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Initiation and Propagation of Stress-Assisted Corrosion

Initiation and Propagation of Stress-Assisted Corrosion

Loading in 2 Seconds... Technical considerations on biomass fired boilers for heat and power - Research in CHEC, DTU. Weigang Lin CHEC Research C enter Department of Chemical and Biochemical Engineering Technical University of Denmark. Outline.Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.Weigang Lin CHEC Research Center Department of Chemical and Biochemical Engineering Technical University of Denmark Brief introduction of DTU Chemical Engineering and CHEC research center Problems in biomass fired boilers Fundamental studies Deposit Corrosion Aerosol emissions Counter measures Gasification Concluding remarks Problems in biomass fired boilers Fundamental studies Deposit Corrosion Aerosol emissions Counter measures Gasification Concluding remarks Corrosion Aerosol emissions Counter measures Gasification Lyngby Combustion and Harmful Emission Control (CHEC) New and Fundamental knowledge on High Temperature Processes Formation and Reduction of Harmful Components and Particulates Catalysis and Chemical Product Design To assist enterprises and governmental organisations High Temperature Processes Formation and Reduction of Harmful Components and Particulates Catalysis and Chemical Product Design Formation and Reduction of Harmful Components and Particulates Catalysis and Chemical Product Design To train engineers and researchers To catalyze international cooperation Merger Risø New pilot Acidification Debate Time 1990 2000 2010 Coal Fluid Bed SO2 NOx Bio-mass Alkali Corrosion-depositions Models Cement Waste Products Coatings Catalysis Gasification Pharma Minerals Systematic development of experimental methods and modeling tools Focus on Reaction Engineering, Transport processes New MSc Programme Started in China and power A full MSc programme on chemical and Biochemical Engineering, with focus on Biomass, is launched in Beijing, China. The programme offers Danish and Chinese students the possibility of obtaining a dual degree from DTU and the University of Chinese Academy of Sciences (UCAS). PM2.5 KCl Corrosion Ash deposition Bed agglomeration SCR deactivation SO and power 2 (g) KCl/K2SO4 nucleation/ heterogeneous condensation SO2 emission HCl emission HCl (g) KCl/KOH (g) SO2 KCl / KOH Cl in straw KCl (g) S in straw SO2 K2SO4 (g) (+ HCl) K2SO4 (g) K in straw K2SO4 (g) Cl in bottom ash S in bottom ash K-Ca-silicates in bottom ash Layered structure:  cm  > 0.7 100% KCl Haslev and Slagelse CHPs (probe), 1994 Rudkøbing CHP (probe + mature), 1995 Masnedø CHP (probe + mature), 1996-1997, 2000-2002 Maribo-Sakskøbing CHP (mature), 2001, 2004 Probe deposits: short term [~ 2-10 hours] exposure of cooled probes (finger print chemistry) Mature deposits: In-boiler, long term [~ 103 hours] exposed deposits (real chemistry, including chemical reaction sintering) Rudkøbing CHP (probe + mature), 1995 Masnedø CHP (probe + mature), 1996-1997, 2000-2002 Maribo-Sakskøbing CHP (mature), 2001, 2004 Probe deposits: short term [~ 2-10 hours] exposure of cooled probes (finger print chemistry) Mature deposits: In-boiler, long term [~ 103 hours] exposed deposits (real chemistry, including chemical reaction sintering) Maribo-Sakskøbing boiler Rudkøbing boiler Haslev boiler Slagelse boiler Boiler wall and power Probe Superheaters CCD camera Flue gas flow New, advanced probe: Heat transfer Mass of deposits Temperatures (flue gas and probe) Video – visible and IR Heat transfer Mass of deposits Temperatures (flue gas and probe) Video – visible and IR After 3 hr Metal temperature From van Loo and Koopejan (2002). mg/Nm3 Ca-P dAero, nm mg/Nm3 S dAero, nm Aerosol sampling: before SCR unit, T=350oC Deposit probe measurement: location B, T=780±20 oC Deposit probe measurement: location A, T=1275±50 oC Deposit probe measurement: location B, T=780±20 oC Deposit probe measurement: location A, T=1275±50 oC Damø et al. (2014), Wu et al. (2013) Significant reduction of submicron aerosol formation with addition of coal fly ash Similar effect for the addition of 6 ton/h and 3 ton/h coal fly ash Similar effect for the addition of 6 ton/h and 3 ton/h coal fly ash Damø et al. (2014) Boiler SCR ESP + Boiler ESP SCR Boiler modification Co-combustion + Additives Pretreatment 1:1 1:10 Low Temperature Circulating Fluid Bed (LT-CFB) Cl, K and S cause severe operational problems in biomass fired boilers for heat and power production, especially deposition, corrosion, agglomeration and aerosol emissions Co-firing biomass and coal can significantly reduce the operational problems Application of right additives may be the other solution Biomass to power through gasification Co-firing biomass and coal can significantly reduce the operational problems Application of right additives may be the other solution Biomass to power through gasification For SlideServe users



The George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA 30332-0405School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, GA 30332-0245preet.singh@mse.gatech.eduThe George W. Woodruff School of Mechanical Engineering, and School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, GA 30332-0245Corresponding author.Industrial boilers experience bulbous cracks in carbon steel water-wall tubes and other water-touched surfaces. Because these cracks are blunt and different from sharp fatigue cracks, they are generally referred to as stress-assisted corrosion (SAC) cracks. The performance of carbon steels in industrial boilers strongly depends on the formation and stability of the magnetite film on the waterside surface. To understand the mechanism for SAC crack initiation and propagation, slow strain rate tests were conducted in a recirculation autoclave under industrial boiler water conditions. The dissolved oxygen in the water was maintained from a negligible amount (5ppb) to 3ppm. The SAC crack initiation and propagation mechanism involves magnetite film damage and requires the presence of dissolved oxygen in the water. Increasing the test temperature accelerates the process. A mechanism for SAC cracking is proposed, and interrupted slow strain rate tests were carried out to validate this mechanism. Temperature and dissolved oxygen in boiler water are important factors in initiation and propagation of stress assisted corrosion cracks. SAC in boilers can be controlled by controlling the dissolved oxygen levels around 5ppb.(a) Sharp corrosion-fatigue (CF) cracks, typically found on carbon steel tubes in high-pressure utility boilers and (b) blunt SAC cracks with bulbous appearance, typically found in industrial boilersSchematic of the recirculation loop and autoclave system used to simulate boiler environmentsEffect of SSRT temperature on (a) crack density and (b) crack velocity for SA-210 carbon steel samples in pure water with dissolved oxygen either 3ppm (denoted “With O2”) or only ∼5ppb (denoted “Without O2”)Surface cracks on a SSRT sample tested in 3ppm oxygenated water at 300°CEffect of test temperature on the ductility of SA-210 carbon steel samplesEffect of dissolved oxygen on the ductility of SA-210 carbon steel samplesThe temperature dependence on crack velocity of SA-210 carbon steel with dissolved oxygen of 5ppmISSRT to simulate boiler shutdown/start-up cycles. Micrographs show crack morphology at different times during the test.Schematic showing proposed mechanism of initiation and propagation of SAC cracksValidation tests conducted in oxygenated water (5ppm) at 300°C: (a) test without interruption showing sharp crack and (b) ISSRT showing bulbous crack formation under simulated boiler operation with shutdown/start-up cycles Some tools below are only available to our subscribers or users with an online account.Download citation file: Customize your page view by dragging and repositioning the boxes below. © 2017 ASME The American Society of Mechanical Engineers Sorry! You do not have access to this content. For assistance or to subscribe, please contact us: Sign in or create your free personal ASME account. This will give you the ability to save search results, receive TOC alerts, RSS feeds, and more. Sign into or create your free personal account





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