GPSA Ch. 21
| Carbon Type | H₂S Capacity | Mercury | BTEX | Cost |
|---|---|---|---|---|
| Virgin | 10% | 5% | 15% | $0.80/lb |
| Impregnated | 20% | 12% | 12% | $1.50/lb |
| Catalytic | 25% | 8% | 18% | $2.00/lb |
Adsorption Principle:
Activated carbon removes contaminants through physical adsorption (van der Waals forces) onto the carbon’s high surface area (800–1200 m²/g). Impregnated carbons add chemisorption via chemical reaction with the impregnant (KOH, NaOH, or metal oxides) for enhanced H₂S and mercury removal.
Mass Transfer Zone (MTZ):
Where v = superficial velocity (ft/min), ts = stoichiometric time. The MTZ is the active adsorption zone moving through the bed. Lead-lag configurations ensure the lag bed captures breakthrough from the lead bed.
Breakthrough Curve:
Breakthrough occurs when the MTZ reaches the bed outlet and contaminant concentration rises above the outlet target. Design bed depth must exceed the MTZ length to ensure adequate contact time. Minimum contact time of 2–5 seconds is required for effective adsorption.
Understand activated carbon adsorption, bed sizing principles, and contaminant removal mechanisms