[{"data":1,"prerenderedAt":679},["ShallowReactive",2],{"site-footer-common":3,"glossary:urea-sncr-aqueous-ammonia-sncr":45,"glossary-related:urea-sncr-aqueous-ammonia-sncr":244},{"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":225,"description":226,"extension":227,"meta":228,"navigation":229,"path":230,"relatedTerms":231,"seo":234,"sources":237,"stem":241,"term":242,"__hash__":243},"glossary\u002Fglossary\u002Furea-sncr-aqueous-ammonia-sncr.md","Urea SNCR \u002F aqueous-ammonia SNCR",[49,50,51],"urea SNCR","aqueous ammonia SNCR","reagent choice SNCR",{"type":53,"value":54,"toc":218},"minimark",[55,75,80,178,182,195,199],[56,57,58,66,67,70,71,74],"p",{},[59,60,62],"a",{"href":61},"\u002Fglossary\u002Fselective-non-catalytic-reduction",[63,64,65],"strong",{},"SNCR"," systems use one of two principal NOx-reducing reagents: ",[63,68,69],{},"urea"," (CO(NH₂)₂, usually delivered as 32–50% aqueous solution) or ",[63,72,73],{},"aqueous ammonia"," (NH₃ at 19–29% in water).",[76,77,79],"h2",{"id":78},"reagent-comparison","Reagent comparison",[81,82,83,99],"table",{},[84,85,86],"thead",{},[87,88,89,93,96],"tr",{},[90,91,92],"th",{},"Attribute",[90,94,95],{},"Urea",[90,97,98],{},"Aqueous ammonia",[100,101,102,114,125,136,147,156,167],"tbody",{},[87,103,104,108,111],{},[105,106,107],"td",{},"Storage hazard class",[105,109,110],{},"Non-hazardous",[105,112,113],{},"Toxic \u002F corrosive",[87,115,116,119,122],{},[105,117,118],{},"Required setback distance",[105,120,121],{},"Modest",[105,123,124],{},"Large (depends on jurisdiction)",[87,126,127,130,133],{},[105,128,129],{},"Permit complexity",[105,131,132],{},"Lower",[105,134,135],{},"Higher",[87,137,138,141,144],{},[105,139,140],{},"Reaction rate",[105,142,143],{},"Slower (decomposes first to NH₃)",[105,145,146],{},"Faster (direct NH₃)",[87,148,149,152,154],{},[105,150,151],{},"Reagent cost per kg-NO removed",[105,153,135],{},[105,155,132],{},[87,157,158,161,164],{},[105,159,160],{},"Suitability for cold furnaces",[105,162,163],{},"Good",[105,165,166],{},"Less good — vaporisation\u002Fdistribution issues",[87,168,169,172,175],{},[105,170,171],{},"Solid by-product risk",[105,173,174],{},"Urea solids at lance tips",[105,176,177],{},"None",[76,179,181],{"id":180},"selection-drivers","Selection drivers",[56,183,184,185,189,190,194],{},"Many plants choose urea for the permitting and safety advantages despite its higher reagent cost; large utilities with established ammonia handling tend towards aqueous ammonia for the lower OPEX. Both reagents produce the same ",[59,186,188],{"href":187},"\u002Fglossary\u002Fammonia-slip","ammonia slip"," and downstream ",[59,191,193],{"href":192},"\u002Fglossary\u002Fammonium-bisulphate","ammonium-bisulphate"," consequences when slip is high.",[76,196,198],{"id":197},"related-terms","Related terms",[200,201,202,208,213],"ul",{},[203,204,205],"li",{},[59,206,207],{"href":61},"Selective Non-Catalytic Reduction (SNCR)",[203,209,210],{},[59,211,212],{"href":187},"Ammonia slip",[203,214,215],{},[59,216,217],{"href":192},"Ammonium bisulphate",{"title":219,"searchDepth":220,"depth":220,"links":221},"",2,[222,223,224],{"id":78,"depth":220,"text":79},{"id":180,"depth":220,"text":181},{"id":197,"depth":220,"text":198},"scr-sncr","SNCR systems use one of two principal NOx-reducing reagents: urea (CO(NH₂)₂, usually delivered as 32–50% aqueous solution) or aqueous ammonia (NH₃ at 19–29% in water).","md",{},true,"\u002Fglossary\u002Furea-sncr-aqueous-ammonia-sncr",[232,233,193],"selective-non-catalytic-reduction","ammonia-slip",{"title":235,"description":236},"Urea SNCR vs aqueous-ammonia SNCR — reagent choice for NOx reduction","SNCR systems use either solid urea (dissolved on site) or aqueous-ammonia solution as the NOx-reducing reagent. Urea is safer to store; aqueous ammonia is more reactive.",[238],{"title":239,"url":240},"Mehldau & Steinfath — SNCR Process for Coal-fired Boilers","https:\u002F\u002Fwww.ms-umwelt.de\u002Fwp-content\u002Fuploads\u002F2020\u002F08\u002F2013.06-PG-Europe__Vienna-SNCR-Process-for-Coal-Fired-Boilers-Experiences-and-Potential-for-the-Future.pdf","glossary\u002Furea-sncr-aqueous-ammonia-sncr","Urea SNCR and aqueous-ammonia SNCR","nnM_JfiERkVAReJLvNxC2rGAlhJF_Q2qHY2BF1w62bc",[245,378,520],{"id":246,"title":207,"aliases":247,"body":249,"category":225,"description":362,"extension":227,"meta":363,"navigation":229,"path":61,"relatedTerms":364,"seo":368,"sources":371,"stem":375,"term":376,"__hash__":377},"glossary\u002Fglossary\u002Fselective-non-catalytic-reduction.md",[65,248],"SNCR system",{"type":53,"value":250,"toc":357},[251,264,268,294,298,301,323,330,332],[56,252,253,255,256,260,261,263],{},[63,254,207],{}," 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 ",[59,257,259],{"href":258},"\u002Fglossary\u002Fselective-catalytic-reduction","SCR"," but achieves lower reduction (typically 30–60%) and produces higher ",[59,262,188],{"href":187},".",[76,265,267],{"id":266},"where-sncr-is-used","Where SNCR is used",[200,269,270,273,284,291],{},[203,271,272],{},"Smaller industrial and utility boilers where SCR capital cost is unjustified",[203,274,275,279,280,283],{},[59,276,278],{"href":277},"\u002Fglossary\u002Fwaste-to-energy","Waste-to-energy"," and ",[59,281,282],{"href":277},"biomass"," plants — often as the primary DeNOx with optional SCR polish",[203,285,286,290],{},[59,287,289],{"href":288},"\u002Fglossary\u002Fpreheater-tower","Cement preheater towers"," where the gas temperature window is naturally available",[203,292,293],{},"As a retrofit on units where space prevents SCR installation",[76,295,297],{"id":296},"fouling-implications","Fouling implications",[56,299,300],{},"SNCR does not have a catalyst to foul, but the reagent injection itself creates downstream deposit risks:",[200,302,303,317],{},[203,304,305,308,309,312,313],{},[63,306,307],{},"Ammonia salt deposits"," — un-reacted ammonia combines with SO₃ and ash to form ",[59,310,311],{"href":192},"ammonium bisulphate"," on cold-end heat-transfer surfaces, particularly the ",[59,314,316],{"href":315},"\u002Fglossary\u002Fair-heater","air heater",[203,318,319,322],{},[63,320,321],{},"Urea \u002F ammonia deposits on lance tips"," — injection lances can plug with urea solids or carbon deposits",[56,324,325,329],{},[59,326,328],{"href":327},"\u002Fglossary\u002Fsonic-horn","Sonic horns"," on the cold-end air heater address ABS fouling that follows SNCR operation.",[76,331,198],{"id":197},[200,333,334,339,345,349,353],{},[203,335,336],{},[59,337,338],{"href":258},"Selective Catalytic Reduction (SCR)",[203,340,341],{},[59,342,344],{"href":343},"\u002Fglossary\u002Fdenox","DeNOx",[203,346,347],{},[59,348,47],{"href":230},[203,350,351],{},[59,352,212],{"href":187},[203,354,355],{},[59,356,217],{"href":192},{"title":219,"searchDepth":220,"depth":220,"links":358},[359,360,361],{"id":266,"depth":220,"text":267},{"id":296,"depth":220,"text":297},{"id":197,"depth":220,"text":198},"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.",{},[365,366,367,233,193],"selective-catalytic-reduction","denox","urea-sncr-aqueous-ammonia-sncr",{"title":369,"description":370},"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.",[372],{"title":373,"url":374},"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":379,"title":212,"aliases":380,"body":383,"category":225,"description":506,"extension":227,"meta":507,"navigation":229,"path":187,"relatedTerms":508,"seo":511,"sources":514,"stem":518,"term":212,"__hash__":519},"glossary\u002Fglossary\u002Fammonia-slip.md",[381,382],"NH3 slip","ammonia breakthrough",{"type":53,"value":384,"toc":500},[385,396,400,442,446,462,466,475,477],[56,386,387,389,390,392,393,395],{},[63,388,212],{}," is the concentration of unreacted ammonia (NH₃) in the flue gas leaving an ",[59,391,259],{"href":258}," or ",[59,394,65],{"href":61}," 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.",[76,397,399],{"id":398},"causes-of-high-ammonia-slip","Causes of high ammonia slip",[200,401,402,412,425,431,436],{},[203,403,404,407,408],{},[63,405,406],{},"Poor NH₃\u002FNOx mixing"," at the ",[59,409,411],{"href":410},"\u002Fglossary\u002Fammonia-injection-grid","AIG",[203,413,414,392,420,424],{},[63,415,416],{},[59,417,419],{"href":418},"\u002Fglossary\u002Fcatalyst-masking","Catalyst masking",[59,421,423],{"href":422},"\u002Fglossary\u002Fcatalyst-pluggage","pluggage"," reducing active surface area",[203,426,427,430],{},[63,428,429],{},"Catalyst age and de-activation"," towards end of life",[203,432,433],{},[63,434,435],{},"Operating temperature outside the catalyst window",[203,437,438,441],{},[63,439,440],{},"Over-injection of ammonia"," to compensate for falling NOx-reduction efficiency",[76,443,445],{"id":444},"downstream-consequences","Downstream consequences",[56,447,448,449,452,453,456,457,461],{},"Slipped ammonia combines with SO₃ in cooling flue gas to form ",[59,450,451],{"href":192},"ammonium bisulphate (ABS)",", a sticky low-melting deposit that fouls ",[59,454,455],{"href":315},"air heaters",", ",[59,458,460],{"href":459},"\u002Fglossary\u002Feconomiser","economisers"," and downstream catalysts and filters. Excessive slip can therefore destroy the cold end of a boiler within months.",[76,463,465],{"id":464},"sonic-horns-and-slip-reduction","Sonic horns and slip reduction",[56,467,468,470,471,474],{},[59,469,328],{"href":327}," reduce slip indirectly by keeping the catalyst face clear of ",[59,472,473],{"href":418},"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.",[76,476,198],{"id":197},[200,478,479,483,487,492,496],{},[203,480,481],{},[59,482,338],{"href":258},[203,484,485],{},[59,486,207],{"href":61},[203,488,489],{},[59,490,491],{"href":410},"Ammonia injection grid",[203,493,494],{},[59,495,217],{"href":192},[203,497,498],{},[59,499,419],{"href":418},{"title":219,"searchDepth":220,"depth":220,"links":501},[502,503,504,505],{"id":398,"depth":220,"text":399},{"id":444,"depth":220,"text":445},{"id":464,"depth":220,"text":465},{"id":197,"depth":220,"text":198},"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.",{},[365,232,509,193,510],"ammonia-injection-grid","catalyst-masking",{"title":512,"description":513},"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.",[515],{"title":516,"url":517},"Power Engineering — Selective Catalytic Reduction: Operational Issues","https:\u002F\u002Fwww.power-eng.com\u002Fenvironmental-emissions\u002Fselective-catalytic-reduction-operational-issues-and-guidelines\u002F","glossary\u002Fammonia-slip","BU6p3qY3enI-T7Yz_rpYjEbWD0YUtLcL2fA38Y4iZN0",{"id":521,"title":522,"aliases":523,"body":528,"category":225,"description":664,"extension":227,"meta":665,"navigation":229,"path":192,"relatedTerms":666,"seo":670,"sources":673,"stem":677,"term":217,"__hash__":678},"glossary\u002Fglossary\u002Fammonium-bisulphate.md","Ammonium bisulphate (ABS)",[524,525,526,527],"ABS","ammonium bisulfate","ammonium sulphate","NH4HSO4",{"type":53,"value":529,"toc":659},[530,549,553,556,592,596,632,634],[56,531,532,535,536,539,540,543,544,546,547,263],{},[63,533,534],{},"Ammonium bisulphate (NH₄HSO₄, ABS)"," — sometimes written ",[537,538,525],"em",{}," in US technical literature — is a sticky, low-melting deposit formed when ",[59,541,542],{"href":187},"slipped ammonia"," reacts with SO₃ in cooling flue gas. ABS condenses between roughly 150 °C and 250 °C, coating the cold end of any ",[59,545,316],{"href":315}," downstream of an ",[59,548,259],{"href":258},[76,550,552],{"id":551},"why-abs-is-the-most-feared-cold-end-deposit","Why ABS is the most-feared cold-end deposit",[56,554,555],{},"ABS is uniquely problematic because it is:",[200,557,558,564,574,580,586],{},[203,559,560,563],{},[63,561,562],{},"Sticky"," — bonds tenaciously to air-heater baskets and economiser tubes",[203,565,566,569,570],{},[63,567,568],{},"Hygroscopic"," — picks up moisture and accelerates ",[59,571,573],{"href":572},"\u002Fglossary\u002Fcold-end-corrosion-dew-point-corrosion","cold-end corrosion",[203,575,576,579],{},[63,577,578],{},"Hard to remove"," — resists steam sootblowing once consolidated",[203,581,582,585],{},[63,583,584],{},"Self-reinforcing"," — coated surfaces trap more ash, accelerating fouling",[203,587,588,591],{},[63,589,590],{},"Concentrated in a narrow temperature band"," — predictably plugs the same air-heater rows",[76,593,595],{"id":594},"mitigation","Mitigation",[200,597,598,606,612,618,626],{},[203,599,600,605],{},[63,601,602,603],{},"Minimise ",[59,604,188],{"href":187}," at the SCR (the single biggest lever)",[203,607,608,611],{},[63,609,610],{},"Manage SO₃ formation"," — fuel sulphur control, catalyst formulation",[203,613,614,617],{},[63,615,616],{},"Avoid the dew-point window"," — keep cold-end gas temperature above the formation band",[203,619,620,625],{},[63,621,622,624],{},[59,623,328],{"href":327}," on the cold end"," — continuous cleaning prevents ABS from consolidating before periodic water-washing",[203,627,628,631],{},[63,629,630],{},"Water-washing campaigns"," — periodic offline washes restore air-heater performance",[76,633,198],{"id":197},[200,635,636,640,644,649,654],{},[203,637,638],{},[59,639,212],{"href":187},[203,641,642],{},[59,643,338],{"href":258},[203,645,646],{},[59,647,648],{"href":315},"Air heater",[203,650,651],{},[59,652,653],{"href":572},"Cold-end corrosion \u002F dew-point corrosion",[203,655,656],{},[59,657,658],{"href":327},"Sonic horn",{"title":219,"searchDepth":220,"depth":220,"links":660},[661,662,663],{"id":551,"depth":220,"text":552},{"id":594,"depth":220,"text":595},{"id":197,"depth":220,"text":198},"Ammonium bisulphate (NH₄HSO₄, ABS) — sometimes written ammonium bisulfate in US technical literature — is a sticky, low-melting deposit formed when slipped ammonia reacts with SO₃ in cooling flue gas. ABS condenses between roughly 150 °C and 250 °C, coating the cold end of any air heater downstream of an SCR.",{},[233,365,667,668,669],"air-heater","cold-end-corrosion-dew-point-corrosion","sonic-horn",{"title":671,"description":672},"Ammonium bisulphate (ABS) — sticky deposit from SCR slip plus SO3","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.",[674],{"title":675,"url":676},"POWER Magazine — SO3's impacts on plant O&M","https:\u002F\u002Fwww.powermag.com\u002Fso3s-impacts-on-plant-om-part-ii\u002F","glossary\u002Fammonium-bisulphate","eVfkw0arMYLXvUn7Eb2ZquRKgct13PXCySe8Iclt3GY",1782613754070]