Filter Press Filtration Process: Key Steps Explained

Filtration using a filter press is a highly efficient method for separating solids from liquids, commonly used in industries such as mining, chemical production, and wastewater treatment. This guide explains each step in the filter press filtration process and highlights key phases that maximize efficiency and output.

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1. Filling Phase: Slurry Introduction into the Filter Press

In the first phase, the slurry &#; a mixture of solid particles and liquid &#; is pumped into the chambers of the filter press. The chambers are formed by a series of filter plates lined with filter cloth. As the slurry enters, solid particles begin to accumulate on the filter cloth, forming a filter cake, while the liquid (filtrate) passes through the cloth and is discharged.

2. Compacting Phase: Solid-Liquid Separation

As the chambers fill, the pressure within the filter press increases. This pressure pushes the liquid through the filter cloth, trapping solid particles and forming a thicker filter cake. The filtration efficiency in this phase depends on factors such as the permeability of the cloth, the nature of the slurry, and the applied pressure.

3. Cake Washing: Removing Impurities from the Filter Cake

For certain applications, washing the filter cake is essential to remove impurities or recover trapped liquids. During this phase, a washing liquid is introduced through the filter plates, effectively cleaning the cake and improving the purity of both the solid and liquid outputs.

4. Cake Squeezing: Optimizing Cake Dryness

To reduce the moisture content in the filter cake, some filter presses feature a cake squeezing phase. A membrane inflates inside the plates, applying extra pressure to squeeze out additional liquid, resulting in a drier, more compact cake. This step is crucial for industries that require minimal moisture in the solid output.

5. Cake Blowing: Further Drying the Filter Cake

The cake blowing phase involves blowing compressed air through the filter cake to remove residual liquid, further increasing its dryness. This step is essential for achieving the lowest possible moisture levels in industries focused on efficient solid-liquid separation.

6. Core Wash and Core Blow: Cleaning the Feed Channels

Over time, the feed channels within the filter press can become clogged with residual slurry or cake material. The core wash flushes these channels with a cleaning liquid, while the core blow uses compressed air to clear any remaining debris. These steps are crucial for maintaining optimal filtration performance and preventing blockages.

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7. Cake Discharge: Removing the Filter Cake

Once filtration is complete, the filter press opens, and the filter cake is discharged from the chambers. This step is fully automated in most modern filter presses, ensuring quick and efficient removal of the dried solids.

8. Cloth Cleaning Systems: Maintaining Filter Cloth Efficiency

After cake discharge, some filter presses are equipped with systems to clean the filter cloths:

• Rinse Wash: This system sprays water over the plates, cleaning the surface of the cloths after each cycle.
• High-Pressure Cloth Washing: A more thorough cleaning, typically performed once a day or as needed, uses high-pressure jets to remove deep-set particles, ensuring the filter cloths remain efficient for future filtration cycles.

The filter press filtration process is a highly effective solution for solid-liquid separation across various industries. By understanding each step &#; such as squeezing, cake washing, cake blowing, and cloth cleaning systems &#; businesses can optimize the filtration process, improve efficiency, and achieve higher quality output.

If you are curious to learn more about each step of the filtration process, feel free to reach out, and I&#;ll be happy to provide any additional information.

Dino Ibba &#; Regional Sales Director &#; USA & Canada

+39 366 69 75 963

Cake filtration or cake-forming filtration is a mechanical process for the separation of solid-containing liquids. It pertains to surface filtration like cross-flow filtration. In contrast to depth filters, the actual separation effect does not take place through the filter medium but through a filter cake, which forms on the filter cloth. As one of the oldest filter units, the filter press is the most important and efficient process pressure filter. Especially when it comes to the highest level of filtration efficiency and maximum degree of dewatering of various filter media. Depending on the application, filtration with filter presses has different functions as a mechanical separation process:

• • Purification of raw materials and products as well as separation of by-products

• • Recycling of solvents and unreacted reactants

• • Removal of impurities from waste water

• • Extraction of recyclable materials and raw materials

WORKING PRINCIPLE OF A FILTER PRESS

During discontinuous cake filtration with filter presses, the suspension to be filtered is pumped and concentrated via the turbidity inlet into the filter plate chambers. The driving force for the liquid transport is provided by a feed pump. The filter plates are lined with special filter cloths according to the respective application. These cloths retain the solids in layers during the flow. A layer of the solids to be separated accumulates over time. This layer is known as the filter cake, which remains in the plate chamber as a solid mass and makes a significant contribution to the filtration of the liquid. The filtrate, which penetrates the filter cloths, is discharged along a channel system via the filtrate drain introduced into the filter plates. As the layer to be flowed through grows, the flow through resistance increases and with it the pressure loss, with a concomitant decrease in throughput and flow rate. The permeability of the cake decreases with compressible products. This leads to inefficient and uneconomically long filtration times. With periodic cake filtration, the filtration process is interrupted once a predetermined pressure has been reached. If necessary, the filter cake is squeeze-treated (membrane technology) and then removed by opening the filter press. After optional cleaning of the filter cloth and closing of the unit, filtration starts again from the beginning. The filtration cycle is essentially divided into four phases:

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