[{"data":1,"prerenderedAt":714},["ShallowReactive",2],{"site-footer-common":3,"glossary:large-particle-ash":45,"glossary-related:large-particle-ash":186},{"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":165,"description":166,"extension":167,"meta":168,"navigation":169,"path":170,"relatedTerms":171,"seo":176,"sources":179,"stem":183,"term":184,"__hash__":185},"glossary\u002Fglossary\u002Flarge-particle-ash.md","Large-particle ash (LPA)",[49,50],"LPA","large particle ash",{"type":52,"value":53,"toc":158},"minimark",[54,72,77,85,89,130,134],[55,56,57,60,61,66,67,71],"p",{},[58,59,47],"strong",{}," is fly ash significantly larger than typical particulate (above ~1 mm and sometimes up to 25 mm), produced by fragmentation of waterwall and superheater slag, agglomeration of finer ash, or thermal break-up of refractory. LPA is the dominant cause of ",[62,63,65],"a",{"href":64},"\u002Fglossary\u002Fselective-catalytic-reduction","SCR catalyst"," channel ",[62,68,70],{"href":69},"\u002Fglossary\u002Fcatalyst-pluggage","pluggage"," on coal-fired utility boilers.",[73,74,76],"h2",{"id":75},"why-lpa-causes-pluggage","Why LPA causes pluggage",[55,78,79,80,84],{},"Normal fly-ash particles are smaller than typical honeycomb ",[62,81,83],{"href":82},"\u002Fglossary\u002Fhoneycomb-catalyst","catalyst pitch"," (3.5–7.4 mm) and pass through. LPA particles match or exceed the pitch dimension, wedge into a channel mouth, and progressively block the cell. A single LPA particle can block one channel; clusters of LPA across the top of the catalyst face can block tens of percent of the open area.",[73,86,88],{"id":87},"mitigation","Mitigation",[90,91,92,104,110,116],"ul",{},[93,94,95,98,99,103],"li",{},[58,96,97],{},"LPA screens"," — coarse mesh installed upstream of the catalyst, ahead of the ",[62,100,102],{"href":101},"\u002Fglossary\u002Fammonia-injection-grid","AIG"," or just below it, trapping particles above a set size",[93,105,106,109],{},[58,107,108],{},"Pop-up grids"," in the economiser hopper trap LPA before it reaches the SCR inlet",[93,111,112,115],{},[58,113,114],{},"Larger-pitch top guard layer"," — first catalyst layer with wider channels admits LPA which then drops through to a screen below",[93,117,118,129],{},[58,119,120,124,125],{},[62,121,123],{"href":122},"\u002Fglossary\u002Fsonic-horn","Sonic horns"," and ",[62,126,128],{"href":127},"\u002Fglossary\u002Fsonic-sootblower","sootblowers"," — dislodge accumulating LPA-driven deposits between maintenance windows",[73,131,133],{"id":132},"related-terms","Related terms",[90,135,136,141,147,152],{},[93,137,138],{},[62,139,140],{"href":64},"Selective Catalytic Reduction (SCR)",[93,142,143],{},[62,144,146],{"href":145},"\u002Fglossary\u002Fpopcorn-ash","Popcorn ash",[93,148,149],{},[62,150,151],{"href":69},"Catalyst pluggage",[93,153,154],{},[62,155,157],{"href":156},"\u002Fglossary\u002Feconomiser","Economiser",{"title":159,"searchDepth":160,"depth":160,"links":161},"",2,[162,163,164],{"id":75,"depth":160,"text":76},{"id":87,"depth":160,"text":88},{"id":132,"depth":160,"text":133},"scr-sncr","Large-particle ash (LPA) is fly ash significantly larger than typical particulate (above ~1 mm and sometimes up to 25 mm), produced by fragmentation of waterwall and superheater slag, agglomeration of finer ash, or thermal break-up of refractory. LPA is the dominant cause of SCR catalyst channel pluggage on coal-fired utility boilers.","md",{},true,"\u002Fglossary\u002Flarge-particle-ash",[172,173,174,175],"selective-catalytic-reduction","popcorn-ash","catalyst-pluggage","economiser",{"title":177,"description":178},"Large-particle ash (LPA) — slag fragments that plug SCR catalysts","LPA is fly ash larger than typical (>1 mm), produced by slag fragmentation and agglomeration in the boiler. It is the leading cause of SCR catalyst channel pluggage.",[180],{"title":181,"url":182},"Airflow Sciences — SCR Catalyst Pluggage Reduction at Roxboro Unit 3","https:\u002F\u002Fwww.airflowsciences.com\u002Fsites\u002Fdefault\u002Ffiles\u002Fdocs\u002F2010_MEGA_Symposium_Roxboro_U3.pdf","glossary\u002Flarge-particle-ash","Large-particle ash","uw9Bv-6YGw7P6wmfT-xY2LbAuysdWQd6SbJ-YshGDYA",[187,348,440,580],{"id":188,"title":140,"aliases":189,"body":193,"category":165,"description":325,"extension":167,"meta":326,"navigation":169,"path":64,"relatedTerms":327,"seo":335,"sources":338,"stem":345,"term":346,"__hash__":347},"glossary\u002Fglossary\u002Fselective-catalytic-reduction.md",[190,191,192],"SCR","SCR system","SCR reactor",{"type":52,"value":194,"toc":320},[195,213,217,232,236,239,265,281,283],[55,196,197,199,200,204,205,124,209,212],{},[58,198,140],{}," is the dominant flue-gas NOx-control technology on coal-fired and gas-fired utility boilers, ",[62,201,203],{"href":202},"\u002Fglossary\u002Fheat-recovery-steam-generator","HRSGs"," in combined-cycle plants, ",[62,206,208],{"href":207},"\u002Fglossary\u002Fwaste-to-energy","waste-to-energy",[62,210,211],{"href":207},"biomass"," boilers, cement plants and major refining furnaces. Ammonia or aqueous urea is injected upstream of a catalyst bed; the catalyst lowers the activation energy for the reaction NOx + NH₃ → N₂ + H₂O, achieving 80–95% NOx reduction across the reactor.",[73,214,216],{"id":215},"reactor-layout","Reactor layout",[55,218,219,220,223,224,227,228,231],{},"A typical SCR reactor is a vertical or horizontal duct containing 2–4 layers of catalyst modules. Upstream of the catalyst sits the ",[62,221,222],{"href":101},"ammonia injection grid (AIG)"," that distributes the ammonia evenly into the flue gas. Most installations operate in the ",[58,225,226],{},"high-dust"," position (between economiser and air heater) where catalyst temperature is around 300–400 °C; ",[58,229,230],{},"tail-end"," SCRs sit downstream of particulate control at lower temperatures, with the trade-off of needing flue-gas reheating.",[73,233,235],{"id":234},"fouling-and-cleaning","Fouling and cleaning",[55,237,238],{},"SCR catalysts foul in two ways:",[90,240,241,256],{},[93,242,243,248,249,124,252,255],{},[58,244,245],{},[62,246,247],{"href":69},"Pluggage"," — fly ash, ",[62,250,251],{"href":145},"popcorn ash",[62,253,254],{"href":170},"large-particle ash"," wedge into the catalyst cells, blocking the gas path",[93,257,258,264],{},[58,259,260],{},[62,261,263],{"href":262},"\u002Fglossary\u002Fcatalyst-masking","Masking"," — a thin layer of deposit covers the active sites; gas flow continues but catalytic activity falls",[55,266,267,268,272,273,276,277,280],{},"Both reduce NOx-reduction efficiency, raise ",[62,269,271],{"href":270},"\u002Fglossary\u002Fammonia-slip","ammonia slip",", and shorten catalyst life. Cleaning options include steam ",[62,274,128],{"href":275},"\u002Fglossary\u002Fsteam-sootblower",", ",[62,278,279],{"href":122},"sonic horns"," and offline campaigns (vacuum \u002F water wash \u002F regeneration). Sonic horns are increasingly favoured because they continuously dislodge ash before it cements onto the catalyst face, without the steam erosion of mechanical sootblowing.",[73,282,133],{"id":132},[90,284,285,291,296,301,306,310,315],{},[93,286,287],{},[62,288,290],{"href":289},"\u002Fglossary\u002Fselective-non-catalytic-reduction","Selective Non-Catalytic Reduction (SNCR)",[93,292,293],{},[62,294,295],{"href":101},"Ammonia injection grid",[93,297,298],{},[62,299,300],{"href":270},"Ammonia slip",[93,302,303],{},[62,304,305],{"href":262},"Catalyst masking",[93,307,308],{},[62,309,151],{"href":69},[93,311,312],{},[62,313,314],{"href":82},"Honeycomb catalyst",[93,316,317],{},[62,318,319],{"href":122},"Sonic horn",{"title":159,"searchDepth":160,"depth":160,"links":321},[322,323,324],{"id":215,"depth":160,"text":216},{"id":234,"depth":160,"text":235},{"id":132,"depth":160,"text":133},"Selective Catalytic Reduction (SCR) is the dominant flue-gas NOx-control technology on coal-fired and gas-fired utility boilers, HRSGs in combined-cycle plants, waste-to-energy and biomass boilers, cement plants and major refining furnaces. Ammonia or aqueous urea is injected upstream of a catalyst bed; the catalyst lowers the activation energy for the reaction NOx + NH₃ → N₂ + H₂O, achieving 80–95% NOx reduction across the reactor.",{},[328,329,330,331,332,174,333,334],"selective-non-catalytic-reduction","denox","ammonia-injection-grid","ammonia-slip","catalyst-masking","honeycomb-catalyst","sonic-horn",{"title":336,"description":337},"Selective Catalytic Reduction (SCR) — how the dominant NOx-control technology works","SCR is the dominant NOx-control technology on industrial combustion plant. Ammonia is injected upstream of a catalyst that converts NOx to nitrogen and water.",[339,342],{"title":340,"url":341},"Wikipedia — Selective catalytic reduction","https:\u002F\u002Fen.wikipedia.org\u002Fwiki\u002FSelective_catalytic_reduction",{"title":343,"url":344},"Power Engineering — SCR Catalyst Cleaning: Sootblowers vs. Acoustic Horns","https:\u002F\u002Fwww.power-eng.com\u002Foperations-maintenance\u002Fscr-catalyst-cleaningsootblowers-vs-acoustic-horns\u002F","glossary\u002Fselective-catalytic-reduction","Selective Catalytic Reduction","fmMCMd4NY3eZdSk_UYlbZ9ryi-9CR2Os6DivQjXEPCU",{"id":349,"title":146,"aliases":350,"body":353,"category":165,"description":429,"extension":167,"meta":430,"navigation":169,"path":145,"relatedTerms":431,"seo":433,"sources":436,"stem":438,"term":146,"__hash__":439},"glossary\u002Fglossary\u002Fpopcorn-ash.md",[351,352],"popcorn fly ash","low-density ash",{"type":52,"value":354,"toc":424},[355,367,371,381,383,408,410],[55,356,357,359,360,363,364,366],{},[58,358,146],{}," is a category of ",[62,361,362],{"href":170},"large-particle ash (LPA)"," consisting of porous, low-density particles 5–25 mm in size that resemble a kernel of popped corn. The particles form during incomplete coal combustion or low-temperature slagging, particularly on sub-bituminous coal and on units operating at reduced load. The low density means the particles are easily carried by flue gas into the ",[62,365,190],{"href":64},".",[73,368,370],{"id":369},"why-popcorn-ash-matters","Why popcorn ash matters",[55,372,373,374,377,378,380],{},"Once a popcorn-ash particle enters a ",[62,375,376],{"href":82},"honeycomb catalyst"," channel, the channel is essentially blocked: the particle is too soft to break up under gas flow, too large to pass through, and too irregular to dislodge with typical ",[62,379,334],{"href":122}," energy. The result is a long-lived dead channel that reduces SCR efficiency.",[73,382,88],{"id":87},[90,384,385,391,397,402],{},[93,386,387,390],{},[58,388,389],{},"Coal blending or fuel switching"," to reduce popcorn-ash formation",[93,392,393,396],{},[58,394,395],{},"Combustion-tuning"," to raise furnace temperature and reduce porous-ash output",[93,398,399,401],{},[58,400,97],{}," upstream of the catalyst",[93,403,404,407],{},[58,405,406],{},"Guard layers"," as first catalyst layer",[73,409,133],{"id":132},[90,411,412,416,420],{},[93,413,414],{},[62,415,184],{"href":170},[93,417,418],{},[62,419,151],{"href":69},[93,421,422],{},[62,423,140],{"href":64},{"title":159,"searchDepth":160,"depth":160,"links":425},[426,427,428],{"id":369,"depth":160,"text":370},{"id":87,"depth":160,"text":88},{"id":132,"depth":160,"text":133},"Popcorn ash is a category of large-particle ash (LPA) consisting of porous, low-density particles 5–25 mm in size that resemble a kernel of popped corn. The particles form during incomplete coal combustion or low-temperature slagging, particularly on sub-bituminous coal and on units operating at reduced load. The low density means the particles are easily carried by flue gas into the SCR.",{},[432,174,172],"large-particle-ash",{"title":434,"description":435},"Popcorn ash — porous low-density particles that wedge into SCR cells","Popcorn ash is porous low-density fly-ash particles, typically 5–25 mm, formed during incomplete coal combustion. They wedge into SCR catalyst channels and resist cleaning.",[437],{"title":181,"url":182},"glossary\u002Fpopcorn-ash","ONIVUaDgbJ8YiIrW43GfjUbT3mh72uc3hfKFshfWiqg",{"id":441,"title":151,"aliases":442,"body":446,"category":165,"description":570,"extension":167,"meta":571,"navigation":169,"path":69,"relatedTerms":572,"seo":573,"sources":576,"stem":578,"term":151,"__hash__":579},"glossary\u002Fglossary\u002Fcatalyst-pluggage.md",[443,444,445],"catalyst plugging","catalyst channelling","SCR catalyst pluggage",{"type":52,"value":447,"toc":565},[448,460,464,497,501,537,539],[55,449,450,452,453,455,456,459],{},[58,451,151],{}," is the physical blockage of ",[62,454,65],{"href":64}," channels by particulate material. Unlike ",[62,457,458],{"href":262},"catalyst masking"," (a thin surface blanket), pluggage fills the catalyst channels themselves, stopping gas flow through affected cells. The result is ΔP rise across the SCR, gas-flow maldistribution into the remaining open cells, and channelling effects that reduce overall NOx reduction.",[73,461,463],{"id":462},"sources-of-pluggage-material","Sources of pluggage material",[90,465,466,473,480,491],{},[93,467,468,472],{},[58,469,470],{},[62,471,47],{"href":170}," — slag fragments and agglomerated ash carried over from the boiler",[93,474,475,479],{},[58,476,477],{},[62,478,146],{"href":145}," — porous low-density ash particles that wedge into honeycomb cells",[93,481,482,485,486,490],{},[58,483,484],{},"Ammonium-salt deposits"," — ",[62,487,489],{"href":488},"\u002Fglossary\u002Fammonium-bisulphate","ammonium bisulphate"," on tail-end SCRs at lower temperatures",[93,492,493,496],{},[58,494,495],{},"Refractory debris"," — fragments from upstream furnace or duct repairs",[73,498,500],{"id":499},"prevention","Prevention",[90,502,503,508,513,519,528],{},[93,504,505,507],{},[58,506,97],{}," — coarse mesh screens upstream of the catalyst trap large particles",[93,509,510,512],{},[58,511,406],{}," — sacrificial top catalyst layer with larger pitch absorbs the initial particulate",[93,514,515,518],{},[58,516,517],{},"Larger pitch on the top layer"," — wider cell openings on the first catalyst layer pass LPA through to a removable screen below",[93,520,521,527],{},[58,522,523,524,526],{},"Periodic ",[62,525,334],{"href":122}," cleaning"," — dislodges accumulating ash before it cements",[93,529,530,536],{},[58,531,532,533],{},"Steam ",[62,534,535],{"href":127},"sootblowing"," — for harder deposits",[73,538,133],{"id":132},[90,540,541,545,549,553,557,561],{},[93,542,543],{},[62,544,140],{"href":64},[93,546,547],{},[62,548,184],{"href":170},[93,550,551],{},[62,552,146],{"href":145},[93,554,555],{},[62,556,305],{"href":262},[93,558,559],{},[62,560,314],{"href":82},[93,562,563],{},[62,564,319],{"href":122},{"title":159,"searchDepth":160,"depth":160,"links":566},[567,568,569],{"id":462,"depth":160,"text":463},{"id":499,"depth":160,"text":500},{"id":132,"depth":160,"text":133},"Catalyst pluggage is the physical blockage of SCR catalyst channels by particulate material. Unlike catalyst masking (a thin surface blanket), pluggage fills the catalyst channels themselves, stopping gas flow through affected cells. The result is ΔP rise across the SCR, gas-flow maldistribution into the remaining open cells, and channelling effects that reduce overall NOx reduction.",{},[172,432,173,332,333,334],{"title":574,"description":575},"Catalyst pluggage — channel blockage that reduces SCR gas flow","Catalyst pluggage is the physical blockage of SCR catalyst channels by large-particle ash, popcorn ash or ammonium-salt deposits. It causes ΔP rise and gas-flow maldistribution.",[577],{"title":181,"url":182},"glossary\u002Fcatalyst-pluggage","m2viiLe19KKcTBiDWhyUc38xPIzoOiMpL15r0i_ayHg",{"id":581,"title":157,"aliases":582,"body":585,"category":698,"description":699,"extension":167,"meta":700,"navigation":169,"path":156,"relatedTerms":701,"seo":705,"sources":708,"stem":712,"term":157,"__hash__":713},"glossary\u002Fglossary\u002Feconomiser.md",[583,584],"economizer","feedwater economiser",{"type":52,"value":586,"toc":692},[587,612,616,619,634,637,641,646,650,658,660],[55,588,589,590,592,593,597,598,602,603,607,608,366],{},"An ",[58,591,175],{}," is the tube bank in a boiler's ",[62,594,596],{"href":595},"\u002Fglossary\u002Fconvective-pass-backpass","convective pass"," that recovers residual heat from the flue gas by preheating boiler feedwater. It sits downstream of the ",[62,599,601],{"href":600},"\u002Fglossary\u002Freheater","reheater"," and upstream of the ",[62,604,606],{"href":605},"\u002Fglossary\u002Fair-heater","air heater","; economiser performance directly affects boiler ",[62,609,611],{"href":610},"\u002Fglossary\u002Fheat-rate","heat rate",[73,613,615],{"id":614},"fouling","Fouling",[55,617,618],{},"Two failure modes dominate:",[90,620,621,627],{},[93,622,623,626],{},[58,624,625],{},"Ash bridging"," between tubes — gas can no longer pass freely; ΔP across the economiser rises",[93,628,629,633],{},[58,630,631],{},[62,632,184],{"href":170}," dropping out of the gas stream onto economiser hoppers — bridges and pluggage in the hopper itself",[55,635,636],{},"The first reduces gas-side heat transfer and forces gas channelling around the blocked area; the second causes hopper extraction to fail and back-pressures the gas path.",[73,638,640],{"id":639},"sonic-horn-duty","Sonic-horn duty",[55,642,643,645],{},[62,644,123],{"href":122}," mounted on the economiser shell and hopper are particularly effective because economiser deposits are dry, friable and respond well to acoustic dislodging. Plants commonly report 1–2% boiler-efficiency recovery after horn installation on heavily-fouled economisers.",[73,647,649],{"id":648},"economiser-scr-adjacency","Economiser-SCR adjacency",[55,651,652,653,657],{},"On units with an upstream ",[62,654,656],{"href":655},"\u002Fglossary\u002Fhigh-dust-low-dust-tail-end-scr","high-dust SCR",", the economiser receives the same large-particle ash that the SCR is designed against. LPA screens between SCR and economiser are common; sonic horns help keep both surfaces clean.",[73,659,133],{"id":132},[90,661,662,668,673,679,684,688],{},[93,663,664],{},[62,665,667],{"href":666},"\u002Fglossary\u002Fboiler","Boiler",[93,669,670],{},[62,671,672],{"href":595},"Convective pass \u002F backpass",[93,674,675],{},[62,676,678],{"href":677},"\u002Fglossary\u002Fsuperheater","Superheater",[93,680,681],{},[62,682,683],{"href":605},"Air heater",[93,685,686],{},[62,687,184],{"href":170},[93,689,690],{},[62,691,319],{"href":122},{"title":159,"searchDepth":160,"depth":160,"links":693},[694,695,696,697],{"id":614,"depth":160,"text":615},{"id":639,"depth":160,"text":640},{"id":648,"depth":160,"text":649},{"id":132,"depth":160,"text":133},"boiler","An economiser is the tube bank in a boiler's convective pass that recovers residual heat from the flue gas by preheating boiler feedwater. It sits downstream of the reheater and upstream of the air heater; economiser performance directly affects boiler heat rate.",{},[698,702,703,704,432,334],"convective-pass-backpass","superheater","air-heater",{"title":706,"description":707},"Economiser — final tube bank that preheats feedwater with flue-gas heat","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.",[709],{"title":710,"url":711},"Wikipedia — Economizer","https:\u002F\u002Fen.wikipedia.org\u002Fwiki\u002FEconomizer","glossary\u002Feconomiser","kh4Q3Eo9CNl35_b843VUXSI8fDZuiLZqLyB__NSzVH4",1782613751274]