SCR烟气脱硝系统冷风加热改造技术研究

Study on Cold Air Heating Transformation Technology of SCR Flue Gas Denitration System

大唐长春第二热电有限责任公司按照国家要求,对1-6号机组原有的SCR烟气脱硝系统进行超低改造,改造完成后烟气中的氮氧化物满足超低排放标准。但由于水解工艺所用稀释氨气的热稀释风为取自锅炉空气预热器的热风,热风中含灰量较多,极易与氨气中的水蒸气混合,导致氨气管道与喷氨格栅分支管道堵塞,造成氨气流量分配不均,降低脱硝效率。采用冷风加热技术安装在原SCR烟气脱硝系统内,在SCR烟气脱硝系统反应器内安装换热管排,增加1台风机,风源取自室内风,通过管道将室内风送至锅炉尾部烟道内,室内风通过换热管道在脱硝系统反应器内与烟气进行换热,将室内风加热成300~320℃热风,热风与氨气混合进入喷氨格栅分支管道,通过喷嘴射入烟道内与烟气中的氮氧化物反应达到脱硝效果。由于该稀释热风取自室内风,风源中含灰量较少,经加热与氨气混合后大大减少堵塞现象,使氨气流量分配十分均匀,有效提高了脱硝效率,降低了尿素耗量,为电厂节约了发电成本。

Datang Changchun Second Thermal Power Co.,Ltd.According to the national requirements,the original SCR flue gas denitration system of No.1 to No.6 units is ultra-low modified,and the nitrogen oxides in the flue gas met the ultra-low emission standard after the transformation is completed.However,due to the fact that the hot dilute air of the dilute ammonia used in the hydrolysis process is taken from the hot air of the boiler air preheater,the hot air has more ash content and is easily mixed with the water vapor in the ammonia gas.The blockage of ammonia gas pipeline and branch pipe of ammonia spray grid results in uneven distribution of ammonia gas flow and reduces denitrification efficiency.Adopting the cold air heating technology to install in the original SCR flue gas denitrification system,installing the heat exchange pipe row in the SCR flue gas denitrification system reactor,adding a fan,the air source is taken from the indoor air。The indoor air is sent to the flue at the end of the boiler through the pipes,and the indoor air is heated into 300~320℃hot air through the heat exchange pipe to exchange heat with the flue gas in the reactor of the denitrification system.The hot air and ammonia gas are mixed into the branch pipe of the ammonia spray grid,and the nozzles are injected into the flue to react with the nitrogen oxide gas in the flue gas to achieve the denitrification effect.Because the diluent hot air is taken from indoor air,the ash content in the air source is less,the blocking phenomenon is greatly reduced after heating and the ammonia gas is mixed.The ammonia gas flow distribution is very uniform.The denitrification efficiency is effectively improved,and the urea consumption is reduced.The utility model saves the cost of generating electricity for the power plant.