(123g) High Temperature Adsorption of Mercury on Non-Carbon Based Sorbents

A bench scale disperse phase, entrained-flow reactor, was employed to investigate elemental mercury (Hg) adsorption on non-carbon based sorbents. The major parameters varied for the Hg adsorption test were reaction temperature, sorbent feeding rate, gas compositions, and mineral composition of sorbents. The sorbent receiving the greatest attention was MinPlus, an engineered sorbent produced from a process which uses paper recycling wastes as a feedstock. Hg adsorption tests were performed of a temperature range of 600 - 1000°C and at various sorbent feeding rates (< 7g/hr). Since the Hg adsorption was occurred at high temperatures and the adsorption efficiency increased with increasing temperature, the reaction between sorbents and Hg should be considered to be chemisorption. Overall Hg capture was achieved at over 90% at 900-1000 °C, and could be divided into two mechanism; in-flight capture and capture through reactor wall effects involving deposited particles.

Surface analysis of spent sorbent (XRD, SEM-EDS) showed that high temperature mineral transitions, and the ensuing sorbent compositions could enhance the Hg sorption mechanism (in-flight and wall effect). Gas compositions such as CO2, H2O, HCl and O2 could have a significant effect on Hg adsorption, which appears to require an oxidation step. Furthethermore, interactions with types of fly ash also could affect the Hg adsorption efficiency, where bituminous coal derived fly ash showed higher Hg capture than that from mixtures involving PRB (Powder River Basin) fly ash.