Activated Carbon is the most important sorbent in ANG process. There are several types of activated carbon and main factors to choose the suitable one are total surface area, density, and pore volume. Total surface area is the most important one among these factors and is calculated through nitrogen adsorption on carbon in square meter per grams of carbon. This parameter can have values between 500 – 1900.
Three main types of activated carbon are used in ANG process:
ACF or Activated Carbon Fiber
PAC or Powdered Activated Carbon
and activated carbon monolith
For ACFs, methane adsorption is highly dependent on burn-off degree and the more burn –off degree increases, the more methane will be adsorbed. Furthermore, CO2 activated ACFs have higher performance than steam activated ACFs. It is also possible to increase adsorption capacity of ACFs by fluorination. In this method, ACF is introduced to pure fluorine after activation by KOH.
For PACs, methane adsorption is directly dependent to BET surface area and total porosity. These factors can change with KOH to Anthracite ratio and pyrolysis time and temperature. Experiments show that PACs adsorb more methane than ACFs at the same condition. The reason is the activation method; in chemical activation method used for PCFs, very narrow micro pores are produced while in physical or steam activation, high burn-off degree is needed to produce the same pores.
by G. Gholipur – Persian Gulf university of Iran
Director: Dr. M. Mofarahi
Translated by: P. Jowkar
Editor: M. A. Makarem