A system 26 for removing elemental mercury or mercury compounds handles carbonaceous sorbent 28 of a starter batch stored in a silo 30 in an agglomerated state. The sorbent 28 is fed by a feeder 32 to a separation device 34, which comminutes (if necessary) and de-agglomerates the sorbent particles 28 to their primary size distribution. This device 34 may be a particle-particle separator or a jet mill, where compressed air or high-pressure steam is the energy source. The de-agglomerated sorbent 28 of a contact batch created from the starter batch is conveyed by an airsteam for injection at a contact location 66 in a flue gas duct whereat carbonaceous sorbent of the contact batch adsorbs mercury from the flue gas. (FIG.1).