喷雾干燥烟气脱硫工艺对细颗粒排放特性影响的试验研究

Influence of Spray-drying Flue Gas Desulfurization Technology on Emission Characteristics of Fine Particles

采用电称低压冲击器和场发射扫描电镜等对喷雾干燥脱硫前后烟气中细颗粒的数量浓度、粒径分布、形态及元素组成进行了测试分析,考察了喷雾干燥烟气脱硫工艺对细颗粒排放特性的影响.在此基础上,采用5种不同的细颗粒脱除工艺,进行了利用蒸汽相变原理促进细颗粒凝结长大并脱除的试验研究.结果表明:在喷雾干燥烟气脱硫过程中,Ca(OH)2浆液与SO2反应生成的部分CaSO4、CaSO3及未反应的CaO细颗粒可随烟气排出脱硫反应塔,脱硫后细颗粒光滑分散,Ca、S元素含量增加且细颗粒数量浓度提高;在脱硫反应塔出口的高湿烟气中添加适量蒸汽并降低烟气温度,由此建立蒸汽相变所需的过饱和水汽环境可促进细颗粒的脱除,脱除效率随蒸汽添加量的增加而提高.

The number concentration, size distribution, morphology and element composition of fine particles in flue gas before and after spsay-drying desulfurization were measured respectively using electrical low pressure impactor （ELPI） and field emission scanning electron microscope/energy dispersive spectrometry （FESEM-EDS）, so as to study the influence of spray-drying desulfurization technology on the emission characteristics of fine particles. Subsequently, experimental tests were carried out for removal of fine particles by heterogeneous condensation based on five different processes. Results show that after desulfurization, fine particles become smooth and scattered, and the content of element Ca and S increases obviously, while the number concentration of fine particles rises slightly. This effect can be attributed to CaSO4, CaSO3 （formed by reaction of Ca（OH）2 with SO2） and unreacted CaO entering into the flue gas as fine particles. By properly adding steam into the flue gas and lowering the gas temperature at outlet of the desulfurization tower so as to establish a supersaturated condition, fine particles can be removed efficiently, during which the removal efficiency increases with the rising amount of added steam.