When Batch Processing Becomes a Constraint
Filter presses, centrifuges, and manual batch systems can create throughput ceilings that are difficult to engineer around. As production demands increase — or as product purity, washing efficiency, and solvent recovery requirements tighten — batch approaches often expose their limits.
Continuous filtration addresses these constraints by combining filtration, cake washing, and drying in a single, automated system. The right platform depends on your slurry, process chemistry, and production targets — which is why BHS testing determines fit before equipment selection.
BHS offers two continuous filtration platforms: the Rotary Pressure Filter for pressure-driven, fully enclosed operations, and the Continuous-Indexing Vacuum Belt Filter for vacuum-based systems with high-throughput and multi-stage washing requirements.
Common Process Challenges
- Throughput bottlenecks Batch cycles limit hourly and daily throughput without operator-intensive workarounds
- Inconsistent cake washing Batch systems struggle to deliver controlled, repeatable washing across every cycle
- Excess solvent and utility consumption Poor filtrate separation and inefficient drying increase operating costs per cycle
- Operator exposure risk Manual discharge and open systems increase exposure for plant teams handling hazardous materials
- Scale-up uncertainty Lab results don’t always translate to production without systematic testing and written scale-up data
- Capital project risk Equipment selection without testing data increases project risk and procurement uncertainty
Continuous Filtration Technologies
Rotary Pressure Filter
The BHS Rotary Pressure Filter (RPF) is a continuous filter for pressure filtration, cake washing, and drying of high-solids slurries with full containment and automatic cake discharge. The technology is based on a slowly rotating drum — less than 2 rpm — with individual cells containing the filter media and isolated process zones.
Filtration is driven by pump pressure of up to 7 barg, with a temperature range up to 200°C. Positive displacement washing or counter-current washing follows filtration. Multiple washing steps, solvent exchanges, steaming, and extraction can also be accomplished. The cake is then dried by blowing hot or ambient-temperature gas through the cake.
The RPF features a uniquely designed discharge system providing for atmospheric discharge from pressure filtration. After automatic cake discharge, the filter cloth is washed and re-enters the feeding/filtration zone, continuing the process. All solvent and gas streams can be recovered separately and reused to minimize consumption.
| TYPE | Filter Area | Drum Ø | Drum Length |
|---|---|---|---|
| RPF P01 | 0.18 m² | 0.75 m | 0.1 m |
| RPF P02 | 0.45 m² | 0.75 m | 0.25 m |
| RPF A03 | 0.72 m² | 1 m | 0.3 m |
| RPF A06 | 1.44 m² | 1 m | 0.6 m |
| RPF A09 | 2.16 m² | 1 m | 0.9 m |
| RPF A12 | 2.88 m² | 1 m | 1.2 m |
| RPF B09 | 3.2 m² | 1.5 m | 0.9 m |
| RPF B12 | 4.3 m² | 1.5 m | 1.2 m |
| RPF B16 | 5.8 m² | 1.5 m | 1.6 m |
| RPF X16 | 6.9 m² | 1.8 m | 1.6 m |
| RPF X20 | 8.6 m² | 1.8 m | 2.0 m |
All specifications apply to high-performance filter with Center Drive. Approximate figures. Subject to modification without notice.
Continuous-Indexing Vacuum Belt Filter
The BHS Continuous-Indexing Vacuum Belt Filter provides vacuum filtration, cake washing, pressing, and drying of high-solids slurries. The technology is based on fixed vacuum trays, continuously feeding slurry systems, and indexing or stepwise movement of the filter media.
Due to the stepwise operation of the belt, washing and drying efficiencies are maximized with the stopped belt and the mechanism of “plug-flow” for gases and liquids. Cake pressing and squeezing further enhance drying. The fixed trays allow for the mother liquor and wash filtrates to be recovered individually and recirculated, recovered, or reused. Steaming and counter-current washing can be integrated into the design.
The BF is available in stainless steel or polypropylene construction, covering an extreme range of chemical compatibility. A completely gas-tight design is available for filtration of flammable materials in a fully inert, closed-loop nitrogen atmosphere.
| TYPE | Belt Width | Length Range | Filter Area |
|---|---|---|---|
| BF 010 | 0.1 m | 1 m | 0.1 m² |
| BF 025 | 0.25 m | 2–5 m | 0.5–1.25 m² |
| BF 050 | 0.50 m | 3–10 m | 1.5–5 m² |
| BF 100 | 1 m | 3–12 m | 3–12 m² |
| BF 150 | 1.5 m | 3–16.5 m | 4.5–24.8 m² |
| BF 200 | 2 m | 4–18 m | 8–36 m² |
| BF 250 | 2.5 m | 6–21 m | 15–52.5 m² |
| BF 300 | 3 m | 6–25.5 m | 18–76.5 m² |
| BF 350 | 3.5 m | 9–30 m | 31.5–105 m² |
All specifications apply to the standard version. Technical data for customized designs may differ. Subject to modification without notice.
Technology Comparison
Both technologies address batch filtration bottlenecks through continuous operation, but each is engineered for different process conditions. BHS testing determines which platform best fits your slurry, washing requirements, and production targets.
| Parameter | Rotary Pressure Filter (RPF) | Indexing Vacuum Belt Filter (BF) |
|---|---|---|
| Drive mechanism | Pump pressure — up to 7 barg | Vacuum — fixed tray, indexing belt |
| Containment | Fully enclosed, gas-tight system | Open or gas-tight / inert N2 design |
| Hazardous / solvent | Well-suited; all streams recoverable separately | Gas-tight design supports flammable materials in inert nitrogen |
| Washing options | Positive displacement, counter-current, multi-step, solvent exchange, steaming, extraction | Overflow, nozzle, counter-current, steaming; filtrates recovered individually by zone |
| Drying method | Gas blowing (hot or ambient temperature) | Vacuum drying, cake pressing/squeezing, gas blowing |
| Active filter area | 0.18 m² – 8.6 m² (standard) | 0.1 m² – 105 m² (standard) |
| Construction | Stainless steel (standard) | Stainless steel or polypropylene |
| Moving parts | Slowly rotating drum (<2 rpm); minimal wear | Stationary filter bed; belt and rollers only |
| Pilot unit | Yes — 0.17 m², up to 6 barg | Yes — open (0.6 m²) and gas-tight (0.5 m²) |
| Typical applications | Fine chemicals, specialty chemicals, pharmaceuticals, pigments, catalysts, solvent-based slurries | Chemicals, food/feed, rare earths, minerals, wastewater, large-volume high-solids slurries |
All specifications subject to change due to development. Equipment suitability is confirmed through process testing and engineering review.
Filtration Process Development
Which Filter Is Right for My Process?
BHS operates a filtration process development laboratory in Charlotte, North Carolina, with bench-scale and pilot equipment available for testing with actual process material. Testing provides engineering and capital project teams with written data on filtration behavior, washing performance, drying characteristics, and scale-up recommendations — before equipment selection.
Pilot RPF and pilot belt filter units are available for testing at BHS or on-site. Results are documented in written test reports to support equipment specification, sizing, and project approval.
For short-term production needs, plant trials, or process validation ahead of a capital purchase, BHS also stocks rental filtration systems in Charlotte.
- Submit Application Data Sheet Provide your slurry description, process requirements, and project timeline to start the testing conversation with BHS engineers.
- Bench-Scale Testing BHS evaluates filtration behavior, cake formation, washing efficiency, and dewatering performance with your process material.
- Pilot Trials Pilot-scale testing on RPF or belt filter equipment generates the data needed for production-scale sizing and confident equipment selection.
- Written Scale-Up Report Test findings are documented with scale-up recommendations and equipment sizing guidance to support project approval.
- Equipment Design & Lifecycle Support BHS supports engineering, turnkey system design, commissioning, spare parts, and long-term service.
Related Resources
Tell Us About Your Process
Share a few details about your slurry and process targets and a BHS engineer will follow up to scope testing, recommend a platform, and answer questions about continuous filtration fit.
A BHS engineer will respond within one business day. For an in-depth submission, you can also send the full Application Data Sheet.