[{"data":1,"prerenderedAt":837},["ShallowReactive",2],{"site-footer-common":3,"glossary:nox-reduction-efficiency":45,"glossary-related:nox-reduction-efficiency":272},{"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":52,"category":252,"description":253,"extension":254,"meta":255,"navigation":256,"path":257,"relatedTerms":258,"seo":263,"sources":266,"stem":270,"term":47,"__hash__":271},"glossary\u002Fglossary\u002Fnox-reduction-efficiency.md","NOx reduction efficiency",[49,50,51],"DeNOx efficiency","SCR efficiency","NOx conversion",{"type":53,"value":54,"toc":244},"minimark",[55,78,83,152,156,203,207,219,223],[56,57,58,61,62,67,68,72,73,77],"p",{},[59,60,47],"strong",{}," is the percentage of NOx removed from the flue gas by a ",[63,64,66],"a",{"href":65},"\u002Fglossary\u002Fdenox","DeNOx"," system, calculated as (NOx_in − NOx_out) \u002F NOx_in. It is the headline KPI for any ",[63,69,71],{"href":70},"\u002Fglossary\u002Fselective-catalytic-reduction","SCR"," or ",[63,74,76],{"href":75},"\u002Fglossary\u002Fselective-non-catalytic-reduction","SNCR"," installation and the figure permit compliance is measured against.",[79,80,82],"h2",{"id":81},"typical-performance","Typical performance",[84,85,86,106],"table",{},[87,88,89],"thead",{},[90,91,92,96,99],"tr",{},[93,94,95],"th",{},"System",[93,97,98],{},"Reduction range",[93,100,101,102],{},"Typical ",[63,103,105],{"href":104},"\u002Fglossary\u002Fammonia-slip","ammonia slip",[107,108,109,121,132,142],"tbody",{},[90,110,111,115,118],{},[112,113,114],"td",{},"SCR (high-dust)",[112,116,117],{},"80–95%",[112,119,120],{},"2–5 ppm",[90,122,123,126,129],{},[112,124,125],{},"SCR (tail-end)",[112,127,128],{},"90–98%",[112,130,131],{},"1–3 ppm",[90,133,134,136,139],{},[112,135,76],{},[112,137,138],{},"30–60%",[112,140,141],{},"5–10 ppm",[90,143,144,147,150],{},[112,145,146],{},"Combined SNCR + SCR",[112,148,149],{},"up to 99%",[112,151,120],{},[79,153,155],{"id":154},"what-erodes-efficiency-over-time","What erodes efficiency over time",[157,158,159,169,178,187,197],"ul",{},[160,161,162,168],"li",{},[59,163,164],{},[63,165,167],{"href":166},"\u002Fglossary\u002Fcatalyst-masking","Catalyst masking"," — fine ash blanket reducing active surface area",[160,170,171,177],{},[59,172,173],{},[63,174,176],{"href":175},"\u002Fglossary\u002Fcatalyst-poisoning","Catalyst poisoning"," — chemical de-activation",[160,179,180,186],{},[59,181,182],{},[63,183,185],{"href":184},"\u002Fglossary\u002Fcatalyst-pluggage","Catalyst pluggage"," — channel blockage and gas channelling",[160,188,189,196],{},[59,190,191,195],{},[63,192,194],{"href":193},"\u002Fglossary\u002Fammonia-injection-grid","AIG"," distribution drift"," — uneven NH₃\u002FNOx mixing",[160,198,199,202],{},[59,200,201],{},"Operating outside the temperature window"," — too cool or too hot for the catalyst",[79,204,206],{"id":205},"how-cleaning-preserves-efficiency","How cleaning preserves efficiency",[56,208,209,213,214,218],{},[63,210,212],{"href":211},"\u002Fglossary\u002Fsonic-horn","Sonic horns"," and steam ",[63,215,217],{"href":216},"\u002Fglossary\u002Fsonic-sootblower","sootblowers"," attack masking and pluggage directly. A well-cleaned catalyst maintains 85–90% of its initial efficiency for 30,000 operating hours, against 60–70% for a poorly cleaned catalyst of the same age. The economic case for active cleaning is therefore measured in deferred catalyst replacement and avoided ammonia-over-injection cost.",[79,220,222],{"id":221},"related-terms","Related terms",[157,224,225,230,235,240],{},[160,226,227],{},[63,228,229],{"href":70},"Selective Catalytic Reduction (SCR)",[160,231,232],{},[63,233,234],{"href":75},"Selective Non-Catalytic Reduction (SNCR)",[160,236,237],{},[63,238,239],{"href":104},"Ammonia slip",[160,241,242],{},[63,243,167],{"href":166},{"title":245,"searchDepth":246,"depth":246,"links":247},"",2,[248,249,250,251],{"id":81,"depth":246,"text":82},{"id":154,"depth":246,"text":155},{"id":205,"depth":246,"text":206},{"id":221,"depth":246,"text":222},"scr-sncr","NOx reduction efficiency is the percentage of NOx removed from the flue gas by a DeNOx system, calculated as (NOx_in − NOx_out) \u002F NOx_in. It is the headline KPI for any SCR or SNCR installation and the figure permit compliance is measured against.","md",{},true,"\u002Fglossary\u002Fnox-reduction-efficiency",[259,260,261,262],"selective-catalytic-reduction","selective-non-catalytic-reduction","ammonia-slip","catalyst-masking",{"title":264,"description":265},"NOx reduction efficiency — the headline KPI for SCR and SNCR systems","NOx reduction efficiency is the percentage of inlet NOx removed by the DeNOx system. The headline KPI for SCR (80–95%) and SNCR (30–60%) operation.",[267],{"title":268,"url":269},"Power Engineering — Selective Catalytic Reduction: Operational Issues","https:\u002F\u002Fwww.power-eng.com\u002Fenvironmental-emissions\u002Fselective-catalytic-reduction-operational-issues-and-guidelines\u002F","glossary\u002Fnox-reduction-efficiency","Xfcyi2ujLtvybPvlNwYTJpUqlszO7aEsUUq3q0gVXkw",[273,428,554,684],{"id":274,"title":229,"aliases":275,"body":278,"category":252,"description":407,"extension":254,"meta":408,"navigation":256,"path":70,"relatedTerms":409,"seo":415,"sources":418,"stem":425,"term":426,"__hash__":427},"glossary\u002Fglossary\u002Fselective-catalytic-reduction.md",[71,276,277],"SCR system","SCR reactor",{"type":53,"value":279,"toc":402},[280,299,303,318,322,325,352,366,368],[56,281,282,284,285,289,290,294,295,298],{},[59,283,229],{}," is the dominant flue-gas NOx-control technology on coal-fired and gas-fired utility boilers, ",[63,286,288],{"href":287},"\u002Fglossary\u002Fheat-recovery-steam-generator","HRSGs"," in combined-cycle plants, ",[63,291,293],{"href":292},"\u002Fglossary\u002Fwaste-to-energy","waste-to-energy"," and ",[63,296,297],{"href":292},"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.",[79,300,302],{"id":301},"reactor-layout","Reactor layout",[56,304,305,306,309,310,313,314,317],{},"A typical SCR reactor is a vertical or horizontal duct containing 2–4 layers of catalyst modules. Upstream of the catalyst sits the ",[63,307,308],{"href":193},"ammonia injection grid (AIG)"," that distributes the ammonia evenly into the flue gas. Most installations operate in the ",[59,311,312],{},"high-dust"," position (between economiser and air heater) where catalyst temperature is around 300–400 °C; ",[59,315,316],{},"tail-end"," SCRs sit downstream of particulate control at lower temperatures, with the trade-off of needing flue-gas reheating.",[79,319,321],{"id":320},"fouling-and-cleaning","Fouling and cleaning",[56,323,324],{},"SCR catalysts foul in two ways:",[157,326,327,344],{},[160,328,329,334,335,294,339,343],{},[59,330,331],{},[63,332,333],{"href":184},"Pluggage"," — fly ash, ",[63,336,338],{"href":337},"\u002Fglossary\u002Fpopcorn-ash","popcorn ash",[63,340,342],{"href":341},"\u002Fglossary\u002Flarge-particle-ash","large-particle ash"," wedge into the catalyst cells, blocking the gas path",[160,345,346,351],{},[59,347,348],{},[63,349,350],{"href":166},"Masking"," — a thin layer of deposit covers the active sites; gas flow continues but catalytic activity falls",[56,353,354,355,357,358,361,362,365],{},"Both reduce NOx-reduction efficiency, raise ",[63,356,105],{"href":104},", and shorten catalyst life. Cleaning options include steam ",[63,359,217],{"href":360},"\u002Fglossary\u002Fsteam-sootblower",", ",[63,363,364],{"href":211},"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.",[79,367,222],{"id":221},[157,369,370,374,379,383,387,391,397],{},[160,371,372],{},[63,373,234],{"href":75},[160,375,376],{},[63,377,378],{"href":193},"Ammonia injection grid",[160,380,381],{},[63,382,239],{"href":104},[160,384,385],{},[63,386,167],{"href":166},[160,388,389],{},[63,390,185],{"href":184},[160,392,393],{},[63,394,396],{"href":395},"\u002Fglossary\u002Fhoneycomb-catalyst","Honeycomb catalyst",[160,398,399],{},[63,400,401],{"href":211},"Sonic horn",{"title":245,"searchDepth":246,"depth":246,"links":403},[404,405,406],{"id":301,"depth":246,"text":302},{"id":320,"depth":246,"text":321},{"id":221,"depth":246,"text":222},"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.",{},[260,410,411,261,262,412,413,414],"denox","ammonia-injection-grid","catalyst-pluggage","honeycomb-catalyst","sonic-horn",{"title":416,"description":417},"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.",[419,422],{"title":420,"url":421},"Wikipedia — Selective catalytic reduction","https:\u002F\u002Fen.wikipedia.org\u002Fwiki\u002FSelective_catalytic_reduction",{"title":423,"url":424},"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":429,"title":234,"aliases":430,"body":432,"category":252,"description":539,"extension":254,"meta":540,"navigation":256,"path":75,"relatedTerms":541,"seo":544,"sources":547,"stem":551,"term":552,"__hash__":553},"glossary\u002Fglossary\u002Fselective-non-catalytic-reduction.md",[76,431],"SNCR system",{"type":53,"value":433,"toc":534},[434,445,449,472,476,479,502,507,509],[56,435,436,438,439,441,442,444],{},[59,437,234],{}," reduces NOx in flue gas by injecting ammonia or aqueous urea directly into the furnace at high temperature (850–1100 °C), where the reagent reacts homogeneously with NOx without needing a catalyst. SNCR is cheaper to install than ",[63,440,71],{"href":70}," but achieves lower reduction (typically 30–60%) and produces higher ",[63,443,105],{"href":104},".",[79,446,448],{"id":447},"where-sncr-is-used","Where SNCR is used",[157,450,451,454,462,469],{},[160,452,453],{},"Smaller industrial and utility boilers where SCR capital cost is unjustified",[160,455,456,294,459,461],{},[63,457,458],{"href":292},"Waste-to-energy",[63,460,297],{"href":292}," plants — often as the primary DeNOx with optional SCR polish",[160,463,464,468],{},[63,465,467],{"href":466},"\u002Fglossary\u002Fpreheater-tower","Cement preheater towers"," where the gas temperature window is naturally available",[160,470,471],{},"As a retrofit on units where space prevents SCR installation",[79,473,475],{"id":474},"fouling-implications","Fouling implications",[56,477,478],{},"SNCR does not have a catalyst to foul, but the reagent injection itself creates downstream deposit risks:",[157,480,481,496],{},[160,482,483,486,487,491,492],{},[59,484,485],{},"Ammonia salt deposits"," — un-reacted ammonia combines with SO₃ and ash to form ",[63,488,490],{"href":489},"\u002Fglossary\u002Fammonium-bisulphate","ammonium bisulphate"," on cold-end heat-transfer surfaces, particularly the ",[63,493,495],{"href":494},"\u002Fglossary\u002Fair-heater","air heater",[160,497,498,501],{},[59,499,500],{},"Urea \u002F ammonia deposits on lance tips"," — injection lances can plug with urea solids or carbon deposits",[56,503,504,506],{},[63,505,212],{"href":211}," on the cold-end air heater address ABS fouling that follows SNCR operation.",[79,508,222],{"id":221},[157,510,511,515,519,525,529],{},[160,512,513],{},[63,514,229],{"href":70},[160,516,517],{},[63,518,66],{"href":65},[160,520,521],{},[63,522,524],{"href":523},"\u002Fglossary\u002Furea-sncr-aqueous-ammonia-sncr","Urea SNCR \u002F aqueous-ammonia SNCR",[160,526,527],{},[63,528,239],{"href":104},[160,530,531],{},[63,532,533],{"href":489},"Ammonium bisulphate",{"title":245,"searchDepth":246,"depth":246,"links":535},[536,537,538],{"id":447,"depth":246,"text":448},{"id":474,"depth":246,"text":475},{"id":221,"depth":246,"text":222},"Selective Non-Catalytic Reduction (SNCR) reduces NOx in flue gas by injecting ammonia or aqueous urea directly into the furnace at high temperature (850–1100 °C), where the reagent reacts homogeneously with NOx without needing a catalyst. SNCR is cheaper to install than SCR but achieves lower reduction (typically 30–60%) and produces higher ammonia slip.",{},[259,410,542,261,543],"urea-sncr-aqueous-ammonia-sncr","ammonium-bisulphate",{"title":545,"description":546},"Selective Non-Catalytic Reduction (SNCR) — DeNOx without a catalyst","SNCR injects ammonia or urea directly into the furnace at 850–1100 °C to reduce NOx without a catalyst. Cheaper than SCR but lower efficiency and higher slip.",[548],{"title":549,"url":550},"Wikipedia — Selective non-catalytic reduction","https:\u002F\u002Fen.wikipedia.org\u002Fwiki\u002FSelective_non-catalytic_reduction","glossary\u002Fselective-non-catalytic-reduction","Selective Non-Catalytic Reduction","IXdCJcIAQIaUzfIpBXuWLUA2b5T-pTWfhvZ703VsbdA",{"id":555,"title":239,"aliases":556,"body":559,"category":252,"description":674,"extension":254,"meta":675,"navigation":256,"path":104,"relatedTerms":676,"seo":677,"sources":680,"stem":682,"term":239,"__hash__":683},"glossary\u002Fglossary\u002Fammonia-slip.md",[557,558],"NH3 slip","ammonia breakthrough",{"type":53,"value":560,"toc":668},[561,571,575,612,616,631,635,644,646],[56,562,563,565,566,72,568,570],{},[59,564,239],{}," is the concentration of unreacted ammonia (NH₃) in the flue gas leaving an ",[63,567,71],{"href":70},[63,569,76],{"href":75}," system. It is the single most important operational KPI after NOx reduction itself: slip is regulated (typically capped at 2–10 ppm in permits), represents wasted reagent, and drives downstream fouling.",[79,572,574],{"id":573},"causes-of-high-ammonia-slip","Causes of high ammonia slip",[157,576,577,585,595,601,606],{},[160,578,579,582,583],{},[59,580,581],{},"Poor NH₃\u002FNOx mixing"," at the ",[63,584,194],{"href":193},[160,586,587,72,591,594],{},[59,588,589],{},[63,590,167],{"href":166},[63,592,593],{"href":184},"pluggage"," reducing active surface area",[160,596,597,600],{},[59,598,599],{},"Catalyst age and de-activation"," towards end of life",[160,602,603],{},[59,604,605],{},"Operating temperature outside the catalyst window",[160,607,608,611],{},[59,609,610],{},"Over-injection of ammonia"," to compensate for falling NOx-reduction efficiency",[79,613,615],{"id":614},"downstream-consequences","Downstream consequences",[56,617,618,619,622,623,361,626,630],{},"Slipped ammonia combines with SO₃ in cooling flue gas to form ",[63,620,621],{"href":489},"ammonium bisulphate (ABS)",", a sticky low-melting deposit that fouls ",[63,624,625],{"href":494},"air heaters",[63,627,629],{"href":628},"\u002Fglossary\u002Feconomiser","economisers"," and downstream catalysts and filters. Excessive slip can therefore destroy the cold end of a boiler within months.",[79,632,634],{"id":633},"sonic-horns-and-slip-reduction","Sonic horns and slip reduction",[56,636,637,639,640,643],{},[63,638,212],{"href":211}," reduce slip indirectly by keeping the catalyst face clear of ",[63,641,642],{"href":166},"masking"," deposits, which preserves active surface area, which lets the catalyst convert ammonia to nitrogen instead of letting it slip. They also keep the AIG decks clean, preserving the designed spray pattern.",[79,645,222],{"id":221},[157,647,648,652,656,660,664],{},[160,649,650],{},[63,651,229],{"href":70},[160,653,654],{},[63,655,234],{"href":75},[160,657,658],{},[63,659,378],{"href":193},[160,661,662],{},[63,663,533],{"href":489},[160,665,666],{},[63,667,167],{"href":166},{"title":245,"searchDepth":246,"depth":246,"links":669},[670,671,672,673],{"id":573,"depth":246,"text":574},{"id":614,"depth":246,"text":615},{"id":633,"depth":246,"text":634},{"id":221,"depth":246,"text":222},"Ammonia slip is the concentration of unreacted ammonia (NH₃) in the flue gas leaving an SCR or SNCR system. It is the single most important operational KPI after NOx reduction itself: slip is regulated (typically capped at 2–10 ppm in permits), represents wasted reagent, and drives downstream fouling.",{},[259,260,411,543,262],{"title":678,"description":679},"Ammonia slip — unreacted NH3 leaving an SCR or SNCR system","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.",[681],{"title":268,"url":269},"glossary\u002Fammonia-slip","BU6p3qY3enI-T7Yz_rpYjEbWD0YUtLcL2fA38Y4iZN0",{"id":685,"title":167,"aliases":686,"body":690,"category":252,"description":823,"extension":254,"meta":824,"navigation":256,"path":166,"relatedTerms":825,"seo":827,"sources":830,"stem":835,"term":167,"__hash__":836},"glossary\u002Fglossary\u002Fcatalyst-masking.md",[687,688,689],"SCR catalyst masking","catalyst fouling","face plugging",{"type":53,"value":691,"toc":817},[692,701,705,759,762,766,780,784,793,795],[56,693,694,696,697,700],{},[59,695,167],{}," is the deposition of a thin blanket of fine ash on the face of an ",[63,698,699],{"href":70},"SCR catalyst"," that physically blocks ammonia and NOx molecules from reaching the underlying active sites. Gas continues to flow through the catalyst cells, but the active surface area is shadowed and reaction efficiency falls.",[79,702,704],{"id":703},"how-masking-differs-from-related-failure-modes","How masking differs from related failure modes",[84,706,707,720],{},[87,708,709],{},[90,710,711,714,717],{},[93,712,713],{},"Failure mode",[93,715,716],{},"Mechanism",[93,718,719],{},"Reversible?",[107,721,722,734,746],{},[90,723,724,728,731],{},[112,725,726],{},[59,727,350],{},[112,729,730],{},"Ash blanket on the active surface",[112,732,733],{},"Yes — cleaning restores activity",[90,735,736,740,743],{},[112,737,738],{},[63,739,333],{"href":184},[112,741,742],{},"Particles physically block catalyst channels",[112,744,745],{},"Sometimes (depends on hardness)",[90,747,748,753,756],{},[112,749,750],{},[63,751,752],{"href":175},"Poisoning",[112,754,755],{},"Chemical species bind to active sites",[112,757,758],{},"Usually no — catalyst replacement",[56,760,761],{},"Masking is the most operationally manageable of the three because it responds to cleaning.",[79,763,765],{"id":764},"what-deposits-cause-masking","What deposits cause masking",[157,767,768,771,774,777],{},[160,769,770],{},"Calcium-rich fly ash (Western US sub-bituminous, biomass)",[160,772,773],{},"Ammonium-salt films on tail-end SCRs",[160,775,776],{},"Sub-micron silica from biomass fuels",[160,778,779],{},"Iron-oxide carry-over from blast-furnace or sinter-plant SCR applications",[79,781,783],{"id":782},"sonic-horns-and-masking-control","Sonic horns and masking control",[56,785,786,788,789,792],{},[63,787,212],{"href":211}," positioned upstream of each catalyst layer continuously dislodge the developing ash blanket before it consolidates. Combined with periodic steam ",[63,790,791],{"href":216},"sootblowing",", this two-tier cleaning typically restores catalyst activity by 10–30% within months of installation.",[79,794,222],{"id":221},[157,796,797,801,805,809,813],{},[160,798,799],{},[63,800,229],{"href":70},[160,802,803],{},[63,804,185],{"href":184},[160,806,807],{},[63,808,176],{"href":175},[160,810,811],{},[63,812,396],{"href":395},[160,814,815],{},[63,816,401],{"href":211},{"title":245,"searchDepth":246,"depth":246,"links":818},[819,820,821,822],{"id":703,"depth":246,"text":704},{"id":764,"depth":246,"text":765},{"id":782,"depth":246,"text":783},{"id":221,"depth":246,"text":222},"Catalyst masking is the deposition of a thin blanket of fine ash on the face of an SCR catalyst that physically blocks ammonia and NOx molecules from reaching the underlying active sites. Gas continues to flow through the catalyst cells, but the active surface area is shadowed and reaction efficiency falls.",{},[259,412,826,413,414],"catalyst-poisoning",{"title":828,"description":829},"Catalyst masking — fine-ash blanket that suppresses SCR activity","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.",[831,832],{"title":423,"url":424},{"title":833,"url":834},"Integrated Global Services — SCR Fouling Solved","https:\u002F\u002Fintegratedglobal.com\u002Fen\u002Fcase_studies\u002Fscr-performance\u002F","glossary\u002Fcatalyst-masking","WbNY355NxnwGZ3FW-bDAalSFTSrruJrjYN-62Fgc5Ig",1782613751455]