Searching for a robust strategy for minimizing alkali chlorides in fluidized bed boilers during burning of high SRF-energy-share fuel

Bajamundi, Cyril; Vainikka, Pasi; Hedman, Merja; Silvennoinen, Jaani; Heinanen, Teemu; Taipale, Raili; Konttinen, Jukka

doi:10.1016/j.fuel.2015.03.087

Cited by 10 publications

(5 citation statements)

References 46 publications

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“…The gaseous oxidation of SO 2 to SO 3 is often mentioned to be a required step in order to achieve a satisfying sulfation rate. − Wu et al point out the temperature window enabling the formation of SO 3 : 900 °C < T < 1100 °C via homogeneous oxidation (kinetically limited at lower temperatures and thermodynamically restricted at higher temperatures). The sulfation has to take place in a sufficient distance to metal surfaces in the superheater in order to ensure that the formed HCl does not interact with the deposit . The generation of a sufficient amount of SO 3 in the flue gas can be achieved by adding additives (e.g., ammonium sulfate, ferric sulfate, etc.)…”

Section: Introductionmentioning

confidence: 99%

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Online Corrosion Measurements in Combination with Deposit and Aerosol Analysis during the Co-firing of Straw with Coal in Electrically Heated, Small-Scale Pulverized Fuel and Circulating Fluidized Bed Systems

et al. 2018

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A measurement campaign has been conducted both in a pilot-scale pulverized fuel and in a pilot-scale circulating fluidized bed test rig to evaluate the behavior of two different online corrosion sensors during the co-combustion of straw with bituminous coal. The online corrosion sensors based on the linear polarization method were equipped with material rings of the alloy10CrMo9-10 and air-cooled to a material temperature of 530 °C (PF) and 560 °C (CFB). They were implemented at a flue gas temperature of approximately 750–800 °C in both test rigs to simulate superheater tubes. The derived signals were compared with flue gas measurements (O2, CO2, SO2, and HCl) as well as selected fine particle measurements and deposit sampling during co-firing tests of 0, 10, 25, 40, 60, and 100% straw with coal on an energy basis. Slight deviations between the fuels tested in the different test rigs were observed. Main differences were measured in the coal ash composition and chlorine content of the straw. Online corrosion sensors reacted quickly to changes in the blend composition. While no enhanced corrosion was detected during the co-combustion of 10% and 25% straw, both sensors identified possible corrosive processes on the metal surface during the 60% straw case. The detected signal change could be correlated to an increased share of chlorine in the fine particles (in the PF and the CFB test rigs) and deposits (only in the CFB tests). Interestingly, a smaller signal change was detected during the 40% straw case in the PF combustion, in contrast to a larger signal gradient during the 40% case in the CFB tests. Two reasons could be identified for this behavior: On the one hand, the sensor used in the PF tests showed a lower sensitivity due to a different design of the sensor head. On the other hand, a significant amount of chlorine was detected in the aerosolic particles in the CFB tests in contrast to no chlorine in the PF experiments during this case. The known interaction mechanisms of alkali mitigation during combustion of difficult fuels (sulfation and embedding in alumino-silicates), which lead to a chlorine reduction in the fine particles, were investigated thoroughly. It was found that sulfation might be more pronounced under conditions typical of CFB systems.

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Section: Introductionmentioning

confidence: 99%

“…The sulfation has to take place in a sufficient distance to metal surfaces in the superheater in order to ensure that the formed HCl does not interact with the deposit. 30 The generation of a sufficient amount of SO 3 in the flue gas can be achieved by adding additives (e.g., ammonium sulfate, ferric sulfate, etc.) into the boiler.…”

Section: ■ Introductionmentioning

confidence: 99%

Online Corrosion Measurements in Combination with Deposit and Aerosol Analysis during the Co-firing of Straw with Coal in Electrically Heated, Small-Scale Pulverized Fuel and Circulating Fluidized Bed Systems

et al. 2018

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“…Potentially this could be useful in fundamental investigations to characterize co-combustion of coal and biomass fuels containing sodium and potassium, respectively. The mitigation of alkali-related problems such as high-temperature corrosion, slagging, and fouling, that are due to the increased use of biomass fuel of different quality regarding alkali and chlorine, 33,34 demands methods that has the possibility of detecting KCl and NaCl, as demonstrated for this set-up.…”

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confidence: 99%

Laser-Induced Photofragmentation Fluorescence Imaging of Alkali Compounds in Flames

et al. 2016

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Laser-induced photofragmentation fluorescence has been investigated for the imaging of alkali compounds in premixed laminar methane-air flames. An ArF excimer laser, providing pulses of wavelength 193 nm, was used to photodissociate KCl, KOH, and NaCl molecules in the post-flame region and fluorescence from the excited atomic alkali fragment was detected. Fluorescence emission spectra showed distinct lines of the alkali atoms allowing for efficient background filtering. Temperature data from Rayleigh scattering measurements together with simulations of potassium chemistry presented in literature allowed for conclusions on the relative contributions of potassium species KOH and KCl to the detected signal. Experimental approaches for separate measurements of these components are discussed. Signal power dependence and calculated fractions of dissociated molecules indicate the saturation of the photolysis process, independent on absorption cross-section, under the experimental conditions. Quantitative KCl concentrations up to 30 parts per million (ppm) were evaluated from the fluorescence data and showed good agreement with results from ultraviolet absorption measurements. Detection limits for KCl photofragmentation fluorescence imaging of 0.5 and 1.0 ppm were determined for averaged and single-shot data, respectively. Moreover, simultaneous imaging of KCl and NaCl was demonstrated using a stereoscope with filters. The results indicate that the photofragmentation method can be employed for detailed studies of alkali chemistry in laboratory flames for validation of chemical kinetic mechanisms crucial for efficient biomass fuel utilization.

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“…86 MJ kg À1 although oxygen content is higher in this study due to the lower ash content. In Finland, Bajamundi et al (2015) analyzed two SRF solid fuels to be used as co-fuel in fluidized bed boilers, with an elemental composition similar to the bulky waste analyzed in this study, and with an oxygen content (27.5-29.1 wt.%) alike that found in this study (35.20-37.93 wt.%).…”

Section: Waste Classificationmentioning

confidence: 64%

Evaluation of the potential of different high calorific waste fractions for the preparation of solid recovered fuels

et al. 2016

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Solid recovered fuels constitute a valuable alternative for the management of those non-hazardous waste fractions that cannot be recycled. The main purpose of this research is to assess the suitability of three different wastes from the landfill of the local waste management company (COGERSA), to be used as solid recovered fuels in a cement kiln near their facilities. The wastes analyzed were: End of life vehicles waste, packaging and bulky wastes. The study was carried out in two different periods of the year: November 2013 and April 2014. In order to characterize and classify these wastes as solid recovered fuels, they were separated into homogeneous fractions in order to determine different element components, such as plastics, cellulosic materials, packagings or textile compounds, and the elemental analysis (including chlorine content), heavy metal content and the heating value of each fraction were determined. The lower heating value of the waste fractions on wet basis varies between 10 MJ kg(-1) and 42 MJ kg(-1). One of the packaging wastes presents a very high chlorine content (6.3 wt.%) due to the presence of polyvinylchloride from pipe fragments, being the other wastes below the established limits. Most of the wastes analyzed meet the heavy metals restrictions, except the fine fraction of the end of life vehicles waste. In addition, none of the wastes exceed the mercury limit content, which is one of the parameters considered for the solid recovered fuels classification. A comparison among the experimental higher heating values and empirical models that predict the heating value from the elemental analysis data was carried out. Finally, from the three wastes measured, the fine fraction of the end of life vehicles waste was discarded for its use as solid recovered fuels due to the lower heating value and its high heavy metals content. From the point of view of the heating value, the end of life vehicles waste was the most suitable residue with a lower heating value of 35.89 MJ kg(-1), followed by the packaging waste and the bulky waste, respectively. When mixing the wastes studied a global waste was obtained, whose classification as solid recovered fuels was NCV 1 Cl 3 Hg 3. From the empirical models used for calculating higher heating value from elemental content, Scheurer-Kestner was the model that best fit the experimental data corresponding to the wastes collected in November 2013, whereas Chang equation was the most approximate to the experimental heating values for April 2014 fractions. This difference is due to higher chlorine content of the second batch of wastes, since Chang equation is the only one that incorporates the chlorine content.

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Searching for a robust strategy for minimizing alkali chlorides in fluidized bed boilers during burning of high SRF-energy-share fuel

Cited by 10 publications

References 46 publications

Online Corrosion Measurements in Combination with Deposit and Aerosol Analysis during the Co-firing of Straw with Coal in Electrically Heated, Small-Scale Pulverized Fuel and Circulating Fluidized Bed Systems

Online Corrosion Measurements in Combination with Deposit and Aerosol Analysis during the Co-firing of Straw with Coal in Electrically Heated, Small-Scale Pulverized Fuel and Circulating Fluidized Bed Systems

Laser-Induced Photofragmentation Fluorescence Imaging of Alkali Compounds in Flames

Evaluation of the potential of different high calorific waste fractions for the preparation of solid recovered fuels

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