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Plasma facts

What is plasma?

The GasPlas technology exploits the remarkable properties of plasma – ionised gases where the atoms have been stripped of the electrons that bond them together. By using microwaves to ionise a natural gas such as methane, it becomes possible to efficiently separate its constituent hydrogen and carbon atoms.

The particles of a plasma are charged and therefore strongly influenced by electromagnetic fields. However, the overall charge of a plasma always remains zero. There are different classifications of plasma, largely dependent upon the degree of ionisation and the distribution of energy between the ions.

  • A thermal plasma is one which has an even distribution of thermal energy between the positively (atoms) and negatively (electrons) charged ions.
  • A non-equilibrium plasma is one which has an uneven distribution of thermal energy between the atoms and electrons.
  • A cold plasma is one which has only a small percentage of the gas molecules ionised and are highly non-equilibrium. The high degree of equilibrium means that electron temperatures are still very high, but the atom temperatures low.
  • Microwave plasmas are non-equilibrium plasmas. This is due to the way that microwaves interact with gas molecules to de-ionise them. However, the level of non-equilibrium that can exist is a scale and can be varied through control of parameters such as gas pressure.
  • The afterglow is the region after the plasma where the electromagnetic field that sustains the plasma glow are absent or insufficient to maintain the discharge. In the afterglow, plasma-generated species de-excite and participate in secondary chemical reactions that tend to form stable species.

The GasPlas plasma nozzle has several notable characteristics. It operates at atmospheric pressure to enable it to process industrial quantities of gas. The result of “high pressure” operation is that the degree of non-equilibrium is shifted away from the extreme end of the scale where low atom temperatures can be expected. However, the energy distribution within our plasma is still considerably different from thermal plasma and still affords all of the benefits associated with highly non-equilibrium plasmas without the reduction in throughput due to low pressure operation.

Moreover, it does not suffer from electrode erosion that is common for many types of thermal plasma source. This is important for synthetic applications which cannot tolerate contamination of the gas stream. It also reduces the operating costs which are associated with the high levels of maintenance costs attributed to part replacement due to erosion. The GasPlas nozzle also offers improved energy efficiency when compared to like-for-like applications over thermal plasma systems due to the use of microwave generators as a power source. The microwave energy couples directly to the electrons that make up the bonds between atoms. This means that most of the energy is directed at ionisation.


GasPlas Newsflash

Presentation at University of East Anglia

8 June 2011

Invited by professor David J Richardson, Dean of Science at the Faculty of Science, Per Espen Stoknes and inventor Phil Risby gave a presentation before a full audience of UEA senior researchers, staff and students.

Download presentation (PDF)