A filter press is a commonly used piece of solid-liquid separation equipment, and its filtration methods are divided into open-flow and closed-flow filtration. Filter presses are widely used in chemical, mining, environmental protection, ceramics, metallurgy, pharmaceutical, dye, food, and brewing industries.

The filtration methods of a filter press

1. Filtration methods

The filtrate can be discharged through either open flow filtration or closed flow filtration.

A. Open-circuit filtration

Each filter plate has a water nozzle at the bottom outlet, allowing the filtrate to flow directly out.

B. Closed-circuit filtration

Each filter plate has a liquid outlet channel hole at its bottom. The liquid outlet holes of several filter plates are connected to form a liquid outlet channel, which is discharged through a pipe connected to the liquid outlet hole below the thrust plate.

2. Washing methods

When the filter cake needs to be washed, there are two methods: open-flow unidirectional washing and bidirectional washing, and closed-flow unidirectional washing and bidirectional washing.

A. Open-flow unidirectional washing

The cleaning fluid enters sequentially through the cleaning fluid holes in the thrust plate, passes through the filter cloth and then through the filter cake, and flows out from the non-porous filter plate. At this time, the liquid outlet nozzle of the perforated plate is closed, and the liquid outlet nozzle of the non-perforated plate is open.

B. Open-flow bidirectional washing

The cleaning fluid enters from both sides above the thrust plate and washes twice. The outlet and inlet of the cleaning fluid are diagonally opposite, so it is also called bidirectional cross-washing.

C. Closed-flow unidirectional washing

The cleaning fluid enters the perforated plate through the inlet hole of the thrust plate, passes through the filter cloth and then through the filter cake, and flows out from the non-perforated filter plate.

D. Closed-flow bidirectional washing

The cleaning fluid enters through two inlets on either side of the stop plate, performing two separate washes. The cleaning fluid outlet is in a diagonal direction, so it is also called a double-sided cross-flow cleaning system.

3. Filter cloth

Filter cloth is a primary filtration medium. The selection and use of filter cloth play a decisive role in the filtration effect. The appropriate filter cloth material and pore size should be selected based on the pH value and solid particle size of the filtered material to ensure low filtration cost and high filtration efficiency. And it is important to ensure the filter cloth is flat and the pores are unobstructed when using it.

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