Taking the SCR device in boiler gas denitrification system of a unit as the object

numerical simulation was adopted to investigate the influence of orifice diameter and ammonia injection speed on ammonia concentration distribution at cross section of catalyst layer entrance

on the basis of baffle arrangement optimization for SCR device.The ammonia injection grid(AIG) design was optimized to improve the uniformity of gas and ammonia concentration distribution.The results showed that

decrease in AIG orifice diameter and increase in orifice number did great help to the mixing of NH3 and gas;the best orifice diameter should be 30 mm.With an increase in ammonia injection speed deviation between region Ⅰ and Ⅱ

the NH3 concentration deviation first dropped and then rose;the optimal ammonia injection speed at region Ⅰ and Ⅱ should be 17.0 m/s and 11.0 m/s

respectively.