Catalyst Additives to Enhance Mercury Oxidation and Capture

Cannon, Jared W. ; Gale, Thomas K.

Southern Research Institute

关键词: Materials Testing;    Coal;    01 Coal, Lignite, And Peat;    Oxidation;    Catalysts;   

DOI  :  10.2172/896094
RP-ID  :  None
RP-ID  :  FC26-04NT41900
RP-ID  :  896094

美国|英语

来源: UNT Digital Library

【 摘 要 】

Preliminary research has shown that SCR catalysts employed for nitrogen-oxide reduction can effectively oxidize mercury. This report discusses initial results from fundamental investigations into the behavior of mercury species in the presence of SCR catalysts at Southern Research Institute. The testing was performed at Southern Research's Catalyst Test Facility, a bench-scale reactor capable of simulating gas-phase reactions occurring in coal-fired utility pollution-control equipment. Three different SCR catalysts are currently being studied in this project--honeycomb-type, plate-type, and a hybrid-type catalyst. The catalysts were manufactured and supplied by Cormetech Inc., Hitachi America Ltd., and Haldor-Topsoe Inc., respectively. Parametric testing was performed to investigate the contribution of flue-gas chemistry on mercury oxidation via SCR catalysts. Methods and procedures for experimental testing continue to be developed to produce the highest quality mercury-oxidation data. During this past quarter, it was discovered that long periods (12 - 24 hours) are required to equilibrate the catalysts in the system. In addition, after the system has been equilibrated, operational changes to temperature, gas concentration, or flow rate shifts the equilibrium, and steady-state must be reestablished, which can require as much as twelve additional hours per condition change. In the last quarter of testing, it was shown that the inclusion of ammonia had a strong effect on the oxidation of mercury by SCR catalysts, both in the short-term (a transitional period of elemental and oxidized mercury off gassing) and the long-term (less steady-state mercury oxidation). All experiments so far have focused on testing the catalysts in a simulated Powder River Basin (PRB) flue-gas environment, which contains lower sulfur and chlorine than produced by other coals. In the next quarter, parametric testing will be expanded to include flue gases simulating power plants burning Midwestern and Eastern coals, which are higher in sulfur and chlorine. Also, the isolation of such gases as hydrogen chloride (HCl), ammonia (NH{sub 3}), and sulfur trioxide (SO{sub 3}) will be investigated. All of these efforts will be used to examine the kinetics of mercury oxidation across the SCR catalysts with respect to flue gas composition, temperature, and flow rate.