What is a Filter Press and How Does it Work?

Micronics is the world-wide authority on filter presses and advanced liquid filtration technology. Here, we&#;ll explore the question &#; how does a filter press work? We will also examine the applications where they are most frequently utilized, and some of Micronics&#; standard and custom filter press solutions.

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What is a Filter Press?

A filter press is a piece of equipment used in liquid/solid separation. Specifically, the filter press separates the liquids and solids using pressure filtration, wherein a slurry is pumped into the filter press and is dewatered under pressure. Basically, each filter press is designed based on the volume and type of slurry that needs to be dewatered. Micronics, Inc. is a trusted expert in liquid/solid separation and offers a wide range of filter press types and capacities to suit specific application needs for trouble-free, economical dewatering. These include configurations such as sidebar automatic, manual overhead, automatic dual overhead beam, stainless steel clad, explosion-proof filter presses, vacuum filter presses, and hand filter presses.

The four main components of a filter press include the frame, filter plates, manifold (piping and valves), and filter cloth, a key ingredient for optimizing filter press operations.

How Does a Filter Press Work?

The working principle of filter presses is that slurry is pumped into the machine such that solids are distributed evenly during the fill cycle. Solids build up on the filter cloth, forming the filter cake; the filtrate exits the filter plates through the corner ports into the manifold, yielding clean filtered water.

Filter presses are a pressure filtration method and as such, as the filter press feed pump builds pressure, solids build within the chambers until they are completely chock-full of solids, forming the cake. Once the chambers are full, the cycle is complete and the filter cakes are ready to be released. 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 a harsh environment such as mines or chemical manufacturing plants.

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Filter Press Applications

Filter presses can be built in a wide range of sizes, from small, lab-scale 150 mm presses, to those with much larger capacities, such as those with and mm filter plates. Filter presses are used for liquid/solid separation in an extensive range of industries and applications including:

Customizing A Filter Press for Your Application Needs

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/systems such as automatic plate shifters, cloth washing system, drip trays, cake shields and safety light curtains. Design of a filter press depends on a host of factors such as filtration cycle time, cake dryness required, cloth life, whether manual or automated plate shifting is desired, and many other factors.

Contact the Experts at Micronics

If you&#;re interested in learning more about how a filter press could be customized for your specific application, contact Micronics, Inc. today. Or we may have just the right standard or used filter press in-stock to meet your needs today. Contact Micronics, Inc. today and benefit from our engineered filtration experience.

Frame Components

Stationary Head- The side of the frame without the closure system has a head that aligns with the filter pack. It is also known as the fixed head. It has a feed hole for the slurry to enter and drain hole for filtrate to exit.

Follower Head- The hydraulic ram pushes the follower head, or thrust head against the filter pack. There are no feed or drain holes on this head.

Closure System- A hydraulic ram is used to press the plates together and hold the filter together during operation. It creates a positive seal and prevents leaks.

Sidebars- The filter press plates rest on sidebars to keep alignment and bear weight.

Pump- Necessary to create the pressure which drives the process, it is usually a positive displacement pump or a centrifugal feed pump.

Extra Features- Newer models can include additional components like plate shifters, spray bars, and automatic cake dischargers.

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Types of Plates

Plate and Frame Filters- Plate and Frame was the original design, and is still used in some applications. The plate has a series of channels or pips creating high and low points. A cloth or paper filter media sits on top of the plate and filtrate passes through in the drainage area around the low points. The frame creates the empty space necessary for two plates to have a chamber between them. Cake accumulates within the chamber.

Recessed Filter Plates- Recessed filter plates eliminate the need for frames. The plate&#;s border is thicker than the high points of the drainage area, creating half of the chamber. The plate it touches creates the other half.

CGR: Caulked Gasketed Recessed Filter Plates- CGR plates are a recessed plate that has filter media caulked into place, normally in an octagonal configuration. It seal feed and drain holes with o-rings.

Diaphragm Filter Plates- A recessed filter plate with a diaphragm. When solid cake has bridged its chamber, touching both plates, water is pumped into the diaphragm which swells. This swelling decreases the amount of space available, further dewatering the cake. Diaphragm plates are sometimes staggered with recessed filter plates, so that only one side of any given chamber will swell.

Industrial Filter Media

While cotton was the main filter media, in the s synthetic fibers created better-performing and longer-lasting press cloths. The Micronics Engineered Filtration Group has a wide variety of fibers, and weave types. Please contact us if you would like to ensure that the cloth your filter uses is the best one for your application.

Here is a list of various configurations for filter media.

Drape Over cloth- Twice the length of a plate, a Drape Over Cloth sits on top of the plate and lays down each side. It can be held in place by small nubs, or &#;dog ears&#;.

Drape Over Paper- If the cake has a tendency to blind the filter media after one batch, a filter paper can be draped on top of the cloth. When the Filter Press opens to discharge, the paper is thrown out with the cake.

Duplex Cloth- Two separate cloths, each the size of a plate&#;s single face, are sewn to a gusset that covers the feed hole that runs through a plate. The top and side edges of the cloth either have grommets or Velcro to secure both sides of the cloth to the plate.

CGR Cloth- This Duplex Cloth is shaped to fit in the grooves of a CGR Plate. There is a rope sewn into the cloth&#;s border that gets caulked into each side of the plate.

Filter Press Wear Parts

Micronics can supply the following wear parts for any make or model:

• Plate and Frame Cloths (Drape Over cloths)
• Recessed Press Cloths
• Plate and Frame Papers (drape over papers)
• Custom-manufactured Filter Press cloth
• Rope
• Caulking & Air Hammer kits
• Frames
• Plates
• Caulking cord
• CGR Filter Cloths

Troubleshooting

• Duplex cloths are seeing premature failure. Either the rubber neck for the feed hole tears the seam or the cloth gusset inhibits flow. Our HPR Necks solve both issues!
• Caulking in CGR cloths with a mallet and dog bone is time-consuming and tiring. Micronics&#; caulking air hammer makes installation a breeze. Contact us to learn more.

Partially Formed Cakes Could Indicate Plugged Drainholes

As filtrate passes through the filter cloth it collects on the plate panel and drains into outlet holes on the corner(s) of the panel. The outlet holes have a channel that goes into the adjacent corner eye. The channel runs between the packing surfaces. Another function of the system is to allow the cake to be dried &#;blown down&#; by compressed air. The manifold piping at the end of the press can be valved to let air into the even-numbered plates pushing the liquid thru the cloth/cake/cloth out the odd-numbered plates. Sometimes particles of precoat and bodyfeed pass through the filter cloth and become trapped within the drainage channels plugging or partially blocking them. It can be easy to overlook, since you can&#;t see into the channels unaided.

Inconsistency Will Direct Your Troubleshooting

The plug likely occurs after a filter cloth tear or if the filter media is too permeable for the precoat and body feed used. The best time to check is when you notice a chamber has not formed a dry, firm cake as it usually does. If some chambers in the filter pack form great cakes and others form wet partial cakes, this could indicate which plates are plugged.

Count on the Micronics Engineered Filtration Group to Fix Your Recessed Plate Filter Press!

Why is this bypass occurring? Contact us and we&#;ll dig into the specifics of your process to ensure that both your body feed selection and the filter media are the best choice.