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Co-combustion of Animal Waste, Peat, Waste Wood, Forest Residues, and Industrial Sludge in a 50 MWth Circulating Fluidized-Bed Boiler: Ash Transformation, Ash/Deposit Characteristics, and Boiler Failures
Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics. (Thermochemical Energy Conversion Laboratory)
Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics. (Thermochemical Energy Conversion Laboratory)
Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics. (Thermochemical Energy Conversion Laboratory)
2013 (English)In: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 27, no 10, 5617-5627 p.Article in journal (Refereed) Published
Abstract [en]

In strive to lower the energy conversion cost and CO2 net emission, more complex biofuels are used. The combustion of these fuels often creates aggressive and problematic fireside environments in boilers, resulting in reduced availability, which, in turn, may lead to increased usage of fossil fuel in backup boilers. The objective of the present work was to contribute to the efforts of maximizing the availability of a 50 MWth circulating fluidized-bed (CFB) boiler firing complex fuels with high amounts of P, Ca, S, Cl, N, K, and Na. In the present work, ash and deposit samples collected from the flue gas system of a CFB boiler were further analyzed with X-ray powder diffraction, complementing earlier analysis made on the same sample set with scanning electron microscopy equipped with energy-dispersive spectrometry. Thermodynamic calculations were also made. The results clarify details about the ash speciation and transformation as well as effects on boiler operation. A suggestion of a control strategy to minimize corrosion rates in superheaters and SO2 emission to downstream cleaning equipment in full-scale industrial boilers is made. An equation for rough estimation of fuel mix corrosion tendencies is also presented.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2013. Vol. 27, no 10, 5617-5627 p.
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:umu:diva-83910DOI: 10.1021/ef400542hISI: 000326126700004OAI: oai:DiVA.org:umu-83910DiVA: diva2:678122
Funder
Bio4Energy
Available from: 2013-12-11 Created: 2013-12-10 Last updated: 2017-12-06Bibliographically approved
In thesis
1. Co-firing animal waste, sludge, residue wood, peat and forest fuels in a 50MWth CFB boiler: ash transformation, availability and process improvements
Open this publication in new window or tab >>Co-firing animal waste, sludge, residue wood, peat and forest fuels in a 50MWth CFB boiler: ash transformation, availability and process improvements
2014 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

The direct variable costs for heat and electricity production based on solid biomass fuel combustion is approximately 3-5 times lower than the costs in a fossil fuel-oil based boiler in Sweden. In addition waste derived biomass fuels are typically much cheaper than biomass not classified as waste. The introduction of the waste derived fuels; wastewater treatment sludge, demolition wood, and animal waste in a 50MWth circulating fluidized bed (CFB) biomass boiler located in Perstorp, Sweden, led to rapid deposit buildup in superheaters, heavy ash accumulation in economizers and failing boiler tubes and vortex finders that forced frequent boiler shutdowns. This in turn increased the use of expensive oil (fossil fuel) in backup boilers and the CO2 footprint of the on-site energy conversion system. This work aims to increase the general mechanistic understanding of combustion systems using complex fuels, and includes: A mapping of the boiler failure and preventive maintenance statistics; elemental composition analysis of ash, deposits and fuel fractions; flue-gas composition measurements; chemical speciation analysis; an attempt to describe the overall ash transformation reactions and mass balance throughout the combustion process. Scanning electron microscope (SEM) equipped with energy dispersive X-ray spectroscopy (EDS) was used to analyze the elemental composition of ash and deposits. The SEM-EDS results were used together with data from X-ray powder diffraction (XRD) analysis, thermodynamic phase data, and equilibrium calculations in an attempt to quantify the crystalline phases and the overall ash transformation of the process. Based on the findings concerning ash transformation and the failure statistics, it has been possible to identify generic key parameters regarding boiler design and process parameters, enabling major improvements of the CFB boiler availability, a lower overall energy conversion cost and a reduced CO2 footprint.

Abstract [sv]

Den direkta rörliga kostnaden för värme-och elproduktion baserad på fast biobränsle är ungefär 3-5 gånger lägre än kostnaden för fossiloljebaserad produktion. Avfallsklassade fasta biobränslen är vidare oftast betydligt billigare än fasta biobränslen som inte är klassade som avfall. Införandet av de avfallsklassade bränslena; reningsslam, rivningsvirke, och animaliskt avfall i en 50MWth cirkulerande fluidiserad bädd (CFB) -panna, ledde till kraftig beläggningstillväxt i överhettare och ackumulering av aska i ekonomisers, samt haveri av panntuber och centrumrör i cyklonerna, som tvingade fram frekventa pannstopp. Detta ökade i sin tur användningen aveldningsolja (fossilt bränsle) i reservkrafts-pannor vilket resulterade i ett större CO2 utsläpp och en högre kostnad för energiomvandlingen på siten. Detta arbete syftar till att öka den allmänna mekanistiska förståelsen av förbränningssystem som använder komplexa bränslen, och omfattar; haveri- och underhållsstatistik, elementarsammansättningsanalys av aska, beläggningar och bränslefraktioner, rökgasens sammansättning, kemisk specificering av askor och beläggningar, ett försök att beskriva de övergripande askomvandlingsreaktionerna, samt en massbalans för förbränningsprocessen. Svepelektronmikroskop (SEM) utrustat med energidispersiv röntgenspektroskopi (EDS) användes för att analysera den elementära sammansättningen av aska och beläggningar. SEM-EDS-resultaten användes tillsammans med pulverröntgendiffraktionsanalys (XRD), termodynamiska fasdata, och jämviktsberäkningar i ett försök att kvantifiera de kristallina faserna och de övergripande askomvandlingsreaktionerna i processen. Baserat på resultaten rörande askomvandling och haveristatistik, har det varit möjligt att identifiera generiska nyckelparametrar gällande panndesign och processparametrar, som möjliggjort stora förbättringar av CFB pannans tillgänglighet, en lägre totalkostnad för energiomvandlingen på siten samt ett minskat CO2-utsläpp.

Place, publisher, year, edition, pages
Umeå: Umeå universitet, 2014. 60 p.
Keyword
Co-combustion, animal waste, peat, waste wood, forest residues, industrial sludge, limestone, CFB boiler, ash transformation, corrosion, erosion, ash and deposit characteristics, deposit buildup, boiler failures, availability, sulfation, boiler design, boiler conversion, waste derived fuels, large scale, Samförbränning, animaliskt avfall, torv, returträ, skogsbränsle, reningsslam, askomvandling, korrotion, erosion, ask- och beläggnings-karaktäristik, beläggningstillväxt, tillgänglighet, sulfatisering, panndesign, pannkonvertering, avfallsderiverade bränslen, storskalig
National Category
Inorganic Chemistry Chemical Process Engineering Corrosion Engineering
Identifiers
urn:nbn:se:umu:diva-114736 (URN)978-91-7601-060-0 (ISBN)
Presentation
2014-06-10, Naturvetarhuset, N300, Umeå universitet, Umeå, 13:00 (English)
Supervisors
Funder
Bio4Energy
Available from: 2016-01-28 Created: 2016-01-27 Last updated: 2016-02-17Bibliographically approved

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