Reactivity of Coal and Char. 1. In Carbon Dioxide Atmosphere

Dutta, S.; Wen, Cheng; Belt, R.J.

doi:10.1021/i260061a004

Cited by 310 publications

(176 citation statements)

References 14 publications

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“…In addition previous studies have shown that the reaction rates on coal chars are significantly greater than on graphite surfaces. 14) Despite the significant differences in carbon reactivity (see Table 1) the overall rates of reduction of the slags by the various chars are similar within experimental uncertainty (Fig. 3).…”

Section: Char/slag Reactionmentioning

confidence: 81%

Kinetics of Reduction of FeO from Slag by Graphite and Coal Chars

Teasdale

Hayes

2005

ISIJ Int.

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The rates of reduction of FeO from iron-saturated FeO-CaO-Al 2 O 3 -SiO 2 slags by graphite, coke, bituminous coal and anthracitic coal chars at temperatures in the range 1 673-1 873 K have been measured using a sessile drop technique. The extents of reaction were determined using EPMA analysis of quenched samples, and on line gas analysis using a quadrupole mass spectrometer. The reaction rates have been shown to be dependent critically on carbon type. For the reaction geometry used in this investigation the reduction rates of graphite and coke are observed to be faster than with coal chars. This unexpected finding is shown to be associated with differences in the dominant chemical and mass transfer mechanisms occurring at the reaction interface. High reaction rates are observed to occur with the formation of liquid Fe-C alloy product and the associated gasification of carbon from the alloy. The rates of reduction by coal chars are determined principally by the chemical reaction at the carbon/gas interface and slag phase mass transfer.KEY WORDS: slag; reduction; carbon; char; kinetics.tion tube, and this stand could be moved from the base of the reaction tube into the hot zone. The hot zone length is approximately 80 mm, over which the temperature varies by Ϯ2 K.The extents of reaction in the slag samples were measured by two methods, i) electron probe X-ray microanalysis (EPMA) of quenched slag samples, and ii) on line quadrupole mass spectrometer measurements (QMS) of the resulting gas composition and mass flows. 2) EPMAThe quenched slag samples were mounted and polished cross sections were examined using scanning electron microscope (SEM) and electron probe X-ray microanalysis (EPMA) with wavelength dispersive spectrometers. The quenched silicate slags formed glass on cooling from the furnace to room temperature enabling the iron oxide concentrations within the slag phase to be accurately measured at various positions within the cross section. The mean FeO concentrations reported in this study are obtained from measurements across the whole section of the sample. Figure 1 shows the sample geometry, and a schematic of the furnace-quadrupole mass spectrometer (QMS) facility is shown in Fig. 2. A gas mass flow controller is used to introduce ultra high purity argon gas (99.999 %) at a known rate into the reaction tube. The argon inlet tube is positioned close to and above the sample to provide a continuous gas flow across the surface of the slag sample. A gas sampling capillary is positioned at the mouth of the crucible; this enables the reaction gases to be extracted from the reaction site for analysis by the mass spectrometer. The gas flow, the configurations and dimensions of the various tubes were selected so as to ensure laminar plug flow of the product gases into the sampling capillary and to provide a fast, reproducible response to changes in gas composition. This was confirmed by injecting tracer gas "spikes" in the gas lines. The resulting peaks that were detected by the mass spectrometer decayed over ...

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Section: Char/slag Reactionmentioning

confidence: 81%

Kinetics of Reduction of FeO from Slag by Graphite and Coal Chars

Teasdale

Hayes

2005

ISIJ Int.

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“…The proper design of combustion facilities demands that the kinetics of combustion be understood. Much combustion literature suggests that char reactivities should be expressed on a surface area basis [2], although small char micropores might not be fully utilized during oxidation or gasification [e.g., [3][4][5][6][7][8]. Many models have been proposed to describe development of char surface areas with burn-off [9][10][11][12][13][14][15], but many features need further clarification -e.g., different patterns of porosity development are observed in the same char, in different gases, even when rates of reaction are set to be identical [7,16].…”

Section: Introductionmentioning

confidence: 99%

Study of Activation of Coal Char

Suuberg¹,

Kulaots²,

Aarna³

et al. 2003

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“…K r,e is evaluated for the conditions in the emulsion, where the reaction takes place. The rate of reaction can also be formulated as [20,21]:…”

Section: Problem Description and Definitionsmentioning

confidence: 99%

“…Some authors have used expressions like Eq. (4) to estimate the role of internal diffusion [20,21]. η p (x c ) is defined as the ratio of the actual conversion rate of a particle to the rate free of diffusion effects (FDE):…”

Section: Problem Description and Definitionsmentioning

confidence: 99%

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Gas–solid conversion in fluidised bed reactors

Gómez–Barea

Leckner

Santana

et al. 2008

Chemical Engineering Journal

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A simplified model for gas-solid reactions in fluidised bed (FB) is proposed. Such models already exist for catalytic gas-solid reactions (CGSRs), providing general description of the system in terms of main governing parameters. Expansion of this approach to non-catalytic gas-solid reactions (NCGSRs) is difficult, because the solid reactant takes part in the reaction. Therefore, FB reactor models for NCGSR are usually devised only for specific cases, and a general analysis has not been presented up to date. The present model allows analysis of different types of NCGSR in a generalised way, handling catalytic reactions as a particular, simpler, case. It is shown that the reactor behaviour can be described by three governing dimensionless parameters. Two additional parameters, quantifying the importance of diffusion effects in single particles are also identified, and their impact on reactor behaviour is analysed. Possible simplifications are explored. Model limitations, that is, assumption of isothermal bed and particle and the occurrence of only one reaction, are discussed. Examples are outlined to show the applicability of the method.

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Reactivity of Coal and Char. 1. In Carbon Dioxide Atmosphere

Cited by 310 publications

References 14 publications

Kinetics of Reduction of FeO from Slag by Graphite and Coal Chars

Kinetics of Reduction of FeO from Slag by Graphite and Coal Chars

Study of Activation of Coal Char

Gas–solid conversion in fluidised bed reactors

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