Detection Characteristics And Exhaust Components Of Municipal Sludge Low-temperature Thermal Drying

In China so many urban sludge treatment plants have been built and began to put into operation, the sewage sludge which is produced by sewage disposal process increased rapidly. Sewage sludge is dangerous to environment and hard to be disposal, but it also has potential of reuse. After mechanicaldehydration in sewage treatment plant the moisture content of sewage sludge is still above80%, high water content has been a big problem for sewage sludge treatment and disposal, so deep dehydration of sewage sludge must be done.Thermo-heating is one of the mature methods to reduce the water content in sewage sludge, has been widely used in Europe, Japan and America, but the promotion of thermo drying is very restricted by its high cost because of abundant consumption of energy and its expensive equipments, potential safety hazard is also big program. We study the characteristics of sludge drying in order to emerge the advanced point of thermo-heating.Sewage sludge from one waste water treatment plant in Beijing was studied which was not only by laboratorial experiments but also finally by model simulation finally. Several experiment conditions such as different specific surface but the same quality of the sewage sludge sample (cake, cylindrical and spherical and all were big particles), blowing air or not and four temperature (at125℃,150℃,175℃and200℃) were compared in drying test. Then revised Page model is used to simulate the drying experiments. It is found that cake sludge has the highest drying efficiency, the best efficiency temperature point may be between125℃～150℃. Revised Page model is very suitable to describe the drying characteristics of bigger granular sludge, and through the parameters analysis the turning point of drying efficiency is around140℃, and the drying efficiency could get the higher point when there is blowing air.The last part of this article is about the off-gas from sludge drying process. Off-gas discharged from sludge drying can cause air pollution and obstruct the drying process normal operation, but it is hard to research and always be neglected. We try to find the release characteristic of the off-gas. Puffing and trapping technique only can analysis organic gas with low-boiling. Most organic gases adsorb on TENEX adsorption tube, but hard to be separate and determine on the nature. But there was always that, whether sludge in any condition, it would release harmful organic gas, during dying the gas will increase a lot. The gas with high-boiling temperature could congeal in drying equipments, these problem must be take more care of.