(6,7) NOx emission can be controlled by the reaction of these oxides with ammonia through a selective catalytic reduction process, whose efficiency is sufficiently high to meet the regulation limits. NOx emissions are known to contribute to global warming, acid rain, and photochemical smog formation, and they also pose a risk to human health. (3−5) Therefore, the acceptable limits for the emission of these oxides are increasingly tightening all around the world. (2) Countries around the world have already started to focus on issues of emissions reduction, which is an important way to reach the environmental objectives.
(1) Nevertheless, power plants utilizing pulverized coal as the fuel are often regarded as one of the major sources of nitrogen oxide (NOx) pollution. In fact, this important and relatively cheap power source represents more than 38% of the annual energy production in South Korea. In South Korea, thermal coal-fueled power generation is the second most utilized method of generating electricity right after nuclear power. The proposed subair technique improved the coal combustibility and reduced the NOx emissions successfully in the furnace. This reduction was attributed to the decrease in the peak temperature as a result of a wider combustion region. In addition, this method achieved reduction of NOx by 6.3 and 13.2% when the subair accounted for 5 and 10% of the combustion air, respectively.
Particles from other burners were not affected significantly. The simulation results showed that the subair improved the combustibility of coal particles originating from burners A and B in the lower part of the furnace. The over-fire air was not adjusted to retain the effect of an air-staged combustion. The secondary air flow rate was decreased appropriately to ensure that the total quantity of combustion air remained constant. The flow rate of subair was set to 0, 5, and 10% of the total combustion air. The location of injection ports was determined based on the coal particle trajectory and its effect was investigated numerically. In this work, subair injection was proposed to improve the combustibility and NOx emission in a 500 MW tangentially fired coal boiler.
0 kommentar(er)
