Effect of NaOH Treatment on the Low-Temperature Oxidation Behavior of Lignite

Wang, Yongyu; Xue, Sheng; Tang, Yibo; Fu-ding, Mei; He, Wei; Pan, Haifeng

doi:10.1021/acs.energyfuels.9b01516

Cited by 13 publications

(5 citation statements)

References 38 publications

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“…According to Fig. 8a, the content of the ring hydrogen bond (belonging to 3200 cm -1 ), OH⋯OR (belonging to the range of 3300-3315 cm −1 ), OH⋯OH (belonging to the range of 3400-3440 cm −1 ) in the raw coal was lower than that of Sad-8 h and Sad-24 h. The ring hydrogen bond (3200 cm −1 ) and OH (~ 3400 cm −1 ) were prone to be broken www.nature.com/scientificreports/ because of their low stability and tendency to react preferentially with oxygen 44 . This had a significant effect on the combustion characteristics.…”

Section: Resultsmentioning

confidence: 95%

Study the effect of drying on the oxidation thermogravimetric and functional group composition characteristics of immersed lignite

Guo

Zhang²,

Han³

2022

Sci Rep

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The drying process of immersed lignite has a significant influence on the characteristics and progress of spontaneous combustion. To reveal the influence mechanism of the drying process of immersed coal on the spontaneous combustion characteristics and the change rule of the spontaneous combustion process, in this research, we measured the mass change during coal oxidation with thermogravimetry, and the change of the functional groups with Fourier transform infrared spectroscopy. The influence of the drying process on the coal was analyzed by comparing activation energy, functional group of immersed coal with different drying degrees and raw coal. The results showed that, compared with raw coal, the content of Ar–C–O– and antisymmetric stretching vibration of the carboxylate group (–COO–) as well as the stretching vibration in the quinone group (C=O) and the –OH group increased. For the content of $$\delta s.{\text{RCH}}_{{3}}$$ δ s . RCH 3 ,$$\delta as.{\text{R}}_{{2}} {\text{CH}}_{2}$$ δ a s . R 2 CH 2 $$\delta as.{\text{RCH}}_{{3}}$$ δ a s . RCH 3 , the value of Asym.CH2/Asym.CH3 decreased. The content of various functional groups changed to be favorable for oxidation and heat release. At different reaction stages, the activation energy was differently affected by the degree of drying. Average values of activation energies at different reaction stages are shown raw coal had the lowest activation energy. After soaking in water and drying, the activation energy of coal is increased to varying degrees, the reactivity is reduced, and the risk of spontaneous combustion is reduced. After soaking in water and drying, the activation energy of coal is increased to varying degrees, the reactivity is reduced, and the risk of spontaneous combustion is reduced. The activation energy of the coal samples dried for 24 h after soaking in water is the lowest among the coal samples dried for different times after soaking in water, and the moisture content is 10.5%.

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Section: Resultsmentioning

confidence: 95%

Study the effect of drying on the oxidation thermogravimetric and functional group composition characteristics of immersed lignite

Guo

Zhang²,

Han³

2022

Sci Rep

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“…Wang 15 studied the effect of different concentrations of NaOH on the oxidation behavior of lignite at low temperature (T < 200 °C); the spontaneous combustion tendency of coal treated with low-concentration NaOH was increased. Nasir et al 16 found that some minerals or oxygen-containing functional groups can be removed from coal by alkali treatment.…”

Section: Introductionmentioning

confidence: 99%

“…Zhang et al found that acid removes some of the minerals from coal and affects the microcrystalline structure of the coal, increasing its aromaticity. Wang studied the effect of different concentrations of NaOH on the oxidation behavior of lignite at low temperature ( T < 200 °C); the spontaneous combustion tendency of coal treated with low-concentration NaOH was increased. Nasir et al .…”

Section: Introductionmentioning

confidence: 99%

Synergistic Effect of the Moisture Content and pH Value of Aqueous Solutions on Oxidation Characteristics of Coal

Xuan,

Yuan,

2024

ACS Omega

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In order to study the synergistic effect of the moisture content and pH value of aqueous solutions on coal oxidation, coal samples with different moistures were prepared by using aqueous solutions with different pH values (3, 5, 7, and 8). The CO, C 2 H 4 production, oxygen consumption rate, and crossing point temperature parameters in the process of low-temperature oxidation of the prepared coal and raw coal samples were studied by using a low-temperature oxidation device. Thermogravimetry− derivative thermogravimetry (TG−DTG) curves of coal samples with different moistures were obtained on the basis of thermogravimetric analysis of coal by using a synchronous thermal analyzer. According to the characteristic temperature, the process of coal spontaneous combustion (CSC) can be divided into the water evaporation and desorption stage, oxygen absorption and weight gain stage, thermal decomposition and combustion stage, and burnout stage. The Coats−Redfern integral method was used to select the appropriate reaction mechanism function to calculate the apparent activation energy at different stages of the coal reaction process. The results show that the activation energy of the oxidation reaction of the coal sample with a moisture of 15% is the smallest, and the oxidation reaction is the most easy to occur. When the coal samples with a moisture of 15% were oxidized at low temperature, the CO and C 2 H 4 emissions and oxygen consumption rates were the highest. The pH value of the aqueous solution has dual effects on CSC. When the moisture is 15%, the higher the pH value of the aqueous solution, the weaker the promotion effect on the coal oxidation process is and the lower the pH value of the aqueous solution is, the higher the production of CO and C 2 H 4 and the oxygen consumption rate is and the earlier the crossing point temperature is reached during low-temperature oxidation of the coal sample.

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“…However, a few studies focus on the evolution of pore and fissure structures of coal during low-temperature oxidation. − It is of great possibility that there exists a correlation between the pore and fissure structure of coal and oxidation from the macroscopic view. Based on the mainstream theory of the cause of coal spontaneous combustion (CSC), − the theory of coal–oxygen interaction, the initial stage of the coal–oxygen interaction is a physical adsorption stage, which is mainly manifested by the migration of oxygen to the internal pores of coal .…”

Section: Introductionmentioning

confidence: 99%

Exploring the Effect of Low-Temperature Oxidation on the Petrophysical Characteristics of Coal

Li,

Cao,

et al. 2023

ACS Omega

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Low-temperature oxidation leads to the accumulation of heat in coal, and it is an important trigger for coal spontaneous combustion (CSC). The oxidation effects induce irreversible damage in the pore and fracture structures of coal, which provide a way for the infiltration of oxygen. In this work, the evolution of pores and cracks of coal in the progress of low-temperature oxidation is researched based on nitrogen adsorption, scanning electron microscopy (SEM), and ultrasonic testing. The results show that the oxidation effect increases microporous structures and promotes the development of mesopores and macropores in coal. Besides, as the temperature increases, the oxidation effect becomes more significant, while the pore morphology has not changed significantly yet. Meanwhile, the oxidation effect causes coal particles to block or collapse in the macropores, and the plugging degree increases with increasing temperature.

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Effect of NaOH Treatment on the Low-Temperature Oxidation Behavior of Lignite

Cited by 13 publications

References 38 publications

Study the effect of drying on the oxidation thermogravimetric and functional group composition characteristics of immersed lignite

Study the effect of drying on the oxidation thermogravimetric and functional group composition characteristics of immersed lignite

Synergistic Effect of the Moisture Content and pH Value of Aqueous Solutions on Oxidation Characteristics of Coal

Exploring the Effect of Low-Temperature Oxidation on the Petrophysical Characteristics of Coal

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