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AARL ELUTION PROCESS PDF

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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Pressure stripping columns are normally sized with a height to diameter ratio of about 4 to 1. The loaded carbon and hot preconditioning solution move down the top section of the column together. Internal solution distributors and collectors are used to provide even flow of solution throughout the carbon bed. The carbon is then steam stripped to recover residual alcohol.

This offers the potential of either designing for multiple stripping cycles each day and reducing equipment sizes in new plant design, or increasing daily capacity in aarll mills by stripping on additional shifts each day. Top of column temperature ………. The Ok Tedi plant was seldom operated under the design conditions listed above.

This information is displayed on the control cubicle.

After rinsing the carbon is pressure transferred to the elution column. Preliminary tests with this pump have proved that it will pump granulated carbon at settled density over short distances. The major processes include: This can be confirmed by visual inspection at the pump or valve.

High pressure operation is accomplished by means of a high pressure solution pump and a stripping column pressure control regulator. After filling, the main valve AV is closed and dilute hydrochloric acid is injected into the bottom of the column via valve AV This stage continues until five bed volumes of water have passed through the column 2.

AARL Carbon Stripping System Operation: Elution & Electrowinning

There are numerous variations to, and combinations of, the basic processes as illustrated by the following:. The AARL process should definitely be considered for large peocess with sophisticated operators. Wait for this before stopping the transfer by stopping the elution water pump locally. This necessitates larger carbon inventories and larger equipment than process faster processes. Stripping temperature is the most significant operating parameter so solutions are kept as close to boiling temperature as is practical.

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The barren solution is then pumped out of the eluate tank into the process water tank. The Zadra process is characterized by simplicity of system design and procesx.

The majority of pressure strip vessels are constructed from stainless steel, but many carbon steel vessels are providing satisfactory service. Gold is recovered from the pregnant strip solution by electrowinning onto steel wool.

To alleviate this problem, most operations routinely orocess a fraction of their strip liquor inventory and replenish with fresh solution. In practice the feed system to each column had a limit of 36 tonnes per day.

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Heat exchanger pressure out ……. This publication is still in print and is actually the foundation for the other stripping processes. Displaced water flows out of the top of the column through the inline filter, along the pregnant solution line to the heat exchanger to exit via valve AV into the eluate tank.

The vessel was oversized and hence reducing eluate flow was not recommended to increase final eluate grade because of the possibility of channelling. Methanol, ethanol, and Isopropanol were all found to increase the gold desorption rate. The gold depleted solution is then reheated and recycled to the carbon bed for reuse see Figure 1. 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.

Continued research at the USBM revealed that pocess Zadra process stripping rate could be increased greatly by stripping at higher temperatures 4. Heat is then applied to the base of the desorption vessel. The acid rinse step 05 is currently set for 2. Most columns are operated with upflow aaarl solution, but some plants have selected to elute by downflow.

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One bed volume thirty minutes into the elution stage the eluate pump is started and pregnant solution from the eluate tank, is pumped up into the electrowinning cell on the first floor of the goldroom.

Activated carbon has long been known to exhibit a strong affinity for the extraction of gold from cyanide solutions. Changes in the duration of soaking time, for most carbons, has little effect on stripping efficiency. Control of the procese of solution purged from the system is done either on a routine scheduled basis or by monitoring stripping efficiency and bleeding as efficiency drops.

The advantages and disadvantages of each procedure are discussed. Automatic solution temperature control and column back pressure control are the minimum automation required. The solution procees heated to about deg-F and pumped through the carbon stripping vessel at a flow rate of about 2 Bed Volumes per hour. Solution bleeding is required to prevent the buildup of contaminants, which reduce stripping efficiency.

AARL Carbon Stripping System Operation: Elution & Electrowinning

The major processes include:. The quality of water used has a substantial effect on stripping efficiency with the AARL procedure. Gold is recovered from the pregnant eluant by electrowinning and the barren eluant is discarded See Figure 3. Operating temperature limits of deg-F are widely specified because of temperature limitations of the butyl rubber lining material utilized to line the strip vessel.

Solution is circulated through electrowinning and back to the pregnant solution tank until acceptable barren levels are achieved.