Study on the Chemical Inhibition Mechanism of DBHA on Free Radical Reaction during Spontaneous Combustion of Coal

Wang, Jie; Wang, Junfeng; Zhou, Changlin; Wu, Yuguo; Tang, Yibo

doi:10.1021/acs.energyfuels.0c00226

Cited by 29 publications

(10 citation statements)

References 35 publications

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“…At 400°C, the g factor value of coal gangue reaches 2.008823 and the free radical concentration reaches 36.77 × 10 17 at 21% oxygen concentration, the free radical in the reaction system are generally in a high‐energy state, and the relaxation time is further prolonged. After free radical have been accumulated to a concentration enough for initiating the chain reactions of free radical, a large amount of heat is generated, bringing about a rapid increase in the ambient temperature, and finally causing spontaneous combustion of coal gangue 34,35 . Therefore, the spontaneous combustion of coal gangue is a process with the g factor value increasing, the free radical concentration rising, and the relaxation time lengthening (line width decreasing).…”

Section: Discussionmentioning

confidence: 99%

The variations of free radical and index gas CO in spontaneous combustion of coal gangue under different oxygen concentrations

et al. 2021

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Summary In order to study the effect of oxygen concentrations on the change of active groups in the oxidation process of coal gangue, the airflows of different oxygen concentrations were prepared to simulate the oxidation and heating process of coal gangue under oxygen concentrations of 0%, 5%, 10%, 15%, and 21%. During the oxidation and heating process, the free radical parameters were measured at different temperatures in real time. The results show that in the early stage of coal gangue oxidation, the g factor remains at a lower level and do not start to increase until certain temperatures are reached. Besides, the higher the oxygen concentration is, the lower the temperature at which the g factor begins to increase. When the oxygen concentrations are 0%, 5%, 10%, 15%, and 21%, the corresponding temperatures are 225, 200, 150, 150, and 125°C, respectively. Furthermore, with the increase of oxidation temperature, the free radical concentrations experience four stages, namely, the slow increase stage, the rapid increase stage, the stagnant increase stage, and the final increase stage. And the higher the oxygen concentration is, the shorter the free radical stagnant increase stage is. During the oxidation of coal gangue, the line widths decrease slowly before 150°C, and then start to plunge and finally stabilize near the minimum at 350°C. Moreover, the higher the oxygen concentration is, the smaller the minimum values of line widths are. In the oxidation process of coal gangue, the gas product CO amounts are first at a lower level, and then begin to increase rapidly after 150°C. At the same temperature, the increased rates of CO production in coal gangue under the oxygen concentrations of 10%, 15%, and 21% are significantly higher than those under the oxygen concentrations of 0% and 5%. Based on the variation law of free radical parameters in coal gangue under different oxygen concentrations, the actual spontaneous combustion of gangue hills was analyzed and the free radical reaction mechanism of spontaneous combustion of gangue hills was discussed. The research results are of guiding significance for the treatment of spontaneous combustion of coal gangue.

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Section: Discussionmentioning

confidence: 99%

The variations of free radical and index gas CO in spontaneous combustion of coal gangue under different oxygen concentrations

et al. 2021

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“…The results showed that TEMPO can combine with alkyl radicals to form inert substances, hinder the occurrence of free radical chain cycle reactions, and play a role in preventing the spontaneous combustion of coal. Wang 16 et al used N , N -dibenzylhydroxylamine (DBHA) as an inhibitor of spontaneous combustion of coal and conducted research and analysis. The results showed that DBHA can combine with hydrogen peroxide intermediates to form stable compounds, reduce the content of active free radicals in coal, and inhibit the spontaneous combustion of coal.…”

Section: Introductionmentioning

confidence: 99%

Study on the Mechanism of Antioxidants Affecting the Spontaneous Combustion Oxidation of Coal

Zhang

Gao

et al. 2023

ACS Omega

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In this paper, in order to further reveal the mechanism of oxidation inhibitors inhibiting coal spontaneous combustion, the mechanism of typical antioxidants butylated hydroxytoluene (BHT) and vitamin C (VC) inhibiting coal low-temperature oxidation was studied by thermogravimetry (TG), Fourier transform infrared spectroscopy, and quantum chemical simulation. This paper studies the thermal reaction process of coal by TG. The experimental results showed that the characteristic temperature of coal samples increased significantly after adding an antioxidant, and the maximum exothermic peak temperature of coal samples with BHT was 36 °C higher than that of raw coal, and the dehydration activation energy was 1.22 times higher than that of raw coal. Then, through the Fourier transform infrared spectroscopy experiment, it is concluded that antioxidants have a great influence on the content of active groups in the process of oxidative heating of coal, and the hydroxyl structure changes in coal are the most obvious. After BHT and VC were added to the coal, the hydroxyl content in the coal was reduced by 5.90 and 4.20%, respectively. Finally, the molecular models of antioxidants and oxygen-containing functional groups (RCOOH, R–CHO, and R–CH2–CH2–OH) in coal are constructed using quantum chemical theory, and their frontier orbitals and thermodynamic data are calculated according to density functional theory. The reaction mechanisms of antioxidants reacting with hydroxyl groups and with hydroxyl groups and oxygen-containing functional groups were comparatively analyzed. The results of orbital gap analysis indicated that antioxidants react more easily with hydroxyl groups than with oxygen-containing functional groups, and the order of their reaction activity is BHT > VC > R–CH2–CH2–OH > R–CHO > RCOOH. Compared to reactions containing oxygen-containing functional groups and hydroxyl groups, the thermodynamic reaction of hydroxyl groups and antioxidants is more active. Because antioxidants preferentially react with hydroxyl radicals and inhibit part of the chain cycle reaction during spontaneous combustion of coal, antioxidants play a good inhibitory role in spontaneous combustion of coal.

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“…Yan et al proposed an intumescent flame retardant, which can show good inhibitory effects during all stages of coal oxidation. Wang et al selected inorganic salt such as magnesium chloride and calcium chloride to combine with free radical scavengers N , N -dibenzylhydroxylamine and 2,6-di- tert -butyl-4-methylphenol to form a composite inhibitor. Christopher et al studied the effect of inorganic phosphate Pi and sulfonate mixed with surfactants on coal spontaneous combustion and found that inorganic salts can destroy free radicals generated during coal oxidation and surfactants can prevent coal from contacting with oxygen.…”

Section: Introductionmentioning

confidence: 99%

Fire-Prevention Characteristics of an Active Colloid Prepared from Stimulated Fly Ash Component

Jie

Zhou

2022

ACS Omega

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In this paper, an active colloid (AC) with a three-dimensional network framework, prepared from stimulated fly ash (FA) component by an acid–base compound chemical method, was proposed for prevention of coal mine fire. During the stimulation process, the active substance in fly ash can be released and transformed into effective components for fire prevention. Research results show that Al3+, Fe3+, and Ti4+ from FA can serve as metal cross-linking agents to graft-copolymerize with sodium carboxymethyl cellulose. Mg2+ and Ca2+ can be formed into halogenated salts that are encapsulated by composite colloids and cooperate with them to participate in fire prevention. The remaining fly ash solid particles served as an inert component can be fixed in the framework to encapsulate more water, improving the colloid’s strength and water retention. The content of the active component was measured by inductively coupled plasma (ICP) emission spectroscopy to evaluate the stimulation effect of fly ash. The gel time, viscosity, water retention, and other performance parameters were determined for evaluation of physical characteristics. The fire-prevention performances of AC were also determined by the inhibition performance test, thermogravimetric analysis, and infrared spectroscopy. Moreover, the fire-prevention mechanism of AC was also explored. These results showed that the AC prepared from the stimulated fly ash component can greatly inhibit the spontaneous combustion of coal and can be chosen as a potential material for prevention of coal mine fire caused by spontaneous combustion of coal.

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Study on the Chemical Inhibition Mechanism of DBHA on Free Radical Reaction during Spontaneous Combustion of Coal

Cited by 29 publications

References 35 publications

The variations of free radical and index gas CO in spontaneous combustion of coal gangue under different oxygen concentrations

The variations of free radical and index gas CO in spontaneous combustion of coal gangue under different oxygen concentrations

Study on the Mechanism of Antioxidants Affecting the Spontaneous Combustion Oxidation of Coal

Fire-Prevention Characteristics of an Active Colloid Prepared from Stimulated Fly Ash Component

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