Industrial acoustic cleaning glossary

Acoustic impedance is the resistance a medium offers to the flow of acoustic energy. Impedance mismatches between media reflect energy; matching is the reason sonic horns use an exponential bell.

Acoustic streaming is the steady (DC) flow induced in a gas or fluid by an intense oscillating sound field. It contributes to particulate dispersion in industrial acoustic cleaning.

Attenuation is the loss of acoustic energy as a sound wave propagates. Higher frequencies attenuate faster, which is why low-frequency sonic horns reach further in industrial vessels.

The decibel is a logarithmic ratio used to express sound pressure, sound intensity and sound power. A 10 dB rise represents a tenfold rise in intensity.

Frequency is the number of acoustic cycles per second, measured in hertz. Industrial acoustic cleaners operate at 12-30 Hz (infrasonic), 60-250 Hz (low) or 250-450 Hz (high).

The fundamental frequency is the lowest natural resonant frequency of a system. For a sonic horn it is the published nameplate frequency at which the horn delivers maximum cleaning energy.

A harmonic is an integer multiple of the fundamental frequency. A sonic horn radiates energy mainly at its fundamental, with progressively less at higher harmonics.

In a free field, sound intensity falls with the square of distance and sound pressure level drops by about 6 dB for each doubling of distance.

The near field is the complex zone close to a horn. The far field is where sound behaves more predictably and distance-based level estimates apply.

An octave band is a frequency range with a two-to-one edge ratio. Octave-band data is essential for sonic-horn noise, attenuation and hearing-protection work.

Resonance occurs when a driving frequency matches a natural mode of a system. Acoustic cleaning uses controlled coupling while avoiding damaging vibration.

Sound power is the acoustic energy emitted by a source. Sound pressure is the local pressure fluctuation measured at a point and depends on distance and surroundings.

SPL is the logarithmic measure of local sound pressure relative to 20 micropascals. It is used for horn output checks, workplace noise and acoustic-cleaning surveys.

A standing wave forms when reflected sound interferes with incoming sound, creating fixed pressure nodes and antinodes that affect acoustic-cleaning coverage.

Wavelength is the distance a sound wave travels in one cycle. It controls how sonic-horn energy diffracts around tube rows, baffles and large process internals.

Detonation cleaning uses a controlled pulse-detonation device to generate high-energy shock waves that dislodge boiler deposits. Best-known commercial offering is Bang & Clean.

Dry-ice blasting projects solid CO2 pellets onto a surface; the pellets sublimate on impact, leaving only the dislodged material as secondary waste. Common for offline boiler cleaning.

Explosive deslagging uses controlled charges of solid explosive to fragment severe boiler slag during outages. Specialised contractor service; permit-heavy; for the toughest cases.

Hydroblasting uses high-pressure water to remove hardened deposits during outages. It is powerful offline cleaning, but it adds access, drying, effluent and safety constraints.

An IK sootblower inserts a rotating steam lance into the boiler gas path, cleans tube banks, then retracts. It is powerful but consumes steam and can erode tubes.

An IR rotary sootblower is a fixed, rotating steam or air lance for local tube-bank and air-heater cleaning where a long retract blower is unnecessary or impractical.

Manual lancing is direct operator cleaning with rods, water lances or tools. It is labour-intensive, hazardous and usually a last-resort method.

Online cleaning happens during operation. Offline cleaning requires shutdown. Industrial cleaning strategy balances prevention, deposit removal, safety and lost production.

A retract sootblower inserts a lance into the boiler for cleaning, then withdraws it to protect the lance from continuous high-temperature exposure.

A shock-pulse generator creates high-energy pressure pulses for boiler cleaning. It is used for periodic deep cleaning, especially in difficult recovery-boiler deposits.

A steam sootblower uses a high-velocity steam jet to remove ash and slag from boiler heat-transfer surfaces, with erosion and steam-use trade-offs.

A venturi scrubber accelerates dirty gas through a throat where liquid droplets capture particulate by impaction, with pressure drop setting collection intensity.

A water cannon fires controlled water jets at boiler waterwall slag, cracking deposits by thermal shock while requiring careful control of tube fatigue risk.

A water lance is a fixed, mechanised or handheld water-jet cleaning tool used for slag, build-up and outage cleaning where thermal shock or hydraulic force is needed.

Air-to-cloth ratio is the gas volumetric flow rate divided by total bag filtration area. It is the primary baghouse sizing parameter and a strong predictor of bag life and deltaP.

Bag 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.

A bag cage is the welded wire frame that holds a filter bag open against differential pressure inside a pulse-jet baghouse. Cage corrosion or breakage causes immediate bag collapse.

A 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.

Cake bridging is dust connecting adjacent bags so the cleaning pulse no longer reaches the surface. Cake blinding is pore choking that raises delta P and reduces filtration.

Can velocity is the upward gas velocity in the space between filter bags. High can velocity re-entrains just-released cake; design limits are around 1.5-2.5 m/s.

Compartment isolation is the procedure of closing inlet and outlet dampers on one baghouse compartment so it can be cleaned or have bags replaced while the rest stays online.

Differential pressure (delta P) 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.

A fabric filter removes particulate from a gas stream by passing it through woven or felted bag media. Sonic horns supplement primary cleaning and reduce differential pressure.

A fibreglass filter bag is woven from glass-fibre yarn and rated for continuous service to 260 deg C. The standard bag for coal-fired utility reverse-air baghouses and high-temperature cement duty.

A 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.

Filter cake is the dust layer that builds up on the surface of a baghouse filter bag. The cake itself does most of the fine-particle filtration; cleaning balances cake build-up against differential pressure.

P84, Nomex and Ryton are common high-temperature synthetic filter media for baghouses. Selection depends on temperature, oxygen, acid gas, moisture and dust release.

A PTFE-membrane filter bag has a microporous PTFE membrane on a base felt. Dust is captured on the surface, improving fine-particle control and cake release.

A plenum is a gas-flow chamber in a baghouse. The dirty side contains dust-laden gas, while the clean side receives filtered gas after it passes through the bags.

A pulse-jet baghouse cleans filter bags with brief compressed-air pulses while the collector remains online. It is the dominant modern fabric-filter design.

The pulse-jet cleaning cycle is the firing pattern for compressed-air bag cleaning. It balances pressure drop control, emissions stability and bag life.

A reverse-air baghouse cleans bags by isolating a compartment and flowing low-pressure clean air backwards through the bags.

A shaker baghouse cleans bags by mechanically shaking the support frame during offline cleaning. It is a legacy fabric-filter design for lighter duties.

The acid dew point is the temperature at which sulphuric acid condenses from flue gas containing SO3 and water vapour. Cold-end metal temperatures must be kept above it.

An air heater (also air preheater, APH) recovers low-grade heat from flue gas to preheat combustion air. Cold-end fouling and corrosion are the dominant operational challenges.

AFBC is the umbrella term for atmospheric-pressure fluidised-bed boilers, including both bubbling-bed (BFB) and circulating-bed (CFB) designs.

An attemperator (or desuperheater) sprays demineralised water into superheater steam to control outlet temperature. Falling attemperation is a leading symptom of superheater fouling.

A 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.

Boiler tube failures are the leading cause of forced outages on industrial boilers. Causes range from creep and erosion to corrosion and overheating; cleaning practices contribute to several.

A BFB boiler suspends fuel in a slowly-bubbling bed of inert solids. Lower fluidisation velocity than CFB; suited to high-moisture biomass and sludges.

A CFB boiler burns fuel in a turbulent bed of sand, ash and limestone circulated by an upward-flowing gas stream. Tolerates coal, biomass, RDF and lignite; produces low NOx.

Cold-end corrosion is the attack on air-heater and economiser surfaces below the acid dew point, where SO3 condenses as sulphuric acid. The leading cold-end failure mechanism.

The convective pass is the downstream section of a boiler where heat transfer is by conduction across tube banks: superheater, reheater, economiser. The primary zone for sonic-horn cleaning.

An economiser is the final tube bank in a boiler's convective pass that recovers heat from the flue gas by preheating feedwater. Ash bridging in the economiser is a routine cleaning challenge.

The furnace is the radiant chamber of a boiler where fuel burns at 1,300-1,700 deg C. Waterwalls absorb the radiant heat; molten slag is the dominant fouling concern.

The generating bank is the array of evaporator tubes between the steam and mud drums of a recovery boiler, performing bulk heat absorption from cooling flue gas.

Heat rate is the fuel energy required to produce one unit of electrical output, measured in BTU/kWh or kJ/kWh. Fouling on convective surfaces directly degrades heat rate.

A hog-fuel or bark boiler burns wood residues, bark and screened biomass to provide auxiliary steam at pulp mills, complementing the kraft recovery boiler.

A Ljungstrom air preheater rotates heat-transfer baskets between flue gas and combustion air. Cold-end fouling, ABS, corrosion and leakage drive maintenance.

A pulverised-coal boiler grinds coal to fine powder and burns it through burners in a furnace. Ash behaviour drives slagging, fouling, ESP duty and cleaning design.

A recovery boiler burns black liquor to generate steam and recover pulping chemicals. Ash deposition, smelt safety and tube cleanliness are central operating concerns.

A reheater raises the temperature of steam returning from the high-pressure turbine before it enters the intermediate-pressure turbine.

These boiler classes describe steam pressure and temperature regimes, affecting efficiency, materials, waterwall design and fouling sensitivity.

A superheater raises saturated steam above saturation temperature and is a critical boiler surface for efficiency, tube metal temperature and fouling control.

Tube erosion and wastage describe boiler tube metal loss from ash impact, sootblower jets, corrosion under deposits and aggressive cleaning.

Tube fouling is deposit build-up on boiler tubes, reducing heat transfer, increasing draft loss and raising corrosion or tube-temperature risk.

A tubesheet is the thick plate that holds tube ends in a shell-and-tube exchanger, waste-heat boiler or similar heat-transfer vessel.

A tubular air preheater transfers heat from flue gas to combustion air through fixed tubes and is vulnerable to ash fouling, acid dew point corrosion and plugging.

A waste-heat boiler recovers heat from hot process gas to generate steam, with fouling, erosion, tubesheet stress and corrosion driving cleaning strategy.

Waterwalls are gas-tight evaporator tube panels lining a boiler furnace. They absorb radiant heat, generate steam and face slagging, corrosion and tube-wastage risks.

Alternative fuels (AFR) replace fossil fuel in cement kilns. They cut CO2 emissions and waste-disposal cost but increase chlorine, sulphur and alkali loading in the kiln gas.

Build-up, coating and accretion are interchangeable terms for accumulated deposits on cement-plant gas-path surfaces. The leading cause of kiln stops in cement manufacture.

A calciner is a combustion chamber in the cement preheater tower where raw meal is pre-calcined (CaCO3 to CaO) before entering the rotary kiln. Common site for AFR firing.

A chloride bypass extracts a slipstream of kiln gas before the preheater to remove chlorine from the recirculating Cl cycle. Essential at high TSR; the bypass duct itself fouls heavily.

Clinker is the dark, hard nodular intermediate product of cement manufacture, formed by burning raw meal at 1,450 deg C in the rotary kiln before grinding to cement powder.

A clinker cooler quenches hot clinker discharged from the rotary kiln using forced ambient air. Hot air recovered is sent to the calciner via the TAD; cooler dust hoppers benefit from sonic horns.

The kiln inlet and riser duct connect the rotary kiln to the calciner and preheater. This hot, dusty zone is highly prone to build-up and acoustic-cleaning retrofits.

A kiln-inlet ring or snowman is a large accretion at the cement kiln inlet. It is driven by alkali, sulphur and chloride cycles and can force kiln stops.

A preheater cyclone separates hot raw meal from kiln exhaust gas. Lower-stage cyclones face heavy build-up, pressure loss and blockage risk.

A preheater tower is a stack of cyclone stages that heats raw meal with kiln exhaust gas before the meal enters the calciner and rotary kiln.

RDF, SRF and TDF are waste-derived fuels used in cement kilns, lime kilns and waste-to-energy plants. They affect ash chemistry, chlorine, moisture and deposits.

Raw mills grind kiln feed, cement mills grind clinker and gypsum, and coal mills grind fuel. Each creates dust-control and deposit-control duties.

A rotary kiln is an inclined rotating refractory-lined cylinder used for cement clinker, lime, pellets and minerals. In cement, it burns meal into clinker.

A tertiary air duct carries hot combustion air from the clinker cooler to the precalciner in a cement kiln system and is prone to build-up and abrasion.

Thermal substitution rate is the share of cement kiln heat supplied by alternative fuels rather than conventional fossil fuels.

A vertical roller mill grinds raw meal, coal, clinker or slag using rollers on a rotating table, with integrated drying, classification and dust handling.

An air receiver buffers the pulse demand of sonic horns from the upstream compressor. Correct sizing prevents SPL drop-off during multi-horn firing cycles.

Filtering particulate and drying moisture from compressed air extends sonic-horn diaphragm life by preventing internal corrosion and abrasion.

A cycle controller programmes the firing pattern of one or more sonic horns - duration, interval, sequence, zone grouping. Either a dedicated standalone unit or a PLC subroutine.

Diaphragm replacement is the routine maintenance task for industrial sonic horns. Typical interval 3-5 years for titanium, 1.5-3 years for stainless. Field-replaceable in under an hour.

A DCS is the plant-wide process-automation system with operator workstations, controllers and field-device networks. Sonic horns typically integrate via fieldbus to the existing DCS.

Instrument air is dried, filtered air for controls. Plant air is general utility air. Sonic horns can use either if pressure, dryness and flow are adequate.

Modbus, Profibus and Profinet are common industrial communication protocols used to integrate sonic-horn controllers with PLC and DCS systems.

Predictive maintenance schedules service from condition signals rather than fixed intervals. For cleaning systems, useful signals include pressure, sound level and valve response.

A PLC is a rugged industrial controller used for interlocks, sequencing, alarms and plant integration. Sonic horn systems may use a dedicated PLC or the site control system.

RCM is a structured method for deciding maintenance tasks from asset functions, failure modes, consequences and detection methods.

A solenoid valve admits compressed air to a sonic horn on command from the controller. Correct sizing, air quality and hazardous-area certification drive reliable cleaning.

A sound-attenuation enclosure surrounds a sonic horn to reduce operator and boundary noise while preserving access, ventilation and acoustic output into the vessel.

An acoustic cleaner is any device that uses high-intensity sound waves to dislodge particulate fouling from inside industrial process equipment such as boilers, ESPs, baghouses and silos.

An acoustic cleaning system is the engineered assembly of sonic horns, compressed-air supply, solenoid valves and cycle controllers that delivers programmed acoustic cleaning to industrial process equipment.

Acoustic cleaning uses audible low-frequency sound to clean industrial process equipment in situ. Ultrasonic cleaning uses high-frequency sound in a liquid bath to clean small parts off-line. They are different technologies for different jobs.

An acoustic horn is the broader term for any low-frequency horn-shaped sound emitter used in industrial cleaning. In commercial practice it is interchangeable with sonic horn.

A bell horn is the conical or exponential flare that amplifies and projects sound from an industrial sonic horn's driver into the vessel being cleaned.

A diaphragm horn is a sonic horn whose sound is generated by a vibrating titanium or stainless-steel diaphragm driven by pulsed compressed air. The dominant form-factor for low-frequency industrial cleaning.

High-frequency acoustic cleaners operate at 250-450 Hz. The shorter wavelength carries more energy per unit volume and suits fabric filters, SCR catalysts and small hopper geometries.

An industrial sonic horn is a pneumatic low-frequency acoustic cleaner used to prevent dust and ash build-up inside process equipment.

An infrasonic cleaner uses very low frequency acoustic energy to clean large, obstructed vessels where long wavelength and low audible noise are valuable.

Low-frequency acoustic cleaners use long-wavelength sound to clean large, obstructed industrial vessels such as ESPs, boilers, hoppers and cement preheaters.

A piston-whistle horn generates sound with a moving piston or rotating disc rather than a diaphragm. It is used where high-frequency acoustic energy is preferred.

A pneumatic acoustic cleaner is a sonic horn driven by compressed plant air. It produces short acoustic bursts to loosen dry particulate deposits in process equipment.

Sonic blower is an informal term for a pneumatic acoustic cleaner or sonic sootblower used to keep boiler, ESP, duct and silo deposits from building up.

A sonic horn is a pneumatic low-frequency sound emitter used to dislodge particulate fouling from boilers, ESPs, baghouses, ducts and silos while the plant stays online.

A sonic sootblower is a sonic horn applied to boiler and heat-recovery surfaces. It uses pulsed sound rather than steam-jet impingement to prevent ash build-up.

A titanium diaphragm is the vibrating metal element in many sonic horns, selected for fatigue strength, corrosion resistance and stable acoustic output.

Back-corona is reverse ionisation through a high-resistivity dust layer on ESP collecting plates. It collapses collection efficiency and is mitigated by keeping plates clean.

The collecting electrode is the grounded plate or tube on which charged particulate accumulates inside an ESP. Dust must be released to hoppers without re-entraining into the gas stream.

Corona discharge is the electrical breakdown around an ESP's discharge electrode that ionises gas molecules and charges dust particles for collection.

The discharge electrode is the high-voltage electrode that generates the corona discharge inside an ESP. Charged dust drifts from it to the collecting plates.

An ESP field (or bus section) is an independently energised electrical zone of an ESP, with its own transformer-rectifier set, discharge electrodes and rapper group.

An ESP hopper is the inverted-pyramid vessel below each ESP field that collects rapped-down fly ash. Bridging and rat-holing are common failures; sonic horns are the standard mitigation.

The ESP penthouse is the gas-tight compartment above the plate stack that houses the rappers, high-voltage bus insulators and discharge-electrode support frames.

An ESP rapper is the mechanical hammer or magnetic impulse device used to dislodge accumulated dust from ESP plates and discharge electrodes. Sonic horns complement and partly replace this duty.

An 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.

A fly-ash hopper collects particulate ash from ESP, baghouse, economiser and air-heater equipment. Bridging and rat-holing of fly ash are persistent operational problems.

Fly-ash resistivity is the electrical resistance of a deposited dust layer. Very high or very low resistivity can both reduce ESP collection performance.

Hot-side ESPs sit upstream of the air heater at high temperature. Cold-side ESPs sit downstream. The choice affects ash resistivity, gas volume, corrosion and cleaning design.

A MIGI rapper lifts and drops a plunger onto an ESP anvil rod. It gives tunable impact cleaning but needs maintenance, sequencing and support from hopper cleaning.

Plate-type ESPs use parallel collecting plates. Tube-type ESPs use cylindrical or polygonal collectors, often in wet ESP and mist applications.

Re-entrainment occurs when collected dust is knocked or lifted back into the gas stream before reaching the hopper. It causes opacity spikes and lower net collection.

Sneakage is flue-gas flow that bypasses the active ESP collection field through hoppers, casing gaps or spaces around the electrode zone.

Specific collection area is the total ESP collecting area divided by gas flow. It is a core sizing and performance indicator for dry electrostatic precipitators.

A tumbling-hammer rapper is a mechanical ESP rapping device that strikes collecting plates or discharge frames to shed dust into the hoppers.

Turning vanes guide flue gas through ESP inlet turns and expansions. Fouling, erosion or misalignment can disturb gas distribution and reduce collection performance.

A wet electrostatic precipitator washes its collecting surfaces and is used for acid mist, sticky aerosols, fine particulate and saturated flue-gas applications.

Coking is the formation of hard carbonaceous deposits on hot process surfaces, typically inside ethylene crackers, delayed cokers and refining heaters. Removed by decoking campaigns.

A derate is operation below nameplate capacity because a limiting condition has been reached. Fouling-driven derates from ID fan, delta P or boiler tube limits are common.

A forced outage is an unplanned shutdown of an industrial unit, typically triggered by equipment failure or pressure-vessel safety conditions. The dominant economic cost of poor cleaning practice.

Fouling is the accumulation of unwanted deposits on process-equipment surfaces. The general umbrella term covering slagging, scaling, coking, sintering and many other specific mechanisms.

Heat-transfer surface fouling describes tube fouling from the economic-impact angle: thermal-resistance addition that reduces heat absorption and degrades plant heat rate.

Scaling is mineral deposition on heat-transfer or flow surfaces, commonly from dissolved salts coming out of solution as temperature or chemistry changes.

Deposit sintering is the bonding of fouling particles into harder consolidated layers under heat. Early cleaning is easier than removing sintered deposits.

Slagging is the formation of molten or semi-molten ash deposits on high-temperature furnace surfaces. It differs from cooler dry fouling.

Sulphur, chloride and alkali species circulate through boilers and kilns, driving sticky ash, corrosion, deposits and cleaning demand.

An air cannon is a pressure-vessel and quick-release-valve assembly that fires a brief high-pressure air pulse into a hopper or silo to break material bridges. Effective but causes structural stress.

An anti-bridging device is any flow-aid hardware installed to prevent or break material bridging in a hopper or silo: sonic horns, air cannons, vibrators, fluidisation pads.

A bin is a small-to-mid bulk-solids storage vessel. The term is used loosely; in industrial practice bins, hoppers and silos overlap in usage.

A bin vibrator is a pneumatic or electric vibrator bolted to the outside of a hopper or silo to dislodge bulk-solids bridges. Compact but can compact wet powders and stress the vessel.

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.

A coal bunker is an intermediate coal-storage vessel that feeds pulveriser mills. Bridging in coal bunkers interrupts mill feed and forces unit derates; sonic horns are the standard flow aid.

The discharge cone is the converging lower section of a hopper or silo. Cone angle and surface finish determine whether the vessel delivers mass flow or funnel flow.

Fluidisation pads are porous panels mounted on the lower hopper wall that admit low-pressure air to aerate the material above. Effective on dry Class-A powders; problematic on wet material.

The Geldart classification groups powders by particle size and density into A, B, C and D classes. Predicts fluidisation, bridging and discharge behaviour.

A hopper is a converging vessel for bulk solids discharge. Its reliability depends on flow pattern, wall angle, outlet size, moisture, ash cohesion and flow-promotion design.

Mass flow moves all material toward the outlet. Funnel flow draws a central channel and leaves stagnant zones that cause ageing, ratholing and bridging.

Material flow promotion combines hopper design, outlet sizing and retrofit flow aids to prevent bridging, ratholing, stagnant zones and unreliable discharge.

Rat-holing is a silo flow problem where material discharges through a narrow channel while surrounding material remains stagnant and consolidates.

A silo stores bulk solids such as cement, fly ash, lime, coal, biomass and powders. Flow design determines whether the stored material discharges reliably.

Whip hammering is the legacy practice of striking hopper or silo walls to break material bridges, with safety, structural and reliability drawbacks.

A CCGT plant combines a gas turbine with a steam turbine driven by an HRSG recovering exhaust heat. Plant efficiency reaches 55-62% LHV; HRSG cleanliness is critical.

The cyclone dipleg is the vertical pipe at the bottom of a cyclone separator that carries separated solids back to a hopper or recirculation circuit. Pluggage is a chronic operational issue.

A cyclone separator removes particulate from a gas stream by centrifugal force. Wall build-up and re-entrainment from the dipleg are the dominant operational issues.

Dampers route, isolate or modulate flue-gas flow. Diverter dampers swing flow between paths; louvers throttle; guillotines fully isolate. Fouling causes sticking, seal failure and bypass.

A duct burner is an auxiliary gas burner installed in the HRSG inlet duct to add heat to the gas-turbine exhaust. Used for steam-flow boosting and cogeneration peak shaping.

A dust catcher is a large vertical inertial separator used in blast-furnace gas cleaning to remove coarse particulate before downstream wet scrubbers or fabric filters.

Finned tubes carry helically-wound fins to multiply gas-side surface area in HRSGs. Harp tubes are the vertical bundle configuration. Fin geometry is particularly fouling-sensitive.

GAHs preheat combustion air with flue-gas heat (like an air heater). GGHs transfer heat between two flue-gas streams, typically reheating scrubbed gas before the stack.

An HRSG recovers heat from a gas turbine's exhaust to generate steam, the second cycle of a combined-cycle plant. Finned-tube ash deposition and ABS fouling are the main cleaning concerns.

Boilers use ID, FD and PA fans to move flue gas, combustion air and primary air. Fouling affects vibration, draft control, efficiency and availability.

A multi-cyclone is a bank of small cyclones in one housing. It is used as a rugged pre-cleaner but is sensitive to pluggage, flow imbalance and hopper bridging.

Stack breeching is the large flue-gas ductwork that connects boilers, air pollution control equipment, induced-draught fans and the stack.

Availability factor is the percentage of total hours that a plant is available to generate, whether or not it actually does. Distinguishes equipment readiness from market dispatch.

Capacity factor is actual energy output divided by theoretical maximum if a plant ran at full nameplate continuously. Combines availability with market dispatch.

Collection efficiency is the fraction of inlet particulate captured by an ESP, baghouse or cyclone. Reported as a percentage; modern ESPs achieve 99.5%+, baghouses 99.9%+.

Compressed air at 4-7 bar from plant or instrument-air systems drives industrial sonic horns. Consumption typically 8-14 Nm3/min during a firing burst.

CEMS instruments measure stack emissions in real time - opacity, PM, NOx, SOx, CO, O2, moisture - providing the data on which environmental compliance is judged.

Mass loading is particulate mass per gas volume. It drives ESP and baghouse sizing, hopper load, dust transport, cleaning demand and emissions margin.

MTBF is the average operating time between failures for repairable equipment. It supports availability, maintenance planning and cleaning-system comparisons.

NOx, SOx and CO are key regulated gaseous emissions from combustion plants. Cleaning affects them indirectly by preserving heat transfer and abatement performance.

Opacity is the percentage of light obscured by particulate in stack gas. It is monitored by transmissometer and often tracks ESP or baghouse upset.

Operating pressure is the air pressure available at a sonic horn during firing. It controls sound output, diaphragm life, pipe sizing and receiver design.

Particulate matter is airborne solid or liquid particulate. PM10, PM2.5 and PM1 describe aerodynamic particle size and influence health, monitoring and collection difficulty.

Removal efficiency is the fraction of a target pollutant removed across a control device. It is used for gases, particulate, odours and some hazardous compounds.

AISI 304 (18-8) stainless is the economy stainless option for non-chloride service. Used for sonic-horn external mountings and accessories where 316 would be overspecified.

AISI 316 / 316L molybdenum-bearing austenitic stainless steel is the workhorse material for industrial sonic-horn bells, diaphragms and mountings in moderate-temperature service.

DN (EN 1092 European) and ANSI B16.5 flanges are the dominant industrial mounting standards. Sonic horns typically come with DN50-DN200 or ANSI 2-8 inch 150 lb mounting flanges.

Hastelloy (C276, C22) is a family of nickel-molybdenum-chromium alloys with extreme corrosion resistance. Specified for sonic horns in severe chloride-bearing or acidic service.

High-alumina refractory bricks contain 60-95% Al2O3 and serve in the highest-temperature zones of cement kilns, lime kilns and metallurgical furnaces.

IP65 and IP66 are IEC ingress-protection ratings for dust-tight enclosures. They differ in water-jet severity and are common on outdoor sonic-horn accessories.

Inconel 625 and 718 are nickel-based superalloys used where stainless steel loses strength or corrosion margin in hot, chloride-rich or oxidising service.

NEMA enclosure ratings define protection for electrical enclosures in US practice. NEMA 4, 4X, 7, 9 and 12 often appear in sonic-horn accessories.

Refractory linings protect steel shells and process equipment from heat, abrasion, slag and chemical attack. Castables and bricks are selected for different service duties.

BLRBAC (Black Liquor Recovery Boiler Advisory Committee) publishes Recommended Good Practices governing safe operation of kraft recovery boilers. Mandatory reference for any cleaning-system change.

Black liquor is the concentrated spent cooking liquor from kraft pulping. It is burned in the recovery boiler to generate steam, power and to recover the pulping chemicals.

Carry-over is the entrained molten smelt droplets and ash particles carried upward in recovery-boiler flue gas. The dominant fouling agent on superheater and generating-bank tubes.

Chill-and-blow is the thermal-shock cleaning campaign on a recovery-boiler superheater. The boiler is rapidly cooled to crack deposits; intense sootblowing then dislodges them.

Fume is the fine sub-micron sodium-sulphate particulate that forms in the upper furnace of a recovery boiler. It deposits on superheater and economiser tubes and is captured by the ESP.

A kraft lime kiln calcines lime mud into burnt lime for recausticising. Fouling appears in chain sections, preheaters, ducts, ESPs and fine-lime hoppers.

A multi-effect evaporator concentrates weak kraft black liquor to high solids before recovery-boiler firing, using vapour from one effect to heat the next.

Recausticising converts green liquor and lime into white liquor for kraft pulping. It links the recovery boiler, smelt dissolving tank and lime kiln.

Smelt is the molten sodium salt mixture formed in a kraft recovery boiler. It drains to the dissolving tank and becomes green liquor.

A smelt dissolving tank receives molten recovery-boiler smelt and dissolves it in weak wash to make green liquor. Vent deposits and safety controls are important.

TRS is the combined concentration of reduced sulphur compounds such as hydrogen sulphide, methyl mercaptan, dimethyl sulphide and dimethyl disulphide.

A recovery boiler water wash is an offline high-pressure cleaning campaign used to remove deposits that online sootblowing and acoustic cleaning cannot control.

An AIG is the array of nozzles that distributes ammonia evenly into flue gas upstream of an SCR catalyst bed. Poor AIG performance is the leading cause of high ammonia slip.

Ammonia slip is unreacted ammonia leaving the DeNOx system in the flue gas. It is regulated, expensive in lost reagent, and causes ammonium-bisulphate fouling downstream.

Ammonium bisulphate is a sticky low-melting deposit formed when slipped ammonia reacts with SO3 in cooling flue gas. The dominant cold-end fouling species on SCR-equipped boilers.

An SCR catalyst module is a steel-framed cassette holding multiple catalyst elements. Modules are stacked into layers; layers are stacked into the SCR reactor.

Catalyst masking is the deposition of a thin ash layer on the SCR catalyst face that blocks ammonia and NOx from reaching the active sites. Distinct from pluggage and poisoning.

Catalyst pluggage is the physical blockage of SCR catalyst channels by large-particle ash, popcorn ash or ammonium-salt deposits. It causes delta P rise and gas-flow maldistribution.

Catalyst poisoning is the chemical binding of trace species (arsenic, alkali metals, phosphorus, sulphur) to SCR active sites. Usually irreversible - the catalyst layer must be replaced.

Regeneration removes accumulated masking and partial poisoning from used SCR catalyst, restoring activity to 90% of fresh and saving 60-70% of replacement cost.

A corrugated catalyst uses corrugated fibre-reinforced sheets coated with active material. Lighter than honeycomb, particularly common on tail-end SCR and marine duty.

DeNOx is the collective term for post-combustion NOx-reduction technologies. SCR and SNCR are the dominant options; both rely on reaction of NOx with ammonia or urea.

High-dust SCR sits upstream of ESP/baghouse at 300-400 deg C. Low-dust sits between ESP and air heater. Tail-end SCR sits downstream of all particulate control at lower temperature.

A honeycomb catalyst is an extruded ceramic SCR catalyst block with parallel square channels. It gives high surface area but needs careful ash, pitch and cleaning management.

Large-particle ash is coarse fly ash or slag debris that can wedge into SCR catalyst channels, raise pressure drop and reduce DeNOx performance.

NOx reduction efficiency is the percentage of inlet NOx removed by a DeNOx system. It depends on catalyst activity, mixing, temperature and cleanliness.

Plate catalyst uses coated metal plates with open gas channels. It is often selected for high-dust SCR service where pluggage risk matters.

Popcorn ash is porous low-density fly ash, often from incomplete coal combustion. It can lodge in SCR catalyst channels and increase pressure drop.

SCR catalysts can oxidise part of flue-gas SO2 to SO3, increasing sulphuric acid mist, ammonium bisulphate fouling and cold-end corrosion risk.

SCR reduces NOx by injecting ammonia upstream of a catalyst. Temperature, mixing, catalyst condition and ash control determine performance.

SNCR injects ammonia or urea into a furnace temperature window to reduce NOx without catalyst. It is simpler than SCR but usually less efficient.

Urea and aqueous ammonia are the main SNCR reagents for NOx reduction, with different handling, injection, by-product and ammonia-slip implications.

ASME PTC 4 specifies the standard methodology for steam-generator performance tests. Used to quantify boiler efficiency, heat losses and heat-rate impact of fouling.

The ATEX directive sets EU requirements for equipment used in explosive atmospheres. Categorises zones 0/1/2 (gas) and 20/21/22 (dust); industrial sonic horns are routinely certified for Zone 20/21/22 dust service.

BREF documents describe Best Available Techniques (BAT) for industrial sectors under the EU IED. BAT-AELs are the associated emission-limit ranges that Member State permits must respect.

The 13. BImSchV regulates large combustion plant emissions in Germany; the 17. BImSchV regulates waste-incineration plants. Both implement the EU IED into German law.

CE marking declares an industrial product's compliance with applicable EU directives. Sonic horns sold into the EU carry CE marking covering ATEX, EMC, Machinery and Pressure Equipment directives as applicable.

NEC Class I Div 1 and Div 2 are the US National Electrical Code's hazardous-area classifications for equipment exposed to flammable gases or vapours.

EN 14181 sets European quality-assurance levels for stationary-source CEMS. EN 13284 covers manual reference methods for low-range particulate determination.

EPA NSPS set emission limits for newly constructed and significantly modified industrial sources. Subpart D / Da / Db cover steam-generating units; many other subparts cover other sectors.

EU Directive 2003/10/EC sets noise-exposure limits for EU workplaces. Lower action 80 dBA, upper action 85 dBA, exposure limit 87 dBA, all daily averages.

The EU Emissions Trading System sets a price on CO2 emissions from large industrial installations. Covers power, cement, refining and municipal waste incineration monitoring.

IEC 60079 is the IEC standard series for explosive atmospheres. It defines equipment, installation, inspection and protection concepts used by ATEX and IECEx.

IECEx is the IEC certification system for equipment used in explosive atmospheres. It uses IEC 60079 standards and is widely used for global hazardous-area procurement.

ISO 1996 describes methods for environmental noise measurement and assessment. It is relevant to site-boundary assessment of industrial sonic-horn installations.

ISO 9614 describes sound-power determination using sound-intensity measurements. It helps compare total acoustic output rather than one-point SPL.

The IED is the EU framework for integrated industrial pollution control. It links permits to BAT conclusions, emission limits, monitoring and inspection duties.

MATS sets US limits for mercury and hazardous air pollutants from coal- and oil-fired power plants, driving particulate, sorbent and monitoring upgrades.

MoEFCC and CPCB emission norms set Indian limits for particulate matter, SO2, NOx and mercury across thermal power and other industrial sectors.

OSHA 29 CFR 1910.95 sets US occupational noise exposure rules. The action level is 85 dBA TWA and the permissible exposure limit is 90 dBA TWA.

TA Luft 2021 is Germany's technical instruction for air pollution control from industrial installations, setting emission and permitting expectations.

UKCA marking is the UK product conformity marking used for goods placed on the market in Great Britain, relevant to machinery, electrical and hazardous-area equipment.

A BOF blows pure oxygen onto molten pig iron to refine it into steel. Off-gas dust collection is high-temperature, intermittent and demanding.

Blast-furnace top gas is cleaned in a multi-stage train: dust catcher, Venturi scrubber, wet ESP. Bridging in dust-catcher hoppers is a recurring operational issue.

A Claus / SRU unit recovers elemental sulphur from H2S-bearing refinery acid gas through partial combustion and catalytic conversion. WHB economiser fouling is the principal cleaning issue.

A coke oven battery destructively distils coking coal into metallurgical coke for the blast furnace. Coke-side and pushing emissions are tightly regulated and require dust collection.

DRI reduces iron-ore pellets to metallic iron in solid state using gas or coal. Hopper bridging in DRI dust handling is a recurring operational issue.

An EAF melts steel scrap and DRI in a refractory-lined vessel using an electric arc. Dust collection is via a roof-evacuation duct to a large baghouse, prone to compartment fouling.

The FCC regenerator burns coke deposits off spent cracking catalyst, restoring activity and producing high-temperature flue gas for downstream energy recovery.

Fluid catalytic cracking (FCC) cracks heavy hydrocarbons into gasoline and lighter products over a fluidised catalyst bed. The associated regenerator and separators benefit from sonic-horn cleaning.

A pelletising kiln hardens green iron-ore pellets into furnace-ready pellets. Dust, alkali salts and fine ore carryover make off-gas cleaning important.

A reformer furnace reacts hydrocarbon feed with steam over catalyst to make hydrogen-rich syngas. Convection-section fouling and ammonium salts can affect heat recovery.

A sinter plant agglomerates iron-ore fines, coke breeze and flux into porous sinter for blast furnaces. Off-gas dust and deposits are major control duties.

A third-stage separator is a high-efficiency cyclone system downstream of FCC regenerator cyclones, protecting expanders and downstream equipment from catalyst fines.

APC residue is the fine fly-ash plus reagent salts captured by the WtE flue-gas treatment train. Classified as hazardous waste; requires specialised disposal.

Alkali 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.

Bagasse is the fibrous residue left after juice extraction from sugarcane. Burned in cogeneration boilers at sugar mills; silica-rich ash deposits aggressively.

Chloride-induced corrosion is the accelerated tube-wall thinning caused by chlorine-rich deposits on WtE and biomass boilers. The dominant tube-failure mechanism in WtE.

Grate-fired (mass-burn) WtE boilers burn MSW on a moving grate without fuel pre-processing. The dominant design for municipal waste incineration.

Hog fuel is the coarse, mixed wood-residue stream - bark, chips, sawdust, screenings - burned in pulp-mill bark boilers and biomass side boilers.

Incinerator bottom ash is the coarse mineral residue discharged from WtE grates. It is processed for metal recovery, ageing, aggregate reuse or landfill.

Low-melt sticky ash forms when alkali-rich ash softens and bonds to cooler tube surfaces. It drives fouling, corrosion and online-cleaning requirements.

Municipal solid waste is mixed residual waste used as fuel in mass-burn WtE plants. Its variable plastics, food, moisture and inerts drive fouling behaviour.

Straw and agricultural residues are biomass fuels with high alkali, chlorine and ash variability, creating slagging, fouling and corrosion challenges.

A tipping fee is the charge paid to a waste facility for accepting material, shaping the economics and availability pressure of waste-to-energy plants.

Waste-to-energy plants burn municipal or prepared waste to generate heat and power, with variable fuel chemistry driving fouling, corrosion and cleaning demand.

Wood pellets are densified biomass fuel used in co-firing and dedicated biomass boilers, with storage, dust, self-heating and ash-fouling implications.