The filtration mechanism of the decanter centrifuge is generally divided into surface filtration and deep filtration. If the decanter centrifuge is based on the driving force of the filtration process, the filtration can be divided into four types: gravity filtration, pressure filtration, vacuum filtration, and centrifugal filtration. The names of products in different filtering formats are also different. The following focuses on the filtering of these four types of filtering:
1. Gravity filtration, the driving force of the operation is the static pressure of the liquid column of the suspension itself, generally not exceeding 50 kPa. This method is only suitable for treating the filter slurry with large particle size and low content;
Second, pressure filtration, pumping or other means to pressurize the slurry, can produce higher operating pressure, generally up to 500kPa, can effectively handle the difficult to separate filter;
3. Vacuum filtration, vacuuming on the bottom side of the filter medium, the pressure difference generated usually does not exceed 85 kPa, suitable for filter slurry containing ore particles or crystal particles, and convenient for washing the filter cake;
4. Centrifugal filtration, the operating pressure is the centrifugal force generated by the filter layer, which is convenient for washing the filter cake. The obtained filter cake has less liquid content and is suitable for filtration of crystal materials and fiber materials.
Filtration mechanism of decanter centrifuge:
The mechanism of intercepting solid particles according to the filter medium can be divided into surface filtration and deep filtration. The former is widely used in chemical production; the latter is less used.
1. Surface filtration: The surface of the filter cake generated by the surface of the filter medium or the filtration process is used to intercept the solid particles to separate the solid from the liquid. This filtration removes only particles having a particle size larger than the diameter of the filter cake, but does not require that the pore diameter of the filter medium be less than the diameter of the retained particles. Under normal circumstances, a small amount of particles smaller than the diameter of the medium passage will be mixed into the filtrate through the medium at the beginning of the filtration, but the particles will soon bridge at the entrance of the medium passage, so that the small particles are blocked and deposited on the surface of the medium to form a filter cake. . At this point, the true interception of the particles is the filter cake, while the filter media only acts to support the filter cake. However, when the particle content of the suspension is extremely small to form a filter cake, the solid particles can only be separated from the liquid by the interception of the filter medium; at this time, only particles larger than the diameter of the medium channel can be removed from the liquid;
2. Deep filtration: When the particle size is smaller than the diameter of the medium, the filter cake cannot be formed on the surface of the filter medium. These particles enter the interior of the medium and approach the pore wall by inertia and diffusion, and deposit under the action of static electricity and surface force. Down, thus separating from the fluid. Deep filtration will gradually narrow the channels inside the filter media, so the filter media must be replaced or regenerated periodically.
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