Waste-to-energy and biomass
Wood pellet
Also known as wood pellets, industrial wood pellet.
Wood pellets are densified biomass-fuel pellets, typically 6–10 mm in diameter and 10–40 mm long, manufactured by milling and pressing wood residues without binder. Industrial wood pellets are the dominant biomass fuel for utility-scale co-firing and for dedicated biomass conversions of former coal-fired power stations (Drax Power Station in the UK is the largest example).
Pellet-silo bridging
Wood-pellet storage silos at biomass power plants are notoriously prone to bridging and rat-holing:
- Pellets self-heat in storage, releasing volatile organics that bind adjacent pellets
- Mechanical compression in tall silos breaks pellets into fines that consolidate
- Moisture absorption from atmospheric humidity worsens cohesion
- Self-ignition is a documented fire hazard requiring inertisation
Sonic horns at silo discharge points provide continuous flow promotion without the mechanical impact of air cannons, which is particularly valuable on tall silos where structural stress matters.
Fouling
Wood-pellet combustion produces moderate alkali ash typical of biomass operation — slagging on the radiant section, fouling on the convective pass. Less chlorinated than waste-derived fuels.
Related terms
Related terms
- SiloA silo is a large vertical bulk-solids storage vessel. Cement, fly-ash, lime, biomass, fertilizer and food-powder silos all bridge and rat-hole; sonic horns are the leading flow aid.
- Bridging (bulk-solids)Bridging (also arching) is the formation of a stable arch of bulk solids above the discharge outlet of a hopper or silo, stopping material flow. The universal failure mode of bulk-solids storage.
- Alkali metals in ashAlkali metals (Na, K) in biomass and waste-fuel ash form low-melting compounds that bond to boiler tubes as sticky deposits and poison SCR catalysts.
- BoilerA boiler is a vessel that converts fuel chemical energy into steam by heating water. Coal-fired, biomass, oil, gas and recovery boilers all foul; sonic horns clean heat-transfer surfaces.