Effects of heat treatment and acid washing on properties and reactivity of charcoal

• The density, surface area and reactivity of charcoal were greatly improved upon heat treatment at elevated temperatures.
• Additional improvement in charcoal's reactivity was obtained by performing the acid leaching before the calcination.
• Addition of the pretreated charcoal to the anode recipe did not deteriorate the reactivity of the produced anode.

Due to its highly amorphous carbon structure and abundant minerals content, as received charcoal possesses several undesirable characteristics such as low density and electrical conductivity in addition to its extremely high air and CO2 reactivities. These disadvantages are the most challenging obstacle for using this material as an alternative for petroleum coke in anode manufacturing processes. In this work, heat treatment under inert conditions was found to be a useful method to improve the molecular structure of charcoal, during this process continuous growth of the more ordered carbon structure at the expense of the amorphous forms was detected using XRD and Raman spectroscopy. Consequently, an improvement in the physical properties and the reactivity of charcoal occurred. In addition, acid washing was employed to eliminate the inorganic minerals of the charcoal. It was found that combination between acid washing and heat treatment produced charcoal having lower reactivity and better physical properties. The burning behavior of the pretreated charcoal samples was found to be comparable to that of calcined petroleum coke. Accordingly, using the pretreated charcoal to substitute up to 10% of coke in the anode recipe did not show a negative effect on the anode's reactivity to both air and CO2.