Optimum Carbon Bed Depth 1

[htwoOtreat]

Trying to find the optimum liquid phase activated carbon bed depth for acid wash carbon (12 x 40 mesh). Is there such a thing as a maximum bed depth in a vessel. If so, what is the limiting factor (i.e. backwash flow, compaction of carbon, pressure drop, etc) ?

 

[bimr]

It will depend somewhat on the application.

 

[htwoOtreat]

Assume high purity water application (i.e. food and beverage)

 

[bimr]

If you have filtration rates of 4-6 gpm/square foot of bed area, the bed depth is typically 2 to 3 feet.

You should be replacing the bed on an annual basis. If you replacing the bed annual, there is no reason to install a deeper bed depth. A deeper bed depth will just give you a slightly higher pressure loss (~1 psi or so)across the filter with no improvement in water quality parameters.

 

[shahyar]

Possibly you are trying to remove organics. Minimum bed depth is dictated by kinetics of adsorbtion reaction. This kinetics can be investigated in the lab with your water sample(and your organics) in the operating temperature. This is a must if you want to provide high purity water. In non critical applications, you can go with bimr rule of thumb: 2-3 ft depth.
The maximum depth can be calculated by Ergun formula to have a pressure loss around 5 psig for a clean bed.

 

[htwoOtreat]

Thanks. Do you happen to have a good reference that presents the Ergun formula for this calc ?