Coal-Based activated carbon: how to size a fixed bed

Buyers comparing coal-based activated carbon usually arrive with the same question: which form does this duty actually need? The answer follows from the vessel and the contaminant, not from the headline iodine value alone.

Screened granules for fixed beds and continuous columns, with the hardness to survive backwashing. Granular carbon suits fixed beds and continuous columns: the mesh range sets both the pressure drop and the contact time, so specify the range your vessel is designed for. Backwashing is normally tolerated because of the hardness of the material.

For the coal-based series the reference ranges are 500-1100 mg/g iodine value and 650-1000 m2/g BET surface area, produced by physical or chemical activation. Compare grades inside one series with caution: iodine value is a microporosity indicator, so a grade with a lower iodine value can still outperform a higher one where larger molecules dominate. Watch for a rising outlet concentration, a colour or odour change, or an increasing pressure drop. Any of these indicates the bed is loading up; arrange a test or a replacement before the outlet goes out of specification. Thermal regeneration and acid washing are the usual recovery routes.

Before contacting a supplier, write down the medium, the flow rate or concentration, the target outlet quality and the particle size your equipment accepts. Those four points are what turn a general enquiry into a usable quotation.