The fine particle material belt dewatering machine is a traditional belt vacuum filter and filter press used in our company's long-term construction of tailings dry discharge projects. It was found that once the material is fine or has a high mud content, under the action of vacuum pumping or external pressure, the fine particles or mud quickly block the filter holes and form a barrier film on the surface of the filter medium, Regardless of the vacuum pumping force or pressure, it does not work (for example, in early 2011, our company carried out tailings dry discharge for the Great Wall Chemical Processing Plant of Hebei Quanli Group. Initially, we used a cyclone to pre grade and concentrate the bottom flow through a dewatering screen and a cyclone overflow flow through a thickener to concentrate the bottom flow and enter a diaphragm filter press for dewatering. After trial production, it was found that the dewatering effect of the material on the dewatering screen was good, with a moisture content of ≤ 10%. However, the fine particles and mud entering the thickener after concentration and entering the diaphragm filter press had extremely poor dewatering effect. After adding flocculants and filtering, the moisture content was still ≥ 25%, making it impossible to transport. The conclusion drawn after the technical personnel of our company and Quanli Group's demonstration is that due to the high mud content of the raw ore, if the coarse particle material is separated now, the material entering the filter press cannot form a natural filter layer in the filter press, causing the fine mud to directly stick to the filter cloth and quickly block it, so it cannot be filtered. Therefore, our company has introduced advanced technology from the United States and successfully developed a fine particle material dewatering equipment through digestion and absorption. It can continuously filter a large amount of materials, and the product is made of high-strength materials, which have significant characteristics such as high processing capacity, high dehydration efficiency, and long service life;

Its working principle is to use a double-layer filter belt to clamp the slurry and subject it to compression and shear on the extrusion roller for solid-liquid separation. The material that has undergone chemical flocculation first enters the gravity concentration and dehydration zone of the dehydrator, and most of the free water is filtered out through the filter belt under the action of gravity. With the operation of the filter belt, the material enters the ultra large diameter virtual roller, and the wedge-shaped dehydration zone composed of two filter belts is preloaded. By slowly applying pressure, the material thickens and hardens, reducing fluidity and preparing for extrusion dehydration. Then the material enters the pressure section, and the pressure under which it is squeezed continuously increases, reaching its maximum at the outlet. Under the dual action of the squeezing force of the filter belt and the shear force generated by the alternating position of the filter belt, most of the capillary water remaining in the material is filtered out, and the material becomes a sheet-like filter cake with a lower water content. The upper and lower filter belts are separated by the discharge roller, and the filter cake is peeled off from the filter belt with a scraper to achieve solid-liquid separation of the material.

Gravity dehydration zone

The material enters the gravity section of the filter press, and most of the free water between solid particles is only discharged under the action of gravity, separating the solid and liquid. The first part of the gravity dehydration section is the material guide plate, which is used for adding materials and evenly distributing them across the width of the entire working surface of the outer belt. It can maintain the same thickness of the materials and determine the thickness of the material layer. Gravity dewatering also uses several rows of mud rakes to enhance the dewatering effect. Fine particles are continuously sorted by the mud rakes to improve the dewatering effect, so more water can be discharged through the filter belt;

With the operation of the filter belt, fine particles enter the wedge-shaped dehydration zone. The wedge-shaped dehydration zone has a dual function of gravity dehydration and press dehydration. The wedge-shaped section constitutes the first pressure section, which is formed by sandwiching the top and bottom belts into a wedge-shaped shape. As a result, the volume decreases, causing the pressure to slowly increase when the material moves in the same direction along the filter press belt. This ensures that the remaining free water in the fine-grained material is completely removed to meet the requirements of gradually thickening and hardening the fine-grained material, thus smoothly transitioning to the pressurized dehydration zone. To ensure that the material enters the low-pressure dehydration section without being crushed, the design of the wedge-shaped section ensures sufficient filtering area, and a specially designed virtual roller effectively ensures that the material enters the pressure zone smoothly without running out, achieving high-speed operation;

Low pressure dehydration zone

The pressure on the material filter cake increases when the dewatering roller is in the low-pressure dewatering section. Due to being placed between two filter belts, the material is dehydrated through the two belts. Therefore, it cannot be directly squeezed before the material reaches the appropriate concentration. Pre pressing dehydration is very necessary, otherwise a large amount of water containing material will be squeezed out from both sides of the filter screen, causing a harsh working environment. Our designed ultra large diameter virtual roller has a diameter of up to Φ 2000mm, cleverly utilizing the long arc of the ultra large diameter virtual roller to enter the special dehydration roller of the L-shaped guide plate. To prevent the rapid filtration speed from damaging the already flocculated large clumps, which may cause the material to be crushed and overflow from the filter belts on both sides, resulting in an increase in the solid content in the filtrate. At the same time, to improve the overall dehydration and treatment capacity of the machine, large-diameter pre pressing rollers should be selected. Two large rollers with diameters of Φ 1000 and Φ 650 are used in the low-pressure dehydration section;

Pressurized dehydration zone

The filter cake formed in the wedge-shaped section and low-pressure dehydration section is placed under the highest possible pressure to achieve the maximum final dry solid content. For this purpose, these two belts and the filter cake sandwiched between them need to pass through several rollers arranged in an S-shape under a preset "S" tension. The diameter of these rollers decreases along the direction of operation of the filter belt. The number of S-shaped rollers arranged also determines the production capacity and mud biscuit degree of the equipment. The filter belt passes through seven S-shaped rollers, and due to the tension of the filter belt, the unit area pressure generated is directly proportional to the belt tension and inversely proportional to the diameter of these rollers. The diameter of these rollers decreases along the direction of the filter press belt, so the pressure at the last roller reaches its maximum value. All guide rollers are coated with glue to prevent corrosion from sludge and sewage, and are equipped with waterproof grooves to prevent sewage from entering the bearing seat along the roller shaft and damaging the bearings. The sturdy structure of the filter press frame, rollers, and bearings allows for a pressure of up to 12 kilograms to be applied to the filter cake during continuous operation;

Filter strip

Two filter belts are used to complete the material dehydration process. The two filter belts of the filter press are driven by driving rollers, and the driving speed is adjusted by a frequency converter. The speed of the filter belt is between 1-6 meters per minute. The tension and guidance of the filter belt are achieved through pneumatic means. To ensure smooth and continuous extrusion of materials in the filter belt, the length of the filter belt can meet the extrusion residence time of the materials during the dehydration process. The filter belt is made of 100% polyester silk, which has high strength, long service life, good breathability, is not easy to block, and high solid recovery rate. The surface of the mesh belt has undergone heat setting and calendering treatment, resulting in a smooth surface. The filter cake is easy to peel off and has good corrosion resistance. Glue the edges and interfaces of the mesh, making it easy to disassemble and replace the filter belt without dismantling any equipment components;

Filter belt backwash device

There are two independent filter belt cleaning devices, one for each filter belt. The spray pipe is made of high-grade steel SS316L and installed with non clogging flat nozzles. The nozzle has a certain angle with the nozzle axis to ensure no pressure loss. The sprayed water is fan-shaped, causing the spraying on the surface of the filter belt to overlap with each other. This nozzle arrangement can clean the entire surface of the filter belt. Each nozzle can be independently replaced and easily removed for maintenance. The filter belt cleaning device has good sealing and is easy to maintain and clean. The cleaning water source for the dehydrator comes from the production water or effluent from the tail water pump room in the factory; The use of advanced cylinders for correction has a sensitive response, minimal wear on the filter cloth and correction rollers, and is stable and reliable. Each filter belt has two belt correction devices, which control the rotational movement of the adjustment rollers through two cylinders. A sensing board that transmits the position of the filter belt edge to the relevant automatic control device. The filter belt correction system, as a continuous automatic filter cloth guidance system, is an integral part of the filter press. It can operate smoothly and continuously, with flexible and reliable actions. When the filter belt deviates 15mm from the center, the correction device automatically works and can work repeatedly 50000 times. The regulating device for filter belt adjustment and cylinder pressure adjustment are both operated pneumatically. The cylinder is supplied with the required amount of compressed air through a plastic hose. The pneumatic components required for operating the filter press are located in the pneumatic control box, which is installed on one side of the filter press frame;

Filter belt tensioning system

Each filter belt is equipped with a set of filter belt tensioning devices. The tension device of the filter belt is adjusted by adjusting the cylinder pressure. The air pressure is transmitted to the tension roller through the cylinder, and then transmitted to the filter belt, increasing the tension of the filter belt and changing the dehydration pressure of the filter belt. The bearing box of the tension control roller moves laterally on the sliding rod installed on the frame. The working pressure of the cylinder is 4-6 bar. The tension of the filter belt can be adjusted flexibly by adjusting the cylinder pressure to achieve the best dehydration effect

Drive device

Each filter press is equipped with one set of driving device, which consists of a reducer, transmission shaft, motor, and gear. The reducer adopts a shaft mounted reducer without coupling or chain transmission, and the speed of the filter belt can be adjusted. The rated input horsepower of the gearbox is equivalent to the horsepower on the motor nameplate, and the driving device can operate continuously for 24 hours. The gearbox is completely enclosed, waterproof, and the wear-resistant bearings have a long service life. The driving device has overload and overheating protection functions, with a protection level of IP55 and an insulation level of F. The purpose of using a unique shaft mounted reducer and gear transmission is to ensure the smoothness and synchronization of the transmission, avoid friction between filter belts due to different linear speeds, and shorten the service life of filter belts;

Filter cake scraper

Each filter belt is equipped with one set of mud cake scraper. The filter cake is removed from the filter screen by a low wear scraper blade. Material: PP. The angle at which it is pressed onto the filter belt can be adjusted. When the filter belt needs to be cleaned, the locking screw can lift it off. If you need to replace the scraper, you can remove the locking screw and the scraper can be pulled out from the side;