Thermal Equipment | Carbon Regeneration Kilns
The largest application for the Ansac HK Series indirect fired kilns is in the field of carbon regeneration. Activated Carbon is used in numerous industries as an absorber of contaminants from waste water to slurries. The gold industry in particular utilises carbon to concentrate gold from a cyanide leached slurry solution into a highly concentrated electrowinning feed.
Unfortunately, gold is not the only chemical species absorbed in the slurry tanks. Other contaminants; particularly organic volatile materials are also captured. These contaminants, or foulants, actually decrease the number of sites or locations for the gold to be absorbed onto.
Often, after only one cycle through the slurry tanks, the activated carbon will drop to 30-50% of the activity of fresh new carbon. This effect is cumulative and after several cycles, the ability of the carbon to capture gold will almost be nil.
Activated carbon must be reactivated or regenerated back to as close to as new condition as possible for the process to be efficient . Chemically, if the carbon is exposed to a steam atmosphere at temperatures greater than 500° C, the foulants will begin to decompose through steam reforming. Most foulants are volatiles within the structure and will begin to break down.
In practical terms, three key factors are necessary to regenerate carbon:
- Process Atmosphere; and
- Residence Time.
Overseeing the carbon circuit, maintaining inventories and reducing overall operating costs is commonly known as carbon management. The effects of poor management on overall plant performance can be crippling.
Carbon movement is increased to compensate low loadings causing bottlenecks and stress on existing equipment.
Carbon turnover is increased due to fresh carbon being needed sooner increasing total costs.
Gold losses through the tailings stream increases and revenue is eroded.
Fundamental to good carbon management is carbon reactivation and the equipment used in regeneration. The Ansac HK Series Kiln maximises the performance of the carbon circuit.
The Ansac HK Series of kilns offer unparalleled carbon regeneration whilst keeping the operating costs to a minimum.
Carbon at 650°C exposed to air will combust. Regeneration however requires a special atmosphere of steam and inerts in order to prevent combustion and remove volatiles and foulants.
Conventional thought would suggest that steam needs to be injected at the discharge end to run counter-current to the carbon and to be discharged out of the feed end.
This concept is energy inefficient – heating the steam twice. Additionally research has shown that the process is not limited by the concentration of steam, but by mass transfer of steam in carbon. In practical terms this refers to the time required to move the mass through the incredibly tortuous pores in each grain of carbon.
Using this information Ansac has developed a kiln around the principle of co-current self generating steam.
Activated carbon, due to its incredibly porous nature, retains almost its entire weight in water. Even when carbon feels dry, it can still contain well over 35% moisture.
With the HK series kiln pre-heater in operation, the carbon still contains more than sufficient water for the regeneration process as it is fed into the kiln. The water evaporates in the initial stages of the heat tube, forming super heated steam which then reacts with the organic compounds in the carbon.
20 years of experience in carbon regeneration has made Ansac the industry standard in carbon regeneration and has led to improvements that have made Ansac’s unit the most capital and operating cost effective options in the market.
Ansac offers full commissioning and after sales support and believes in developing a long term relationship with our clients