5 Must-Have Features in a Filter Plate Manufacturer

A plate and frame filter press is an indispensable piece of equipment used in various industrial filtration applications. But how exactly does this contraption work to separate liquids and solids?

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In this comprehensive guide, we’ll cover everything you need to know about the working principles and operation of a plate and frame filter press.

What Is a Plate and Frame Filter Press?

A plate and frame filter press consists of a series of vertical plates and frames assembled in an alternating pattern. The plates are covered with filter cloths and the frames have internal channels.

When the plates and frames are pressed tightly together by a hydraulic ram, it creates small compartments between each plate-frame pair. These compartments are known as chambers.

As slurry is pumped into the chambers under pressure, it gets dewatered through the filter cloth, forming a filter cake. The liquid that passes through the cloth is called the filtrate or the effluent. It flows through the frames into a collection pipe and exits the filter press.

Key Components:

• Filter Plates: Made of materials like polypropylene or stainless steel to withstand pressure. They contain the filter cake.
• Filter Frames: Channels inside allow the filtrate to flow out.
• Filter Cloths: Made of materials like polypropylene, nylon, cotton etc. Dewaters the slurry.
• Feed Pump: Delivers the slurry into the chambers under pressure.
• Hydraulic System: Applies pressure to plates and frames for filtration.

How Does a Plate and Frame Filter Press Work?

The working principle of a plate and frame filter press relies on the dewatering capability of the filter cloths under pressure. Here are the key steps:

1. Loading

The filter cloths are fixed onto the plates and frames are installed in an alternating pattern onto the filter press skeleton.

Plate and frame filter press design

2. Feeding The Slurry

The slurry or influent, which contains suspended solid particles in a liquid, is pumped at a certain pressure into the chambers by the feed pump.

3. Filtration

As the chambers fill with slurry, pressure starts building up. The liquid component passes through the filter cloths, while the solid particles begin to accumulate on the cloth surface.

4. Cake Formation

Over time, a porous mass of solids called filter cake is formed on both sides of the filter cloth in each chamber. The filter cake itself acts as an additional filter medium.

5. Filtrate Collection

The liquid filtrate flows through the internal channels of the frames into a central collection pipe via corner ports. It exits the filter press through the filtrate outlet.

6. Cake Discharge

Once the chambers are completely filled with solids and the filtration process is finished, the filter press opens. The cake falls off or is scraped out manually.

Plate and frame filter press working

This sequence repeats for the next batch. The dewatered filter cake goes for further processing while the liquid filtrate is also collected for treatment or reuse.

6 Advantages/Benefits Of a Plate and Frame Filter Press

Now that you understand what a plate & frame filter press is and how the basic filtration process works, let’s go through some of its major advantages:

1. High Filtration Efficiency

It can dewater slurries down to 30% moisture content through positive pressure filtration. This also results in extremely clear filtrate.

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2. Fully Enclosed Filtration

Unlike some other filters like belt filters, the entire process happens in an enclosed chamber. This makes plate and frame filter presses excellent for handling hazardous materials.

3. Adaptability

You can use filter cloths with different materials and meshes for varied applications. Just swap them out between cycles.

4. Easy Maintenance

Maintaining a plate and frame filter press is quite straightforward – just periodically clean or replace the filter cloths. The simple design has few moving parts.

5. Space Savings

With the ability to handle high pressures and deliver high cake dryness, a plate and frame filter press provides substantial volume reduction over other separation processes. This cuts down infrastructure costs.

6. Low Operating Costs

Beyond the initial purchase cost, a plate and frame filter press is an extremely affordable filtration system to operate. Consumable costs are low and energy consumption is minimal.

Typical Applications Of Plate and Frame Filter Presses

Now that you know how a plate & frame filter press works, here are some of the most common industrial and municipal applications where they are utilized:

• Wastewater Treatment: Primary sludge dewatering, waste activated sludge filtration.
• Chemical Processing: Catalyst separation, resin recovery.
• Pharmaceuticals: API crystallization, solvent recovery, cell harvesting.
• Food & Beverage: Sugar syrup and juice clarification, extraction of oils.
• Mining: Tailings dewatering, mineral concentrate filtration.
• Metal Processing: Slag removal from molten metal, hydraulic oil purification.
• Pulp & Paper: Cellulose fiber washing, black liquor filtration.

These were just a few examples of the extremely diverse range of uses for the versatile plate and frame filter press across all types of industries.

Key Considerations While Selecting a Plate and Frame Filter Press

To conclude, here are some key parameters to consider when choosing the right plate and frame filter press for your specific needs:

• Filtration Area: Determines the throughput capacity and filtration rate.
• Cloth Material: Needs to handle your slurry composition, temperature and pressure requirements.
• Cake Thickness: Select frame depth based on desired cake dryness.
• Level Of Automation: Manual, semi-automatic or fully automatic?
• Additional Features: Consider chamber plates for pre-coating, drip trays, and other optional accessories.
• After-Sales Support: Ensure timely provision of spare parts, maintenance and other services.

With their simple yet rugged design and excellent performance, it’s no wonder plate and frame filter presses continue to be ubiquitous across industrial filtration processes for over a century. I hope this guide helped you achieve crystal clarity on what this apparatus is and how it manages to separate crystals!

Filter Presses and Belt Presses are different in several ways. With Belt Presses, slurry is dewatered between two moving synthetic cloths or belts. Water initially is released by gravity then by squeezing the slurry/belts between rollers. The filtrate water is collected below the press unit in a pit. The dewatered cake material is scraped off the belts as they separate at the discharge end of the press. A dewatering polymer chemical is required to flocculate the slurry particles prior to the slurry entering the press. The chemical also aids in allowing the water to release from the solid material.

A plate Filter Press is composed of a frame holding a series of recessed plates lined with filter cloths. The plates are held tightly together, creating a seal around their perimeters using hydraulic pressure. A high-pressure slurry dewatering pump forces slurry into the chamber spaces between the plates for dewatering. The slurry solids are captured between the plates, while the clean filtrate water passes through the filter cloth mesh and exits through ports in the filter plates. When the chamber spaces are full of dewatered slurry solids, the slurry feed pump is automatically stopped. The hydraulic pressure holding the plates together is released so the plates can be separated individually, allowing the cake to fall by gravity out of the press. Typically, no chemicals are required to aid dewatering on a plate filter press.

Recessed plates are solid plates made of plastic or metal or a combination of metal and plastic. The plates have recessed surfaces, except for the perimeter edge surface that allows the plates to seal against each other when they are clamped together using a hydraulic ram. With the plates held tightly together, all dewatering takes place as a result of the slurry feed pump press. 

Membrane plates are similar to recessed plates, having recessed surfaces except for their perimeter edges. The membrane plates are constructed so compressed air or water can be injected inside the plate surface, inflating the plate surfaces. These plates are also held tightly together with a hydraulic ram while the slurry is pumped into the press and dewatered. Once the chambers are filled with dewatered slurry, the feed pump is stopped. With plates still clamped together, the membrane plate surfaces are inflated to compress/squeeze the dewatered cake material. If the material can be compressed, additional water is removed from the solids. The plate surfaces are deflated by relieving the air or water pressure, then the plates are unclamped to allow the plates to be separated and the cakes are discharged by gravity.

Filter Presses are often used to create a closed loop process. This eliminates the need for a settling pond or tailings pond, while also recycling process water back for reuse. By eliminating the need for tailings ponds or settling ponds, valuable land reserves can be protected or freed up for mining rather than being covered with tailings.

In many cases, the use of a closed loop process can also reduce regulatory permits while also putting forth an environmentally positive message for investment companies.

Many companies are now waiting years for permits for new settling ponds without assurance that this permit will be approved. Moving to a closed-loop process can eliminate the need for some of these long permitting processes.

Water availability and cost are becoming more of an issue as large population areas continue to grow. These areas also require quarried and mined materials, but lack of water can be restrictive for new plant considerations. Plant feasibility is greatly improved using a closed loop approach to wet processing with a filter press due to the maximum recovery of recyclable water, minimizing the need for new water sourcing.

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