Abstract
In order to clarify the mechanism by which the addition of a drying accelerator improves the drying rate of organic sludge, changes in the physical properties of sludge with the drying accelerator during drying is investigated. Since the drying rate of sludge increased most significantly during the reduced-rate drying period, changes in capillary attraction, which has the greatest influence on drying during the reduced-rate drying period, and evaluated the contact angle, which is a factor in the capillary attraction are focused on. In the experiment, 0.8 wt% of a drying accelerator was added to organic sludge, and the contact angles of the dried sludge samples were measured from mid-drying to complete drying. The contact angle of the sludge differed greatly depending on the type of drying accelerator. The contact angle of the sludge dried with the drying accelerator that promoted drying became larger, while the contact angle of the sludge dried with the drying inhibitor became smaller. Therefore, it was found that the drying promotion mechanism is likely that the larger contact angle reduces capillary attraction and weakens the ability to hold water inside the sludge, thereby preventing a significant decrease in the rate of water movement inside the sludge.
