The hollow paddle dryer is composed of a W-shaped shell with a jacketed end face, an upper cover, a hollow shaft with blades, an end cover at both ends, a rotary joint with hot medium, a metal hose and a transmission mechanism including gears and sprockets.
The core of the equipment is the hollow shaft (can be divided into single, double, four) and the hollow stirring blade welded on the shaft. In sludge drying process, it is generally biaxial. The shape of the blade is a wedge-shaped hollow semicircle, which can be heated by medium. In addition to stirring, it is also the heat transfer body of the equipment. The two main heat transfer sides of the blade are inclined. Therefore, when the material contacts the inclined surface, the rotating particles of the blade quickly slide away from the inclined surface, so that the heat transfer surface is constantly updated. The dryer operates continuously. When two spindles are configured, the rotation direction is opposite. The spindle speed is low and the linear speed is lower than 2 m / s. The main shaft, paddle and W-shaped groove (including the part above the shell which is a certain distance higher than the outer diameter of paddle) are all hollow with hot fluid in the middle. The upper dome of the dryer is not heated, which is used for opening inspection windows, connecting air ducts, pipelines, etc. A suction port is arranged in the middle of the top cover to extract the evaporated water vapor in a micro negative pressure way.
The heat transfer mode is heat conduction, only a small amount of ambient air flows in when the negative pressure is extracted, and the movement direction of gas and material is cross flow. The residence time of the material in the dryer is longer. The process loop is open loop, and the treated waste gas will not be returned. As the main shaft is a rotating part, it is also a heat exchange surface. For the sake of sealing and mechanical deformation, the temperature of the process medium shall not exceed 200
Degree. Because the latent heat is released by steam while the sensible heat is only released by heat transfer oil, the steam working medium is generally selected for this process. At this time, the required heat flow path for conveying hot fluid is small and easy to arrange. The typical saturated steam temperature is 150-200 ℃, and the pressure is 5-7 MPa.
The paddle dryer has a high heat transfer efficiency. The agitated blades not only have the effect of heat transfer, but also can break the sludge and play a dynamic role. It also has the function of self purification which is lack in general drying, which is more suitable for sludge drying with large flow and high viscosity.
(1) The structure of paddle dryer is compact. Wedge blade and wall can conduct heat at the same time. The heat transfer efficiency is as high as 80%.
(2) The paddle dryer has the function of shearing and self-cleaning, which is especially suitable for the sludge material with high viscosity of wet material and no adhesion of dry material.
(3) In order to promote the paddle dryer in sludge treatment industry,