AARL process as applied at SDGM. • Identify the key elution circuit components. • Demonstrate an understanding of carbon reactivation theory. • Demonstrate an. Request PDF on ResearchGate | Modelling of the AARL elution process | The influence of temperature on the equilibrium adsorption of gold and hydroxide ion . successful methods is the carbon-in-pulp (CIP) process. In CIP processing elution rig was commissioned to simulate industrial Zadra and AARL carbon elution.
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After stopping the elution water pump locally, reset the switch and then reset the sequence controller by: Although the sequence controllers govern the various stripping stages it is essential to monitor the plant on a regular basis so as to ensure that all equipment is operating properly and that desired temperatures are being reached and maintained within the time limitations set on the controllers. Atmospheric pressure Zadra stripping was the first commercially successful process developed for stripping gold from carbon.
Due to the timed cyclical nature of the procedure, a programmable logic controller PLCautomatic pump starting and automatic valves are generally used to time and sequence the system.
This can be confirmed by visual inspection at the pump prkcess valve. The thermocal pump operates for another two hours after the end of the carbon cool stage, this aiding the cooling down of the heater. The condensate recycle spray is stopped and the alcohol is allowed to boil out of prodess pregnant solution.
Bottom of column pressure ……… around kPa. Electrowinning of gold from the pregnant solution is done on a batch basis. The elution unit is configured like a packed bed distillation tower with a heater on the base of the column, an overhead condenser, a reflux pump and the loaded carbon functioning as the tower packing. The final eluate exits just below the top compartment as shown in Figure 5. Aaarl stripping frequently is used to increase capacity in existing Zadra operations, but economics usually favor conversion to pressure stripping if continuing operation is planned.
Additional water is injected into this line via valve AV and the carbon is carried long the line to the dewatering screen above the regeneration kiln feed hopper.
Carbon Stripping – Denver Mineral Engineers
We have a metallurgical test for every possible mineral type and treatment. Since many mines are at high elevations, with resultant low boiling points, the reduction in stripping rate eluhion be significant when compared with operations at near sea level altitudes. The extent of instrumentation is generally determined by operator preference. The solution is heated to about deg-F and pumped through the carbon stripping vessel at elutoin flow rate of about 2 Bed Volumes per hour.
The downflowingcondensate washes the gold values from the carbon particles into the boiler section below.
AARL Carbon Stripping System Operation: Elution & Electrowinning
Top of column temperature ………. It is much slower than the alternatives. This may reduce the need to reactivate carbon as frequently at some operations.
Typical strip times with glycol are 24 to 36 hours.
High levels of gold in recycled eluant result in a reduction in stripping rate as illustrated typically by Figure 2 3. Higher temperatures also accelerate the decomposition of cyanide. It may also be preferred for areas where extreme ease of maintenance and operability are a priority due to a lack of skilled manpower.
Eluant water temperature has a very significant effect on stripping efficiency. Elutoin Micron elution procedure takes advantage of the enhanced stripping rate achieved with alcohol, but confines the alcohol to the closed stripping unit. Solution bleeding is required to prevent the buildup of contaminants, which reduce stripping efficiency.
Part 3 outlines in full detail every action required on the part of goldroom personnel in order to operate the plant successfully. This is achieved at flow rates in the range of 2 bed volumes per hour operating in series flow with electrowinning cells. Carbon is loaded procesd the acid wash column from the loaded carbon surge hopper by opening the main inlet valve AV Ethanol is generally used rather than methanol.
After rinsing the carbon is pressure transferred to the elution column. When desorption is completed, as indicated by gold solution concentration reaching a constant level in the column boiler, alcohol recovery commences. A falling top of column temperature procesw the best indicator of possible trouble caused by such things as dirty heat exchanger plates, thermocal heater not operating properly or pegged inline screens.
Many methods are used commercially for recovering gold and silver from loaded elutioon carbon.
Awrl then flows back into the eluate tank. It is interesting to note that the Zadra stripping procedures researched by the USBM, originally envisioned presoaking carbon with a caustic cyanide solution followed by elution with deionized water. Preliminary tests with this pump have proved that it will pump granulated carbon at settled density over short distances.
Zadra, and others, at the U. The majority of pressure strip vessels are constructed from stainless steel, but many carbon steel vessels are providing satisfactory service. It is however very reliant upon the availability of an abundant supply of good quality water profess its water usage is far greater than that of either the Zadra system or the more recently developed solvent stripping system.
Activated carbon has long been known to exhibit a strong affinity for the extraction of gold from cyanide solutions. Barren strip solution is typically pumped through a heat recovery heat exchanger and a solution heater. This necessitates larger carbon inventories and larger equipment than other faster processes. The circuit shown in Figure 4 has the following advantages over that shown in Figure 3 and may become the prcoess process.
By this time most of the gold and silver on the carbon will have been desorbed into solution and both the carbon elutlon the solution slution have reached an optimum temperature for the subsequent elution proper.