Research On Flow And Mixing Characteristic Of Leaf Type Of Static Mixer Elements

At present, Selective catalytic reduction(SCR) is the most effective and most widely applied method in removing NOx from the boiler flue gas. Static mixer is a common mixing device in the SCR system, whose mixing result related with SCR denitration effect directly. In order to solve the problem of rapid mixing, this paper attempts to study a kind of static mixing device that can mixes the flue gas with the reductant well. This paper researched on the leaf type static mixing elements, by adopting the combination of numerical simulation and experimental study methods, studied the internal fluid mechanics performance and mixing performance of the mixer when airflow passed.Three typical leaf shape(willow leaf, maple leaf, pine leaf) of static mixing elements were numerically simulated. The results show that: imitation of pine leaf type mixing element causes smaller velocity disturbance range, willow leaf type causes the largest disturbance range; at the wake of the mixing element blade, the fluid turbulent intensity and turbulent kinetic energy dissipation rate are quite large, and in which that the blade’s downstream of willow leaf type has the largest turbulent kinetic energy and dissipation rate and the strongest mesoscopic and macroscopic mixture, pine leaf type is minimal; The pine leaf type mixing element can hardly influence the pressure drop of the fluid inside the pipeline basically, the willow type and the maple type make the pressure drop of the fluid inside the pipeline have obvious changes, and the maple leaf type makes the trend of increasing pressure drop more evident.With turbulent kinetic energy principle, the willow leaf type mixing element is selected as the best leaf type preliminarily. The flow characteristics and mixed characteristics of willow leaf type element were researched by numerical simulation and experimental method, and the influence of the leaf amount and angle of leaf and the axis to the mixed effect were analyzed. The results show that the numerical simulation results and experiment by using the same mathematical model are consistent. When the angle between the blade of mixing element and axis becomes bigger, the turbulent kinetic energy becomes bigger, the mixing element produces more vortex when it is at L=26cm, the constant distance of high speed standard deviation coefficient along the way becomes longer, both standard deviation coefficient of the speed and the concentration at the outlet become smaller, mixing effect is enhanced. With the number of the leaf blade increased, the turbulent kinetic energy becomes bigger, the concentration deviation coefficient along the way decreases faster and the standard deviation coefficient of the speed at the outlet becomes smaller. With the small vortex at the downstream position of mixing element decreased, the mesoscopic mixture becomes weaker. When the number of hybrid element blades is a certain, pressure increases as the angle between the blades and the axis becomes bigger. When the angle between the blades and the axis is a certain, pressure increases as the number of hybrid element blades increases.