Dynamics of SO2 absorption by sewage sludge during drying
接触式污泥干化过程中SO2吸收率的动态变化

Using the actual operating parameters of a contact-type sludge drying process, a simulation was conducted to study the dynamics of absorption of suffur dioxide (SO_2) 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 SO_2 absorptian rate decreased with increasing temperature and airflow. At 80℃, the SO_2 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 SO_2 gas diffuses from the gas phase to the gas-liquid interlace, so elevating the drying temperature and increasing the airflow accelerate the evaporation of sludge water, thus hampering the process and causing the SO_2 absorption rate to drop. Increase of the SO_2 concentration in the flue gas had no obvious effect on SO_2 absorption rate. After absorption of SO_2 , 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.