多变截面选择性催化还原系统喷氨方式数值模拟

Optimization of ammonia injection in a SCR denitration system with multiple variable cross sections:numerical simulation

以某660 MW燃煤机组选择性催化还原(SCR)烟气脱硝系统为研究对象,采用Gambit软件建立了三维数值模型,以模拟分析反应器内流场分布的特点,并对比了分区喷氨和线性喷氨2种方式对首层催化剂入口氨气分布均匀性的影响。结果表明:因反应器存在2个变截面烟道,从而使得喷氨格栅处的烟气流场分布极不均匀,烟气速度相对偏差系数为27.5%;采用线性喷氨方式时,首层催化剂入口氨气分布相对偏差系数高达25.3%;对于分区喷氨方式,采用10区喷氨方式时首层催化剂入口氨气分布相对偏差系数为8.9%,30分区喷氨方式可使氨气分布相对偏差系数降低至5.6%,分区喷氨的效果显著优于线性喷氨。

Taking the SCR de-NOxsystem in a 660 MW coal-fired unit as the research object,a three-dimensional numerical model was established by using the Gambit software.The characteristics of flow field distribution in the reactor were simulated.Moreover,the effects of ammonia injection strategies on uniformity of the NH3 distribution at entrance of the first catalyst layer were investigated.The results show that,due to the existence of two flue ducts with variable cross sections in the reactor,the flow field distribution at the ammonia injection grid（AGI）is extremely uneven,the relative deviation coefficient of flue gas velocity is 27.5%.When the linear ammonia injection strategy is adopted,the relative deviation coefficient of NH3 at entrance of the first catalyst layer is 25.3%.The relative deviation coefficient of NH3 at entrance of the first catalyst layer is 8.9% when the 10-area ammonia injection strategy is employed and that becomes5.6% when the 30-area ammonia injection strategy is adopted.The ammonia injection effect of partition ammonia injection strategy is obviously better than that of the linear ammonia injection strategy.