Investigation On The Drying Characteristic And Drying Process Of Sludge

Sludge is the byproduct of the municipal waste water treatment , The productivity of municipal sewage sludge is very huge and the component of it is very complex. If sludge can't be well disposed, it will give rise to two times pollution. At the same time, sludge is resource which can be utilized, Much attention has been paid on how to deal with it effectively. At present, aiming at the disadvantages of the traditional treatment ways of municipal swage sludge, the thermal drying is considered as one of the practicable and necessary technology in the field of sludge treatment. The thermal efficiency of the indirect thermal drying technology is higher than the direct thermal drying technology.The drying mechanism is important to the thermal drying technology of sewage sludge. Firstly, the characteristic of the sludge in the static thermal drying process has been studied experimentally. The experimental includes: the influences of two factors, such as the diameter of the sludge particles and the temperature in the drying process; the thermal conduct coefficient of sludge in different moisture content can be given:λ= 0.0025X³-0.031 X²+ 0.1543 X+0.07.To investigate the indirect thermal drying process, The hollow blade paddle dryer is used to dry the sludge particle in this experiment. The experiment system is designed, including the process scheme, equipment structure and retention time control. Using the experiment data, the heat transfer coefficient can be given, Based on the analysis for the factors that influence the heat transfer, a correlation for the overall heat transfer coefficient is also established by using the experiment data: h = 81.94 S^{-0 .3362} ( Nρ)^0.3319 C^-0.0043λ^1.0043.The modified particle heat transfer model is applied to analyze the heat transfer in the drying process. The heat transfer coefficient of the hollow blade paddle dryer and the humidity distributing of the sludge particle in dryer are calculated. When the rotate speed of the thermal conducting axes is changed, a reasonable model of total contact time and single contact time aiming at the hollow blade paddle dryer is set up. The calculated value is accord with the value from the experiment.