Abstract
For the design of selective catalytic reactors of NOx by $NH_3$, engineering approach can be performed to determine the reactor shape, mixing device and $NH_3$ injection system. This study shows the optimization of guide vanes to improve the flow pattern near the catalyst layer of SCR in a untility boiler. By varying their spacings and shapes, flow performance of guide vanes was analyzed to achieve an uniform velocity distribution which increases the NOx convesion efficiency, and a flow direction normal to the layer which minimises the erosion by the dust in the flue gas. Including these results, experimental and numerical studies for the SCR design were discussed.