碱基吸收剂脱除SO_(3)试验研究

Experimental study on SO_(3) removal by alkaline absorbent

燃煤机组选择性催化还原(SCR)烟气脱硝系统在运行过程中,烟气中的NH3与SO_(3)在特定温度下生成液态硫酸氢铵(ABS),易在0~40%低负荷造成脱硝催化剂ABS失活和加剧空气预热器冷端换热元件ABS灰垢堵塞。碱粉喷射脱除SO_(3)是控制ABS的重要方法,但现有的格栅式多喷嘴装置存在喷射不均、SO_(3)脱除效率低等问题。研发了立式气固流态化混合分配装置,改善了烟道截面的粉体喷射均匀性。中试试验结果显示:SCR脱硝系统上游烟气中的SO_(3)脱除效率达到55.6%,催化剂ABS结露温度降低8.6℃,最低连续喷氨运行温度降低11.9℃,可拓展催化剂安全运行温度下限,并减轻对机组调峰负荷下限的制约;空气预热器上游SO_(3)脱除效率达到84.3%,ABS沉积影响系数降低86.9%,可延缓空气预热器冷端的ABS灰垢堵塞;烟囱SO_(3)排放浓度约为2.5~3.4 mg/m^(3),可消除蓝色烟羽。

During the operation of selective catalytic reduction(SCR)flue gas denitration system of coal-fired units,NH3 and SO_(3) in the flue gas generate liquid ammonium bisulfate(ABS)at a specific temperature,which is viscous and easy to cause catalyst deactivation at 0~40% low load due to micropore plugging and aggravate the fly ash blockage of heat exchange elements at the cold end of air preheater.Alkali powder injection to remove SO_(3) from flue gas is an important method to control ABS.However,the existing grid type multi-nozzle device has problems of uneven injection and low SO_(3) removal efficiency.A vertical gas-solid fluidization mixing and distribution injection device is developed to improve the uniformity of absorbent powder injection in the flue section.The pilot test results show that,the SO_(3) removal efficiency at upstream of the SCR denitration system reaches 55.6%,the condensation temperature of the catalyst ABS decreases by 8.6℃,and the minimum operation temperature decreases by 11.9℃,which can expand the lower limit of the catalyst operation temperature and reduce the restriction on the lower limit of the peak load of the unit.The SO_(3) removal efficiency at upstream of the air preheater reaches 84.3%,and the ABS deposition influence coefficient decreases by 86.9%,which can delay the ABS ash blockage at the cold end of the air preheater.The SO_(3) emission mass concentration from the chimney is 2.5~3.4 mg/m^(3),which can eliminate blue smoke.