What is Pressure Filtration and Liquid/Solid Separation?

Wednesday, November 7, 2018
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Filter PressPressure Filtration is the process of separating a suspended solid such as a precipitate from the liquid in which it is already suspended by straining it – under pressure – through a porous medium that can be penetrated easily by liquid. Pressure Filtration is used extensively in a range of industries including:

  • Chemical manufacturing
  • Pigments
  • Mining
  • Mineral processing
  • Frac sand
  • Aggregates
  • Sugar beet processing
  • Winemaking
  • Beer making
  • Metal/surface finishing

The liquid to be filtered is called the suspension or slurry. The liquid passed by the filter is called the filtrate. The solid material remaining in the filter is known as the filter cake. The filtrate – free of solids – is forced out of the filtrate manifold.

Choosing a Filter Media for Pressure Filtration

Micronics’ pressure filtration experts recommend the use of woven filter cloth or non-woven, felted material such as needle punched felt, depending upon the application and operating conditions.

The choice of media is critical to the performance of the filtration equipment. This is why Micronics always counsels clients that filter cloth is the key foundation to excellent filter press operations! Improvements in particle retention (capture efficiency) may be achieved by utilizing filter cloth that has been expressly designed with consideration for both the yarn type (e.g. monofilament, multifilament, textured, spun) and the physical construction of the cloth (e.g. weave, weight, etc.)


Solids are the physical state of matter in which samples maintain their shape and size. Some highly viscous liquids, such as cold molasses, flow so slowly that they seem to retain their size and shape and thus appear to be solids. Solids exhibit a regular arrangement of atomic, ionic, or molecular particles. Solid objects have a crystalline structure. In contrast, the molecules of liquids are arranged irregularly. Liquids have no crystalline structure.


Substances in the liquid state of matter are intermediate between the gaseous and solid states. The molecules of liquids are not as tightly packed as those of solids or as loosely arranged as those of gases. The densities of liquids are usually lower than but close to the densities of the same substances in the solid state. In some substances such as water, the liquid state is denser.

Liquids are characterized by a resistance to flow, called viscosity. The viscosity of a liquid decreases with temperature and increases with pressure. Viscosity is also related to the complexity of the molecules constituting the fluid. For example, the viscosity is low in liquefied inert gases and high in heavy oils. A liquid can sometimes be heated above its usual boiling point. Liquids in that state are referred to as superheated. Similarly, liquids can also be cooled below their freezing point.

Contact Micronics for solutions to your liquid-solid separation challenges. We can outfit you with industry-leading filter cloth, filter plates, filter presses, press parts & accessories, and field service. We are your pressure filtration experts…since 1983.

Pressure Filtration CTA