Mercury Measurements from Pilot-Scale Furnaces under Air- and Oxy-fired Conditions

摘要

Experiments were performed in University of Utah's 1.5MW and 100kW pulverized coal furnaces and a 300kW circulating fluidized bed to investigate the suitability of carbon traps for mercury measurement under high CO_2 environments produced by oxycombustion. The difference in mercury emission and speciation between air- and oxy-fired conditions was also evaluated. Both a bituminous (all three furnaces) and a PRB (100kW furnace) fuel were used. Mercury measurements were performed on the flue gas using Method 30b, modified to distinguish between gas-phase and particle-bound mercury. The mercury mass balance was acceptable for all conditions with the exception of oxycombustion in the 1.5MW furnace, indicating a mercury sink not present for the air-fired conditions. Native mercury capture was slightly higher for the oxy-fired conditions in the 100kW and 300kW furnaces, probably related to an increase in unburned carbon in ash. There was minimal difference in gas-phase speciation between air- and oxy-fired conditions.