The working principle of the folding belt rotary drum vacuum filter is the same as that of the Scraper type rotary drum vacuum filter, the only difference is that the filter slag is removed by folding belt unloading, so the filter cloth of the folding belt rotary drum vacuum filter is zigzagged between the rotating drum and the rollers. The filter effect on fine viscous materials is better. However, when the scraper filter filters fine viscous materials, there are some disadvantages such as difficult discharge, poor permeability, easy clogging of filter cloth, high water content of filter cake and low production capacity. Because the folding belt filter changes the discharge method and strengthens the cleaning of the filter cloth, these shortcomings are basically overcome. When the cake passes through the vacuum area, the filter cloth is led out of the cylinder by a set of rollers for unloading and cleaning, and the cleaned filter cloth is returned to the cylinder weight for new work. The folding belt vacuum filter allows the filter cloth to bypass the discharge roller, and makes the filter cake fall automatically by changing the curvature, and can also use the scraper and other mechanisms to help discharge the material. This discharge improves the filtration capacity, and the air is not blown, so that the cake will not increase water due to the return water. The folding filter leads the filter cloth to the outside of the cylinder and has enough time to clean the filter cloth in an effective way. Generally, both sides of the filter cloth are washed with pressure water, and more thorough cleaning can be carried out with devices such as playons and cloth beaters as needed to ensure the permeability of the filter cloth. The folding belt vacuum filter is suitable for the dehydration of fine and viscous materials, and is widely used to filter the floating washing products of non-ferrous metal concentrate and coal and to treat sewage.