In order to remove gas-phase mercury and NOx from flue gas, experimental studies on flue gas mercury oxidation removal and denitration of Guizhou anthracite combustion with NH4Br addition were carried out. The influence of NH4Br addition on the ignition temperature and combustion characteristics was studied using a thermogravimetric analyzer. The effects of the NHaBr addition amount on gas-phase mercury oxidation and removal were investigated in a bench scale of 6 kW fluidized bed combustor （FBC）. Mercury concentrations in flue gas were determined by the Ontario hydro method （OHM） and the mercury mass balance was obtained. Results show that the NH4Br addition has little influence on the ignition temperature of Guizhou anthracite. With the mercury mass balance of 95.47%, the proportion of particulate mercury Hg^p, gaseous mercury Hg^0 and Hg^2＋ are 75.28%, 11.60% and 13. 12%, respectively, as raw coal combustion. The high particulate mercury Hg^p in flue gas is caused by the high unburned carbon content in fly ash. When the NH4Br addition amount increases from 0 to 0. 3%, the concentration of gaseous Hg^0 and Hg^2＋ in flue gas decreases continuously, leading to the Hg^p increase accordingly. The oxidation rate of Hg^0 is positively correlated to the Br addition amount. It demonstrates that coal combustion with NH4Br addition can promote Hg^0 oxidation and removal. NOx concentration in flue gas exhibits a descending trend with the NHaBr addition and the removal rate reaches 17.31% with the addition amount of 0.3%. Adding NH4Br to coal also plays a synergistic role in denitration.
A novel carbon trap sampling system for gas-phase mercury measurement in flue gas is developed, including the high efficient sorbents made of modified biomass cokes and high precision sorbent traps for measuring particle-bound and total vapor-phase mercury in flue gas. A dedusting device is installed to collect fine fly ash for reducing the measurement errors. The thorough comparison test of mercury concentration in flue gas is conducted between the novel sampling system and the Ontario hydro method （OHM） in a 6 kW circulating fluidized bed combustor. Mercury mass balance rates of the OHM range from 95.47% to 104.72%. The mercury breakthrough rates for the second section of the sorbent trap are all below 2%. The relative deviations in the two test cases are in the range of 15. 96% to 17. 56% under different conditions. The verified data suggest that this novel carbon trap sampling system can meet the standards of quality assurance and quality control required by EPA Method 30B and can be applied to the coal-fired flue gas mercury sampling system.
