Research on Sodium Removal from Zhundong Coal

Chen, Chuan; Zhang, Shou Yu; Shi, Da Zhong; Lv, Jun Fu; Liu, Da Hai; Guo, Xinyun; Dong, Ai Xia; Xiong, Shao Wu

doi:10.4028/www.scientific.net/amr.734-737.614

Cited by 15 publications

(10 citation statements)

References 9 publications

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“…These problems can bring about unscheduled shutdowns and increase in operation cost . Investigators believed that the high amount of alkali metals (mainly sodium) in Zhundong coal should be responsible for these ash-related problems. , Hence, the safe and efficient utilization of Zhundong coals will to a large extent depend on our understanding of transformation behaviors of alkali metal sodium and its functional mechanism on ash deposition. It is challenging to explore the ash deposition problems related to the thermal utilization of Zhundong coals directly using the existing research findings on the behavior of alkali metals.…”

Section: Introductionmentioning

confidence: 99%

Release and Transformation of Sodium during Pyrolysis of Zhundong Coals

Wang

et al. 2014

Energy Fuels

110

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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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Section: Introductionmentioning

confidence: 99%

Release and Transformation of Sodium during Pyrolysis of Zhundong Coals

Wang

et al. 2014

Energy Fuels

110

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“…Yan et al find that the forms of alkali metal in ZD coal have different effects on fuel conversion and alkali metal in ZD coal is mainly in the water-soluble form . Water-soluble alkali metal in fuel can be removed by washing. , In this work, the effects of water-soluble alkali metal in ZD coal were investigated on the characteristics of ZD coal conversion and NO emissions in CLC with different oxygen carriers. The influences of the gasification agent and reaction temperature were also studied.…”

Section: Introductionmentioning

confidence: 99%

“…With the aim at this problem, a lot of studies have been conducted. When additives, such as kaolin, were introduced during the combustion process of ZD coal, ash problems can be restrained effectively by physical or chemical interactions between additives and coal ash. − The method of co-combustion was also studied, and the results proved that co-combustion was a feasible way of solving these ash problems by decreasing the content of sodium in ash and controlling the sodium release. − To reduce the content of sodium in ZD coal, coal washing was also used to pretreat ZD coal and then water-soluble alkali metal was removed from coal, suppressing ash problems. , Besides, a novel combustion technology, chemical looping combustion (CLC), was applied to ZD coal combustion for its low operation temperature, and its bed material could control the release of sodium. , Among these above methods, CLC is attracting more attention of researchers for its advantages in solving these ash problems. Furthermore, CLC is one of the most promising CO 2 capture technologies. − With the pressure of global warming increasing, CLC is becoming more popular.…”

Section: Introductionmentioning

confidence: 99%

“…6−10 To reduce the content of sodium in ZD coal, coal washing was also used to pretreat ZD coal and then watersoluble alkali metal was removed from coal, suppressing ash problems. 11,12 Besides, a novel combustion technology, chemical looping combustion (CLC), was applied to ZD coal combustion for its low operation temperature, and its bed material could control the release of sodium. 13,14 Among these above methods, CLC is attracting more attention of researchers for its advantages in solving these ash problems.…”

Section: Introductionmentioning

confidence: 99%

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Investigations of Zhundong Coal with Removing Water-Soluble Sodium in Chemical Looping Combustion

et al. 2022

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Zhundong (ZD) coal is one significant fuel source in China but contains a lot of sodium, limiting its utilization. In this work, the effects of sodium in ZD coal were investigated on coal conversion and NO x emissions with a batch fluidized bed reactor in chemical looping. Here, ZD coal was processed by the water-washing method to remove water-soluble sodium in ZD coal. During the traditional combustion process, water-soluble sodium had negative effects on coal conversion and NO generation. When chemical looping was applied to ZD coal combustion, the NO emission was restrained largely and mainly from pyrolysis. In addition, the gasification agent facilitated NO generation, and CO2 had a stronger effect on chemical looping. The NO generation was ascribed to the oxidization of the oxygen carrier and increased with the increase of the oxygen carrier in reactivity. Besides, water-soluble sodium promoted NO generation but restrained coal conversion in chemical looping. Furthermore, the NO generation rate was also affected by the reaction temperature, and an increasing reaction temperature promoted NO generation, especially using hematite as the oxygen carrier.

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“…Due to its superhuge reserves, low-cost mining, high reactivity, and low contents of ash and sulfur, the utilization of Zhundong coal has currently attracted growing concern. , Unfortunately, a series of ash-related problems occur during thermal conversion of Zhundong coal, e.g., fouling, ash depositing, and bed agglomeration. It is reported that these problems are attributable to the high content of sodium in Zhundong coal. − Therefore, it appears imperative to get a clear understanding of the release behavior and transformation mechanism of alkalis for the clean and efficient utilization of Zhundong coal.…”

Section: Introductionmentioning

confidence: 99%

Gasification Characteristics and Sodium Transformation Behavior of High-Sodium Zhundong Coal

Zhang

2017

Energy Fuels

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The Zhundong coalfield is a newly discovered superhuge coal deposit in China. Zhundong coal is considered as a potential resource for gasification, due to its high reactivity. However, the high sodium content in Zhundong coal could cause serious ash-related problems during its thermal utilization. This study was conducted to investigate the gasification characteristics and sodium transformation behavior of a typical high-sodium Zhundong coal. The gasification performance of Zhundong coal is greatly improved at elevated temperature, which is verified by both thermogravimetric analysis and bench-scale study in a bubbling fluidized bed reactor. Compared to Shigouyi coal, Zhundong coal shows better gasification reactivity at the same temperature, indicating better adaptability of Zhundong coal to fluidized bed gasification. Sodium in Zhundong coal chiefly exists as the water-soluble form. The temperature is a crucial parameter affecting the release and transformation of sodium. With increasing temperature, more sodium is released to the gas phase, primarily in the form of NaCl(g). Sodium in the gasification fly ash mainly exists as NaCl, and a small amount of NaAlSiO4 is also identified, whereas the major crystalline phase of sodium in the bottom ash is NaAlSiO4. The formation of high-melting-point sodium containing NaAlSiO4 is beneficial for mitigation of bed agglomeration problems during high-sodium coal gasification.

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Research on Sodium Removal from Zhundong Coal

Cited by 15 publications

References 9 publications

Release and Transformation of Sodium during Pyrolysis of Zhundong Coals

Release and Transformation of Sodium during Pyrolysis of Zhundong Coals

Investigations of Zhundong Coal with Removing Water-Soluble Sodium in Chemical Looping Combustion

Gasification Characteristics and Sodium Transformation Behavior of High-Sodium Zhundong Coal

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