| ENGINEERED
COPPER CONCENTRATE BINS PREVENT FLOW PROBLEMS AT
CHINO MINES
THE PROBLEM
Part of a modernization project for Chino Mines
Company involved new bins for copper concentrate,
flux, and slag. Stearns Catalytic Corp., the engineering/construction
contractor for the project, asked Jenike & Johanson
to evaluate the design of the bins and feeding
arrangement.
The design called for four 12' diameter copper
concentrate bins, two 12' diameter slag bins, and
four 7' 9" diameter flux bins, all with 35° (from
vertical) conical hoppers. An air injection system
and a pinch valve in the bottom of each bin were
intended to control flow onto an impact flow meter.
The material would then be transferred by screw
conveyor to the process.
Jenike & Johanson determined the flow properties
of the concentrate, flux and slag, each at two
moisture contents. Our tests showed that much steeper
hoppers (13° from the vertical) would be required
to ensure mass flow. Without mass flow, semi-stable ratholes could
form even when the moisture contents were low,
causing erratic flow. If the moisture content increased
above the specified value due to a disturbance
in the dryer, arches and ratholing could
be expected.
THE SOLUTION
 A
straight mass flow cone inclined at 13° from
vertical would have required a substantial increase
in headroom. The solution we proposed was to modify
the bins with a triple cone BINSERT® system
as shown in the sketch. This converted the bins
to mass flow, with no increase in headroom. Discharge
is controlled by a mass flow screw feeder whose
speed is varied by a signal from the impact flow
meter.
Although some of the materials are abrasive, screw
feeders are viable for this situation because of
the low flow rates required and because of the
enclosed design of the feeders. Our wear evaluation
showed that a reasonable wear life could be expected.
THE RESULT
Jenike & Johanson engineers performed the
structural design calculations and prepared engineering
drawings for the modification, including the mass
flow screw feeders. We reviewed the bin and feeder
construction in the fabrication shop and again
on-site after installation to ensure that the design
was properly executed. We also designed and supplied
special shutoff slide gates to be used when performing
maintenance on the bins.
The bins have been used for several years and
have operated extremely well.
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