Drying Technology
Key words: sludge drying industry,water treatment
The domestic sludge drying industry started late. It sprouted during the reform and opening up period in the late 1970s. Due to the inherent policy constraints of heavy water and light sludge, the domestic large-scale sludge filter press manufacturers have only begun to gradually start in the nineties. It can be seen from the establishment that sludge drying has never been developed. In fact, the domestic policy of focusing on water over mud has been gradually changed since 2010. There are a large number of water treatment and environmental protection exhibitions covering the drying of sludge in China every year, and we can see the vigorous development of environmental protection companies.
In the existing sludge deep dewatering technology, low-temperature drying is an effective method that can evaporate all the capillary water, adsorbed water and part of the bound water of the sludge. The so-called low-temperature drying of sludge is the process of evaporating the water in the sludge through an external heat source lower than the burning point of the sludge. However, sludge drying is a process of net energy consumption, and energy consumption usually accounts for more than 80% of the total cost of sludge treatment. If the waste heat of flue gas is used for sludge drying, the energy consumption bottleneck of sludge drying can be completely overcome.The operating cost of sludge treatment is greatly reduced.
Sludge evaporation dehydration drying is divided into high temperature drying and low temperature drying. High temperature drying will cause the volatilization of harmful substances in the sludge, and the stability and safety of high temperature equipment is poor, and it has been gradually eliminated. Low temperature drying is the use of Xunhua hot air (about 70 degrees) to evaporate the sludge water. Because of the low temperature, harmful substances are not decomposed and cannot be volatilized, and the stability and safety of the equipment are greatly improved.
The sewage condensed from the sludge through the low-temperature drying process is directly returned to the original sewage tank to avoid the environmental protection problem of secondary pollution caused by direct discharge. Compared with other mechanical dehydration, the moisture content of dry sludge can be reduced to a lower moisture content, and the volume of sludge is greatly reduced. This can save considerable environmental protection costs for sewage disposal units due to soaring solid waste disposal costs.
