Biodesulphurization of coal: behaviour of trace elements

Morán, Antonio; Cara, J.; Miles, N.J.; Shah, C L

doi:10.1016/s0016-2361(01)00142-9

Cited by 10 publications

(3 citation statements)

References 8 publications

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“…Demir et al examined the effect of froth flotation on the removal of the trace element(s) content from coal. Morán et al found that some pro-sulfur elements, such as Ni, Cu, Zn, As, among others, can be partly removed by the biological desulfurization process. Helble investigated the effects of coal separation on the reduction of emissions of trace elements during coal combustion.…”

Section: Introductionmentioning

confidence: 99%

Arsenic in Coal: Modes of Occurrence, Distribution in Different Fractions, and Partitioning Behavior during Coal Separation—A Case Study

et al. 2016

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The content and modes of occurrence of arsenic and its distribution in Yunnan coal of China as well as its partitioning behavior during the coal separation process were investigated. The following laboratory equipment such as proximate analyzer, ultimate analyzer, sulfur analyzer, inductively coupled plasma mass spectrometer and the methods including sequential chemical extraction process, screening analysis, float-and-sink analysis, heavy liquid separation, and progressive release flotation were frequently used during the research process. The coal sample has a high sulfur content of 8.21%, and its arsenic content is 15.1 μg/g, which is within the range of the mild enrichment level. Content relationship among the various modes of occurrence in order is sulfide-associated form (47.38%) > organically bounded form (18.09%) > silicate-associated form (17.51%) > carbonate-associated form (12.04%) > ion-exchangeable form (3.84%) > water-soluble form (1.14%). The sulfide-associated form is the dominant mode of occurrence of arsenic in the raw coal, which means arsenic has an affinity to sulfur. Arsenic in the sulfide-associated form mainly occurs in the inorganic sulfide minerals (especially in pyrite). Besides, the arsenic content increases with the decrease of coal particle size, and arsenic is concentrated in high-density products. There is a good correlation between the removal rate of arsenic and clean coal ash in either gravity separation or flotation, and arsenic removal rate of 57.96% and 70.77% could be obtained through gravity separation and flotation, respectively. In order to ensure arsenic removal rate and clean coal yield, a combined approach of physics and chemistry should be developed.

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Section: Introductionmentioning

confidence: 99%

Arsenic in Coal: Modes of Occurrence, Distribution in Different Fractions, and Partitioning Behavior during Coal Separation—A Case Study

et al. 2016

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“…Different techniques of desulfurization have been developed based on physical, microbial, and chemical principles, but the former two methods are ineffective in removing sulfur completely. − Chemical methods are promising desulfurization processes, are used extensively worldwide, and primarily utilize different oxidizing agents as desulfurizing reagents. − Although chemical processes can successfully remove almost the entire inorganic sulfur component of coal, removal of organic sulfur is achieved to a certain extent.…”

Section: Introductionmentioning

confidence: 99%

Desulfurization of Organic Sulfur from a Subbituminous Coal by Electron-Transfer Process with K₄[Fe(CN)₆]

Borah¹

2005

Energy Fuels

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The desulfurization reaction involving direct electron transfer from potassium ferrocyanide, K 4 [Fe (CN) 6 ], successfully removed organic sulfur from a subbituminous coal. The temperature variation of desulfurization revealed that increase of temperature enhanced the level of sulfur removal. Moreover, the desulfurization reaction was found to be dependent on the concentration of K 4 [Fe(CN) 6 ]. Gradual increase in the concentration of K 4 [Fe(CN) 6 ] raised the magnitude of desulfurization, but at higher concentration the variation was not significant. The removal of organic sulfur from unoxidized coal slightly increased with reduced particle size. Desulfurization from oxidized coals (prepared by aerial oxidation) revealed a higher level of sulfur removal in comparison to unoxidized coal. Highest desulfurization of 36.4 wt % was obtained at 90°C and 0.1 M concentration of K 4 [Fe(CN) 6 ] in the 100-mesh size oxidized coal prepared at 200°C. Model sulfur compound study revealed that aliphatic types of sulfur compounds are primarily responsible for desulfurization. Because of higher stability, thiophene and condensed thiophene-type of compounds perhaps remained unaffected by the electron-transfer agent. Infrared study revealed the formation of oxidized sulfur compounds (sulfoxide, sulfone, sulfonic acid, etc.) in the oxidized coals. Band intensities in these oxidized compounds due to common -SdO and -SO 2 units increased in their respective regions. The desulfurization reaction in different systems is well-represented by the pseudo-first-order kinetic model. The intrinsic rate constants were found to be in the range of (1.8-3.5) × 10 -5 s -1 , which implies that the reaction proceeds at a slow and steady rate. The activation energy of the reaction in different systems falls in the range of 5.2-8.8 kJ mol -1 . Lower values of frequency factor (range: (1.9-5.5) × 10 -4 s -1 ) revealed that during the course of the reaction an associated type of compound (activated complex) was formed. Application of the transition state theory indicated that the desulfurization reaction proceeds with the absorption of heat (endothermic reaction) and is nonspontaneous in nature.

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“…Various physical, microbial, and chemical methods of desulfurization are known; however, the former two are ineffective in leaching organic sulfur to the permissible level from coal. − In contrast, chemical methods are promising desulfurization processes and are usually accomplished using various oxidizing agents. − Almost all the sulfate and pyritic sulfur can effectively be removed by chemical methods; however, in the case of organic sulfur, removal is achieved to a reasonable extent.…”

Section: Introductionmentioning

confidence: 99%

Electron-Transfer-Induced Desulfurization of Organic Sulfur from Sub-bituminous Coal

Borah¹

2004

Energy Fuels

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The intent of this paper is to investigate the effects of leaching time and temperature on the level of desulfurization of organic sulfur by an electron-transfer process involving the transition-metal ion Ni2+ from a sub-bituminous Indian coal. The electron-transfer process was accomplished both in the presence and the absence of naphthalene with unoxidized and oxidized samples. Desulfurization has been determined to be greater in oxidized samples. The presence of naphthalene enhanced the amount of desulfurization both in unoxidized and oxidized samples, revealing that it serves as an excellent electron-transfer agent. Increases in reaction time and temperature increased the level of desulfurization. The electron-transfer process, in the presence of naphthalene, succeeded in removing a maximum of 16.3 wt % organic sulfur from unoxidized coal and 18.7 wt % from oxidized coal at 50 °C and 4 h. Study of a model sulfur compound indicated that the desulfurization is primarily due to aliphatic-type compounds, such as dibenzothiophene, that is unable to release sulfur under these conditions. A higher level of desulfurization in oxidized coals is consistent with the formation of oxidized sulfur compounds, as revealed by the infrared study, where it is observed that band intensities due to −SO and −SO2 units have decreased in their respective regions in the desulfurized coals. The sulfur removal process is continuous. Application of a pseudo-first-order kinetic model produced overall rate constants for the desulfurization reaction that consistently fell in the range of 5.2 × 10-6−2.1 × 10-5 s-1, implying a slow and steady process. The frequency factor (ln A) for the desulfurization reaction in different systems was in the range of 10.8−11.0 s-1, which is in support of predicting an associated type of reaction that envisages the formation of an activated complex. The Arrhenius activation energy of the sulfur loss reaction in different systems has been observed to be in the range of 10.9−23.0 kJ/mol. A semiquantitative thermodynamic approach of transition-state theory revealed that the desulfurization reaction is nonspontaneous in nature and proceeded with the absorption of heat, accompanied by the reduction in the degree of disorder in the systems, irrespective of the leaching time and temperature.

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Biodesulphurization of coal: behaviour of trace elements

Cited by 10 publications

References 8 publications

Arsenic in Coal: Modes of Occurrence, Distribution in Different Fractions, and Partitioning Behavior during Coal Separation—A Case Study

Arsenic in Coal: Modes of Occurrence, Distribution in Different Fractions, and Partitioning Behavior during Coal Separation—A Case Study

Desulfurization of Organic Sulfur from a Subbituminous Coal by Electron-Transfer Process with K₄[Fe(CN)₆]

Electron-Transfer-Induced Desulfurization of Organic Sulfur from Sub-bituminous Coal

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Biodesulphurization of coal: behaviour of trace elements

Cited by 10 publications

References 8 publications

Arsenic in Coal: Modes of Occurrence, Distribution in Different Fractions, and Partitioning Behavior during Coal Separation—A Case Study

Arsenic in Coal: Modes of Occurrence, Distribution in Different Fractions, and Partitioning Behavior during Coal Separation—A Case Study

Desulfurization of Organic Sulfur from a Subbituminous Coal by Electron-Transfer Process with K4[Fe(CN)6]

Electron-Transfer-Induced Desulfurization of Organic Sulfur from Sub-bituminous Coal

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Desulfurization of Organic Sulfur from a Subbituminous Coal by Electron-Transfer Process with K₄[Fe(CN)₆]