接触式污泥干化过程中SO_2吸收率的动态变化

Dynamics of SO_2 absorption by sewage sludge during drying

根据接触式污泥干化工艺的实际运行参数,通过模拟试验,研究了污泥在干化过程中对烟气中二氧化硫(SO2)吸收率的动态变化及其影响因素,并对导致吸收率变化的原因进行了理论分析.结果表明,污泥对SO2的吸收率随干化温度的升高和气体流速的增大而减小,含水率为55%和75%的污泥对SO2的吸收率分别从干化温度80℃的16.0%和25.0%降至干化温度160℃的6.0%和7.0%,这是因为干化温度升高和气体流速增大,促使污泥水分加速蒸发,从而影响SO2从气相通过气膜向气液界面传递和扩散的过程,最终导致污泥对SO2吸收率的下降;污泥对SO2的吸收率随SO2浓度的增加没有明显的变化;污泥吸收SO2后,pH值降低表明了污泥吸收SO2发生了酸碱中和反应,污泥红外光谱证明污泥对烟气中SO2的吸收是一个化学吸收过程.

Using the actual operating parameters of a contact-type sludge drying process,a simulation was conducted to study the dynamics of absorption of sulfur dioxide （SO2） from flue gas by sewage sludge during drying.The factors and causes leading to changes in the absorption rate were analyzed.The results show that the SO2 absorption rate decreased with increasing temperature and airflow.At 80℃,the SO2 absorption rates of sludge with moisture contents of 55% and 75%,were 16.0% and 25.0% respectively.These rates were reduced to 6.0% and 7.0%,respectively,at 160℃.Absorption of SO2 by sludge occurs when SO2 gas diffuses from the gas phase to the gas-liquid interface,so elevating the drying temperature and increasing the airflow accelerate the evaporation of sludge water,thus hampering the process and causing the SO2 absorption rate to drop.Increase of the SO2 concentration in the flue gas had no obvious effect on SO2 absorption rate.After absorption of SO2,the pH of the sludge dropped,indicating that acidic reactions had occurred.Infrared analysis of the sludge shows that absorption of SO2 by sludge is a chemical absorption process.