P84, Nomex and Ryton filter media

P84, Nomex and Ryton filter media are synthetic high-temperature baghouse fabrics used where polyester cannot survive the gas temperature or chemistry. They are selected for a combined duty: continuous temperature, peak excursion temperature, oxygen level, moisture, acid gas exposure, dust abrasiveness, and the ability of the cake to release during cleaning.

P84 is a polyimide fibre. Its irregular, multi-lobed fibre shape gives high surface area and good fine-particle capture, especially when used as a surface layer over a more economical backing felt. It is useful where emissions performance is tight and the dust cake is difficult to stabilise. Its limits are cost and chemical sensitivity in some alkaline or hydrolytic conditions.

Nomex is an aramid felt, widely used on asphalt, cement, and other hot dry gas streams. It handles moderate high-temperature duty well but does not like acid condensation, high moisture at temperature, or strong oxidising conditions. In a plant with unstable dew point control, a Nomex bag can lose strength long before the obvious dust leakage starts.

Ryton is the common trade name for PPS, polyphenylene sulphide. PPS is valued in coal boilers, waste-to-energy, and other acidic flue gas applications because it tolerates sulphur-bearing gas and hydrolysis better than many aramids. It is less tolerant of high oxygen at elevated temperature, so oxygen excursions and air inleakage matter.

Selection implications

The media choice is not just a maximum temperature decision. A baghouse running below the continuous rating can still fail early if acid dew point is crossed, if alkali deposits attack the fibre, if dust abrasion cuts the felt, or if aggressive pulse settings fatigue the bag. The cage finish, snap band seal, bag length, inlet distribution, and cleaning cycle all influence media life.

PTFE membrane can be laminated onto these base fabrics when very low outlet dust or improved cake release is needed. In that case the membrane becomes the primary filtration surface and the base felt provides strength. Damage to the membrane, oil contamination, or sticky dust defeats the purpose by forcing dust into the felt depth.

Acoustic cleaning context

Sonic horns do not replace the pulse system, but they can reduce the amount of cake that becomes compacted between pulses, especially on long bags, hoppers, and plenum surfaces. That matters for premium media because excessive pulsing shortens life. A stable dust cake, lower differential pressure, and fewer high-energy pulses usually give better total value than simply choosing the most expensive fabric.

Selection and inspection context

P84, Nomex, and Ryton are often compared during baghouse upgrades because each one answers a different operating limit. P84 is valued for fine-particle capture and cake release, Nomex for dry hot gas service, and Ryton for many chemically aggressive gases at moderate temperature. The final choice still depends on oxygen, moisture, acid gases, alkali, inlet spark risk, cleaning energy, and the dust's tendency to blind or abrade the fibres.

Useful checks include bag length and snap-band fit, cage finish, seam wear, membrane condition, clean-side dust traces, and differential-pressure trend after each pulse cycle. A bag that looks intact can still fail through chemical embrittlement, hydrolysis, surface glazing, or local abrasion at the cage wires. Acoustic cleaning is most relevant around inlet plenums, hoppers, and dead zones where heavy dust accumulation increases abrasion or re-entrainment; it is not a substitute for choosing media that survives the gas chemistry.

Related terms

• Filter bag
• PTFE-membrane filter bag
• Fibreglass filter bag