A membrane (diaphragm) filter press uses inflatable rubber or polypropylene membrane elements on the recessed plate faces — after initial slurry fill and gravity-driven cake formation, compressed air or water (5–16 bar) inflates the membrane inward, mechanically squeezing the cake to reduce final moisture content by 5–15 percentage points vs. pressure filtration alone. Processing 10–50,000 L/batch at pressures up to 16 bar with membrane squeeze at 6–16 bar, it achieves the lowest final cake moisture of any filter press — the preferred type for pharmaceutical API isolation and mineral concentrate dewatering where drying cost is a major factor.
Initial filtration proceeds as a standard recessed plate press — slurry fills the chamber under pump pressure, cake forms on both cloth faces. After fill (detected by low flow rate or high inlet pressure), the membrane is inflated against the cake face by compressed air or water to 6–16 bar, squeezing the cake centrally. The increased mechanical pressure consolidates the cake structure, expressing interstitial liquid through the filter cloth. Squeeze duration of 15–60 minutes reduces cake moisture by 5–15% below equivalent non-membrane press performance. Core blow (compressed air through cake) follows to remove residual surface liquid.
Challenges
Membrane Rupture from Tramp Material in Feed Slurry
Hard or sharp particles puncture membrane elastomer — press loses squeeze capability; batch must be aborted.
Uneven Membrane Inflation Creating Non-Uniform Cake Squeeze
Unequal air/water pressure distribution inflates some membranes more than others — moisture variation across press.
Membrane Fatigue After Extended High-Cycle Service
Repeated inflate-deflate cycles fatigue rubber membrane at fold lines — cracking and loss of pressure retention.
Feed Slurry Bypassing Cloth at Chamber Edge Under High Squeeze Pressure
Membrane squeezes cake centrally but pushes slurry to cloth edge — overflow at edge if cloth not sealed tightly.
Longer Cycle Time vs. Standard Recessed Press (Squeeze + Core Blow Steps)
Additional squeeze (15–60 min) and core blow (5–15 min) extend batch cycle — reduces throughput per hour vs. non-membrane.
Solutions
- Magnetic Inlet Screen + Cyclone Pre-Separator for Tramp Protection: Combined magnetic + cyclone pre-treatment removes hard particles before membrane contact — eliminates rupture risk.
- Precision Air Distribution Manifold (±2% Pressure Uniformity Across All Chambers): Air manifold with calibrated orifices per chamber ensures uniform inflation — consistent moisture across press.
- High-Temperature Vulcanised EPDM Membrane (Rated 2 Million Squeeze Cycles): Premium vulcanised EPDM rated 2 million cycles at 16 bar — replaces standard at 500,000 cycles; 4× service life.
- Cloth Clamping Insert at Chamber Perimeter (Prevents Edge Bypass): SS insert clamps cloth at chamber edge — prevents slurry from bypassing cloth edge under squeeze pressure.
- Simultaneous Fill + Squeeze Protocol (Reduces Cycle Time by 20–30%): Membrane squeeze begins when cake is 80% full — reduces total cycle time; applies squeeze before final fill completion.
Applications
- Pharmaceutical: API final cake production — minimum moisture before vacuum tray drying; reduces drying time and energy.
- Mining: Copper, zinc, iron ore concentrate dewatering — 5–15% lower cake moisture vs. standard press reduces transport cost.
- Chemical: Specialty chemical, pigment, catalyst dewatering — minimum drying step after press.
- Environmental: Municipal and industrial sludge — minimum disposal volume; lowest final moisture press available.
- Food: Fruit and vegetable press cake — maximum solids recovery, minimum liquid in cake.
Models & Capacities
Type 2B — Membrane / Diaphragm Filter Press: Models & Capacities | |||||||||||
Model | Scale | Plate Size [mm×mm] | No. of Plates (max) | Filter Area (max) [m²] | Chamber Vol. (max) [L] | Membrane Squeeze Pressure [bar] | Final Cake Moisture [%] | Core Blow Available | Hydraulic Clamping [t] | Overall L [mm] |
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FPM-320 | Lab/Pilot | 320×320 | 12 | 2.4 | 80 | 6–16 | 15–35 | Yes | 60 | 1,600 |
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FPM-470 | Pilot | 470×470 | 20 | 8.8 | 350 | 6–16 | 15–35 | Yes | 120 | 2,500 |
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FPM-630 | Production | 630×630 | 40 | 31.7 | 1,270 | 6–16 | 15–35 | Yes | 200 | 4,000 |
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FPM-800 | Production | 800×800 | 60 | 76.8 | 3,840 | 6–16 | 15–30 | Yes | 380 | 6,000 |
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FPM-1000 | Production | 1,000×1,000 | 80 | 160 | 8,000 | 6–16 | 15–30 | Yes | 600 | 8,500 |
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FPM-1200 | Large Prod | 1,200×1,200 | 100 | 288 | 14,400 | 8–16 | 12–28 | Yes | 900 | 11,500 |
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FPM-1500 | Large Prod | 1,500×1,500 | 120 | 540 | 32,400 | 8–16 | 12–25 | Yes | 1,400 | 16,000 |
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