[{"data":1,"prerenderedAt":634},["ShallowReactive",2],{"site-footer-common":3,"glossary:so2-so3-conversion":45,"glossary-related:so2-so3-conversion":189},{"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":169,"description":170,"extension":171,"meta":172,"navigation":173,"path":174,"relatedTerms":175,"seo":179,"sources":182,"stem":186,"term":187,"__hash__":188},"glossary\u002Fglossary\u002Fso2-so3-conversion.md","SO₂\u002FSO₃ conversion",[49,50,51],"SO2 to SO3","SCR SO3 generation","sulphur oxidation in SCR",{"type":53,"value":54,"toc":162},"minimark",[55,68,106,111,125,129,141,145],[56,57,58,61,62,67],"p",{},[59,60,47],"strong",{}," refers to the unwanted side reaction whereby ",[63,64,66],"a",{"href":65},"\u002Fglossary\u002Fselective-catalytic-reduction","SCR catalyst"," oxidises a fraction of the flue-gas SO₂ to SO₃ — typically 0.3–1.5% across a high-dust SCR. The newly-formed SO₃ has three downstream consequences, all undesirable:",[69,70,71,85,100],"ul",{},[72,73,74,80,81],"li",{},[59,75,76],{},[63,77,79],{"href":78},"\u002Fglossary\u002Fammonium-bisulphate","Ammonium bisulphate (ABS)"," formation in cooler downstream zones, plugging ",[63,82,84],{"href":83},"\u002Fglossary\u002Fair-heater","air heaters",[72,86,87,90,91,95,96],{},[59,88,89],{},"Sulphuric-acid dew-point excursion"," in ",[63,92,94],{"href":93},"\u002Fglossary\u002Feconomiser","economisers"," and ducting, driving ",[63,97,99],{"href":98},"\u002Fglossary\u002Fcold-end-corrosion-dew-point-corrosion","cold-end corrosion",[72,101,102,105],{},[59,103,104],{},"Visible blue plume"," from sulphate aerosol at the stack",[107,108,110],"h2",{"id":109},"minimising-conversion","Minimising conversion",[69,112,113,116,119,122],{},[72,114,115],{},"Catalyst formulation tuned for low V₂O₅ content (V is the conversion driver)",[72,117,118],{},"Lower SCR operating temperature where the catalyst window allows",[72,120,121],{},"Reduced excess air at the burner to limit SO₃ formation",[72,123,124],{},"Fuel sulphur control where economically possible",[107,126,128],{"id":127},"why-it-matters-for-cleaning","Why it matters for cleaning",[56,130,131,132,135,136,140],{},"Higher SO₃ means more ABS in the cold end. Plants with significant SO₂\u002FSO₃ conversion face heavier ",[63,133,134],{"href":83},"air-heater"," fouling and benefit more from ",[63,137,139],{"href":138},"\u002Fglossary\u002Fsonic-horn","sonic-horn"," installation on the cold end.",[107,142,144],{"id":143},"related-terms","Related terms",[69,146,147,152,157],{},[72,148,149],{},[63,150,151],{"href":65},"Selective Catalytic Reduction (SCR)",[72,153,154],{},[63,155,156],{"href":78},"Ammonium bisulphate",[72,158,159],{},[63,160,161],{"href":98},"Cold-end corrosion \u002F dew-point corrosion",{"title":163,"searchDepth":164,"depth":164,"links":165},"",2,[166,167,168],{"id":109,"depth":164,"text":110},{"id":127,"depth":164,"text":128},{"id":143,"depth":164,"text":144},"scr-sncr","SO₂\u002FSO₃ conversion refers to the unwanted side reaction whereby SCR catalyst oxidises a fraction of the flue-gas SO₂ to SO₃ — typically 0.3–1.5% across a high-dust SCR. The newly-formed SO₃ has three downstream consequences, all undesirable:","md",{},true,"\u002Fglossary\u002Fso2-so3-conversion",[176,177,178],"selective-catalytic-reduction","ammonium-bisulphate","cold-end-corrosion-dew-point-corrosion",{"title":180,"description":181},"SO2\u002FSO3 conversion — unwanted SCR side reaction generating sulphuric mist","SCR catalysts unintentionally oxidise a fraction of flue-gas SO2 to SO3. Higher SO3 means more cold-end corrosion, more ammonium bisulphate and more visible plume.",[183],{"title":184,"url":185},"POWER Magazine — SO3's impacts on plant O&M","https:\u002F\u002Fwww.powermag.com\u002Fso3s-impacts-on-plant-om-part-ii\u002F","glossary\u002Fso2-so3-conversion","SO₂\u002FSO₃ conversion (in SCR)","qG9c5tO1N9JI9TVv_OtEBzeznxm5JdxTD2GHYk4C4CM",[190,359,511],{"id":191,"title":151,"aliases":192,"body":196,"category":169,"description":336,"extension":171,"meta":337,"navigation":173,"path":65,"relatedTerms":338,"seo":346,"sources":349,"stem":356,"term":357,"__hash__":358},"glossary\u002Fglossary\u002Fselective-catalytic-reduction.md",[193,194,195],"SCR","SCR system","SCR reactor",{"type":53,"value":197,"toc":331},[198,217,221,237,241,244,273,290,292],[56,199,200,202,203,207,208,212,213,216],{},[59,201,151],{}," is the dominant flue-gas NOx-control technology on coal-fired and gas-fired utility boilers, ",[63,204,206],{"href":205},"\u002Fglossary\u002Fheat-recovery-steam-generator","HRSGs"," in combined-cycle plants, ",[63,209,211],{"href":210},"\u002Fglossary\u002Fwaste-to-energy","waste-to-energy"," and ",[63,214,215],{"href":210},"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.",[107,218,220],{"id":219},"reactor-layout","Reactor layout",[56,222,223,224,228,229,232,233,236],{},"A typical SCR reactor is a vertical or horizontal duct containing 2–4 layers of catalyst modules. Upstream of the catalyst sits the ",[63,225,227],{"href":226},"\u002Fglossary\u002Fammonia-injection-grid","ammonia injection grid (AIG)"," that distributes the ammonia evenly into the flue gas. Most installations operate in the ",[59,230,231],{},"high-dust"," position (between economiser and air heater) where catalyst temperature is around 300–400 °C; ",[59,234,235],{},"tail-end"," SCRs sit downstream of particulate control at lower temperatures, with the trade-off of needing flue-gas reheating.",[107,238,240],{"id":239},"fouling-and-cleaning","Fouling and cleaning",[56,242,243],{},"SCR catalysts foul in two ways:",[69,245,246,264],{},[72,247,248,254,255,212,259,263],{},[59,249,250],{},[63,251,253],{"href":252},"\u002Fglossary\u002Fcatalyst-pluggage","Pluggage"," — fly ash, ",[63,256,258],{"href":257},"\u002Fglossary\u002Fpopcorn-ash","popcorn ash",[63,260,262],{"href":261},"\u002Fglossary\u002Flarge-particle-ash","large-particle ash"," wedge into the catalyst cells, blocking the gas path",[72,265,266,272],{},[59,267,268],{},[63,269,271],{"href":270},"\u002Fglossary\u002Fcatalyst-masking","Masking"," — a thin layer of deposit covers the active sites; gas flow continues but catalytic activity falls",[56,274,275,276,280,281,285,286,289],{},"Both reduce NOx-reduction efficiency, raise ",[63,277,279],{"href":278},"\u002Fglossary\u002Fammonia-slip","ammonia slip",", and shorten catalyst life. Cleaning options include steam ",[63,282,284],{"href":283},"\u002Fglossary\u002Fsteam-sootblower","sootblowers",", ",[63,287,288],{"href":138},"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.",[107,291,144],{"id":143},[69,293,294,300,305,310,315,320,326],{},[72,295,296],{},[63,297,299],{"href":298},"\u002Fglossary\u002Fselective-non-catalytic-reduction","Selective Non-Catalytic Reduction (SNCR)",[72,301,302],{},[63,303,304],{"href":226},"Ammonia injection grid",[72,306,307],{},[63,308,309],{"href":278},"Ammonia slip",[72,311,312],{},[63,313,314],{"href":270},"Catalyst masking",[72,316,317],{},[63,318,319],{"href":252},"Catalyst pluggage",[72,321,322],{},[63,323,325],{"href":324},"\u002Fglossary\u002Fhoneycomb-catalyst","Honeycomb catalyst",[72,327,328],{},[63,329,330],{"href":138},"Sonic horn",{"title":163,"searchDepth":164,"depth":164,"links":332},[333,334,335],{"id":219,"depth":164,"text":220},{"id":239,"depth":164,"text":240},{"id":143,"depth":164,"text":144},"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.",{},[339,340,341,342,343,344,345,139],"selective-non-catalytic-reduction","denox","ammonia-injection-grid","ammonia-slip","catalyst-masking","catalyst-pluggage","honeycomb-catalyst",{"title":347,"description":348},"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.",[350,353],{"title":351,"url":352},"Wikipedia — Selective catalytic reduction","https:\u002F\u002Fen.wikipedia.org\u002Fwiki\u002FSelective_catalytic_reduction",{"title":354,"url":355},"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":360,"title":79,"aliases":361,"body":366,"category":169,"description":501,"extension":171,"meta":502,"navigation":173,"path":78,"relatedTerms":503,"seo":504,"sources":507,"stem":509,"term":156,"__hash__":510},"glossary\u002Fglossary\u002Fammonium-bisulphate.md",[362,363,364,365],"ABS","ammonium bisulfate","ammonium sulphate","NH4HSO4",{"type":53,"value":367,"toc":496},[368,389,393,396,430,434,471,473],[56,369,370,373,374,377,378,381,382,385,386,388],{},[59,371,372],{},"Ammonium bisulphate (NH₄HSO₄, ABS)"," — sometimes written ",[375,376,363],"em",{}," in US technical literature — is a sticky, low-melting deposit formed when ",[63,379,380],{"href":278},"slipped ammonia"," reacts with SO₃ in cooling flue gas. ABS condenses between roughly 150 °C and 250 °C, coating the cold end of any ",[63,383,384],{"href":83},"air heater"," downstream of an ",[63,387,193],{"href":65},".",[107,390,392],{"id":391},"why-abs-is-the-most-feared-cold-end-deposit","Why ABS is the most-feared cold-end deposit",[56,394,395],{},"ABS is uniquely problematic because it is:",[69,397,398,404,412,418,424],{},[72,399,400,403],{},[59,401,402],{},"Sticky"," — bonds tenaciously to air-heater baskets and economiser tubes",[72,405,406,409,410],{},[59,407,408],{},"Hygroscopic"," — picks up moisture and accelerates ",[63,411,99],{"href":98},[72,413,414,417],{},[59,415,416],{},"Hard to remove"," — resists steam sootblowing once consolidated",[72,419,420,423],{},[59,421,422],{},"Self-reinforcing"," — coated surfaces trap more ash, accelerating fouling",[72,425,426,429],{},[59,427,428],{},"Concentrated in a narrow temperature band"," — predictably plugs the same air-heater rows",[107,431,433],{"id":432},"mitigation","Mitigation",[69,435,436,444,450,456,465],{},[72,437,438,443],{},[59,439,440,441],{},"Minimise ",[63,442,279],{"href":278}," at the SCR (the single biggest lever)",[72,445,446,449],{},[59,447,448],{},"Manage SO₃ formation"," — fuel sulphur control, catalyst formulation",[72,451,452,455],{},[59,453,454],{},"Avoid the dew-point window"," — keep cold-end gas temperature above the formation band",[72,457,458,464],{},[59,459,460,463],{},[63,461,462],{"href":138},"Sonic horns"," on the cold end"," — continuous cleaning prevents ABS from consolidating before periodic water-washing",[72,466,467,470],{},[59,468,469],{},"Water-washing campaigns"," — periodic offline washes restore air-heater performance",[107,472,144],{"id":143},[69,474,475,479,483,488,492],{},[72,476,477],{},[63,478,309],{"href":278},[72,480,481],{},[63,482,151],{"href":65},[72,484,485],{},[63,486,487],{"href":83},"Air heater",[72,489,490],{},[63,491,161],{"href":98},[72,493,494],{},[63,495,330],{"href":138},{"title":163,"searchDepth":164,"depth":164,"links":497},[498,499,500],{"id":391,"depth":164,"text":392},{"id":432,"depth":164,"text":433},{"id":143,"depth":164,"text":144},"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.",{},[342,176,134,178,139],{"title":505,"description":506},"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.",[508],{"title":184,"url":185},"glossary\u002Fammonium-bisulphate","eVfkw0arMYLXvUn7Eb2ZquRKgct13PXCySe8Iclt3GY",{"id":512,"title":161,"aliases":513,"body":517,"category":620,"description":621,"extension":171,"meta":622,"navigation":173,"path":98,"relatedTerms":623,"seo":626,"sources":629,"stem":631,"term":632,"__hash__":633},"glossary\u002Fglossary\u002Fcold-end-corrosion-dew-point-corrosion.md",[514,515,516],"cold end corrosion","dew point corrosion","sulphuric acid corrosion (boiler)",{"type":53,"value":518,"toc":615},[519,541,545,548,561,564,566,587,589],[56,520,521,524,525,528,529,531,532,535,536,540],{},[59,522,523],{},"Cold-end corrosion"," (also ",[375,526,527],{},"dew-point corrosion",") is the attack on boiler ",[63,530,134],{"href":83}," baskets, ",[63,533,534],{"href":93},"economiser"," tubes and downstream ducting where flue-gas temperature falls below the ",[63,537,539],{"href":538},"\u002Fglossary\u002Facid-dew-point","acid dew point"," of the gas. SO₃ in the flue gas combines with water vapour to form sulphuric acid that condenses on the cooled surfaces and attacks them.",[107,542,544],{"id":543},"the-interplay-with-fouling","The interplay with fouling",[56,546,547],{},"Cold-end corrosion and fouling reinforce each other:",[69,549,550,553,556],{},[72,551,552],{},"Condensed acid bonds dust to surfaces — fouling consolidates faster",[72,554,555],{},"Fouled tubes run cooler than design — more acid condenses",[72,557,558,560],{},[63,559,79],{"href":78}," deposits accelerate both processes",[56,562,563],{},"The result is a self-feeding cycle: a unit that begins to foul typically also begins to corrode, and both worsen until the cold end is water-washed or rebuilt.",[107,565,433],{"id":432},[69,567,568,573,576,579,582],{},[72,569,570,571],{},"Maintain cold-end metal temperature above the ",[63,572,539],{"href":538},[72,574,575],{},"Manage fuel sulphur and SCR SO₂\u002FSO₃ conversion",[72,577,578],{},"Use corrosion-resistant materials (Cor-Ten, enamel-coated baskets) at the cold end",[72,580,581],{},"Periodic water-washing of cold-end baskets and tubes",[72,583,584,586],{},[63,585,462],{"href":138}," to keep deposits from consolidating",[107,588,144],{"id":143},[69,590,591,595,600,604,609],{},[72,592,593],{},[63,594,487],{"href":83},[72,596,597],{},[63,598,599],{"href":93},"Economiser",[72,601,602],{},[63,603,156],{"href":78},[72,605,606],{},[63,607,608],{"href":538},"Acid dew point",[72,610,611],{},[63,612,614],{"href":613},"\u002Fglossary\u002Fboiler-tube-failure","Boiler tube failure",{"title":163,"searchDepth":164,"depth":164,"links":616},[617,618,619],{"id":543,"depth":164,"text":544},{"id":432,"depth":164,"text":433},{"id":143,"depth":164,"text":144},"boiler","Cold-end corrosion (also dew-point corrosion) is the attack on boiler air-heater baskets, economiser tubes and downstream ducting where flue-gas temperature falls below the acid dew point of the gas. SO₃ in the flue gas combines with water vapour to form sulphuric acid that condenses on the cooled surfaces and attacks them.",{},[134,534,177,624,625],"acid-dew-point","boiler-tube-failure",{"title":627,"description":628},"Cold-end corrosion — sulphuric-acid attack at the boiler's coolest point","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.",[630],{"title":184,"url":185},"glossary\u002Fcold-end-corrosion-dew-point-corrosion","Cold-end corrosion and dew-point corrosion","IO_wdcX5SRjrSEY4SMku6RmkWNHXkuMTmeI4uHpz1dI",1782613751797]