Filter press

An industrial filter press is a device employed in separation processes, particularly for the purpose of segregating solids from liquids. This machinery consists of numerous filter elements aligned in stacks, which enables straightforward operation for the removal of filtered solids. It also allows for efficient cleaning or replacement of the filter media.

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While filter presses don’t operate continuously, they deliver impressive performance, especially when minimal residual liquid in the solid is a key requirement. One of their applications is within marble factories, where they serve to separate water from mud, allowing the water to be reused during the marble cutting operation.

Understanding Filter Press Technology

In the filter press, the slurry that needs to be separated is injected into the chambers of the press. Each chamber is filled optimally, ensuring that active filling occurs until the last chamber reaches capacity before the sludge from the initial chamber starts to solidify or cake. As the chambers fill, the internal pressure of the system increases because of the buildup of thickened sludge. Then, by applying force, pressurized air or, in some cases, water is used to coax the liquid through the filter cloths, promoting efficiency, particularly if recycled water is drawn from earlier processes.

Historical Background

The invention of the filter press dates back to the United Kingdom, initially aimed at extracting seed oil through the use of pressure cells. Despite its innovation, early models grappled with challenges such as high labor demands and a batch processing system. A turning point occurred in mid-20th century Japan, where Kenichiro Kurita and Seiichi Suwa developed the first automatic horizontal filter press. This innovation enhanced cake removal efficiency and moisture absorption. A subsequent goal in filter press technology has been the integration of flexible diaphragms, which aids in reducing the moisture content of the filter cakes, thus optimizing the filtration cycle, compressing the cake, discharging it, and cleaning the filter cloth, which broadens the range of industrial applications for filter presses.

Categories of Filter Presses

Filter presses are primarily categorized into four fundamental types: plate and frame filter presses, recessed plate and frame filter presses, membrane filter presses, and fully automatic filter presses.

Plate and Frame Filter Press

The plate and frame filter press presents the most basic design configuration, which could also be referred to as a "membrane plate filter." It comprises multiple alternating plates and frames assembled with the support of dual rails, with filter membranes placed between each plate-frame pair.

• The plates support the filter membranes under pressure, featuring narrow slots for liquid to flow through the membrane and collect in the plate for subsequent discharge.
• The frames create chambers for the slurry application, where the accumulated filter cake resides.

The stack experiences compression to ensure a liquid-tight seal between the plates and frames, with either an integrated edge seal or the filter material itself functioning as a gasket. The filter cake thickens as slurry is pumped, increasing filter resistance until reaching a pressure threshold that prompts the process to halt.

For removal of the filter cake, the stack of plates and frames separates, permitting the cake to either fall or be scraped from the membranes into a collection tray below. The membranes are subsequently cleaned using a wash liquid before being recompressed for the next operational cycle.

For more information on various types of BRIGHT filter presses and their applications particularly in pharmaceutical filter press systems, please check out our dedicated resources.