Pyrolysis regeneration of activated carbon used for glycerin purification

In this work, we investigated granular activated carbons Norit 1240 (AC) – initial and spent (SAC) with adsorbed impurities after purification of technical glycerin and subsequent washing with water. The aim of the work was to establish the optimal conditions for the thermal regeneration of AC at the pyrolysis unit and to quantify the adsorbed impurities in the SAC using thermogravimetric analysis (TGA). For all AC samples, the specific surface area (S), adsorption activity on iodine and mass fraction of moisture were measured. It was established by the TGA method that water is released in the temperature range of 20 – 180 °C, and glycerin – 180 – 400 °C. Spent AC contains up to 31.3 wt. % H2O and up to 37.3 wt. % C3H5(OH)3. The pyrolysis reactor was used for the regeneration of SAC samples. It was shown that after the reactivation of SACs, their specific surface area is restored to 45-94% of the initial one. There is a weak correlation between S and iodine number, R=0.64. Adsorption activity for iodine and S increase in the same row ACspent > ACregenerated > ACinitial. As a result of regeneration, activated carbons suitable for reuse were obtained.