Migration and transformation of sodium and chlorine in high-sodium high-chlorine Xinjiang lignite during circulating fluidized bed combustion

Qi, Xiaobin; Song, Guoliang; Yang, Shu; Zhao, Yang; Lyu, Qinggang

doi:10.1016/j.joei.2018.03.005

Cited by 30 publications

(14 citation statements)

References 30 publications

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“…A coating layer on the surfaces of bed material particles would be induced, , forming a melted or sintered layer enriched in (Ca,Na)(Si,Al) 4 O 8 and CaSiO 3 . Most Na would be released as gaseous phases and leave the chamber, leading to severe ash deposition on heat exchange surfaces. , The retention of Na in bottom ash particles was less likely to occur at 950 °C even though quartz as the bed material presented. When the combustion temperature became 800 and 750 °C, as analyzed from XRD and SEM–EDX, more Na was retained in the bottom ash, allowing for the formation of a coating layer enriched in Ca/Na sulfates.…”

Section: Resultsmentioning

confidence: 99%

Experimental Investigation into Ash Deposition and Na Migration Characteristics during Combustion of High Sodium Zhundong Lignite in a Circulating Fluidized Bed Operating at Low Temperatures

Liu

Zhu

et al. 2019

Energy Fuels

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The mineralogical, morphological, and chemical characteristics of ash deposits during combustion of Zhundong lignite (<3 mm) in a 0.2 t d–1 circulating fluidized bed (CFB) operating at relatively low temperatures, that is, 800–760 and 750–680 °C, were investigated. Two air-cooled probes were installed in the furnace dilute phase (P1) and the cyclone outlet (P2) to simulate ash deposition. The deposits along with the bottom ash and fly ash were collected and analyzed by using scanning electron microscopy energy-dispersive X-ray spectroscopy, X-ray diffraction, and inductively coupled plasma optical emission spectroscopy. Results showed that the P1 deposit composed of melted Ca/Na sulfate particles at 800 °C but became granular Na/Ca/Mg aluminosilicate particles at 750 °C. Likewise, the P2 deposit comprised agglomerated particles rich in Na2SO4 and CaSO4 at 800 °C but became discrete Na2SO4 and NaCl particles at 750 °C. The bottom ash was enriched with (Ca,Na)(Si,Al)4O8 and Na2SO4 at 800 °C but turned into Na2SO4, (Na,K)(Si3Al)O8 at 750 °C. The Na content in the bottom ash correspondingly increased from 31.3 to 36.5 mg g–1, retaining more Na in the bottom ash at 750 °C. The fly ash also became discrete particles enriched in Na2SO4 and NaCl. The CFB combustion at 750–680 °C thus decreased the release of Na and the sintering propensity of ash particles and consequently lessened their deposition propensity.

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Section: Resultsmentioning

confidence: 99%

Experimental Investigation into Ash Deposition and Na Migration Characteristics during Combustion of High Sodium Zhundong Lignite in a Circulating Fluidized Bed Operating at Low Temperatures

Liu

Zhu

et al. 2019

Energy Fuels

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“…There is a consensus in the literature that there are two general chlorination mechanisms-direct and indirect one. Direct chlorination is thought to be a prevalent mechanism in the case of NaCl where (high-temperature) direct reaction between NaCl and Cd (or other HMs) oxides occur [67]. Indirect chlorination is more common and was observed (e.g.,) in the case of PVC, CaCl 2 or MgCl 2 and is based on (low-temperature) release of chlorination agent (HCl, Cl 2 ) that is followed by its reaction with CdO (or other HMs oxides) [68].…”

Section: Effect Of CLmentioning

confidence: 99%

“…This is consistent with the conclusion of Yu et al [42]: when temperature reaches melting point of NaCl (801 • C) or KCl (770 • C), NaCl or KCl become liquid phase; then, the reaction rates between liquid NaCl/KCl and SiO 2 or Al 2 O 3 can be accelerated. At higher temperatures, NaCl or KCl was further vaporized into gas phase and the formation of HCl or Cl 2 through gas-solid reaction can occur (as described in Reactions (2)-(6)) [42,67]:…”

Section: Direct Chlorination (Effect Of Nacl)mentioning

confidence: 99%

Behavior of Cd during Coal Combustion: An Overview

et al. 2020

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Due to the unfavorable combination of its toxicity and high volatility, Cd is contained in most lists of potentially hazardous air pollutants with the greatest environmental and human-health concerns. The review paper evaluates the behavior of Cd during combustion (incineration) processes and its redistribution among condensed fractions (bottom ash/slag, fly ash) and volatilized fractions (that passes through most particulate control devices). The paper addresses all important effects of Cd interactions, such as presence of organic or inorganic chlorides, moisture levels, S, P and Na concentrations, flue gas composition etc. Possibilities of using various adsorbents (either within in-furnace regime or applied in post-combustion zone) are evaluated as well. Special attention is paid to mitigating its emissions factors; decreasing Cd volatility and facilitating Cd retention are discussed with the view of various combustion (incineration) conditions and the feed fuel composition.

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“…Then CaSO 4 and CaSiO 3 will be captured by the sticky layer. Qi et al 15 and Tao et al 16 find Ca–Na‐bearing minerals will go through decomposition, evaporation, and interaction to convert to molten phase during the combustion. Dai et al 17 find that Ca atoms tend to transform to eutectic minerals with Al–O bond, decreasing the AFTs, with FactSage, one chemical thermodynamic equilibrium software 18 .…”

Section: Introductionmentioning

confidence: 99%

The effect on ash deposition by blending high‐calcium Zhundong coal with vermiculite: Focusing on minerals transformations

Yang

Jin

Liu

et al. 2020

Asia-Pacific J Chem Eng

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To solve the ash deposition problem caused by burning high‐calcium Zhundong coal (ZDC), the addition of vermiculite is a promising solution. However, complete mechanisms of vermiculite addition reducing ash deposition are still unknown. In this paper, the effect of vermiculite on sodium emission, ash fusion characteristics, and mineral transformation is investigated. The results show that although vermiculite, with limited Na capture capacity, lowers the ash fusion temperatures (AFTs), it can greatly reduce ash deposition. In the combustion of ZDC, calcium‐bearing minerals will react with clay minerals and then convert to molten glassy phase. Those molten minerals will take high melting point minerals, Ca2Al2SiO7 and CaMgSi2O6, as bone, showing slagging phenomenon with high AFTs. When vermiculite is introduced, the main reaction products are Ca2MgSi2O7 and Mg2SiO4 and that reduces the extent of molten minerals formation. The main ash product transforming from Ca2Al2SiO7 to Ca2MgSi2O7 leads to the decrease of AFTs. The initial ash deposition with Ca2Al2SiO7 still happens; however, vermiculite addition makes it hard for ash to grow on the existing ash deposit. The results of FactSage software agree with the experimental ones, and the proportion of slag decreases by 36% with vermiculite at 1250°C.

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Migration and transformation of sodium and chlorine in high-sodium high-chlorine Xinjiang lignite during circulating fluidized bed combustion

Cited by 30 publications

References 30 publications

Experimental Investigation into Ash Deposition and Na Migration Characteristics during Combustion of High Sodium Zhundong Lignite in a Circulating Fluidized Bed Operating at Low Temperatures

Experimental Investigation into Ash Deposition and Na Migration Characteristics during Combustion of High Sodium Zhundong Lignite in a Circulating Fluidized Bed Operating at Low Temperatures

Behavior of Cd during Coal Combustion: An Overview

The effect on ash deposition by blending high‐calcium Zhundong coal with vermiculite: Focusing on minerals transformations

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