(637c) High Temperature Sorbents for Sorption of Elemental Mercury in Packed Beds

In order to investigate sorption properties of sorbents, packed bed experiments were conducted. The focus here is on chemi-sorption of elemental mercury in air on a packed bed, consisting of kaolinite/calcite/lime mixtures (Minplus), silicon dioxide, kaolinite and lime powder. Sorption occurs at temperatures between 600°C and 1000°C and requires activation of the minerals contained within the sorbents. Mercury capture is dominated by temperature and capture on sorbents over long time scales. Freshly activated sorbent is the most effective, and deactivation of MinPlus occurs at high temperatures and long times. This activation is suspected to involve a solid/solid reaction between intimately mixed calcium oxide and silica that are both contained within the sorbent. Sorbent A had significantly greater capacity for mercury sorption than did Sorbent B, for all temperatures examined. Deactivation occurs at temperatures higher than 1000°C, and this is due to melting of the substrate and pore closure. The situation in packed beds is complicated because the bed also shrinks, thus allowing channeling and by-passing, and consequent ambiguities in determining sorbent saturation. Sorpion also requires the presence of oxygen.