The moisture content changes of feedstock is a very important economic parameter for the drying system. The lower the content is, the higher the investment will be. In addition, it is an important parameter for security.

Moisture content may fluctuate due to different sources of wet mud (possibly from several different sewage treatment plants) or improper operation of dehydrator (mechanical failure, mechanical efficiency reduction, replacement of flocculant or changes in additive amount). When the fluctuation range exceeds a certain range, it may pose a threat to the safety of drying.

The cause of the danger lies in the characteristics of the drying system itself. Generally, during the commissioning process, the amount of heat and its relevant process gas has been determined, and the feed amount of the feed device is controlled only by monitoring the temperature and humidity of the gas at the outlet of the dryer.

The determination of the amount of heat means the determination of the amount of evaporation per unit time. When the water content of feedstock changes and the feed quantity is constant, the moisture balance of internal system will be broken. If the humidity increases, it may cause uneven drying; if the moisture content decreases, it means the increase of the dust amount and the particle temperature rises.

The change of moisture content of full drying system is sensitive. Theoretically, when the feedstock is carried out directly, only a maximum of 2 percentage points of fluctuation (such as setting 20%, but actual 22%) is allowed. At this time, due to the rapid decrease of sludge moisture, The temperature of the product in the dryer will rise and form a dangerous environment. Since this section is very narrow, the demand for monitoring feedback system for adjusting the feed quantity of wet mud is higher.