[{"data":1,"prerenderedAt":727},["ShallowReactive",2],{"site-footer-common":3,"glossary:corona-discharge":45,"glossary-related:corona-discharge":181},{"id":4,"extension":5,"footer":6,"meta":40,"navbar":41,"stem":43,"__hash__":44},"common\u002Fcommon.yml","yml",{"tagline":7,"links":8,"sections":9},"Acoustic cleaning intelligence for industrial fouling, soot, ash, dust and build-up.",[],[10,19,31],{"title":11,"links":12},"Product",[13,16],{"label":14,"to":15},"How it works","\u002F#product",{"label":17,"to":18},"Cost assessment","\u002F#hero",{"title":20,"links":21},"Company",[22,25,28],{"label":23,"to":24},"What we build","\u002F#about",{"label":26,"to":27},"Careers","\u002F#careers",{"label":29,"to":30},"Contact","\u002F#contact",{"title":32,"links":33},"Resources",[34,37],{"label":35,"to":36},"Blog","\u002Fresources\u002Fblog",{"label":38,"to":39},"Glossary","\u002Fglossary",{},{"links":42},[],"common","YocmZRy1AYfBbpgGVms-zhdiABlF8VTxHx6h4rDmZBA",{"id":46,"title":47,"aliases":48,"body":51,"category":163,"description":164,"extension":165,"meta":166,"navigation":167,"path":168,"relatedTerms":169,"seo":172,"sources":175,"stem":179,"term":47,"__hash__":180},"glossary\u002Fglossary\u002Fcorona-discharge.md","Corona discharge",[49,50],"corona (electrical)","negative corona",{"type":52,"value":53,"toc":156},"minimark",[54,79,84,87,91,127,130,134],[55,56,57,58,62,63,68,69,73,74,78],"p",{},"A ",[59,60,61],"strong",{},"corona discharge"," is a self-sustaining electrical discharge that occurs when the field gradient around a sharp electrode exceeds the breakdown threshold of the surrounding gas. In an ",[64,65,67],"a",{"href":66},"\u002Fglossary\u002Felectrostatic-precipitator","ESP"," the corona forms around the ",[64,70,72],{"href":71},"\u002Fglossary\u002Fdischarge-electrode","discharge electrode",", ionises flue-gas molecules, and the resulting ions attach to dust particles. The charged particles then drift to the ",[64,75,77],{"href":76},"\u002Fglossary\u002Fcollecting-electrode","collecting electrodes"," under the electric field.",[80,81,83],"h2",{"id":82},"negative-corona-dominates","Negative corona dominates",[55,85,86],{},"Industrial ESPs almost always run on negative corona because it sustains a higher voltage before sparking — but it also produces some ozone, which is one of the reasons WESPs in confined ventilation paths sometimes use positive corona instead.",[80,88,90],{"id":89},"what-disrupts-the-corona","What disrupts the corona",[92,93,94,101,115,121],"ul",{},[95,96,97,100],"li",{},[59,98,99],{},"Excessive dust on the collecting plate"," — raises plate-face voltage, narrows the working gap",[95,102,103,110,111],{},[59,104,105,106],{},"High ash ",[64,107,109],{"href":108},"\u002Fglossary\u002Fresistivity","resistivity"," — traps charge in the dust layer, leading to ",[64,112,114],{"href":113},"\u002Fglossary\u002Fback-corona","back-corona",[95,116,117,120],{},[59,118,119],{},"Bent or broken discharge electrodes"," — local field collapse, sparking, eventual short",[95,122,123,126],{},[59,124,125],{},"Fouled discharge electrode tips"," — suppressed corona, reduced ion current",[55,128,129],{},"Acoustic cleaning addresses two of these (plate dust thickness and discharge-electrode fouling) without the broken-electrode risk of aggressive mechanical rapping.",[80,131,133],{"id":132},"related-terms","Related terms",[92,135,136,141,146,151],{},[95,137,138],{},[64,139,140],{"href":66},"Electrostatic precipitator",[95,142,143],{},[64,144,145],{"href":71},"Discharge electrode",[95,147,148],{},[64,149,150],{"href":113},"Back-corona",[95,152,153],{},[64,154,155],{"href":108},"Resistivity (fly-ash)",{"title":157,"searchDepth":158,"depth":158,"links":159},"",2,[160,161,162],{"id":82,"depth":158,"text":83},{"id":89,"depth":158,"text":90},{"id":132,"depth":158,"text":133},"esp","A corona discharge is a self-sustaining electrical discharge that occurs when the field gradient around a sharp electrode exceeds the breakdown threshold of the surrounding gas. In an ESP the corona forms around the discharge electrode, ionises flue-gas molecules, and the resulting ions attach to dust particles. The charged particles then drift to the collecting electrodes under the electric field.","md",{},true,"\u002Fglossary\u002Fcorona-discharge",[170,171,114,109],"electrostatic-precipitator","discharge-electrode",{"title":173,"description":174},"Corona discharge — the ionisation mechanism that powers an ESP","Corona discharge is the electrical breakdown around an ESP's discharge electrode that ionises gas molecules and charges dust particles for collection.",[176],{"title":177,"url":178},"Wikipedia — Corona discharge","https:\u002F\u002Fen.wikipedia.org\u002Fwiki\u002FCorona_discharge","glossary\u002Fcorona-discharge","dShpP0lym_kkFMbohrkUgv75_uA0O8qlKu9VJ1eimyA",[182,356,457,584],{"id":183,"title":184,"aliases":185,"body":188,"category":163,"description":332,"extension":165,"meta":333,"navigation":167,"path":66,"relatedTerms":334,"seo":341,"sources":344,"stem":354,"term":140,"__hash__":355},"glossary\u002Fglossary\u002Felectrostatic-precipitator.md","Electrostatic precipitator (ESP)",[67,186,187],"electrostatic precipitators","dry ESP",{"type":52,"value":189,"toc":326},[190,206,210,223,227,263,267,298,300],[55,191,192,193,196,197,201,202,205],{},"An ",[59,194,195],{},"electrostatic precipitator (ESP)"," is an air-pollution-control device that removes particulate matter from a flue-gas stream by electrostatically charging dust particles and collecting them on grounded plate electrodes. ESPs are the dominant particulate-control technology on coal-fired boilers, cement kilns, ",[64,198,200],{"href":199},"\u002Fglossary\u002Fwaste-to-energy","waste-to-energy"," plants, ",[64,203,204],{"href":199},"biomass"," plants, sinter strands and many other heavy-industry off-gas streams.",[80,207,209],{"id":208},"how-an-esp-works","How an ESP works",[55,211,212,213,215,216,219,220,222],{},"Flue gas flows horizontally between a parallel array of vertical ",[64,214,77],{"href":76}," (plates) and ",[64,217,218],{"href":71},"discharge electrodes"," (high-voltage wires or rigid spikes). A negative DC potential of 40–80 kV applied to the discharge electrodes generates a ",[64,221,61],{"href":168}," that ionises the gas. Charged dust particles drift to the collecting plates, accumulate as a dust layer, are rapped down into hoppers below and removed by ash-handling equipment.",[80,224,226],{"id":225},"where-sonic-horns-fit","Where sonic horns fit",[55,228,229,230,234,235,239,240,244,245,249,250,252,253,257,258,262],{},"ESPs accumulate dust faster than mechanical rapping can release it, and hoppers below ESP fields routinely ",[64,231,233],{"href":232},"\u002Fglossary\u002Fbridging","bridge"," and choke. ",[64,236,238],{"href":237},"\u002Fglossary\u002Fsonic-horn","Sonic horns"," installed on the ESP ",[64,241,243],{"href":242},"\u002Fglossary\u002Fesp-penthouse","penthouse"," and on hopper walls keep dust dislodged, supplement ",[64,246,248],{"href":247},"\u002Fglossary\u002Fesp-rapper","rappers",", prevent ",[64,251,114],{"href":113}," by limiting plate dust thickness, and eliminate hopper ",[64,254,256],{"href":255},"\u002Fglossary\u002Frat-holing","rat-holing"," without the structural fatigue of ",[64,259,261],{"href":260},"\u002Fglossary\u002Ftumbling-hammer-rapper","tumbling-hammer rappers",".",[80,264,266],{"id":265},"common-failure-modes","Common failure modes",[92,268,269,275,280,286,292],{},[95,270,271,274],{},[59,272,273],{},"High opacity \u002F particulate emissions"," from thick dust layers reducing collection efficiency",[95,276,277,279],{},[59,278,150],{}," in high-resistivity ash that reverses ionisation and collapses collection",[95,281,282,285],{},[59,283,284],{},"Re-entrainment"," as rapper puffs return dust to the gas stream",[95,287,288,291],{},[59,289,290],{},"Hopper bridging"," that stops ash extraction and triggers field shutdowns",[95,293,294,297],{},[59,295,296],{},"Discharge-electrode breakage"," from rapper fatigue or sparking",[80,299,133],{"id":132},[92,301,302,307,311,315,321],{},[95,303,304],{},[64,305,306],{"href":76},"Collecting electrode",[95,308,309],{},[64,310,145],{"href":71},[95,312,313],{},[64,314,150],{"href":113},[95,316,317],{},[64,318,320],{"href":319},"\u002Fglossary\u002Fesp-hopper","ESP hopper",[95,322,323],{},[64,324,325],{"href":237},"Sonic horn",{"title":157,"searchDepth":158,"depth":158,"links":327},[328,329,330,331],{"id":208,"depth":158,"text":209},{"id":225,"depth":158,"text":226},{"id":265,"depth":158,"text":266},{"id":132,"depth":158,"text":133},"An electrostatic precipitator (ESP) is an air-pollution-control device that removes particulate matter from a flue-gas stream by electrostatically charging dust particles and collecting them on grounded plate electrodes. ESPs are the dominant particulate-control technology on coal-fired boilers, cement kilns, waste-to-energy plants, biomass plants, sinter strands and many other heavy-industry off-gas streams.",{},[335,336,171,337,338,339,114,340],"wet-esp","collecting-electrode","corona-discharge","esp-hopper","esp-rapper","sonic-horn",{"title":342,"description":343},"Electrostatic precipitator (ESP) — how it works and how it fouls","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.",[345,348,351],{"title":346,"url":347},"Wikipedia — Electrostatic precipitator","https:\u002F\u002Fen.wikipedia.org\u002Fwiki\u002FElectrostatic_precipitator",{"title":349,"url":350},"EPA — Monitoring Knowledge Base: Electrostatic Precipitators","https:\u002F\u002Fwww.epa.gov\u002Fair-emissions-monitoring-knowledge-base\u002Fmonitoring-control-technique-electrostatic-precipitators",{"title":352,"url":353},"Babcock & Wilcox — Basics of ESP Operation","https:\u002F\u002Fwww.babcock.com\u002Fhome\u002Fabout\u002Fresources\u002Flearning-center\u002Fbasic-esp-operation","glossary\u002Felectrostatic-precipitator","hT_C4hmid3iZaYWhLpiSJ2tBfL0bSJ-uhzn7TY4Vtj4",{"id":357,"title":145,"aliases":358,"body":363,"category":163,"description":447,"extension":165,"meta":448,"navigation":167,"path":71,"relatedTerms":449,"seo":450,"sources":453,"stem":455,"term":145,"__hash__":456},"glossary\u002Fglossary\u002Fdischarge-electrode.md",[359,360,361,362],"emitting electrode","corona electrode","discharge wire","rigid discharge electrode",{"type":52,"value":364,"toc":442},[365,383,387,390,408,412,418,420],[55,366,367,368,370,371,373,374,377,378,380,381,262],{},"The ",[59,369,72],{}," (also called the ",[59,372,359],{},") is the high-voltage element inside an ",[64,375,376],{"href":66},"electrostatic precipitator"," that generates the ",[64,379,61],{"href":168},". It is energised at 40–80 kV DC negative relative to the grounded ",[64,382,77],{"href":76},[80,384,386],{"id":385},"geometry","Geometry",[55,388,389],{},"Two families dominate:",[92,391,392,402],{},[95,393,394,397,398,401],{},[59,395,396],{},"Wire electrodes"," — fine spiral or barbed wires, typically weighted at the bottom and suspended from a top frame. Lightweight; easy to retrofit; prone to fatigue and breakage under ",[64,399,400],{"href":247},"rapping"," impacts.",[95,403,404,407],{},[59,405,406],{},"Rigid discharge electrodes (RDE)"," — pipe or mast sections with formed spikes or points. Used in modern American-style and rigid-frame ESPs. More robust against rapper breakage but heavier.",[80,409,411],{"id":410},"fouling-on-discharge-electrodes","Fouling on discharge electrodes",[55,413,414,415,417],{},"Just like the collecting plates, discharge electrodes accumulate dust. A thick coating on a wire or RDE reduces the local field gradient, suppresses corona, and lowers collection efficiency. The cleaning challenge is geometrically harder than for plates — discharge electrodes are point or line sources surrounded by gas. ",[64,416,238],{"href":237}," addressing the whole field volume help dislodge dust from discharge electrodes as well as from plates.",[80,419,133],{"id":132},[92,421,422,426,430,434,438],{},[95,423,424],{},[64,425,140],{"href":66},[95,427,428],{},[64,429,306],{"href":76},[95,431,432],{},[64,433,47],{"href":168},[95,435,436],{},[64,437,150],{"href":113},[95,439,440],{},[64,441,325],{"href":237},{"title":157,"searchDepth":158,"depth":158,"links":443},[444,445,446],{"id":385,"depth":158,"text":386},{"id":410,"depth":158,"text":411},{"id":132,"depth":158,"text":133},"The discharge electrode (also called the emitting electrode) is the high-voltage element inside an electrostatic precipitator that generates the corona discharge. It is energised at 40–80 kV DC negative relative to the grounded collecting electrodes.",{},[170,336,337,114,340],{"title":451,"description":452},"Discharge electrode — the high-voltage emitter inside an ESP","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.",[454],{"title":346,"url":347},"glossary\u002Fdischarge-electrode","E8VJGt3XxJD7K99lsPd9v-FQlmpjndXP4FYfB-pqPJk",{"id":458,"title":150,"aliases":459,"body":463,"category":163,"description":571,"extension":165,"meta":572,"navigation":167,"path":113,"relatedTerms":573,"seo":574,"sources":577,"stem":582,"term":150,"__hash__":583},"glossary\u002Fglossary\u002Fback-corona.md",[460,461,462],"reverse ionisation","back ionisation","back corona",{"type":52,"value":464,"toc":565},[465,480,484,490,511,515,531,535,541,543],[55,466,467,469,470,473,474,476,477,479],{},[59,468,150],{}," (also ",[471,472,460],"em",{},") is a destructive failure mode in an ",[64,475,376],{"href":66}," in which the dust layer on the ",[64,478,77],{"href":76}," accumulates so much charge that the gas trapped within it breaks down and emits ions of the opposite polarity. These positive ions discharge incoming negatively-charged dust particles before they reach the plate, and collection efficiency collapses.",[80,481,483],{"id":482},"when-back-corona-occurs","When back-corona occurs",[55,485,486,487,489],{},"Back-corona is triggered by high-",[64,488,109],{"href":108}," ash — typically above ~10¹¹ Ω·cm — combined with a thick, undisturbed dust layer. The conditions are common on:",[92,491,492,495,505,508],{},[95,493,494],{},"Low-sulphur Western US coals and sub-bituminous lignite",[95,496,497,498,500,501,504],{},"Some ",[64,499,204],{"href":199}," and ",[64,502,503],{"href":199},"WtE"," ashes",[95,506,507],{},"ESPs that have slipped behind on rapper maintenance",[95,509,510],{},"Cement-kiln ESPs after fuel switches or raw-mill stoppages",[80,512,514],{"id":513},"symptoms","Symptoms",[92,516,517,522,525,528],{},[95,518,519,520],{},"Falling secondary voltage at the ",[64,521,72],{"href":71},[95,523,524],{},"Rising secondary current with falling efficiency (the classic back-corona signature)",[95,526,527],{},"Persistent stack opacity rise that does not respond to rapper intensification",[95,529,530],{},"Sparking and arcing in the ESP power supply",[80,532,534],{"id":533},"sonic-horns-and-back-corona","Sonic horns and back-corona",[55,536,537,538,540],{},"Because back-corona is fundamentally a dust-thickness problem, the strongest mitigation is to keep the plates thinner — continuously, not in periodic bursts. ",[64,539,238],{"href":237}," installed across the field deliver gentle, frequent dislodging that holds the plate dust layer below the critical thickness for back-corona, while reducing the re-entrainment penalty of aggressive rapping. Acoustic cleaning is therefore one of the most cost-effective retrofits on a back-corona-limited ESP.",[80,542,133],{"id":132},[92,544,545,549,553,557,561],{},[95,546,547],{},[64,548,140],{"href":66},[95,550,551],{},[64,552,155],{"href":108},[95,554,555],{},[64,556,47],{"href":168},[95,558,559],{},[64,560,306],{"href":76},[95,562,563],{},[64,564,325],{"href":237},{"title":157,"searchDepth":158,"depth":158,"links":566},[567,568,569,570],{"id":482,"depth":158,"text":483},{"id":513,"depth":158,"text":514},{"id":533,"depth":158,"text":534},{"id":132,"depth":158,"text":133},"Back-corona (also reverse ionisation) is a destructive failure mode in an electrostatic precipitator in which the dust layer on the collecting electrodes accumulates so much charge that the gas trapped within it breaks down and emits ions of the opposite polarity. These positive ions discharge incoming negatively-charged dust particles before they reach the plate, and collection efficiency collapses.",{},[170,109,337,336,340],{"title":575,"description":576},"Back-corona — what it is, why it kills ESP performance, and how sonic horns help","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.",[578,581],{"title":579,"url":580},"Power Engineering — Tuning in to Acoustic Cleaning","https:\u002F\u002Fwww.power-eng.com\u002Fcoal\u002Ftuning-in-to-acoustic-cleaning\u002F",{"title":349,"url":350},"glossary\u002Fback-corona","G6FyEgaY8SP8-TTBfd1_Oq0GIZQSeNR8jVcFF2LPxto",{"id":585,"title":155,"aliases":586,"body":590,"category":163,"description":717,"extension":165,"meta":718,"navigation":167,"path":108,"relatedTerms":719,"seo":720,"sources":723,"stem":725,"term":596,"__hash__":726},"glossary\u002Fglossary\u002Fresistivity.md",[587,588,589],"ash resistivity","fly ash resistivity","dust resistivity",{"type":52,"value":591,"toc":711},[592,606,610,662,666,680,684,691,693],[55,593,594,597,598,600,601,603,604,262],{},[59,595,596],{},"Fly-ash resistivity"," is the electrical resistance of the dust layer deposited on the ",[64,599,77],{"href":76}," of an ",[64,602,67],{"href":66},". It is the single most important fuel-dependent variable in ESP performance, because it controls whether the collected dust can discharge its acquired charge to ground or instead accumulates trapped charge that triggers ",[64,605,114],{"href":113},[80,607,609],{"id":608},"the-resistivity-window","The resistivity window",[611,612,613,626],"table",{},[614,615,616],"thead",{},[617,618,619,623],"tr",{},[620,621,622],"th",{},"Resistivity (Ω·cm)",[620,624,625],{},"ESP behaviour",[627,628,629,643,651],"tbody",{},[617,630,631,635],{},[632,633,634],"td",{},"Below 10⁸",[632,636,637,638,642],{},"Dust discharges too quickly; ",[64,639,641],{"href":640},"\u002Fglossary\u002Fre-entrainment","re-entrainment"," dominates",[617,644,645,648],{},[632,646,647],{},"10⁸–10¹¹",[632,649,650],{},"Ideal range; standard ESP operation",[617,652,653,656],{},[632,654,655],{},"Above 10¹¹",[632,657,658,659,661],{},"High risk of ",[64,660,114],{"href":113},"; collection efficiency collapses",[80,663,665],{"id":664},"what-raises-resistivity","What raises resistivity",[92,667,668,671,674,677],{},[95,669,670],{},"Low sulphur content in coal (less SO₃ to condition the ash)",[95,672,673],{},"Low gas temperature near the acid dew point",[95,675,676],{},"High-alkali biomass ash",[95,678,679],{},"Certain cement-kiln dust compositions",[80,681,683],{"id":682},"mitigation","Mitigation",[55,685,686,687,690],{},"The classic remedy is flue-gas conditioning — injecting SO₃ or ammonia ahead of the ESP to lower ash resistivity. A complementary remedy is to keep the plate dust layer thin enough that back-corona cannot establish, which is where ",[64,688,689],{"href":237},"sonic horns"," earn their keep on high-resistivity ESPs: continuous gentle dislodging prevents the critical thickness from developing.",[80,692,133],{"id":132},[92,694,695,699,703,707],{},[95,696,697],{},[64,698,140],{"href":66},[95,700,701],{},[64,702,150],{"href":113},[95,704,705],{},[64,706,47],{"href":168},[95,708,709],{},[64,710,325],{"href":237},{"title":157,"searchDepth":158,"depth":158,"links":712},[713,714,715,716],{"id":608,"depth":158,"text":609},{"id":664,"depth":158,"text":665},{"id":682,"depth":158,"text":683},{"id":132,"depth":158,"text":133},"Fly-ash resistivity is the electrical resistance of the dust layer deposited on the collecting electrodes of an ESP. It is the single most important fuel-dependent variable in ESP performance, because it controls whether the collected dust can discharge its acquired charge to ground or instead accumulates trapped charge that triggers back-corona.",{},[170,114,337,340],{"title":721,"description":722},"Fly-ash resistivity — why high-resistivity ash triggers ESP back-corona","Fly-ash resistivity is the electrical resistance of a deposited dust layer. Resistivity above ~10¹¹ Ω·cm triggers back-corona and degrades ESP performance.",[724],{"title":349,"url":350},"glossary\u002Fresistivity","J1-xKuznLqtCFjFw4yljyJW2c3Rl6O26UKlXuDzmDdo",1782613734969]