FGD Gypsum Filter Cloth for Horizontal Vacuum Belt Filters
FGD gypsum is the by-product gypsum recovered from wet limestone flue-gas desulphurisation scrubbers. It is commonly dewatered on rubber-belt horizontal vacuum belt filters, where the filter cloth is a consumable endless belt fabricated to the machine's dimensions.
Scrubber gypsum, and why it is its own duty
FGD gypsum is precipitated in a wet limestone scrubber: sulphur dioxide from the flue gas is captured in a limestone slurry, oxidised, and comes out as calcium sulphate. The scrubber bleed is thickened or cycloned and then dewatered, and on many plants that final dewatering step is a horizontal vacuum belt filter.
Two things make the belt a production asset rather than a piece of housekeeping. The scrubber cannot run its water balance without taking gypsum out, so a belt in trouble is a limit on the scrubber. And the cake's value — whether it is sold or landfilled — is decided on the belt, in the wash stage, not downstream.
The cloth is a consumable: an endless belt fabricated to your machine's width and circumference, running on the grooved rubber transporter, and replaced on a cycle that your duty sets.
Same chemical family, different duty. This gypsum comes out of a scrubber and carries chlorides from the scrubber circuit; phosphogypsum comes out of a phosphoric acid plant and brings fluoride with it. At least one established weaver publishes separate belt classes for the two duties rather than a single gypsum belt, and this site keeps them apart for the same reason.
Phosphogypsum vs FGD gypsum →Process flow across the belt
- 01 Slurry Feed Scrubber bleed, usually thickened or cycloned, is fed onto the moving cloth.
- 02 Filtration Vacuum pulls scrubber liquor through the cloth and the gypsum cake forms.
- 03 Washing Wash stages displace scrubber liquor and the chlorides it carries out of the cake.
- 04 Dewatering A dry-vacuum zone pulls the cake down towards its handling moisture.
- 05 Cake Discharge Cake releases at the discharge roller for stacking, landfill or sale.
Stage-by-stage operating values — slurry solids, temperature, wash ratio, residual moisture — are plant-specific. We do not publish typical figures for them; they are on the confirmation list below.
If your gypsum has to meet a wallboard specification
On a lot of plants the person who cares most about the filter belt is not in the power station at all — it is the gypsum or wallboard company that takes the cake.
When the by-product is sold rather than landfilled, it stops being waste handling and becomes a product with an acceptance specification behind it. Chloride carry-over is usually the term everyone argues about, alongside free moisture and purity, because chlorides ride in with the scrubber liquor and the only place on the plant that removes them is the wash stage of the belt filter.
That is what puts the filter cloth in the middle of a commercial conversation. Cake that cracks washes badly; cake that washes badly carries liquor; liquor carries chloride. A cloth chosen only for filtration rate can hit throughput and still fail the acceptance test at the wallboard plant.
We do not publish a chloride limit, a moisture figure or a purity claim. Your limit comes from your off-take specification, not from us. Send us the number you have to hit and the wash configuration you run, and we will work the cloth question backwards from it.
The acceptance specification you are held to, the wash stages currently on the machine, the machine brand and model, and a recent analysis of the cake as it leaves the belt. If the plant that runs the filter is a different company from yours, say so — the answer often involves both of you.
What makes this duty hard on a belt
The liquor is chloride-bearing because it comes out of a scrubber circuit, and the wash stage carries commercial weight. Polymer and finish are chosen against that chemistry; the temperature and chemical window is confirmed in writing for your duty rather than published here as a general figure.
-
Wash efficiency, not just filtration
Wash water channels through cracks in the cake instead of displacing liquor evenly across the belt.
Cloth implication: Cake formation behaviour — which is a weave and finish question — decides whether the wash stage can do its job at all.
-
Blinding by fines and scale
Free area closes as fines and precipitated solids lodge in the fabric; throughput drifts down before anything visibly fails.
Cloth implication: Weave geometry and surface finish set how fast the fabric closes and how much of it recovers on cloth wash.
-
Tracking and wrinkling
The belt wanders on the grooved rubber transporter, contacts the edge guides and the vacuum seal starts leaking.
Cloth implication: Fabricated length, seam squareness and edge treatment all feed into tracking.
-
Seam and joint leakage
A clipper or PAD joint opens, vacuum drops as the joint crosses the box, and the cake wets back.
Cloth implication: Seam type is a specification to be decided against your machine, not a shop default.
-
Cake sticking at discharge
Cake does not release cleanly at the discharge roller and carry-over builds on the return run.
Cloth implication: Surface finish and calendering change release behaviour.
These are the difficulties common to horizontal vacuum belt duty. Which of them bites on your machine depends on numbers we do not have yet — that is what the confirmation list is for.
The machines this duty actually runs on
Horizontal vacuum belt filters are common on FGD gypsum, and they are not the only route. The families below are the ones observed in FGD service, with the evidence level stated as we found it.
| OEM family | Industries observed | Evidence level | Next step |
|---|---|---|---|
| FLSmidth EIMCO Extractor | FGD, minerals | OBSERVED (trade press) | Send brand + model |
| Compositech T-REX / Chemifilter | FGD, chemicals (US) | OBSERVED | Send brand + model |
| EKCP EIMCO-KCP | FGD and phosphate (India) | OBSERVED | Send brand + model |
| Toncin DU | FGD, mining, lithium (China) | Company-reported | Send brand + model |
| WesTech HBF | Minerals, FGD directories | PARTIAL | Send brand + model |
Drum filters also dewater FGD gypsum, and some plants are built that way on purpose. If your gypsum comes off a drum rather than a belt, this page does not apply to you — tell us your machine and we will say honestly whether we can help.
OEM names above are used only to identify the machine a cloth has to fit.
How the cloth is specified for this duty
Selection runs backwards from the slurry. Liquor chemistry and temperature narrow the polymer; particle size and the wash requirement narrow the weave and the surface finish; the machine fixes the dimensions, the seam and the edge treatment. The candidate polymers for horizontal vacuum belt duty are PET monofilament, PET mono/multifilament combinations, polypropylene, double- and multi-layer weave constructions, and hydrolysis- or alkali-resistant specialities.
Which of them belongs on your machine is not something a web page can decide, and a page that tells you otherwise is guessing on your behalf. On this duty the wash requirement usually carries more weight in the decision than raw filtration rate — but "usually" is not your plant, which is why the conversation starts with your data.
Specification status
Our factory specification package has not been confirmed in writing yet, so every parameter reads UNKNOWN. Each 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 |
|---|---|---|---|
| Polymer | UNKNOWN | — | Confirmed against scrubber liquor chemistry |
| Weave / construction | UNKNOWN | — | Confirmed against cake formation and wash duty |
| Air permeability | UNKNOWN | L/dm²/min | Measured per lot; test method and pressure stated on the report |
| Fabric weight | UNKNOWN | g/m² | Reported per lot |
| Seam type | UNKNOWN | — | Confirmed against machine and seam photo |
| Edge treatment | UNKNOWN | — | Confirmed against machine edge seal |
| Max fabricated width | UNKNOWN | mm | Confirmed against loom and machine width |
| Continuous temperature limit | UNKNOWN | °C | Confirmed per polymer and finish |
| Chemical limit (chloride-bearing liquor) | UNKNOWN | — | Confirmed per polymer and finish |
Industry reference — not our specification
| Parameter | Industry reference | Unit | Source |
|---|---|---|---|
| Belt width range seen on this machine family | up to 4500–4800 | mm | Equipment-family observation, third-party machines |
This row describes the machine population, not what we can weave. Our own width limit stays on the UNKNOWN list above until the factory confirms it.
How FGD gypsum belts come off the machine
A failed belt is usually three-way: something in the cloth, something in the machine, and something in the process. Calling it a cloth problem straight away is the fastest route to buying the same failure twice.
Belt tracking and wrinkling
Often machine-side (roller alignment, edge guides) before it is cloth-side.
Diagnose this →Seam / joint failure
Cloth-side and fabrication-side: seam type, squareness, and how the joint was closed on site.
Diagnose this →Cloth blinding
Process-side (fines, scaling, wash balance) interacting with weave choice.
Poor cake release
Cloth surface and discharge geometry together; rarely one or the other alone.
Cloth life on a horizontal vacuum belt filter is duty-specific. Published third-party cases run from weeks to months depending on slurry and machine condition, and we do not quote a life figure before seeing your duty. A supplier who promises you a number of months without asking what you filter is selling, not engineering.
Measuring the old belt and photographing where it failed is the first step in telling the three causes apart. How to measure your old belt →
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. Each item removes a guess from the specification.
| What to confirm | How to get it |
|---|---|
| Machine brand and model | Copy it off the machine nameplate. “Unknown” is an acceptable answer. |
| Belt width | Measure the old cloth across the web, not the rubber transporter. |
| Belt length (circumference) | Measure the endless loop, or give us the machine centre distances. |
| Seam type in use now | Photograph the joint close up — clipper, PAD, or spiral. |
| Photos of the old cloth | Face and back, plus wherever it failed. This is the single most useful thing you can send. |
| What failed | Life, blinding, tracking, seam leak, cake release, or wash quality. Compare against the failure modes above. |
| Slurry temperature and pH | From the process sheet or a recent lab analysis. |
| Where the cake goes | Landfill, stack, cement, or wallboard — and the specification it has to meet if it is sold. |
Question we get asked
Can the same belt run on FGD gypsum and on phosphogypsum?
Treat them as separate specifications. The two slurries come from different processes and carry different chemistry — chloride on the FGD side, fluoride on the phosphogypsum side — and the wash duty is not the same either. A belt fabricated for one may physically fit a machine on the other, which is not the same thing as being the right cloth for it. If you run both duties, send both sets of machine and slurry data and we will quote them separately.
Get an engineering quote for FGD gypsum 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 or a sample plan.
Every belt is fabricated to your machine dimensions — we quote per RFQ. No online checkout.
Samples available — freight terms confirmed per request.
Where to go next
FGD Gypsum Belt Cloth
The cloth family for this duty: weave, polymer, seam, edge and width options.
Phosphogypsum Filtration
A different duty, not a variant of this one — acid-plant origin, fluoride chemistry.
Phosphogypsum vs FGD Gypsum
The two duties side by side, and why one belt does not cover both.
HVBF Compatibility
OEM families, what we can fit, and what we need from each machine.