Page 57 - HUB-4 Magazine Issue 82
P. 57

 Quarrying News
  As the aggregate exits the hull, it receives a final rinse to remove any 0-5mm carry over, and this is sent to the integrated sump. All the water used in the scrubbing process is contained in a closed loop, and the dirty water is collected in the integral sump. From here, it is pumped back along the extended conveyor to the Aggresand sump, where it enters the sand washing process. What remains is a pile of clean, marketable aggregate in distinct-sized stockpiles and a neat pile of trash and organics.
Flocculant dosing unit
The plant uses an FDU3000 flocculent dosing unit. The 3000- litre capacity unit is a stainless-steel construction split into three separate tanks, a mixing tank, maturing tank and storage tank.
During flocculant preparation clean potable water is pumped from a water storage tank situated outside the control room. Simultaneously dry flocculant powder is fed into the pressurised water entering the mixing tank flow by an auger mounted in the flocculant hopper. The flocculant solution is then thoroughly mixed using a mixer in the mixing tank.
Premixed flocculant is displaced and overflows from the mixing tank into the maturing tank via a weir, where it is further mixed and allowed to mature for between 45 -60 minutes.
Flocculant in the storage tank is then pumped via a mono pump into the slurry feed pipeline just before the static mixer, where it thoroughly mixed with the slurry feed, before entering the thickener.
The settling rate of the solids within the slurry are continuously monitored automatically by the dosing control unit. This allows the control panel to monitor and adjust the amount of flocculant used and therefore optimise consumption.
Deep Cone Thickener
This is where the dirty water, now dosed with flocculant, enters into the centre feed well. Immediately you can see the floc working, causing the particles of silt & clay bind together and sink to the bottom of the DC220. Here you can see the clarified water weiring over the troughs and channelled into a below ground water storage tank. The thickened sludge is compressed in the deep cone and the volume of sludge in the thickener is controlled via this sensor. When the level reaches its set point the sensor sends a signal to the control system which automatically opens the discharge valve. The thickened sludge is then transferred to the pond under gravity This being a key advantage of the deep cone thickener, not requiring a sludge pump. A further advantage is the fact that the sludge can reach a higher solids ratio, on average 50% solids, meaning that a greater level of water in recovered / recycled. At the exist position of the Deep cone, you can see the valve arrangement, we install flush out points. This allows the operator to and easily flush out any blockages safely and quickly.
The thickened sludge is piped to the settlement ponds where is contained and easier to handle.
Central control room
TWS also incorporated a central control room with insulated panels lighting and heating. This is where the main panels and switch gear systems are
located. The control panels have a touch screen system that allows operators to drill down into the system and look at an individual machines performance to optimise plant efficiency. Should alerts arise, these are highlighted on the large display screen and can be identified and rectified quickly.
The system also allows for Terex engineers to remotely dial in for troubleshooting and fault diagnostics. They can help with plant performance and change settings if feed material change or support are needed.
End to end
The plant was designed with custom features to meet Keohane's specific needs.
The company provided a full turnkey solution that leveraged its wide product portfolio. All of the equipment used in Keohane's Brinny plant comes from TWS's product line. TWS's decades of in-house experience helped ensure its equipment is applied properly and efficiently. September/October - Issue 82
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