Transformation behaviors of C, H, O, N and S in lignite during hydrothermal dewatering process

Mo, Qiong; Liao, Junjie; Chang, Liping; Chaffee, Alan L.; Wang, Bao

doi:10.1016/j.fuel.2018.08.128

Cited by 38 publications

(13 citation statements)

References 41 publications

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“…A comparison of FBDC with HTDC showed that hydrothermal dewatering had a greater influence on the pore structure than other dewatering techniques. This is because H + in water will promote the decomposition of the oxygen-containing functional groups and accelerate the release of volatiles enlarging the specific surface area and pore volume . Finally, it can be concluded that different drying conditions will exert different effects on the physicochemical structures of lignite.…”

Section: Resultsmentioning

confidence: 99%

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Evolution of Physical and Chemical Structures in Lignite during Dewatering Process and Their Effects on Combustion Reactivity

Yang

Liao

et al. 2019

Energy Fuels

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The Inner Mongolia lignite was selected as the feedstock and dewatered by hydrothermal, fixed-bed, and microwave upgrading techniques. The physicochemical structures of the raw coal and dewatered coal samples were determined by N 2 adsorption, Fourier transform infrared, and chemical titration methods. The combustion behavior of coals was investigated by thermogravimetric analyzer, and the results demonstrated that the combustion reactivity of the dewatered coals was enhanced. The apparent activation energies of the coal samples were obtained from nonisothermal single heating rate method, and the results illuminated that the combustion process of these coals could be divided into three stages according to the variations of their apparent activation energies. Those variations were used as the medium to investigate the correlations between combustion reactivity parameters and physicochemical structures. It was found that at stage I of the combustion process, the ignition temperature of the coal was mainly affected by intrinsic chemical reactivity; at stage II, the maximum combustion reaction rate of the coal was affected by intrinsic chemical reactivity and specific area diffusion, and the temperature corresponding to the maximum combustion reaction rate was mainly affected by intrinsic chemical reactivity; and at stage III, the burnout temperature was affected by intrinsic chemical reactivity, and the overall reaction rate was controlled by gas diffusion rate.

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Section: Resultsmentioning

confidence: 99%

“…The hydrothermally dewatered coal was obtained through an autoclave reactor, whose schematic diagram could be found elsewhere, 22 using a mixture of raw coal (100 g) and distilled water in a proportion of 1:2 loaded into it. Lignite was heated to temperature 300 °C and held at this temperature for 30 min.…”

Section: Methodsmentioning

confidence: 99%

Evolution of Physical and Chemical Structures in Lignite during Dewatering Process and Their Effects on Combustion Reactivity

Yang

Liao

et al. 2019

Energy Fuels

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“…42 The reduction in sulfur oxides released during the SP combustion might be due to the presence of sulfur components in active functional groups or unstable structures in the SPs, 43 and these contents were brought into the LPs after the removal of moisture during the microwave heating step. 44 When adding Na 2 SO 4 , there were two SO 2 emissions peaks. The first one was related to the combustion of sulfur in the SPs, and the second one may be associated with the thermal decomposition of SO 4 2− .…”

Section: Resultsmentioning

confidence: 99%

“…Without changing the physical properties of the SPs, the microwave effect can remove the sulfur contained in the SPs . The reduction in sulfur oxides released during the SP combustion might be due to the presence of sulfur components in active functional groups or unstable structures in the SPs, and these contents were brought into the LPs after the removal of moisture during the microwave heating step . When adding Na 2 SO 4 , there were two SO 2 emissions peaks.…”

Section: Resultsmentioning

confidence: 99%

The Influence of Anionic Additives on the Microwave Dehydration Process of Lignite

Liu

Feng

et al. 2020

Energy Fuels

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Different anionic additives were added to lignite to enhance the effect of microwave heating on the dehydration and upgrading processes. The dehydration kinetics and moisture diffusion coefficient as well as the physical and chemical properties of solid and liquid products were studied in detail. During the microwave heating process, the enhancement effect of each additive was in the order of Na2CO3 < Na2SO4 < NaCl < NaNO3. The dehydration process of lignite was well fitted by the logarithmic model. For the solid products, as the promotion effect on the dehydration process of lignite increased, the structure tended to be stable, the content of harmful gas released by combustion was reduced, and the surface hydrophobicity was enhanced. At the same time, for the liquid products, the total organic carbon, chemical oxygen demand, and electrical conductivity increased, the pH decreased and the surface tension increased first and then decreased. With an increasing additive enhancement effect, moisture loss was supplemented by the loss of inorganics and then organics.

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“…While NH 3 can be oxidized to NO in this process or can be used as a reducing agent to reduce NO in the selective catalytic reduction (SCR) denitrification process, so it has dual properties. Mo et al 31 have found that when the basic nitrogen‐containing structural units are heated, the weak bonds would be broken. Part of the product is divided into HCN and NH 3 , and the source of the two products is primarily volatile matter and semi‐char in pyrolysis.…”

Section: Resultsmentioning

confidence: 99%

Thermal conversion behavior and nitrogen‐containing gas products evolution during co‐pyrolysis of cow manure and coal: A thermal gravimetric analyzer/differential scanning calorimetry–mass spectrometer investigation

Bai

Wang

et al. 2021

Asia-Pacific J Chem Eng

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The kinetics and thermal behaviors of cow manure (CM) and Meihuajing bituminous coal (MHJ) blending from room temperature to 950°C were investigated by thermal gravimetric analyzer (TGA) coupled with differential scanning calorimetry (DSC) and mass spectrometer (MS). TG curves show that the high heating rate accelerates thermal decomposition rate, and the position of differential thermal gravity (DTG) peaks shifts to a higher temperature. Owing to the heat transfer limitation phenomenon, the residual weight of CM is only 40.38% with the heating rate of 1°C/min in comparison with other heating rate. DSC takes more time to reach a steady state than TGA. Gaseous evolution curves of HCN and NH3 were obtained during the pyrolysis of blends based on TG–MS experiments. With the increased heating rate, the emissions increased a lot due to the secondary reaction of volatiles. The Eα of 1C1M obtained using Kissinger–Akahira–Sunose (KAS), Flynn–Wall–Ozawa (FWO), Friedman, and Kissinger methods is within 124.58–317.18, 121.97–321.11, 150.28–331.64, and 209.26 kJ/mol, respectively. The kinetic parameters calculated based on four model‐free kinetic modeling methods shows good agreement. And the thermodynamic parameters were obtained and discussed under different conversion rates. This work is greatly important to understand the co‐prolysis mechanism of CM and coal and to design the pyrolysis reactors.

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Transformation behaviors of C, H, O, N and S in lignite during hydrothermal dewatering process

Cited by 38 publications

References 41 publications

Evolution of Physical and Chemical Structures in Lignite during Dewatering Process and Their Effects on Combustion Reactivity

Evolution of Physical and Chemical Structures in Lignite during Dewatering Process and Their Effects on Combustion Reactivity

The Influence of Anionic Additives on the Microwave Dehydration Process of Lignite

Thermal conversion behavior and nitrogen‐containing gas products evolution during co‐pyrolysis of cow manure and coal: A thermal gravimetric analyzer/differential scanning calorimetry–mass spectrometer investigation

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