Abstract: The distribution of flue gas flow field and the effects on mixing the reducing agent （NH3） with NOx in SCR system are important in the denitrification. Therefore，the structure optimization by numerical simulation of newly designed SCR reactors is essential in the SCR reactor design. In this research FLUENT software was used to simulate flue gas flow field，the effects on mixing NH3 with NOx at the entrance of the first layer catalyst，and the pressure drop of the system in a 300MW coal-fired power plant. Results showed that the relative standard deviation of flue gas velocity was less than 15% between the above and below section of AIG (ammonia injection grid)，the entrance of the first layer catalyst and the outlet of SCR reactor after structure optimization in the BMCR (boiler maximum continuous rating) conditions；the relative standard deviation of NH3/NOx ratio was less than 10% at the entrance of the first layer catalyst；the maximum deviation angle of the flue gas entrance at the entrance of the first layer catalyst was between ?10° and 10°；the pressure drop of the system was less than 800Pa. Using well-designed deflectors could inhibit the flow separation phenomenon caused by bending and variable cross section，eliminate the high swirl，and make it more smoothly for the flue gas entering the catalyst.

Key words: SCR, flue gas denitrification, numerical simulation, deflector

摘要： SCR烟气脱硝装置中烟气流场的分布及还原剂（NH3）与NOx的混合效果对脱硝效果起着重要作用，因此，采用数值模拟技术对于初步设计的SCR烟气脱硝装置进行结构优化是目前国内外SCR烟气脱硝装置设计必不可少的一部分。本研究采用Fluent软件对某燃煤电厂300MW机组SCR烟气脱硝装置内的烟气流动、第一层催化剂入口NH3与NOx的混合和系统压降等方面进行模拟，结果表明：BMCR工况下，结构优化后的SCR烟气脱硝装置AIG上（下）游、第一层催化剂入口和装置出口截面烟气流速相对标准偏差不超过15%；第一层催化剂入口截面NH3/NOx摩尔比相对标准偏差不超过10%；第一层催化剂入口截面烟气进入最大偏差角度处于±10°范围之间；系统压降低于800Pa。合理的设计导流板能够起到抑制弯管以及变截面所引起的流场分离现象、消除大旋流的产生使烟气更加流畅地进入催化剂等作用。

关键词: 选择催化还原, 烟气脱硝, 数值模拟, 导流板