Everything You Need To Know To Find The Best Filter Press Belts

How belt filter presses work

A belt filter press (BFP) provides sludge dewatering by pressing the sludge to force the water through a permeable medium. The process produces a cake (the dewatered product) having a dry solids (DS) content of 30% or more in the case of primary sludge. This is to be distinguished from the lower-energy gravity belt thickener process which achieves a maximum DS content of ~10%.

Huaqiang Product Page

A BFP combines drainage and mechanical pressure sequentially to remove water. The equipment normally comprises 2−3 recirculating belts, with two belts combining at some point to compress the sludge and squeeze water from it.

The conditioned sludge feed is first conveyed along a gravity drainage section of one of the porous belts, as with a gravity belt thickener. It is then subject to pressure as it is passed between two recirculating belts, forming a wedge zone at the inlet, which travel over a roller. This squeezing action from the two belts in this pressure zone releases more water.

Many belt filter press technologies contain a second pressure zone comprising a series of rollers through which the two belts pass with the sludge solids retained between them. The rollers in this high pressure zone apply tensioning (i.e. stretching) to the belts, exerting both shearing and compressive forces on the sludge which further release more water.

Some BFP technologies are based on a three-belt system, where the gravity belt is independent of the two pressurising belts. This allows the recirculation rate for the thickening operation to be separately adjusted from the dewatering operation.

In common with the gravity belt thickener, the belts are subject to cleaning with water spray to limit the plugging of the filter belt pores. The waste washwater is combined with the filtrate.

The overall performance of the BFP is dependent on the feed sludge source and characteristics and the dosing conditions. As with all other thickening and dewatering technologies, primary sludges – both raw and anaerobically digested – are more readily filtered than waste activated sludge (WAS).

Let’s examine the wide variety of factors that influence how Filter Press Cloth performs in your operations.

Type of Filtration Equipment

The type of machine determines the overall strength needed for the filter media. Fabric that may work well on one type of machine may not work at all on another. Tensile strength, elongation properties, flexibility, and durability of the cloth are all important considerations in filter cloth selection. Different types of filters hold and pull fabric in different ways. Some fabrics may work well with one type of filtration equipment, but not with another because of how it stretches, bends, and holds up to stress in the application.

Learn more about the role of yarn fiber materials, filament types, yarn types, and weave patterns in Filter Cloth Selection.

Cake Release

Each type of filter press cloth has different cake release characteristics. Selecting the proper filter press cloth will help to ensure proper cake formation. The proper amount of filter cake dryness will not only prevent the need for excess cloth scraping but will also contribute to lower expenses in hauling away the filter cake.

Learn more about how proper Filter Cloth Selection will help to ensure a trouble-free press operation with excellent cake formation. Symptoms to look out for regarding your filter press cakes include sticky cakes, thin filter cakes, sloppy filter cakes, and partially formed filter cakes.

The company is the world’s best Filter Press Belts supplier. We are your one-stop shop for all needs. Our staff are highly-specialized and will help you find the product you need.

Learn more about Filter Cloth Troubleshooting.

Filter Cloth Ease of Cleaning

How clean does the filter need to be? Some processes may require the cloth to be cleaned after each cycle, or during the process. How is the cloth cleaned, and what is used to clean it? A spray bar may be used to clean cloth on a filter but may also create additional abrasion and wear on the filter press cloth.

Learn about whether Chemical Cleaning is an effective tool in cleaning your filter press cloth.

Learn about Micronics Automatic Cloth Washing Systems and how they are well-suited to extending the life of your properly selected filter press cloth.

Particle Size

Particle size is important when selecting filter cloth. Different fabrics are equipped to handle different particle sizes. If the cloth’s pores are too big, particles will pass through without being caught in the filter. If the pores are too small, the cloth will blind and prevent slurry from passing through. Often, the cake that forms on the cloth is performing much of the filtering. The cloth must have the right pore size to build a cake but still allow liquid to flow through.

Particle Size Distribution & Shape

Just as particle size is important when selecting filter cloth, so is particle size distribution. In some applications, the particles are all about the same size. In others, large particles are mixed with fine particles. Understanding the particle size distribution helps find the ideal cloth to use as your filter media.

Sometimes, if particle size varies, the material can be processed multiple times in order to efficiently filter. The first pass will catch the largest particles on the cloth but not finer particles. The second pass will allow medium-sized particles to build a thicker cake on top of the largest particles. Additional passes catch and build up finer particles until optimal filtration efficiency is achieved.

The shape of the particles will affect how the cake builds, how it adheres to the cloth, and how much wear may be put on the filter press cloth.

Chemistry/Operating Temperature

Different types of filter press cloth are equipped to handle different operating conditions. Most fabrics have a maximum operating temperature. Operating outside of that will damage the cloth and affect filtration efficiency. Depending on what the fabric is made of, it may also be susceptible to chemical damage. Filter media selection takes into account susceptibility to chemical attack as well as the operating temperature and consistency of the slurry.

Some types of cloth have an ideal pH range. Many times, both pH and operating temperature need to be considered to ensure the cloth can handle the operating conditions.

The Micronics Engineered Filtration Group can help you select the optimal filter press cloth for your operating conditions which will also help to extend filter press cloth life.

Volume of Material Being Processed

Consider how much material is being processed. How thick does the filter cake need to be? How heavy is the filter cake? If the cloth must support all the weight of the filter cake, the fabric must be strong enough to handle the load of the material being processed.

Want more information on Polyester Filter Mesh? Feel free to contact us.

Need Help Selecting the Right Filter Fabric for Your Specific Application?