Filter Press vs Pressure Leaf Filter
At a glance
| Factor | Filter press (plate & frame) | Pressure leaf filter |
|---|---|---|
| Principle | Cloth on clamped plates & frames | Mesh leaves in a closed pressure vessel |
| Enclosure | Open frame | Fully enclosed (inert-able) |
| Operation | Batch; manual open/clean | Batch/semi-continuous; more automated |
| Cake handling | Manual removal between plates | Discharged (vibration/sluice), less manual |
| Labor | Higher | Lower |
| Best duty | Polishing press oil, smaller/variable flows | Bleaching-earth filtration, hot oil, larger flows |
| Capital | Lower | Higher |
| Oxidation exposure | More (open to air) | Less (closed) |
Two ways to hold the filter medium
Both machines separate solids from oil, but they hold the filter medium differently. A plate-and-frame filter press clamps a long stack of plates dressed with filter cloth; oil is pumped in, solids build as a cake between the plates, and clean oil runs out. A pressure leaf filter suspends a set of mesh "leaves" inside a closed pressure vessel; oil is forced through the leaves under pressure and the cake builds on their surfaces. The filter press is essentially an open, modular stack; the leaf filter is a sealed vessel — a structural difference that drives nearly every practical trade-off between them.
Operation, labor and cake handling
The filter press is simple and flexible but labor-intensive: when the cake fills the frames, an operator opens the stack and cleans the plates, which takes time and handling. That is fine for smaller or variable flows and for occasional polishing. The pressure leaf filter is more automated and enclosed: cake is discharged from the leaves by vibration or sluicing with less manual work, and cycles are more repeatable — better for larger, steady duties. So a press trades labor for low cost and flexibility, while a leaf filter trades capital and complexity for throughput and less manual handling.
Enclosure: why it matters for hot and bleaching duty
A decisive factor is exposure to air. The open filter press lets hot oil contact air, risking oxidation, and makes containing fine, dusty bleaching earth harder. The closed pressure leaf filter keeps the oil sealed — it can even be blanketed with inert gas — which suits hot oil, oxidation-prone oils, and filtering spent bleaching earth in a refinery, where dust containment and oxygen exclusion matter. This is why leaf filters are common on the bleaching step, while simple filter presses are often used to polish press oil in smaller mills.
Verdict — which should you choose?
FAQ
What is the difference between a filter press and a leaf filter?
A filter press uses cloth on clamped plates and frames, open to air and cleaned manually. A pressure leaf filter uses mesh leaves inside a closed vessel, is more automated and enclosed, and suits hot oil and bleaching-earth duty.
Which is better for filtering bleaching earth?
Usually the enclosed pressure leaf filter, because it contains the fine, dusty spent earth and excludes air from the hot oil. Filter presses are more common for polishing press oil in smaller mills.
Which needs less labor?
The pressure leaf filter — cake is discharged with less manual handling, and cycles are more automated. A plate-and-frame press must be opened and cleaned by hand between cycles.
Is a filter press cheaper?
Generally yes — it is simpler and lower in capital cost, which suits smaller or variable flows. The leaf filter costs more but offers enclosure, automation and throughput.