Effect of Fuel Type and Deposition Surface Temperature on the Growth and Structure of an Ash Deposit Collected during Co-firing of Coal with Sewage Sludge and Sawdust<sup>†</sup>

Kupka, Tomasz; Krzysztof, Zajac; Weber, Roman

doi:10.1021/ef800976y

Cited by 36 publications

(21 citation statements)

References 10 publications

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“…This does not greatly change the geometry of the deposit surface and affect the particle impaction and deposition behaviour. Kupka et al [34] experimentally found a linear ash deposition rate in the early stage, which also supports the 'steady state' assumption in this study.…”

Section: Case Set-up and Uncertainty Analysissupporting

confidence: 91%

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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Section: Case Set-up and Uncertainty Analysissupporting

confidence: 91%

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

Yang

Szuhánszki

Tian

et al. 2019

Fuel

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“…Figure 4 shows a typical diagram of process temperature-base-acid ratio, as an indi-cator of slagging/fouling for the cofiring of Kakanj brown coal with spruce sawdust. This corresponds to the explanation given by Raask [11]. Above this temperature, ash deposition of the coal-sawdust mixtures was accentuated; ash deposits were melted and then hardened.…”

Section: Investigated Of Slagging and Fouling-related Problems On Labsupporting

confidence: 85%

“…They do not represent a threat to the stability of operation or the efficiency of the boiler. Only slight change in NO x emissions can be noticed with the change of fuel, and there is no clear correlation between the influence of adding biomass to the emission of NO x , which is consistent with experimental research described above, as well as with many findings in the world on the phenomenon of the influence of biomass on emissions of NO x , see [9][10][11]. The base-acid ratio for the ash deposits is given in fig.…”

Section: Slagging/fouling Assessment Based On the Trial Runsupporting

confidence: 83%

Co-firing Bosnian coals with woody biomass: Experimental studies on a laboratory-scale furnace and 110 MWe power unit

et al. 2012

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This paper presents the findings of research into cofiring two Bosnian cola types, brown coal and lignite, with woody biomass, in this case spruce sawdust. The aim of the research was to find the optimal blend of coal and sawdust that may be substituted for 100% coal in large coal-fired power stations in Bosnia and Herzegovina. Two groups of experimental tests were performed in this study: laboratory testing of co-firing and trial runs on a large-scale plant based on the laboratory research results. A laboratory experiment was carried out in an electrically heated and entrained pulverized-fuel flow furnace. Coal-sawdust blends of 93:7% by weight and 80:20% by weight were tested. Co-firing trials were conducted over a range of the following process variables: process temperature, excess air ratio and air distribution. Neither of the two coal-sawdust blends used produced any significant ash-related problems provided the blend volume was 7% by weight sawdust and the process temperature did not exceed 1250ºC. It was observed that in addition to the nitrogen content in the co-fired blend, the volatile content and particle size distribution of the mixture also influenced the level of NOx emissions. The brown coal-sawdust blend generated a further reduction of SO2 due to the higher sulphur capture rate than for coal alone. Based on and following the laboratory research findings, a trial run was carried out in a large-scale utility - the Kakanj power station, Unit 5 (110 MWe), using two mixtures; one in which 5%/wt and one in which 7%/wt of brown coal was replaced with sawdust. Compared to a reference firing process with 100% coal, these co-firing trials produced a more intensive redistribution of the alkaline components in the slag in the melting chamber, with a consequential beneficial effect on the deposition of ash on the superheater surfaces of the boiler. The outcome of the tests confirms the feasibility of using 7%wt of sawdust in combination with coal without risk to the efficiency of the unit, its combustion process and with the benefits of emissions reductions. Furthermore, they show that no modification to the existing coal transport system and boiler equipment is necessary to achieve this outcome

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“…Zhou et al [5,6] used a digital imaging system protected by cooling water and compressed air to monitor the growth of ash deposition. Additionally, surface temperature plays an important role in ash deposition [7][8][9][10]. Zhou et al [11] found that the temperature of the deposition surface had a significant effect on the deposition rate and morphology, and that the deposition thickness increased as the surface temperature decreased.…”

Section: Introductionmentioning

confidence: 99%

Measuring surface temperatures of different types of fly ash samples using a CCD camera

et al. 2022

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In this work, an optical emission-based two-color method was experimentally investigated for the measurement of surface temperatures of different types of fly ash samples using a CCD camera. A heating system consisting of a Hencken flat-flame burner, a narrow piece of stainless steel wire mesh to separate the flame and the ash samples to be studied, and a thermocouple to record the temperature, was used to heat fly ash samples. A color camera equipped with a tri-band filter was used to capture radiation images. Fly ash samples collected from three kinds of coal-fired boilers were heated and imaged at different temperatures. The chemical compositions, elements, and particle size distributions were analyzed. The emissivity ratios of the wavelengths corresponding to the R and G optical channels and permitted by the tri-band filter were experimentally determined. A two-color method was subsequently used to calculate the average surface temperatures with relative errors within ? 2 % in the experiments, and an uncertainty analysis was conducted. Surface temperature distributions were also calculated and presented. The results demonstrate that the emission-based two-color method can be used to determine reliable average surface temperatures and surface temperature distributions when the radiation emitted from the ash samples is obviously greater than the ambient light. The results also show that the method has a lower limit of temperature measurement, which will lessen with the use of larger apertures and a higher radiation capacity of the ash samples to be studied.

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Effect of Fuel Type and Deposition Surface Temperature on the Growth and Structure of an Ash Deposit Collected during Co-firing of Coal with Sewage Sludge and Sawdust^†

Cited by 36 publications

References 10 publications

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

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

Co-firing Bosnian coals with woody biomass: Experimental studies on a laboratory-scale furnace and 110 MWe power unit

Measuring surface temperatures of different types of fly ash samples using a CCD camera

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Effect of Fuel Type and Deposition Surface Temperature on the Growth and Structure of an Ash Deposit Collected during Co-firing of Coal with Sewage Sludge and Sawdust†

Cited by 36 publications

References 10 publications

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

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

Co-firing Bosnian coals with woody biomass: Experimental studies on a laboratory-scale furnace and 110 MWe power unit

Measuring surface temperatures of different types of fly ash samples using a CCD camera

Contact Info

Product

Resources

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Effect of Fuel Type and Deposition Surface Temperature on the Growth and Structure of an Ash Deposit Collected during Co-firing of Coal with Sewage Sludge and Sawdust^†