Chemistry Reference
In-Depth Information
Discussing the two limiting situations of low or high power input into the AZ
P
. The set of chemical
rate equations results in two final compositions, which are qualified as [1,2]:
→
0 and
P
→∞
, which includes the limits
n
e
→
0 and
n
e
→∞
1. CEEC, Chemical equilibrium of electronic catalysis. The occurrence of a
finite degree of conversion in a closed plasma chemical system at the limit of
vanishing ionization is a very typical case, representing a kind of electronic
catalysis: In principle already one hot electron (permanent regenerated)
is able to convert a reactant mixture in this equilibrium state of altered
composition.
2. CECD, Chemical equilibrium of complete decomposition. Large concen-
trations of hot electrons (high power input) result in the nearly complete
decomposition of the reactants in the active zone (phase). The after-
glow recombination processes yield a final composition of the reactant
mixture according to the neutral gas reactions starting from the elemen-
tary constituents. Obviously this behavior must be a general characteristic
equilibrium state of every nonisothermal plasma chemical reactor, too.
An important point regarding the experimental verification of the quasi-equilibrium
states is the following one: Although these states are defined as limiting cases (
P
→
0
or
P
→∞
) in practice they can be observed already at moderate values of
P
.
4.3.2 D
EFINITION AND
K
INETIC
B
ACKGROUND
The reaction system is characterized by the type of reversible gross reaction:
A
+
B
+
e
C
+
e
(4.6)
(
e
symbolizes the hot electron) and some plasma parameters like the kinetic
temperature of electrons
T
e
and gas temperature
T
g
. Under a plasma chemical quasi-
equilibrium, we understand a stationary state of the composition of stable reaction
products:
•
Attainable from both sides of a reversible gross reaction (mentioned earlier)
•
Independent of reactor parameters, as power input (degree of ionization),
geometry, and type of the plasma zone as well as reactor dead zone
•
Described by a modified mass action law whose constant differs from the
usual one, but depends like the usual one on the gas temperature (the most
important point). It is determined by a multitude of elementary processes of
the reactor and is kinetic by nature.
Inthecaseofthechemicalequilibriumofthermalreactions(CETR)fortheconversion
k
+
A
+
B
C
k
−
