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45 results on '"Cen, Jianmeng"'

18. Carbon Structure of Coal from the CP/MAS 13C NMR Spectra: Effect of Contact Time and Potential Quantitative Modification

Author

Lv, Tong, Fang, Mengxiang, Zeng, Xi, Yan, Jiqing, Huang, Yu, Cen, Jianmeng, and Wang, Qinhui

Abstract

Carbon structures are important for converting coal into chemical products and carbon materials. Solid-state 13C nuclear magnetic resonance (NMR) spectroscopy is a powerful approach for determining the structural characteristics of carbon in coal. However, there is much controversy regarding the quantitative reliability of typical cross-polarization magic angle spinning (CP/MAS) 13C NMR experiments of coal. This study systematically investigated the effect of one of the important factors, CP contact time, using six different coal types with Vdafvalues ranging from 6% to 44%. A series of experimental results at variable contact times from 0.01 to 10 ms indicated that aromatic and aliphatic carbons undergo polarization transfer at different rates, and the nonprotonated carbon of aromatic groups polarized 2–3 times more slowly than that of aliphatic groups. It is challenging for a single CP/MAS 13C NMR experiment with coal to ensure that each type of carbon is sufficiently polarized before the signal decay of the proton spin–lattice relaxation. As a potential quantitative indicator, the initial magnetization intensity independent of contact time was obtained using a classical five-parameter model for CP dynamics, and the initial aromaticity was further calculated. A linear correlation between the apparent and initial aromaticity was introduced into a calibration method of model compounds to refine the effect of contact time. The modified carbon structural parameters of the coal samples showed better agreement in terms of the H/C atomic ratio, Fourier transform infrared spectroscopy, and empirical aromaticity formulas. These results will help to provide a convenient reference for the quantitative analysis of the carbon structure in coal.

Published
2024
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20. Sulfur Transformation during Coal Pyrolysis with Char Heat Carrier.

Author

Wang, Qinhui, Ying, Chengdong, Zhang, Ruiyue, and Cen, Jianmeng

Subjects
COAL pyrolysis, SULFUR, CHAR, COMBUSTION, TEMPERATURE effect, SULFUR cycle
Abstract

To investigate sulfur transformation during coal pyrolysis with char heat carrier (CHC), the effects of temperature, CHC/coal, and CHC production temperature were explored in a fluidized bed. The yield rates of sulfur in H2S (YH2S) and YCOS elevated with temperature. YCH3SH and Ychar‐S decreased, and temperature showed no significant effect on Ytar‐S. CHC inhibited sulfur transformation to the gas phase. More H2S and COS were fixed in mixed‐char in form of CaS by CHC, resulting in the increase of Ychar‐S. CHC was favorable for CH3SH decomposition. The inhibitory effect was enhanced with increasing CHC/coal. Higher production temperature inhibited the sulfur fixation capacity of CHC. CHC enhanced the decomposition of pyrite, organic sulfur, sulfate, and the yield of sulfide in mixed‐char. [ABSTRACT FROM AUTHOR]

Published
2023
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31. Integrated Process of Coal Fast Pyrolysis in a Fluidized Bed Reactor With Reforming Reaction of Simulated Fuel Gas to Promote Light Tar Evolution

Author

Chao Li, Qike Yan, Cen Jianmeng, Luo Zhongyang, and Fang Mengxiang

Subjects
Economics and Econometrics, fast pyrolysis, viruses, light tar, Energy Engineering and Power Technology, complex mixtures, General Works, SFG, law.invention, chemistry.chemical_compound, CRS over Al2O3 catalyst, Fuel gas, law, otorhinolaryngologic diseases, Phenol, Coal, Inert gas, Distillation, Renewable Energy, Sustainability and the Environment, Chemistry, business.industry, selectivity, Tar, Fuel Technology, Chemical engineering, Fluidized bed, business, Pyrolysis
Abstract

The evolution behavior of the light tar during coal fast pyrolysis under inert gas, simulated fuel gas (SFG) atmosphere, and catalytic reformation of simulated (CRS) fuel gas over Ni/Al2O3 was studied in this article. The light tar was recovered from the distillation of the crude tar at the temperature of 300°C and subsequently subjected to detection through the GC-MS analysis. It was found that both SFG and CRS over Ni/Al2O3 significantly enhanced the light tar yield, but a little effect was shown on the heavy tar yield. According to the molecular structure characteristics, the compounds in the light tar could be classified into several groups: aromatic components, phenol components, aliphatic components, heteroatom components, and O-containing components (phenol compounds excluded). It was demonstrated that the selectivity of each component in the light tar varied significantly with the pyrolysis atmosphere and temperature. The evolution of the aromatic components took the dominant role in the light tar produced at high temperature. The SFG and CRS contributed markedly to enhancing the evolution of the O-aromatic components in the light tar, whereas they suppressed the evolution of the O-aliphatic components and the phenol components in the light tar at high temperature.

Published
2021

36. Research on Coal Pyrolysis and Combustion Poly-generation System

Author

Fang, Mengxiang, primary, Cen, Jianmeng, additional, Li, Chao, additional, Wang, Qinhui, additional, Wang, Shurong, additional, Luo, Zhongyang, additional, Cen, Kefa, additional, Chao, Zhichuan, additional, Zhang, Xiaoling, additional, Rao, Xingdao, additional, Dong, Ganlin, additional, Wang, Jiping, additional, and Wang, Yuan, additional

Published
2012
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43. Research on Coal Pyrolysis Property for Polygeneration Technology

Author

Luo Zhongyang, Cen Jianmeng, Su Wenjuan, and Fang Meng-xiang

Subjects
Waste management, business.industry, Destructive distillation, chemistry.chemical_element, Nitrogen, Chemical kinetics, chemistry, Chemical engineering, Scientific method, Coal, Fluidized bed combustion, business, Thermal analysis, Pyrolysis
Abstract

A circulating fluidized bed heat-power-gas-tar polygeneration technology has been developed which is based on the property of coal pyrolysis. To study the effect of temperature and coal type on pyrolysis behavior, the pyrolysis process of four different types of coal was investigated by TGFTIR. The results showed that, at the heating rate of 25?/min, pyrolysis process could be divided into four stages, namely drying stage, preheating stage, primary pyrolysis stage and secondary pyrolysis stage. Primary pyrolysis process was described as first-order reaction model and kinetic parameters were calculated by Coats-Redfern method at different temperature ranges. TG-FTIR coupled with kinetic analysis revealed the formation mechanism and variation of gas products, such as CO, CO2, CH4, during pyrolysis process. Pyrolysis laws provided a reference for achieving the target gas products by controlling temperature and selecting suitable coal type during polygeneration process.

Published
2010

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