![]() More recently, there has been a renewed focus on better carbon regeneration, as part of the overall focus on improved carbon management.ĭuring adsorption, many organic and inorganic adsorbates can accumulate within the porous structure of activated carbon. While there is often no observed immediate impact, over time a significant degradation in CIL performance will occur. Often operations will cease thermal regeneration for an extended period due to equipment failure. Lack of focus in this atva often leads to underinvestment in good equipment, poor operating practices (insufficient temperature/residence time/steam), and poor maintenance. In general, process operations manage the acid washing and elution stages well however, the thermal regeneration process is often problematic. Thermal regeneration to remove organic adsorbates and refresh active sites.Elution to remove gold, silver, and base metals.Acid washing to remove inorganic adsorbates.Obtaining a good kinetic activity for a barren carbon is a function of 3 steps: A minority of operations to achieve good regeneration (>70% of new carbon), demonstrating that a satisfactory outcome is possible with proper equipment and procedures. Experience over the past 30 years suggests that on average regenerated carbon has a kinetic activity no better than 50% of new carbon and often only 20-40%. Despite this knowledge, gold processing operations have generally not been particularly good at regenerating barren carbon. The importance of returning barren carbon to good kinetic activity has long been known. ![]() The average carbon activity in a circuit is mainly a function of the efficiency of the carbon regeneration process (i.e. Lower carbon activity will result in higher carbon inventories in the circuit, lower gold loadings on the carbon, and higher soluble gold losses from the circuit. This paper will focus on the design considerations in the acid wash and thermal reactivation circuits, although it should be noted that all three operations must be operated efficiently to ensure proper carbon reactivation and the resultant low soluble gold losses from the cyanidation circuit.Īs noted previously, carbon kinetic activity is an important factor in the efficient operation of a CIP circuit. The main unit operations within the reactivation circuit are acid washing, elution and thermal reactivation. Since each circuit will be treating a unique solution, which will result in unique carbon fouling problems, the reactivation circuit design must consider several variables, which includes the preference of the plant operator. The carbon reactivation circuit is series of unit processes designed to restore the activated carbon’s ability to recover precious metals from cyanidation circuit solutions. Thennal activation is preceded or followed by exposure to hydrochloric acid to remove inorganic precipitates such as carbonates. Regeneration generally consists primarily of thermal activation in a rotary kiln at around 650 C in steam to remove organic debris. ![]() Consequently, the performance of the activated carbon decreases unless it is regenerated. Other compounds such as calcium and magnesium carbonate commonly precipitate on the carbon surface and restrict gold adsorption access. Organic compounds tend to adsorb readily on the hydrophobic activated carbon, which reduces site availability for gold cyanide. In normal process streams activated carbon is exposed to a variety of chemicals. products/pyro-process/carbon-regeneration
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