Ash Deposition on Heat Transfer Tubes during Combustion of Demolition Wood

Åmand, Lars-Erik; Leckner, Bo G; Eskilsson, David; Tullin, Claes

doi:10.1021/ef0503919

Cited by 34 publications

(30 citation statements)

References 9 publications

(11 reference statements)

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“…Common uses of FTIR and Raman spectroscopy in polymer science center around functional group determination via comparison between peaks of interest with databases. The area under a characteristic region can be translated to a molar quantity using a Beer’s Law type analysis . This information can then be used to determine the number-average degree of polymerization M̅ n , degree of functionalization, as well as the presence of contaminants and the morphology of polymer crystals. − In addition to the conventional bulk sampling techniques, IR has been coupled with atomic force microscopy (AFM).…”

Section: Polymer Strandsmentioning

confidence: 99%

Molecular Characterization of Polymer Networks

et al. 2021

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Polymer networks are complex systems consisting of molecular components. Whereas the properties of the individual components are typically well understood by most chemists, translating that chemical insight into polymer networks themselves is limited by the statistical and poorly defined nature of network structures. As a result, it is challenging, if not currently impossible, to extrapolate from the molecular behavior of components to the full range of performance and properties of the entire polymer network. Polymer networks therefore present an unrealized, important, and interdisciplinary opportunity to exert molecular-level, chemical control on material macroscopic properties. A barrier to sophisticated molecular approaches to polymer networks is that the techniques for characterizing the molecular structure of networks are often unfamiliar to many scientists. Here, we present a critical overview of the current characterization techniques available to understand the relation between the molecular properties and the resulting performance and behavior of polymer networks, in the absence of added fillers. We highlight the methods available to characterize the chemistry and molecular-level properties of individual polymer strands and junctions, the gelation process by which strands form networks, the structure of the resulting network, and the dynamics and mechanics of the final material. The purpose is not to serve as a detailed manual for conducting these measurements but rather to unify the underlying principles, point out remaining challenges, and provide a concise overview by which chemists can plan characterization strategies that suit their research objectives. Because polymer networks cannot often be sufficiently characterized with a single method, strategic combinations of multiple techniques are typically required for their molecular characterization.

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Section: Polymer Strandsmentioning

confidence: 99%

Molecular Characterization of Polymer Networks

et al. 2021

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“…For ash deposit formation in the post-combustion region, the effect of ash particle shape on ash deposition could be alleviated for the ash particles with the melting history due to the increased spherical shape after melting [14]. Amand et al [15] reported the experimental studies of ash deposit formation for a demolition wood combustion in a 12-MWth circulating fluidized-bed (CFB) boiler. They found that KCl was responsible for the serious ash deposition problem while the contamination of Zn (zinc) without chlorine cannot cause a serious ash deposition problem.…”

Section: Introductionmentioning

confidence: 99%

Understanding the effects of oxyfuel combustion and furnace scale on biomass ash deposition

Yang

Szuhánszki

Tian

et al. 2019

Fuel

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Recycled wood oxyfuel combustion is attractive for the advantages of reusing the waste bioenergy and reducing the carbon emissions. However, the changes in the fuel properties and combustion conditions can lead to uncertainties in the ash deposition. In addition, the understanding of the differences in the ash deposition between the pilot-scale and full-scale furnaces is very limited. We have performed ash deposition experiments on a 250 kW pilot-scale furnace for recycled wood air and oxyfuel combustion along with the EI Cerrejon coal combustion as a reference. A CFD-based ash deposition model, which uses the excess energy based particle sticking model, has been developed and the predictions are in qualitative agreement with the measurement data. The results suggest that, besides furnace temperature, the aerodynamics and ash physicochemical properties dictate the ash deposition. The recycled wood has a much higher deposition rate than the coal in the pilot-scale furnace; however, the biomass can numerically have a lower deposition rate under high velocities close to the full-scale boilers. This is mainly due to the biomass having a much lower sticking efficiency since it has high calcium and silicon concentrations and low potassium concentration. Although the effect of oxyfuel combustion is small and within the experimental uncertainties, it is found that oxyfuel combustion can affect the particle impaction and sticking behaviours depending on the fly ash properties and these effects occur in different ways in the pilot-scale and full-scale conditions. Great care should be taken to perform the transfer of the deposition observations from the pilot scale to the full scale and this is because the furnace scale has an effect on the selective deposition behaviour. In this paper a relationship between the fly ash properties (ash composition, size, etc.) and ash deposition for the woody biomass has been proposed.

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“…During combustion, zinc is released and readily available to form gaseous products in the flue gas, and previous studies indicate that zinc readily forms zinc chloride, which melts at 318 °C . Findings of ZnCl 2 in fireside deposits in municipal solid waste (MSW) boilers have led to the general belief that ZnCl 2 might play a role in the corrosion of heat-transfer tubes in these boilers owing to its low melting temperature and high corrosivity when molten. − …”

Section: Introductionmentioning

confidence: 99%

Effects of Reduced Bed Temperature in Laboratory- and Full-Scale Fluidized-Bed Boilers: Particle, Deposit, and Ash Chemistry

Jones

Niklasson²,

Lindberg

et al. 2013

Energy Fuels

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This study focuses on how the temperature of the bed in a waste-fired fluidized-bed boiler affects the chemical composition of ash and deposits. The aim was to reduce the concentration of corrosive elements in the convection pass, which can lead to both less frequent soot blowing intervals and extended superheater lifetimes. Complementary laboratory-scale tests were carried out in a single-pellet reactor to study online alkali and Zn emissions during temperature changes, using an ICP-MS instrument. The full-scale study was based on full-scale experiments at a plant consisting of two 20 MWth fluidized-bed boilers firing a mixture of municipal solid waste and industrial waste. The boilers are normally operated at bed temperatures of about 870 °C. This normal operation was compared in this work to a test case in which the bed temperature was reduced below 720 °C by altering the air staging and flue gas recycling. The experimental work included collecting samples of fuel, ash, and particles under the two different sets of operating conditions. Furthermore, deposits on temperature-controlled probes were sampled upstream of the superheaters. By reducing the bed temperature, the sand consumption of the plant could be reduced by roughly 25%. The measurements showed that the amount of submicrometer particles decreased and the fouling rate on deposit probes was reduced by about 20%. The measured concentration of HCl in the flue gas increased as the bed temperature was reduced. This might be a consequence of the reduced formation of alkali chlorides. In addition, results from the laboratory-scale tests indicated a trend of reduced alkali emissions from the fluidized bed with reduced temperature, and thermodynamic equilibrium calculations confirmed the trends.

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Ash Deposition on Heat Transfer Tubes during Combustion of Demolition Wood

Cited by 34 publications

References 9 publications

Molecular Characterization of Polymer Networks

Molecular Characterization of Polymer Networks

Understanding the effects of oxyfuel combustion and furnace scale on biomass ash deposition

Effects of Reduced Bed Temperature in Laboratory- and Full-Scale Fluidized-Bed Boilers: Particle, Deposit, and Ash Chemistry

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