Reduction of Oxide Minerals by Hydrogen Plasma: An Overview

Sabat, Kali Charan; Rajput, Priyanka; Paramguru, R. K.; Bhoi, Bhagyadhar; Mishra, B.K.

doi:10.1007/s11090-013-9484-2

Cited by 128 publications

(83 citation statements)

References 33 publications

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“…In the reduction of TiO2, oxygen plasma was detected by spectroscopy during microwave irradiation at 900 W for 10 min at the maximum intensity of the microwave electric field in a 10 −1 Pa vacuum, and the weak reduction of TiO2 was confirmed [13]. Other papers have reported the reduction of various transition-metal oxides by plasma [14][15][16]. Sabat et al [15] mentioned that, typically, the activation energy of plasma-assisted reactions is lower than that of the corresponding standalone reactions.…”

Section: Introductionmentioning

confidence: 91%

“…Other papers have reported the reduction of various transition-metal oxides by plasma [14][15][16]. Sabat et al [15] mentioned that, typically, the activation energy of plasma-assisted reactions is lower than that of the corresponding standalone reactions. Moreover, the reduction of copper oxide (CuO) occurred during microwave irradiation, and the reduction behavior was different between irradiation by the microwave electric field and the magnetic field [17].…”

Section: Introductionmentioning

confidence: 99%

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In Situ Spectroscopic Analysis of the Carbothermal Reduction Process of Iron Oxides during Microwave Irradiation

Fukushima

Takizawa

2018

Metals

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Abstract:The effects of microwave plasma induction and reduction on the promotion of the carbothermal reduction of iron oxides (α-Fe 2 O 3 , γ-Fe 2 O 3 , and Fe 3 O 4 ) are investigated using in situ emission spectroscopy measurements during 2.45 GHz microwave processing, and the plasma discharge (such as CN and N 2 ) is measured during microwave E-field irradiation. It is shown that CN gas or excited CN molecules contribute to the iron oxide reduction reactions, as well as to the thermal reduction. On the other hand, no plasma is generated during microwave H-field irradiation, resulting in thermal reduction. Magnetite strongly interacts with the microwave H-field, and the reduction reaction is clearly promoted by microwave H-field irradiation, as well as thermal reduction reaction.

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Section: Introductionmentioning

confidence: 91%

Section: Introductionmentioning

confidence: 99%

In Situ Spectroscopic Analysis of the Carbothermal Reduction Process of Iron Oxides during Microwave Irradiation

Fukushima

Takizawa

2018

Metals

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“…Further, it is argued based on thermodynamic data that the equilibrium partial pressure of atomic hydrogen needed to reduce these oxides decreases with a decrease in temperature unlike that for the reduction with molecular hydrogen. Activated species present in hydrogen plasma are also known to remove kinetic barriers during the reaction [13]. The underlying question, whether hydrogen plasma having atomic H or other active hydrogen species can reduce the induction period in the CuO reduction, remains unresolved.…”

Section: Introductionmentioning

confidence: 99%

“…It is mathematically written as DG°= -RTlnK. Considering K = pH 2 O/pH 2 in the case of hydrogen reduction and putting this value in the DG°expression and after simplifying, the Bauer-Glaessner [B-G] equilibrium diagram can be worked out [12,13]. The diagram shows the equilibrium relationship between the partial pressure of molecular hydrogen or atomic hydrogen, and the temperature for a given reaction.…”

Section: Introductionmentioning

confidence: 99%

Reduction of Copper Oxide by Low-Temperature Hydrogen Plasma

Sabat

Paramguru

Mishra

2016

Plasma Chem Plasma Process

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The paper presents experimental results of reduction of cupric oxide (CuO) by low-temperature hydrogen plasma in a microwave-assisted plasma set-up. The experiments were carried out at low microwave powers in the range of 600-750 W and low hydrogen flow rates in the range of 0.833 9 10 -6 to 2.5 9 10 -6 m 3 s -1 . In all the experiments for reduction of CuO with hydrogen plasma, an initial induction period was observed in the kinetic plots. The induction period decreases with increase in pressure or temperature. The induction period leads to the formation of active sites for adsorption of H 2 . After the induction period, fast autocatalytic reduction takes place followed by a sluggish period towards the end. The reduction process proceeds in sequential steps through the formation of sub-oxides. The kinetic data fits the Avrami-Erofeev equation with 'n' value close to 3. The resultant activation energy measured during hydrogen plasma processing is around 75.64 kJ mol -1 . This is lower compared to activation energies measured by other methods of reduction indicating a clear advantage.

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“…The primary motivation for reduction of oxides in hydrogen plasma is the environmental constraints faced by global metal industries to reduce CO 2 emission, limitations of future supply of carbon as reductant, and exploitation of the favourable thermodynamic and kinetic condition for reduction of metal oxides by low temperature hydrogen plasma. An excellent review of reduction of oxide minerals in hydrogen plasma can be found in literature [1]. The hydrogen plasma is exploited in two ways for reduction purpose: low temperature or cold plasma and thermal plasma.…”

Section: Introductionmentioning

confidence: 99%

Monitoring Hydrogen Plasma Reduction of Oxides by Na D Lines

Das

Rajput

et al. 2016

Plasma Chem Plasma Process

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Out of many applications of hydrogen plasma, reduction of metal oxides is an important one. The reduction can be carried out using carbon or hydrogen. While carrying out the reduction of hematite (Fe 2 O 3 ) in hydrogen plasma, an attempt was made to characterize the hydrogen plasma by optical emission spectroscopy. The spectroscopic results provide some new and useful information. In addition to the hydrogen emission lines, two prominent lines at 589 and 589.6 nm were observed. These two lines are confirmed to be sodium D1 and D2 (Na D lines) by comparing with a low pressure sodium vapour lamp (LPSVL). The source of the trace amount of sodium is also confirmed to be from the metal oxide sample as an impurity. These lines are found to be very sensitive to various process parameters such as gas flow rate, microwave power, and reduction chamber pressure. The temporal variation of these two Na D lines also shows a characteristic trend during metal oxide reduction in hydrogen plasma. The weight loss and the X-ray diffraction analyses of reduced Fe 2 O 3 sample for different time duration provides the evidence of correlation with Na D lines' intensity trend. This trend can be used to monitor the state and completion of hydrogen plasma based reduction reaction. In processes where Na is not associated with metal oxide, trace amount of Na in its molecular form such as NaOH can be introduced for monitoring the plasma process parameters as well as the plasma based reduction process.

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Reduction of Oxide Minerals by Hydrogen Plasma: An Overview

Cited by 128 publications

References 33 publications

In Situ Spectroscopic Analysis of the Carbothermal Reduction Process of Iron Oxides during Microwave Irradiation

In Situ Spectroscopic Analysis of the Carbothermal Reduction Process of Iron Oxides during Microwave Irradiation

Reduction of Copper Oxide by Low-Temperature Hydrogen Plasma

Monitoring Hydrogen Plasma Reduction of Oxides by Na D Lines

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