Details of good silver sulphide leaching and filtration circuit operation and instructions for sequencing and preparing for startup.
The following items must be checked before the equipment in this EXAMPLE Argentite Leaching Circuit is started.
- The leach tank agitators should be running.
- Check that the Argentite filter feed pump, drum filter, repulper and tailings sampling pump are available to start up.
- Ensure that shut-off valve in the air line to each leach tank is open.
- Ensure that the timer for the lime addition has power and that the shut-off valves in the appropriate lime lines are open.
- Check the level of cyanide solution in the cyanide day tank to ensure there is an adequate amount to start the Argentite Leach Circuit.
- Ensure there is an adequate supply of flocculant available and that the flocculant metering pump is available to operate.
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Start UP Sequence and Procedure of this EXAMPLE Silver Leaching & Filtration Circuit
- Start the Argentite drum filter, filter boot agitator and the filter repupler. Ensure that gland seal water is flowing to the repulper and adjust the flow rate with flowmeter.
- Start the tailings sampler pump and turn on the reclaim repulp water to 0.2 cubic meters per hour.
- Start the Argentite filter feed pump.
- Turn on the filter wash water to 0.1 cubic meters per hour and if closed, open the vacuum valves at the drum filter.
- When feed from the Flotation Circuit begins to enter the Argentite Leach Circuit, adjust the air rate to each leach tank with flowmeters to 5.4 cfm.
- Start lime addition timer at the first leach tank, making sure that the lime lines are not plugged.
- Start cyanide addition to the first leach tank.
- When leached slurry begins to enter the filter boot, turn on the appropriate flocculant metering pump and adjust the flow rate to the filter to 500 litres per hour.
Procedure of Silver Leaching & Filtration Circuit Normal Operation
After the Argentite Leaching and Filtration Circuit has been brought up to normal operating conditions, the operator must monitor the various process variables and alarms. The operator is also required to sample and analyse process streams and read local indicators.
The operator must routinely monitor the air flow rate into each leach tank and adjust the appropriate air flowmeter if the air rate deviates from the normal design rate of 5.4 cfm.
Like the primary leaching circuit, the protective alkalinity and free cyanide levels should be determined in the , first leach tank every 2 hours and the appropriate adjustments made to the cyanide metering pump and lime timer. Occasional checks (2 per shift) should be made on the remaining Argentite leach tanks for lime and cyanide and any adjustments made.
The operation of the small Argentite drum filter is identical to that of the larger primary and secondary drum filters. Refer to Section 6.3.3 for details.
- Ensure that the Flotation Circuit and cleaner concentrate pump has shut down before shutting down the Argentite Leach Circuit.
- Once slurry has stopped flowing from tank to tank, the air to each tank can be shut-off.
- Discontinue cyanide addition to the first leach tank.
- Shut-off the lime timer and close appropriate lime shut-off valves.
- Shut down the Argentite filter feed pump.
- Leave Argentite leach tank agitators running.
- Allow the filter boot to empty as much as possible with the filter operating. Once the filter is no longer picking up solids, allow the filter cloth to be cleaned with wash water.
- Shut off the flocculant metering pump and close the shut-off valves in the wash and repulp water lines.
- If the filter is to be down for an extended period of time, the filter boot should be drained. However, if the filter is down for a short time, the boot does not have to be drained, but the boot agitator must be left running.
- Close the shut-off valve in the air line to sampler and shut off the tailings sampling pump.
In the event of an emergency, the leach tank agitators, the Argentite filter feed pump and the Argentite drum filter can be shut down from locally mounted STOP switches or from the MCC located in the mill control room.
After the equipment is shut down, the cyanide metering pump, the flocculant metering pump and the lime timer must be shut down. Also close all shut off valves in the air lines to the leach tanks and drum filter and in the reclaim water line to the drum filter.
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