DUCON® has developed a new RAM (stenter) filter to control emissions
from textile production. Designed to reduce stack opacity caused by sub-micron and larger
particles in the exhaust, this system delivers high efficiency with low operating cost.
For effective emission control, a DUCON® Coalescing Filter System is proposed.
DUCON® uses fiber-bed diffusion filters to capture the sub-micron particles that
drive opacity. Fiber-bed filters are engineered to capture both solid and liquid aerosols
and are used successfully for economical control of enclosure/hood emissions.
Capture mechanisms: Brownian diffusion, inertial impaction, and interception act together.
Inlet Pre-Filter (GF): An indexing pre-filter removes coarse matter such as fibrous lint or waxy components before the exhaust reaches the main filters.
Upstream of the main filter, a rotary drum indexing pre-filter is installed to extend the life
of the fiber-bed main filters by reducing the exhaust load of oil, tar, and lint.
A durable polymer filter medium is wrapped on a drum for continuous service.
Function: Captures oil/tar and coarse contaminants, lowering the load on the main filter and helping keep differential pressure under control.
Construction: The filter medium is wound on a drum and advanced by an indexing mechanism.
Operating principle: As the medium loads, ΔP rises. At a set setpoint, the drive (drum) motor indexes, spooling the spent section and bringing fresh medium into the airstream.
Maintenance: Media rolls can be replaced quickly through access doors; no repacking is required.
Design exhaust flow: Up to 50,000 m³/h per line
Design exhaust temperature: 180–200 °C
Saturated exhaust temperature after cooling: ~30 °C
Clean filter ΔP: ≈ 2 mbar (clean)
Filter change threshold: ≤ 10 mbar (maximum)
Guaranteed stack opacity: reduced to ≤ 5% (typical)
Oils and other volatiles are condensed from vapor to liquid prior to collection.
Cooling the exhaust to ~30 °C is generally sufficient for full condensation. For higher
process loads, a Cyclonic Washer (scrubber) is used.
Cyclonic Washer: Uses adiabatic saturation for cooling. As the exhaust rises through the cyclonic tray, vanes impart swirl. Water is sprayed onto the tray; the resulting turbulence maximizes heat and mass transfer for excellent cooling.
Maintenance/Robustness: Highly plug-resistant design with low maintenance requirements.
Blowdown management: Depending on local regulations, blowdown is sent to sewer or to a wastewater treatment plant.
Long filter life is achieved by designing for low initial ΔP and by correctly sizing
fan static pressure capacity. Because a clean system may require less pressure than the
fan can produce, flow control can be handled in two ways:
Damperless (recommended): A VFD fan drive with closed-loop pressure control lets the fan generate only the pressure required, reducing energy consumption.
With damper: Additional pressure loss is introduced to maintain design flow (secondary choice due to energy penalty).
Pressure signal: Fan speed is automatically adjusted from the static pressure measured at the RAM inlet duct, preserving the internal vacuum–pressure balance.
PLC/HMI: All equipment is PLC-controlled; values are monitored and logged via HMI.
The DUCON fiber-bed RAM filter uses deep-bed microfiber media for sub-micron aerosol control.
It delivers high efficiency in the 0.1–3 µm range, offers low initial ΔP, and provides a long service life.
This is a patented design developed by DUCON specifically for RAM machines and differentiated from competitors.
While optimized for RAM applications, it also performs successfully across a broad range of processes.
Efficiency: 95–99.95% (0.1–3 µm)
Initial ΔP: 150–700 Pa
Typical outlet: < 5–20 mg/Nm³
System elements are validated for maximum performance through shop and field testing.
With proper cooling and face velocity, stack opacity drops to 5% or below; near-zero opacity is targeted in most processes.
The test methodology is defined during design and verified on site with conditioning and acceptance criteria.
As the gas stream passes through the fiber bed, multiple capture mechanisms act simultaneously.
After coalescence, enlarged droplets drain. To extend the life of the final filter, a pre-filter is used,
and hot gases are cooled by a high-pressure Venturi scrubber.
The pre-Venturi scrubber provides effective pre-separation of particulates as well as gas cooling.
Inertial Impaction: ≈ 4 µm and larger particles impact fibers due to inertia and are captured.
Interception: 1–3 µm particles follow streamlines and are intercepted on fiber surfaces.
Brownian Diffusion: Sub-micron (< 1 µm) particles reach fibers via random motion; coalesced droplets then drain.
Cyclonic Washer: Reduces exhaust temperature by adiabatic cooling (water evaporation); return water is distributed onto a cyclonic tray to help wash out solids.
Ambient-Air Dilution Cooling: Dilution with ambient air; regulated via a damper or a temperature controller.
Air-to-Air Heat Exchangers: Counter-flow heat exchange between clean air and hot process exhaust with proper condensate control.
Emission-control systems that clean exhaust from RAM machine stacks will foul over time and therefore require maintenance.
Thanks to DUCON’s careful design, the required maintenance is significantly reduced. When maintenance is needed,
accessibility is a key design attribute.
Access doors: Doors on the upper and lower sections of the unit provide safe, fast entry to the system.
Steam connections: Steam ports at the top and bottom of the vessel can be used for steam quenching/dewaxing and for cleaning the filters—especially useful when waxy compounds are present.
Sloped-to-drain floor: The unit base is sloped toward a drain to facilitate removal of solids that may settle in the hopper.
Pre-filter service: The pre-filter is cleanable and can be removed via the access door for thorough cleaning.
Replacement filters: Supplied installation-ready (pre-packed); no repacking is required.
Side service covers: Convenient side covers provide access to the filter elements; no lifting equipment is required for filter maintenance.
The exhaust gas first enters the cooling stage. Cooling is critical because it condenses most
organics and promotes coalescence of sub-micron particles.
Adiabatic cooling (cyclonic tray washer):Cooling is performed adiabatically on a fixed cyclonic tray using water as the medium.
The cyclonic washer uses turbulent air motion to create aggressive air–water contact and also
removes a portion of larger particulates from the exhaust stream.
Water recirculation and makeup:Cooling water is stored in an integrated tank within the system. To minimize consumption, water is
recirculated, and automatic makeup compensates for evaporation losses.
Pre-filtration (droplet/particle removal):As the cooled air exits the wash tray, it enters the pre-filter. In addition to contaminants,
most water droplets are removed, which lowers the differential pressure across the fiber-bed filters
and protects them from sticky surface loading. As the medium loads, ΔP rises; a
Photohelic® differen
The DUCON® DFY-RF5000 RAM Mist Collector Systems deliver state-of-the-art technology
aimed at boosting your profitability. Whether you operate a single line or multiple plants,
DUCON provides the optimum solution.
In textile production, process exhaust from RAM (stenter) ovens naturally produces visible
“smoke” or blue haze due to the evaporation of light fractions (hydrocarbons).
As these vapors condense, they form sub-micron aerosols that are inherently difficult to capture
with conventional filters.
Dry dust filters: Designed for dry particulate, they do not drain recovered mist well, often causing frequent media changes.
Electrostatic precipitators (ESPs): Surfaces foul quickly, driving maintenance cost and downtime; under unfavorable conditions they can also pose a potential fire hazard.
Wet scrubbers alone: When used as a stand-alone solution on RAM exhaust, they may not consistently achieve the required final clarity/opacity control at high mist loads.
High efficiency, low ΔP: Excellent collection in the 0.1–3 µm range with low initial pressure drop and long service life.
Integrated architecture: Cyclonic adiabatic cooling + indexing pre-filter + fiber-bed coalescing stage for effective sub-micron aerosol removal.
Reduced maintenance: Indexing pre-filter lowers sticky load; fiber-bed drainage minimizes surface loading and extends maintenance intervals.
Scalability: Modular design for single-line or multi-line plants; straightforward retrofit into existing lines.
Compliance ready: Headroom to meet increasingly stringent air-quality requirements over the coming years.
Thanks to the combination of high efficiency and low maintenance cost,
DUCON® RAM Mist Collector Systems are the preferred method for controlling textile
production emissions. By advancing fiber-bed filtration to a new level, DUCON helps ensure
your systems will continue to meet tightening air-quality standards for years to come.