Membrane or chamber filter press: which one for your tailings?

A chamber filter press and a membrane filter press look alike: a frame, a stack of plates, cloths, a feed pump, a cake that drops when the pack opens. The difference comes down to one component — a flexible membrane on one face of the plate — and it changes the result, the cycle and the invoice. Choosing without understanding that difference means overpaying for an advantage you will never use, or saving on a machine that will never reach the moisture you were asked for.

What a chamber plate does

The chamber plate (or recessed plate) is the simplest design. Two plates face to face form a chamber; slurry is pumped under pressure into that chamber; filtrate passes through the cloths and drains away; solids build up against the cloths and form the cake. Filtration stops when the chamber is full or when the filtrate flow becomes negligible.

Its strength is simplicity: no squeeze circuit, one wear part fewer, a lower cost per plate, and maintenance any site crew can handle.

Its limit is physical: late in the cycle, filtration slows down because the cake already formed resists the filtrate. The last minutes cost a lot of time and return little dryness. The cake ends up at whatever moisture the feed pressure and the solids' permeability allow — no more, no less.

What a membrane plate adds

The membrane plate carries, on one or both faces, a flexible membrane that is inflated with compressed air or water once the filling phase is over. The membrane mechanically squeezes the cake against the cloth and expresses part of the remaining water.

Three consequences:

• A drier cake, all else being equal, because the squeeze pressure acts uniformly over the whole surface, where feed pressure no longer works effectively at the end of the cycle.
• A shorter cycle, because filtration can be stopped before its slow phase and the squeeze finishes the job.
• A more uniform cake, which improves cake washing where it is required and makes discharge more consistent.

The price of those advantages: a more expensive plate, a membrane that is a wear part in its own right, a squeeze circuit (compressor or water pump, valves, sequence) to integrate and maintain, and a richer cycle sequence to tune at commissioning.

Comparison — what decides

The questions that decide

What moisture, and why? This is the first question, and it either has a precise answer or it does not. If the cake has to be dry-stacked and stand up mechanically, if the concentrate is sold with a moisture penalty, if the tailings are trucked and every point of moisture is water paid for by the tonne-kilometre — the membrane is often justified. If the cake goes to a pond or to a process that tolerates moisture, the chamber press is usually enough.

How many cycles per day? The number of cycles sets the filtration area required. A shorter membrane cycle can mean a smaller press — or fewer presses — for the same tonnage. On a project where floor space or the building is constrained, that argument weighs as much as moisture.

Is your slurry stable? Particle size, percent solids, mineralogy: the more they vary from one day to the next, the more the membrane delivers, because the squeeze recovers what filtration alone did not achieve. A very consistent feed gets less out of the membrane.

Who will maintain it? A membrane press on a remote site needs a stock of membranes, a crew trained to replace them, and monitoring of the squeeze circuit. It is doable — but it is planned, with the critical spares list, at purchase, not at the first replacement.

Cold. On sites in Northern Quebec, Northern Ontario or the territories, cake moisture is not only a trucking-cost question: it also governs how the cake behaves during handling and outdoor storage in freezing weather. A drier cake handles better; that does not remove the need to heat the building and trace the filtrate and squeeze lines.

A third option: the mixed pack

Many manufacturers offer plate packs alternating chamber plates and membrane plates. You get part of the squeeze effect at an intermediate cost, and on some frames the pack can be upgraded later. It is a common answer when the target moisture is close to what a chamber press can deliver, without certainty.

What to measure before choosing

The right choice is not made on a data sheet: it is made on a filtration test with your slurry. What a serious manufacturer will ask for:

1. A representative slurry sample (several, if it varies), with particle size distribution, solids density and percent solids.
2. The tonnage of solids to process per day and the operating hours.
3. The target cake moisture, with the reason behind it.
4. Any cake washing requirement and the wash ratio.
5. Utilities available on site: compressed air, squeeze water, power.
6. Available space and the cake discharge method (conveyor, bin, truck).

With those inputs, a pressure filtration test, with and without squeeze, gives a moisture-versus-time curve for each option. That curve — not the brochure — decides. We support this selection process through our equipment sales and supply service, and commissioning then sets the real sequence — pressures, squeeze time, air blow — on the press as delivered.

See the Filter presses & hydrocyclones product page for the configurations offered, or request a sizing assessment.

Frequently asked questions

Can a chamber press be converted to a membrane press? Sometimes, by replacing all or part of the plates, provided the frame can take the required closing force and the squeeze circuit can be added. Check with the frame manufacturer before buying plates.

Does a membrane press use more energy? It adds the squeeze consumption (air or water), but a shorter cycle reduces pumping time. The balance depends on the slurry; it is one of the outputs of the filtration test.

How long does a membrane last? It depends on slurry abrasiveness, squeeze pressure and the number of cycles. The manufacturer states it for your application; plan for it in the spare parts list from the purchase onward.