Effect of steam on the transformation of sulfur during demineralized coal pyrolysis

Wang, Min; Du, Qian; Li, Yupeng; Xu, Junjie; Gao, Jianmin; Wang, Hui

doi:10.1016/j.jaap.2019.03.011

Cited by 27 publications

(28 citation statements)

References 41 publications

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“…5 38 , as it can be converted to H2S (R9) in steam atmosphere in the reactor . Consistent with some previous experimental conclusions, sulfur-containing gases are mainly H2S during pyrolysis of thiophenes in water vapor system 3,9 . Therefore, at higher temperatures, thiophenes desulfurization mechanisms are most likely dominated by radical reactions under steam atmosphere.…”

Section: Desulfurization Mechanisms Of Thiophenes With Free Radicals (•H And•oh)supporting

confidence: 92%

Stimulation Calculation of Desulfurization Mechanisms Dominated by Free Radicals Reactions During Pyrolysis of Thiophenes Under Water Vapor Atmosphere

Cheng

Chen

Guo

et al. 2021

Preprint

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The desulfurization mechanisms of thiophene and 2-methyl thiophene were investigated by the density functional theory (DFT) during pyrolysis under water vapor atmosphere. All possible reaction pathways of these desulfurization mechanisms were explored at M06-2X/6-311g (d) level. The Multwfn3.0 and VMD1.9.2 programs were used to analyze weak interactions between thiophene compounds and H2O molecule. It can be seen that hydrogen bonds can be formed in the reactions of thiophene sulfurs and H2O. Since H2O molecule can decompose at higher temperature and generate free radicals, such as·H and·OH,, the desulfurization mechanisms of thiophene and 2-methyl thiophene with free radicals need to be further considered. The reaction energy barriers (∆G≠) and reaction energies (∆GP) of thiophene and 2-methyl thiophene with H2O molecule (g) or free radicals (·H and·OH) have been stimulated and calculated in detail. Based on the transition state theory (TST), the rate constants corresponding to these elementary reactions are also calculated, meanwhile the speed and spontaneity of every reaction can be obtained from the aspect of kinetics. Theoretically, it is found that H2O (g) directly attacking C-S bonds of thiophene and 2-methyl thiophene cannot easily generate COS and H2S even at 1200 K in terms of thermodynamics and kinetics. If the desulfurization mechanisms of thiophenes are investigated by free radicals mechanisms under steam atmosphere, their initial energy barriers needing to be overcome significantly reduce. Therefore, desulfurization mechanisms of thiophenes and H2O (g) are the most possibly dominated by radical reactions at higher temperatures and H2S is mainly generated.

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Section: Desulfurization Mechanisms Of Thiophenes With Free Radicals (•H And•oh)supporting

confidence: 92%

Stimulation Calculation of Desulfurization Mechanisms Dominated by Free Radicals Reactions During Pyrolysis of Thiophenes Under Water Vapor Atmosphere

Cheng

Chen

Guo

et al. 2021

Preprint

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“…However, the degradation rate of light transmittance in 100 °C + 100%RH + Sulfur ageing was the largest compared to that of other conditions. According to Wang et al, (2019) and Manconi and Lens, (2009), the sulfur (S 8 ) can be transformed into hydrogen sulfide (H 2 S) with existence of water vapor, and the strong sensitivity of silicone toward H 2 S was confirmed. Therefore, the chemical reaction between silicone and H 2 S might lead to the most serious optical property deterioration of test samples in 100 °C + 100%RH + Sulfur ageing.…”

Section: Optical Propertiesmentioning

confidence: 99%

“…The LED was attacked by the sulfur and sulfide coming from the air atmosphere, when working in harsh environments such as mine, chemical fertilizer plant, livestock farm, and sewage treatment plant. Silicone is prone to absorb sulfur and sulfide causing the degradation of itself (Wang et al, 2019). For example, Zibold et al (2017) studied the impacts of hydrogen sulfide on light output power of LEDs.…”

Section: Introductionmentioning

confidence: 99%

Sulfur-Rich Ageing Mechanism of Silicone Encapsulant Used in LED Packaging: An Experimental and Molecular Dynamic Simulation Study

Chen

Cao

et al. 2022

Front. Mater.

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In a light-emitting diode (LED) package, silicone encapsulant serves as a chip protector and enables the light to transmit, since it exhibits the advantages of high light transmittance, high refractive index, and high thermal stability. However, its reliability is still challenged under harsh operation conditions. In this study, the optical and mechanical properties of silicone encapsulant, including appearance, light transmittance, Young’s modulus, and tensile strength, were experimentally monitored during the sulfur-rich ageing process. Meanwhile, the Fourier transform infrared (FTIR) spectroscopy and molecular dynamics (MD) simulation were used to reveal its degradation mechanism. The results show that 1) in the sulfur (S8)-rich ageing process, the severe vulcanization reaction occurred in silicone encapsulant assisted only by high temperature and high moisture, with the existence of H2S as the reaction product of S8 and H2O vapor. 2) Vulcanization characterized by the formation of the sulfhydryl (-SH) group lowered both optical and mechanical properties of silicone encapsulant. 3) The hydrolysis reaction featured by the formation of the hydroxyl (-OH) group decreased the mechanical performances of silicone encapsulant but brought slight harm to its optical performances.

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“…During the pyrolysis process, sulfur in coal first forms volatile sulfur-containing gas (mainly H 2 S, a small amount of SO 2 , CS 2 , mercaptans, etc.) and sulfur in tar, and the sulfur that is difficult to decompose remains in semicoke. − The decomposition of pyrite in coal and aliphatic organic sulfur produces a large amount of H 2 S during pyrolysis . The decomposition of organic sulfur is closely related to the chemical structures of its functional groups.…”

Section: Introductionmentioning

confidence: 99%

“…From the perspective of thermodynamics, the desulfurization efficiency of coal in an inert atmosphere is not high, so sulfur is mainly contained in semicoke and tar . The steam atmosphere, as an oxidizing atmosphere, is more beneficial to the removal of sulfur in coal than inert atmosphere, especially it can remove more than 90% of inorganic sulfur in coal. , The steam added during pyrolysis or gasification also promotes the production of H 2 S gas, thereby increasing the share of sulfur in the gas and reducing the share of sulfur in the semicoke. ,,, …”

Section: Introductionmentioning

confidence: 99%

Effect of H₂O on the Transformation of Sulfur during Demineralized Coal Pyrolysis: Molecular Dynamics Simulation Using ReaxFF

Wang

Gao

Xu³

et al. 2021

Energy Fuels

Self Cite

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Reactive force field molecular dynamics (ReaxFF-MD) (reactive force field molecular dynamics) is a promising method for exploring complex chemical reactions, allowing a better understanding of sulfur transformation during coal pyrolysis. In this work, we built three pyrolysis systems with different H2O contents to explore the effect of H2O on the transformation of sulfur during demineralized pyrolysis by ReaxFF-MD. Product distributions, sulfur-containing bonds, and the path of organic sulfur in different systems were analyzed. We found that H2O could accelerate the pyrolysis process, reduce the semicoke yield, and increase the production of gas components significantly, including H2S gas. By adding H2O during pyrolysis, more sulfur in semicoke and heavy tar converted to gas and light tar, respectively. H2O not only promoted the cleavage of C–S bonds but also generated more H free radicals to form SH free radicals, thereby promoting the removal of organic sulfur.

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Effect of steam on the transformation of sulfur during demineralized coal pyrolysis

Cited by 27 publications

References 41 publications

Stimulation Calculation of Desulfurization Mechanisms Dominated by Free Radicals Reactions During Pyrolysis of Thiophenes Under Water Vapor Atmosphere

Stimulation Calculation of Desulfurization Mechanisms Dominated by Free Radicals Reactions During Pyrolysis of Thiophenes Under Water Vapor Atmosphere

Sulfur-Rich Ageing Mechanism of Silicone Encapsulant Used in LED Packaging: An Experimental and Molecular Dynamic Simulation Study

Effect of H₂O on the Transformation of Sulfur during Demineralized Coal Pyrolysis: Molecular Dynamics Simulation Using ReaxFF

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Effect of steam on the transformation of sulfur during demineralized coal pyrolysis

Cited by 27 publications

References 41 publications

Stimulation Calculation of Desulfurization Mechanisms Dominated by Free Radicals Reactions During Pyrolysis of Thiophenes Under Water Vapor Atmosphere

Stimulation Calculation of Desulfurization Mechanisms Dominated by Free Radicals Reactions During Pyrolysis of Thiophenes Under Water Vapor Atmosphere

Sulfur-Rich Ageing Mechanism of Silicone Encapsulant Used in LED Packaging: An Experimental and Molecular Dynamic Simulation Study

Effect of H2O on the Transformation of Sulfur during Demineralized Coal Pyrolysis: Molecular Dynamics Simulation Using ReaxFF

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Effect of H₂O on the Transformation of Sulfur during Demineralized Coal Pyrolysis: Molecular Dynamics Simulation Using ReaxFF