**3. Description of the plasma furnace**

The schematic diagram of 30 kW DC extended arc plasma reactor used for this study is shown in **Figure 4** [13].

On top of the reactor, the plasma torch is attached in the downward direction. The plasma torch contains a hollow cylindrical graphite crucible with 145 mm outer diameter, wall thickness 15 mm, and 300 mm high that serves as the anode. A hollow graphite rod of 400 mm long and 5 mm inner and 35 mm outer diameter serves as the cathode. The graphite rod end is tapered to a conical shape for superior

**99**

chamber.

**Figure 4.**

*Plasma Processing of Iron Ore*

*DOI: http://dx.doi.org/10.5772/intechopen.94050*

*Schematic diagram of DC extended arc plasma reactor.*

electron emission. The hollow structure of the cathode has been designed to have provisions for gas flow. The material to be processed was placed in the anode crucible bed, and the arc was initiated by shorting the cathode and the crucible bottom wall (graphite plate). The arc length was increased by raising the cathode rod up suitably within the crucible to heat the charge placed in the crucible. The power supply and power control unit is designed to vary the necessary voltage and current, enabling easy and smooth control of experimental conditions. Voltage and current can be altered over a range of 0–100 V and 0–500 A, respectively. The gas supply unit facilitates plasma forming gases, i.e., oxygen, argon, nitrogen, methane, coke oven gas. Besides, the mixture of above gases can be utilized as plasma forming gas. Gas flow control consisting of digital indicators helps in not only measuring gas flow rate but also governing a suitable flow of gases as per experiment performed and stands as a key parameter. The gas flow rate can be varied from 0 to 15 LPM. Heat insulating materials are placed in between the steel casting and reaction

Several prerequisite steps have to be done before feeding samples into the reaction chamber. Initially, the crucible was cleaned in order to avoid any other material contained in the crucible to be reacted with samples. The hollow tapered graphite rod was fitted in such a way that it points towards the center of the reaction chamber. After checking no leakage in the crucible, it was placed in the space provided in steel casting. Bubble alumina was poured in spacing between the reaction chamber and reaction chamber that acts as a heat-insulating medium. The power supply was then provided, and proper arcing between cathode and anode was tested. The gas supply is then connected to the cathode passage, and plasma forming gas was purged into the reaction chamber for 1 minute to displace atmospheric air. After that, the power supply and plasma forming gas supply both supplied simultaneously, and the required voltage and current maintained. Then sample feed was poured into the hot reaction chamber as per our requirement.

The present study demonstrates the plasma processing of three iron-bearing

minerals viz. blue dust, siliceous type iron ore, and manganiferous iron ore.

**4. Plasma processing of iron-bearing minerals**

*Iron Ores*

*Long-range of melting materials*

*Independent energy* 

*Gas environment control*

*Electrical energyintensive process*

*High energy transfer to slag layer*

*Purity level in product*

**Table 1.**

*source*

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iii.Type of process (melting, smelting or smelting reduction)

*High efficiency* Since a huge amount of energy in the form of heat is available by utilization of plasma, high throughput can be achieved.

*Feed capability* This process is independent of the size, shape, and composition of feed material. *Transient process* Due to the release of huge heat energy that a particular reaction requires at a specific

*High energy fluxes* Higher temperatures with extreme jet velocities and greater thermal conductivities

*Gas flow control* Unlike combustion systems, the gas flow rate, temperature, and energy input are

a shorter period.

using plasma.

be made.

rate.

irrespective of energy input.

temperature into account.

Since high temperature can be achieved in a reaction by using plasma, almost all materials can be melted in this process. Although its commercial use to melt and process metals is well known, the method is less known as a method of melting glass.

temperature, plasma stands ahead of any other process to respond to the changes in

of plasma gases are the key factors that result in high energy fluxes. Smaller furnace dimensions with high smelting capacity are a unique aspect of using plasma.

The flexibility of control over feed rate and power independently and input power is not limited by the electrical conductivity of feed material to be melted or smelted. Hence greater freedom of choice with respect to charge composition is available by

not interdependent, and gas flow rate and temperature can be controlled separately

Energy can be provided to the system with desired oxygen potential to ensure oxidizing, reducing, or inert gas conditions independently without taking

Minimization of the usage of fossil fuel energy and conservation of fossil fuel can

Plasma jet is directed towards slag layer and significantly increases the metallization

The purity level of the final product through plasma processing is very high.

The schematic diagram of 30 kW DC extended arc plasma reactor used for this

On top of the reactor, the plasma torch is attached in the downward direction. The plasma torch contains a hollow cylindrical graphite crucible with 145 mm outer diameter, wall thickness 15 mm, and 300 mm high that serves as the anode. A hollow graphite rod of 400 mm long and 5 mm inner and 35 mm outer diameter serves as the cathode. The graphite rod end is tapered to a conical shape for superior

v.Process environment (open-air, inert or vacuum)

iv.Process duration

*Advantageous aspects of thermal plasma.*

vi.Feed rate

vii.Power control

**3. Description of the plasma furnace**

study is shown in **Figure 4** [13].

**Figure 4.** *Schematic diagram of DC extended arc plasma reactor.*

electron emission. The hollow structure of the cathode has been designed to have provisions for gas flow. The material to be processed was placed in the anode crucible bed, and the arc was initiated by shorting the cathode and the crucible bottom wall (graphite plate). The arc length was increased by raising the cathode rod up suitably within the crucible to heat the charge placed in the crucible. The power supply and power control unit is designed to vary the necessary voltage and current, enabling easy and smooth control of experimental conditions. Voltage and current can be altered over a range of 0–100 V and 0–500 A, respectively. The gas supply unit facilitates plasma forming gases, i.e., oxygen, argon, nitrogen, methane, coke oven gas. Besides, the mixture of above gases can be utilized as plasma forming gas. Gas flow control consisting of digital indicators helps in not only measuring gas flow rate but also governing a suitable flow of gases as per experiment performed and stands as a key parameter. The gas flow rate can be varied from 0 to 15 LPM. Heat insulating materials are placed in between the steel casting and reaction chamber.

Several prerequisite steps have to be done before feeding samples into the reaction chamber. Initially, the crucible was cleaned in order to avoid any other material contained in the crucible to be reacted with samples. The hollow tapered graphite rod was fitted in such a way that it points towards the center of the reaction chamber. After checking no leakage in the crucible, it was placed in the space provided in steel casting. Bubble alumina was poured in spacing between the reaction chamber and reaction chamber that acts as a heat-insulating medium. The power supply was then provided, and proper arcing between cathode and anode was tested. The gas supply is then connected to the cathode passage, and plasma forming gas was purged into the reaction chamber for 1 minute to displace atmospheric air. After that, the power supply and plasma forming gas supply both supplied simultaneously, and the required voltage and current maintained. Then sample feed was poured into the hot reaction chamber as per our requirement.
