Babei It may also be preferred for areas where extreme ease of maintenance and operability are a priority due to a lack of skilled manpower. During the elution cyclewater is drawn from the potable water tank and pumped through the heat exchanger via valve AV into the eluution. Solution bleeding is required to prevent the buildup of contaminants, which reduce stripping efficiency. Continued research at the USBM revealed that the Zadra process stripping rate could be increased greatly by stripping at higher temperatures 4. Likewise it should be remembered that the controllers will not operate if a local stop switch is depressed.
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Automatic or manual mode selection by external signal. Unit Number Setting Switch. Complete log sheet by recording times and volumes of water used during this sequence. The cycle will then start again from the point at which it was interrupted. The pregnant solution or eluate, flows into the eluate tank.
The transfer pump will still be operating. Sequence is ended. Fill in the relevant information on the log sheet. Make sure that the manual valve on the acid container is open. Record the time, the level of acid in the container and the reading for potable water off the meter by the potable water tank, on the goldroom log sheet.
Check to see that the acid pump is running. The sequence controller will automatically take the sequence through the soak step 04 and the rinse step At the end of step 5 the alarm will sound. Check the pH level of the solution from the sample point at the top of the column. Whilst the carbon is being transferred take samples from the transfer line sample point, every five minutes.
Make sure that the filter bag has no holes in it and that the pliable band fits snugly into the ledge inside the filter housing. Also ensure that the steel ball has been put back inside the bag. Close the accumulator drain valves and also the manual back up valve on the barren carbon transfer line. Reagent Addition and Preheat On the log sheet, note the meter readings for the caustic, and cyanide pumps and also that of the potable water supply.
During the addition of reagents step 02 visually check that the pumps are operating and also record the meter readings immediately after the pumps stop. Should the output of either pump be drastically short of the desired amount Presently litres of cyanide and litres of caustic immediately press one of the pump stop switches and then reset it, This action will prevent the sequence controller from continuing on through the elution programme.
Close auto valves AV and AV manually. The controller will automatically continue on with the preheat cycle step Check to ensure that the thermocal heater is operating. Monitor the preheat step regularly and record both temperatures and pressures on the log sheet every half hour, the desired top of column temperature at the end of the preheat step varies with weather conditions, but during the cooler months it should reach QO0 approximately.
Elution After preheat the controller will automatically go into the elution step Start the electrowinning cell after the first bed volume -thirty minutes running time. After one hour in the elution step 06 the following operating parameters are considered desirable. Transfer of Barren Carbon to Regeneration Kiln Hopper Open the back up manual valve on the barren carbon transfer line. Back flush the carbon transfer line into the quench tank by attaching a hose to the minsup coupling behind the dewatering screen above the feed hopper.
This step is only necessary if the previous lot of barren carbon was transferred directly into the quench tank. Close the carbon delivery valve above the quench tank. Make sure that the dewatering screen is clean. Do not over flush as this could flood the kiln. Should this decrease markedly, stop the elution water pump locally and flush the carbon transfer line again.
Wait for this before stopping the transfer by stopping the elution water pump locally. Again do not risk flooding the kiln by over flushing the line. After stopping the elution water pump locally, reset the switch and then reset the sequence controller by: i On the sequence controller pane 1, switch the L. Electrowinning One bed volume thirty minutes after the commencement of the elution step 06 the electrowinning cell may be put into operation.
Start Up Procedure Check the valves by the eluate tank. Shut the drainage valve at the base of the cell. Open the input valve partly. Make sure that the fume exhaust fan is operating. Start the pump — it will not start if the local switch outside the goldroom door has been left isolated. Open fully the input valve. When there is a flow over the weir at the discharge end of the cell, switch on the rectifier and adjust the volts to no more than 5. Regulate the input valve so that the eluate level is about half way up the overflow outlet of the cell.
Monitor the cell regularly to check on both eluate level and volts. Check the pH and cyanide levels. Tell the night shift personnel that the cell is operating. If there is a power failure, the pump will need to be restarted at the local switch. Shut Down Procedure Take an eluate sample.
Stop the pump — reset the switch immediately. Open the dump valve on the line leading to the eluate tank. When the cell is half empty, switch off the rectifier and turn the control knob back to zero. Shut or open the appropriate valves by the eluate tank. Before pumping out the spent eluate to the process water tank, advise both the intensive cyanidation operator and the shift foreman.
When the tank is pumped out, the eluate pump should stop and the low level indicator will come on on the control panel. Change the valves by the eluate tank back to the positions required for electrowinning.
Points to Watch High eluate level in the cell could indicate: i The cathodes are blocked with slime or fully loaded. Low eluate level in the cell could indicate: i The pump is faulty. Incorrect voltage level could indicate: i Too much resistance in the cathodes, i. Eluate is poisonous — wear gloves when taking a sample or handling the cathodes.
Do not linger by the cell even when the fume exhaust fan is operating.
Pyrometallurgy: Roasting, Smelting, Refining & Electrowinning
Jular Automatic solution temperature control and column back pressure control are the minimum automation required. Pfocess are numerous variations to, and combinations of, the basic processes as illustrated by the following:. When the curve flattens out, the rinsing is sufficient even if the pH is only 4. Changing of the dosing time in the stripping sequence step 02 results in the changing of the levels of both NaCN and NaOH as the same timer controls both pumps. Selection of design and operating flows is made on the basis of equipment costs and time constraints.
AARL ELUTION PROCESS PDF
AARL Carbon Stripping System Operation: Elution & Electrowinning