600 MW燃煤机组多变截面SCR脱硝系统流场及喷氨优化

流场均匀性对脱硝效率有重要影响,喷氨格栅(AIG)上游和催化剂入口标准速度偏差是衡量流场均匀性的重要指标。采用FLUENT6.3软件对某600 MW超临界燃煤机组的SCR烟气脱硝系统内流场进行数值模拟,主要针对空塔布置时,在烟道多变截面和弯头处出现的流场充满度差、低速三角区、高速冲刷区和低速回流区进行优化。模拟结果显示,采用不同倾角的"直板"、"圆弧"型、"平直—圆弧—平直"型和"圆弧—平直"型导流板可以有效抑制烟道弯头处烟气速度分离的现象。将AIG上游标准速度偏差从空塔时的58.60%降低到9.43%,催化剂入口速度偏差从空塔时的86.31%降到8.60%。提高了NH_3与烟气的混合效果,氨氮摩尔比维持0.81左右,脱硝效率从69.76%提高到92.37%,NH3逃逸率由1.9×10~(-5)降低到2.9×10~(-6)。

FLOW FIELD AND AMMONIA SPRAYING OPTIMIZATION OF SCR DENOX SYSTEM WITH VARIABLE CROSS SECTION IN 600MW COAL-FIRED UNIT

Flow field uniformity has an important impact on the denitrification efficiency,the velocity standard deviation at ammonia injection grid (AIG) upstream and catalyst inlet is an important indicator of the uniformity of the flow field.The paper applied software FLUENT6.3 to simulate the flow field in SCR reactor of 600 MW supercritical coal-fired units,mainly optimized the low triangle,high-speed and low-speed erosion zone reactor when the reactor was arranged by empty tower.The simulation results showed that arc-type,arc-straight-arc type and arc-straight type deflectors could effectively inhibit the flue gas velocity isolated phenomenon at elbow flue.The speed standard deviation at AIG upstream was dropped from 58.6％ to 9.43％ at the empty tower and catalyst velocity-inlet's speed deviation dropped from 86.31％ to 8.60％.The mixing effect of NH3 and oxygen was improved.NH3/NOx molar ratio was about 0.81,denitration efficiency was increased from 69.76％ to 92.37％,and NH3 escape rate was reduced from 1.9 × 10-5 to 2.9 × 10-6.