Investigation of demineralized coal char surface behaviour and reducing characteristics after partial oxidative treatment under an O2 atmosphere

Wang, Zhuozhi; Sun, Rui; Zhao, Yixuan; Li, Yupeng; Ismail, Tamer M.; Ren, Xiaohan

doi:10.1016/j.fuel.2018.06.098

Cited by 18 publications

(7 citation statements)

References 34 publications

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“…There are generally massive oxygen-containing functional groups on the surface of coal-based fuel particles, and the reactivity of the particles is mainly determined by the behavior of these functionalities. , Previous researchers conveyed that the oxygen-containing complexes on the particle surface could be normally divided into six types: carboxyl, hydroxyl(phenol), ether, anhydride, lactone, and quinone . When the oxidizing reactions occurred, the complexes with low thermal stability were more likely to decompose into gaseous products (CO or CO 2 ) or convert into complexes with higher thermal stability .…”

Section: Resultsmentioning

confidence: 99%

Effects of Upgrading Treatment on the Physicochemical Structure, Moisture Re-Adsorption Ability, and NO_x Emission Characteristic of Lignite Particles

2019

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A typical Chinese lignite (HLH) was used for determining the correlation among upgrading temperature, moisture re-adsorption behaviors, and nitrogen evolution characteristics during the combustion process. The upgraded samples were obtained from four drying temperatures: 393, 423, 453, and 483 K in the ComDry (counter flow multi baffle dryer) system. By means of the utilization of the N2 adsorption method and scanning electron microscope, the effects of drying temperature on the surface morphology and pore structural characteristics of lignite particles were determined. With the increase of drying temperature (T d), big pores collapsed into small ones leading to the enhancement of porosity, pore volume, and specific surface area, as well as the reduction of the average pore diameter. The distribution of oxygen-containing functional groups (C(O)) on the surface of the samples dried at different temperatures was identified by Fourier transform infrared spectroscopy. More carboxyl and hydroxyl converted into ether and anhydride, which were thermally stable in the process of drying treatment performed at higher temperatures, reducing the possibility of spontaneous combustion in lignite storage. Both the physical and chemical structural characteristics could be regarded as indicators reflecting the moisture re-adsorption behavior. The moisture content re-adsorbed by the upgraded coal particles expressed negative effects on inhibiting NO emission during the combustion process, and increasing T d could effectively inhibit the occurrence of moisture re-adsorption. The optimum T d for the upgrading treatment of HLH lignite by the ComDry system is 483 K.

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Section: Resultsmentioning

confidence: 99%

Effects of Upgrading Treatment on the Physicochemical Structure, Moisture Re-Adsorption Ability, and NO_x Emission Characteristic of Lignite Particles

2019

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“…The behavior of char particles played a vital role in affecting the generation of NO x , which was the decomposition product of C(N) on the surface of char particles, and the NO x reduction by C(O) or CO, which was the decomposition product of C(O) . Meanwhile, compared to the homogeneous reaction between nitrogen-containing gaseous products and oxidizing reactants in the early stage of O 2 /H 2 O combustion, the heterogeneous reduction reaction between char particles and NO was the major pathway in determining the final conversion ratio of coal-N to NO . Previous research reported the specific reaction mechanism between C(O) and NO at different reaction temperatures systemically, as shown in eqs – .…”

Section: Resultsmentioning

confidence: 99%

“…21 Meanwhile, compared to the homogeneous reaction between nitrogen-containing gaseous products and oxidizing reactants in the early stage of O 2 /H 2 O combustion, the heterogeneous reduction reaction between char particles and NO was the major pathway in determining the final conversion ratio of coal-N to NO. 17 Previous research reported the specific reaction mechanism between C(O) and NO at different reaction temperatures systemically, as shown in eqs 13−17. 25 Obviously, the behavior of C(N) showed significant effects on the generation of nitrogen-containing gaseous products during the O 2 /H 2 O reaction process at high temperatures.…”

Section: Energy and Fuelsmentioning

confidence: 99%

“…Jiang et al revealed that the reactivity of chars was much lower than that of volatile matters under identical combustion conditions, so the char oxidation process was generally the rate-limiting step in the coal combustion process and the contact time between the gaseous products and char particles was relatively long. Because the contact time between flue gas and partially oxidized char particles was much longer, a considerable amount of NO could be consumed by the particles in the oxidation process . However, the effects of H 2 O concentration on the characteristics of C(N) on the surface of chars obtained from the O 2 /H 2 O combustion process are still not very clear but essential for thorough understanding of the emission mechanism of NO x in O 2 /H 2 O combustion.…”

Section: Introductionmentioning

confidence: 99%

“…Because the contact time between flue gas and partially oxidized char particles was much longer, a considerable amount of NO could be consumed by the particles in the oxidation process. 17…”

Section: Introductionmentioning

confidence: 99%

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Effects of Reaction Condition on the Emission Characteristics of Fuel-N during the O₂/H₂O Combustion Process of Demineralized Coal

Wang

Zhu

et al. 2019

Energy Fuels

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This research investigated the emission and evolution characteristics of fuel-N during the O2/H2O combustion process of a typical bituminous coal (Shenhua). To avoid the catalytic interference of alkali metal salts, the demineralized coal obtained from the raw coal sample was employed for the investigation in this research. The effects of reaction temperature (T r) and H2O concentration, which were two vital factors affecting coal combustion characteristics, on the emission characteristics of fuel-N during the combustion process were also taken into consideration. Isothermal combustion tests performed under different O2/H2O conditions (T r: 1073 and 1473 K; O2: 30%; H2O: 0, 3.5, 8.5, 15, 20, and 30 vol %) indicated that relatively high concentrations of N2O, HCN, and NH3 were measured in the O2/H2O combustion of the coal sample. With the increase of T r and H2O concentration, more fuel-N would be released in the devolatilization/volatile oxidation stage of the reaction. The X-ray photoelectron spectroscopy results of chars after devolatilization indicated that most of the N-5 decomposed into HCN or converted to N-6 or N-Q in the early reaction stage at high temperatures and that N-Q was the dominated form of a nitrogen-containing functional group (C(N)) existing on the char particle surface. The reducibility of the chars after O2/H2O devolatilization played vital roles in reducing the emission of NO during the whole O2/H2O combustion process.

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Investigation of combustion reactivity and NO emission characteristics of chars obtained from the devolatilization of raw and partially dried lignite

et al. 2019

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In an attempt to achieve the clean and efficient utilization of lignite, drying pre‐treatment was performed in this study before lignite combustion. The combustion reactivity and NO emission characteristics of the partially dried lignite samples in the char combustion stage were investigated by means of TG and isothermal combustion tests, and the reactivity could be summarized as the following order: L1>L0.5>raw>L3>LT>L5 (chars obtained from the devolatilization of the raw and partially dried coals at 378 K for 0.5, 1, 3, 5, and 120 minutes) and the NO conversion ratio of L1 was the lowest. When the moisture content in the coal particles was relatively high (19.68%‐35.84%), the drying treatment could increase the combustion reactivity and inhibit NO emission in the char combustion stage; When the moisture content was within a relatively low range (0.17%‐19.68%), the moisture removal had negative effects on the reactivity and NO emission in the char combustion stage. The surface behaviour and microstructure of the raw coal char and chars derived from the partially dried coals were clarified by temperature programmed desorption/reduction (TPD/TPR) and Raman spectroscopy. The results illustrated that L1 derived from Lc1 (19.68%) was the most reactive sample with the largest amount of C(O) on the particle surface. There were also more reactive aromatic structures in L1 than other samples. Compared with direct combustion or excessive drying treatment, lignite should be dried to a certain degree (19.68%) for optimized lignite combustion.

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Investigation of demineralized coal char surface behaviour and reducing characteristics after partial oxidative treatment under an O2 atmosphere

Cited by 18 publications

References 34 publications

Effects of Upgrading Treatment on the Physicochemical Structure, Moisture Re-Adsorption Ability, and NO_x Emission Characteristic of Lignite Particles

Effects of Upgrading Treatment on the Physicochemical Structure, Moisture Re-Adsorption Ability, and NO_x Emission Characteristic of Lignite Particles

Effects of Reaction Condition on the Emission Characteristics of Fuel-N during the O₂/H₂O Combustion Process of Demineralized Coal

Investigation of combustion reactivity and NO emission characteristics of chars obtained from the devolatilization of raw and partially dried lignite

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Investigation of demineralized coal char surface behaviour and reducing characteristics after partial oxidative treatment under an O2 atmosphere

Cited by 18 publications

References 34 publications

Effects of Upgrading Treatment on the Physicochemical Structure, Moisture Re-Adsorption Ability, and NOx Emission Characteristic of Lignite Particles

Effects of Upgrading Treatment on the Physicochemical Structure, Moisture Re-Adsorption Ability, and NOx Emission Characteristic of Lignite Particles

Effects of Reaction Condition on the Emission Characteristics of Fuel-N during the O2/H2O Combustion Process of Demineralized Coal

Investigation of combustion reactivity and NO emission characteristics of chars obtained from the devolatilization of raw and partially dried lignite

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Effects of Upgrading Treatment on the Physicochemical Structure, Moisture Re-Adsorption Ability, and NO_x Emission Characteristic of Lignite Particles

Effects of Upgrading Treatment on the Physicochemical Structure, Moisture Re-Adsorption Ability, and NO_x Emission Characteristic of Lignite Particles

Effects of Reaction Condition on the Emission Characteristics of Fuel-N during the O₂/H₂O Combustion Process of Demineralized Coal