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MEMBRANE TECHNOLOGY / SQUEEZING FOR FILTER PRESSES

Membrane filter presses have a great influence on the dryness of the solid by using membrane technology in the filter plates. A flexible, impermeable membrane attached to the carrier body compresses the cake in the chamber after the feeding process is complete.

 

The membrane technology not only offers the advantage of an extremely high degree of dewatering. Furthermore, the filtration cycle time is additionally reduced, on average by more than 50 percent, depending on the suspension through the membrane filtration. This results in faster cycle and turnaround times, which lead to an increase in productivity. Even with partially filled filter chambers, excellent dry matter results can be achieved thanks to membrane technologies. Even with abrasive media, for example, pump wear is decreased by reduced feeding pressure (6-8 bar depending on the suspension) without affecting the final result.

 

Depending on the degree of dewatering, different dry matter contents (dry matter content – percentage by weight of dry material in the filter cake) can be achieved in the filter cake by squeezing with membrane plates. The range of achievable dry matter contents extends from 30 to over 80 percent. In the standard version, squeezing is also carried out on both sides. Depending on the medium to be filtered, there is also the option of only using membrane technology for every second filter plate. The combination of membrane filter plates and chamber filter plates (mixed package) reduces the initial costs and also guarantees excellent filtration results. This type of filter press is called the chamber membrane filter press.

process optimization of a filter press by membrane technology

SQUEEZING PRESS UNIT WITH MEMBRANE TECHNOLOGY

 

For the operation of a membrane filter press, an additional squeezing unit is always required. The squeezing medium enters the membrane filter plates, causing the individual membranes to expand. This further compresses the filter cake by pressing out the excess liquid. The result is a higher DM content. The degree of compaction depends on the respective suspension. After dewatering, the squeezing unit ensures complete dewatering of the membrane. In the following, you will find an overview of the possible squeezing units and their functional principle.

working principle of a membrane filter press with squeezing unit

PRINCIPLE OF OPERATION OF THE SQUEEZING UNIT USING COMPRESSED AIR

 

The ambient air is used as the squeezing medium for the pneumatic pressurisation. The pressure is reached using a compressor. This serves as a squeezing medium for the membrane lines. Extensive safety precautions are required for this.

 

PRINCIPLE OF OPERATION OF THE SQUEEZING UNIT USING WATER

 

Squeezing using water is carried out from a storage tank. Water is pumped into the membrane plates of the membrane filter press via a centrifugal pump and a distribution pipe. The pressure is controlled via a control valve which allows water to flow off into the storage tank. If necessary, e.g. at different temperatures, automatic adjustment of pressure and pressure rise is possible. The aim of the control system is to achieve the shortest possible squeezing times while complying with the limit values. After dewatering the filter cake, the water is sucked back into the storage tank without loss.