Glossary
Baghouses
Filter cake
Also known as dust cake, filter cake layer.
Filter cake is the dust layer that progressively builds up on the gas-side surface of a filter bag during normal operation. Counter-intuitively, the cake itself performs most of the fine-particle filtration: a fresh bag with no cake has higher penetration than a bag with a developed cake. The art of baghouse operation is to maintain a useful cake without letting it grow so thick that differential pressure climbs unsustainably.
Cake life cycle
- Conditioning — a new or freshly cleaned bag is "pre-coated" by initial dust loading
- Steady-state filtration — the cake builds, ΔP rises slowly, outlet remains low
- Cleaning cycle — pulse-jet, reverse-air or shaker releases part of the cake
- Residual cake — a thin layer remains; ΔP resets but not to zero
- Long-term drift — over many cycles, residual cake gradually thickens, eventually requiring offline cleaning or bag change
How cake behaviour varies
- Coal fly ash — releases relatively cleanly under pulse-jet
- Cement kiln dust — can be sticky, prone to bridging
- Wet or hygroscopic dusts — cake hardens; classic bag-blinding risk
- Sub-micron biomass / WtE ash — fine cake bonds firmly to bag surface
Sonic horns supplement primary cleaning by addressing residual cake before it consolidates.
Related terms
Related terms
- Filter bagA filter bag is the cylindrical fabric sock that traps particulate inside a fabric filter. Media selection depends on temperature, gas chemistry, dust load and cleaning cycle.
- Cake bridging and cake blindingCake bridging is dust connecting adjacent bags so the cleaning pulse no longer reaches the surface. Cake blinding is pore choking that raises ΔP and reduces filtration.
- Bag blindingBag blinding is the choking of filter-bag pores by dust embedded within the medium. It raises differential pressure permanently and is the leading cause of premature bag replacement.
- Differential pressure (baghouse)Differential pressure (ΔP) across a baghouse is the pressure drop between dirty and clean plenums. It is the headline operational KPI: too low signals broken bags, too high signals fouling.
- Pulse-jet cleaning cycleThe pulse-jet cleaning cycle is the firing pattern of compressed-air pulses across a baghouse. Tuned by pulse duration, interval and ΔP set-point to balance cleaning against bag wear.