Experimentation Research For Simultaneous Reduction Of No_x And So₂ Emissions By Reburning In Dtf

Entering the 21 century, people's requirements towards the quality of environment are getting stricter with the development of China's economy and the level's improvement of people's living. NOX and SO2 are the main pollutants in flue gas from coal firing power plants and the causes of acid rain. With the rapid development of economy in China, the number of coal-firing power plants increases constantly, and the excess emissions of NOX and SO2 have caused serious environmental problems. Research works about how to control NOX and SO2 emissions have been urgent tasks. Traditional desulfurization and denitrification technology have come to maturity, but for the complexity of the system, high costs of investment, operation and maintenance, some of them have the limitation for application in China. Simultaneous desulfurization (De-SOX) and denitrification (De-NOX) technology receives more and more attentions with its much less investment and relatively high efficiency. Reburning is an efficient technique to remove NOX (mainly NO) from flue gas. By fuel and air staged combustion, reburning can reduce NOx generated in the furnace.The simultaneous reduction of NOX and SO2 by pulverized coal reburning was studied in a drop tube furnace (DTF). A bituminous pulverized coal was chosen as the reburning fuel, and calcium oxide was added as desulfurizer. The influences of stoichiometric ratio (SR), reburning temperature, calcium to sulfur ratio (Ca/S), and residence time on efficiency of removing NOX and SO2 were studied by DTF hot experiments. The experiment results showed that, at the condition of the reburning temperature 1200℃, Ca/S=1.5, NOX reduction efficiency decreased with the increase of reburning fuels stoichiometric ratio, but SO2 reduction efficiency increased. When the reburning temperature increased from 1000℃to 1200℃, NOX and SO2 reduction efficiencies initially increased, but then decreased as temperature higher than 1100℃. NOX reduction efficiency decreased when Ca/S changed from 1.0 to 2.5, and SO2 reduction efficiency increased at all times, in spite of the increasing trend became flat when Ca/S was higher than 2.0. Among all tests, high SO2 and NOX reduction ratios were obtained at SR of 0.8～0.9 and Ca/S of 1.5. The mechanisms of desulfurization and denitrification are also discussed and presented to explain the reactions routine in the DTF.