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Zhong Y.-L.,National Power Grid Jiangxi Provincial Academy of Electrical Power Science | Li H.-S.,National Power Grid Jiangxi Provincial Academy of Electrical Power Science | Zeng G.-F.,Xinchang Power Generation Co. | Fang Q.-Y.,University of Science and Technology of China
Reneng Dongli Gongcheng/Journal of Engineering for Thermal Energy and Power | Year: 2015

A numerical simulation of the in-furnace flow, combustion and NOx emissions characteristics of a 660 MW swirling opposed-firing boiler was conducted to optimize its low NOx combustion operating condition under the condition of burners in various layers operating in a combination mode. The relative error between the simulation results and the test values was less than 10%, indicating relatively good agreement. It has been found that at the rated load, when burners in all five layers are in operation, if the burners on the front and rear wall in the same layer are shut down respectively, the NOx emissions and the carbon content of flying ash are basically identical. When to shut down the burners in the upper layer is compared with to shut down the burners in the middle layer, the former has a better air staging effectiveness and a longer pulverized coal particle residence time and the NOx emissions and the carbon content of flying ash decrease by 9.5% and 9.8% respectively. In the practical operation of boilers, to shut down the burners in the upper layer will be favorable for reducing the NOx emissions and enhancing the combustion efficiency. ©, 2015, Reneng Dongli Gongcheng/Journal of Engineering for Thermal Energy and Power. All right reserved. Source


Zhong L.-J.,National Power Grid Jiangxi Provincial Academy of Electrical Power Science | Zhang D.-P.,National Power Grid Jiangxi Provincial Academy of Electrical Power Science | Tian D.-F.,University of Science and Technology of China | Fang Q.-Y.,University of Science and Technology of China
Reneng Dongli Gongcheng/Journal of Engineering for Thermal Energy and Power | Year: 2015

A numerical simulation was conducted of the in-furnace flow, combustion, heat transfer and pollutant emissions characteristics of a 700 MW tangential pulverized coal-fired boiler. The simulation results were in good agreement with the measuring values. Both the numerical simulation and practical operation results show that after the A-PM (advanced-pollution minimum) low NOx burners had been adopted and an in-depth air staged combustion modification has been preformed, the in-furnace air dynamic characteristics are good and the air flow will never directly sweep through the water wall and the main combustion zone will be just in its strong reduction atmosphere with a low oxygen and high CO concentration, thus prohibiting the formation of NO and reducing NO that had been produced in a large amount. The NOx emissions from the boiler will drop conspicuously, declining 68.8%, 52.9% and 56.6% at a load of 100%, 75% and 50% respectively. The temperature of the flue gases at the bottom of the tube platen will obviously increase and the main and reheat steam characteristics will improve considerably, thus the temperature will increase to the design value and the heat load of the wall surface of the water wall will be more uniform. Although the carbon content of flying ash and CO emissions concentration will increase, yet the temperature of the exhaust flue gases will decline by about 10℃ and the decrease in the heat loss of the exhaust flue gases will be greater than the sum of the mechanical and chemically incomplete combustion loss thus increased, therefore, the boiler efficiency will increase. ©, 2015, Reneng Dongli Gongcheng/Journal of Engineering for Thermal Energy and Power. All right reserved. Source

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