4A Zeolite Slurry Filtration and Dewatering Cloth
4A zeolite is a synthetic sodium aluminosilicate crystallised in a caustic liquor and then filtered, washed and dewatered before drying. It is not dewatered on one standard machine — leaf filters and plate presses are common, and one benchmarked filter-media supplier lists zeolite among the duties its belt-filter cloth covers. Each of those takes a physically different cloth, so the first question is which machine you run.
Zeolite is a duty we can quote against, not a market we hold up as our core. The public evidence on which machine 4A plants use is genuinely split, and we would rather say that than write a page that sounds certain. If you run this duty, tell us your machine — that is where the conversation starts, and it is an honest starting point rather than a confident one.
What 4A zeolite slurry is, and where the cloth sits
Zeolite A — 4A in its sodium form — is a synthetic sodium aluminosilicate. Its largest use is as a detergent builder, the role it took over from sodium tripolyphosphate as phosphate was removed from laundry formulations. It is made rather than mined: sodium aluminate and sodium silicate are reacted in a sodium hydroxide solution and the crystals grow hydrothermally in that liquor.
That origin sets the whole filtration problem. Because the particles are crystallised to size rather than produced by grinding, the population is fine and there is little coarse material in it to act as a natural filter aid. And because crystallisation happens in caustic, the solid arrives at the filter suspended in an alkaline mother liquor that has to be washed out, not merely drained off.
So the filter has two jobs, as it does on most washed-cake duties: separate the crystals from the liquor, and displace the residual alkali and soluble silicate out of the cake before it goes to the dryer. Cake moisture leaving the filter is what the dryer then has to pay for.
On a belt machine it is an endless belt with a seam and an edge seal. On a vertical tower press it is an endless zigzag belt with controlled elongation. On a leaf filter or a plate press it is a cut and made-up cover or plate cloth. These are different articles, not options on one product.
Vertical pressure filter cloth →Process flow, in words
- 01 Crystallisation Sodium aluminate and sodium silicate react in caustic solution; zeolite A crystals grow in the liquor rather than being ground to size.
- 02 Filtration The crystals are separated from the alkaline mother liquor. The cake, not the cloth, is the dominant flow restriction on this duty.
- 03 Washing Wash water displaces residual mother liquor — free alkali and soluble silicate / aluminate — out of the cake.
- 04 Dewatering Residual moisture is pulled or pressed out. What leaves here sets the load on the dryer downstream.
- 05 Discharge and drying Cake is released and goes forward to drying and, for detergent grades, on to the builder blend.
The description above is process engineering that holds for the route in general. Operating values for your plant — crystalliser temperature, free alkali, solids, particle size distribution, target cake moisture — are plant-specific, and we do not publish typical figures for them. They go on the confirmation list below instead.
Which filter are you running?
This is the part of the duty that most pages get wrong, so it is worth stating plainly: 4A zeolite slurry is not dewatered on one standard machine, and the public evidence points in more than one direction at once.
Leaf filters and plate presses are common on this duty — a benchmarked competitor's published 4A zeolite content describes a leaf filter, which is a different machine family from the belt machines much of this site is about. Separately, one benchmarked filter-media supplier lists zeolite among the applications for its horizontal-vacuum-belt cloth. Both of those are real observations and they do not contradict each other; they describe different plants. What they mean for you is that nobody can tell you what cloth you need until they know which of these you have in front of you.
| Machine route | Evidence for this route on 4A zeolite | Cloth form it takes | What we need to identify it |
|---|---|---|---|
| Leaf filter / plate press | OBSERVED — published 4A zeolite content from a benchmarked competitor describes a leaf filter | Cut-and-made-up covers or plate cloths, not a continuous belt | UNKNOWN in our equipment map — send the machine and the old cloth |
| Vertical pressure filter (tower press) | Machine family is documented; zeolite service on it is UNKNOWN in our inputs | Endless zigzag, low elongation | Plate size / area + old cloth |
| Horizontal vacuum belt filter | OBSERVED — one benchmarked HVBF technical PDF lists zeolite among its duties | Endless belt, clipper / PAD, edge seal | Brand + model + width + seam photo |
No named plant running 4A zeolite on a belt machine appears in what we were able to verify, and no OEM in our equipment map is recorded in zeolite service. That is a gap in the public record, and we are not going to close it with a guess. If your zeolite plant runs a leaf filter or a plate press, tell us — we will say honestly whether the cloth you need is something we can supply or not.
The equipment pages linked above identify machine families only, so that a cloth can be matched to the machine it has to fit.
What makes this duty hard on a cloth
Whichever machine the plant runs, the difficulty comes from the same place: the particles are fine, they arrive in alkali, and the cake has to be washed rather than just drained.
-
Very fine crystals against the pore
Detergent-grade zeolite A is a synthetic crystalline solid grown to a fine particle size, with little coarse fraction to act as a natural filter aid and build a permeable cake.
Cloth implication: The finer the particle relative to the opening, the sooner solids lodge in the fabric instead of bridging over it. Pore geometry and surface finish decide which of the two happens.
-
Blinding is the central cloth problem here
Open area closes progressively as crystals embed in the fabric; flow falls, cycle time stretches, and the cloth stops recovering after its wash.
Cloth implication: This duty is chosen against blinding first and throughput second. A fabric that filters beautifully on day one and cannot be regenerated is the wrong fabric.
-
Washing has to displace, not channel
A cake of fines has high specific resistance. When it cracks, wash water takes the crack and the mother liquor stays in the cake.
Cloth implication: Even cake formation across the full filtration area is a cloth and machine property together, and it is what decides whether the wash stage does its job.
-
Alkaline mother liquor
The crystals leave the reactor in a caustic liquor, so the cloth sits in alkali for its whole service life, not only during upsets.
Cloth implication: Polyester is subject to alkaline hydrolysis; a liquor that is harmless on a temperature chart can still shorten life chemically. Polymer and finish are chosen against the liquor, not only against the heat.
-
Cake release and carry-over
Cake that does not release cleanly builds up on the return run or the plate face and comes back as blinding.
Cloth implication: A general filtration difficulty rather than a zeolite-specific one, but it compounds the fines problem on this duty.
These are industry-level statements about the duty, not measurements of ours. How severe each one is on your circuit depends on numbers we do not have yet — which is what the confirmation list is for.
How the cloth is specified for this duty
Selection runs backwards from the slurry, with one step in front of it that other duties do not need. First the machine family fixes the cloth form — belt, zigzag, cover or plate — because that decides what article is being quoted at all. Then the liquor chemistry and temperature narrow the polymer; then the particle size distribution and the wash requirement narrow the weave and the surface finish; then the machine fixes the dimensions, the seam or make-up, and the edge treatment.
We are not going to name a fabric for your zeolite filter on a web page. On a fine crystalline duty the trade-off between throughput and blinding resistance is the whole decision, and it is settled against your particle size distribution and your regeneration regime — not from a published table.
Specification status
Our factory specification package has not been confirmed in writing yet, so every parameter reads UNKNOWN. Each one is fixed against your machine and slurry during the engineering review and stated in the quotation — not inferred from this page.
| Parameter | Value | Unit | How it is fixed |
|---|---|---|---|
| Cloth form (belt / zigzag / cover / plate) | UNKNOWN | — | Fixed by your machine family before anything else is discussed |
| Polymer | UNKNOWN | — | Confirmed against liquor chemistry and wash regime |
| Weave / construction | UNKNOWN | — | Confirmed against particle size distribution and duty |
| Air permeability | UNKNOWN | L/dm²/min | Test method and test pressure will be stated with the value, once the mill confirms them in writing |
| Fabric weight | UNKNOWN | g/m² | Reported with the value, once confirmed in writing |
| Surface finish / calendering | UNKNOWN | — | Confirmed against blinding and release behaviour |
| Seam or make-up | UNKNOWN | — | Confirmed against machine and a photo of the existing joint |
| Max fabricated width / plate size | UNKNOWN | mm / m² | Confirmed against machine dimensions |
| Continuous temperature limit | UNKNOWN | °C | Confirmed per polymer and finish |
| Chemical limit (alkali / caustic) | UNKNOWN | — | Confirmed per polymer and finish |
Industry reference — not our specification
| Parameter | Industry reference | Source |
|---|---|---|
| Belt width range seen on rubber-belt vacuum belt machines | 4.5–4.8 m | Equipment-family observation, third-party machines |
That row describes the machine population, not what we can produce. Our own width and plate-size limits are on the UNKNOWN list above until the factory confirms them. Measuring the cloth you are running now is the reliable way to fix the dimensions. How to measure your old belt →
What we can build for this duty
The parameter table above reads UNKNOWN because our own values are not confirmed in writing yet, and we will not fill that table with industry averages. This section is the other half of the answer: the options this cloth is actually built from, what each one changes, and which piece of your data decides it. Nothing below is a specification — it is the shape of the decision.
Cloth form Leaf filter, plate press, vertical pressure filter and horizontal vacuum belt are all used on this duty, and they take different cloth forms — a continuous belt, a zigzag loop, or cut-and-made-up covers and plate cloths. Which one you run is the first thing to settle, and it is not a detail.
Recommended material direction
The crystals are grown in caustic and they arrive at the filter in it, so the cloth sits in alkali for its whole service. That makes alkaline hydrolysis the governing chemistry question rather than a footnote: a liquor that looks harmless on a temperature chart can still shorten life chemically, because the rate climbs with concentration as well as with heat.
This narrows the field; it does not pick. Which polymer goes on your machine is settled against your measured numbers and not on a web page — the same position the selection section above takes. What follows is the reasoning behind that position, not a departure from it.
- Polypropylene PP
Continuous reference up to ~90 °C — a published property of the polymer, not a value of ours
- Acid Excellent
- Alkali Excellent
- Hydrolysis Excellent
- Abrasion Good
Alkali resistance is its strongest property, and caustic is what this duty is. The reference continuous temperature above is the constraint to check against your liquor.
- Polyphenylene sulfide (PPS) PPS
Continuous reference up to ~190 °C — a published property of the polymer, not a value of ours
- Acid Excellent
- Alkali Excellent
- Hydrolysis Excellent
- Abrasion Good
The direction where the liquor is hot as well as caustic. A large cost step that has to be justified by the duty rather than by a preference.
- Polyester (PET) PET
Continuous reference up to ~150 °C — a published property of the polymer, not a value of ours
- Acid Good
- Alkali Limited
- Hydrolysis Limited
- Abrasion Excellent
The reference polymer elsewhere and the one to be careful with here, because alkaline hydrolysis is its published weakness and this liquor is alkaline by construction.
- PA Its alkali resistance is good, so chemistry is not the objection here. What rules it out is that it changes dimension with absorbed moisture, and on a fine caustic duty it brings no advantage — abrasion is not the problem on this feed — to offset that.
What actually decides it Free alkali and the temperature at the filter — and the machine family before either of them, because the cloth form decides what is even being specified.
Everything in this block is reasoning from published polymer behaviour applied to the chemistry described further up this page. It is a direction, not a selection — and the selection is made against your measured numbers during the engineering review, then written into the quotation. The full polymer envelope is on the materials page.
Weave options
Detergent-grade zeolite A is fine and has no coarse fraction to build a helpful cake, so blinding is the headline failure and the surface matters more than it does on a mineral duty.
- Double layer / multi-layer Two or more interlaced fabric layers woven as one. A fine filtering face carried on a coarse structural back — high strength with fine retention, and drainage channels inside the fabric. Watch: Thicker and heavier; more expensive to weave. The usual answer on heavy belt duties.
- Twill The crossing point steps sideways each pick, giving a diagonal rib. More flexible and more permeable than plain at the same yarn count, with better cake release. Watch: Slightly less dimensionally stable than plain.
- Satin Long floats, few crossing points. The smoothest surface of the three, so the best cake release and the easiest to wash back. Watch: Floats snag and abrade; retention is coarser at a given yarn count.
- Plain One over, one under. The most stable and the most rigid. Tight, uniform pores; lower permeability for a given yarn. Watch: Least forgiving of dimensional movement; can blind faster on fine solids.
Yarn form and surface finish are chosen together with the weave rather than after it. Calendering is part of that decision, not a finishing detail applied at the end.
Yarn form. Monofilament washes back best and retains most coarsely; multifilament and staple do the reverse. On a feed with no coarse fraction that choice is the whole argument.
Yarn form, weave and surface finish are settled as one decision. The four yarn forms available are monofilament, multifilament, mono + multi combination and staple / spun.
Permeability considerations
Air permeability is the figure everyone compares and the easiest one to quote meaninglessly. It is measured per ISO 9237 at a stated pressure drop — often 200 Pa — or per ASTM D737 (Frazier). A value with no stated pressure and no stated unit is not comparable to anything, including ours. The same applies to a pore or retention rating: on a woven cloth that is a nominal figure and not an absolute cut-off, because woven media do not have a single pore size and the cake quickly becomes the real filter.
On a blinding-dominated duty the number worth arguing about is not the as-new permeability but how much of it the regeneration wash brings back. Ask any supplier for the method and the test pressure, then ask what the figure is after the wash cycle.
How each property is measured, and what to ask any supplier for alongside the number, is set out on the testing and inspection page. Naming the method is a fact about a public standard, not a claim about our laboratory.
Joint options
The descriptions below are written from belt and loop practice. A leaf cover or a plate cloth does not take a joint at all — it takes a made-up edge — so on those routes this list is context rather than a choice.
- PAD / welded overlap The two ends are overlapped and thermally fused. A smoother, quieter joint that seals better than a clipper and carries load more evenly. Watch: Made off the machine or with a portable press; a change-out takes longer.
- Clipper (metal hook) Interlocking metal hooks crimped onto both cloth ends, joined by a pintle wire. Fitted and replaced on the machine without dismantling it. The fastest change-out. Watch: The joint is a discontinuity: it leaks vacuum as it passes the box, and it is where most belt failures start. Hook material has to suit the liquor.
- Spiral Spiral coils on each end interlaced and pinned. Flexible, drains through the joint, distributes load along the full width. Watch: Adds an open line across the belt — not appropriate where the joint must seal.
- Sewn overlap The ends are overlapped and stitched. Simple and repairable in the field. Watch: The stitch line is the weak point and a leak path. Least common on vacuum belts.
An endless belt takes a joint; a plate cloth or a leaf cover takes a made-up edge instead. Which of these is even the right question follows from the machine, which is why the machine is the first item on the confirmation list.
The four constructions drawn in cross-section: how joints fail and what each one costs you.
Edge treatment
- Cut and sealed The cut edge is thermally sealed against fraying. The baseline. Adequate where the machine edge seal is in good condition.
- Folded / hemmed The selvedge is folded back and secured. Adds thickness and stiffness at the edge where the seal rubs.
- Reinforced edge band A separate band is bonded along the selvedge. For machines that chew edges — the usual answer when a belt keeps failing at the edge while its body is sound.
- Coated / sealed band A polymer band is applied to the edge. Seals the edge against vacuum bypass as well as protecting it mechanically.
- Guide strip / tracking profile A profile bonded to the underside to run in the machine guide. Only where the machine is built for it. Fitting one to a machine that is not is a common and expensive mistake.
For a belt or a loop these are the options. For cut-and-made-up covers the equivalent is how the panel is hemmed, eyeleted or sealed, and that is taken from the cloth you are replacing.
Relevant equipment
Whatever cloth form this duty turns out to need, it is decided at the loom before it is decided anywhere else: what a weaving platform can hold — pick density, tension, width — sets what the finished cloth can be asked to do. Our weaving runs on DORNIER (Germany) and Sulzer (Switzerland) platforms, machines built for technical textiles rather than for apparel.
Fine caustic duty puts the weight of the decision on construction and finish — both set upstream of anything that can be adjusted on site.
Model designations, working widths and installed quantities are being confirmed against the machine nameplates and are not published until they are. A weaving platform is easy to name and hard to fake, and we would rather you were able to check.
The full platform description, the eleven process stations from yarn to crate, and the nine laboratory checks: manufacturing.
Factory capability for this duty
The rows below are the part of our capability envelope that this duty touches. The last group is the one that makes the rest of it worth reading — a supplier who can do everything has told you nothing.
Machine families
- Rubber-belt horizontal vacuum belt filter Built to your spec
Core family. Endless belt with clipper, PAD or spiral joint and a finished edge.
What decides it Brand and model, measured width and developed length, a photograph of the joint.
- Vertical / tower / stacked pressure filter Built to your spec
Core family. Endless low-elongation zigzag loop.
What decides it Plate dimensions or filtration area, plus the cloth you are replacing.
- Drum, disc, leaf or chamber press Engineering review
Not our default family. We ask what machine you run before saying anything about cloth.
What decides it The machine family, confirmed first.
- Indexing / tray vacuum filters Not offered
Different cloth mechanics. We will tell you so rather than sell you a belt that does not fit.
What we do not do
- Quoting from an industry name alone Not offered
Two plants in the same industry run different slurries through different machines. We ask which.
The full envelope, including the machine families and services we decline: what we build to order and what we will not take on. Fifteen pages on how a specification like this is built and read: the filter cloth specification guide.
How zeolite cloths come off the machine
On a fine crystalline duty most of the failures collapse into one root cause with different symptoms. Diagnosing it as a fabric quality problem alone is the fastest way to buy the same failure twice.
Cloth blinding
The headline failure on this duty. Fines embed, open area closes, and the cloth stops recovering after its regeneration wash.
Diagnose this →Mother liquor carry-over
Process-side and cloth-side together: cake cracking, wash distribution, and how evenly the cake forms.
Diagnose this →Short life in alkali
Chemical rather than mechanical. Shows up as strength loss across the whole cloth, not as local wear.
Diagnose this →Wrong cloth form for the machine
An endless belt does not fit a leaf filter and a plate cloth does not fit a belt. This is a specification error, not a quality failure.
Diagnose this →Cloth life on a fine crystalline duty is set by how fast the fabric blinds and how well it regenerates, both of which are plant-specific. We do not quote a life figure before seeing your duty. Anyone who offers you a number of months without asking about your particle size distribution and your wash regime is selling, not engineering.
What we need from you to quote
This list is the engineering RFQ in plain form — what you gather here is exactly what the form asks for. On this duty the first line is the one that matters most, because it decides what kind of article is being quoted at all.
| What to confirm | How to get it |
|---|---|
| Which machine family | Leaf, plate press, vertical pressure filter, or horizontal vacuum belt. If you are not sure, a photo of the machine plate and of the filter itself settles it. |
| Machine brand and model | Copy it off the nameplate. “Unknown” is an acceptable answer. |
| Dimensions of the cloth in use now | Belt width and circumference, or plate size / filtration area, depending on the machine. |
| Seam or make-up in use now | Photograph the joint or the made-up edge close up. |
| Photos of the old cloth | Face and back, plus wherever it failed. This is the single most useful thing you can send. |
| What failed | Blinding, wash quality, cycle time, strength loss, or release. Compare against the failure modes above. |
| Liquor chemistry and temperature | Free alkali, slurry temperature, and solids content from the process sheet or a recent lab analysis. |
| Particle size distribution | From your own QC data if you have it. On this duty it matters more than on a coarse mineral slurry. |
Before you enquire
Do you have a standard 4A zeolite filter cloth?
No, and on this duty that is the correct answer rather than an evasive one. The cloth form alone differs between a leaf filter, a plate press, a vertical pressure filter and a vacuum belt filter — those are four different articles. Tell us the machine first; the fabric discussion only makes sense afterwards.
Is zeolite one of your main markets?
It is not, and we would rather write that down than imply otherwise. Our published material on belt filters is strongest on gypsum duties. Zeolite is a duty we can quote against once we know your machine, and we will tell you plainly if what you need is outside what we can supply.
Get an engineering quote for 4A zeolite duty
Three steps after you submit: an engineer checks what you sent against the machine, we come back for anything missing, and you get a quotation, a sample plan, or a straight answer that this one is not for us.
Every cloth is made to your machine dimensions — we quote per RFQ. No online checkout.
Samples available — freight terms confirmed per request.
Where to go next
Vertical Pressure Filter Cloth
Endless zigzag cloth for tower press machines — one of the routes this duty runs on.
HVBF Filter Cloth
The belt family: weave, polymer, seam, edge and width options.
Cloth Blinding
The central failure on fine crystalline duties — how to tell it apart from wear.
Vertical Pressure Filters
Machine families, what we can fit, and what we need from each machine.