In order to meet the different requirements of different separation objects, filtering methods and equipment are varied. According to the filtration mechanism, two types of filter cake filtration are available: cake filtration and deep filtration.
In fact, the pore size of the filter medium used in filter cake filtration is not necessarily smaller than the diameter of the particles. At the beginning of filtration, some particles can enter the pores of the medium, and some particles may pass through the medium and make the filtrate turbid. With the extension of the filter, many particles crowded towards the orifice, forming a bridge phenomenon in or on the orifice. When the actual pore size of the solid particle concentration decreases, the fine particles cannot pass through and are retained, forming a filter cake. The filter cake acts as a real filter medium in the subsequent filtration. Due to the small voids of the filter cake, very small particles are also intercepted, making the aluminum liquid clear, and then the filtration can be truly effective. The filter cake is carried out on the surface of the medium, also known as surface filtration.
The depth filter media layer is generally thicker, forming a long and tortuous channel inside the quality layer, the size of the channel is larger than the particle size. When the particles enter the pores of the medium with the fluid, under the action of gravity, diffusion and inertia, the particles tend to the wall of the pore during movement, and under the action of surface force and static electricity, they adhere to the wall and separate from the fluid. The suspension is filtered. medium. The characteristic of deep filtration is that the filtration is carried out inside the filter medium. There is no solid particle layer formed on the surface of the filter medium. Due to the small pores of the filter material, the filtration resistance is large, and it is generally only used for high production capacity, while the particles in the fluid are small and the volume concentration is Below 0.1%, for example, the purification of molten aluminum. In actual filtration, the above two types of filtration mechanisms may occur simultaneously or before and after. In these two filter types, filter cake filtration is widely used.