84
Infrasound soot cleaning VGB PowerTech 8 l 2013
Authors
Kurzfassung
Online Rußblasen mit Infraschall
Das Unternehmen Infrafone wendet seit über 30 Jahren Infraschalltechnik als Rußblastechnik an. Die von Infrafone eingesetzte Rußblastechnik steigert die Effizienz sowie die Verfügbarkeit und Reisezeit von großtechnischen und auf Schiffen installierten Dampferzeugern. Im vorliegenden Beitrag wird die von Infrafone eingesetzte Infraschalltechnik sowie deren Wirkungsweise als Rußbläser dargestellt und beschrieben. Es schließt sich ein Vergleich bzw. eine Abgrenzung zur HochtonReinigungstechnik an. Abschließend werden anhand von Fallstudien Ergebnisse und Einsparpotenziale durch InfrafoneRußblastechnik aufgezeigt. l
Ph.D. Èric Torra i FernàndezDevelopment EngineerM.Sc. Martin EllebroDirector EngineeringInfrafone ABStockholm/Sweden
Introduction
The paper is to provide a deeper insight and better understanding of infrasound cleaning. The authors try to summarise the most important technical aspects of infra-sound cleaning of heat exchange surfaces.Infrafone, with headquarters in Stock-holm, Sweden, is the oldest company in the field of soot cleaning using infrasound, with more than 30 years of experience. The technical development has resulted in a very powerful product and acoustic model-ling software that is unique. Infrafone has installed infrasound cleaning equipment on 65 waste-to-energy and bio-fuel boil-ers (most of them during the last 8 years), 11 coal-fired boilers and 900 ships. In power plants and heating plants, the technology is mainly used for cost-efficient on-line cleaning of soot (fly-ash) off econ-omisers, tubular air preheaters, catalysts, ducts, electrostatic precipitators (ESP), and Ljungstrom air preheaters. Cleaning of superheaters is possible if the soot build up is not sticky. On marine cruise ships and cargo ships the technology is used for on-line cleaning of exhaust gas economisers, ducts, and oil fired boilers.
Infrasound
The frequency of sound is related to the wavelength λ according to the expression λ= c/f. The wavelength is the distance between two points of the same phase in consecutive cycles of a wave. The speed of sound in air is approximately 340 m/s at room temperature. Hence high frequen-cies of sound have short wavelengths and low frequencies of sound have long wave-lengths. The infrasound cleaners are using infra-sound as an acoustic cleaning method. The infrasound is the sound produced at very low frequencies, typically less than 20 Hz. At room temperature a sound wave with 20 Hz will have a wavelength of around 17 m. However, a sound wave of 250 Hz will only have a wavelength of 1.36 m. From a cleaning point of view, low frequen-cy sound has several advantages. One is that infrasound is omnidirectional, which means it spreads in all directions. Further-more, sound absorption in tube bundles is very low at these frequencies. This means that the sound produced by infrasound cleaners can reach all parts of a tube bun-dles in for example an economiser, which in many cases means a lower and more stable differential pressure compared to steam soot blowing.
Online soot cleaning using infrasoundÈric Torra i Fernàndez and Martin Ellebro
A third property of infrasound that is ad-vantageous from a soot cleaning point of view is the high degree of turbulence that infrasound creates in the flue gas stream. The typical flue gas velocities at heat ex-changers in power plants are low and the flue gas flow has a low degree of turbu-lence. This results in areas with a very low flue gas velocity near the surface of the tube bundles. Soot particles accumulate in these areas with low gas velocity and grow to large deposits with time. For efficient re-moval of the soot particles attached to the heat exchangers or other surfaces with in-frasound, the particle displacement of the flue gas has to be maximised. The particle displacement is the magnitude that is relat-ed to the distance of the movement of the particles when excited by a sound wave. The particle displacement is inversely pro-portional to the frequency. Thus, low fre-quency sound as the infrasound results in large particle displacement. The oscillation with large particle displacement creates a high degree of turbulence in the flue gas and this high degree of turbulence around the tubes of a heat exchanger helps to keep the tube surface clean ( F i g u r e 1 and 2 ). Infrafone’s infrasound cleaner is producing sound just for a few seconds every few min-utes. This means that the turbulence pro-duced by the sound wave occurs typically only during 1 to 2 seconds. The system is a continuous and dry on-line cleaning method since it operates every few min-utes. The infrasound cleaners cannot clean surfaces where the soot build up is sticky or hard, i.e. they keep clean surfaces already cleaned. In summary, the main advantages of using infrasound for cleaning are:
– Large wavelengths, – Low sound absorption, – Omni-directionality, – Large particle displacement,
high turbulence, – Dry cleaning method, – Non-abrasive, and – Continuous cleaning method.
Acoustic modelling
Infrafone has developed an acoustic mod-elling software that is used for simulating the sound propagation in great detail. An acoustic model is designed for each boiler where an infrasound cleaner is to be in-stalled. All the dimensions of the boiler and the heat exchangers are introduced in this model. Flue gas temperature distribu-tion and flue gas velocity are also entered since these are related to wavelength of the
VGB
Pow
erTe
ch -
Aut
oren
exem
plar
- ©
201
3
>>> VGB DIGITAL <<<VGB PowerTech - Autorenexemplar - © 2013
85
VGB PowerTech 8 l 2013 Infrasound soot cleaning
sound and attenuation of sound energy in the tube bundles. By using the acoustic model it is possible to choose the optimal installation position, the optimal size, and number of sonic cleaners as well as the fre-quency of sound in order to obtain the re-quired acoustic power in the desired clean-ing area.The model is always confirmed by carrying out sound pressure level measurements in-side the boiler ( F i g u r e 3 ).
Infrafone’s infrasound cleaners
The infrasound cleaner consists of an at-tachment socket, a diffuser, a resonance tube, a resonance chamber and a pulsator. The attachment socket is welded directly to the flue gas duct. The resonance tube can be designed in different shapes in order to fit in the installation position and sur-roundings (F i g u r e 4 and 5 ). The frequency of the infrasound can be fine-tuned by a moveable plate inside the resonance chamber. The total length of the sonic cleaner can be adjusted in order to obtain the desired frequency simply by
moving the resonance plate along the reso-nance chamber.The pulsator is placed on the top of the resonance plate and is connected to a com-pressed air source. The compressed air should have a pressure of 6 to 8 bar(g). The pulsator produces the air pulses that gen-erate infrasound. It consists of a cylinder, a piston, and a titanium spring. The axial mechanical moving system is very simple and can be easily maintained. There are no rotational mechanisms involved and no electric or electronic instrumentation is required.A unique feature of the infrasound cleaner allows the pulsator to auto-regulate itself by the positive feedback produced by the reflected acoustic waves in the resonance tube. In this way, the maximum acous-tic power is always generated by the in-frasound cleaner independently of load changes and changes in flue gas tempera-ture in the boiler system. Without posi-tive feedback, a change of some degrees in temperature inside the boiler means a decrease in acoustic power emitted by the infrasound cleaner.
The acoustic power delivered is propor-tional to the square of the cross section area of the open end of a sonic cleaner. Inf-rafone has several infrasound cleaner sizes. The attachment socket’s diameter of the biggest and most powerful sonic cleaner is 1,500 mm. The infrasound cleaner is very powerful, so to prevent any movement of the sonic cleaner, reinforcements around the at-tachment to the boiler wall is generally recommended. Infrafone has designed a vibration damper that is tuned in for each sonic cleaner, so vibrations transmitted to the boiler are kept low. Infrafone also has an automatic control system that mini-mises the operating time of the infrasound cleaners, which is also crucial for obtain-ing high cleaning effect and low vibration levels.
Comparison with sonic horns
Sound at the audible frequency range is used by sonic horns which typically use sound frequencies of around a few hun-dred Hz, i.e. the area which they can keep
Laminar flow
Fig. 1. Laminar flow.
Turbulent flow
Fig. 2. Turbulent flow.
Cleaning effect
Fig. 3. Acoustic model.
Attachmentsocket
Pulsator
Resonancechamber
Resonance tube
Diffuser
Fig. 4. Infrasonic cleaner.
VGB
Pow
erTe
ch -
Aut
oren
exem
plar
- ©
201
3
>>> VGB DIGITAL <<<VGB PowerTech - Autorenexemplar - © 2013
86
Infrasound soot cleaning VGB PowerTech 8 l 2013
clean is small due to the short acoustic wavelengths.Furthermore, the sound frequencies used by sonic horns are not omnidirectional and the sound absorption is much higher for this sound frequency range than for in-frasound. For this reason, sonic horns are producing a local cleaning effect close to the installation position. Due to the limited cleaning range, several sonic horns must be installed. However, just one, or in some cases two, infrasound cleaners are usually installed to cover a large cleaning area.Furthermore there is a limit for how large cross-section at the cleaning area that can be cleaned by sonic horns due to the long distance from the installation locations at the walls to the middle parts of e.g. an economizer.
Potential savings from using infrasound cleaning
– Reduced operational and maintenance costs
– Savings on operation of steam soot blow-ing and shot cleaning
– Saved steam can be used for increased production or reduced fuel consumption
– Savings on replacement of tubes in heat exchangers through extended tube life-time
Stable Δp, which means: – Less outages, increased availability,
higher energy production
– Less outages, more burned waste – Less outages, improved working environ-
ment – Reduced fan power consumption – Lower risk for high flue gas velocity in lo-
cal areas – Savings on replacement of tubes in heat
exchangers through extended tube life-time
– Cleaner electrostatic precipitator, cata-lyst
– Compliance with environmental regula-tions
– Savings on replacement of catalyst ele-ments through extended element life-time
Case studies
E.ON Norrköping P14, Sweden, 75 MWth, boiler equipped with circulating fluidised bed combustion (CFB)Commissioning: 2006Cleaning area: Vertical economiser ( F i g -u r e 6 )Fuel: Industrial/household wastePerformance:
– Steam soot blowing reduced from 3 to 4 times/day to once/week
– Increased production of electricity – Less wear on economiser tube bundles – Lower and more stable differential pres-
sure, Δp than with steam soot blowing operating 3 times/day.
SYSAV boiler 1&2 Malmö, Sweden, 2 x 29 MWth, grate firingCommissioning: 2008 and 2009Cleaning area: vertical evaporator and economiserFuel: Industrial/household wastePerformance:
– Shot cleaning of the economiser (flue gas temp 420 to 170 °C) has been turned off
– Lower and more stable Δp over the econ-omiser than with shot cleaning
– The exhaust gas outlet temperature from the evaporator is lower and stable
– The soot deposits in the high-tempera-ture area (flue gas temperature 680 to 600 °C) of the evaporator are now softer and it takes longer time to build up
VAFAB Köping, Sweden, 12 MWth, grate firingCommissioning: 2009Cleaning area: Vertical evaporator and economiserFuel: Industrial/household wastePerformance evaporator:
– The steam soot blowers at flue gas tem-perature range 470 down to 200 °C have been turned off. Previous operation was 3 times/day
– Δp is lower than with steam soot blowing 3 times/day
Fig. 5. Two infrasonic cleaners on top of economisers.
ECO 6
ECO 5
ECO 4
ECO 3
ECO 2
ECO 1
CONV
CONV
SH1
SH1
SH2
SH2
850 °C 350 °C
710 °C 175 °C
INFRAFONESONIC CLEANER
Fig. 6. Norrköping power plant.
VGB
Pow
erTe
ch -
Aut
oren
exem
plar
- ©
201
3
>>> VGB DIGITAL <<<VGB PowerTech - Autorenexemplar - © 2013
87
VGB PowerTech 8 l 2013 Infrasound soot cleaning
Performance economiser: – With the previously installed air cleaning
lances flue gas temp increased rapidly – With infrasound technology installed,
air cleaning lances were turned off and the Δp and outlet temperature are now on a stable low level the full season
E.ON Mora, Sweden, 8 MWth, grate firingCommissioning: 2010Cleaning area: Vertical economiserFuel: Industrial/household wastePerformance:
– The boiler has been in operation for two years (since early 2011) without any need for manual cleaning of the econo-miser
– The Δp is still low and stable – The differential temperature is still high
and stable – No other soot cleaning equipment in-
stalled
Mississippi Power Plant Daniel, USA, 2 x 535 MWel
Commissioning: 1999, 2000, 2001, 2005Cleaning area: 4 x Ljungstrom air preheat-ers size 24 ½ and 2 x economiserFuel: Powder river basin coal (with low heat value (8800 BTU/lb.) and high ash content)Performance:
– Since installing the infrasound clean-ers, the use of steam soot blowers for the Ljungstrom air preheaters and econo-mizers for both coal-fired boilers has been eliminated.
EVO Offenbach, Germany, 2 x 110 MWel
Commissioning: 1993, 1994, 1995, 1996Cleaning area: 2 tubular air preheaters, 2 economisers, 2 superheatersFuel: Coal Performance:
– No soot-cleaning device was installed from the beginning. Deposits reduced the heat transfer considerably. Since installing infrasound cleaners the clean-ing results in both boilers are very good. Load changes caused by clogging are no
longer a problem and the thermal effi-ciency has increased by 1.5 %.
Vattenfall Hamburg Tiefstack, Germany, 2 x 150 MWel Commissioning: 1997, 1999Cleaning area: 2 x SCR honeycomb catalyst on two identical boilersFuel: Hard coalPerformance:
– Since installation in the end of the 1990s, the pressure drop over both cata-lysts is being kept stable the whole op-erating season. Infrasound cleaning is the only soot cleaning equipment for the catalysts.
Summary
Infrasound cleaning is a cost-efficient way of keeping low-temperature areas clean, such as economisers, air preheaters, cata-lysts etc. The technique drastically elimi-nates or reduces the need for other clean-ing methods such as steam soot blowing, shot cleaning, air soot blowing, detonation cleaning, and manual cleaning. The return of investment is typically short thanks to e.g. higher availability, increased produc-tion or reduced fuel consumption. l
VGB-Abkürzungskatalog für die KraftwerkstechnikVGB Abbreviationcatalogue for power plant technologyAusgabe/Edition 2012 – VGB-S-891-00-2012-06-DE-EN DIN A4, 642 Sei ten, Print oder CD, Preis für VGB-Mit glie der € 130,–, für Nicht mit glie der € 190,–,
+ Ver sand kos ten und MwSt. Print + CD, Preis für VGB-Mit glie der € 260,–, für Nicht mit glie der € 380,–, + Ver sand kos ten und MwSt.
DIN A4, 642 pages, Print or CD, Pri ce for VGB mem bers € 130.–, for non mem bers € 190.–, + VAT, ship ping and hand ling. Print + CD, Pri ce for VGB mem bers € 260.–, for non mem bers € 380.–, + VAT, ship ping and hand ling.
Diese Richtlinie wurde vom VGBArbeitskreis „Anlagenkennzeichnung und Dokumentation“ erarbeitet, in dem Betreiber und Instandhalter sowie Planer und Hersteller von Kraftwerken gemeinsam tätig sind. Zu den Aufgaben dieses Arbeitskreises gehören u.a. die Erstellung und Pflege von fach- bezogenen und kraftwerkstypspezifischen Richtlinien sowie der Kennbuchstaben für Kraftwerks- systeme. Für die laufende Pflege dieser Richtlinie ist der VGB-Arbeitskreis „Anlagenkennzeichnung und Dokumentation“ zuständig.Mit dieser 4. Ausgabe wurde die bisher nur in deutscher Sprache vorliegende VGB-Richtlinie redak tionell vollständig überarbeitet und in die englische Sprache übertragen. Für die Anwendung von Abkürzungen im englischen Sprachraum wurden entsprechende Abkürzungsregeln benutzt, die teilweise von den deutschen Festlegungen abweichen.Zur Neuaufnahme von Abkürzungen steht auf der Web-Seite des VGB ein Formular zur Verfügung.This guideline was prepared by the VGB Working Panel „Reference Designation and Plant Docu-mentation“, which is attended by power plant operators and maintenance contractors as well as designers and suppliers of power plants. The tasks of this working panel include the preparation and maintenance of discipline-specific and power plant type-specific guidelines as well as the letter codes for power plant systems (system key). The VGB Working Panel „Reference Designation and Plant Documentation“ is responsible for updating this guideline on an ongoing basis.This 4th issue is editorial amended and translated from German into English. For the application of abbreviations in English-speaking countries, corresponding abbreviations rules have been used. These are partly different from the German rules.To submit new abbreviations, please use the form on the VGB web page.
VGB-Standard
VGB-Abkürzungskatalog für die KraftwerkstechnikVGB Abbreviation- catalogue for power plant technology
VGB-S-891-00-2012-06-DE-EN
VGB PowerTech Service GmbHVerlag technisch-wissenschaftlicher Schriften
Klinkestraße 27-31 45136 Essen P.O. Box 10 39 32 Germany
Fon: +49 201 8128-200 Fax: +49 201 8128-329 Mail: [email protected]
VGB-Standard
VGB
Pow
erTe
ch -
Aut
oren
exem
plar
- ©
201
3
>>> VGB DIGITAL <<<VGB PowerTech - Autorenexemplar - © 2013
International Journal for Electricity and Heat Generation
Please copy >>> fill in and return by mail or fax
Yes, I would like order a subscription of VGB PowerTech.The current price is Euro 275.– plus postage and VAT.Unless terminated with a notice period of one month to the end of the year, this subscription will be extended for a further year in each case.
Return by fax to
VGB PowerTech Service GmbHFax No. +49 201 8128-302
or access our on-line shop at www.vgb.org | MEDIA | SHOP.
Name, First Name
Street
Postal Code City Country
Phone/Fax
Date 1st Signature
Cancellation: This order may be cancelled within 14 days. A notice must be sent to to VGB PowerTech Service GmbH within this period. The deadline will be observed by due mailing. I agree to the terms with my 2nd signature.
Date 2nd Signature
Vo lu me 89/2009 · ISSN 1435-3199
K 43600
In ter na tio nal Edi ti on
Focus: Power Plants in Competiton
New Power Plant Projects of EskomQuality Assurance for New Power PlantsAdvantages of Flexible Thermal Generation
Market Overview for Imported Coal
In ter na tio nal Jour nalfor Elec tri ci ty and Heat Ge ne ra ti on
Pub li ca ti on ofVGB Po wer Tech e.V.www.vgb.org
Vo lu me 89/2009 · ISSN 1435-3199
K 43600
In ter na tio nal Edi ti on
Focus: VGB Congress
Power Plants 2009
Report on the Activities
of VGB PowerTech
2008/2009
EDF Group Reduces
its Carbon Footprint
Optimising Wind Farm
Maintenance
Concept for Solar
Hybrid Power Plants
Qualifying Power Plant Operators
In ter na tio nal Jour nal
for Elec tri ci ty and Heat Ge ne ra ti on
Pub li ca ti on of
VGB Po wer Tech e.V.
www.vgb.org
Con gress Is sue
Vo lu me 89/2009 · ISSN 1435-3199
K 43600
In ter na tio nal Edi ti on
Focus: Furnaces, Steam Generators and Steam TurbinesUSC 700 °C Power Technology
Ultra-low NOx Combustion
Replacement Strategy of a Superheater StageEconomic Post-combustion Carbon Capture Processes
In ter na tio nal Jour nalfor Elec tri ci ty and Heat Ge ne ra ti onPub li ca ti on ofVGB Po wer Tech e.V.www.vgb.org
Vo lu me 90/2010 · ISSN 1435-3199
K 43600
In ter na tio nal Edi ti on
Fo cus: Pro Quality
The Pro-quality
Approach
Quality in the
Construction
of New Power Plants
Quality Monitoring of
Steam Turbine Sets
Supply of Technical
Documentations
In ter na tio nal Jour nal
for Elec tri ci ty and Heat Ge ne ra ti on
Pub li ca ti on of
VGB Po wer Tech e.V.
www.vgb.org
V
00634 K
9913-5341 NSSI · 5002/58 emulo
International Edition
Schwerpunktthema:
Erneuerbare Energien
Hydrogen Pathways
and Scenarios
Kopswerk II –
Prevailing Conditions
and Design
Arklow Bank
Offshore Wind Park
The EU-Water
Framework Directive
International Journal
for Electricity and Heat Generation
Publication of
VGB PowerTech e.V.
www.vgb.org
Vo lu me 89/2009 · ISSN 1435-3199
K 43600
In ter na tio nal Edi ti on
Focus: Maintenance
of Power Plants
Concepts of
IGCC Power Plants
Assessment of
Generators for
Wind Power Plants
Technical Data for
Power Plants
Oxidation Properties
of Turbine Oils
In ter na tio nal Jour nal
for Elec tri ci ty and Heat Ge ne ra ti on
Pub li ca ti on of
VGB Po wer Tech e.V.
www.vgb.org
VGB PowerTech-DVDMo re than 12,000 digitalised pages with data and expertise
(incl. se arch func ti on for all do cu ments)
Ple ase fill in and re turn by mail or fax
I would li ke to or der the VGB Po wer Tech-DVD 1990 to 2012 (sin gle user li cen se).
Eu ro 950.–* (Subs cri ber of VGB Po wer Tech Jour nal 1
Eu ro 1950.–* (Non-subs cri ber of VGB Po wer Tech Jour nal 2 Plus postage, Germany Euro 7.50 and VAT Net work li cen se (cor po ra te li cen se), VGB mem bers’ edi ti on (In fo Ex pert) and edu ca ti on li cen se on re quest
(pho ne: +49 201 8128-200).* Plus VAT.Annual update 1 Euro 150.–; 2 Euro 350.– The update has to be ordered annually.
Re turn by fax or in business envelope with window to VGB Po wer Tech Ser vice GmbHFax No. +49 201 8128-329In fo Ex pert
Na me, First Na me
Street
Pos tal Co de Ci ty Count ry
Pho ne/Fax
Da te 1st Sig na tu re
Can cel la ti on: This or der may be can cel led wi thin 14 days. A no ti ce must be sent to to VGB Po wer Tech Ser vice GmbH wi thin this pe ri od. The deadline will be observed by due mailing. I ag ree to the terms with my 2nd sig na tu re.
Da te 2nd Sig na tu re
Top Related