Granules Activated Carbon
Granular activated carbons are mostly made from Coconut Shells on petroleum Coke, bituminous coal or lignite. Granular activated carbon is used in continuous Process in areas like water treatment (drinking & effluent water), removal of mercury from effluents or alkali cells, solvent recovery, gold recovery, removal of odor, Gas masks, as catalyst carrier, for decholorination of water, purification & separation of gases, kitchen hoods, dry cleaning etc.
The granules activated carbon (GAC) is milled and sieved to achieve
particles in the range of 0.2 to 5 mm.
Typically the drinking water industry uses
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8 x 30 mesh (effective size of 0.80-1.0 mm),
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12 x 40 mesh (effective size of 0.5 - 0.7 mm).
GAC is used in both liquid and gas phase applications.
Application
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Wastewater
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Oil refining
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Sugar refining
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Gold recovery
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Soil stabilization
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Drinking water
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Bottle beverage plant
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Air filtration
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Free Chlorine Removal
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Organic Matter removal
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Odour Removal
Activated carbon For water treatment
The water treatment process involves dosing PAC to the water, or passing the water through a GAC bed.
PAC is used in water treatment plants to control the taste and odor and / or for the elimination of organic substances.
it comes in two main forms:
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Powdered activated carbon (PAC) – pulverized ground material, where most of the particles have a diameter <0.18 mm (80 mesh).
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Granular activated carbon (GAC) – has irregular shape and a typical diameter between 0.2 and 1.5 mm.
It is applied as a dry powder or as slurry.
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Dry powder – dosing with dry feed equipment for dosing dry materials. It is used for low-dose applications and for infrequent applications.
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Slurry – dosed with metering pumps. It is used when PAC is added more frequently and when high doses are required.
GAC is used mainly as post-filtration, after a conventional filtration process, or inside a granular medium filter, where some part of the filter bed is replaced by GAC.
In the post-filtration configuration, the GAC filter receives high quality water, because the water has already passed through the entire treatment process.
Particle size:
Activated carbon is commonly available in
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8 by 30 mesh (largest)
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12 by 40 mesh (most common)
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20 by 50 mesh (finest).
The finer mesh gives the best contact and better removal, but at the expense of higher pressure drop. A rule of thumb here is that the 8 by 30 mesh gives two to three times better removal than the 12 by 40, and 10 to 20 times better kinetic removal than the 8 by 30 mesh.
Flow rate:
Generally, the lower the flow rate, the more time the contaminant will have to diffuse into a pore and be adsorbed. Adsorption by activated carbon is almost always improved by a longer contact time. Again, in general terms, a carbon bed of 20 by 50 mesh can be run at twice the flow rate of a bed of 12 by 40 mesh, and a carbon bed of 12 by 40 mesh can be run at twice the flow rate of a bed of 8 by 30 mesh. Whenever considering higher flow rates with finer mesh carbons, watch for an increased pressure drop!
Temperature:
Higher water temperatures decrease the solution viscosity and can increase die diffusion rate, thereby increasing adsorption. Higher temperatures can also disrupt the adsorptive bond and slightly decrease adsorption. It depends on the organic compound being removed, but generally, lower temperatures seem to favour adsorption.