**2.3 Generation of plasma**

Thermal arc plasmas are generated by striking an electric arc between two or more electrodes. They are characterized by high current densities (greater than 100 A/cm2 ) and are more luminous than other types of discharges, especially when operated at atmospheric pressure and above. Thermal arcs can be initiated in several ways. Two common methods are electrode contact, which produces a short circuit, or pre-ionization of the gap between electrodes by a high-frequency spark. The cathode must be heated beyond 3500 °K, at which point the thermionic emission of electrons begins, generating the charge carriers that create the plasma state [3]. Cold cathodes are cylindrical and made of heavily cooled copper, iron, or copper alloy while high-temperature cathodes are usually rod-shaped and made of thorium, tungsten, or graphite. Thermal arc plasma torches can operate in two modes, i.e., non-transferred and transferred arc. If the plasma torch having two electrodes designed in such a way that hot gas emerges through one electrode and then heated by the flame is called non-transferred. If there is only one electrode in the torch and

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comprises;

burning)

*Plasma Processing of Iron Ore*

are shown in **Figure 3**.

**Figure 3.**

**2.4 Application of plasma**

surface modification, and surface coating.

troubleshooting and also processing costs.

**2.6 Application in iron making**

**2.5 Advantages of plasma over conventional processes**

*Schematic diagram of transferred and non-transferred plasma torches.*

plasma, some of the important features are given in **Table 1**.

i.Type of reducing agent (carboneous or any other)

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

material to be heated/melted acts as another electrode, then it is said to be transferred. The schematic of both transferred and non-transferred arc plasma torches

In the last two decades, plasma has claimed to be an emerging solution to numerous processes due to its unique features and hence implemented in various sectors [4, 6–10]. Plasma finds significant industrial applications viz. melting, smelting, smelting and reduction, remelting and refining, spark plasma sintering,

Although there are a lot of many advantageous aspects behind the utilization of

Many researchers investigated the applicability of plasma in iron and steel making [9, 11, 12]. In general, plasma is used as a heat source instead of reductant itself, as the percentage of the degree of reduction lags behind when utilized as a reductant. The selection of the type of plasma and preferred operating parameters, along with the type of reductant, is a crucial factor that needs to be considered sensibly in relation to the treating of material. The wrong choice can affect both

Criteria for selection must be based on answering many questions, which

ii.Type of plasma forming gas (inert, self-reducing, self-burning or helps in

*Plasma Processing of Iron Ore DOI: http://dx.doi.org/10.5772/intechopen.94050*

#### **Figure 3.**

*Iron Ores*

**Figure 2.**

3500°K, where molecules begin to dissociate, while the lower limit of plasma temperatures is about 10,000°K. As most laboratory plasmas are heated electrically, their temperatures will lie in the bottom end of the ionization curve, i.e., above 10,000°K for diatomic gases. For any process operating below 1000°K, an air-fuel flame (~2000°K) or an oxygen-fuel flame (~3000°K) will have a high percentage of energy available for the process. However, for the reaction occurring at 2500°K, only one-sixth of energy contained in an oxygen flame will be available, and rest must be either wasted or recovered in the expensive heat exchangers. On the other hand, a plasma flame composed of atomic nitrogen at 10,000°K would have more than 90% of its energy available above 2500°K. This high energy efficiency may more than offset the economic advantage that combustion energy over electrical energy; certainly, this advantage will increase as electrical energy becomes cheaper while fossil energy gets more expensive. Although by utilizing plasma high temperature can be achieved with the liberation of huge heat energy in a chemical reaction, plasma gases are generally not

Thermal arc plasmas are generated by striking an electric arc between two or more electrodes. They are characterized by high current densities (greater than

operated at atmospheric pressure and above. Thermal arcs can be initiated in several ways. Two common methods are electrode contact, which produces a short circuit, or pre-ionization of the gap between electrodes by a high-frequency spark. The cathode must be heated beyond 3500 °K, at which point the thermionic emission of electrons begins, generating the charge carriers that create the plasma state [3]. Cold cathodes are cylindrical and made of heavily cooled copper, iron, or copper alloy while high-temperature cathodes are usually rod-shaped and made of thorium, tungsten, or graphite. Thermal arc plasma torches can operate in two modes, i.e., non-transferred and transferred arc. If the plasma torch having two electrodes designed in such a way that hot gas emerges through one electrode and then heated by the flame is called non-transferred. If there is only one electrode in the torch and

) and are more luminous than other types of discharges, especially when

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used as reactants in the reaction.

*Temperature and energy relationship of various plasma gases.*

**2.3 Generation of plasma**

100 A/cm2

*Schematic diagram of transferred and non-transferred plasma torches.*

material to be heated/melted acts as another electrode, then it is said to be transferred. The schematic of both transferred and non-transferred arc plasma torches are shown in **Figure 3**.
