[{"data":1,"prerenderedAt":651},["ShallowReactive",2],{"site-footer-common":3,"glossary:combined-cycle-gas-turbine":45,"glossary-related:combined-cycle-gas-turbine":152},{"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":131,"description":132,"extension":133,"meta":134,"navigation":135,"path":136,"relatedTerms":137,"seo":142,"sources":145,"stem":149,"term":150,"__hash__":151},"glossary\u002Fglossary\u002Fcombined-cycle-gas-turbine.md","Combined-cycle gas turbine (CCGT)",[49,50,51],"CCGT","combined cycle","combined-cycle plant",{"type":53,"value":54,"toc":124},"minimark",[55,70,75,86,90,93,97],[56,57,58,59,63,64,69],"p",{},"A ",[60,61,62],"strong",{},"combined-cycle gas turbine (CCGT)"," plant combines a gas turbine with a steam turbine driven by an ",[65,66,68],"a",{"href":67},"\u002Fglossary\u002Fheat-recovery-steam-generator","HRSG"," that recovers heat from the gas-turbine exhaust. The arrangement raises overall plant efficiency from ~38% LHV for a simple-cycle gas turbine to 55–62% LHV for modern CCGT, with the latest H-class machines pushing 64%+.",[71,72,74],"h2",{"id":73},"why-hrsg-cleanliness-matters","Why HRSG cleanliness matters",[56,76,77,78,82,83,85],{},"CCGT plants are economically dispatched ahead of coal in most markets, but margins per MWh are tight and competition from renewables intensifies the focus on heat rate. Every 0.5% efficiency loss from HRSG fouling translates directly to fuel cost. ",[65,79,81],{"href":80},"\u002Fglossary\u002Fsonic-horn","Sonic horns"," on the ",[65,84,68],{"href":67}," gas path are increasingly part of the standard maintenance toolkit on modern combined-cycle plants.",[71,87,89],{"id":88},"cycling-adds-complication","Cycling adds complication",[56,91,92],{},"Modern CCGT plants increasingly two-shift — running daytime and shutting overnight when renewable supply meets demand. Frequent start-stop cycling worsens HRSG fouling because cold metal surfaces during shutdowns condense moisture that bonds dust into a harder deposit. Continuous sonic-horn cleaning helps offset cycling-driven fouling acceleration.",[71,94,96],{"id":95},"related-terms","Related terms",[98,99,100,106,112,118],"ul",{},[101,102,103],"li",{},[65,104,105],{"href":67},"Heat Recovery Steam Generator (HRSG)",[101,107,108],{},[65,109,111],{"href":110},"\u002Fglossary\u002Fduct-burner","Duct burner",[101,113,114],{},[65,115,117],{"href":116},"\u002Fglossary\u002Fselective-catalytic-reduction","Selective Catalytic Reduction (SCR)",[101,119,120],{},[65,121,123],{"href":122},"\u002Fglossary\u002Fheat-rate","Heat rate",{"title":125,"searchDepth":126,"depth":126,"links":127},"",2,[128,129,130],{"id":73,"depth":126,"text":74},{"id":88,"depth":126,"text":89},{"id":95,"depth":126,"text":96},"hrsg-gas-path","A combined-cycle gas turbine (CCGT) plant combines a gas turbine with a steam turbine driven by an HRSG that recovers heat from the gas-turbine exhaust. The arrangement raises overall plant efficiency from ~38% LHV for a simple-cycle gas turbine to 55–62% LHV for modern CCGT, with the latest H-class machines pushing 64%+.","md",{},true,"\u002Fglossary\u002Fcombined-cycle-gas-turbine",[138,139,140,141],"heat-recovery-steam-generator","duct-burner","selective-catalytic-reduction","heat-rate",{"title":143,"description":144},"Combined-cycle gas turbine (CCGT) — gas turbine plus HRSG and steam turbine","A CCGT plant combines a gas turbine with a steam turbine driven by an HRSG recovering exhaust heat. Plant efficiency reaches 55–62% LHV; HRSG cleanliness is critical.",[146],{"title":147,"url":148},"Wikipedia — Combined cycle power plant","https:\u002F\u002Fen.wikipedia.org\u002Fwiki\u002FCombined_cycle_power_plant","glossary\u002Fcombined-cycle-gas-turbine","Combined-cycle gas turbine","by8SpjeEI8ON6lFVMPJSYZgoB4OvOKZUqmCtbhUvCds",[153,277,355,523],{"id":154,"title":105,"aliases":155,"body":157,"category":131,"description":257,"extension":133,"meta":258,"navigation":135,"path":67,"relatedTerms":259,"seo":264,"sources":267,"stem":274,"term":275,"__hash__":276},"glossary\u002Fglossary\u002Fheat-recovery-steam-generator.md",[68,156],"heat-recovery steam generator",{"type":53,"value":158,"toc":251},[159,167,171,179,183,186,215,219,224,226],[56,160,58,161,163,164,166],{},[60,162,105],{}," recovers heat from the exhaust of a gas turbine to generate steam — the second cycle of a ",[65,165,62],{"href":136}," power plant. HRSGs raise overall plant efficiency from the ~38% of a simple-cycle gas turbine to 55–62% of a modern combined-cycle plant.",[71,168,170],{"id":169},"hrsg-layout","HRSG layout",[56,172,173,174,178],{},"A typical HRSG contains multiple ",[65,175,177],{"href":176},"\u002Fglossary\u002Ffinned-tube-harp-tube","finned-tube"," tube banks arranged in series along the gas-path direction: superheaters, evaporators, economisers, and (on units with SCR) the catalyst layers. Modern HRSGs operate at three pressure levels (HP, IP, LP) to maximise energy recovery from the cooling exhaust gas.",[71,180,182],{"id":181},"fouling","Fouling",[56,184,185],{},"HRSG fouling is generally lighter than coal-fired boiler fouling because gas-turbine exhaust contains far less particulate. The dominant fouling mechanisms are:",[98,187,188,197,203,209],{},[101,189,190,196],{},[60,191,192],{},[65,193,195],{"href":194},"\u002Fglossary\u002Fammonium-bisulphate","Ammonium bisulphate (ABS)"," on units with SCR — slipped ammonia + SO₃ from fuel sulphur condenses on finned tubes",[101,198,199,202],{},[60,200,201],{},"Fine ash deposition"," on finned-tube banks reducing heat transfer",[101,204,205,208],{},[60,206,207],{},"Duct-burner-driven"," particulate on units with supplementary firing",[101,210,211,214],{},[60,212,213],{},"Cold-end corrosion"," below the acid dew point on sulphur-bearing fuels",[71,216,218],{"id":217},"cleaning","Cleaning",[56,220,221,223],{},[65,222,81],{"href":80}," installed across the gas path are increasingly common on HRSG maintenance plans, particularly for keeping SCR catalyst layers and cold-end finned tubes clear of ABS without the need for offline water-wash campaigns.",[71,225,96],{"id":95},[98,227,228,232,237,241,246],{},[101,229,230],{},[65,231,47],{"href":136},[101,233,234],{},[65,235,236],{"href":176},"Finned tube \u002F harp tube",[101,238,239],{},[65,240,111],{"href":110},[101,242,243],{},[65,244,245],{"href":194},"Ammonium bisulphate",[101,247,248],{},[65,249,250],{"href":80},"Sonic horn",{"title":125,"searchDepth":126,"depth":126,"links":252},[253,254,255,256],{"id":169,"depth":126,"text":170},{"id":181,"depth":126,"text":182},{"id":217,"depth":126,"text":218},{"id":95,"depth":126,"text":96},"A Heat Recovery Steam Generator (HRSG) recovers heat from the exhaust of a gas turbine to generate steam — the second cycle of a combined-cycle gas turbine (CCGT) power plant. HRSGs raise overall plant efficiency from the ~38% of a simple-cycle gas turbine to 55–62% of a modern combined-cycle plant.",{},[260,261,139,262,263],"combined-cycle-gas-turbine","finned-tube-harp-tube","ammonium-bisulphate","sonic-horn",{"title":265,"description":266},"Heat Recovery Steam Generator (HRSG) — convert gas-turbine exhaust to steam","An HRSG recovers heat from a gas turbine's exhaust to generate steam, the second cycle of a combined-cycle plant. Finned-tube ash deposition and ABS fouling are the main cleaning concerns.",[268,271],{"title":269,"url":270},"Wikipedia — Heat recovery steam generator","https:\u002F\u002Fen.wikipedia.org\u002Fwiki\u002FHeat_recovery_steam_generator",{"title":272,"url":273},"Combined Cycle Journal — Clean HRSG heat-transfer surfaces","https:\u002F\u002Fwww.ccj-online.com\u002Fclean-heat-transfer-surfaces-inside-and-out-to-keep-hrsgs-at-peak-efficiency\u002F","glossary\u002Fheat-recovery-steam-generator","Heat Recovery Steam Generator","2QpNZZDCPIfd-x3tx7w8wKqru7_s0rVDnW6E_FXNJVw",{"id":278,"title":111,"aliases":279,"body":282,"category":131,"description":345,"extension":133,"meta":346,"navigation":135,"path":110,"relatedTerms":347,"seo":348,"sources":351,"stem":353,"term":111,"__hash__":354},"glossary\u002Fglossary\u002Fduct-burner.md",[280,281],"HRSG duct burner","supplementary firing",{"type":53,"value":283,"toc":340},[284,293,304,308,314,318,324,326],[56,285,58,286,289,290,292],{},[60,287,288],{},"duct burner"," is an auxiliary natural-gas or distillate-oil burner installed in the inlet duct of an ",[65,291,68],{"href":67}," to add heat to the gas-turbine exhaust before it enters the first tube bank. Duct burners are used for:",[98,294,295,298,301],{},[101,296,297],{},"Steam-flow boosting beyond the gas-turbine-only HRSG capacity",[101,299,300],{},"Cogeneration peak shaping where process steam demand exceeds nominal HRSG output",[101,302,303],{},"Cold-start steam-temperature ramp control",[71,305,307],{"id":306},"effect-on-fouling","Effect on fouling",[56,309,310,311,313],{},"Duct-burner firing raises the temperature and changes the gas composition entering the ",[65,312,177],{"href":176}," banks. On natural-gas-only HRSGs, this adds little fouling; on duct burners firing oil or in any unit firing back-up fuel, particulate loading rises substantially and convective-pass fouling accelerates.",[71,315,317],{"id":316},"cleaning-implications","Cleaning implications",[56,319,320,321,323],{},"HRSGs that operate with regular duct-burner firing on liquid fuels usually need more aggressive ",[65,322,263],{"href":80}," coverage on the HRSG harps than gas-only HRSGs do.",[71,325,96],{"id":95},[98,327,328,332,336],{},[101,329,330],{},[65,331,105],{"href":67},[101,333,334],{},[65,335,47],{"href":136},[101,337,338],{},[65,339,236],{"href":176},{"title":125,"searchDepth":126,"depth":126,"links":341},[342,343,344],{"id":306,"depth":126,"text":307},{"id":316,"depth":126,"text":317},{"id":95,"depth":126,"text":96},"A duct burner is an auxiliary natural-gas or distillate-oil burner installed in the inlet duct of an HRSG to add heat to the gas-turbine exhaust before it enters the first tube bank. Duct burners are used for:",{},[138,260,261],{"title":349,"description":350},"Duct burner — supplementary firing in the HRSG gas path","A duct burner is an auxiliary gas burner installed in the HRSG inlet duct to add heat to the gas-turbine exhaust. Used for steam-flow boosting and cogeneration peak shaping.",[352],{"title":269,"url":270},"glossary\u002Fduct-burner","sPgINXKI3DVBZ9j_4oCwpk-x5CSkcumgPsjS_2-O9JA",{"id":356,"title":117,"aliases":357,"body":361,"category":499,"description":500,"extension":133,"meta":501,"navigation":135,"path":116,"relatedTerms":502,"seo":510,"sources":513,"stem":520,"term":521,"__hash__":522},"glossary\u002Fglossary\u002Fselective-catalytic-reduction.md",[358,359,360],"SCR","SCR system","SCR reactor",{"type":53,"value":362,"toc":494},[363,381,385,401,405,408,437,454,456],[56,364,365,367,368,371,372,376,377,380],{},[60,366,117],{}," is the dominant flue-gas NOx-control technology on coal-fired and gas-fired utility boilers, ",[65,369,370],{"href":67},"HRSGs"," in combined-cycle plants, ",[65,373,375],{"href":374},"\u002Fglossary\u002Fwaste-to-energy","waste-to-energy"," and ",[65,378,379],{"href":374},"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.",[71,382,384],{"id":383},"reactor-layout","Reactor layout",[56,386,387,388,392,393,396,397,400],{},"A typical SCR reactor is a vertical or horizontal duct containing 2–4 layers of catalyst modules. Upstream of the catalyst sits the ",[65,389,391],{"href":390},"\u002Fglossary\u002Fammonia-injection-grid","ammonia injection grid (AIG)"," that distributes the ammonia evenly into the flue gas. Most installations operate in the ",[60,394,395],{},"high-dust"," position (between economiser and air heater) where catalyst temperature is around 300–400 °C; ",[60,398,399],{},"tail-end"," SCRs sit downstream of particulate control at lower temperatures, with the trade-off of needing flue-gas reheating.",[71,402,404],{"id":403},"fouling-and-cleaning","Fouling and cleaning",[56,406,407],{},"SCR catalysts foul in two ways:",[98,409,410,428],{},[101,411,412,418,419,376,423,427],{},[60,413,414],{},[65,415,417],{"href":416},"\u002Fglossary\u002Fcatalyst-pluggage","Pluggage"," — fly ash, ",[65,420,422],{"href":421},"\u002Fglossary\u002Fpopcorn-ash","popcorn ash",[65,424,426],{"href":425},"\u002Fglossary\u002Flarge-particle-ash","large-particle ash"," wedge into the catalyst cells, blocking the gas path",[101,429,430,436],{},[60,431,432],{},[65,433,435],{"href":434},"\u002Fglossary\u002Fcatalyst-masking","Masking"," — a thin layer of deposit covers the active sites; gas flow continues but catalytic activity falls",[56,438,439,440,444,445,449,450,453],{},"Both reduce NOx-reduction efficiency, raise ",[65,441,443],{"href":442},"\u002Fglossary\u002Fammonia-slip","ammonia slip",", and shorten catalyst life. Cleaning options include steam ",[65,446,448],{"href":447},"\u002Fglossary\u002Fsteam-sootblower","sootblowers",", ",[65,451,452],{"href":80},"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.",[71,455,96],{"id":95},[98,457,458,464,469,474,479,484,490],{},[101,459,460],{},[65,461,463],{"href":462},"\u002Fglossary\u002Fselective-non-catalytic-reduction","Selective Non-Catalytic Reduction (SNCR)",[101,465,466],{},[65,467,468],{"href":390},"Ammonia injection grid",[101,470,471],{},[65,472,473],{"href":442},"Ammonia slip",[101,475,476],{},[65,477,478],{"href":434},"Catalyst masking",[101,480,481],{},[65,482,483],{"href":416},"Catalyst pluggage",[101,485,486],{},[65,487,489],{"href":488},"\u002Fglossary\u002Fhoneycomb-catalyst","Honeycomb catalyst",[101,491,492],{},[65,493,250],{"href":80},{"title":125,"searchDepth":126,"depth":126,"links":495},[496,497,498],{"id":383,"depth":126,"text":384},{"id":403,"depth":126,"text":404},{"id":95,"depth":126,"text":96},"scr-sncr","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.",{},[503,504,505,506,507,508,509,263],"selective-non-catalytic-reduction","denox","ammonia-injection-grid","ammonia-slip","catalyst-masking","catalyst-pluggage","honeycomb-catalyst",{"title":511,"description":512},"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.",[514,517],{"title":515,"url":516},"Wikipedia — Selective catalytic reduction","https:\u002F\u002Fen.wikipedia.org\u002Fwiki\u002FSelective_catalytic_reduction",{"title":518,"url":519},"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":524,"title":123,"aliases":525,"body":529,"category":635,"description":636,"extension":133,"meta":637,"navigation":135,"path":122,"relatedTerms":638,"seo":642,"sources":645,"stem":649,"term":123,"__hash__":650},"glossary\u002Fglossary\u002Fheat-rate.md",[526,527,528],"boiler heat rate","plant heat rate","heat-rate degradation",{"type":53,"value":530,"toc":630},[531,536,540,543,589,595,599,602,604],[56,532,533,535],{},[60,534,123],{}," is the fuel energy consumed per unit of electrical energy generated, measured in BTU\u002FkWh (US) or kJ\u002FkWh (everywhere else). Lower heat rate equals higher thermodynamic efficiency. Heat rate is the central economic KPI of every coal-fired and gas-fired power plant — a 1% rise in heat rate at sustained load costs the operator 1% more fuel per MWh forever.",[71,537,539],{"id":538},"heat-rate-and-convective-pass-fouling","Heat rate and convective-pass fouling",[56,541,542],{},"Heat rate degrades from many causes. The fouling-driven contribution is normally split between:",[98,544,545,555,564,578],{},[101,546,547,554],{},[60,548,549,553],{},[65,550,552],{"href":551},"\u002Fglossary\u002Feconomiser","Economiser"," fouling"," — feedwater pre-heat falls, steam-cycle efficiency drops",[101,556,557,563],{},[60,558,559,553],{},[65,560,562],{"href":561},"\u002Fglossary\u002Fair-heater","Air heater"," — combustion-air pre-heat falls, boiler efficiency drops",[101,565,566,577],{},[60,567,568,572,573,553],{},[65,569,571],{"href":570},"\u002Fglossary\u002Fsuperheater","Superheater"," \u002F ",[65,574,576],{"href":575},"\u002Fglossary\u002Freheater","reheater"," — outlet temperatures fall, turbine efficiency drops",[101,579,580,588],{},[60,581,582,583,587],{},"Forced ",[65,584,586],{"href":585},"\u002Fglossary\u002Fattemperator-desuperheater","attemperation"," loss"," of margin",[56,590,591,592,594],{},"A typical poorly-maintained coal-fired unit carries 2–4% heat-rate penalty from cumulative fouling. Aggressive cleaning, including ",[65,593,452],{"href":80}," on convective surfaces, can recover 1–3% of that — equivalent to USD 1–5 million annual fuel saving for a 500 MW unit.",[71,596,598],{"id":597},"how-heat-rate-recovery-is-monetised","How heat-rate recovery is monetised",[56,600,601],{},"Heat-rate recovery is the headline business case for sonic-horn retrofits on coal and biomass boilers. The savings flow directly through fuel cost; payback periods of 12–24 months are routinely quoted.",[71,603,96],{"id":95},[98,605,606,612,616,620,626],{},[101,607,608],{},[65,609,611],{"href":610},"\u002Fglossary\u002Fboiler","Boiler",[101,613,614],{},[65,615,552],{"href":551},[101,617,618],{},[65,619,562],{"href":561},[101,621,622],{},[65,623,625],{"href":624},"\u002Fglossary\u002Fconvective-pass-backpass","Convective pass \u002F backpass",[101,627,628],{},[65,629,250],{"href":80},{"title":125,"searchDepth":126,"depth":126,"links":631},[632,633,634],{"id":538,"depth":126,"text":539},{"id":597,"depth":126,"text":598},{"id":95,"depth":126,"text":96},"boiler","Heat rate is the fuel energy consumed per unit of electrical energy generated, measured in BTU\u002FkWh (US) or kJ\u002FkWh (everywhere else). Lower heat rate equals higher thermodynamic efficiency. Heat rate is the central economic KPI of every coal-fired and gas-fired power plant — a 1% rise in heat rate at sustained load costs the operator 1% more fuel per MWh forever.",{},[635,639,640,641,263],"economiser","air-heater","convective-pass-backpass",{"title":643,"description":644},"Heat rate — the fuel-efficiency metric used by every coal and gas plant","Heat rate is the fuel energy required to produce one unit of electrical output, measured in BTU\u002FkWh or kJ\u002FkWh. Fouling on convective surfaces directly degrades heat rate.",[646],{"title":647,"url":648},"Wikipedia — Heat rate (efficiency)","https:\u002F\u002Fen.wikipedia.org\u002Fwiki\u002FHeat_rate_(efficiency)","glossary\u002Fheat-rate","OgQ7351DfpLtBl2D9AWNTCFTk4exqZE2ZLpWrVGyJWA",1782613741964]