Thermal Plasma

The plasma, sometimes referred to as the fourth state of matter, is an ionized gas comprised by molecules, atoms, ions, electrons and photons. Due to the free charge carriers present in a plasma, as opposed to ordinary gases, the plasma presents high electrical conductivity and, therefore, is capable to conduct electrical current.

In general, plasmas can be classified into two different types: the thermal plasma (“hot” plasma) and non-equilibrium plasmas (“cold” or low pressure plasmas).

The plasma technology has a long development history and, along the years, has became itself a valuable tool to produce high temperature gases. A chief characteristic of plasma is its total independence on chemical reactions to produce heat, as for instance it occurs in combustion. Besides the capability to produce very high temperatures, the operating principle of plasma allows the free choice of the working atmosphere according to process needs, conveniently adapting to operating demands for inert, reducing, or oxidizing atmospheres.

Thermal plasma are most commonly obtained by passing an electrical current through the gas (electrical discharge). Plasma generating systems include the following items of equipment:

• plasma torch;
• arc ignitor;
• power supply to feed the plasma torch, generally with continuous current;
• dionized cooling water system intended for cooling of torch parts;
• control unit; and
• gas feeding system.

The equipment needed for plasma generation can be either adapted on existing furnaces and reactors, or applied in dedicated furnaces and reactors design, optimized for the use of plasma in specific industrial application.