Comparison of Ash from PF and CFB Boilers and Behaviour of Ash in Ash Fields

Arro, H.; Pihu, T.; Prikk, A.; Rootamm, R.; Konist, Alar

doi:10.1007/978-3-642-02682-9_164

Cited by 11 publications

(6 citation statements)

References 2 publications

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“…All of the studies noted above were performed during oxy-fuel combustion in PC boilers, while relatively little research has been devoted to studying ash deposition in CFB boilers during oxy-fuel combustion. There will be some differences in the ash generated by CFB and PC boilers because of the different combustion temperatures, combustion modes, and feed coal particle sizes between the two boiler types, all of which directly affect ash formation . Wu et al investigated characteristics of the ash produced by a 100 kW th pilot-scale CFB boiler during oxy-fuel combustion incorporating a limestone sorbent but paid more attention to the desulfurization mechanism and combustion process rather than fly ash deposition.…”

Section: Introductionmentioning

confidence: 99%

Fly Ash Deposition during Oxy-fuel Combustion in a Bench-Scale Fluidized-Bed Combustor

et al. 2013

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Ash deposition on heat-exchanger surfaces in boiler systems can cause numerous problems, including slagging, fouling, and corrosion. These deleterious processes can be compounded if the boiler combustion process is changed from air to oxy-fuel. In this paper, fly ash deposition characteristics under both air and oxy-fuel combustion conditions were investigated using a bench-scale fluidized-bed combustor (FBC) based on measurements of ash deposition rates via a temperature-controlled probe. Three different combustion atmospheres were studied, and results demonstrated that, under similar combustion temperature profiles and equivalent fluidization velocities, the deposition rate increased when transitioning from combustion atmospheres consisting of 21% O 2 /79% CO 2 to air to 30% O 2 /70% CO 2 . To determine the primary factors associated with the observed variations in deposition rates, the chemical compositions and micromorphologies of ash and fly ash deposits were analyzed by inductively coupled plasma−atomic emission spectrometry (ICP−AES) and scanning electron microscopy (SEM). Particulate matter with aerodynamic diameters less than 10 μm (PM 10 ) was measured by an electrical low-pressure impactor (ELPI), and the particle size distributions (PSDs) and carbon contents of the collected filter ash were also ascertained. The results indicate that the higher deposition propensity associated with a 30% O 2 /70% CO 2 atmosphere can be largely attributed to a wider PSD rather than any changes in the chemical compositions of the fly ash or deposited ash, in which there are no obvious differences between air and oxy-fuel combustion. In addition, the slightly higher concentration of fine particles produced under this atmosphere also promotes the deposition of fly ash.

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Section: Introductionmentioning

confidence: 99%

Fly Ash Deposition during Oxy-fuel Combustion in a Bench-Scale Fluidized-Bed Combustor

et al. 2013

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“…Different composition of ash fractions has significant influence on the potential application of ashes as secondary raw materials. In earlier decades, PF ashes have been extensively studied [2,[9][10][11][12], and used for the production of construction materials and cement [13], in road construction [14] and for liming of acid soils [15]. Potential industrial scale applications and possible environmental aspects of CFB ashes are, however, virtually unexplored.…”

Section: Introductionmentioning

confidence: 99%

Composition of Oil Shale Ashes From Pulverized Firing and Circulating Fluidized-Bed Boiler in Narva Thermal Power Plants, Estonia

Bityukova¹,

Mõtlep²,

Kirsimäe³

2010

Oil Shale

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The composition of oil shale ashes from pulverized firing (PF) and circulating fluidized-bed boiler combustion (CFB) systems at the Eesti and the Balti Thermal Power Plants was studied by means of quantitative X-ray diffraction, chemical analysis and scanning electron microscopy. The composition of ash varies systematically in the boiler gas pass, depending on the firing technology. PF ashes are dominated by free lime, whose content decreases from the furnace to the last fields of electrostatic precipitators. Same trends can be observed within residual fraction (i.e. mineral phases remaining in firing process) and Ca-silicates. Anhydrite, on the other hand, concentrates into the end of the gas pass. CFB ash shows more complex variations, and on several occasion the changes in certain phases are opposite to variations in respective PF ashes. Comparison of the phase composition of ashes from the same type of boilers in the Eesti and Balti TPP show remarkable differences in Ca-silicate phases. To our best knowledge, earlier mineralogical studies have not addressed compositional variations of ashes from two separate power plants. These differences are probably related to the heterogeneity of oil shale fuel, not so much to combustion temperature.

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“…For example, in PC-NID samples, most of the elements exhibited different distribution patterns from those in CFBC samples. This was attributed to the differences in the temperatures and operating conditions -the temperatures in the PC boiler were significantly higher than in CFBC boilers, 1350-1450 °C and about 850 °C, respectively [44]. Additionally, the grain size of the fuel was somewhat different.…”

Section: Resultsmentioning

confidence: 98%

Comparison of the ecotoxic properties of oil shale industry by-products to those of coal ash

Järvik¹,

Konist²,

Lees³

et al. 2022

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The European Union (EU) presented a uniform List of Waste (LoW) in 2000 and last updated the technical guidance in 2018. The respective local regulations for the classification of waste in Estonia were set in 2015. Due to the changes in the regulations, it was necessary to review the properties of solid wastes generated in Estonian oil shale industry in light of hazardous properties. Therefore, the properties of the produced ash streams were analysed and the obtained results were compared to those for coal for being in accordance with common practices. The main objective of the paper was to answer the question whether the properties of oil shale (OS) are comparable to those of coal as coal and its combustion residues were not considered hazardous waste in Europe, but the respective counterparts of oil shale were. The EU guidelines suggest the use of calculations based on trace element concentrations for the classification of hazardous property (HP) 14 -ecotoxic. Therefore, an extensive study was conducted to investigate the hazardous properties of all the solid residues from power plants operating on oil shale and shale oil production facilities. This paper describes one part of it -the trace element compositions of the major ash streams produced in the Estonian oil shale industry and focuses on their comparison with data available for coal ash samples. The findings of the study showed that, similarly to coal, oil shale ash (OSA) should not be considered as ecotoxic due to the low concentrations of trace elements. It was found that the investigated oil shale ash samples exhibited a very similar composition and properties to those of coal, and as a result of a larger study, from the beginning of 2020, oil shale ash and other oil shale thermal treatment residues are not classified as hazardous waste in Estonia, thereby initiating policy changes that affect most areas of the economy.

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Comparison of Ash from PF and CFB Boilers and Behaviour of Ash in Ash Fields

Cited by 11 publications

References 2 publications

Fly Ash Deposition during Oxy-fuel Combustion in a Bench-Scale Fluidized-Bed Combustor

Fly Ash Deposition during Oxy-fuel Combustion in a Bench-Scale Fluidized-Bed Combustor

Composition of Oil Shale Ashes From Pulverized Firing and Circulating Fluidized-Bed Boiler in Narva Thermal Power Plants, Estonia

Comparison of the ecotoxic properties of oil shale industry by-products to those of coal ash

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