Chinese
The belt filter press, also known as a chain-belt filter, is a type of continuous filter and a new high-efficiency dewatering device. Its operation resembles a belt conveyor, where slurry is dewatered during transport, separating solids and liquids and filtering residues. There are two structural types: pressurized and vacuum. The former is more commonly used and is divided into filter presses and pressing machines; the latter is the vacuum filter.
The belt filter press, also called a belt pressing filter, consists of two endless filter belts wound around a series of sequentially arranged rollers of varying sizes. It removes water from the slurry through the squeezing and shearing action between the belts.
Different arrangements and combinations of the pressing rollers create various models of belt filter presses. They feature a simple structure, high dewatering efficiency, large processing capacity, low energy consumption, low noise, high automation, continuous operation, and easy maintenance. Their cost and operating expenses are over 30% lower than those of plate-and-frame filter presses, making them the preferred equipment for urban wastewater treatment.
Belt filter presses are mainly used in industries such as paper, textile printing and dyeing, pharmaceuticals, mining, steel, coal, and leather, and are especially common in urban sewage treatment and industrial sludge dewatering.
The working principle of the belt filter press generally consists of four stages:
1. Pre-treatment stage: The raw slurry typically has a very low solid content and must be concentrated by gravity settling or other methods to reduce processing costs. A common pre-treatment method is to mix concentrated sludge with polymer flocculants, causing fine particles to agglomerate under the flocculant and settle, preparing the sludge for machine dewatering.
2. Gravity dewatering stage: The flocculated and pre-treated sludge is added to the filter belt. Under gravity, free water outside the flocs passes through the filter belt, reducing the sludge moisture content.
3. Wedge pre-press dewatering stage: After gravity dewatering, the sludge enters the wedge-shaped pressing section. The gaps between the filter belts gradually narrow, applying squeezing and shearing forces to further dewater the sludge. After this stage, the sludge loses almost all fluidity, ensuring it is not expelled during the pressing dewatering section under normal conditions.
4. Pressing dewatering stage: The sludge undergoes repeated squeezing and shearing by a carefully designed series of pressing rollers, removing capillary water and gradually reducing moisture to form a sludge cake. At the point where the belts separate, the sludge cake is scraped off by the discharge blade, and the cleaned filter belt enters the next cycle.
