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Filter press: characteristics, parts, how it works, uses

The pressure that this filter uses comes from a piston, and also from the same solids that are compacted within the interiors of its chambers or frames. In doing so, they form what are known as filter cakes, which further press and push the liquid flowing through the external channels or pipes.

Filter press of the company MW Watermark. Source: Jerem2016 / CC BY-SA (https://creativecommons.org/licenses/by-sa/4.0)

In the image above you have one of the many available filter press models. There are manual and automatic ones, but all generally work in batches or load, so they do not process or filter continuous streams of suspensions. These suspensions are usually made of sludge or pulp, from which it is desired to extract the water to recycle it, purify it, or to improve the qualities of the filtered solid.

The filter press finds use in the mining, food, pharmacy, paint, chemical, textile, and other industries.

Filter press features

Industrial filter press

The filter press could be considered as a large filter, in which instead of being helped by vacuum or gravity, it uses an external pressure to compress and “squeeze” the solid. The solid ends up so compacted that it takes the form of a cake, which must be extracted for subsequent filtration.

It has an inlet through which the suspension to be separated enters the filter, and an outlet through which the filtrate runs in the opposite direction. Once the process is finished, and the solid having been sufficiently purified, the filter cakes are removed and the filter cloths or canvases are washed, in order to repeat the process as many times as necessary.

It is a very heavy machine or tool, which is assembled in parts, suspended and fixed thanks to a support.

Filter press parts

A filter press consists of many parts, the names and descriptions of which vary from model to model. However, they all share in common, regardless of their size, the following four elements: frame or skeleton, filter plates, filter cloths or media, and a collector through which the filtrate extracted from the cakes flows or is discharged.

Frame or skeleton

It is the metal frame that makes up the entire volume of the filter press.

Filter plates

Filter plates of an industrial filter press

The filter plates are the compartments or chambers through which the suspensions enter. A filter press has several of these chambers, which follow one after another, in such an ingenious way that filtration does not begin until the last plate has been filled. Then the pressure will reach an appropriate value to start filtering.

The filter cloths, meshes, or media are the true filters, since the liquid will drain through them due to the increasing and enormous pressure inside the plates.

Manifold

The collector or discharge tube is where the liquid or filtered water ends up flowing towards the filter outlet, to be finally collected.

How does the filter press work?

In the following video you can see the operation of a frame and plate filter press:

The piston or cylinder that will depress all the filter chambers is activated manually or automatically. In portable filter presses, this consists rather of nuts, which are completely closed until the plates are aligned or parallel to each other.

Mud or suspension enters the chambers or frames through side holes. While the chamber is being filled, the level and pressure of the suspension increase until the water begins to pass through the filter medium, with increasing force, giving rise to the appearance of a flow of filtrate that rises and is collected by the top of the filter press.

After filtering, the pressure is released by deactivating the cylinder and separating the chambers. Then the filter cakes are removed, which are nothing more than the compacted solids that were suspended in the initial sludge. Air currents are often blown to further dry out the cakes and ensure that all the water has been filtered.

Applications

Laboratories

At the laboratory level, portable press filters are used, which serve to purify the filter medium or the suspended solid, depending on the desired product. Its performance and efficiency are superior compared to other filtering techniques or tools.

Ceramics

The filter press is used in the ceramic industry to improve the qualities of porcelains, gray, marbles, quartz and pigments. Here, as expected, filter cakes are more interesting than filtered cakes.

Sewage treatment

The plants of wastewater treatment filter presses have to purify water flows.

Mining

In mining, the filter press is used to filter coal sludge and other minerals, in such a way that dry solids of appreciable purity are obtained. These steps are essential so that coal and other minerals can undergo different chemical treatments, with which the extraction of metals, such as iron, gold, lead, copper, manganese and zinc is sought.

On the other hand, the filtered water is used to clean the machinery or to be reused in subsequent processes.

Food

The filter press is especially valuable in the food industry. It is used to purify and improve the quality of syrups, syrups, beers, wines, yeasts, sugars, among other products.

Pharmacy

And finally, in the pharmaceutical industry, the filter press is used to filter liquids, the blood serum being the most important of all, as it serves as a raw material for the synthesis of various drugs.

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