The filter press is a very versatile piece of machinery that has become ubiquitous in a number of industrial settings since its introduction. Used for food production, pharmaceuticals, mining, waste management, blood plasma separation, and many other applications, the machine separates liquids from solids. It works by accepting slurry, which is a general name for the combination of liquids and solids, through a pump. A set of moving plates clamps a set of cloth or paper mesh together and, as the slurry moves through the system, the liquid passes through the mesh. Solids are caught in a set of frames, forming “cakes” that are eventually discarded.
Based on this design scheme, three variations of the filter press have been developed.
1. The Plate and Frame Press
This basic design is sometimes known as a membrane filter plate. The device consists of a number of separated chambers, each containing one hollow frame and two plates and separated from the frame by cloth or paper filters. As the slurry flows through the chamber, the plates press into the frame, which catches the solids. As the resulting cakes become Filterpressen thicker, the overall resistance of the mechanism increases until the machine is eventually stopped. At this point, a worker manually removes cakes from each plate, and the process begins again.
2. The Automatic Press
This type of design functions similarly to the plate and frame model described above. The only difference is that it is fully automated, so it does not require someone to start and stop the machine in order to discharge the cakes. Instead of this manual labor, a set of mechanical devices shifts the plates as the system operates, which shakes out the cakes. This saves a great deal of time and labor, freeing up workers to tackle other tasks while the process is running.
3. The Recessed Plate Filter Press
This is a more recent innovation in the industry that utilizes a different design. It consists of a set of polypropylene square plates, each two to four feet across with a depression on the surface and a small hole in the center. When the machine is turned on, each set of two plates is pushed together, forming a chamber in which the slurry is squeezed through a set of filters. The solid cakes form inside the depression on each plate. This system has the advantage of enforcing a uniformity of cake sizes, as each cake must fit into the depression for the system to work. While this reduces the occurrence of malfunctions, this design requires more time to replace filters, which negates the possibility of using paper. It is therefore more expensive to operate.
The filter press remains a mainstay of a wide array of modern industries and, despite its age, the principle concept remains efficient and relatively unchanged. Although innovations continue to be made, this type of machinery is here to stay.