The first deep sludge drying and drying system in Nanjing was commissioned

The first deep sludge drying and drying system in Nanjing recently started trial operation at Chengdong Sewage Treatment Plant. This new technology can reduce the water content of sludge from the original 80% to 60% or less, which will greatly increase the Reduce sludge treatment costs.

At present, Nanjing produces about 1.1 million tons of sewage every day. There are currently more than 20 sewage treatment plants in Nanjing. Before this new technology was put into use, all sewage treatment plants use the principle of centrifugal force to transfer sludge from the sewage. The water is separated like a washing machine. After this separation, the water content in the sludge is still about 80%. This new technology uses an extrusion method to reduce the moisture content of the sludge to below 60%. After two or three days of stacking and turning, the moisture content of the sludge can be reduced to 50. %the following. The reduction in the moisture content of the sludge directly affects the cost of transportation. In addition, the cost of burning and generating electricity after the sludge enters the power plant will be greatly reduced. It should be said that this new technology is also the future direction of sewage treatment in Nanjing. .

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Sludge dewatering and drying equipment

Usually, the sludge is first pretreated to improve dewatering performance and then dehydrated and dried . The most common pretreatment method is the addition of inorganic salts or polymeric coagulants. In addition, there are panning and heat treatment methods. Mechanical dehydration methods include filtration and centrifugation. Filtration is to filter the wet sludge layer (porous material such as filter cloth, metal mesh) so that moisture (filtrate) permeates the filter layer, and the dewatered sludge (filter cake) is trapped on the filter layer. The centrifugation method uses the different centrifugal tendencies produced by the difference in the solid and liquid specific gravity of the sludge to achieve the separation of the slurry. The equipment used for the filtration method includes a vacuum filter, a frame filter press and a belt filter. The vacuum filter continuously enters the mud, and mud is continuously discharged. The operation is stable, but there are many ancillary facilities. The frame filter press is a commonly used chemical equipment, which has a large driving force for filtration and a low moisture content in the mud cake. The inflow of mud and mud is intermittent and the productivity is low. Manually operated plate and frame filter presses are very labor intensive and are now mostly used for mechanical automation. Belt filter is a new type of filter. It has a variety of designs, and the dewatering principle is also different (gravity filtration, pressure filtration, capillary suction, granulation), but they all have turning belts, while carrying mud, while dehydrating, or Only the role of mud transport. Their complexity and energy consumption are similar. Centrifugal method is commonly used horizontal high-speed settlement centrifugal dewatering machine, which is composed of inner and outer drums. The drum is cylindrical at one end and conical at the other end. The rotation speed is generally around 3,000 rpm or more, and there is a certain speed difference between the inner and outer drums. Centrifugal dehydrator continuous production and automatic control, sanitary conditions are better, the area is also small, but the sludge pretreatment requirements are higher. The mechanical dewatering method is mainly used for primary sedimentation sludge and digested sludge. The moisture content of the dewatered sludge is related to the nature of the sludge and the dewatering method. Under normal circumstances, vacuum filtered mud cakes have a moisture content of 60% to 80%, plate and frame filter filtration of 45% to 80%, and centrifugal dewatering of 80%. To 85%.

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