas) air stream. This operation is rarely used
in base-metal processing. Niobium concentrates are rotary dried whereas graphite
concentrates are filtered on a heated belt-filter.
These unit operations are tightly coupled as is depicted in the generic flowsheet
diagram shown in Figure 1.2.

Pebbles
crusher

Cyclones

Crusher SAG Mills Ball mills

MINE

E

Regrinding

Thickening
Filtering
Stock

Cleaning
section

Rougher
section

Concentrate

Scavenger
section

Final
Tailings

Figure 1.2 Generic concentrator flowsheet and its unit operations

Clearly the operation of this processes chain will be affected by important geo-
logical factors such as those listed in Table 1.1. Unknown and unexpected changes
in these factors could translate into large variations in the main process variables.
The use of any available information about them could be used to reduce their effect
by taking some feed-forward actions. Thus, any improvement in the predictability
of the main disturbances and/or input variables will have an impact on the operation
of the whole process. Currently, there is an increasing interest in obtaining and using
information related to these factors which can be directly used in control strategies.
Some important advances are expected in the next decade.
Besides the effect of the external factors, the effect of the upstream processes on
downstream ones is also very important in this serial process structure. There are
some well-documented examples illustrating this statement. For instance, blasting
and crushing can have a significant impact on SAG mill performance, since their
throughput rate is dependent on the ore hardness and feed size distribution [11, 12].
Hardness is dependent on rock strength and mill feed size is dependent on in situ