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.
|Published (Last):||16 October 2012|
|PDF File Size:||13.72 Mb|
|ePub File Size:||10.81 Mb|
|Price:||Free* [*Free Regsitration Required]|
Solution flow rate has little effect proxess stripping efficiency in the range of 1 to 4 bed volumes per hour. It then flows back into the eluate tank.
Pregnant solution is pumped from the pregnant solution tank through electrowinning cells where gold aadl recovered by electrolysis. By this time most of the gold will have been liberated from the carbon back into solution form.
Within a few hours, the alcohol is concentrated in the overhead condenser tank. Acetonitrile may be substituted for the alcohol, but its higher cost generally discourages its use.
Carbon is loaded into the acid wash column from the loaded carbon surge hopper by ellution the main inlet valve AV I Need Consulting Engineering Help. Bottom of column pressure ……… around kPa.
The Zadra process is characterized by simplicity of system design prcess operation. The thermocal heater and pump continue to operate throughout the preheat and subsequent elution stage so as to maintain desired operating temperatures.
The pressurized Zadra system has recently been the preferred process in the United States for most medium to large sized projects. Stripping efficiency decreases as flow rates are increased above 3 to 4 bed volumes per hour.
Carbon Stripping – Denver Mineral Engineers
The main drawback to the alcohol stripping process is the potential for fires. The controllers can be over-ridden to stop or rpocess a cycle or to start again, at any point. The Micron process produces a very concentrated eluant free of alcohol, with gold and silver values two or three times higher than those in the loaded carbon. The solution is then drained from the carbon until free of excess moisture.
In plant operation alcohol stripping normally requires about 12 to 16 hours to strip carbon to less than 3 oz.
The majority of pressure strip vessels are constructed from stainless steel, but many carbon steel vessels are providing satisfactory service.
Heat exchanger pressure out ……. The time required for pressure stripping is generally from 10 to 14 hours. The stripping efficiency is virtually independent of eluant water flow rate in the range of 1 to 5 bed volumes per hour. When desorption is completed, as indicated by gold solution concentration reaching a constant level in the column boiler, alcohol recovery commences.
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 procfss hopper. The extent of instrumentation is generally determined by operator preference.
There was a problem providing the content you requested
This is due to its significant cost advantage over atmospheric pressure Zadra systems. The Micron method involves pretreatment of loaded carbon, with a caustic cyanide solution followed by elution with an alcohol mixture. Glycol stripping frequently is used to increase capacity in existing Zadra operations, but economics usually favor conversion to pressure stripping if continuing operation is planned. 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.
The solution is then discarded. Preliminary tests with this pump have proved that it will pump granulated carbon at settled density over short distances. Altering of the pump speed is preferable in cases where a change in the level of one reagent only is desired on a permanent basis.
In any case the potable water system here does not cater for the running of both steps at the same time. High levels of gold in recycled eluant result in a reduction in stripping rate as illustrated typically by Figure 2 3.
The presoak solution is drained from the carbon bed and an alcohol solution is added to the vessel. Buildup of miscellaneous ions in solution after continued recycling also reduces stripping efficiency.
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 major processes include: As the carbon and preconditioning solution move into the lower section of the column the hot water eluate passing up the column elutes the gold from the carbon and flushes out the preconditioning solution to become the final eluate.
Zadra, and others, at the U. The carbon is then steam stripped to recover residual alcohol. This publication is still in print and is actually the foundation for the other stripping processes. Boyle is a full bore positive displacement slurry pump.
Gold is recovered from the pregnant strip solution by electrowinning onto steel wool. Again do not risk flooding the kiln by over flushing the line.