Definition
Particulate matter
Particulate matter is airborne solid or liquid particulate. PM10, PM2.5 and PM1 describe aerodynamic particle size and influence health, monitoring and collection difficulty.
- Subject
- KPIs and measurements
- Also known as
- PM, PM10, PM2.5, PM1, particulate
Particulate matter (PM) is airborne solid or liquid particulate. In industrial emissions control it covers fly ash, cement dust, fume, condensed salts, soot, metal oxides, carbon, mist droplets, and mixed agglomerates carried by the gas stream.
PM categories are based on aerodynamic diameter, not just physical diameter. Aerodynamic diameter reflects how a particle behaves in air, so density, shape, and porosity matter.
| Category | Size basis | Practical significance |
|---|---|---|
| PM10 | 10 micrometres and smaller | Inhalable particulate and a common permit basis |
| PM2.5 | 2.5 micrometres and smaller | Fine respirable particulate, often harder to capture and more health-significant |
| PM1 | 1 micrometre and smaller | Very fine particulate and fume, usually the most difficult fraction for conventional collectors |
Where it appears
Combustion plant produces PM from mineral ash, unburned carbon, condensed metals, sulphates, chlorides, and ammonium salts. Cement and mineral processes produce PM from raw meal, clinker dust, lime, gypsum, kiln bypass dust, and grinding circuits. Steel and non-ferrous processes add iron oxide fume, sinter dust, coke breeze, and flux carryover.
The same total mass can behave very differently depending on size distribution. Coarse dust loads hoppers and causes abrasion. Fine PM drives stack test results, opacity, visible plume risk, filter penetration, and health exposure. Sticky submicron fume can blind a fabric filter even when the mass loading looks modest.
Control and measurement
Baghouses capture PM by forming a dust cake on the filter surface. ESPs charge particles electrically and collect them on plates or tubes. Cyclones and inertial separators remove coarse PM but are weak on fine fractions. Stack testing usually reports filterable PM and, where required, condensable PM or size-specific PM.
PM control is affected by gas temperature, moisture, particle resistivity, inlet distribution, air-to-cloth ratio, specific collection area, rapping or pulse strategy, and whether dust reaches the hopper without being re-entrained. A small increase in fine PM penetration can indicate bag leaks, membrane damage, ESP back-corona, poor ash resistivity, hopper re-entrainment, or fouled internals.
Acoustic cleaning context
Sonic horns improve PM control indirectly. They keep dust from building on collecting plates, catalyst faces, duct ledges, hopper walls, and baghouse surfaces where deposits would later shed, blind, or re-enter the gas stream. Acoustic cleaning is most valuable when the collection device is fundamentally capable but loses performance between mechanical cleaning events.
Measurement and plant context
Particulate matter is measured differently depending on the purpose. Stack compliance may use gravimetric sampling, continuous opacity, triboelectric leak detection, or certified continuous particulate monitors. Process troubleshooting may use hopper catch, ash chemistry, particle-size analysis, differential pressure, fan power, and inspection photographs. These measurements do not describe the same thing: a low stack concentration can still coexist with severe internal fouling if the collector is doing its job but the upstream equipment is dirty.
In combustion plants, operators watch for changes in fuel ash, mill fineness, unburned carbon, ammonium salts, and sulphur compounds because they alter how particles adhere. In cement and metals plants, temperature, alkali cycles, chloride cycles, and recycling of fines can shift dust from free flowing to sticky. Acoustic cleaning has value where the dust is already in suspension or loosely attached, especially around tube banks, hoppers, catalyst faces, and baghouse plenums.
Related terms
Explore the subject
Related terms
4 terms
- Opacity (stack)Opacity is the percentage of light obscured by particulate in stack gas. It is monitored by transmissometer and often tracks ESP or baghouse upset.
- Electrostatic precipitatorAn ESP removes particulate from flue gas by charging dust and collecting it on plate electrodes. Sonic horns are widely used to dislodge ash from plates and to keep hoppers from bridging.
- BaghouseA baghouse is the structural enclosure that holds the bags, cages, tubesheet, cleaning system and hoppers of a fabric-filter dust collector. Sized in compartments for online isolation.
- Mass loadingMass loading is particulate mass per gas volume. It drives ESP and baghouse sizing, hopper load, dust transport, cleaning demand and emissions margin.
References