Kinetics and Reduction Characteristics of Hematite-noncoking Coal Mixed Pellets under Nitrogen Gas Atmosphere.

Dey, Sajal Kumar; Jana, Biswanath; Basumallick, A.

doi:10.2355/isijinternational.33.735

Cited by 39 publications

(29 citation statements)

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“…It was widely assumed that the metal oxides reduction by carbon should be negligible at temperatures lower than 1000 ºC [367][368][369]. However, Siriwardane et al [227,370] showed the direct reduction Even though N 2 was used as fluidizing gas, eventually the char conversion through CO 2 gasification can be the relevant reacting mechanism.…”

Section: Reaction Schemementioning

confidence: 99%

Progress in Chemical-Looping Combustion and Reforming technologies

Adánez

Abad

Garcı́a-Labiano

et al. 2012

Progress in Energy and Combustion Science

1,997

1,614

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This work is a comprehensive review of the Chemical-Looping Combustion (CLC) and Chemical-Looping Reforming (CLR) processes reporting the main advances in these technologies up to 2010. These processes are based on the transfer of the oxygen from air to the fuel by means of a solid oxygen-carrier avoiding direct contact between fuel and air for different final purposes. CLC has arisen during last years as a very promising combustion technology for power plants and industrial applications with inherent CO 2 capture which avoids the energetic penalty present in other competing technologies.CLR uses the chemical looping cycles for H 2 production with additional advantages if CO 2 capture is also considered.The review compiles the main milestones reached during last years in the development of these technologies regarding the use of gaseous or solid fuels, the oxygen-carrier development, the continuous operation experience, and modelling at several scales. Up to 2010, more than 700 different materials based on Ni, Cu, Fe, Mn, Co, as well as other mixed oxides and low cost materials, have been compiled. Especial emphasis has been done in those oxygen-carriers tested under continuous operation in Chemical-Looping 2 prototypes. The total time of operational experience (≈ 3500 h) in different CLC units in the size range 0.3-120 kW th , has allowed to demonstrate the technology and to gain in maturity. To help in the design, optimization, and scale-up of the CLC process, modelling work is also reviewed. Different levels of modelling have been accomplished, including fundamentals of the gas-solid reactions in the oxygen-carriers, modelling of the air-and fuel-reactors, and integration of the CLC systems in the power plant. Considering the great advances reached up to date in a very short period of time, it can be said that CLC and CLR are very promising technologies within the framework of the CO 2 capture options.

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Section: Reaction Schemementioning

confidence: 99%

Progress in Chemical-Looping Combustion and Reforming technologies

Adánez

Abad

Garcı́a-Labiano

et al. 2012

Progress in Energy and Combustion Science

1,997

1,614

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“…[1][2][3][4][5] Iron oxide fines are generated at every stage of iron oxide processing, leading to either a loss of the iron resource or the burden of higher utilisation costs. Being able to utilise, economically, such iron oxide fines has the potential to provide significant benefits to the iron industry.…”

Section: Introductionmentioning

confidence: 99%

“…[1][2][3][4][5] The degree of control the Boudouard reaction displays, as reported by different researchers, however, is seen to vary. There is agreement in literature that the overall self reduction reaction rate is seen to increase with increasing carbon content; increasing carbon surface area; and in the presence of Boudouard reaction catalysing agents (including metallic iron).…”

mentioning

confidence: 99%

Kinetic Model for the Uniform Conversion of Self Reducing Iron Oxide and Carbon Briquettes

Moon¹,

Sahajwalla²

2003

ISIJ International

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A kinetic model has been developed to describe the uniform conversion of a self reducing mixture of iron oxide and carbon. The model takes into account the reaction kinetics of both the iron oxide reduction and carbon oxidation. The model is validated with experimental data. Rate constants are compared with those in the literature.The combination of existing reaction analysis techniques coupled with the model developed has shown that for the experimental conditions used here, the Boudouard reaction controls the self reduction kinetics.KEY WORDS: mathematical modelling; kinetics; uniform conversion model; self-reduction; iron oxide; carbon; reduction; oxidation.Boudouard reaction (Reaction 4) displays a highly controlling influence on the overall carbothermic reduction of iron oxide. [1][2][3][4][5] The degree of control the Boudouard reaction displays, as reported by different researchers, however, is seen to vary. There is agreement in literature that the overall self reduction reaction rate is seen to increase with increasing carbon content; increasing carbon surface area; and in the presence of Boudouard reaction catalysing agents (including metallic iron). These effects are consistent with the Boudouard reaction displaying a significant influence on the overall self reduction reaction.The overall self reduction reaction rate, however, is seen to level off at higher carbon contents 12,13) ; higher temperatures 14,15) ; and is seen to be improved by decreasing the iron ore particle size (with the inference of increased surface area).14) These effects suggest that there is a limitation to the control the Boudouard reaction displays, which is not yet fully understood. Such incomplete understanding (regarding the degree of control the Boudouard reaction displays on the overall self reduction rate) introduces difficulty in being able to kinetically describe the reaction system.Adding to the complexity of unclear controlling reactions is the issue of non-isothermal reactions occurring within a self-reducing pellet or briquette. In the self reducing briquette, the reactants are intimately mixed and the reaction proceeds when a sufficient temperature is achieved by all or part of the mixture. The very nature of the having combined, thermally activated reactants raises difficulties when studying the reaction kinetics.Work has been conducted, examining the possibility of briquettes reacting non-homogenously when the temperature is raised. Several researchers have shown the nonisothermal nature of the self-reducing mixture. [16][17][18][19] Work by Seaton et al. 18) showed the temperature profile through the mixture changed with increasing reaction temperature. They indicated that the mode of reaction changed to a shrinking core style with increasing temperature. Accordingly, the complexity of the physical and chemical system makes the selection of an appropriate reduction model difficult. The self reduction process is made up of complimentary oxidation and reduction reactions. However, investigations have only focuss...

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“…It was observed by many researchers 1,[5][6][7][8] that the reduction of Panzhihua titanomagnetite concentrates (PTC) is slower than that of magnetite due to its special crystal structure of the ore with the existence of titanium, which results in a higher thermodynamic stability of titanomagnetite. 9,10) This implies a longer residence time in RHF than that with the common iron ore.…”

Section: Introductionmentioning

confidence: 99%

Carbothermic Reduction of Titanomagnetite Concentrates with Ferrosilicon Addition

Bai

et al. 2013

ISIJ Int.

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The effect of Fe-Si on the carbothermaic reduction of Panzhihua titanomagnetite concentrates were investigated under argon atmosphere by isothermal experiments at 1 623 K and non-isothermal experiments in the temperature range from room temperature to 1 723 K with a heating rate of 10 K/min, respectively. The morphology of reduced samples obtained by isothermal experiments was checked by scanning electron microscope. The results show that the addition of Fe-Si accelerates the carbothermic reduction rate of PTC. A part of silicon in the Fe-Si substitutes for carbon to participate the reduction of PTC. The addition of Fe-Si facilitates the nucleation and coalescence of metallic iron formed by reduction. A reaction mechanism for the carbothermic reduction of PTC with Fe-Si addition was proposed. The reduction process could be divided into three stages. In the first stage (lower than 1 273 K), the solid phase reactions with carbon and silicon as reductants are dominant. The exdothermic reduction by silicon, to a certain extent, promotes the reduction of PTC. In the second stage (1 273-1 423 K), the rate of reduction by CO is much faster than that of reduction by silicon, resulting in little influence of Fe-Si on the reduction of PTC. In the final stage, the reduction by silicon markedly occurs again, which further facilitates the coalescence of metallic iron and the reduction of PTC.

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Kinetics and Reduction Characteristics of Hematite-noncoking Coal Mixed Pellets under Nitrogen Gas Atmosphere.

Cited by 39 publications

References 0 publications

Progress in Chemical-Looping Combustion and Reforming technologies

Progress in Chemical-Looping Combustion and Reforming technologies

Kinetic Model for the Uniform Conversion of Self Reducing Iron Oxide and Carbon Briquettes

Carbothermic Reduction of Titanomagnetite Concentrates with Ferrosilicon Addition

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