[{"data":1,"prerenderedAt":640},["ShallowReactive",2],{"site-footer-common":3,"glossary:acid-dew-point":45,"glossary-related:acid-dew-point":185},{"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":166,"description":167,"extension":168,"meta":169,"navigation":170,"path":171,"relatedTerms":172,"seo":176,"sources":179,"stem":183,"term":47,"__hash__":184},"glossary\u002Fglossary\u002Facid-dew-point.md","Acid dew point",[49,50,51],"sulphuric acid dew point","SADT","SO3 dew point",{"type":53,"value":54,"toc":158},"minimark",[55,64,69,88,92,120,124,137,141],[56,57,58,59,63],"p",{},"The ",[60,61,62],"strong",{},"acid dew point"," is the temperature at which sulphuric acid (H₂SO₄) begins to condense from flue gas containing SO₃ and water vapour. For typical coal-fired flue gas the acid dew point sits in the 120–160 °C range, depending on SO₃ concentration and moisture content. Higher SO₃ raises the dew point; in extreme cases it reaches 180 °C.",[65,66,68],"h2",{"id":67},"why-it-matters","Why it matters",[56,70,71,72,77,78,82,83,87],{},"Operating any cold-end surface — ",[73,74,76],"a",{"href":75},"\u002Fglossary\u002Fair-heater","air heater"," baskets, ",[73,79,81],{"href":80},"\u002Fglossary\u002Feconomiser","economiser"," tubes, ducting — below the acid dew point allows condensed sulphuric acid to attack the metal, causing ",[73,84,86],{"href":85},"\u002Fglossary\u002Fcold-end-corrosion-dew-point-corrosion","cold-end corrosion",". The dew point sets the practical floor on cold-end metal temperature.",[65,89,91],{"id":90},"scr-related-complication","SCR-related complication",[56,93,94,95,99,100,104,105,109,110,114,115,119],{},"Boilers with upstream ",[73,96,98],{"href":97},"\u002Fglossary\u002Fselective-catalytic-reduction","SCR"," face a double challenge: the SCR catalyst converts a fraction of SO₂ to SO₃ (",[73,101,103],{"href":102},"\u002Fglossary\u002Fso2-so3-conversion","SO₂\u002FSO₃ conversion","), raising the dew point, ",[106,107,108],"em",{},"and"," unreacted ",[73,111,113],{"href":112},"\u002Fglossary\u002Fammonia-slip","ammonia slip"," combines with SO₃ to form ",[73,116,118],{"href":117},"\u002Fglossary\u002Fammonium-bisulphate","ammonium bisulphate"," that condenses and fouls cold-end surfaces in the same temperature window.",[65,121,123],{"id":122},"operational-implications","Operational implications",[125,126,127,131,134],"ul",{},[128,129,130],"li",{},"Cold-end air-heater inlet temperature is normally controlled at least 10–15 °C above the calculated dew point",[128,132,133],{},"Steam coil air heaters or hot-air recirculation raise inlet air temperature during low-load operation",[128,135,136],{},"Periodic dew-point measurement campaigns confirm the calculated value",[65,138,140],{"id":139},"related-terms","Related terms",[125,142,143,148,153],{},[128,144,145],{},[73,146,147],{"href":85},"Cold-end corrosion \u002F dew-point corrosion",[128,149,150],{},[73,151,152],{"href":75},"Air heater",[128,154,155],{},[73,156,157],{"href":117},"Ammonium bisulphate",{"title":159,"searchDepth":160,"depth":160,"links":161},"",2,[162,163,164,165],{"id":67,"depth":160,"text":68},{"id":90,"depth":160,"text":91},{"id":122,"depth":160,"text":123},{"id":139,"depth":160,"text":140},"boiler","The acid dew point is the temperature at which sulphuric acid (H₂SO₄) begins to condense from flue gas containing SO₃ and water vapour. For typical coal-fired flue gas the acid dew point sits in the 120–160 °C range, depending on SO₃ concentration and moisture content. Higher SO₃ raises the dew point; in extreme cases it reaches 180 °C.","md",{},true,"\u002Fglossary\u002Facid-dew-point",[173,174,175],"cold-end-corrosion-dew-point-corrosion","air-heater","ammonium-bisulphate",{"title":177,"description":178},"Acid dew point — temperature at which sulphuric acid condenses from flue gas","The acid dew point is the temperature at which sulphuric acid condenses from flue gas containing SO3 and water vapour. Cold-end metal temperatures must be kept above it.",[180],{"title":181,"url":182},"POWER Magazine — SO3's impacts on plant O&M","https:\u002F\u002Fwww.powermag.com\u002Fso3s-impacts-on-plant-om-part-ii\u002F","glossary\u002Facid-dew-point","LF2CjgPQtrngyjMNvCFxb-1is5GIA-MYJO6t4FzoDhs",[186,308,489],{"id":187,"title":147,"aliases":188,"body":192,"category":166,"description":295,"extension":168,"meta":296,"navigation":170,"path":85,"relatedTerms":297,"seo":300,"sources":303,"stem":305,"term":306,"__hash__":307},"glossary\u002Fglossary\u002Fcold-end-corrosion-dew-point-corrosion.md",[189,190,191],"cold end corrosion","dew point corrosion","sulphuric acid corrosion (boiler)",{"type":53,"value":193,"toc":290},[194,212,216,219,233,236,240,263,265],[56,195,196,199,200,203,204,77,206,208,209,211],{},[60,197,198],{},"Cold-end corrosion"," (also ",[106,201,202],{},"dew-point corrosion",") is the attack on boiler ",[73,205,174],{"href":75},[73,207,81],{"href":80}," tubes and downstream ducting where flue-gas temperature falls below the ",[73,210,62],{"href":171}," 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.",[65,213,215],{"id":214},"the-interplay-with-fouling","The interplay with fouling",[56,217,218],{},"Cold-end corrosion and fouling reinforce each other:",[125,220,221,224,227],{},[128,222,223],{},"Condensed acid bonds dust to surfaces — fouling consolidates faster",[128,225,226],{},"Fouled tubes run cooler than design — more acid condenses",[128,228,229,232],{},[73,230,231],{"href":117},"Ammonium bisulphate (ABS)"," deposits accelerate both processes",[56,234,235],{},"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.",[65,237,239],{"id":238},"mitigation","Mitigation",[125,241,242,247,250,253,256],{},[128,243,244,245],{},"Maintain cold-end metal temperature above the ",[73,246,62],{"href":171},[128,248,249],{},"Manage fuel sulphur and SCR SO₂\u002FSO₃ conversion",[128,251,252],{},"Use corrosion-resistant materials (Cor-Ten, enamel-coated baskets) at the cold end",[128,254,255],{},"Periodic water-washing of cold-end baskets and tubes",[128,257,258,262],{},[73,259,261],{"href":260},"\u002Fglossary\u002Fsonic-horn","Sonic horns"," to keep deposits from consolidating",[65,264,140],{"id":139},[125,266,267,271,276,280,284],{},[128,268,269],{},[73,270,152],{"href":75},[128,272,273],{},[73,274,275],{"href":80},"Economiser",[128,277,278],{},[73,279,157],{"href":117},[128,281,282],{},[73,283,47],{"href":171},[128,285,286],{},[73,287,289],{"href":288},"\u002Fglossary\u002Fboiler-tube-failure","Boiler tube failure",{"title":159,"searchDepth":160,"depth":160,"links":291},[292,293,294],{"id":214,"depth":160,"text":215},{"id":238,"depth":160,"text":239},{"id":139,"depth":160,"text":140},"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.",{},[174,81,175,298,299],"acid-dew-point","boiler-tube-failure",{"title":301,"description":302},"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.",[304],{"title":181,"url":182},"glossary\u002Fcold-end-corrosion-dew-point-corrosion","Cold-end corrosion and dew-point corrosion","IO_wdcX5SRjrSEY4SMku6RmkWNHXkuMTmeI4uHpz1dI",{"id":309,"title":310,"aliases":311,"body":315,"category":166,"description":474,"extension":168,"meta":475,"navigation":170,"path":75,"relatedTerms":476,"seo":480,"sources":483,"stem":487,"term":152,"__hash__":488},"glossary\u002Fglossary\u002Fair-heater.md","Air heater (APH)",[312,313,314],"air preheater","APH","air heaters",{"type":53,"value":316,"toc":468},[317,331,335,385,389,402,424,428,435,437],[56,318,319,320,322,323,325,326,330],{},"An ",[60,321,76],{}," — also called an ",[60,324,312],{}," (APH) — is the final heat-recovery device in a boiler's ",[73,327,329],{"href":328},"\u002Fglossary\u002Fconvective-pass-backpass","convective pass",", recovering low-grade heat from cooling flue gas to preheat the combustion air. APHs lift overall boiler efficiency by 5–10 percentage points and are critical to heat-rate performance.",[65,332,334],{"id":333},"aph-types","APH types",[336,337,338,351],"table",{},[339,340,341],"thead",{},[342,343,344,348],"tr",{},[345,346,347],"th",{},"Type",[345,349,350],{},"Description",[352,353,354,366,377],"tbody",{},[342,355,356,363],{},[357,358,359],"td",{},[73,360,362],{"href":361},"\u002Fglossary\u002Fljungstrom-air-preheater","Ljungström \u002F regenerative",[357,364,365],{},"Rotating matrix of heat-exchange baskets cycling between gas and air sides",[342,367,368,374],{},[357,369,370],{},[73,371,373],{"href":372},"\u002Fglossary\u002Ftubular-air-preheater","Tubular",[357,375,376],{},"Fixed tube bundle with flue gas through tubes, air around them",[342,378,379,382],{},[357,380,381],{},"Plate-type",[357,383,384],{},"Cross-flow plate exchanger; smaller industrial duty",[65,386,388],{"id":387},"the-cold-end-problem","The cold-end problem",[56,390,391,392,396,397,401],{},"The APH cold end is the coolest point in the flue-gas path before the ",[73,393,395],{"href":394},"\u002Fglossary\u002Felectrostatic-precipitator","ESP"," \u002F ",[73,398,400],{"href":399},"\u002Fglossary\u002Fbaghouse","baghouse",". Two related failure modes dominate:",[125,403,404,414],{},[128,405,406,410,411,413],{},[60,407,408],{},[73,409,231],{"href":117}," fouling on boilers with upstream ",[73,412,98],{"href":97},": sticky deposits plug Ljungström baskets and tubular APH tubes",[128,415,416,420,421,423],{},[60,417,418],{},[73,419,198],{"href":85}," below the ",[73,422,62],{"href":171}," — sulphuric acid condenses and attacks baskets and tubes",[65,425,427],{"id":426},"why-sonic-horns-are-routinely-specified-on-aphs","Why sonic horns are routinely specified on APHs",[56,429,430,431,434],{},"ABS fouling is the single most common reason plants install ",[73,432,433],{"href":260},"sonic horns"," on the cold end. Continuous low-amplitude vibration prevents ABS from consolidating between water-wash campaigns, extending the campaign interval from quarterly to annual and avoiding capacity-derate excursions.",[65,436,140],{"id":139},[125,438,439,445,450,455,459,463],{},[128,440,441],{},[73,442,444],{"href":443},"\u002Fglossary\u002Fboiler","Boiler",[128,446,447],{},[73,448,449],{"href":361},"Ljungström air preheater",[128,451,452],{},[73,453,454],{"href":372},"Tubular air preheater",[128,456,457],{},[73,458,157],{"href":117},[128,460,461],{},[73,462,147],{"href":85},[128,464,465],{},[73,466,467],{"href":260},"Sonic horn",{"title":159,"searchDepth":160,"depth":160,"links":469},[470,471,472,473],{"id":333,"depth":160,"text":334},{"id":387,"depth":160,"text":388},{"id":426,"depth":160,"text":427},{"id":139,"depth":160,"text":140},"An air heater — also called an air preheater (APH) — is the final heat-recovery device in a boiler's convective pass, recovering low-grade heat from cooling flue gas to preheat the combustion air. APHs lift overall boiler efficiency by 5–10 percentage points and are critical to heat-rate performance.",{},[166,477,478,175,173,479],"ljungstrom-air-preheater","tubular-air-preheater","sonic-horn",{"title":481,"description":482},"Air heater (APH) — final flue-gas heat-recovery device before the stack","An air heater (also air preheater, APH) recovers low-grade heat from flue gas to preheat combustion air. Cold-end fouling and corrosion are the dominant operational challenges.",[484],{"title":485,"url":486},"Wikipedia — Air preheater","https:\u002F\u002Fen.wikipedia.org\u002Fwiki\u002FAir_preheater","glossary\u002Fair-heater","3pBQ2ZyiQ7VOKuf9rxsx43EFarkhgykVhd2amXg0TMY",{"id":490,"title":231,"aliases":491,"body":496,"category":627,"description":628,"extension":168,"meta":629,"navigation":170,"path":117,"relatedTerms":630,"seo":633,"sources":636,"stem":638,"term":157,"__hash__":639},"glossary\u002Fglossary\u002Fammonium-bisulphate.md",[492,493,494,495],"ABS","ammonium bisulfate","ammonium sulphate","NH4HSO4",{"type":53,"value":497,"toc":622},[498,517,521,524,558,560,596,598],[56,499,500,503,504,506,507,510,511,513,514,516],{},[60,501,502],{},"Ammonium bisulphate (NH₄HSO₄, ABS)"," — sometimes written ",[106,505,493],{}," in US technical literature — is a sticky, low-melting deposit formed when ",[73,508,509],{"href":112},"slipped ammonia"," reacts with SO₃ in cooling flue gas. ABS condenses between roughly 150 °C and 250 °C, coating the cold end of any ",[73,512,76],{"href":75}," downstream of an ",[73,515,98],{"href":97},".",[65,518,520],{"id":519},"why-abs-is-the-most-feared-cold-end-deposit","Why ABS is the most-feared cold-end deposit",[56,522,523],{},"ABS is uniquely problematic because it is:",[125,525,526,532,540,546,552],{},[128,527,528,531],{},[60,529,530],{},"Sticky"," — bonds tenaciously to air-heater baskets and economiser tubes",[128,533,534,537,538],{},[60,535,536],{},"Hygroscopic"," — picks up moisture and accelerates ",[73,539,86],{"href":85},[128,541,542,545],{},[60,543,544],{},"Hard to remove"," — resists steam sootblowing once consolidated",[128,547,548,551],{},[60,549,550],{},"Self-reinforcing"," — coated surfaces trap more ash, accelerating fouling",[128,553,554,557],{},[60,555,556],{},"Concentrated in a narrow temperature band"," — predictably plugs the same air-heater rows",[65,559,239],{"id":238},[125,561,562,570,576,582,590],{},[128,563,564,569],{},[60,565,566,567],{},"Minimise ",[73,568,113],{"href":112}," at the SCR (the single biggest lever)",[128,571,572,575],{},[60,573,574],{},"Manage SO₃ formation"," — fuel sulphur control, catalyst formulation",[128,577,578,581],{},[60,579,580],{},"Avoid the dew-point window"," — keep cold-end gas temperature above the formation band",[128,583,584,589],{},[60,585,586,588],{},[73,587,261],{"href":260}," on the cold end"," — continuous cleaning prevents ABS from consolidating before periodic water-washing",[128,591,592,595],{},[60,593,594],{},"Water-washing campaigns"," — periodic offline washes restore air-heater performance",[65,597,140],{"id":139},[125,599,600,605,610,614,618],{},[128,601,602],{},[73,603,604],{"href":112},"Ammonia slip",[128,606,607],{},[73,608,609],{"href":97},"Selective Catalytic Reduction (SCR)",[128,611,612],{},[73,613,152],{"href":75},[128,615,616],{},[73,617,147],{"href":85},[128,619,620],{},[73,621,467],{"href":260},{"title":159,"searchDepth":160,"depth":160,"links":623},[624,625,626],{"id":519,"depth":160,"text":520},{"id":238,"depth":160,"text":239},{"id":139,"depth":160,"text":140},"scr-sncr","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.",{},[631,632,174,173,479],"ammonia-slip","selective-catalytic-reduction",{"title":634,"description":635},"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.",[637],{"title":181,"url":182},"glossary\u002Fammonium-bisulphate","eVfkw0arMYLXvUn7Eb2ZquRKgct13PXCySe8Iclt3GY",1782613724307]