After dewatering ponds, filter press dewatering became the standard in coal and aggregate wash plants. But today, a new standard is taking shape: decanter centrifuges. In this blog, we unpack five reasons why.
Pond vs. Press vs. Centrifuge for Coal & Aggregate Dewatering
| Pond | Filter Press | Decanter Centrifuge | |
| How it works | Underflow is pumped into an open earthen basin, where gravity separates solids over weeks or months | Slurry is pumped into cloth-lined chambers under hydraulic pressure; water passes through as filtrate while cake builds up behind it | A horizontal bowl spins fast enough to generate high centrifugal force, sometimes thousands of times gravity, throwing solids to the wall while a scroll conveys them out as cake |
| Cake dryness | Settled only, no active pressing | Some of the driest cake of any method; a cloth barrier physically catches even very fine particles | Comparable to a press with modern bowl geometry and correctly matched flocculant chemistry |
| Operating style | Passive once pumped | Batch: fill, pressurize, drop cake, wash, repeat | Continuous: material moves through in seconds |
| Biggest drawback today | Land, permitting, and long-term liability | Cloth replacement and maintenance and batch downtime | Performance depends on getting configuration and dosage right |
For coal and aggregate wash plants, cake dryness is mostly a hauling and stacking question. A drier cake weighs less per truckload, stacks more stably, and leaves a wider compliance margin.
READ MORE: Centrifuge vs. Filter Press for Dredging & Tunneling Dewatering
5 Reasons Coal & Aggregate Crews Are Switching From Filter Press to Decanter Centrifuge
Reason #1: Continuous Operation
A filter press runs in batches, and that batch cycle causes most of its downtime. A typical cycle takes one to four hours: fill, pressurize, wait, open the plates, drop the cake, wash the cloths, start over. Because the press can’t accept new feed during that window, every press-based system needs a surge tank built just to hold slurry until the cycle finishes.
A centrifuge doesn’t work in batches at all. Material moves through the bowl in seconds, so feed never has to stop, which means no surge tank, no idle time between cycles, and no capital spent on equipment whose only job is to wait.
Reason #2: No Cloth to Blinding
A filter press separates through a physical cloth barrier, and that cloth is also its biggest maintenance point. Fine coal and aggregate particles clog it faster than coarse material does, a problem called cloth blinding, which slows filtration and forces more frequent washing, sometimes an entire automated cloth-washing system just to keep throughput steady.
A centrifuge has no cloth at all. Separation happens through G-force instead, so there’s nothing to blind and nothing to wash between runs.
That wasn’t always the case. Earlier centrifuge designs, often built around hydraulic drive rather than today’s electric-drive control, lost more ultra-fine material to the centrate than a press’s cloth barrier would have caught. Today’s bowl geometry, when correctly matched with flocculant chemistry, now reaches a solids recovery rate comparable to a filter press.
READ MORE: Lynx 50, 65, 72, and 100: G-Force and Ultra-Fine Separation Performance Compared
Reason #3: Less Hands-On Monitoring
A press needs an operator’s attention through every cycle to check when the cake is ready to drop, track cloth condition, and confirm plates have seated before the next pressurization.
A centrifuge cuts out most of that redundancy. Once it’s configured and tuned to its feed, most current equipment runs on automated controls that adjust in real time, so the constant cycle-by-cycle attention a press demands isn’t needed.
Reason 4: A Smaller Footprint
A large filter press needs a structural steel frame, a poured foundation, and overhead clearance to service the plates. Most decanter centrifuges are compact and typically skid-mounted, so they can go where a press physically can’t.
This matters most on sites where space is already the constraint, such as a dredging barge with fixed deck space, an urban tunneling job working in a confined footprint, or an older plant with no room left for new construction.
Reason #5: A Better Return
Sticker price alone doesn’t tell you which option is cheaper. Total cost of ownership does, and it combines two numbers.
- Capital expenditure (CapEx): what you pay upfront to buy and install the equipment.
- Operating expenditure (OpEx): what it costs to run day after day – energy, labor, wear parts, flocculant – added up over the equipment’s working life.
A press wins on the CapEx side. It costs less to buy, and it draws less energy per cycle since it runs in bursts instead of continuously.
A centrifuge wins on the OpEx side, with less labor per shift, no batch downtime eating into throughput, and no cloth to replace. Cake dryness comes out close to a press when the unit is configured correctly, which keeps hauling and stacking requirements within reach without the batch cycle.
READ MORE: Should You Rent or Buy a Decanter Centrifuge? 7 Factors to Consider
Conclusion
Every operation’s material behaves differently, in particle size, moisture, and abrasiveness alike. How well the equipment, bowl geometry, wear protection, and everything in between are configured to those differences determines whether a switch pays off or falls flat.
Diamond T’s Pilot Program confirms that fit by testing a centrifuge configuration on your plant’s actual material before any installation. From there, you can purchase equipment outright or rent it on flexible terms, whichever fits your plant’s timeline and budget.
As Alfa Laval’s Master Distributor, Diamond T Services operates the largest Lynx fleet in North America, with 48-hour shipping turnarounds nationwide. Contact a Diamond T specialist to discuss your coal or aggregate wash plant application.
