Selective removal of sodium from low-rank Xinjiang coal upon multistage countercurrent water washing

experimental investigation and kinetics modeling

Song Zhou, Tahereh Hosseini, Jie Zhao, Xiwang Zhang, Hongwei Wu, Lian Zhang

Research output: Contribution to journalArticleResearchpeer-review

Abstract

Prior washing of coal is an essential step for the minimization of ash-related slagging and fouling inside a coal-fired boiler. With regard to the coal washing process, the recyclability of the washing reagent, usually water, is critical from both cost-effective and efficiency perspectives. This paper addresses the washing kinetics of water-soluble Na + from two different low-rank Xinjiang coals using both fresh and used/recycled water to alleviate the ash-related fouling in low-rank coal-fired boilers. Apart from once-through fresh water washing, washing using recycled water via both multicycle single-stage and three-stage countercurrent processes was studied in detail to investigate the recyclability of water. Additionally, a modified shrinking core model (SCM) was developed to reveal the Na + removal mechanism under all washing conditions. Our experimental results showed that the Na + removal extent decreased with the recycling of used water due to an increase in the Na + concentration in the recycled water and/or a decrease in the Na + content in the washed coal. The saturation point of Na + in the used water, beyond which the water can no longer remove Na + , is far below the solubility of NaCl in water. The modeling approach further confirmed that the overall rate for the removal of water-soluble Na + is dominated by the intraparticle diffusion within the coal matrix. The effective diffusion coefficient of Na + was within the range of 0.28 × 10 -6 to 3.75 × 10 -6 cm 2 /s, which agrees with reported values in the literature. Additionally, a novel iterative calculation method integrating the modified SCM into the three-stage countercurrent washing process has been proposed to predict the Na + removal at each stage for each cycle. The results show that the water can be recycled a maximum of 15 times in the three-stage countercurrent process.

Original languageEnglish
Pages (from-to)2142-2152
Number of pages11
JournalEnergy and Fuels
Volume33
Issue number3
DOIs
Publication statusPublished - 21 Mar 2019

Cite this

@article{917c178fd10a433e9f7f5fc4867cb722,
title = "Selective removal of sodium from low-rank Xinjiang coal upon multistage countercurrent water washing: experimental investigation and kinetics modeling",
abstract = "Prior washing of coal is an essential step for the minimization of ash-related slagging and fouling inside a coal-fired boiler. With regard to the coal washing process, the recyclability of the washing reagent, usually water, is critical from both cost-effective and efficiency perspectives. This paper addresses the washing kinetics of water-soluble Na + from two different low-rank Xinjiang coals using both fresh and used/recycled water to alleviate the ash-related fouling in low-rank coal-fired boilers. Apart from once-through fresh water washing, washing using recycled water via both multicycle single-stage and three-stage countercurrent processes was studied in detail to investigate the recyclability of water. Additionally, a modified shrinking core model (SCM) was developed to reveal the Na + removal mechanism under all washing conditions. Our experimental results showed that the Na + removal extent decreased with the recycling of used water due to an increase in the Na + concentration in the recycled water and/or a decrease in the Na + content in the washed coal. The saturation point of Na + in the used water, beyond which the water can no longer remove Na + , is far below the solubility of NaCl in water. The modeling approach further confirmed that the overall rate for the removal of water-soluble Na + is dominated by the intraparticle diffusion within the coal matrix. The effective diffusion coefficient of Na + was within the range of 0.28 × 10 -6 to 3.75 × 10 -6 cm 2 /s, which agrees with reported values in the literature. Additionally, a novel iterative calculation method integrating the modified SCM into the three-stage countercurrent washing process has been proposed to predict the Na + removal at each stage for each cycle. The results show that the water can be recycled a maximum of 15 times in the three-stage countercurrent process.",
author = "Song Zhou and Tahereh Hosseini and Jie Zhao and Xiwang Zhang and Hongwei Wu and Lian Zhang",
year = "2019",
month = "3",
day = "21",
doi = "10.1021/acs.energyfuels.9b00055",
language = "English",
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pages = "2142--2152",
journal = "Energy and Fuels",
issn = "0887-0624",
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Selective removal of sodium from low-rank Xinjiang coal upon multistage countercurrent water washing : experimental investigation and kinetics modeling. / Zhou, Song; Hosseini, Tahereh; Zhao, Jie; Zhang, Xiwang; Wu, Hongwei; Zhang, Lian.

In: Energy and Fuels, Vol. 33, No. 3, 21.03.2019, p. 2142-2152.

Research output: Contribution to journalArticleResearchpeer-review

TY - JOUR

T1 - Selective removal of sodium from low-rank Xinjiang coal upon multistage countercurrent water washing

T2 - experimental investigation and kinetics modeling

AU - Zhou, Song

AU - Hosseini, Tahereh

AU - Zhao, Jie

AU - Zhang, Xiwang

AU - Wu, Hongwei

AU - Zhang, Lian

PY - 2019/3/21

Y1 - 2019/3/21

N2 - Prior washing of coal is an essential step for the minimization of ash-related slagging and fouling inside a coal-fired boiler. With regard to the coal washing process, the recyclability of the washing reagent, usually water, is critical from both cost-effective and efficiency perspectives. This paper addresses the washing kinetics of water-soluble Na + from two different low-rank Xinjiang coals using both fresh and used/recycled water to alleviate the ash-related fouling in low-rank coal-fired boilers. Apart from once-through fresh water washing, washing using recycled water via both multicycle single-stage and three-stage countercurrent processes was studied in detail to investigate the recyclability of water. Additionally, a modified shrinking core model (SCM) was developed to reveal the Na + removal mechanism under all washing conditions. Our experimental results showed that the Na + removal extent decreased with the recycling of used water due to an increase in the Na + concentration in the recycled water and/or a decrease in the Na + content in the washed coal. The saturation point of Na + in the used water, beyond which the water can no longer remove Na + , is far below the solubility of NaCl in water. The modeling approach further confirmed that the overall rate for the removal of water-soluble Na + is dominated by the intraparticle diffusion within the coal matrix. The effective diffusion coefficient of Na + was within the range of 0.28 × 10 -6 to 3.75 × 10 -6 cm 2 /s, which agrees with reported values in the literature. Additionally, a novel iterative calculation method integrating the modified SCM into the three-stage countercurrent washing process has been proposed to predict the Na + removal at each stage for each cycle. The results show that the water can be recycled a maximum of 15 times in the three-stage countercurrent process.

AB - Prior washing of coal is an essential step for the minimization of ash-related slagging and fouling inside a coal-fired boiler. With regard to the coal washing process, the recyclability of the washing reagent, usually water, is critical from both cost-effective and efficiency perspectives. This paper addresses the washing kinetics of water-soluble Na + from two different low-rank Xinjiang coals using both fresh and used/recycled water to alleviate the ash-related fouling in low-rank coal-fired boilers. Apart from once-through fresh water washing, washing using recycled water via both multicycle single-stage and three-stage countercurrent processes was studied in detail to investigate the recyclability of water. Additionally, a modified shrinking core model (SCM) was developed to reveal the Na + removal mechanism under all washing conditions. Our experimental results showed that the Na + removal extent decreased with the recycling of used water due to an increase in the Na + concentration in the recycled water and/or a decrease in the Na + content in the washed coal. The saturation point of Na + in the used water, beyond which the water can no longer remove Na + , is far below the solubility of NaCl in water. The modeling approach further confirmed that the overall rate for the removal of water-soluble Na + is dominated by the intraparticle diffusion within the coal matrix. The effective diffusion coefficient of Na + was within the range of 0.28 × 10 -6 to 3.75 × 10 -6 cm 2 /s, which agrees with reported values in the literature. Additionally, a novel iterative calculation method integrating the modified SCM into the three-stage countercurrent washing process has been proposed to predict the Na + removal at each stage for each cycle. The results show that the water can be recycled a maximum of 15 times in the three-stage countercurrent process.

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U2 - 10.1021/acs.energyfuels.9b00055

DO - 10.1021/acs.energyfuels.9b00055

M3 - Article

VL - 33

SP - 2142

EP - 2152

JO - Energy and Fuels

JF - Energy and Fuels

SN - 0887-0624

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