Investigation on ash deposit formation during the co-firing of coal with agricultural residues in a large-scale laboratory furnace

Wang, Gongliang; Pinto, Tiago; Costa, Mário

doi:10.1016/j.fuel.2013.09.084

Cited by 46 publications

(17 citation statements)

References 18 publications

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“…For woody biomass, potassium and chlorine play a significant contribution in causing serious ash deposit issues due to the low melting temperatures of the potassium related minerals to generate a sticky deposit surface and increase the particle stickiness itself under the pulverised combustion conditions. In addition, high concentrations of potassium in the deposits can increases the degree of sintering [43], which deteriorates the deposit removal. For the recycled woody biomass with a low concentration of potassium used in this study, the ash deposition should not be serious as both SiO2 and CaO are less reactive and refractive.…”

Section: From Pilot-scale To Full-scalementioning

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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Section: From Pilot-scale To Full-scalementioning

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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“…Therefore, plentiful efforts have been attempted to probe the functional mechanism of alkali metals on these ash-related problems. 15−17 Wang and Pinto 18 described an experimental investigation on ash deposit formation during the cofiring of coal with agricultural residues. They found that a higher level of Na in the deposit composition led to a higher degree of adherence to surfaces.…”

Section: Introductionmentioning

confidence: 99%

Release and Transformation of Sodium during Pyrolysis of Zhundong Coals

Wang

et al. 2014

Energy Fuels

109

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Zhundong coalfield is one of the superhuge coalfields newly discovered in Xinjiang Autonomous Region of China. While many studies on alkali metals in coal/biomass have been reported previously, few efforts were conducted on Zhundong coals which are characterized by a high content of sodium. It is challenging to explore the ash deposition problems related to Zhundong coals directly using existing findings on the behavior of alkali metals. The occurrence mode and transformation of alkali metals during thermal conversion of Zhundong coals could be quite different. Specific investigation on sodium transformation during pyrolysis of Zhundong coals will make a contribution to our understanding on the fate and behavior of alkali metals involved in high-sodium coals. Here, the release and transformation fundamentals of sodium during pyrolysis of two Zhundong bituminous coals were investigated using an experimental approach of sequential chemical extraction. The sodium volatilization and evolution of occurrence modes in chars of Zhundong coal were probed in a laboratory-scale reactor. The occurrence of alkali metals in Zhundong coals greatly differs from those in other coals of China. Water-soluble sodium is the predominant chemical form in Zhundong coals. Most of the water-soluble sodium is released into gas phase as a volatile during pyrolysis and part of the remainder is converted into an insoluble form, but the release of sodium is not always synchronous with volatility. The release behavior of sodium demonstrates a nonmonotonic variation with the particle size of the coal while the effect of particle size includes many factors resulting in the challenge of demonstrating its individual contribution to sodium release. The duration time has an insignificant effect on volatile release and sodium transformation at low temperature, while it has an obvious influence at high temperature or in the initial stage of pyrolysis. With the extension of duration time at high temperature, no more sodium is obviously released from the residual chars of Zhundong coal but more water-soluble sodium will still transform into insoluble form. During the devolatilization of Zhundong coals under CO 2 atmosphere, the release of sodium and its conversion into insoluble form will be inhibited compared to that under N 2 condition.

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“…In particular, high Cl content in SEH coal can cause corrosion in the boiler heating surfaces [8], which are primarily caused by gaseous corrosive media [9], including HCl (g), NaCl (g), and Cl 2 (g) [10]. Wang et al [11] observed a high degree of particle deposition on the boiler surfaces when coal is co-fired with agriculture residues due to their high sodium contents. Tyni et al [12] concluded that the formation of low-melting phases in ash is caused by the high alkali metal contents.…”

Section: Introductionmentioning

confidence: 99%

Effects of temperature and additives on ash transformation and melting of high-alkali-chlorine coal

et al. 2020

THERM SCI

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The high contents of sodium and chlorine in Shaerhu (SEH) coal aggravate severe slagging ash deposition and corrosion in boilers. Adding proper additives is an effective way to reduce slagging ash deposition and corrosion. Based on the experimental study, this paper investigated the effect of combustion temperature, types of additives, and its amount on the ash transformation and melting of high sodium chloride (NaCl) SEH coal. The ash melting characteristics, elemental compositions and mineral compositions of the ash produced under different conditions were characterized. Results showed that the contents of calcium (Ca), magnesium (Mg), and sulfur (S) in the coal ash varied slightly with the temperature increasing. Chlorine (Cl) and sodium (Na) released rapidly from coal at 550 to 815?C and 550 to 700?C, respectively. At 1050?C, calcium silicate (Ca2SiO4) was observed as the main component of the ash. The addition of different additives had no significant effect on chlorine and sodium capture. The addition of silicon species lowered the ash fusion temperatures (AFTs), while the aluminum (Al) had an opposite effect. To prevent the furnace from slagging, a high aluminum additive is proposed to be adopted.

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Investigation on ash deposit formation during the co-firing of coal with agricultural residues in a large-scale laboratory furnace

Cited by 46 publications

References 18 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

Release and Transformation of Sodium during Pyrolysis of Zhundong Coals

Effects of temperature and additives on ash transformation and melting of high-alkali-chlorine coal

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