How long does a filter press cycle take?

Filter press is a machine for solid/liquid separation by forcing the feed slurry through a permeable filter cloth. The separation process takes place in chambers formed between every two filter plates. In this case, the solid phase is inside the chambers (forming a so-called "cake"), and the liquid phase (filtrate) penetrates through the filter media and flows out through the discharge ports.

A filter press has two main components: the framework and the filter pack. The framework holds the filter pack together while pressure is being developed inside the filtration chamber. The chamber however can only hold a specific volume of solids. And the major difference in the type of filter press is the style of plates used in the filter pack.

The filter press is mainly used as a batch pressure filter with fixed volumes. In this case, the machine is designed to process a specific quantity of solids per filtration cycle for efficiency work, if not filled to capacity with solids, the filter cake will not reach its maximum potential for cake dryness. The "batch" means that it is necessary to interrupt the cycle to discharge the collected solids (filter cakes) before starting a new cycle.

The Total Cycle time is the Fill Cycle time plus a constant. For presses of 125 cubic feet and under this constant is usually around 45 minutes. This is the time required to close/open the press, perform the Air Blow Down and discharge the filter cake. If the particular application requires operations such as Core Blow or Cake Wash, for example, this constant is longer.

HOW LONG DOES A FILL CYCLE TAKE?

The Fill Cycle is dependent on many parameters. The most important parameter is the nature of material to be dewatered. A sand slurry releases its water readily and dewaters quickly. On the other hand, an Aluminum Hydroxide waste slurry from beverage can manufacture does not readily release its water and dewaters slowly.

The next most important parameter is the concentration of the solids by weight in the slurry. The Fill Cycle for a 5% solids slurry is about twice as long as a 10% solids slurry (with all other parameters being equal). This is because the press has to process half of the water to fill with solids.

Other parameters include the thickness of the filter cake, the maximum feed pressure which the slurry is fed to the press, and the filter cloth selection. These parameters are typically fixed during the proposal process.

With 32mm (1.25”) cake chamber thickness, 100 psi max feed to the press and a 3-5 SCFM filter cloth, a 5% sand slurry would be expected to dewater in 20-30 minutes and a 10% sand slurry in 10-15 minutes.