4. Conclusion

Plasma torches, whether arc, DC or radio-frequency (RF), are now a well-established technology, even if they are still evolving. Indeed, whatever the process used, it's the torch that needs to be adapted to the process, not the other way round. Generally speaking, torches with non-consumable electrodes, whether blown or transferred arc, are limited in power: currently 400 kW for RF torches, 7 to 8 MW for torches with or without transferred arc. This means that, for operations requiring power levels in excess of a few megawatts, we have moved towards the use of direct-current arcs with solid or hollow graphite electrodes, because with the latter, by injecting a gas into the center, we have good control over the plasma formed.

Choosing the right torch for the process depends on the enthalpy required, the plasma gases needed (heat transfer and chemistry issues) and...