Flow Rate Computation: Automatic Dumping Hoppers
FLOW RATE COMPUTATION
AUTOMATIC DT]MPING HOPPERS
INTROD UCTION: Some of the problem s encountered in obtaining acceptable product from grinding operations are discussedinthis paper. In particular,the application of an EAI PC-12 Process Control
Computer to this problem is considered, and a description of some
initial steps towards improvements in system operation are given.
\J
As a rule, acceptable product, fines, and oversize
particles are formed in the grinding of materials.
Often, however, grinding mills have widelyvarying
charasteristics,
and the grindability of feed and
oversize recycle changes drastically. In such cases,
the efficiency of grinding (aceeptable product per
unit of energy input) can fluctuate beyond reason.
As an initial step in improving the tlpical operation of such a system, an operatorts guide along
the following lines is considered.
v
It is assumed that three (or more) products are
separated by size and fed to hoppers which dump
automatically when certain weights are reached.
A single hopper dumps every minute or so. The
average rate of production over that interval for
that product is then
R. =w./t.
-'*$r-l
-rl
n
-l
t------ll
tIn
'--------------1
;
|
Figure 1: Dumped Hopper Cireuit
where R. =ov€r&go rate, #/}nr.
Wi =weight at which hoPPer dumPs, #
t.
I
=time since last durrping, hr.
A pulse (contact closure) is generatedbythedumping mechanism and this pulse is in turn used to
control an analog computer circuit.
P r i n r e di n U . S . A . 1 0 3
A simple analog circuit is thus tleveloped to compute Ri values artd the fractional rate ofproduction
of acceptable particles, R;/(>Ril. Figure 1 illustrates such a computing circuit. The immediate
displays of rates and fractional rates provides the
mill operator with good information as to what
effects he is causing by adjusting the mill operation.
@ El c c tr c ni c As s oc i oi es, I n c . 1 9 6 3
Al l R i ghr s R es er v ed
Bul l eti n N um ber ALM P6 3 6 9 -I o b