Activated Carbon: What Particle Size Range Is Best For Each Application?
Contrary to popular belief, the capacity of an activated carbon does not increase no matter how small the particle size. This is because, no matter how finely a carbon is grinded, its surface area is practically not increased (the surface area is at a molecular level unaffected by mechanical methods). However, the kinetics (speed of adsorption) does increase substantially as the particle size of the carbon decreases. This means that the smaller the particle size of a carbon, the smaller the bedding required to achieve a given performance.
When to choose a smaller particle size activated carbon?
On the other hand, the smaller the particle size of a granular carbon, the greater the pressure drop and therefore the cost of achieving flow through it increases. From the above, it can be concluded that in all cases the smallest size of carbon should be used as long as the benefit of requiring a small bed is greater than the cost of circulating the fluid through it.
The increase in adsorption kinetics can be estimated with the following equation:
D = average particle diameter of the largest carbon
V = velocity of adsorption of the largest carbon
d = average particle diameter of the smallest carbon
v = velocity of adsorption of the smallest carbon