Modeling of ferric sulfate decomposition and sulfation of potassium chloride during grate‐firing of biomass

Wu, Hao; Jespersen, Jacob Boll; Frandsen, Flemming; Glarborg, Peter; Aho, Martti; Paakkinen, Kari; Taipale, Raili

doi:10.1002/aic.14174

Cited by 12 publications

(22 citation statements)

References 47 publications

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“…39 The experimental results of ammonium sulfate and aluminum sulfate are shown in Figure 4, along with the results of ferric sulfate obtained previously. 39 It can be seen that the correlation between ln(k) and 1/T generally shows a high linearity, indicating that the volumetric reaction model (eq 3) can satisfactorily describe the decomposition of the sulfates. The activation energy (E) and the pre-exponential factor (A) derived from Figure 4 are listed in Table 2.…”

Section: Model Development and Simulationmentioning

confidence: 94%

“…42 The yields of SO 2 and SO 3 from the decomposition of ammonium sulfate and aluminum sulfate in the laboratory-scale tube reactor are shown in Figure 5, along with the results of ferric sulfate from previous work. 39 It can be seen that the yield of SO 2 from aluminum sulfate decomposition is low, and within the uncertainty, it is independent of the decomposition temperature in the temperature range of 700−900°C. Therefore, in the modeling, we assume that 15% sulfur in aluminum sulfate is released as SO 2 under boiler conditions and the remaining 85% is released as SO 3 .…”

Section: Model Development and Simulationmentioning

confidence: 98%

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Modeling the Use of Sulfate Additives for Potassium Chloride Destruction in Biomass Combustion

Pedersen

Jespersen

et al. 2013

Energy Fuels

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Potassium chloride, KCl, formed from biomass combustion may lead to ash deposition and corrosion problems in boilers. Sulfates are effective additives for converting KCl to the less harmful K 2 SO 4 and HCl. In the present study, the rate constants for decomposition of ammonium sulfate and aluminum sulfate were obtained from experiments in a fast heating rate thermogravimetric analyzer. The yields of SO 2 and SO 3 from the decomposition were investigated in a tube reactor at 600−900°C , revealing a constant distribution of about 15% SO 2 and 85% SO 3 from aluminum sulfate decomposition and a temperaturedependent distribution of SO 2 and SO 3 from ammonium sulfate decomposition. On the basis of these data as well as earlier results, a detailed chemical kinetic model for sulfation of KCl by a range of sulfate additives was established. Modeling results were compared to biomass combustion experiments in a bubbling fluidized-bed reactor using ammonium sulfate, aluminum sulfate, and ferric sulfate as additives. The simulation results for ammonium sulfate and ferric sulfate addition compared favorably to the experiments. The predictions for aluminum sulfate addition were only partly in agreement with the experimental results, implying a need for further investigations. Predictions for the effectiveness of the sulfur-based additives indicate that ferric sulfate and ammonium sulfate have similar effectiveness at temperatures ranging from approximately 850 to 900°C, whereas ferric sulfate is more efficient at higher temperatures and ammonium sulfate is more effective at lower temperatures.

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Section: Model Development and Simulationmentioning

confidence: 94%

Section: Model Development and Simulationmentioning

confidence: 98%

Modeling the Use of Sulfate Additives for Potassium Chloride Destruction in Biomass Combustion

Pedersen

Jespersen

et al. 2013

Energy Fuels

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“…The transformation behaviors of alkali metals among various modes of occurrence in the coal need to be further elucidated. There are quite a few studies on the behaviors of alkali metals during the heat treatment of biomass in which alkali metal is mainly potassium. , Nevertheless, the physical and chemical characteristics of coals are remarkably different from biomass. Specifically, Zhundong coals could be greatly different from other existing coals or biomass in the amount, occurrence mode, and release mechanism of alkali metals and specific study on the transformation features of alkali metals involved in utilization of Zhundong coals is necessary.…”

Section: Introductionmentioning

confidence: 99%

Release and Transformation of Sodium during Pyrolysis of Zhundong Coals

Wang

et al. 2014

Energy Fuels

111

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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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“…A positive effect of SO 2 has been reported when SO 2 sulphates KCl aerosol particles in the vapour phase, before they condense on vulnerable metallic surfaces (i.e., ‘in‐flight’ sulphation) . However, heterogeneous (‘in‐deposit’) sulphation is considered in the following discussion because this corresponds to the experimental conditions in the present study.…”

Section: Discussionmentioning

confidence: 81%

Effect of flue gas composition on deposit induced high temperature corrosion under laboratory conditions mimicking biomass firing. Part II: Exposures in SO₂ containing atmospheres

Okoro

Kiamehr

Montgomery

et al. 2016

Materials & Corrosion

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In biomass fired power plants, the fast corrosion of superheaters is facilitated by the presence of corrosive flue gas species, for example, SO2, which are released during combustion. To understand the role of the gas species on the corrosion process, comparative laboratory exposures of deposit (KCl)‐coated and deposit‐free austenitic stainless steel (TP 347H FG) samples to gas mixtures containing SO2 was carried out, under conditions relevant to biomass‐firing. Exposures were conducted isothermally at 560 °C for 72 h, in oxidizing‐sulphidizing, and oxidizing‐sulphidizing‐chlorinating gas mixtures containing 60 ppmv SO2. Scanning electron microscopy (SEM), energy dispersive X‐ray spectroscopy (EDS) and X‐ray diffraction (XRD) techniques were complimentarily applied to characterize the resulting corrosion products. A partially molten K2SO4‐layer formed on KCl coated specimens, and corrosion resulted in localized broad pits containing sulphides and oxides. The severe pitting attack was decreased by the presence of HCl in the gas mixture.

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Modeling of ferric sulfate decomposition and sulfation of potassium chloride during grate‐firing of biomass

Cited by 12 publications

References 47 publications

Modeling the Use of Sulfate Additives for Potassium Chloride Destruction in Biomass Combustion

Modeling the Use of Sulfate Additives for Potassium Chloride Destruction in Biomass Combustion

Release and Transformation of Sodium during Pyrolysis of Zhundong Coals

Effect of flue gas composition on deposit induced high temperature corrosion under laboratory conditions mimicking biomass firing. Part II: Exposures in SO₂ containing atmospheres

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Modeling of ferric sulfate decomposition and sulfation of potassium chloride during grate‐firing of biomass

Cited by 12 publications

References 47 publications

Modeling the Use of Sulfate Additives for Potassium Chloride Destruction in Biomass Combustion

Modeling the Use of Sulfate Additives for Potassium Chloride Destruction in Biomass Combustion

Release and Transformation of Sodium during Pyrolysis of Zhundong Coals

Effect of flue gas composition on deposit induced high temperature corrosion under laboratory conditions mimicking biomass firing. Part II: Exposures in SO2 containing atmospheres

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Effect of flue gas composition on deposit induced high temperature corrosion under laboratory conditions mimicking biomass firing. Part II: Exposures in SO₂ containing atmospheres