Have you heard of a filter press but are not sure if it makes sense for your application? This article will answer the following questions that you may have: What is it? How does it work? What are some applications it is used for?
M.W. Watermark specializes in the manufacture of equipment used for water and process filtration applications worldwide.
What is a Filter Press?
A filter press is a piece of equipment used to separate liquids and solids using pressure filtration. A slurry (a watery mixture of insoluble matter) is pumped into a press and dewatered with pressure. Filter presses are designed to match the volume and type of slurry that needs to be dewatered.
M.W. Watermark® offers a wide range of filter press types and capacities as well as parts and accesories for a wide variety of applications. To learn more see our filter press product page. Our custom designed filter press sizing calculator will help you determine what filter press is right for your application.
Filter presses are comprised of five key elements: filter cloths (a key component for optimal performance), filter plates, steel frames, hydraulic systems, and manifolds. A filter press is designed to efficiently process large batches of pressurized slurry.
Filtration occurs at the filter cloth, a flexible material securely positioned by its corresponding filter plate
Multiple plates stack within a steel frame, clamped together by the hydraulic system.
This plate stack creates a circuit for the liquid, beginning and ending at the manifold.
How Does It Work?
The working principle of filter presses is that during the fill cycle a slurry is pumped into the machine until the solids are evenly distributed.
At the heart is the filter cloth which separates liquid filtrate from suspended solid particles. Initially some fine particles may pass through (fig. 1). As larger particles bridge the cloth openings, they form an initial layer that enhances filtration efficiency because of the reduction of effective openings in the filter media (fig. 2). During the feed cycle, solids distribute evenly throughout each chamber, and the solids compact tightly because of the increased pressure (fig. 3).
Dewatered filter cake completely fills each chamber by the end of the filtration cycle. Clamping two filter plates together creates each chamber, with filter cloth encasing the entirety of this cavity. The steel frame aligns and holds the plates which form an interconnected system of chambers, and they each contribute to the overall capacity of the fixed-volume filter press.
Once the liquid makes it beyond the cloth barrier, the plates feature an inner porting system that delivers filtrate to the manifold. Once the even-fill process has concluded, the operator changes the valve configuration on the manifold to end the feed cycle and allow filtrate to exit the press through a single point: the filtrate outlet.
Upon completing of the filtration cycle, the follower retracts, and the filter press is ready to be emptied. Clamp the press again to begin a new batch.
In many higher capacity filter presses, fast action automatic plate shifters are employed, speeding cycle time. Some filter presses are specifically designed for fully automatic, 24-hour operation in harsh environments such as mines or chemical manufacturing plants.
Now that we have answered how does it work, let’s look at how it is used.
What are some applications?
Filter presses are used in various applications in a variety of industries. Surface finishing, chemical engineering, battery recycling, bioplastic production, mining, chemical manufacturing, and food and beverage processing use filter presses in their workflow.
The industry, application and operational considerations will guide specifics such as the overall design, filtration capacity, number of chambers, filter plate size, materials of construction, as well as additional features and systems such as plate shifters, cloth washing system, drip trays, cake shields and safety light curtains. Design depends on filtration cycle time, cake dryness required, cloth life, whether manual or automated plate shifting is desired, and many other factors.
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