氨法烟气脱硫过程中气溶胶颗粒生成特性

利用自行搭建的模拟氨法烟气脱硫实验平台,针对氨法脱硫中脱硫浆液液滴夹带蒸发和非均相反应两种气溶胶生成途径,采用电称低压冲击器(ELPI)、PM_2.5/10采样器、场发射扫描电子显微镜(FESEM)等手段对两种途径下生成的气溶胶浓度、粒度分布以及形貌特征进行了测试分析,实验考察了氨法脱硫工艺参数对两种途径下生成的气溶胶特性的影响。结果表明,氨法脱硫中形成的气溶胶颗粒从数浓度角度而言,主要为亚微米级颗粒,从质量浓度分析,则以微米级及更大颗粒为主;脱硫浆液中挥发逸出的气态NH₃和烟气中水汽、SO₂间的非均相反应是氨法脱硫气溶胶的主要来源,其形成量主要取决于脱硫浆液pH、脱硫塔进口烟温等;其次来自于脱硫液滴的夹带蒸发作用,其形成量主要取决于脱硫浆液浓度、空塔气速等。

Properties of aerosol formation during wet ammonia-based desulfurization process

An ammonia-based wet flue gas desulfurization (WFGD) simulation was built to simulate separately the two different aerosol formation mechanisms in ammonia-based desulfurization process of the inhomogeneous reaction mechanism and the entrainment mechanism. The electrical low pressure impactor (ELPI, Dekati Ltd.) was employed for the online measurement of aerosol concentration in the outlet flue gas after the WFGD scrubber. The pollutant PM sampler was used for aerosol sampling in the flue gas. The samples gathered were then scanned and analyzed by the field emission scanning electron microscope (FESEM). The results showed that the inhomogeneous reaction of NH₃ escaped from desulfurization slurry with the moisture and SO₂ in the flue gas was the dominating one of the two aerosol formation mechanisms in the ammonia-based WFGD, which produced the majority of the aerosols emitted from the scrubber. It was found that the aerosols were consisted mainly of submicron particles if counted in respect of numerical concentration and micron ones in respect of mass concentration. The amount of aerosols produced was depended mainly on the desulfurization solution pH along with the flue gas temperature at the inlet of WFGD, etc. The entrainment mechanism was of the secondary importance in the aerosol formation in the ammonia-based WFGD. The production of the aerosols was mainly related to the desulfurization solution concentration, the empty tower gas velocity, and so forth.