Chemistry Reference
In-Depth Information
Radiation
photons
Beams
electrons
protons
…
Thermal energy
gas heating
compression
Plasma
Chemical processes
Heating of electrons
Electrical
gas discharges
Electric current in gas
Breakdown
Electric fields
FIGURE 1.1
Principles of plasma generation.
Important historical milestones in the investigation and application of plasma
chemical reactions are as follows:
•
The synthesis of H
2
O in spark discharges operating in H
2
/O
2
mixtures
(H. Cavendish 1781)
•
The fixation of air nitrogen in spark discharges forming NO
(H. Cavendish 1784, J. Priestley 1785)
•
The discovery and application of the ozonizer
(W. v. Siemens 1857)
•
The conversion of organic compounds in silent discharges
(M. Berthelot 1866)
•
The industrial production of nitrogen oxides in the arc discharge
(Birkeland-Eyde process 1905)
•
The industrial production of acetylene in plasmatrons
(Hüls process 1940)
1.3 THERMAL AND NONTHERMAL PLASMA CHEMISTRY
We have to distinguish two kinds of plasma chemical conversions, the thermal as
well as the nonthermal plasma chemistry. In the case of
thermalplasmachemistry
the
plasmas act primarily as generators of thermal energy. They operate typically in the
kW to MW power range. At high temperatures (range 10
3
-10
4
K) and high specific
enthalpies, the chemical compounds are decomposed. This process is called plasma
pyrolysis. The chemical reactions take place in/or nearby the thermal equilibrium,
characterized by the common temperature (the gas temperature) of all species. The
output of reaction products has to be optimized by a quenching procedure and their
separation from the gas mixture.
