Filter Press Uses and Selection

What a Filter Press Does

A filter press forces a liquid-solid slurry through a filter medium under pressure. The solids form a cake on the filter cloth; the clarified filtrate passes through and exits via drainage channels in the plates. Batch filter presses discharge the cake manually or semi-automatically when the chambers are full. The process is straightforward — which explains why filter presses have been standard chemical plant equipment for over a century.

Filter press uses cover a remarkable range of industries precisely because the mechanism is so general: any feed with filterable solids and a recoverable liquid or dry cake product is a candidate.

Filter Press Uses by Industry

Chemical manufacturing — pigment dewatering, catalyst recovery, fine chemical cake washing. The ability to perform in-situ cake washing (displacing the mother liquor with wash solvent) is a major advantage over centrifuges in API chemical synthesis.

Pharmaceutical — API intermediate isolation, cake washing for purity control, and solvent recovery. GMP-grade filter presses use polypropylene or stainless steel plates with FDA-compliant cloths. Used pharmaceutical equipment buyers frequently specify filter presses for API work.

Mining and minerals — tailings dewatering, concentrate thickening. High-pressure membrane filter presses can achieve very low cake moisture, reducing transport weight and environmental liability.

Food processing — edible oil clarification, juice polishing, wine and beer filtration. Food-grade filter presses use food-contact-rated materials throughout.

Wastewater treatment — municipal sludge dewatering before landfill or incineration. A dewatering press for sale often refers to belt filter press or membrane filter press units sized for continuous high-volume sludge feeds.

Types of Filter Press

Plate-and-frame filter press — the classic design. Separate plates and frames are alternated; the frame provides the cake space. A used plate and frame filter press is widely available on the second hand market, typically in cast iron, polypropylene, or stainless steel. Well suited to low-to-medium pressure batch filtration.

Recessed plate (chamber) filter press — each plate is recessed to form its own cake chamber, eliminating the need for separate frames. More compact, faster to open and close. The dominant design for chemical and pharmaceutical use today.

Membrane filter press — recessed plates incorporate a flexible membrane. After filtration, the membrane inflates with air or water to squeeze additional filtrate from the cake. Achieves lowest cake moisture of any batch filter press type.

Belt filter press — continuous operation, two-belt design. A used belt filter press for sale is most commonly found in wastewater, paper, and food processing applications where batch operation is impractical. A used belt press requires inspection of the belt condition, rollers, and tensioning system before purchase.

The Filter Press Hydraulic System

Plate closure and the holding force during filtration are provided by the filter press hydraulic system. The hydraulic pump, cylinder, and closing carrier must maintain constant pressure throughout the filtration cycle — often 6–16 bar depending on the press design. On any used filter press, inspect the hydraulic unit for cylinder seal condition, pump output pressure, and any evidence of inter-plate leakage (which indicates insufficient closing force or worn plate sealing faces).

Key Selection Criteria for a Used Filter Press

• Filter area (m²) — determines throughput; calculated from filtration rate per unit area × batch time available
• Operating pressure — standard: up to 7 bar; high-pressure: 15–30 bar for membrane types
• Plate material — polypropylene (most common, chemical-resistant), cast iron (high-pressure mining), stainless steel (food/pharma)
• Cake discharge — manual, semi-automatic (shifting plates), or fully automatic (overhead beam types)
• Cloth condition — filter cloths are a consumable; confirm availability and cost before committing to a unit

SIGMA Process Equipment carries used filter presses for sale — plate-and-frame, recessed plate, and belt press types. All units inspected. Send an RFQ with your feed characteristics and required filter area.